WO2007085254A1 - Medical device with ph dependent drug release - Google Patents

Abstract

The invention provides intravascular devices coated with a first domain comprising an alkali formulation of polyethylenimine diazeniumdiolate . The alkali ensures stabilisation of the polyethylenimine diazeniumdiolate during processing of the medical device, whilst allowing controlled release of nitric oxide upon use. The invention also provides medical devices coated with a first domain of polyethylenimine diazeniumdiolate, and an outer-layer which prevents or hinders the release of polyethylenimine diazeniumdiolate upon use in the body, particularly from the alkali first domain. In a preferred embodiment a balloon is coated with linear poly (ethylenimine) diazeniumdiolate (L-PEI-NONO) embedded in polyurethane (PU) and provided with a top coat of poly acrylic acid and PU.

Description

MEDICAL DEVICE WITH PH DEPENDENT DRUG RELEASE

Technical field

The present invention is concerned with the release of nitric oxide (NO) from a medical device comprising polyethylenimine diazeniumdiolate, particularly an intravascular medical device; the prevention of the premature release of nitric oxide prior to the therapeutic use of the medical device; the optimisation of the release kinetics of nitric oxide from the medical device once in use; and the prevention of the release of polyethylenimine diazeniumdiolate from the surface of the medical device once in use.

Background of the invention

Within the field of intravascular surgery, local release of therapeutic agents near affected treatment sites is often beneficial. Usually, release of the therapeutic agents must be precisely timed with respect to surgical intervention in order to ensure not only drug delivery at the correct point in time but also at the correct site. For example, a drug-coated stent should not release drug until the stent has reached its intended location in a patient's blood vessels. Additionally, it may be desirable that the release rate of drug from a medical device is controllable if a therapeutic agent is to be administered over an extended period of time, e.g. several hours or even days. On the other hand, for some treatments, swift drug release, e.g. within minutes or seconds, is essential to optimise therapeutic efficiency.

Nitric oxide is regarded as a potent mediator for many biological functions, acting as a vasodilator, a neurotransmitter, an inflammatory mediator, an inhibitor of platelet activation, a modulator of endothelial and leukocyte adhesion, and a modulator of macrophages and neutrophils.

However, nitric oxide is highly unstable in physiological conditions, and is rapidly inactivated by oxyhemoglobin within red blood ceils.

Nitric oxide adducts, such as nitroglycerin have been widely used systemically, for example in the treatment of angina. However, systemic application results in an extensive dilution of the adduct as well as potentially harmful side effects at sites remote from the site of therapeutic action.

There has therefore been a concerted effort to develop local administration technologies, which allow the direct application of nitric oxide to the required site in the body, particularly within the vascular system, where nitric oxide can prevent or reduce thrombosis or vasospasm during vascular surgery, or prevent restenosis occurring after coronary angioplasty and stent implantation. Various compounds have been used to deliver NO therapeutically. One possible candidate for NO release is diazeniumdiolates (NONO'ates) which exhibit the ability to release NO upon exposure to H⁺ ions. The use of NONO'ates for the release of nitric oxide for the treatment of tissue that has been injured or is at risk of injury during sepsis or shock has been described in US patent No. 5,814,656 (Saavedra et al. Apparently insoluble polymeric NONO'ates have also been generally described in US patent No. 5,519,020 (Smith et al.). These polymers have been used to deliver NO to specific tissues, and results have shown that controlled release of NO to a specific site have reduced inflammation and accelerated healing, whilst allegedly avaiding the detrimental effects of systemic delivery or release.

The use of NONO'ates as coatings on implantable medical devices is disclosed in US patent No. 5,770,645.

PCT/DK2006/000714, which is hereby incorporated by reference, provides a method and system for measurement of nitric oxide release from nitric oxide adducts. The method allows for the level of nitrite to be taken into account or even eliminated in order to obtain a precise measurement of NO that has been hitherto achievable.

EP 0 752 866 discloses that polymers to which are bound nitric oxide releasing N₂O₂ ^" functional group may be used for the treatment of restenosis and related disorders. It was found that nitric oxide treated polyethylenimine (polyethylenimine diazeniumdiolate) was effective in triggering vaso-relaxation.

WO2005037339, which refers to expandable balloon for use in angioplasty procedures, discloses that expandable stents, used in the treatment of restenosis, may be coated with a pharmaceutical agent, such as nitric oxide (NO) and that such nitric oxide releasing matrixes may also relax or prevent arterial spasm once the medical device is in place.

US 2006/0008529 discloses the use of additive sites to control nitric oxide release from nitric oxide donors contained within polymers.

WO2005/039664 refers to a medical device, such as a guide wire, an embolization device, or a guide shaft for a microcatheter, which comprises an outer surface layer formed by electrospun nanofibers of polymeric linear poly(ethylenimine) diazeniumdiolate, which may be encompassed by an outermost coating layer, e.g. of polyacrylic acids and co-polymers thereof. WO2005/039664 states that it is advantageous to include an acidic agent to the outer surface layer formed by electrospun nanofibers of polymeric linear poly(ethylenimine) diazeniumdiolate.

WO 95/24908 discloses NONOate polymers, including linear polyethylenimine diazeniumdiolate, which are capable of locally releasing nitric oxide to a site at risk of restenosis. WO 95/24908 also discloses that the NONOates are unique among currently known drugs in that they decompose at any given pH by a first-order reaction to provide doses of nitric oxide that can be predicted, quantified, and controlled.

US 6,885,366 which refers to electrospinning of linear polyethylenimine diazeniumdiolate to coat medical devices with nanofibres of LPEI-NONO, discloses that linear poly(ethylenimine) diazeniumdiolate (LPEI-NONO) is a water insoluble polymer.

Summary of the invention

The embodiments of the present invention may be used in conjunction with the inventions disclosed in the following applications, which are hereby incorporated by reference: EP application No. EP06023203 and US provisional application 60/864,879, EP application No. 06023223 and US provisional 60/864,886, EP application No. 06023222 and US provisional application 60/864,893, EP application No. EP06075159 and US provisional application 60/761,359.

Using the nitric oxide analysis methods disclosed in our application PCT/DK2006/000714 we have carried out a detailed study of the chemical performance of polyethylenimine diazeniumdiolate ((L)PEI-NONO) within formulation solutions and embedded in spray coated polymeric matrix.

These studies have raised a previously unidentified problem of instability of (L)PEI-NONO, both in terms of preparation and storage of (L)PEI-NONO prior to use, such as in the coating of intravascular medical devices, and also the (L)PEI-NONO present in or coated onto such medical devices. Critically, the use of the nitric oxide assays disclosed in

PCT/DK2006/000714 has allowed us to measure the real time release of nitric oxide whilst accounting for the presence of nitrite and nitrate, contaminants which can otherwise lead to considerable experimental error, and typically lead to an considerable over-estimation of the NO released from LPEI-NONO.

The solution provided by the present invention is to ensure that the (L)PEI-NONO is kept in an alkaline environment during the formulation and processing of the (L)PEI-NONO and the application of such (alkali) (L)PEI-NONO formulations to medical devices. Through careful analysis of NO release from linear-polyethylenimine diazeniumdiolate, we have also detected NO release from ionic solutions which have been exposed to medical devices, after removal of the medical device. This has led us to the discovery that contrary to previous teachings, linear-polyethylenimine diazeniumdiolate is soluble in ionic aqueous solution, and as such there is a measurable systemic release of LPEI-NONO into the body upon use of medical devices coated with LPEI-NONO. (see Figure 12).

The solubility of LPEI-NONO in physiological fluids presents a previously unrecognized problem relating to its use to coat medical devices, such as intravascular medical devices in that the release of LPEI-NONO from the medical device into the blood stream will result in the systemic release of LPEI-NONO and undesirable release of nitric oxide at sites remote to the site of therapy.

It is also considered that the release of LPEI-NONO into the blood stream is undesirable as it results in the release of a foreign compound into the body.

We have overcome this problem of systemic release by utilisation of an outer-coat layer external to the LPEI-NONO layer which effectively hinders the release of LPEI-NONO upon insertion into body fluid, such as blood.

In addition, we have found that the use of an alkali formulation of LPEI-NONO presents a disadvantage in that the solubility of LPEI-NONO appears to be enhanced, resulting in increased potential for systemic release of the polymer when in use. In order to overcome this, we employ an external coating (outer-layer or outer-coat). In addition, the outer-coat can have a beneficial effect upon the release kinetics of nitric oxide from polyethylenimine diazeniumdiolate coated medical devices.

The release of NO is thereby effectively controlled until the use of the medical device - this greatly extends the shelf-life and reliability of the medical device, and allows for accurate determination of therapeutic release, and thereby control of the desired pharmacological effect.

For example, in one aspect, upon insertion of the medical device into the body there is a controllable initial period, where NO release is relatively low. This prevents premature release of NO, which can cause issues of excessive bleeding from the entry wound due to the anti-thrombosis effect of NO. The properties of the outer-layer, and in some respects the first, second and third domains, as referred to herein, particularly the nature of the hydrophilic support polymer/polymer blend used in said domains, are important in determining (i.e. controlling) the nature of this initial period. Therefore, using the present invention, the release kinetics of NO can be carefully controlled, ensuring an optimal release profile during the surgical procedure. Whilst initial NO release can be limited, the period of release of therapeutic effective amounts can be extended, thereby overcoming problems of NO depletion after prolonged surgical procedures.

In one aspect, the current invention is based upon the surprising discovery that contrary to the knowledge in the prior art, (linear) poly(ethylenimine) diazeniumdiolate (LPEI-NONO) is soluble in ionized aqueous solutions, most critically in physiological fluids such as blood.

The invention provides for a solution in the form of an outer coating which is applied external to the LPEI-NONO layer (LPN layer, also referred to herein as the first domain), which provides steric hinderance to prevent or reduce the release of LPEI-NONO from the surface of the medical device, whilst allowing the diffusion of water into the LPN layer, and the release of nitric oxide from the LPN layer.

The outer layer may be used in conjunction with a polymer coating system, where the nitric oxide adduct is presented in the form of a polymer structure which comprises both a structural polymer, and a hydrophilic polymer, thereby allowing the controlled access of physiological fluids directly to the nitric oxide adduct, depending upon the proportion of the structural polymer, the hydrophilic polymer and the nitric oxide adduct present in the polymer coating system. It is also considered that the polymer coating system can be used to prevent or reduce the unwanted release of nitric oxide adducts from the surface of coated medical devices, whilst allowing controlled diffusion of water and ions to the nitric oxide adduct, and the resulting nitric oxide from the adduct.

The invention provides for a medical device for intravascular use, comprising a base material which either comprises polyethylenimine diazeniumdiolate, or is at least in part coated with an inner coating which comprises polyethylenimine diazeniumdiolate, wherein said medical device further comprises an outer layer, positioned externally to said base material or said inner coating, said outer layer comprising a polymeric barrier between the polyethylenimine diazeniumdioiate and the external environment.

Therefore the outer layer comprises a polymer which controls, reduces or prevents the release of polyethylenimine diazeniumdiolate from said inner layer into the physiological medium.

The invention also provides for a method for the manufacture of a medical device suitable for intravascular use, said method comprising, (a) selecting a medical device suitable for use in vascular surgery, said medical device comprising a base material; (b) optionally applying a primer layer to the surface of the base material; (c) applying an inner layer (refered to herein as the first domain) onto the surface of the base material or the surface of a primer layer, said inner layer (first domain) comprising polyethylenimine diazeniumdiolate; (d) Applying an outer layer which comprises a polymer which controls, reduces or prevents the release of polyethylenimine diazeniumdiolate from said inner layer (first domain) into the physiological medium.

The invention also provides for a method for the manufacture of a medical device suitable for intravascular use, said method comprising, (a) selecting a medical device suitable for use in vascular surgery, said medical device comprising a base material or a inner layer (first domain) which comprises polyethylenimine diazeniumdiolate; (b) Applying an outer layer (also refered to herein as the outer -coat) which comprises a polymer which controls, reduces or prevents the release of polyethylenimine diazeniumdiolate from said inner layer into the physiological medium.

The invention also provides for the use of the outer-coat and/or alkali stabilised (L)PEI-NONO composition, for the manufacture of a medical device comprising (L)PEI-NONO, for use intravascular or neurovascular use, for the prevention of one or more the conditions selected from: vasospasm or vasoconstriction, prevention of cerebral vasospasm, relaxation of smooth muscle, vasodilatation, thrombosis, decreased platelet deposition or aggregation, alleviation of restenosis, increased blood pressure, oxygen free radical reperfusion injury, treatment of cardiovascular disease, preventing the adverse effects associated with the use of said medical device, preventing abnormal cell proliferation.

The invention also provides for the use of the outer layer (coat) to control the rate of release of polyethylenimine diazeniumdiolate from the surface of a medical device which comprises polyethylenimine diazeniumdiolate when said medical device is inserted in vivo.

In one embodiment, the outer layer may control the release of nitric oxide from said inner layer into the physiological medium, and/or the diffusion of water from the physiological medium into the inner layer under physiological conditions and/or the leakage of small molecule by products from said polymer mixture into the physiological medium.

The present invention also provides an alkaline formulation of polyethylenimine diazeniumdiolate, and a medical device which comprises an alkaline formulation of polyethylenimine diazeniumdiolate (pH greater than 7).

The invention provides for a method for the preparation of a (alkali) stabilised formulation of polyethylenimine diazeniumdiolate, suitable for use in the coating of intravascular medical devices, said method comprising dissolving polyethylenimine diazeniumdiolate (LPEI-NONO) in a alkali organic solvent. The solvent may be any suitable solvent, such as a solvent selected from the group consisting of: an alcohol, ethanol, methanol, aniline, benzaldehyde, cyclohexylamine dimethyl sulfoxide, preferably methanol The water content of the organic solvent is preferably less than 1%, such as less than 0.5. The concentration of polyethylenimine diazeniumdiolate which may be dissolved in the solvent will depend on the solvent used. However, typically the level of polyethylenimine diazeniumdiolate dissolved in the solvent is (in w/w terms) between about 0.2% to about 20%, such as from about 1% to about 10%, such as about 1% to about 5%, such as about 2%.

The invention also provides for a composition comprising an alkali stabilised polyethylenimine diazeniumdiolate, suitable for use in the coating of intravascular medical devices. Suitably the composition comprises polyethylenimine diazeniumdiolate dissolved in an alkali solvent, suitably at a concentration of about (w/w) 0.2% to about 20%, such as from about 1% to about 10%, such as about 1% to about 5%, such as about 2%.

The composition comprising an alkali stabilised polyethylenimine diazeniumdiolate composition may further comprises a further polymer such as hydrophilic polymer or a structural polymer as referred to herein, preferably a polyurethane polymer and/or the hydrophilic support polymer or polymer blend or coating system as referred to herein.

The present invention provides for a medical device which comprises at least a first domain which comprises polyethylenimine diazeniumdiolate, wherein the pH of the first domain is greater than pH 7. Suitably, the medical device is capable of releasing nitric oxide (suitably from the polethylenimine diazeniumdiolate) to a body of a living being upon wetting of at least a portion of a surface of the medical device.

The invention also provides for a method for the manufacture of a medical device suitable for intravascular use, said method comprising, (a) selecting a medical device suitable for use in vascular surgery, said medical device comprising a base material; (b) optionally applying a primer layer to the surface of the base material; (c) applying an inner layer (first domain) onto the surface of the base material or the surface of a primer layer (or the external surface of the medical device, such as on a further domain or layer, such as the second or third domains as referred to herein), said inner layer (first domain) comprising an alkali formulation of polyethylenimine diazeniumdiolate; (d) optionally applying an outer layer which comprises a polymer which controls, reduces or prevents the release of polyethylenimine diazeniumdiolate from said inner layer (first domain) into the physiological medium. The method for the manufacture of a medical device suitable for intravascular use, may therefore comprise the following steps, (a) selecting a medical device suitable for use in vascular surgery, (b) applying a first domain which comprises an alkali formulation of polyethylenimine diazeniumdiolate (or composition comprising said formulation) to said medical device (typically to the external surface, such as to the base material or a primer layer or one of the further domains refered to herein); (c) optionally applying an outer layer which comprises a polymer which controls, reduces or prevents the release of polyethylenimine diazeniumdiolate from said first domain into the physiological medium.

In the method for the manufacture of a medical device according to the invention a second domain and/or third domain as referred to herein may be applied either prior to, during or subsequent to the application of the first domain.

The invention also provides for the use of the an alkali formulation of polyethyleninime diazeniumdiolate, or composition comprising said formulation (such as the first domain as referred to herein) according to the invention, for the manufacture of a medical device for intravascular or neurovascular use, such as for the prevention or treatment of one or more the conditions selected from: vasospasm or vasoconstriction, prevention of cerebral vasospasm, relaxation of smooth muscle, vasodilatation, thrombosis, decreased platelet deposition or aggregation, alleviation of restenosis, increased blood pressure, oxygen free radical reperfusion injury, treatment of cardiovascular disease, preventing the adverse effects associated with the use of said medical device, preventing abnormal cell proliferation,

and/or

the invention also provides for the use of the an outer-layer according to the invention, for the manufacture of a medical device for use intravascular or neurovascular use, such as for the prevention or treatment of one or more the conditions selected from: vasospasm or vasoconstriction, prevention of cerebral vasospasm, relaxation of smooth muscle, vasodilatation, thrombosis, decreased platelet deposition or aggregation, alleviation of restenosis, increased blood pressure, oxygen free radical reperfusion injury, treatment of cardiovascular disease, preventing the adverse effects associated with the use of said medical device, preventing abnormal cell proliferation.

