EP2121060A1 - Verfahren zur bereitstellung eines kompositfilms auf einem substrat - Google Patents
Verfahren zur bereitstellung eines kompositfilms auf einem substratInfo
- Publication number
- EP2121060A1 EP2121060A1 EP08708836A EP08708836A EP2121060A1 EP 2121060 A1 EP2121060 A1 EP 2121060A1 EP 08708836 A EP08708836 A EP 08708836A EP 08708836 A EP08708836 A EP 08708836A EP 2121060 A1 EP2121060 A1 EP 2121060A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- substrate
- layer
- film
- solution
- composite film
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
- A61L27/28—Materials for coating prostheses
- A61L27/30—Inorganic materials
- A61L27/306—Other specific inorganic materials not covered by A61L27/303 - A61L27/32
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
- A61L27/28—Materials for coating prostheses
- A61L27/34—Macromolecular materials
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
- A61L27/40—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material
- A61L27/42—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material having an inorganic matrix
- A61L27/427—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material having an inorganic matrix of other specific inorganic materials not covered by A61L27/422 or A61L27/425
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
- A61L27/40—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material
- A61L27/44—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material having a macromolecular matrix
- A61L27/446—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material having a macromolecular matrix with other specific inorganic fillers other than those covered by A61L27/443 or A61L27/46
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D1/00—Processes for applying liquids or other fluent materials
- B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D2350/00—Pretreatment of the substrate
- B05D2350/60—Adding a layer before coating
- B05D2350/63—Adding a layer before coating ceramic layer
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/50—Multilayers
- B05D7/56—Three layers or more
Definitions
- the present invention relates to a method for providing an organic-inorganic composite film onto a substrate, in particular biomaterials, and to such substrates.
- a substrate in particular biomaterials
- the fabrication of well controlled composite coatings on solid surfaces is a promising new tool to control both the mechanical, optical, wetting and permeability properties of the interface between the solid and its surroundings.
- WO 04/047880 proposes to produce a composite coating of polyelectrolyte and particles of calcium phosphate by immersion.
- a refractory laminate may be prepared on the surface of a support by dipping the support into a bath of colloidal silica or alkaline ionic silicate to form a coating on the substrate, contacting the coated surface with a polycationic organic setting agent and repeating this sequence until the coating has the desired thickness.
- both these methods use immersion of the substrate into a solution as a deposition technique.
- This technique is however quite costly because it implies the use of large volumes of solution.
- it is further necessary to dry the substrate before proceeding with the next step, which is energy and time consuming, in particular for coating formed by a large number of layers.
- the coating obtained generally has an inhomogeneous thickness, and may be opaque in the visible spectrum.
- the present invention is based on the observation that multilayer composite films can be obtained using a layer-by-layer deposition spray coating if the mineral oxide precursor solution is chosen to be stable to allow for its application through a spraying nozzle, but to decompose upon contact with active groups of the underlying polycationic compound to yield oxide particles. This method allows a rapid and low cost preparation of composite films on a variety of substrates.
- the films obtained have a homogeneous thickness which can be finely tuned according to the intended application. Further, the films show a particular behaviour with respect to their permeability towards multivalent ions.
- the present invention thus aims at a method for providing a composite film onto a substrate comprising the steps consisting of: i) coating onto a substrate a solution comprising a polycationic compound by spray coating, thus forming a layer A; ii) coating onto the layer A a solution of mineral oxide precursor by spray coating, thus forming a layer B; and iii) repeating steps i) and ii) until the formed composite film has the desired thickness.
- the proposed method is also called hereafter "reactive layer by layer spray coating”.
- a major feature of the proposed method is the fact that the mineral oxide precursor is decomposed upon contact with the polycationic compound present in the preceding, underlying layer.
- the contact with the polycationic compound induces a reaction, such as a polycondensation, of the mineral oxide precursor, which yields the mineral oxide.
- a number of deposition steps are necessary to form a homogeneous film. Generally, this film will be considered as homogeneous upon percolation of the mineral oxide particles.
- the number of deposition steps necessary to obtain a homogeneous film may depend on a number of process parameters, in particular on the concentration on the solution used. Generally however, at least 10 layer deposition steps (counting either step (i) or step (N)) are necessary to obtain a homogeneous film.
- the polycationic compounds do not only play the role of a catalyst by enhancing the rate of mineral oxide decomposition but they may also be an active component of the obtained composite material.
- infrared spectra of composite films obtained according to the invention show that the Si-O stretching band is significantly displaced from 1085 cm “1 in the absence of polycation to 1039 cm “1 for the polycation containing material.
- Preferred polycationic compound are hydrosoluble, so as to allow to work in aqueous solutions and to avoid organic solvents.
- Particularly preferred polycationic compounds are chosen from polyamines, polyimines and, polyaminoacids, and copolymers comprising amine, imine or aminoacid groups.
- Amine groups may be aliphatic or aromatic primary, secondary, tertiary or quaternary.
- the cationic charge density of these compounds depends essentially on the pH of the solution. Nitrogen containing groups are particularly preferred because they further have a nucleophilic character. Among these, polyallylamine hydrochloride (PAH) and poly(diallyldimethyl ammonium chloride) (PDADMAC), polyethylene imine (PEI), poly-L-histidine, poly- L-lysine and poly-4-vinylpyhdine are particularly preferred.
