MXPA02002931A - Resorbable implant materials - Google Patents

Abstract

A noncrosslinked, decellularized and purified mammalian tissue (e.g., bovinepericardium) having particular use as an implantable resorbable material. The material is treated by alkylating its primary amine groups in a manner sufficient to reduce the antigenicity of the tissue, permitting the treated tissue to be used in vivo and without crosslinking, and in turn, permitting it to be resorbable. The material can be used in surgical repair of soft tissue deficiencies for a certain period of time while the implant itself is gradually remodeled or absorbed by the host. Also provided are a method of preparing such a material as well as a method of using such a material for surgical repair.

Description

REABSORBIBLE IMPLANT MATERIALS TECHNICAL FIELD The invention relates to materials for use as implants within the body, and in particular with resorbable materials} remodelables for such use.

BACKGROUND OF THE INVENTION Currently there are resorbable materials (occasionally referred to as absorbable or "castable") for use in prosthetic applications, for example, patches, implants and / or com? prosthetic device components.

Synthetic resorbable materials made of polyesters, polylactide and polyglycolide, for example, have found use in various fields of medicine (See, for example, Ashammaki, NA, J. Biomed, Mater. Res., 33: 297-303; 1996 ). Commercial versions of these materials are available under the trade names of V: .cryl® (Ethicon, Inc.) and Dexon® (Davis &Geck, Inc.). The gradual composition of these polymers is facilitated by hydrolysis, and catalyzed by the biochemical action of host tissues (Hanbrough, J.F., et al, J. Burn Care Rehab., 14: 485-494, 1993). Those materials they can be produced as membranes or as a woven mesh in the case of the production of resorbable suture.

Although synthetic resorbable materials are a more recent phenomenon, collagen materials have been used as prosthetic inserts for many years, as in the case of freeze-dried human dura, dating from 1954. As a common practice they last for a long time. several years, such collagenous materials have been crosslinked as an agent such as glutaraldehyde, to dissolve the antigenicity of a xenograft while increasing its resistance to enzymatic degradation produced by host tissue responses (Gratzer, PF, et al., J. Biomed, Mater. Res., 31: 533-543; 1996) Polyepoxy compounds have also been used for such purposes, however they are more stable with respect to the resulting alkylated amines in collagen (Sung, HW., Et al. ., J. Biomater, Sci. Polymer Edn., 8: 587-600, 1997). Although cross-linked tissues work well as long-term implants, they are not resorbable, and therefore, do not promote remodeling of the host tissue, or in turn, the eventual replacement of a graft by the body itself.

Aesculap AG & Co (B. Braun Surgical) offers products under the trademark of Lyoplan®, in the form of a resorbable replacement based on bovine pericardium for hard matter. Lyoplan is produced by a process that * - f ******, It involves the mechanical removal of adherent fat and connective tissue, chemical treatment to inactivate enzymes and potential pathogens, lyophilization, cutting to various sizes, packaging and terminal sterilization with ethylene oxide. The product is indicated to be used to cover lasting cerebral and cerebellar effects, for decompressive duraplasty in cases of increased intracranial pressure, to cover spinal dural effects and for decompressive spinal duraplasty. It has been observed that this material is completely remodeled within one year after implantation.

Tutogen Medical, I nc. It provides pericardial products processed under the brand name Tutoplast, in the form of a preserved human pericardium, dehydrated with solvent, and radiated with gamma radiation. Tutoplast® tissue processing involves perfect cleaning, processing, dehydration and preservation. It is said that the process leaves no harmful residues and minimizes the antigenic potential. Collagenous connective tissue with multidirectional fibers retains the mechanical strength and elasticity of the native pericardium, while providing the basic formative structure to support replacement by new endogenous tissue. This tissue is indicated for use in a variety of surgical applications, including duraplasty (as a substitute for material biodegradable infusion to be used in the treatment of urethral obstructions. Stack, et al., U.S. Patent No. 5,306,286 describes an absorbable stent to be placed inside the blood vessel during coronary angioplasty. Duran, U.S. Patent No. 5,376,112 discloses an annuloplasty ring to be implanted in the heart to function in conjunction with the native heart valve. In another aspect, U.S. Patent No. ,837,278 (Geistlich, et al., "Resorbable Collagen Membrane for Use in Guided Regeneration of "Fabric" describes the use of a collagen-containing membrane in the guided generation of tissue The Patent provides a resorbable collagen membrane for use in guided tissue regeneration where one face of the membrane is fibrous thereby allowing growth cell on the Lia and the opposite face of the membrane that is smoothed, thus inhibiting the cellular addition on it.

Finally, see U.S. Patent No. 5,413,798 (Scholl, et al.) 1, which describes a process for treating bovine pericardial tissue to increase resistance to biological degradation by wet chemical processing. The use of a tissue is exemplified in the form of an implant, which after three and six months after used in a variety of applications, including as patches, suture and support members for the stapling line, and warranties.