The invention therefore also provides for a method of therapy (including prevention/prophylaxis), such as a method of therapy (surgery, vascular surgery, or intravascular intervention) of one or more the conditions selected from: vasospasm or vasoconstriction, prevention of cerebral vasospasm, relaxation of smooth muscle, vasodilatation, thrombosis, decreased platelet deposition or aggregation, alleviation of restenosis, increased blood pressure, oxygen free radical reperfusion injury, treatment of cardiovascular disease, preventing the adverse effects associated with the use of said medical device, preventing abnormal cell proliferation.

The invention provides for a method of performing intravascular intervention (or vascular surgery) using the intravascular medical device according to the invention, such as for a method of therapy (including prevention/prophylaxis) of one or more the conditions selected from: vasospasm or vasoconstriction, prevention of cerebral vasospasm, relaxation of smooth muscle, vasodilatation, thrombosis, decreased platelet deposition or aggregation, alleviation of restenosis, increased blood pressure, oxygen free radical reperfusion injury, treatment of cardiovascular disease, preventing the adverse effects associated with the use of said medical device, preventing abnormal cell proliferation.

The present invention further provides for the use of a multi-layered (domain) coating system for use in coating of medical devices, such as intra-vascular medical devices, ϊn one aspect the coating system comprises a first domain comprising an alkaline formulation of (L)PEI-NONO, and a second (acidic) domain, which, upon wetting of the medical device - e.g. during use in intravascular surgery, results in the transfer of protons from the second domain into the first domain, thereby resulting in shifting the local balance between H⁺ and OH^" ions within the first domain, effectively reducing the pH in the first domain, and thereby destabilising the 'alkali' stabilised (L)PEI-NONO resulting in the therapeutic release of NO.

By adjusting the buffering capacity of the alkali first domain and/or the concentration of diffusible protons in the second domain, it is possible to both ensure that the premature release of NO is reduced or effectively prevented, and to control the timing and release of NO from the surface of the medical device.

Typically, for transient medical devices, such as introducer sheaths, guide wires, catheters, microcatheters, and balloon catheters, it is preferable that the alkali used does not have a significant buffering capacity. However, for implants, such as stents and embolisation devices, it may be preferable that the alkali is in the form of an alkaline buffer as this can ensure a prolonged release profile of NO.

Therefore, it is an object of preferred embodiments of the present invention to provide a medical device and a method allowing for a controlled release rate of nitric oxide from such medical devices (e.g. balloon catheter systems, guide wires or introducer sheaths). It is a further object of preferred embodiments of the invention to provide a medical device, such as a coated balloon, guide wire, or introducer sheath, of high mechanical strength that maintains its mechanical integrity during surgical intervention. It is a further object of preferred embodiments of the invention to provide a medical device and method of its use, which allows for lapse of a predetermined period of time from wetting of the device to release of a therapeutic agent contained in the device. It is a further object of preferred embodiments of the invention to provide a coated balloon catheter having a balloon that can be folded, stored, sterilised and unfolded without adhesion between coated surfaces of the balloon. It is a further object of preferred embodiments of the invention to provide a multi- layered coating on a medical device allowing for essentially instant wetting of the entire coating even though the surface has been folded prior to use. It Is a further object of preferred embodiments of the invention to provide a coating for a medical device that has a low surface friction to enable convenient placement of the device, e.g. placement of a balloon prior to inflation thereof.

In a one aspect the invention provides a medical device for release of a therapeutic agent (nitric oxide) to a body of a living being upon wetting of at least a portion of a surface of the medical device, for example by bodily fluids, the medical device including at least a first domain and a second domain, wherein:

- the first domain is capable of releasing the therapeutic agent at a release rate;

- the second domain is capable of affecting pH of at least one of the first domain and the second domain by shifting the local balance between H⁺ and OH^" ions upon wetting of at least a portion of the medical device; and wherein:

- the release rate of the therapeutic agent from the first domain is dependent on the pH of at least one of the first domain and the second domain.

In a further aspect the invention provides a medical product comprising the medical device of the invention, the medical device being packed in a package, which prevents moisture, oxygen and/or light from entering the package.

In a further aspect the invention provides the use of a therapeutic agent in the preparation of a disposable medical device for the treatment of a cell disorder in a body duct, the medical device including at least a first domain and a second domain, wherein:

- the first domain is capable of releasing the therapeutic agent at a release rate; - the second domain is capable of affecting pH of at least one of the first domain and the second domain by shifting the local balance between H⁺ and OH^" ions upon wetting of at least a portion of the medical device; and wherein:

- the release rate of the therapeutic agent from the first domain is dependent on the pH of at least one of the first domain and the second domain. In a further aspect the invention provides a method of releasing a therapeutic agent, from a medical device, the medical device including at least two domains, a first domain and a second domain, of which the first domain is capable of releasing the therapeutic agent at a release rate, and the second domain is capable of affecting pH of the first domain, by shifting the local balance between H⁺ and OH^" ions upon wetting of at least a portion of the medical device, and wherein the release rate of the therapeutic agent from the first domain is dependent on the pH of at least one of the first domain and the second domain, the method comprising the steps of:

- placing the medical device in contact with a bodily fluid of a living being; - wetting the medical device to thereby cause transport of H⁺ or OH^' ions from one of the first and second domains to the other domain to thereby increase rate of release of the therapeutic agent from the first domain to body tissue.

In a further aspect the invention provides a method of applying a coating to a surface of a medical device, the coating including at least one therapeutic agent, the method comprising the steps of:

- arranging the medical device in a confined environment, e.g. a manufacturing space; and subsequently:

- applying the coating to the surface of the medical device while controlling the pH of the confined environment to inhibit release of the therapeutic agent from the medical device, such as in an alkaline environment.

As an alternative to a confined environment, a solution of the coating may contain a buffer that controls pH. For example, poly(ethylenimine) diazeniumdiolate, such as linear poly(ethylenimine) diazeniumdiolate (L-PEI-NONO) as disclosed in US 6,737,447 may be dissolved in a pH-controlling agent, such as NaOH typically dissolved in an organic solvent (as referred to herein, such as pyridine or an alcohol, such as methanol). A further alternative is to feed e.g. a spray gun applying the coating with pH-controlling gas, such as ammonia. In the presence of liquid, ammonia will cause the spray mist to become basic. Other alkali gases may be used as appropriate.

The invention therefore provides for methods for the treatment of e.g. smooth muscle cell proliferation to reduce restenosis, for prevention or reduction of inflammation such as imflammation caused by insertion of foreign objects or devices into the patient, for the inhibition of aggregation of platelets and/or for vasodilation. Such methods comprising using the medical device according to the invention in a surgical procedure, such as intravascular surgery/intervention. Detailed description of the invention

The NO Adduct (The Therapeutic Agent)

Various nitric oxide (NO) donor compounds and polymeric compositions capable of releasing nitric oxide have been proposed in the prior art, e.g. US 5,519,020, US 5,691,423, US 5,770,645, US 5,814,656, US 5,962,520, US 5,958,427, US 6,147,068, and US 6,737,447 Bl (corresponding to EP 1220694 Bl).

Polyimines represent a diverse group of polymer which may have diazeniumdiolate moieties covalently bound thereto. Polyimines include poly(alkylenimines) such as poly(ethylenimines). For example, the polymer may be a linear poly(ethylenimine) diazeniumdiolate (L-PEI-NONO) as disclosed in US 6,737,447 which is hereby incorporated by reference. The loading of the nitric oxide donor onto the linear poly(ethylenimine) (PEI) can be varied so that 5-80%, e.g. 10-50%, such as 33%, of the amine groups of the PEI carry a diazeniumdiolate moiety. Depending on the applied conditions, the (L)-PEI-NONO can liberate various fractions of the total amount of releasable nitric oxide.

Polyimines with diazeniumdiolate moieties (in particular linear poly(ethylenimine) diazeniumdiolate) may e.g. be used as polymers for an electrospinning process because such polymers typically have a suitable hydrophilicity and because the load of diazeniumdiolate moieties (and thereby the load of latent NO molecules) can be varied over a broad range, cf. the above example for PEI-NONO.

A most preferred nitric oxide adduct polymer is polyethylenimine diazeniumdiolate, such as linear polyethylenimine diazeniumdiolate (LPEI-NONO). PEI-NONO also exists as a branched polymer, which may also be used, although LPEI-NONO (linear) form is preferred.

US 6,855,366 provides methods for the preparation to LPEI-NONO. The loading of the nitric oxide donor onto the linear poly(ethylenimine) (PEI) can be varied so that 5-80%, e.g. 10- 50%, such as about 20 to about 40%, such as about 30% of the amine groups of the PEI carry a diazeniumdiolate moiety. Depending on the applied conditions, the L-PEI-NONO can liberate various fractions of the total amount of releasable nitric oxide.

The MW of the nitric oxide adduct polymer, will, in one embodiment, such as when the NO adduct is LPEI-NONO, depend upon the size of the starting materials used to prepare the NO adduct, and in some cases the degree of branching of the polymer. Typically, larger polymers sizes are preferable in terms of reducing in vivo solubility, however, large polymers may also interfere with the ability to solubilise and coat the medical device. In the case of LPEI-NONO, the use of branched precursors results in cleavage of the molecular structure at branch points, reducing the average molecular weight of the polymer molecules present in the final NO polymer adduct. Hence MW may be used to define whether the LPEI-NONO is linear:

In a preferred embodiment, the nitric oxide adduct, such as the LPEI-NONO polymer has an average molecular weight of between about 5kDa and about 20OkDa, such as between about 1OkDa and about 10OkDa, such as more preferably between about 3OkDa and about 7OkDa, such as about 55kDa with a preferred polydispersity between about 1 and about 3 and more preferably about 2.

The average molecular weight is determined by size exclusion chromatography (SEC) of the polymer backbone, linear polyethyleneimine (L-PEI) using various polyethylene glycols (PEG) with known molecular weights as standards. The total amount of NO in the NO loaded polymer (L-PEI-NONO) can be determined by elemental analysis (EA). Hence, the average molecular weight of the NO loaded polymer (L-PEI-NONO) can be calculated based on the results from the size exclusion chromatography (SEC) and the elemental analysis (EA).

In a preferred embodiment, the nitric oxide adduct, which may form a coating (i.e. an NO eluting coating), is, or is based on linear polyethyleneimine (L-PEI) with pendant NONO groups.

Each NONO group is covalently attached to one of the N atoms in the L-PEI polymer chain thereby forming an N* - N⁺(O^')=N-O^' group in which N* is one of the atoms of the L-PEI backbone. This group is stabilized by the formation of a Zwitter-ion complex with an adjacent -NH₂ ⁺- amine group in the L-PEI backbone.

The nitric oxide loaded linear polyethyleneimine (L-PEI-NONO) releases the nitric oxide when it is exposed to a proton donating (H⁺) environment like ionized water or blood.

To assist stabilize the coating the device is typically stored in a sealed aluminum pouch with an inert gas, such as a N₂ atmosphere. The product is thereby protected against moisture, light and oxygen during storage. Typically, such as when using N₂(g) atmosphere the moisture content is 6% or below, and the 0₂(g) is about 2% or below. The moisture and 0₂(g) levels may be further reduced by using moisture and oxygen absorbing agents, such as those referred to herein), thereby in a preferred embodiment, the level of moisture is about 0.1% or below, and the level of 0₂(g) at about 0.01% or below. Incorporating the L-PEI-NONO into a polymer matrix, allows controlled release of nitric oxide. When introduced into the vascular system the nitric oxide is delivered to the vessel wall by diffusion.

The nitric oxide dose delivered to the vessel wall (i.e. the target location) is determined by the release rate and the time in contact with the artery wall. The dose delivered to the target, i.e. the smooth muscle cell (SMC), depends furthermore on the thickness of the vessel wall, potential plaque, presence of blood/hemoglobin, the presence of oxygen and the diffusion constant (D).

It has been recognised that polymeric NONOates, such as those which contain diazeniumdiolate groups can generate undesirable small molecule side products such as nitrosamines (see US 6,875,840). The present invention overcomes the generation and/ or release of undesirable small molecule side products, whilst allowing controlled release of nitric oxide under physiological conditions by the incorporation of polymeric NONOates, such as polyethyleminine diazeniumdioiate, in a hydrophilic support polymer or polymer blend.

In one embodiment, density of application of the NO adduct, such as polyethylenimine diazeniumdiolate onto the surface of the medical device is between about 0.05 and about lOOmg/cm², such as between about 0.1 and about 10 mg/cm², such as preferably between about 0.2 and about 0.5 mg/cm².

In one embodiment, density of application of the NO adduct, such as polyethylenimine diazeniumdiolate onto the surface of the medical device is between about 0.05 and about 200 μmol NO/cm², such as between about O.land about 20 μmol NO/cm², such as preferably between about 0.3 and about 1 μmol NO/cm².

In one embodiment, the invention provides for alkali stabilised formulations of polyethylenimine diazeniumdioiate, such as linear polyethylenimine diazeniumdiolate, and medical devices which comprise, such as are coated with such alkali stabilised formulations, such as medical devices which comprise at least said first domain as described herein.

We have discovered that despite the use of non-aqueous solvents such as methanol, as a solvent for polyethylenimine diazeniumdiolate, the release of NO from polyethylenimine diazeniumdiolate can occur prematurely, such as during the formulation, storage and processing of the polyethylenimine diazeniumdiolate, resulting in sub-optimal nitric oxide donation capacity. In the case that formulation and processing of the nitric oxide adduct occurs in the presence of oxygen (e.g. during spray coating of medical devices), formation of nitrite is an unavoidable effect of spontaneous nitric oxide release. The invention therefore provides for a method of preparing alkaline formulations of polyethylenimine diazeniumdiolate, comprising dissolving the polyethylenimine diazeniumdiolate in alkaline organic solvents, such as alcohols, such as ethanol and methanol, tetrahydrofurane, pyridine, and the like.

The alkali solvents are typically prepared by dissolving suitable alkali compounds (bases) prior to the addition of the (L)PEI-NONO polymer. The OH^" added should be between about about 0.1 μM to about 2 mM OH- such as between 0.001 mM to about 1 mM OH- such as about between 0.0ImM and about 0.5mM, such as between about 0.05mM and about 0.2mM about 0.1 mM. The pH of the solvent is modulated by adjusting the amount of alkali added.

Numerous suitable alkali agents may be used, such as inorganic alkali, such as NaOH, KOH, Ca(OH)₂, and LiOH, or organic alkali, such as lithium diisopropylamide and methylamine. The alkali may ben a organiic or inorganic alkali buffer such as phosphate (pK2), ethanolamine, ADA, carbonate (pKl), ACES, PIPES , MOPSO, imidazole, BIS-TRIS propane, BES, MOPS, HEPES, TES, MOBS, DIPSO , TAPSO, triethanolamine (TEA), pyrophosphate, HEPPSO, POPSO, tricine, hydrazine, glycylglycine (pK2), Trizma (tris), EPPS, HEPPS, BICINE, HEPBS, TAPS, 2- amino-2-methyl-l,3-propanediol (AMPD), TABS, AMPSO, taurine (AES), borate, CHES, 2- amino-2-methyl-l-propanol (AMP), glycine (pK2) , ammonium hydroxide, CAPSO, carbonate (pK2), methylamine , piperazine (pK2), CAPS, CABS, and pipidine.

Suitably, the pH of the first domain is such that the OH^'concentration is between about 0.02 mM to about 2 mM OH^" such as between 0.05 to about 1 mM OH^" such as about 0.1 mM.

Most preferred is an alkali methanol, such as NaOH dissolved in methanol (typically at a concentration of between 0.1 and 10 μg/ml, such as between 1 and 2 μg/ml, such as about 1.67μg/ml).

A key aspect in controlling this premature release of nitric oxide from polyethylenimine diazeniumdiolate is to increase the pH of the polyethylenimine diazeniumdiolate (local environment - e.g. first domain) to above 7, such as between pH 8 and 13.

The First Domain

The first domain is a discrete domain which does not form a homogenous phase with the second domain, if present. In a preferable embodiment, the first domain may be in the form of a uniform layer of approximately uniform thickness. However, it will be apparent to the skilled person that the first domain may be in many other forms.

The first domain may comprise the hydrophilic supporting polymer or polymer blend combined with one or more alkali (base) agents or basic side groups. The hydrophilic supporting polymer or polymer blend suitable for use in the first domain is described in EP application No. 06023223 and US provisional 60/864,886.

In one embodiment, the first domain may form discrete particles, such as nanoparticles, which are embedded into a further domain, such as the second domain. Alternatively the second domain may form discrete particles which are embedded in a further domain, e.g. the outer-layer and/or the first domain.

In one embodiment the first domain is in the form of LPEI-NONO fibres, such as electrospun fibres or nanofibres.

However, in one embodiment, the first domain is not in the form of, or does not comprise, LPEI-NONO fibres, such as electrospun fibres or nanofibres.

It is preferable that the first domain forms a homogeneous phase.

The pH of the first domain may be controlled in numerous ways known in the art. For application to a medical device, (L)PEI-NONO is typically dissolved in a non-aqueous solvent,

Typically the first domain is an alkaline domain, i.e. when it comes into contact with a suitable solvent, for example water, the pH of the local domain is above pH 7, such as above about pH 7.5, such as above about pH 8, such as above about pH 9, such as above about pH 10, such as above about pH 11, such as above about pH 12, such as above about pH 13, such as about pH 14, or such as between above pH 7 and about pH 14. In a preferred embodiment the pH of first domain is between about pH 9 and about pH 12, most preferred between about pH 8 and about pH 11, such as between about pH 9 to about pH 10. We have noted that high pH, e.g. 12 and above, the polymer systems, such as the hydrophilic support polymer/polymer blend, that the high pH can alter the physical properties of the polymer, which is some cases may be detrimental, for example high pH may effect the stability of the coating systems.

The first domain therefore typically comprises an alkaline compound which may be organic or inorganic. Suitable inorganic alkali compounds include by way of example NaOH, KOH, Ca(OH)₂, and LiOH. Suitable alkali organic compound include, by way of example lithium diisopropylamide and methylamine. The alkali compound may be a alkaline buffer, such as a buffer selected formt he group consisting of: phosphate (pK2), ethanolamine, ADA, carbonate (pKl), ACES, PIPES , MOPSO, imidazole, BIS-TRIS propane, BES, MOPS, HEPES, TES, MOBS, DIPSO , TAPSO, triethanolamine (TEA), pyrophosphate, HEPPSO, POPSO, tricine, hydrazine, glycylglycine (pK2), Trizma (tris), EPPS, HEPPS, BICINE, HEPBS, TAPS, 2-amino-2-methyl- 1,3-propanediol (AMPD), TABS, AMPSO, taurine (AES), borate, CHES, 2-amino-2-methyl-l- propanol (AMP), glycine (pK2) , ammonium hydroxide, CAPSO, carbonate (pK2), methylamine , piperazine (pK2), CAPS, CABS, and pipidine.

The alkaline compound may also be an alkaline polymer, such as a polymer containing a inorganic or organic base, such as an alkaline side group.

The alkaline compound, including alkali polymers, preferably has a pKb of less than 6, more preferable a pKb of less than 5

The alkali compound or group may be selected from the group consisting of a primary amine, a secondary amine and a tertiary amine.

The alkali compound or group may be selected from the group consisting of lithium diisopropylamide, methylamine, chloroquine

In addition to (alkali formulation) (L)PEI-NONO the first domain typically comprises a further polymer, such as a polyurethane, or a hydrophilic structural polymer or polymer blend as referred to herein (see under coating systems).

In one embodiment, the first domain may comprise a polymer selected from the group consisiting of: polyolefins, such as polystyrene, polypropylene, polyethylene, polytetrafluorethylene, polyvinylidene difluoride, polyvinylchloride, derivatized polyolefins such as polyethylenimine, polyethers, polyesters, polyamides such as nylon, polyurethanes, silicones.

In one embodiment, the first domain may comprise a polymer selected from the group consisiting of: aromatic polyurethanes, ethylene acrylate polyolefins, hydrophilic aliphatic polyurethanes or silicones, all with a high ratio of water conductance towards water absorbance. These polymers can be selected from the tecophilic, estane, EMAC and EBAC polyolefins families or high water vapour conducting silicones.

In one embodiment, the first domain may comprise a polymer selected from the group consisiting of: polyolefins, such as polystyrene, polypropylene, polyethylene, polytetrafluorethylene, polyvinylidene difluoride, polyvinylchloride, derivatized polyolefins such as polyethylenimine, polyethers, polyesters, polyamides such as nylon, polyurethanes with good adhesion and structural stability, fulfilling the stability criteria stated above. However, it could preferably be an aliphatic polyether-based polyurethane such as eg. Tecoflex SG 85A.

The Second Domain

The second domain is a discrete domain which does not form a homogenous phase with the first domain. In a preferable embodiment, the second domain may be in the form of a uniform layer of approximately uniform thickness. However, it will be apparent to the skilled person that the second domain may be in many other forms.

The second domain may comprise the hydrophilic supporting polymer or polymer blend combined with one or more acidic agents or acidic side groups. The hydrophilic supporting polymer or polymer blend suitable for use in the second domain is described in EP application No. 06023223 and US provisional 60/864,886.

The second domain may form discrete particles, such as nanoparticles, which are embedded into a further domain, such as the first domain. Alternatively the second domain may form discrete particles which are embedded in a further domain, e.g. the outer-layer and/or the first domain.

In one embodiment the second domain may also comprise (L)PEI-NONO. However, in one preferred embodiment, the second domain does not comprise (L)PEI-NONO.

In one embodiment, the second layer is not in the form of, or does not comprise, LPEI-NONO fibres, such as electrospun fibers or nanofibers.

It is preferable that the second domain forms a homogeneous phase.

The pH of the second domain may be controlled in numerous ways known in the art. For example, the second domain may e.g. comprise ascorbic acid, polyacrylic acid, lactic acid, acetic acid and/or oxylic acid as H⁺-releasing agents for affecting release of the therapeutic agent from the first domain. The second domain may comprise a polymer which is acidic, or comprises acidic side groups, which are capable of releasing protons upon contact with water. Further acidic agents or side groups, which may be used in the second domain include lactic acid or vitamin C, and/or an acid agent selected from the group consisting of: ascorbic acid, polyacrylic acid, oxylic acid, acetic acid and lactic acid.

The acidic agent may have a pKa of less than 6, more preferable any organic acid with a pKa of less than 5.

In one embodiment the acidic agent is an inorganic acid, such as hydrochloric acid, sulphuric acid, nitric acid or hydrobromic acid.

The acidic agent may be, or comprise an acidic buffer, such as a buffer selected form the group consisting of: maleate (pKl), phosphate (pKl), glycine (pKl), citrate (pKl), glycylglycine (pKl), malate (pKl), formate, citrate (pK2), succinate (pKl), acetate, propionate, malate (pK2), pyridine, piperazine (pKi), cacodylate, succinate (pK2), MES, citrate (pK3), maleate (pK2), histidine, bis-tris, phosphate (pK2), ethanolamine, ADA, and carbonate (pKl).

The acidic compound may be, in one embodiment, a polymer containing an inorganic or organic acid such as a side group. In a preferable embodiment, the acidic compound, such as the acidic polymer comprises carboxylic groups.

The acidic compound may therefore be a fruit acid, or an equivalent, for example a hydroxy acid, or an acidic derivative thereof.

Therefore, it is considered that the second domain may be either internal or external to the first domain.

The second domain is capable of affecting the pH of the first domain by shifting the local balance between H⁺ and OH^" ions upon wetting of at least a portion of the medical device, i.e. the second domain is capable of reducing the pH of the first domain upon wetting of at least a portion of the medical device. Therefore release rate of the nitric oxide from the first domain is dependent on the pH of at least one of the first domain and in one embodiment the second domain.

Typically the second domain is an acidic domain, i.e. when it comes into contact with a suitable solvent, for example water, the pH of the local domain is below pH 7, such as below about pH 6.5, such as below about pH 6, such as below about pH 5, such as below about pH 4, such as below about pH 3, such as below about pH 2, such as about pH 1, or such as between below pH 7 and about pH 1. The pH of the second domain may, for example be between about pH 2 and about pH 6. or between about pH 3 to about pH 5.

We have also noted that at very low acidity, such as below pH 2, the acidity can effect the physical properties of the polymers used in the second coat, and this may effect the stability of the coat detrimentally.

First and second domains

In one embodiment of the invention, the medical device is at least partially coated with both a first and a second domain.

In one embodiment, the first domain comprises a first coating layer of the device which is applied to, or is immediately adjacent to, either the base material of the medical device or the primer layer. The second domain may therefore comprise a second coating layer of the device which is applied to, or is immediately adjacent to said first coating

Suitably, the release rate of the nitric oxide from the first domain is dependent on the pH of at least one of the first domain and/or the second domain.

The first and second domains may have any form or shape, however, layered structures are preferred, such that the first domain forms one coating layer and that the second domain forms another coating layer. For example, the medical device may be coated with one material forming the second domain as an initial surface coating, which subsequently is being covered with another material forming the first domain as a further coating layer onto of the initial surface coating. For some applications it may be preferable that the donor-compound containing layer (i.e. first domain) is applied prior to the pH modifying layer (i.e. second domain), whereas it may be preferable for other applications that the pH modifying layer (i.e. second domain) is applied prior to the donor layer (i.e. first domain). It is also envisaged that the two layers may be applied simultaneously, for example by extrusion of two independent layers, or by coating of a layer which comprises both the first and second domains, e.g. for example when the first and/or second domains are in the form of particles, one domain may form a 'matrix', whist the other domain forms discrete (i.e. non- homogeneous) particles, such as nano-particles within the 'matrix' domain, or both first and second domains may be in the form of discrete particles within a suitable matrix composition, such as the hydrophilic supporting polymer or polymer blend referred to herein.

In the embodiment where there is at least a first domain and a second domain, the first domain is capable of releasing one or more therapeutic agents, the release rate being e.g. dependent on the pH of the domain. As the second domain is capable of affecting the pH of the first domain by release of H⁺ ions, upon wetting of at least a portion of the medical device, the pH of the first domain increases upon wetting of a portion of the device, and accordingly the release of the therapeutic agent is triggered or enhanced. The pH of the first domain changes upon wetting of the second domain due to transport of H⁺ ions from the second domain to the first domain.

Hence, in one preferred embodiment, the present invention provides for the controlled release of the therapeutic agent (typically nitric oxide) in dependency of the humidity or water content of a portion of the medical device, such as the water content of the second domain. In a typical application of the medical device, the second domain is wetted by blood upon entry into the vascular system of a human or animal body. The timing of the release of nitric oxide may be further influenced by the arrangement of the first and second domains, and by the addition of further layers, such as the outer-coat. In one embodiment, the outer- coat provides a further protection against premature release of NO by preventing the premature hydration of the first and/or second domains. This may be achieved by utilising an outer-coat which is, for example, is only partially permeable to water, or only permeable to water vapour, for example an outer-coat made of a hydrophobic polymer - such outer- coats are particularly useful for delayed release, for example in the case of implants such as stents. Suitable hydrophobic polymers are known in the art and include various polymers such as silicones (which may for example be permeable to water vapour but not water) and polyvinyl chloride (PVC) polyurethanes (PU), polyacrylates or other polymers with restricted water conductance or mixtures hereof.

In a preferred embodiment, the second domain is applied prior to, i.e. is interior to, the first domain. This ensures that as the protons diffuse out of the second domain to the external environment they must pass through the first domain, thereby ensuring the maximum NO release.

Herein, the first domain is also referred to as the bioactive domain, and the second domain is also referred to as the pH active domain. However, it should be recognised that that the first domain is also pH active, but in contrary to the second domain the pH (or potential pH upon wetting) of the first domain is alkaline, where as the pH (or potential pH upon wetting) of the second domain is acidic.

The Third Domain

The medical device may comprise a third domain. The third domain may be an additional domain which is positioned between the first domain and the second domain.

In one embodiment, the medical device may comprise a first domain and a third domain.

The third domain may be a neutral layer, which controls the rate of influx of water (and protons) from the body fluid (optionally via the second domain) into the first domain. The third domain may, in one embodiment, comprise a buffer, which limits the influx of protons into the first domain, thereby providing for 'long and low' NO release kinetics.

By using a third domain of about neutral pH (7) between the fist and second domains, the premature degradation of the (L)PEI-NONO (NO release) can be avoided or reduced even further, this particularly relevant during the processing steps (manufacture) involved in preparation of the medical device.

In one embodiment the third domain comprises or consists of the hydrophilic supporting polymer or polymer blend as referred to herein, such as that disclosed in EP application No. 06023223 and US provisional application 60/864/886.

In one embodiment, the third domain consists or comprises a hydrophilic polymer.

In one embodiment, the third domain consists or comprises a hygroscopic polymer.

The third domain may comprise a buffer, such as a buffer of pH around 7, when it comes into contact with water. As such the third domain can control the rate at which the protons diffuse from the second domain into the first domain by acting as a proton quencher. This is useful when the medical device may come into contact with water or water vapour prior to the time at which the therapeutic release is required or optimal. Likewise the third domain can act as a -OH quencher, preventing the undesirable alkalisation of the acidic layer.

The thickness of the third domain, may, for example be between about O.lμm and about 10μm, such as between lμm and about 5μm.

In one embodiment the third domain does not comprise a buffer. In one embodiment the pH of the third domain is about 7.

It is recognised that the composition of the outer-coat and the third layer may, in one embodiment be identical. Inner Priming Layer

A primer is typically a first coating formulated to seal raw surfaces and hold succeeding finish coats.

In a preferred embodiment, the base material of the medical device (i.e. external surface and/or the surface which comes into contact with the physiological media, is coated with an inner priming layer between the base layer of the medical device and said first or second domains (or coating systems as referred to herein) or nitric oxide adduct.

In one embodiment the inner priming layer may be selected from the group consisting of polyolefins, such as polystyrene, polypropylene, polyethylene, polytetrafluorethylene, polyvinylidene difluoride, polyvinylchloride, derivatized polyolefins such as polyethylenimine, polyethers, polyesters, polyamides such as nylon, polyurethanes.

Suitably the inner priming layer has good adhesion and structural stability, withstanding a traction force applied to the surface of the polymer coat of about 4 to 100 Newton cm^"2 such as about 8 to 50 newton cm^'2 such as preferably between 10 tp 20 Newton cm^"2.

A preferred primer polymer is an aliphatic polyether-based polyurethane such as eg. Tecoflex SG 85A.

In one embodiment, the thickness of the priming layer is between 0.2 and 5μm. The priming layer need not be uniform in thickness, over the surface as its role is to secure the coating and/or NO adduct to the medical device. It is therefore required to provide sufficient anchor points to provide a robust platform on which to apply the addition coating(s). Preferably, the priming layer has effectively complete coverage over the base material to be coated as this ensures maximum structural integrity of the subsequent layers.

Further layers

As described above with respect to the method for the manufacture of a sterilised medical device, a further layer or layers may be applied over the nitric oxide adduct (first domain), such as the coating system or fibre layers. Such further layers include the second domain and third domains as well as the outer-coating (outer-layer) as herein disclosed.

In one embodiment, at least one of the first, second, third domains comprises polyurethane, such as both the first and second domains, such as the first and third domains. Therefore in one embodiment, the medical device according to the invention comprises a nitric oxide adduct (first domain) capable of releasing nitric oxide under physiological conditions as herein described, and at least one further layer (second domain) of a material which is capable of affecting the pH of the nitric oxide adduct (the first domain), such as the nitric oxide adduct coating system or fibres, upon insertion into physiological media.

In one embodiment, it is preferred that the further layers (including the outer layer referred to below) are sufficiently flexible to allow movement and flexing of the medical device without risking the integrity of the further layers. Suitably, the further layers may be hydroscopic and swell with water when in use. The routine submersion of medical device, e.g. the introducer sheath apparatus, in isotonic solution prior to use therefore allows the further layers to absorb sufficient water to ensure sufficient flexibility, and reduced friction upon insertion. Some polymers, for example the tecophillic polymers used for the outer coating, may swell to about 60% of their volume when inserted in aqueous media. A further advantage of using further coats of polymers which swell is that the swelling will mask any pin-hole defects or imperfections in the further coats, therefore ensuring the integrity of the coating system when in use.

Whilst it is, in one embodiment, preferable that the further layer or layers are applied externally to said nitric oxide adduct (i.e. located between the nitric oxide adduct and the physiological media when in use), it is also recognised that the further layer may be applied as a layer between the base material of the medical device and the nitric oxide adduct

In a preferred embodiment, an outer coating as herein described is also applied. The outer coating may be applied directly to the coating system layer, or to one or more further layers applied to the coating system layer.

The Outer Layer (Outer coating)

It is preferred that the medical device comprises an outer layer situated externally to the first domain, and if relevant any further domains. Typically, the outer layer comprises a polymer which controls one or more of the following: i) the release of the (L)PEI-NONO from said inner layer into the physiological medium, e.g. either by forming a diffusion barrier between the nitric oxide releasing adduct and the physiological medium, or by applying a high diffusion resistance to the diffusing molecule and thereby significantly slowing down the diffusion process; ii) the release of nitric oxide from said inner layer into the physiological medium by reducing the conductance to the nitric oxide molecule; iii) the diffusion of water from the physiological medium into the inner layer under physiological conditions by either facilitating or restricting the water flow (conductance) through the top layer depending on the needs in the given application; and/or iv) the leakage of small molecule by products from said polymer mixture into the physiological medium. To ensure a controllable release of nitric oxide, in one embodiment, the outer layer should be able to restrict the activation, and/or the continuous release, of the nitric oxide release by a factor of about 1 to 20 such as about 1.5 to 10 such as preferably between 2 to 5 compared to the activation of the nitric oxide release from the nitric oxide coating layer itself.

Suitable outer-coatings and methods of manufacture of medical devices coated with out- coats, and the medical devices and uses thereof are disclosed in European application No 06023222 and US provisional application 60/864,893.

The outer layer may also provide structural stability, ensuring the NO adduct and/or coating system remains in place during manufacture, storage, preparation and use of the introducer sheath apparatus.

As described above, the outer coat may consist or comprises of a polymer which has the ability to swell upon insertion into aqueous media. An advantage of using polymers which swell is that the swelling will mask any pin-hole defects or imperfections in the further coats, therefore ensuring the integrity of the coating system when in use.

The ability to swell may be determined by a simple experiment where a known volume of polymer, such as in a granular form, is added to an excess of pure water and allowed to reach an equilibrium in term of water absorption. The swollen granules are then removed from the aqueous media, excess water removed, and the change in volume is assessed. Typically, polymers suitable for use in the outer coat have an ability to swell of at least 1% volume, such as at least 5%, such as at least 10%, such as at least 20%, such as at least 30%, such as at least 40%, such as at least 50%, such as about 60%. Such polymers are referred to as hydroscopic polymers. It will however be recognised that the use of hydroscopic polymers should be used carefully so as to not interfere with the functionality of the medical device or removal of the medical device from the patient.