SUMMARY OF THE INVENTION The present invention provides a non-crosslinked, decellularized and purified mammalian tissue (e.g., bovine pericardium) which has particular use as an implantable material so that it is resorbable and removable. The material is prepared by alkylating the primary amine groups of the natural tissue in a manner sufficient to reduce the antigenicity of the tissue, and in turn, to a degree that allows the treated tissue to be used in vivo and without crosslinking, thereby allowing this be absorbable The material can be used, for example, in the surgical repair of soft tissue deficiencies, for a period of time, while the implant itself is gradually remodeled or absorbed by the host. In a related aspect, the invention provides a method for preparing such material, as well as a method for using such material for surgical repairs. As used herein with respect to a material of the present invention, the word "reabsorb" and inflexions thereof will refer to a material that, once implanted in vivo, is reabsorbed by the body and with time and without undue harmful effects in or inside the body itself. The word "remodel" and inflections thereof, as used herein with respect to a material of the present invention, will refer to a resorbable material that is adapted, for example, by virtue of its location and method of implant within the body. , to encourage and / or allow the body to replace some or all of the structures and / or functions of the implant with newly formed natural tissue. While not intending to be bound by theory, at least in some embodiments of the present invention, remodeling seems to occur by a gradual bodily process in which substantial portions of the implant material are gradually reabsorbed, while an inherent fibrous network of the implant be retained on the site. The network, in turn, is used by the body as a scaffold for the generation of new woven or tissue components.

In a preferred embodiment, the invention provides a resorbable implantable material comprising a non-crosslinked, decellularized and purified mammalian tissue having most of its free alkylated amine groups. In a particularly preferred embodiment, the tissue is selected from the group consisting of pericardium, peritoneum, fascia lata, dura dura, dernis and submucosa of the intestine and the material has been alkylated by an alkylating agent selected from the group consisting of 1,2-epoxy-R compounds where R is an alkyl group of up to 6 carbon atoms. Such material may be provided in any suitable form, for example,] as flat or textured sheets or strips, and may be adapted for use in a variety of surgical applications, including those selected from the group consisting of plasty, thoracic, abdominal surgery. , urological, ophthalmic, cardiac and vascular.

DETAILED DESCRIPTION A woven fabric of the present invention can be obtained from any suitable source, including mammalian sources for example, in the form of collagenous connective tissue with three-dimensional inter-braided fibers. Such tissues generally involve serous and fibrosarcoma membranes. In a particularly preferred embodiment, the tissue source is selected from bovine pericardium, peritoneum, fascia lata, dura, stem, dermis and submucosa of the small intestine. In a further preferred embodiment, the tissue is bovine pericardium, and is treated using a method as described herein to provide the treated tissue with an optimum combination of biocompatibility, thickness and other physical and physiological properties.

The fabrics of the present invention may be provided from durja material, for example, for use in neurosurgical applications. Collagenous connective tissue with three-dimensional inter-braided fibers, when treated in the de-rusted form here, retains the multidirectional and mechanical strength of the native hard matter, while providing the basic formative structure to support replacement with new endogenous tissue.

Although it is desirable to reduce or eliminate the antigenic properties of material based on xenographic or even allographic tissue to be implanted in a body, if the absorption and / or remodeling of the body material is desired, cross-linking can not be effected. To effect in a specific manner such a modification of a material based on collagen, a monofunctional reagent is used. The reagent is "monofunctional" since it is adapted to react with, and therefore terminate and "crown" the available amine functionalities of the tissue proteins, but will not react more with adjacent groups. An optimum reagent of this invention, therefore, is preferably a relatively small and structurally simple compound that, after reacting with group > Proteins such as amines will bind to those groups but in such a way that they do not alter the biological properties of the collagen matrix to a degree that renders the tissue unsuitable for its intended use.

In a particularly preferred embodiment, a woven fabric of the present invention is treated by a process that includes renting a greater percentage of the available amine groups to a sufficient degree to allow the tissue to be implanted and used in vivo. Preferably a fabric is processed by alkylating its amines to a sufficient degree to react 80% or more, preferably 90% more, more preferably 95% or more of the amine groups originally present. The efficiency and degree of alkylation can be determined by a variety of means, as described herein, including the use of a ninhydrin-based assay ("am: .nas index") to determine the comparative level of amine groups, before and after after the treatment (see, for example, Sung HW, et al., Art Org., 21: 50-58; 1997. Sung, HW, et al., J. Biomed, Mater.Res. 33: 177-186. ). Preferably the efficiency and degree of the alkylation process is further evaluated by determining the unreacted amounts in the incubation of the batch of the alkylating agent used.

Preferred alkylating agents can be used, for example, at a pH between about 9 and about 11, and at a concentration between about 2% (w / w) and about 5% (weight / weight), exposing the tissue to a solution containing the agent for at least 48 hours. the branching of the collagen polymer by the action of the alkylating agent and the subsequent alteration of the collagen matrix (Tu, R., et al., J. iomed, Mater. Res., 28: 677-684, 1994).

In a preferred embodiment, the tissue of the present invention is also treated with a base such as sodium hydroxide (NaOH), to further reduce the possibility of further transmission of Bovine Spongiform Encephalopathy (BSE). Histological analyzes of tissue treated with NaOH (pericardium, for example) reveal a virtually complete decellularization due to this treatment Since it is known that the cellular component of the tissue contains the vast majority of antigen loading (Corutman, DW et al. ., J. Biomed, Mater. Res., 28: 655-666.; 1994), decellularization treatment with NaOH may complement the use of an alkylating agent to reduce antigenicity.

A fabric of the present invention can be used to manufacture a prosthetic article having any suitable shape or configuration, and in any dimensions suitable for its intended use. For example, the fabric may be proportioned and packaged in a flat configuration (eg, sheet, or ribbon-like), with either or both surfaces thereof being optimally textured or moaiified (eg, by bonding). covalent, trapped and / or adsorption of biologically active factors, lubricating agents, antimicrobial agents and the like).

In a preferred embodiment, a process of the present invention includes the steps of: a) obtain pericardi from an appropriate source (eg, approved by the USDA) b) cleaning the weave and optionally, and preferably, treating the ejido, for example, to decellularize this and / or to • produce / eliminate the infectivity of BSE of potential, c) alkylating the tissue (e.g., hydroxypropylation using propylene oxide) to coat a larger percentage of available amine groups * (by eject, potentially reactive), and optionally, d) end processing; 1, which includes one or more of the following steps: washing, drying, sterilizing and packaging the fabric.

Natural tissues suitable for use in the process of the present invention preferably meet strict specifications during donor selection and laboratory testing to reduce the risk of transmission of infectious diseases. The process in such a way that the free edges of the implant do not exceed the areas where the possibility of adhesion may present a problem. Absorbable or non-absorbable suture material, for example glue, etc. can be used to fix the tissue in place. For a continuous suture, absorbable suture material and round atraumatic needles are recommended, although the size of the suture depends on the surgical indication. The suture should be located two to three millimeters from the edge of the graft. Better results are obtained by folding the section in suture sites that are under moderate to high stress. The weaves of the present invention provide a variety of features and advantages, including the fact that they are immediately available for surgery and can save valuable time in the operating room.

In addition, there is no secondary surgery site and less stress for the patient; The bual can result in less time under anesthesia, painless as a weakness of the patient, and the patient} . Since tissues can be made available in a wide range of sizes, the surgeon can choose the necessary size, leading to minimal waste. As with biological products, it is not possible to provide an absolute guarantee of freedom from infectious infectious diseases such as stannous, 0.16% (w / v), pH 5.0] 95-100 ° C for 30 minutes. 5. Cool the tubes to room temperature. 6. Add 250 μl of collagenase sample to 1.0 ml of 50% isopropanol. Vortex stir and read the absorbance 570 nm. 8. The absorbance at 570 nm is divided by the weight of the piece of tissue to give the OD / mg. The OD / mg is the value of the amount of collagen peptide that has been degraded by the action of the collagenase enzyme. The results of the collagenase assay are determined by comparing the mu-test with both positive (untreated) and negative (cross-linked with glutaraldehyde) control samples.

Amine index. The amine number can be defined as the percentage of initiating amines available that have been modified (and therefore rendered substantially unreactive in vi tro) by reaction with amine reagents. Such modification will render the amine incapable of producing "Ruhemann purple" when introduced into ninhydrin, and the relevant assay may be carried out as follows: 1. 200 μl of DI water was added to 25-30 milligrams of tissue. 2. Add one thousand Llitro of ninhydrin solution to each tube. 3. Incubate the tubes at 95-100 ° C for 30-35 minutes. 4. Cool the tubes to room temperature. 5. Add 250 μl of sample to one milliliter of 50% isopropanol solution. 6. Vortex and see absorbance at 570 nm. 7. The amine number is calculated. To calculate the percentage of modified original amines, the following formula is used: Amine index (%) = [* control (OD / mg) -sample (OD / mg)] x 100 control (OD / mg) The OD / mg was dividing the OD @ 570 by the weight of the piece of tissue. * The control is unmodified tissue Test for the quantification of Alkylating Agent without React The purpose of this test is to confirm that although 100% of the alkylation of the amine is typically not achieved, this is not due to the lack of an alkylating agent NaOH and Neutralization 1. Weigh 40-45 grams of bovine pericardium. 2. Place the per.cardium in one liter of NaOH 1.0 M (40 grams of NaOH in a .itro of DI water) for 60-65 minutes. Take a sample to measure the pH at the end of the wash. 3. Decant the STaOH, gently squeeze the tissue and place it in two liters of DI water filtered for 30-35 minutes. 4. Decant DI water and place tissue in two liters of cijtrato buffer (28 grams of sodium citrate and 2.0 grams of citric acid in two liters of DI water) for 60-65 minutes. Take a sample to measure the pH at the end of the wash. 5. Decant the citrate buffer, gently squeeze the tissue and mix the tissue in another two liters of DI water for 30-35 minutes.

Fabric Alkylation 1. Prepare a solution of 5% Propylene Oxide (50 milliliters of propylene oxide in 950 milliliters of 0.2 M carbonate buffer, pH 10.5-10.6). 2. Place the fabric treated with NaOH in propylene oxide solution.