Whilst disclosures in the prior art refer to the insolubility of LPEI-NONO (see US 6,855,366 for example), we have surprisingly found that (linear) polyethylenimine diazeniumdiolate is soluble in physiological media despite it previously being considered insoluble in aqueous media. It appears that the solubility is due to the presence of ions within the physiological media, which are absent in pure water in which polyethylenimine diazeniumdiolate is insoluble. The use of the coating system and/or outer layer reduces or prevents the inappropriate release of the LPEI-NONO from the coated medical device. In one embodiment, the outer layer comprises a hydrophilic polymer, such as a hydroscopic polymer.

Polymers which may be used in the outer coating may be selected from the group consisting of: polyolefins, such as polystyrene, polypropylene, polyethylene, polytetrafluorethylene, polyvinylidene difluoride, polyvinylchloride, derivatized polyolefins such as polyethylenimine, polyethers, polyesters, polyamides such as nylon, polyurethanes, silicones, or celluloses. More specifically they can be aromatic polyurethanes, ethylene acrylate polyolefins, hydrophilic aliphatic polyurethanes or silicones. In one embodiment, these polymers can be selected from the tecophilic, estanes.

High water vapour conducting polymers, such as EMAC and EBAC polyolefins families or high water vapour conducting silicones may also be used. Water vapour conducting polymers can be identified using the ASTM Method E96B - 50%RH, 23⁰F, preferable water vapour conducting polymers range from moderately breathable, about 350g/m²/24hrs MVT to a highly breathable, about 760g/m²/24hrs HMVT. Such polymers may, in one embodiment also be useful as the hydrophilic polymers for use in the polymer blend/coating systems disclosed herein.

In one preferred embodiment, the outer layer polymer forms a hydroscopic gel upon insertion into physiological media.

It is preferred that the outer coating is selected for its ability to facilitate the insertion and withdrawal of the medical device from the vessel. In this respect hydroscopic or hydrophilic polymers may be preferred in some applications as they form a slippery surface upon insertion into aquatic environments, such as physiological media. It may therefore be preferred that the medical device is contacted with a suitable aqueous solution prior to use, such as isotonic water, for a brief period prior to use, such as for between 1 and 3 minutes.

In one preferred embodiment, the outer layer polymer comprises a hydrophilic polyurethane.

It has surprisingly been discovered that the use of such an outer-layer can control the release of the nitric oxide adduct from said inner layer into the physiological medium. This is particularly of relevance for intravascular medical devices, such as transient intravascular medical devices where the release of the nitric oxide adducts may lead to a low level of undesirable systemic effects, and may therefore also require more stringent regulatory approval process. Hence it is preferred that both the first domain, (and optionally the second and/or third domains and the outer layer are used), as both these can control the undesirable release of the nitric oxide adduct into the physiological media.

The outer layer can also be used to control the rate and timing of the release of nitric oxide from the nitric oxide adduct, such as the coating system as disclosed herein, into the physiological medium. In this respect the outer layer may be only partially or unevenly applied, thereby allowing part of the nitric oxide adduct to rapidly come into contact with physiological media, giving an initial release of NO, whilst the adduct which has an outer coating provides a more sustained release for longer duration.

It is also envisaged that the outer layer can prevent the leakage of small molecules bi- products from said polymer mixture into the physiological medium.

In one embodiment, the outer layer (coat) does not comprise an acidic agent. Such an outer-layer may be used in the coatings of medical devices where a further layer or layers are applied which comprise an agent which modulates the pH as herein referred to (i.e. a pH modifying layer).

The pH of the outer-layer may suitably be about physiological pH, such as between about pH 7 and about pH 8, such as about pH 7.4. The outer layer may comprise a buffer which maintains such a pH, such as a phosphate buffer. By maintaining a pH of about physiological pH the outer-layer can protect the cells which come into contact with the medical device from the pH of the first and/or second domains.

Nitric Oxide Release

One of the dominant processes in the blood vessel is the scavenging of nitric oxide by haemoglobin. Most nitric oxide combines with oxyhaemoglobin in a 60-100% oxygen saturated environment to form methaemoglobin and subsequently nitrate. In low oxygen saturated environment, nitric oxide combines with deoxyhaemoglobin to form nitrosylhaemoglobin, which in the presence of oxygen forms nitrogen oxides and methaemoglobin. The end products of nitric oxide that enter the systemic circulation are methaemoglobin and subsequently nitrate. The nitrate is then transferred to the serum, and the greater part of the nitrate is excreted into the urine through the kidney.

The typical half life of nitric oxide in blood is milliseconds. The half-life of nitric oxide is several hundred times longer in tissue than in blood. The biological half-life of haemoglobin- bound nitric oxide is about 15 min. Physiological concentration range of nitric oxide activity

The concentration in the smooth muscle cells resulting in relaxation is, based on the literature findings, expected to be larger than 200 nM but significantly below 1 mM. The lower limit (200 nM) is determined by the concentration required to activate soluble guanylyl cyclase, which acts as the enzyme that generates the second messenger cyclic GMP resulting in smooth muscles relaxation. The upper limit (1 mM) is determined by the concentration leading to significant oxidative stress and mutations.

For comparison the physiological level of nitric oxide concentration in tissue stated in the literature ranges form 100 to 500 nM. The physiological concentration in healthy endothelial cell is about 100 μM.

Dose - nitric oxide release

According to Vaughn et al., Am J Physiol. 1998 Jun;274(6 Pt 2), 0.32 nmol/min/cm² is one of the highest reported release rates from the natural endothelium. In order to obtain the desired biological response values higher may therefore required. For example, considering the short contact with the vessel wall and the thickness of tissue that the nitric oxide needs to pass before reaching the media of the vessel the desired release rate should preferably be higher to obtain the optimal vasorelaxing response.

To support the determination of an appropriate release rate ex-vivo studies on human as well as rat arteries were carried out. The aim of the study was to investigate the effect of nitric oxide released from test tubes coated with the nitric oxide eluting polymer. It was shown that the nitric oxide eluting polymer induced forceful relaxation of the arteries. The applied release rates were in the magnitude of 0.5 and up to 3 nmol/min/cm². Testing has been performed in PBS as well as in blood.

According to the literature findings there is about a factor of 5000 between the concentration required to activate soluble guanylyl cyclase (200 nM) and the concentration level leading to significant oxidative stress and mutations (1 mM).

The effective device release rate has according to the preclinical studies and literature findings a broad range. To minimize the risk of toxicity the upper limit is preferably set to 40 nmol/min/cm². The lower limit is preferably set to 0.5 nmol/min/cm². Lower release rates than 0.5 nmol/min/cm², possibly even as low as 0.2 nmol/min/cm² probably also induce relaxation, however they may be less effective. Suitably the (maximum) rate of NO release from the medical device according to the invention may be greater than about 0.1 nmol/min/cm², such as greater thanθ.25 nmol/min/cm², preferably greater than about 0.32 nmol/min/ cm², such as greater than 0.5 nmol/min/cm², such as greater than lnmol/min/ cm².

Suitably the maximum rate of NO release from the medical device according to the invention is no more than about 40 nmol/min/cm², such as no greater than about 60 nmol/min/cm², such as no greater than about 80 nmol/min/cm².

In one embodiment, (maximum) release rate from the medical device according to the invention is between about 0.5 and up to about 3 nmol/min/cm².

When a topcoat (outer layer/coating) is applied, typically the release of nitric oxide deviates significantly from a l'order release. This is due to the barrier properties of the topcoat: limiting the water absorption and the diffusion of nitric oxide through the coating.

Preferably, the peak release of nitric oxide, and/or the release after 5 minutes after insertion into an isotonic solution, from the outer surface of the medical device is between about 0.5 and about 40 nmol/min/cm²,as measured by using a dynamic headspace chamber connected to a chemoluminescence NO detector: The object coated with the described nitric oxide releasing coating system is placed in a head space chamber containing pbs buffer (pH7.4) with 0.00004% Tween 20, kept at 37°C. The solution is continuously flushed with 250 mL N₂ gas ensuring oxygen free conditions. The nitric oxide released from the coat into the oxygen free environment is striped off from the solution and carried to the chemoluminescence NO detector by the NO gas. The examples provide a NO assay which is used to determine the release rate of nitric oxide.

In one embodiment the peak release rate is obtained within the first 10 minutes after wetting or inserting the device, such as within the first five minutes, such as within the first three minutes after wetting or inserting the device.

In order to determine whether a potential nitric oxide adduct is capable of releasing nitiric oxide 'under physiological conditions' as used herein, the assay as described above may be used.

Preferably, the release of nitric oxide from the outer surface of the medical device has a half life in physiological media of at least 30 minutes, such as at least 60 minutes, such as at least 90 minutes or at least 2 hours such as at least 4 hours, at least 6 hours or at least 12 hours. In one embodiment the maximum rate of decrease of NO release after the point of maximum rate of NO release has been obtained is less than about -0.015 nmol/min/min, such as less than about -0.03nmol/min/min, such as less than about -0.06 nmol/min/min.

Further Therapeutic Agents

The medical device may be capable of releasing one or more further therapeutic agents. These further therapeutic agents may be provided in the first, second and/or third domains, and or the outer-coating. Alternatively the therapeutic device may provide other means for delivery of the further therapeutic agents. Like the release of NO from polyethylenimine diazeniumdiolate, the release of the further therapeutic agents may also be pH dependant, and as such the acidification of the first domain may cause the release of the therapeutic agent, or the alkalinisation of the second or third domain or outer-layer from the alkali first domain, may trigger the release of the further therapeutic agents.

In addition to (or in one embodiment as an alternative to) the polyethylenimine diazeniumdiolate, the medical device may be coated in one or more further therapeutic agents, such as a human growth factor, an anti coagulant, such as heparin, an antibiotic agent, such as an antibiotic, a chemotherapeutical agent, a further smooth muscle cell proliferation reducing agents, such as nitric oxide (NO) or a nitric oxide donor, and/or a vasodilation agents, such as NO or an NO donor. Ascorbic acid (vitamin C) may be provided as an antioxidant or as a catalyst for release of nitric oxide (I.e. within the second domain). In one embodiment, in case the release rate of the further therapeutic agent is not per se dependent on pH, the therapeutic agent may be bonded to or encapsulated in a carrier compound, which is characterised by a pH-dependent release rate or a pH-dependent degradation rate of a carrier material encapsulating the therapeutic agent.

The further therapeutic agent may be immobilised in a hydrogel, e.g. a hydrogel. Certain hydrogels swell under acidic conditions. One possible way to produce such a hydrogel which swells in blood but not in pure water is to co-deposit the therapeutic agent with glucoseoxidase (GOD). When glucose diffuses into the hydrogel from the blood, GOD will transform the glucose to cluconic acid and hydrogen peroxide.

The further therapeutic agent may e.g. comprise at least one of: heparin or another thrombin inhibitor, hirudin, hirulog, argatroban, D-phenylalanyl-L-poly-L-arginyl chloromethyl ketone or another antithrombogenic agent, or mixtures thereof; streptokinase, urokinase, a tissue plasminogen activator, or another thrombolytic agent, or mixtures thereof; paclitaxel; estrogen or estrogen derivatives; a fibrinolytic agent; a vasospasm inhibitor; a calcium channel blocker, a nitrate, nitrite, nitric oxide, a nitric oxide promoter, such as ascorbic acid, or another vasodilator; an antimicrobial agent or antibiotic; aspirin, ticlopdine or another antiplatelet agent; colchicine or another antimitotic, or another microtubule inhibitor; cytochalasin or another actin inhibitor; a remodelling inhibitor; GPIIb/Illa, GPIb-IX or another inhibitor or surface glycoprotein receptor; deoxyribonucleic acid, an antisense nucleotide or another agent for molecular genetic intervention; methotrexate or another antimetabolite or antiproliferative agent; an anti-cancer chemotherapeutic agent; dexamethasone, dexamethasone sodium phosphate, dexamethasone acetate or another dexamethasone derivative, or another anti-inflammatory steroid; dopamine, bromocriptine mesylate, pergolide mesylate or another dopamine agonist; ⁶⁰Co (having a half life of 5.3 years), ¹⁹²Ir (half life of 73.8 days), ³²P (half life of 14.3 days), ¹¹¹In (68 hours), ⁹⁰Y (64 hours), ^99mTc (6 hours) or another radiotherapeutic agent; iodine-containing compounds, barium-containing compounds, gold, tantalum, platinum, tungsten or another heavy metal functioning as a radiopaque agent; a peptide, a protein, an enzyme, anextracellular matrix component, a cellular component or anotherbiologic agent ; captopril, enalapril or another angiotensin converting enzyme (ACE) inhibitor; ascorbic acid, alphatocopherol, superoxide dismutase, deferoxyamine, a 21-aminosteroid (lasaroid) or another free radical scavenger, iron chelator or antioxidant; angiopeptin; a ¹⁴C-, ³H-, ¹³¹I-, ³²P or ³⁶S-radiolabelled form or other radiolabeled form of any of the foregoing. Mixtures of any of these are also envisaged.

It is recognised that one or more of the therapeutic agents listed above, may in one embodiment, be used either in the absence of (L)PEI-NONO, or in addition to (L)PEI-NONO. They may be present in the first domain, second domain, third domain or outer coat and/or further layers as referred to herein.

The Medical Device

In one embodiment, the medical device is an intravascular medical device or a neurovascular medical device.

In one embodiment the medical device is a transient medical device which does not remain within the patient after the surgical procedure has been completed, such as an introducer sheath or assembly and components thereof, a catheter such as a coronary guiding catheter or a neuro catheter, a guide wire, a syringe needle/trocar, an angioplasty balloon, a coronary wire.

The medical device may be disposable.

The medical device may comprise an intermittent or permanent intravascular implant. The medical device may be selected from the group consisting of: Neuro medical devices, such as neuro guiding catheter, neuro microcatheter, neuro microwire, neurostent delivery system, neuron balloon; coronary medical devices, such as coronary wires, coronary guiding catheter, PTCA angioplasty balloon; stent delivery system, coronary wires, coronary guiding catheter, PTA angioplasty balloon; introducer sheath, dilator, guide wire, syringe needle /trocar, introducer sheath assembly, dialysis sheath.

The medical device may for instance include an intermittent or permanent intravascular implant, such as a stent, a stent graft, a balloon, a catheter, a guiding catheter, a guidewire, an embolization device, such as wire or a coil.

In case of a balloon, the device may e.g. include an expandable coated angioplasty balloon, such as a PTA (percutaneous translumenal angioplasty) balloon, a PTCA (percutaneous translumenal coronar angioplasty) balloon or a PTNA (percutaneous translumenal neurovascular angioplasty) balloon.

In one embodiment the medical device is an implant such as a stent.

In one embodiment the medical device is a prosthetic, such as a breast implant or a penis implant.

In one embodiment the medical device may be applicable in intravascular surgery and may include, e.g., a balloon, a balloon catheteter, a catheter, a stent, a stent graft or a guidewire.

In one embodiment, the medical device is not made from polytetrafluoroethylene (PTFE) (Teflon™) or Fluorinated polyethylene (FEP). There are two benefits in selecting an alternative substrate for manufacture of the base material of the medical device, firstly, it allows for the routine use of radiation based sterilisation techniques, and secondly it facilitates the coating of the medical device.

Therefore, preferably the medical device, such as the introducer sheath (or dialysis sheath) is manufactured from a material which is capable of being sterilised using radiation based techniques, such as gamma radiation or e-beam. Nylon is a suitable based material. Other suitable materials may be selected from the group consisting of, for example, polyurethanes, aromatic polyesters, polycarbonates, polyethylenes, polystyrenes, and polysulfones.

The medical device may be made from a base material which is high density polyethylene. The medical device may for instance include an intermittent or permanent intravascular implant, such as a stent, a stent graft, a balloon, a catheter, a guiding catheter, a guidewire, an embolization device, such as wire or a coil. In case of a balloon, the device may e.g. include an expandable coated angioplasty balloon, such as a PTA (percutaneous translumenal angioplasty) balloon, a PTCA (percutaneous translumenal coronar angioplasty) balloon or a PTNA (percutaneous translumenal neurovascular angioplasty) balloon.

In one embodiment, the medical device is an introducer sheath, such as the introducer sheaths and components thereof referred to in European application No. EP06023203 and US provisional application 60/864,879.

Introducer Sheath

The nitric oxide eluting medical device according to the present invention may be an introducer sheath, or introducer sheath assembly (kit of parts). The kit of parts comprises at least two key components: the introducer sheath including a dilator and the nitric oxide eluting coating applied on at least the distal portion of the sheath. The primary mode of action of this device is identical to that of the traditional introducer sheath: for use for the intravascular introduction of interventional and/or diagnostic devices. The ancillary action of the nitric oxide elution is to prevent vessel spasm and occlusion during the introduction of interventional and/or diagnostic devices through the introducer sheath. It is envisaged that the use of the introducer sheath of the present invention will also reduce the likelihood of blood clot formation, thrombosis and related disorders.

A preferred device is an introducer sheath coated with a nitric oxide eluting coating applied on at least the distal 10 cm of the sheath.

In one embodiment the proximal lcm of the introducer sheath is not coated.

The device is indented for radial intravascular introduction of interventional/diagnostic devices and the primary mode of action of this device is identical to that of the traditional introducer sheath.

The ancillary action of the medical device is nitric oxide elution to enhance the clinical safety during the procedure, such as decreasing the risk of vasospasm or thrombosis.

The term an 'introducer sheath' as used herein is a device which is used to introduce medical devices into the human body, such as the vascular or neurovascular system. It comprises a hollow tube, typically made of a flexible material through which other medical devices are introduced into the vascular or neurovascular system. Introducer sheaths are often coated with a lubricating surface or made from a lubricating material, such as Teflon™. The proximal end of the introducer sheath is exterior to the body, whilst the majority of the length of the introducer sheath is within the lumen of a vessel of the vascular system. The introducer sheath typically has a length of about 10 to about 30 cm in length and a diameter of 5 or 6 french. French are units which correspond to the internal diameter of the introducer sheath, and the external diameter of subsequent medical devices inserted into introducer sheath, such as catheters. 1 French is l/3^rd of a millimetre. Although wall thicknesses of the introducer sheath may vary, it is preferable to have as thin a wall as possible, whilst retaining the structural robustness of the introducer sheath.

Typically, the insertion of the introducer sheath involves a first act of making an incision into the human body using a hollow needle (a trocar) into an arterial wall (venepuncture). Subsequently a soft tipped guide wire is passed through the needle and the needle removed. An introducer sheath, comprising the dilator within is then passed over the guide wire. The dilator is removed and the medical device, typically comprising a catheter is passed over wire and wire is removed.

Preferably, the external surface of the proximal end of the introducer sheath is not coated with said nitric oxide adduct. This is because this is the region which comes into more that momentary contact with the site of injury into the vessel (insertion site), where a local vasospasm is may be desirable, both in ensuring a tight connection with the introducer sheath, thereby preventing leakage of the physiological media from the insertion site into the surrounding tissues and external to the body, and also facilitates quicker healing after removal of the introducer sheath as the blood clots at the insertion site.

Therefore, preferably, the region of the external surface of the proximal end of the introducer sheath not coated is sufficient to reduce bleeding from the entry point into the vascular or neurovascular system, as compared to an equivalent proximally coated sheath.

Typically the introducer sheath has a length of between 10 and 30cm.

Typically, the introducer heath has an inner diameter of between 4 and 12 French. Other sizes may be appropriate depending on the size of the patient (and their arteries), and the size of the medical device to be inserted via the introducer sheath. For example, the diameter may be between 4 and 7 French, such as between 5 - 6 French, may for example be used for radial arteries. 4 French introducer sheaths may be suitable for use in small children. 8 or 9 French may be used for larger equipment to be entered via the femoral artery, and even up to 12 to 14 French for devices such as aortic stents. However, typically 5 to 6 French is sufficient for normal cardiac procedures. In on embodiment the introducer sheath is a dialysis sheath. Such dialysis sheaths are particularly useful as the release of NO reduces the vasospasm associated with repeated insertion and removal of sheaths for routine dialysis. In some patients vasospasm is such a problem that all suitable venal entry sites become unusable, and as such the life of the dialysis patient can be threatened.

Kit of Parts

Introducer sheaths are typically manufactured as kits of parts, which in addition to the introducer sheath comprises a dilator.

The term 'dilator' as used herein, is a device which is inserted into the introducer sheath, which ensures the structural robustness of the introducer sheath upon insertion into the vascular system, and are removed prior to insertion of the medical device to be inserted to the introducer sheath. The dilator has an outer diameter allowing a close fit with the introducer sheath, whilst not impeding its removal. The dilator also has an immer diameter, through which the guide wire passes upon insertion into the patient. Dilators are also made from a flexible material, and when fully inserted into the introducer sheath they typically extends beyond the distal tip of the introducer sheath, and typically comprises a tapered end which facilitates insertion of the introducer sheath/dilator into the vessel. The dilator also may comprise a distal region of radio opaque material which, using X ray images, is used to locate the end of the introducer sheath assembly to ensure correct insertion.

The term 'guide wire for an introducer sheath' is specific term describing the guide wire which is used for guiding the insertion of the introducer sheath into the blood vessel. Preferably, the guide wire ranges from about 0.018 to about 0.038" (about 0.4572 to about 0.9652mm) in diameter and about 35 to about 80cm in length. Unlike guide wires for catheters, the guide wire for an introducer sheath does not reach the site of intervention, indeed, in one embodiment it is not necessary for the guide wire to extend beyond the distal tip of the introducer sheath or dilator.

The term ^λAn introducer sheath assembly' refer to a kit of parts which comprises an introducer sheath and at least one other medical device which is used during the insertion of the introducer sheath into the vascular system, for example by the Seldinger technique. The Introducer sheath assembly may also comprise, in its proximal end, which is not inserted into the body, a valve to facilitate the introduction of further medical devices, such as catheters. The introducer sheath may also comprise a valve to allow insertion of fluid administration such as therapeutic agents. A suture ring on the valve housing may provide secure anchoring of the sheath. An introducer sheath assembly suitable for coating with the compound capable of releasing nitric oxide under physiological conditions is disclosed in US 5,409,463. Suitable introducer sheaths for coating using the method of the invention are available from Thomas Medical Products Inc., Malvern, Pennsylvania, and may be prepared by e.g. spray coating, such as coating with the coating system and/or coating with nanofibres, such as by electrospinning (US 6,382,526, US 6,520,425).

In one embodiment, the kit of parts comprises a dilator according to the invention wherein said dilator is capable of being inserted into an introducer sheath, such as the introducer sheath according to the invention, or an introducer sheath that is not coated with an nitiric oxide adduct. The dilator may also, preferably, be capable of being inserted over an introducer sheath guide wire, such as the introducer sheath guide wire according to the invention.

Preferably, when the dilator is fully inserted into said introducer sheath, it extends beyond the distal tip of said introducer sheath, and the region of the dilator which extends beyond the distal tip of said introducer sheath comprises a tapered end which is coated with said compound capable or releasing nitric oxide under physiological conditions.

In one embodiment, the region of said dilator which does not extend beyond the distal end of the introducer sheath when fully inserted is not coated with said compound capable or releasing nitric oxide under physiological conditions.

The kit of parts may also comprise an introducer sheath guide wire which is optionally coated in a nitric oxide adduct which is capable of releasing nitric oxide under physiological conditions, such as the nitric oxide adducts and/or coating systems as referred to herein.

The trocar needle used for making the initial insertion may also be coated with a nitric oxide adduct. The trocar is hollow to allow passage of the guide wire through into the lumen of the vessel. Whilst it is considered beneficial that the distal portion of the trocar is coated in the nitric oxide adduct and/or coating systems as referred to herein, in one embodiment, the proximal end of the trocar, i.e. the portion which after insertion into the patent, is in contact with the wound site, is not coated with the nitric oxide adduct or coating system as referred to herein.

Coating Systems

In a preferred aspect the first domain, second domain, third domain and/or outer-coating are in the form of a coating applied to at least part of the external surface of the medical device according to the invention. Suitable coating systems, for use in each of the first, second and/or third domains, are described in European Application No 06023223 and US provisional application 60/864,886.

In a preferable embodiment, the medical device according to the invention comprises first domain comprising a nitric oxide adduct in the form of a coating system comprising a polymer mixture, wherein said polymer mixture comprises said nitric oxide adduct and a hydrophilic supporting polymer or polymer blend, and wherein the said nitric oxide adduct and the supporting polymer or polymer blend form a homogeneous phase.

The coating system preferably comprises an antioxidant, such as a sterically hindered phenolic antioxidant (eg. Octadecyl-3-(3,5-di-tert.butyl-4-hydroxyphenyl)~propionate, tradename Irganox 1076, Ciba specialty chemicals), such as between about 0.01 and 1%; such as between about 0. 1% and 0.5% (w/w). The use of such an antioxidant increases stability during radiation sterilization and improves the shelf life of the medical device.

The term 'hydrophilic' refers to a substance which has a higher solubility in water than in oil or other hydrophobic solvents. Hydrophilic molecules are capable of forming hydrogen bonds, which makes then soluble not only in water but other polar solvents.

It has surprisingly been discovered that the use of such a polymer mixture can control the release of the nitric oxide adduct from said inner layer into the physiological medium. By adjusting the ratio between the nitric oxide releasing adduct and the additional polymer blend the embodiment of the nitric oxide releasing adduct will be improved to minimize the release of the nitric oxide releasing adduct into the surrounding environment. This is particularly of relevance for the medical devices, such as transient medical devices, where the release of the nitric oxide adducts may lead to a low level of undesirable systemic effects, and may therefore also require more stringent regulatory approval process. It is also envisaged that the use of the polymer matrix can prevent the leakage of small molecule by-products from said polymer mixture into the physiological medium.

The use of the polymer mixture is also key in controlling the rate and timing of the release of nitric oxide from said inner layer into the physiological medium. This is controlled by adjusting the polymer or polymer blend to balance the level of support compared to hydrophilic characteristics, thereby creating the desired structure which can provide the controlled diffusion of water from the physiological medium into the inner layer under physiological conditions to release the nitric oxide. Parameters important for the nitric oxide releasing adduct are, as mentioned above, good stability, a fast activation of the nitric oxide release, a continuous release within physiological relevant concentration and ensuring no, or minimal, release of the nitric oxide releasing polymer into the external environment.

To ensure good stability, the polymer mixture, polymer blend, coating system and/or single polymer should withstand a traction force applied to the surface of the polymer coat of about 4 to 100 newton cm^"2 such as about 8 to 50 newton cm^"2 such as preferably between 10 to 20 Newton cm^"2.

To ensure a rapid activation of the nitric oxide release, the polymer mixture should show a good water conductance performance. In one embodiment, this parameter can be measured by determining the release rate of nitric oxide from a NO adduct coated with the polymer and a suitable nitric oxide adduct. This may be achieved by supplying a polymer with high water conductance and a high water conductance/swelling ratio to the nitric oxide releasing polymer layer. The polymer mixture, polymer blend, coating system, and/or hydrophilic polymer should allow water transport into the NO adduct layer rapidly enough to induce a increase in nitric oxide release of about 0.05 to about 50 nmol cm^"2 min^"1 per minute such as about 0.25 to about 20 nmol cm^"2 min^"1 per minute such as preferably between 0,5 to about 10 nmol cm^"2 min^"1 per minute when measured at the maximum rate of increase of NO release (see Figure 6). This may be determined by preparing a 30% LPEI-NONO, 70% hydrophilic polymer (or polymer mixture or polymer blend), on an inert base material such as nylon, and measuring the rate of release of NO over time when inserted into phosphate buffered saline, pH 7.4, 37°C. Suitably the nitric oxide adduct used to determine the NO release may be the LPEI-NONO as prepared in the example 1

In one embodiment, the ratio of polymer mixture to said nitric oxide adduct present in the coating system is between about 5/95 to about 95/5, such as between 40/60 and 90/10, preferably between about 50/50 and about 80/20, such as about 70/30, as measured weight/weight).

In one embodiment, the NO donor itself may be form the hydrophilic or support polymer, or polymer blend, and as such the NO adduct is suitable for use as a coating system per se. In such an embodiment, the coating system may comprise up to 100% of the NO adduct.

In one preferred embodiment, the polymer blend comprises a mixture of a support polymer and a hydrophilic polymer. The hydrophilic polymer may be selected from the group consisting of: polyolefins, such as polystyrene, polypropylene, polyethylene, polytetrafluorethylene, polyvinylidene difluoride, polyvinylchloride, derivatized polyolefins such as polyethylenimine, polyethers, polyesters, poiyamides such as nylon, polyurethanes, silicones.

More specifically they may be selected from the group consisting of: aromatic polyurethanes, ethylene acrylate polyolefins, hydrophilic aliphatic polyurethanes or silicones, all with a high ratio of water conductance towards water absorbance. These polymers can be selected from the tecophilic, estane, EMAC and EBAC polyolefins families or high water vapour conducting silicones.

The support polymer may be selected from the group consisiting of: polyolefins, such as polystyrene, polypropylene, polyethylene, polytetrafluorethylene, polyvinylidene difluoride, polyvinylchloride, derivatized polyolefins such as polyethylenimine, polyethers, polyesters, poiyamides such as nylon, polyurethanes with good adhesion and structural stability, fulfilling the stability criteria stated above. However, it could preferably be an aliphatic polyether- based polyurethane such as eg. Tecoflex SG 85A.

In one embodiment, the ratio of support polymer to hydrophilic polymer used in the coating system can be between about 95/5 to about 35/65. by weight depending on the characteristics of the polymers used. In one system, using an aliphatic polyether-based polyurethane together with an aromatic polyurethane, the ratio can vary from about 90/10 to about 50/50 by weight.

In one embodiment the ration of support to hydrophilic polymer used in the coating system is about 70/30 by weight.

The ratio of support polymer to hydrophilic polymer is a ration which excludes the NO adduct, which is also present in the coating system.

It is envisaged that in one embodiment the NO adduct may itself be part of either of the hydrophilic and/or supporting polymer. However, in a preferred embodiment, the NO adduct is not the supporting polymer or hydrophilic polymer referred to in the coating system, although may comprise support and/or hydrophilic properties. Suitable methods for the preparation of hydrophilic and/or supporting polymer nitric oxide adducts are disclosed in US 5,405,919 or other references referring to synthesis of NO polymers, such as those referred to herein. In one embodiment, the thickness of the coating system is between about 1 to about 100 μm, such as between 5 and about 20 μm in dry state.

In one aspect, the coating or coating system (e.g. comprising the nitric oxide adduct - first domain), is applied to the exterior surface of said medical device by one or more of the following methods: spray coating, painting, dipping, and extrusion.The second domain may comprise an acidic agent or acidic side group in the form of a coating system comprising a polymer mixture, wherein said polymer mixture comprises and acidic agent, such as a compound or acidic group, and a hydrophilic supporting polymer or polymer blend, and wherein the said acidic agent and the supporting polymer or polymer blend form a homogeneous phase. It is recognised that the polymers used in the coating system may be naturally acidic, or modified to comprise acidic side groups.The coating system use in the first domain may comprise polymers which are naturally alkali or have been modified to comprise alkali side groups.

The third domain may comprise a coating system comprising a polymer mixture, wherein said polymer mixture comprises a hydrophilic supporting polymer or polymer blend which form a homogeneous phase.

Fibres

In one embodiment the coating comprising the nitric oxide adduct is applied to the exterior surface of said medical device in the form of fibres such as nanofibres, such as electrospun nanofibres (such as the polyethylenimine diazeniumdiolate nanofibres disclosed in US 6,382,526, US 6,520,425).

It is envisaged that such fibres/nanofibres may also be encased in the polymer system as described herein. The fibres/nanofibres may be applied directly to the surface of the medical device or a primer layer as described herein. The fibres/nanofibres may be further coated with an outer layer as herein described.

However, in one embodiment the nitric oxide adduct is applied to the area of the medical device to be coated as a uniform layer, such as in the form of a coating system as described herein.

In one embodiment in the form of a fibre or a nano-fibre or an electrospun nanofibre, or electrospun fibre.

Methods of Manufacture It is envisaged that medical device according to the invention may be made from or comprise a base material which comprises the nitric oxide adduct. In this instance the first domain forms at least part of the base material of the medical device.

However, in a preferred embodiment, the medical device is pre-manufactured, and the subsequently coated with the NO adduct - such as by application of at least the first domain.

In order to ensure a specific target release resulting in the desired clinical impact (optimal target release is in the range from about 0.5 nmol/min/cm² to about about 40 nmol/min/cm²), the nitric oxide donor is incorporated into a polymeric matrix, such as the coating system as referred to herein.

In a preferred embodiment, the coating consists of 3 layers: (i) an optional primer layer, which ensures and optimizes coating adherence to the device, (ii) The nitric oxide donating layer (first domain), which may for example be a mixture of polyurethanes or other polymers referred to herein (see under coating system) and L-PEI-NONO (LPN)(which, may for example be suitably dissolved in an alkali organic solvent, such as pyridine or pH adjusted methanol (prepared for example by addition of a suitable alkali, such as NaOH) for spray application onto the medical device). The recipe for the nitric oxide (e.g. LPN) donating layer may include a pH adjusted solvent (e.g. an alkali organic solvent such as an alcohol such as methanol, or pyridine) to ensure that the nitric oxide (e.g. LPN) is stable during processing. The alkali agent is preferably retained in the first domain to ensure that the pH of the first domain remains above 7(Ni) an optional topcoat (Outer layer/coat), which serves to ensure coating integrity, appropriate rate of water absorption and appropriate rate of NO diffusion (and prevents systemic release of LPEI-NONO).

The pH of the first domain may also be controlled by ensuring the coating is performed in a confined environment comprising a suitable alkali agent, typically an (alkali) gas, such as ammonia. For the addition of the second domain, when appropriate, the medical device is then, typically transferred to a neutral environment.

Coats (i) and (iii) may be optional, but are preferred. Typically the method for preparing a coated medical device according to the invention consists of a first optional step of applying the priming layer (i), a second step of applying the nitric oxide adduct layer (first domain) (ii), and a third optional step of applying the top coat (iii). Further coatings, such as the second domain and third domains as referred to herein, may be applied either before during or subsequent to the application of the nitric oxide adduct layer (first domain). When a topcoat (Outer coat) is applied, the release of nitric oxide typically deviates significantly from a l'order release. This is due to the barrier properties of the topcoat: limiting the water absorption and the diffusion of nitric oxide through the coating leading to a more constant release over time.

Prior to application of the NO adduct coating (first domain), a priming layer, as herein described, may be applied. The priming layer may be applied by any suitable means, such as dipping, spaying coating, or extrusion.

During manufacture of the device, the layers (domains) may e.g. be formed by dip-coating, spraying, painting, printing, vapour deposition, extrusion or a combination thereof. In one embodiment the layers are not formed by electro spinning techniques. Spray coating has been found to be a highly convenient way of applying the domains and layers to medical devices.

The inner layer(s) may be textured e.g. by sanding prior to application of the outer layer, so as to obtain a textured or roughened outer surface of the inner layer providing improved bonding of the outer layer.

The NO adduct (first domain) is suitably applied either directly to the base material of the medical device, or to the primer layer or a further layer, such as the second or third domains. The NO adduct (first domain) itself may be applied, for example, in one embodiment LPEI- NONO nanofibres may be applied. Alternatively a coating system comprising (L)PEI-NONO as herein described may be employed.

The coating system may comprise a polymer mixture applied to said external surface of the medical device, wherein said polymer mixture comprises at said at least one nitric oxide adduct and a hydrophilic supporting polymer or polymer blend, and wherein the nitric oxide adduct and the supporting polymer or polymer blend form a homogeneous phase.

Further layers may then be applied over the coating system layer. For example a second domain of a material which is capable of affecting the pH of the first domain upon insertion into physiological media may be applied (i.e. the second domain).

pH modifying layer(s) typically include a pH modifying agent, which in a broad embodiment may include any atom, molecule or ion, including H⁺ and OH^", capable of affecting pH by shifting the local balance between H⁺ and OH^" ions. A change in pH may arise due to direct increase or decrease of H⁺ or OH^" ions by means of ingress of acid or base, or due to ingress of molecules or ions that trigger chemical reactions that confer a change of pH. The NO release from NO adducts is typically sensitive to pH, with release of NO being favoured in acidic conditions. Therefore the use of a further layer which is capable of shifting the local balance between H⁺ and OH^" ions upon wetting (e.g. in physiological media) allows the release rate of NO from the nitric oxide adduct to be controlled. The second domain may therefore comprise, for example an acidic agent or acidic side groups, such as an acid selected from ascorbic acid, polyacrylic acid, oxylic acid, acetic acid and lactic acid. The acid may be incorporated into a polyurethane polymer for application.

In a preferred embodiment, an outer coating as herein described is also applied. The outer coating may be applied directly to the coating system layer, or to one or more further layers applied to the coating system layer.

If premature release of the therapeutic agent is to be avoided, the donor-compound containing coating is preferably applied under conditions that are unfavourable for release, e.g. conditions of low temperature, low pressure, lower water content or low humidity. In particular, premature release of the therapeutic agent is achieved by deposition of the donor- compound, i.e. therapeutic agent, under pH conditions which inhibit release of the therapeutic agent - suitably under alkaline conditions of pH greater than 7.

Thus, the method of manufacture according to the invention preferably takes place at a relative humidity of at most 40%, such as at most 30%, such as at most 25%, such as at most 20%, such as at most 15% or 10%. Likewise, in the product of the second aspect of the invention, a relative humidity of at most 40% may be maintained in the package, such as at most 30%, such as at most 25%, such as at most 20%, such as at most 15% or 10%. Similarly, to prevent premature release of the therapeutic agent, the medical device may be manufactured and stored at a pH inhibiting such release, e.g. at a pH of at least 7, such as at least 8, 9, 10, 11, 12, 13 or 14. Combinations of humidity and pH and optionally other parameters may be applied to further inhibit premature release of the therapeutic agent.

The medical device is then packaged, and sterilised.

As NO release from NO adducts is sensitive to moisture, it is preferable that the packaging is performed in a confined environment where the relative humidity does not exceed about 40%, such as does not exceed about 30%, such as does not exceed about 20% or about 10%. In one embodiment the relative humidity (at room temperature) is less than about

1%, or substantially free of water (i.e. less than 0.1% water). In one embodiment the O₂(g) is less than about 0.1%, or substantially free of O₂(g) (i.e. less than 0.1% water). Preferably, the medical device or kit of parts is packaged in a sealed pouch, such as an aluminium sealed pouch with N₂ atmosphere. The packaging should preferably prevent moisture, oxygen and light from entering the package,

It is highly advantageous to include an oxygen and/or water absorber into the inside of the packaging material to ensure low oxygen and water environment within the packaging - this not only extends the shelf life of the sealed products, but also protects the top coat during sterilisation. Suitably, levels of gaseous water and molecular oxygen as low as 0.01% within the packaging can be obtained (www.mgc-a.com).

In one embodiment, the sterilisation is performed using radiation sterilisation, such as e- beam of gamma radiation.

In one embodiment, the method of manufacture involves coating the entire external surface of the medical device. However, as described herein, typically it advantageous to coat only part of the medical device - i.e. the parts which are likely to come into contact with the cells in need of receiving NO.

During manufacture of the device, the layers may e.g. be formed by dip-coating, electro- spinning, gas-assisted electrospinning, spraying, painting, printing, vapor deposition or a combination thereof. The inner layer may be braided prior to application of the outer layer, so as to obtain a textured or roughened outer surface of the inner layer providing improved bonding of the outer layer.

The first domain may comprise at least one polymer and at least one donor compound, the donor compound being capable of releasing a therapeutic agent and having the characteristic that the rate of release is correlated to the pH in the domain.

The therapeutic agent may either be present as discrete molecules within the polymer, or it may be bound to the polymer(s) of the first domain either by covalent bonds, by ionic interactions, by hydrogen bonds or by hydrophobic interactions. In the latter of the two instances, the therapeutic agent typically needs to be liberated from the polymer molecules before its biological effect can enter into effect. In the former of the two instances, the polymer may itself serve as donor compound. Liberation will often take place upon wetting of the second domain, Le by contact with physiological fluids (e.g. blood) to result in a transfer of H⁺ ions to the first domain to liberate the therapeutic agent.

Upon wetting of the first and/or second domain, the second domain may obtain a pH different from the pH of the first domain such that inter-diffusion between the first and the second domain affects the pH in the first domain and hence affects the release of therapeutic agent. Depending on the exact nature of the bioactive and pH active domains different mechanisms may result in release of therapeutic agent.

A first mechanism is that a pH modifying compound diffuses away from the bioactive domain into the pH active domain, thus depleting the bioactive domain from the pH modifying compound.

A second mechanism is that the pH modifying compound diffuses from the pH active domain to the bioactive domain, thus affecting the pH in the bioactive domain.

A third mechanism is that the donor compound diffuses from the bioactive domain to the pH active domain. By entering the pH active domain the pH shifts, thus trigging the release of therapeutic agent from the donor compound.

The pH modifying agent may include any atom, molecule or ion, including H⁺ and OH^", capable of affecting pH by shifting the local balance between H⁺ and OH^" ions. A change in pH may arise due to direct increase or decrease of H⁺ or OH^" ions by means of ingress of acid or base, or due to ingress of molecules or ions that trigger chemical reactions that confer a change of pH.

In embodiments of the invention, in which the first and second domains are provided as superposed coating layers, the medical device may further comprising a third coating layer forming an outer surface layer of the medical device, e.g. to protect the first and/or second domain from damage or to delay ingress of blood or other body fluids and/or to control the release rate of the therapeutic agent from the first layer (first domain) to surrounding tissue. Transport of H⁺ or OH^" ions between the first and second domains may delayed by a fourth coating layer provided between the first and the second coating layers, i.e. the layers of the first and second domains. The fourth layer may prevent or reduce unintended diffusion between the first and second domains during storage of the device, i.e. unintended diffusion at low humidity of the surrounding environment. At least one of the first, second third and fourth coating layers may comprise polyurethane. Thanks to the provision of the outer surface layer, i.e. the third coating layer, mechanical integrity and strength of the device may be improved, adhesion between surface portions of e.g. a coated balloon may be avoided, and low surface friction may be achieved.

Method of Treatment

The medical devices/kits of parts according to the invention may be used for performing intravascular or neurovascular surgery, such as vascular intervention(s). The invention therefore provides for a method of releasing nitric oxide from a medical device, the medical device including at least a first and a second domain as according to any one of the preceding claims, the method comprising the steps of:

- placing the medical device in contact with a bodily fluid of a living being; - wetting the medical device to thereby cause transport of H⁺ or OH^" ions from one of the first and second domains to the other domain to thereby increase rate of release of nitric oxide from the first domain to body tissue.

The site of entry of the medical device may, in one embodiment, be selected form the group consisting of: the femoral artery, the radial artery, the carotid artery, the brachial artery, the auxiliary artery.

In one embodiment, the site of entry of the medical device is selected form the group consisting of: the radial artery, the brachial artery & the auxiliary artery. Such entry points are particularly preferred when using the introducer sheath according to the invention.

Other embodiments: The following specific embodiments may be combined with the other embodiments referred to herein.

Embodiment 1. A medical device for release of a therapeutic agent to a body of a living being upon wetting of at least a portion of a surface of the medical device, the medical device including at least a first domain and a second domain, wherein:

- the first domain is capable of releasing the therapeutic agent at a release rate; - the second domain is capable of affecting pH of at least one of the first domain and the second domain by shifting the local balance between H⁺ and OH^" ions upon wetting of at least a portion of the medical device; and wherein:

- the release rate of the therapeutic agent from the first domain is dependent on the pH of at least one of the first domain and the second domain.

2. The medical device of Embodiment 1, wherein the therapeutic agent comprises at least one of: a human growth factor, an anti coagulant, an antibiotic agent, a chemotherapeutical agent, a vasolidation agent, and a smooth muscle cell proliferation reducing agent.

3. The medical device of Embodiment 1 or 2 and including an intermittent or permanent intravascular implant.

4. The medical device of any of Embodiment 1-3, wherein the first domain comprises a first coating layer of the device. 5. The medical device of Embodiment 4, wherein the second domain comprises a second coating layer of the device.

6. The medical device of any of the preceding Embodiment, wherein the second domain includes at least one of: ascorbic acid, polyacrylic acid, oxylic acid, acetic acid, and lactic acid.

7. The medical device of Embodiment 5, wherein one of the first and second coating layers is provided on top of the other one.

8. The medical device of Embodiment 7, wherein the first coating layer is provided on top of the second coating layer.

9. The medical device of Embodiment 7 or 8, further comprising a third coating layer forming an outer surface layer of the medical device.

10. The medical device of any of Embodiment 7-9, further comprising a fourth coating layer provided between the first and the second coating layers.

11. The medical device of Embodiment 9 or 10, wherein at least one of the first, second third and fourth coating layers comprises polyurethane.

12. The medical device of any of the preceding Embodiment, wherein the therapeutic agent is immobilised in a hydrogel.

13. The medical device of Embodiment 12, wherein the hydrogel is mixed with glucoseoxidase (GOD).

14. A medical product comprising the medical device of any of the preceding Embodiments, the medical device being packed in a package, which prevents moisture from entering the package.

15. The medical product of Embodiment 14, wherein the package maintains a relative humidity in the package of at most 40% at room temperature.

16. The medical product of Embodiment 14 or 15, wherein the package maintains a pH of at most 7. 17. Use of a therapeutic agent in the preparation of a disposable medical device for the treatment of a cell disorder in a body duct, the medical device including at least a first and a second domain, wherein;

- the first domain is capable of releasing the therapeutic agent at a release rate; - the second domain is capable of affecting pH of at least one of the first domain and the second domain by shifting the local balance between H⁺ and OH^" ions upon wetting of at least a portion of the medical device; and wherein:

- the release rate of the therapeutic agent from the first domain is dependent on the pH of at least one of the first domain and the second domain.

18. A method of releasing a therapeutic agent from a medical device, the medical device including at least a first and a second domain, of which the first domain is capable of releasing the therapeutic agent at a release rate, and the second domain is capable of affecting pH of at least one of the first domain and the second domain by shifting the local balance between H⁺ and OH^" ions upon wetting of at least a portion of the medical device, and wherein the release rate of the therapeutic agent from the first domain is dependent on the pH of at least one of the first domain and the second domain, the method comprising the steps of:

- placing the medical device in contact with a bodily fluid of a living being; - wetting the medical device to thereby cause transport of H⁺ or OH^" ions from one of the first and second domains to the other domain to thereby increase rate of release of the therapeutic agent from the first domain to body tissue.

19. A method of applying a coating to a surface of a medical device, the coating including at least one therapeutic agent, the method comprising the steps of: - arranging the medical device in a confined environment; and subsequently:

- applying the coating to the surface of the medical device while controlling the pH of the confined environment to inhibit release of the therapeutic agent from the medical device.

20. The method of Embodiment 19, wherein the confined environment is maintained at a relative humidity of at most 40%.

21. The method of Embodiment 19 or 20, wherein the confined environment is maintained at a pH, which inhibits release of the therapeutic agent from the medical device.

LEGENDS TO FIGURES FIGURE 1: Schematic presentation for the synthesis of L-PEI and further processing to LPEI- NONO'ate. The poly(2-ethyl-2-oxazoline) used was produced by Polymer Chemistry Innovations Inc. (AQUAZOL^® 500) and has an average molecular weight of 500.000 g/mol.

FIGURE 2: Diagram of the introducer sheath purchased from Thomas Medical Products, US.

FIGURE 3: Principal of the spray pattern analyzer. The spray plume is illuminated by a laser sheet and captured by a high speed camera.

FIGURE 4: Simple illustration of the concept: The release of nitric oxide is impacted by the water absorption, the pH and the diffusion rate of nitric oxide through the coating layers.

FIGURE 5: Diazeniumdiolates and their suggested the mechanism of release.

FIGURE 6: Nitric oxide release dymanics using the primer/ (alkali) NO adduct coating system/outer layer.

FIGURE 7: illustrates various coated medical devices according to the invention as described herein. OL refers to outer layer, 1^st refers to the first domain, 2^nd refers to the second domain, 3^rd refers to the third domain, BM refers to the base material of the medical device - typically the external surface prior to coating. All embodiments show may also comprise a primer layer on top of the base material. The pH of the 1^st domain is preferably alkaline in embodiments A, B, C, D, F, G, H, and I, and may also be alkaline in E. The pH of the second domain is acidic in all embodiments where it is shown. The pH of the 3^rd domain is typically about neutral. The pH of the outer-coat is typically around physiological pH.. Diagrams F, G, H and I represent particles of the first and/or second domains, optionally coated with the third domain, which are embedded In either the first, second or third domains as illustrated.

FIGURE 8: A balloon coated with a linear poly(ethylenimine) diazeniumdiolate (LPEI-NONO) as disclosed in US 6,737,447 embedded in polyurethane and provided with a top coat of pure polyurethane was immersed in the head space chamber. Nitric oxide release started essentially immediately upon immersion of the inflated balloon in the head space chamber and increased asymptotically to a level of approximately 1.5 nmol/min/cm² in approximately 50 minutes. Due to the high load of NO in the LPEI-NONO, the release of NO maintained essentially constant for the remaining measurement period (approximately 140 minutes).

FIGURE 9: A balloon coated with a linear poly(ethylenimine) diazeniumdiolate (LPEI-NONO) as disclosed in US 6,737,447 embedded in polyurethane and supported by a coating layer of 90% polyacrylic acid and 10% polyurethane was immersed in the headspace chamber. Nitric oxide release started essentially immediately upon immersion of the inflated balloon in the head space chamber at a level above the threshould measurement maximum of the nitric oxide analysis apparatus (10 nmol/min/cm²). An asymptotic decrease to a level of approximately 1.2 nmol/min/cm² was observed until the measurement was interrupted after approximately 82 minutes.

FIGURE 10: A balloon coated with a linear poly(ethylenimine) diazeniumdiolate (LPEI- NONO) as disclosed in US 6,737,447 embedded in polyurethane and supported by a coating layer of 80% polyacrylic acid and 20% polyurethane, and further comprising a top coat of polyurethane was immersed in the headspace chamber. Nitric oxide release started essentially immediately upon immersion of the inflated balloon in the head space chamber at a level above the threshold measurement maximum of the nitric oxide analysis apparatus (10 nmol/min/cm²). An asymptotic decrease to a level of approximately 0.4 nmol/min/cm² was observed until the measurement was interrupted after approximately 105 minutes.

FIGURE 11: A and B represent balloons coated with a linear poly(ethylenimine) diazeniumdiolate (LPEI-NONO) as disclosed in US 6,737,447 and embedded in polyurethane without top coat. Formulation and processing is equal for both (A) and (B) except from the pH of the methanol used for dissolving the LPEI-NONO. The two balloons were dissolved in respectively alkaline methanol (A) and neutral methanol (B). The Balloons were immersed in the head space chamber. The peaks at approximately 15-17 minutes and at the end of the measurement, represent nitrite measurements (samples are indexed for comparison). 2005 1102 SGP E1-B2 #710 pH adjusted, 20051102 SGP El-Bl #719 not pH adjusted.

FIGURE 12: A and B represent nitric oxide release from a modified nylon (pebax™) tube coated with a linear poly(ethylenimine) diazeniumdiolate (LPEI-NONO) as disclosed in US 6,737,447 and embedded in polyurethane. Formulation and processing is equal for both (A) and (B) except for the presence of a top coat in A and the absence of top coat in B. The arrows illustrate where the coated tube has been removed and re-entered the measuring chamber. The nitric oxide signal between the arrow is equal to the nitric oxide release from the LPEI-NONO leaked out of the coat (samples are indexed for comparison). EXAMPLES

EXAMPLE 1: Manufacturing of the nitric oxide donor (L-PEI-NONO'ate)

In this example, the nitric oxide eluting coating applied to the medical device is based on linear polyethyleneimine (L-PEI) with pendant NONO groups. Each NONO group is covalently attached to one of the N atoms in the L-PEI polymer chain thereby forming an N* - N⁺(C) = N-O^' group in which N* is one of the atoms of the L-PEI backbone. This group is stabilized by the formation of a Zwitter-ion complex with an adjacent -NH₂ ⁺- amine group in the L-PEI backbone.

The manufacturing of L-PEI-NONO'ate may be divided into the following basic steps:

1. Synthesis of L-PEI (synthesized from poly (2-ethyl-oxazoline - see Warakomski and

Thill, 3. Polymer Science 1990;28:3551-63 for methodology)

2. Preparation of L-PEI powder.

3. Loading of L-PEI powder with Nitric Oxide. Loading occurred a reaction chamber under Nitric Oxide pressure where the LPEI was suspended in acetonitrile. The Nitric Oxide forms covalent bonds with the nitrogen atoms on the L-PEI, thereby forming the L-PEI-NONO'ate. This reaction was continued until the reaction reached equilibrium and no more NO was consumed (4-6 days depending on batch size). Subsequently, the L-PEI-NONO'ate was evacuated of any solvents and then grinded to a very fine powder.

The overall chemical reaction is illustrated in Figure 1.

Nitric oxide (NO) is a colourless and odourless lipophilic gas that with a aiπwater partition coefficient of 20: 1 and a maximum solubility of 1.7xlO^"3 M at 1 atm 25 ⁰C, making it easily diffusible across membranes. NO has an unpaired electron and is thus characterized as a free radical, allowing it to react with other species with unpaired electrons such as O₂ ^" and other radical species. Additionally, NO possesses high capacity to ligate with hemeproteins such as hemoglobin.

The NO used in the manufacture of the NO Eluting Introducer Sheath contains at least 99% V/V of NO. The impurities for the NO include the following gasses: carbon dioxide, nitrogen, nitrogen dioxide, nitrous oxide and water. The Nitric Oxide was purchased from Linde Gas. The purity is larger than 99% weight. Impurities are specified as non specific NOX < 0.5% by weight (N₂O, N₂O₃, N₂O₄, NO₂, N₂O₅) and Nitrogen < 0.5% by weight (N₂).

Poly(2-ethyl-oxazoline) was boiled for 24 hours in sulphuric acid. Boiling in a sulfuric acid solution was needed to reach the desired > 90% level of hydrolysis of poly(2-ethyl 2- oxazoline). In the isolation procedure of the formed product, polyethyleneimine, the formed propionic acid was distilled off and the sulfuric acid was neutralized with sodium hydroxide and then recrystallised several times in water to remove salt impurities, i.e. sodium sulphate and propionic acid residuals.

The production of LPEI from Poly(2-ethyl-oxazoline) eliminates the risk of residual ethyleneimine monomers.

The average molecular weight of the L-PEI-NONO'ate was found to be between 25 and 3OkDa, such as about 28kDa, with a relatively narrow distribution.

EXAMPLE 2: The Introducer Sheath

The introducer sheaths to be coated were purchased bulk from Thomas Medical Products, US. The (percutaneous) introducer sheath is used for intravascular introduction of interventional/diagnostic devices (See Figure 2).

Table 1: Materials used in the coating of the introducer sheath

Tradenames of polymers used: Tecoflex SG85A, Estane 58237, Tecophillic SP-93A.

EXAMPLE 3: 100 % Tecoflex in Pyridine (Primer layer) Solution: 2 % solid, (w/w), Tecoflex in Pyridine (in total 80 g).

1. 2 g Tecoflex SG85A was dried for 4 hours at 75 ⁰C

2. After drying the vessel was sealed and left at room temperature.

3. 1.6 g dried Tecoflex SG 85A was mixed with 78.4 g Pyridine and incubated overnight at 75°C. "Dried" Pyridine, 34945 from Riedel-de Haen was used.

4. The solution was homogeneous prior to use.

EXAMPLE 4 : Tecoflex/ Estane 70/30 to LPN formulation in amount 70/30

1. 2 g Tecoflex and SG85A 1 g Estane 58237 were dried for 4 hours at 75 ⁰C 2. After drying the vessel was sealed and left at room temperature.

3. Preparation of mixture A: 0.48 g dried Tecoflex SG85A, 0.12 g dried Estane 58237 and 29.4 g dried Pyridine were mixed. The mixture was sealed and incubated at 75 ⁰C overnight. The vessel was shaken vigorously several times during the incubation.

4. To prepare pH adjusted methanol, 50 mg NaOH was added to 30 ml water free (i.e. about 99.8% methanol or above) methanol.

5. Preparation of mixture B: 0.3 g LPN and 14.7 g (18.6 ml) pH adjusted methanol were mixed in a vial. The mixture was shaken briefly. The vessel was sealed and protected against light, and incubated at room temperature with stirring for 1 hours. The mixture was filtered through a 0.45 μm filter into a new vial. 6. Preparation of mixture C: Mixtures A and B were mixed in ratio 7:3 (e.g. 7 ml + 3 ml) into a new vial and sealed in a light proof vessel.

7. Mixture C was used for down stream processing. The maximum time from final preparation of mixture C and until termination of the down stream processes was 9 hours. The solution was shaken just prior to down stream processing.

EXAMPLE 5: 100 % Tecophillic SP-93A-100 in Pyridine

Solution: 2 % solid, (w/w) Tecophillic in Pyridine (in total 80 g).

1. 2 g Tecophillic SP-93A-100 was dried for 4 hours at 75 ⁰C

2. After drying the Tecophillic SP-93A-100 was sealed and stored at room temperature. 3. 1.6 g Tecophillic and 78.4 g Pyridine were mixed and incubated overnight at 75°C.

The vessel was shaken vigorously several times during the incubation. 4. The solution was homogeneous prior to down stream applications. EXAMPLE 6: Coating

The coating was applied in a three step spray coating process. The first step was to apply a USP class VI tested primer onto the sheath. For spray coating onto the sheath, the primer is dissolved in pyridine.

The second step is to spray a mixture of polyurethanes and L-PEI-NONO dissolved in methanol and pyridine onto the introducer sheath.

The third step is to apply a top coat.

The three different spray coating mixtures are described in detail in below.

The spray coating is performed with conventional air spraying equipment designed for a small fluid flow and low air pressure. The spray coating process is monitored and controlled to ensure that the spray process delivers a smooth uniform layer, and that the layer thicknesses are not subject to deviations.

The most critical source of variation in the spray coating setup is variation in the spray plume. Variations can include particle size variations and variations in spray plume geometry, e.g. that the spray plume will not be concentrated on the center of the rotating sheath during the spray-coating process.

Variations in the spray coating process are typically due to spray fluid drying up on the spray nozzle orifice thus altering the airflow. One way to manage this problem is to optimize the design of the spray nozzle and thereby avoid spray residue build-up. In addition, formulation of the spray mixture is optimized to prevent drying of the spray solution on the spray nozzle.

The spray process may be examined and optimised using advanced laser technique and highspeed camera. The equipment enables measuring the angle and orientation of the spray plume and analyzing variations. Furthermore, the equipment enables analysis of drop sizes and the impact of different parameters such as air flow and distance to the device surface. The working principal of this spray coating analysis equipment is illustrated by FIGURE 3.

The described technique is similar to the method required to validate the spray plume geometry for oral and nasal sprays. In order to ensure a specific target release resulting in the desired clinical impact (target release is in the range from 0.5 nmol/min/cm² - 40 nmol/min/cm²), the nitric oxide donor was incorporated into a polymeric matrix (FIGURE 4). The coating consists of 3 layers:

• Primer To ensure and optimize coating adherence to the device.

• Nitric oxide donating layer

The nitric oxide donating layer is a mixture of polyurethanes and L-PEI-NONO (LPN) dissolved in pyridine and methanol onto the medical device.

The recipe for the nitric oxide donating layer includes pH adjusted solvent (methanol) to ensure that the LPN is stable during processing.

• Topcoat

The polymeric topcoat serves to ensure coating integrity, a barrier solubilisation of the LPN polymer, appropriate rate of water absorption and appropriate rate of NO diffusion. When a topcoat is applied the release of nitric oxide deviates significantly from a l'order release. This is due to the barrier properties of the topcoat: limiting the water absorption and the diffusion of nitric oxide through the coating.

EXAMPLE 7: Layer thickness

When using confocal fluorescence microscopy the LPN layer has a relatively strong autofluorescence (blue/green). The other layers cannot be detected by this method, probably because they have no or very weak autofluorescence and because the top layer and the priming layers are too thin (less than 0.6-0.7 μm). By this method the thickness of the LPN layer, when dry, is determined to be in the magnitude of 4-5 μm, when applying 44 cycles of LPN (normal spray-coating parameters). When using only 22 cycles of LPN applied on the devices and when proportionality is assumed the LPN coating is in the magnitude of 2 μm.

The total coat is considered to be in the magnitude of 3 μm when using 22 cycles. However, coats of up to 40 μm may be appropriate and can be achieved by increasing the number of coating, such as spraying cycles.

When merged into an isotonic solution the coating swells as a result of water absorption. We have determined experimentally that the swelling increase the coating thickness by approximately 0.03 mm (30 μm).

EXAMPLE 8: Nitric oxide measurement Nitric oxide measurements were carried out by using a chemiluminescence NO analyzer (Sievers NO Analyser NOA 280i-2). The NO analyzer detects the total amount of NO(g) that passes the detector after a sample injection. The detection is based on the reaction:

NO + O₃ -> NO₂* + O₂

NO₂* -> NO₂ + hv

The emitted light (hv) is detected in a photomultiplier and is directly correlated to the amount of NO.

The principle is that NO eluting samples are placed in acid wash bottle (named head space chamber) containing PBS buffer (pH 7.4) added 0.0004%o Tween 20 covering the sample, which is continuously flushed with N₂ gas which carries the released NO gas to the NO analyzer. Due to the continuous flow of N₂, The presence of oxygen is thereby avoided and so is the formation of nitrite (NO₂ ^"). This method ensures that all NO and only NO is measured.

EXAMPLE 9: PACKING & STERILIZATION

Products are then packaged and sealed in an aluminum pouch are appropriate for sterilization by electron beam irradiation.

Coated medical devices may be sterilized by electron beam sterilization through a certified sub-contractor, such as Sterigenics, Espergade, DK.

The validation and routine sterilization is performed in accordance with the requirements of EN 552 (Sterilization of medical devices - Validation and routine control of sterilization by irradiation) and ISO 11137 (Sterilization of health care products - Radiation) and the products are sterile in accordance with EN 556 (Sterilization of Medical Devices) (SAL 10^"6).

EXAMPLE 10:

The release of nitric oxide (NO) from medical devices according to the present invention is illustrated in the below examples with reference to Figs. 8 - 10 Coated balloons with various coatings were immersed in a head space chamber containing phosphate-buffered saline

(PBS) maintained at pH=7.4 and body temperature, i.e. 37°C. The head space chamber was continuously flushed with N₂ gas, which carried the released NO to a nitric oxide analysis apparatus. The nitric oxide analysis apparatus comprised a so-called high-sensitivity detector for measuring nitric oxide based on a gas-phase chemiluminescent reaction between nitric oxide and ozone:

NO + 03 -> NO2* + 02 N02* -> N02 + hv

As emission from electronically excited nitrogen dioxide is in the red and near-infrared region of the spectrum, it could be detected by a thermoelectrically cooled, red-sensitive photomultiplier tube. The analysis apparatus used was a Nitric Oxide Analyzer NOA™ 28Oi provided by Sievers^®, Boulder, Colorado, USA.

In Figs. .8 - 10 the irregular discontinuities in the NO output signal derives from a discontinuity in the flow of NO to the analysis apparatus.

Example IQa. (Fig. 8) A balloon coated with a linear poly(ethylenimine) diazeniumdiolate (LPEI-NONO) as disclosed in US 6,737,447 embedded in polyurethane and provided with a top coat of pure polyurethane was immersed in the head space chamber. Nitric oxide release started essentially immediately upon immersion of the inflated balloon in the head space chamber and increased asymptotically to a level of approximately 1.5 nmol/min/cm² in approximately 50 minutes. Due to the high load of NO in the LPEI-NONO, the release of NO maintained essentially constant for the remaining measurement period (approximately 140 minutes).

Example IQb (Fig. 9): A balloon coated with a linear poly(ethylenimine) diazeniumdiolate (LPEI-NONO) as disclosed in US 6,737,447 embedded in polyurethane and supported by a coating layer of 90% polyacrylic acid and 10% polyurethane was immersed in the headspace chamber. Nitric oxide release started essentially immediately upon immersion of the inflated balloon in the head space chamber at a level above the threshould measurement maximum of the nitric oxide analysis apparatus (10 nmol/min/cm²). An asymptotic decrease to a level of approximately 1.2 nmol/min/cm² was observed until the measurement was interrupted after approximately 82 minutes.

Example IQc. (Fig. 10): A balloon coated with a linear poly(ethylenimine) diazeniumdiolate (LPEI-NONO) as disclosed in US 6,737,447 embedded in polyurethane and supported by a coating layer of 80% polyacrylic acid and 20% polyurethane, and further comprising a top coat of polyurethane was immersed in the headspace chamber. Nitric oxide release started essentially immediately upon immersion of the inflated balloon in the head space chamber at a level above the threshould measurement maximum of the nitric oxide analysis apparatus (10 nmol/min/cm²). An asymptotic decrease to a level of approximately 0.4 nmol/min/cm² was observed until the measurement was interrupted after approximately 105 minutes.

REFERENCES

[1] Iganarro et al. Oxidation of nitric oxide in aqueous solution to nitrite but not nitrate: Comparison with enzymatically formed nitric oxide from L-arginine Pharmacology, Vol. 90, pp. 8103-8107, September 1999

[2] L. K. Keefer et al.

Chemistry of the Diazeniumdiolates. 2. Kinetics and Mechanism of Dissociation to Nitric Oxide in Aqueous Solution.

3. Am. Chem. Soc. 2001, 123, 5473-5481

[3] Keith M. Davies,*,t David A. Wink,Φ Joseph E. Saavedra,§ and Larry K. Keefer.

Chemistry of the Diazeniumdiolates. 2. Kinetics and Mechanism of Dissociation to Nitric Oxide in Aqueous Solution. J. Am. Chem. Soc. 2001, 123, 5473-5481 [4] Dennis K. Taylor, Ian Bytheway, Derek H. R. Barton, Craig A. Bayse, and Michael B.

Hall. Toward the Generation of NO in Biological Systems. Theoretical Studies of the N 2 0 2 Grouping. J. Org. Chem. 1996,60, 435-444

[5] Andrew S. Dutton, Jon M. Fukuto and K. N. Houk. The Mechanism of NO Formation from the Decomposition of Dialkylamino Diazeniumdiolates: Density Functional Theory and CBS-QB3 Predictions. Inorganic Chemistry, Vol. 43, No. 3, 2004.

Claims

1. A medical device capable of releasing nitric oxide to a body of a living being upon wetting of at least a portion of a surface of the medical device, the medical device comprising a first domain which comprises polyethylenimine diazeniumdiolate, wherein the pH of the first domain is greater than pH 7.

2. The medical device according to claim 1, wherein the pH of the first domain is between about pH 8 and about pH 13.

3. The medical device according to claim 1, wherein the pH of the first domain is between about pH 9 and about pH 10.

4. The medical device according to any one of claims 1-3, wherein the first domain comprises an alkaline compound.

5. The medical device according to claim 4, wherein the alkaline compound is an inorganic compound, such as an inorganic compound with a pKb of less than 6 such as inorganic compound a with a pKb of less than 5.

6. The medical device according to claim 5, wherein the inorganic compound is selected from the group consisting of: NaOH, KOH, Ca(OH)₂, and LiOH.

7. The medical device according to claim 4, wherein the alkaline compound is an organic compound, such as an organic compound with a pKb of less than 6 such as a organic compound with a pKb of less than 5.

8. The medical device according to claim 7, wherein said organic compound is selected from the group comprising primary amines, secondary amines, tertiary amines, chloroquine, lithium diisopropylamide or methylamine.

9. The medical device according to any one of claims 4 or 8, wherein the alkaline compound is an either an organic or inorganic alkaline buffer.

10. The medical device according to claim 9, wherein the alkaline buffer is selected from the group consisting of: phosphate, ethanolamine, ADA, carbonate, ACES, PIPES , MOPSO, imidazole, BIS-TRIS propane, BES, MOPS, HEPES, TES, MOBS, DIPSO , TAPSO, triethanolamine (TEA), pyrophosphate, HEPPSO, POPSO, tricine, hydrazine, glycylglycine, Trizma (tris), EPPS, HEPPS, BICINE, HEPBS, TAPS, 2-amino-2-methyl- 1,3-propanediol (AMPD), TABS, AMPSO, taurine (AES), borate, CHES, 2-amino-2- methyl-1-propanol (AMP), glycine , ammonium hydroxide, CAPSO, carbonate, methylamine , piperazine, CAPS, CABS, and pipidine.

11. The medical device according to claim 4 - 10, wherein the alkaline compound is a polymer containing an inorganic or organic base, such as an inorganic or organic base with a pKb of less than 6, more preferable any inorganic or organic base with a pKb of less than 5, such as a base selected from the group comprising primary, secondary and tertiary amines.

12. The medical device according to any one of the preceding claims, wherein the polyethylenimine diazeniumdiolate has a molecule weight of between about 5kDa and about 20OkDa, such as between about 1OkDa and about 10OkDa, such as more preferably between about 2OkDa and about 6OkDa, such as about 3OkDa.

13. The medical device according to any one of the preceding claims wherein the polyethylenimine diazeniumdiolate is linear.

14. The medical device according to any one of the preceding claims, wherein said first domain comprising polyethylenimine diazeniumdiolate is applied as, or forms a coating layer applied on the external surface of the medical device.

15. The medical device according to any one of the preceding claims wherein said polyethylenimine diazeniumdiolate is not applied as, or does not form, fibres such as nanofibres, such as electrospun nanofibres.

16. The medical device according to claim 14 or 15, wherein said polyethylenimine diazeniumdiolate forms a homogeneous phase in said first domain.

17. The medical device according to claim 16, wherein said alkaline compound forms a homogeneous phase with said polyethylenimine diazeniumdiolate in said first domain.

18. The medical device according to claims 16 or 17, wherein said first domain comprising polyethylenimine diazeniumdiolate is in the form of a coating system comprising a polymer mixture, wherein said polymer mixture comprises polyethylenimine diazeniumdiolate and a hydrophilic supporting polymer or polymer blend, and optionally the alkaline compound, and wherein the polyethylenimine diazeniumdiolate and the supporting polymer or polymer blend, and optionally the alkaline compound, form a homogeneous phase.

19. The medical device according to claim 18, wherein the ratio of hydrophilic supporting polymer to polyethylenimine diazeniumdiolate present in the coating system is between about 5% to about 80%, such as between 10% and 50%, preferably between about 20% and about 50%, such as about 30%.

20. The medical device according to any one of claims 17 - 19, wherein the concentration of alkaline compound in the first domain is such that the OhTconcentration is between about 0.1 μM to about 2 mM OH- such as between 0.001 mM to about 1 mM OH- such as about 0.1 mM

21. The medical device according to any one of claims 18 - 20, wherein said polymer blend comprises a mixture of a support polymer and a hydrophilic polymer.

22. The medical device according to any one of claims 18 - 21, wherein the homogeneous polymer blend, provides a release rate of about 0.5 and about 40 nmol/min/cm² as measured by using a dynamic headspace chamber connected to a chemoluminescence NO detector at the point of maximum rate of increase of release of nitric oxide when inserted into phosphate buffered saline solution, pH 7.4 at 37°C.

23. The medical device according to any one of claims 18 to 22, wherein the support polymer and/or hydrophilic support polymer or polymer blend and/or coating system and/or homogeneous polymer blend can withstand a traction force applied to the surface of the polymer coat of about 4 to 100 newton cm^"2 such as about 8 to 50 newton cm^"2 such as preferably between 10 to 20 Newton cm^"2.

24. The medical device according to any one of claims 18 to 23, wherein the ratio of support polymer to hydrophilic polymer used in the in coating system is between about 95/5 to about 35/65 by weight.

25. The medical device according to any one of claims 18 to 24, wherein the thickness of the coating system is between is about 1 to about 100 μm, such as between 5 and about 20μm in dry state.

26. The medical device according to any one of the claims 1 to 25 wherein the base material is coated with an inner priming layer prior to (i.e. internal to) application of the coating system, such as the first or second domain.

27. The medical device according to claim 26, wherein the wherein the inner priming layer is a polyurethane primer.

28. The medical device according to claims 26 or 27, wherein the thickness of the priming layer is between about 0.2 and about 5μm.

29. The medical device according to any one of the preceding claims wherein the release of nitric oxide from the outer surface of the medical device is between about 0.5 and about 40nmol/min/cm² as measured by using a dynamic headspace chamber connected to a chemoluminescence NO detector.

30. The medical device according to any one of the preceding claims wherein the release of nitric oxide from the outer surface of the medical device has a half life under physiological conditions as measured by using a dynamic headspace chamber connected to a chemoluminescence NO detector, of at least 30 minutes, such as at least 60 minutes, such as at least 90 minutes.

31. The medical device according to any one of the preceding claims wherein the release of nitric oxide from the outer surface of the medical device has a half life as measured by using a dynamic headspace chamber connected to a chemoluminescence NO detector, of no greater than 6 hours, such as no greater than 4 hours, such as no greater than 3 hours.

32. The medical device according to any one of the preceding claims wherein the medical device is an intravascular medical device

33. The medical device according to claim 32, wherein the medical device is selected from the group consisting of: Neuro medical devices, such as neuro guiding catheter, neuro microcatheter, neuro microwire, neurostent delivery system, neuron ballon; coronary medical devices, such as coronary wires, coronary guiding catheter, PTCA angioplasty balloon; stent delivery system, coronary wires, coronary guiding catheter, PTA angioplasty balloon; introducer sheath, dilator, guide wire, syringe needle; and dialysis sheath.

34. The medical device according to any one of the preceding claims wherein the base material of the medical device consists or comprises of one or more of the compounds selected from the group consisting of: a metal, such as stainless steel, titanium, gold, plantinum; a plastic, such as PVC, PA, PS, Epoxy Resins, Silicone Rubber, Natural Rubber, Polyurethane, PE, PP, Polyester, Nylon, Polyester, PET, PMMA, Polysulphones, Polyphosphazenes, Thermoplastic Elastomers Polydimethylsiloxane (PDMS).

35. The medical device according to any one of the preceding claims wherein the density of application of polyethylenimine diazeniumdiolate onto the surface of the medical device is between about 0.05 mg/cm2 and about 100mg/cm2.

36. The medical device according to any one of the preceding claims which comprises a second domain which may be either internal or external to the first domain, wherein said second domain is capable of affecting the pH of the first domain by shifting the local balance between H⁺ and OH^" ions upon wetting of at least a portion of the medical device.

37. The medical device according to claim 36, wherein the second domain is capable of reducing the pH of the first domain upon wetting of at least a portion of the medical device.

38. The medical device according to claims 36 or 37, wherein the release rate of the nitric oxide from the first domain is dependent on the pH of at least one of the first domain and the second domain.

39. The medical device according to any of claims 1 to 38, wherein the first domain comprises a first coating layer of the device which is applied to, or is immediately adjacent to, either the base material of the medical device or the primer layer according to any one of claims 26 - 28.

40. The medical device according to claim 39, wherein the second domain comprises a second coating layer of the device which is applied to, or is immediately adjacent to said first coating.

41. The medical device according to any one of claims 36 - 40, wherein the pH of the second domain is between about pH 1 and below pH 7.

42. The medical device according to claim 36 - 40, wherein the pH of the second domain is between about pH 2 and about pH 6.

43. The medical device according to claim 36 - 40, wherein the pH of the second domain is between about pH 3 and about pH 5.

44. The medical device according to any one of claims 36 - 43, wherein the second domain comprises an acidic compound.

45. The medical device according to claim 44, wherein the acidic compound is an inorganic compound.

46. The medical device according to claim 45, wherein the inorganic compound is selected from the group consisting of: an inorganic acid with a pKa of less than 6, an inorganic acid with a pKa of less than 5, hydrochloric acid, sulphuric acid, nitric acid and hydrobromic acid.

47. The medical device according to claim 44, wherein the acidic compound is an organic compound.

48. The medical device according to claim 47, wherein said organic compound is selected from the group consisting of: an organic acid with a pKa of less than 6, an organic acid with a pKa of less than 5, ascorbic acid, polyacrylic acid, oxylic acid, acetic acid, and lactic acid.

49. The medical device according to any one of claims 44 to 48, wherein the acidic compound is an organic or inorganic acidic buffer.

50. The medical device according to claim 49, wherein the acidic buffer is selected from the group consisting of: maleate , phosphate , glycine , citrate , glycylglycine , malate , formate, citrate , succinate , acetate, propionate, pyridine, piperazine , cacodylate, succinate , MES, histidine, bis-tris, ethanolamine, ADA, and carbonate

51. The medical device according to claim 44 - 50, wherein the acidic compound is an acidic polymer, such as a polymer selected from the group consisting of: a polymer comprising an inorganic acid, a polymer comprising an organic acid, an inorganic or organic acid with a pKa of less than 6, inorganic or organic acid with a pKa of less than 5, a polymer comprising carboxylic groups.

52. The medical device according to claim 51 wherein the acidic compound is a polymer is either polyacrylic or polylactic acid.

53. The medical device of any one of claims 36 - 52, wherein one of the first and second domains are provided on top of the other one.

53. The medical device of any one of claims 36 - 52, wherein one of the first and second domains are provided on top of the other one,

54, The medical device according to claim 53, wherein the first domain is provided on top of the second domain.

55. The medical device according to any one of claims 1 - 54, wherein said medical device further comprises an outer layer, positioned externally to said first domain, said outer layer comprising a polymeric barrier between the poiyethylenimine diazeniumdiolate present in said first domain and the external environment (such as body fluid).

56. The medical device according to claim 55, wherein said outer layer prevents or reduces the release of poiyethylenimine diazeniumdiolate from said first domain when said medical device is in an aqueous ionic media, such as blood serum.

57. The medical device according to claim 55 or 56, wherein said outer layer controls the release of nitric oxide from said inner layer into the physiological medium.

58. The medical device according to any one of claims 55 - 57, wherein said outer layer controls the diffusion of water from the physiological medium into the inner layer under physiological conditions.

59. The medical device according to any one of claims 55 - 58, wherein said outer layer reduces or prevents the leakage of small molecule by products from said polymer mixture into the physiological medium.

60. The medical device according to any one of claims 55 - 59, wherein said outer layer comprises a hydrophilic polymer.

61. The method according to claim 60, wherein said hydrophilic polymer forms a hydroscopic gel upon insertion into physiological media.

62. The medical device according to any one of claims 55 - 61, wherein said outer layer comprises a hydrophilic polymer selected from the group consisting of polyurethane, polyolefins, such as polystyrene, polypropylene, polyethylene, polytetrafluorethylene, polyvinylidene difluoride, polyvinylchloride, derivatized polyolefins such as polyethylenimine, polyethers, polyesters, polyamides such as nylon, polyurethanes, silicones, or celluloses

63. The medical device according to claim 62, wherein said outer layer comprises a hydrophilic polymer selected from the group consisting of aromatic polyurethanes, ethylene acrylate polyolefins, hydrophilic aliphatic polyurethanes or high water vapour conducting silicones or celluloses.

64. The medical device according to any one of claims 55 - 63 wherein the outer-layer is an unbuffered layer, allowing the outer-layer to adjust to the physiological pH upon use.

65. The medical device according to any one of claims 55 - 64, wherein the pH of the outer layer is at about physiological pH, such as about pH 7.4.

66. The medical device according to any one of claims 55 - 65, wherein said outer layer has a thickness of between about 0.3 and about 5 μm.

67. The medical device of any of claims 36 - 66, wherein said medical device further comprising a third domain (fourth coating layer) provided between the first and the second domains.

68. The medical device according to claim 67, wherein said third domain is an unbuffered polymeric layer.

69. The medical device according to claim 67 or 68 wherein the third domain comprises a hydrophilic supporting polymer or polymer blend.

70. A method for the preparation of a (alkali) stabilised formulation of polyethylenimine diazeniumdiolate, suitable for use in the coating of intravascular medical devices, said method comprising dissolving polyethylenimine diazeniumdiolate (LPEI-NONO) in a alkali organic solvent.

71. The method according to claim 70, wherein said solvent is selected from the group consisting of: an alcohol, ethanol, methanol, aniline, benzaldehyde, and cyclohexylamine dimethyl sulfoxide.

72. The method according to claim 72 wherein the organic solvent is methanol.

73. The method according to claim 73 where the water content of the organic solvent is less than 1%, such as less than 0.5%

74. The method according to any one of claims 70 - 73 wherein the concentration of polyethylenimine diazeniumdiolate is between about 0.2% to about 20%, such as from about 1% to about 10%, such as about 1% to about 5%, such as about 2%.

75. A composition comprising an alkali stabilised polyethylenimine diazeniumdiolate, suitable for use in the coating of intravascular medical devices, wherein said composition comprises polyethylenimine diazeniumdiolate at a concentration of about 0.2% to about 20%, such as from about 1% to about 10%, such as about 1% to about 5%, such as about 2%, dissolved in an alkali solvent as according to any one of claims 70 - 73.

76. The composition according to claim 75, wherein said composition further comprises a polyurethane polymer and/or the hydrophilic support polymer or polymer blend as according to any one of claims 18 - 25.

77. A method for the manufacture of a medical device suitable for intravascular use, said method comprising:

a. selecting a medical device suitable for use in vascular surgery, said medical device comprising a base material,

b. Applying an first domain as according to the first domain of any one of claims 1 - 35 to at least a portion of said base material.

78. The method according to claim 77, which comprises applying at least one second domain which may be applied either internal (prior to) or external (subsequent) to the first domain, wherein said second domain is as defined in any one of claims 36 - 54.

79. The method according to claim 77 or 78, wherein prior to the application of the first domain, a primer according to any one of claims 26 - 28 is applied to the base material of the medical device.

80. The method according to any one of claims 77 - 79, wherein a third domain is applied between the application of the first domain and the second domain, to provide a barrier domain between the first and second domains.

81. The method according to claim 80, wherein the third domain is as defined in any one of claims 67 - 69.

82. The method according to any one of claims 77 - 81 wherein an outer layer according to any one of claims 55 - 66 is applied to the medical device once said first, and optionally said second and third domains have been applied.

83. The method according to any one of claims 77 -82 wherein the primer layer, first domain, second domain, third domain and/or outer layer are applied by spray coating, dipping, extrusion or painting.

84. The method according to any one of claims 77 - 83, wherein, prior to application onto the medical device, the first domain is prepared by mixing the composition according claim 75, or as prepared by the method of any one of claims 70 - 74 and the hydrophilic support polymer or polymer blend according to any one of claims 18 to 25.

85. A medical device for intravascular use, comprising a base material which either comprises polyethylenimine diazeniumdiolate, or is at least in part coated with an inner coating (or first domain) which comprises polyethylenimine diazeniumdiolate, wherein said medical device further comprises an outer layer, positioned externally to said base material or said inner coating (or first domain), said outer layer comprising a polymeric barrier between the polyethylenimine diazeniumdiolate and the external environment.

86. The medical device according to claim 85, wherein the outer-layer is as defined in any one of claims 55 - 66.

87. The medical device according to claim 85 or 86, wherein said medical device comprises a first domain as according to any one of claims 1 - 25.

88. The medical device according to any one of claims 85 - 87, wherein said medical device comprises a second domain as according to any one of claims 36 - 54.

89. The medical device according to any one of claims 85 - 88, wherein said medical device comprises a inner priming layer as according to any one of claims 26 - 28.

90. The medical device according to any one of claims 85 - 89, wherein said medical device comprises a third domain as according to any one of claim 67 - 69.

91. The medical device according to any one of claims 85 - 90, wherein the medical device is selected from the group referred to in any one of claims 32 - 34.

92. The medical device according to any one of claims 85 - 91, wherein the wherein the release of nitric oxide from the outer surface of the medical device is as according to any one of claims 29 - 31.

93. The medical device according to any one of claims 85 - 92 wherein the density of application of polyethylenimine diazeniumdiolate onto the surface of the medical device is between 0.05 and about 100mg/cm2.

94. A method for the manufacture of a medical device suitable for intravascular use, said method comprising:

a. selecting a medical device suitable for use in vascular surgery, said medical device comprising a base material or an inner layer (or first domain) which comprises polyethylenimine diazeniumdiolate;

b. Applying an outer layer to said medical device, said outer layer being defined as according to any one of claims 55 to 66.

95. The method according to claim 94, which comprises applying at least one second domain which may be applied either internal (prior to) or external (subsequent) to the inner layer (or first domain), wherein said second domain is as defined in any one of claims 36 - 54.

96. The method according to claim 94 or 95, wherein prior to the application of the first domain, a primer according to any one of claims 26 - 28 is applied to the base material of the medical device.

97. The method according to any one of claims 94 - 96, wherein a third domain is applied between the application of the first domain and the second domain, to provide a barrier domain between the first and second domains.

98. The method according to claim 97, wherein the third domain is as defined in any one of claims 67 - 69.

99. The method according to any one of claims 94 -98 wherein the primer layer, first domain, second domain, third domain and/or outer layer are applied by spray coating, dipping, extrusion or painting.

100. A medical product comprising the medical device of any of claims 1 - 69 or any one of claims 85 - 93, the medical device being packed in a package, which prevents moisture, oxygen and/or light from entering the package.

101. The medical product of claim 100, wherein the package maintains a relative humidity in the package of less than about 0.01% at room temperature

102. The medical product of claim 100 or 101, wherein the package is in the form of a sealed pouch with an inert gas atmosphere.

103. The medical product of any one of claims 100 - 102, wherein the oxygen (O₂) content in the package is less than about 0.1%.

104. A method of performing intravascular or neurovascular surgery, comprising inserting the medical device according to any one of claims 1 to 69, or as according to any one of claims 85 - 93, or prepared as according to the method according to any one of claims 77 - 84, or prepared as according to the method according to any one of claims 94 -99 into the vascular or neurovascular system of a patient.

105. A medical device according to any one of claims 1 to 69, or as according to any one of claims 85 - 93, or prepared as according to the method according to any one of claims 77 - 84, or prepared as according to the method according to any one of claims 94 -99 for intravascular or neurovascular use, for the prevention of one or more the conditions selected from: vasospasm or vasoconstriction, prevention of cerebral vasospasm, relaxation of smooth muscle, vasodilatation, thrombosis, decreased platelet deposition or aggregation, alleviation of restenosis, increased blood pressure, oxygen free radical reperfusion injury, treatment of cardiovascular disease, preventing the adverse effects associated with the use of said medical device, preventing abnormal cell proliferation.

106. Use of an outer coat as defined according to any one of claims 55 - 66 or 83 -

91, for prevention of the release of polyethylenimine diazeniumdiolate from a medical device suitable for intravascular use which comprises a base coat and/or an inner layer (or first domain) which comprises polyethylenimine diazeniumdiolate.

107. Use of an alkali compound or composition, for prevention of the release of nitric oxide from polyethylenimine diazeniumdiolate from a medical device suitable for intravascular use which comprises a base coat and/or a first domain which comprises said polyethylenimine diazeniumdiolate and said alkali compound or composition.

108. Use of a alkali stabilized polyethylenimine diazeniumdiolate in the preparation of a disposable medical device for the treatment of a cell disorder in a body duct, the medical device including at least a first domain, and optionally one or more of the further domains or layers as according to any one of the preceding claims;

109. A method of applying a coating to a surface of a medical device, the coating including at least polyethylenimine diazeniumdiolate, the method comprising the steps of:

- arranging the medical device in a confined environment; and subsequently: - applying the coating of polyethylenimine diazeniumdiolate to the surface of the medical device while controlling the pH of the confined environment to inhibit release of the nitric oxide from the medical device.

110. The method of claim 109, wherein the confined environment is maintained at a pH greater than 7.