- PAH polyallylamine hydrochloride
- PDADMAC poly(diallyldimethyl ammonium chloride)
- PEI polyethylene imine
- poly-L-histidine poly-L-histidine
- poly- L-lysine and poly-4-vinylpyhdine are particularly preferred.
- L-poly-aminoacids are mentioned in particular because they are easily available, however D-polyamino-acids are equally appropriate.
- the polycationic compound is used in solution, preferably in aqueous solution and particularly preferred in a buffered solution.
- concentration of the solution is not critical, as long as the solution is stable. A concentration of about 0,1 to 1 mg/mL is generally suitable.
- mineral oxide precursors is understood to cover compounds that are capable of reacting with the reactive groups of the polycationic compounds, for instance by a polycondensation reaction to yield, directly or indirectly, a mineral oxide.
- the term aims in particular at compounds that form mineral oxides in presence of cationic groups such as amine or imine groups.
- aqueous solutions of mineral oxide precursors which are therefore preferably hydrosoluble.
- Hydrosoluble mineral oxide precursors may be used as aqueous solutions, and allow to avoid the use of solvents, which may be dangerous for human health when inhaled.
- Particularly preferred hydrosoluble mineral oxide precursors are chosen from silicic acid and water soluble metal alkoxydes but metal complexes comprising anionic ligands such as titanium (IV) (bis ammoniumlactate) dihydroxyde may also be used.
- anhydrous solvents such as alcohols, ethers and esters and their mixtures may also be valuable for the process claimed, since some mineral oxide precursors such as metal alkoxydes may undergo spontaneous condensation in presence of water.
- a mineral precursor solution in alcohols such as methanol, ethanol, isopropanol and n-propanol.
- alcohols such as methanol, ethanol, isopropanol and n-propanol.
- the mineral oxide precursor is preferably a silicon compound or a titanium compound. From the large groups of mineral oxide precursors, metal alkoxydes are particularly preferred.
- Preferred alkoxydes are organometallic compounds having at least one group derived from an alcohol by removal of one H atom. Alkoxydes tend to hydrolyse in presence of water to form metal hydroxides, which are generally unstable and polycondensate to yield oxides and water.
- metal alkoxydes are in particular titanium alkoxydes, silicium alkoxydes and zirconium alkoxydes. Most preferred Ti(OBu) 4
- stable solution is intended to mean a solution which does not show a noticeable precipitation, as detected by the onset of turbidity for at least two hours under room temperature. The onset of turbidity was followed by UV-Vis spectroscopy at a wavelength of 350 nm for experiments performed with silicic acid.
- the solution of the mineral oxide precursor is buffered to a pH such as to prevent precipitation, in particular spontaneous polycondensation.
- the pH suitable for an optimal stability will depend on the nature of the mineral oxide precursor.
- a solution of silicic acid or of titanium (IV) (bis ammoniumlactate) dihydroxyde can be stabilized at a pH of around 7,4.
- the use of 50 mM Tris buffer is thus appropriate for these precursors.
- the solution of the mineral oxide precursor has a concentration such as to prevent precipitation, in particular spontaneous polycondensation.
- a low precursor concentration is favourable in terms of stability because it will slow down the precipitation.
- the determination of the optimal concentration is a matter of routine testing. As an example, a concentration of less than 30 mM has been found suitable for silicic acid while a concentration of up to
- the solutions may be provided in separate vessels equipped respectively with a spraying nozzle. It is also possible to provide the solutions through a spray coating device having a common spraying nozzle.
- the substrate is preferably hold with an angle, preferably nearly or completely vertically during spray coating. Thereby, excess solution is eliminated easily by gravity.
- step ii) it can be advantageous to leave the substrate for some seconds in order to allow for the reaction between the mineral oxide precursor and the polycationic compound.
- the coated substrate is rinsed after step i) and step ii), respectively.
- the rinsing is normally done with the solvent of the solutions used. When working with aqueous solutions, the rinsing may be carried out conveniently using water.
- the layers have a varying thickness.
- the thickness of one layer will be lower than one micron.
- the alternate layers A and B have a respective thickness of about 1 nm to about 100 nm. Particularly preferred is a thickness of about 10 to about 50 nm.
- a continuous film is understood to mean to be formed upon percolation of the particles in the film. This can be determined easily by using a technique such as Atomic Force Microscopy.
- steps i) and ii) necessary to obtain a continuous film will depend on the process parameters such as the concentration of the solution and the nature of the substrate. However, generally, the repetition of steps i) and ii) for between 10 and 100 times is appropriate to yield a continuous film.
- the obtained homogeneous composite films are made from mineral oxide particles agglomerates and polycations. These films have a defined composition, thickness and structure. Generally, the total thickness of the films is from about 10 nm to about 1000 nm.
- the cohesion of the different layers in these films is not only due to electrostatic interactions, but also by bonds created by the chemical reaction between the polycationic compound and the mineral oxide precursor.
- a second aspect of the invention concerns a substrate coated with a composite film of alternate layers A and layers B, wherein layer A comprises or is made of a polycationic compound and layer B comprises or is made of a mineral oxide.
- the first layer on the substrate is a layer A.
- a primer film between the substrate and the composite film.
- a primer film may in particular comprise a polyanionic layer.
- a primer film consisting of a polyelectrolytic layer obtained by depositing alternately a polyanionic and a polycationic compound.
- An appropriate multilayer primer film typically consists of 2 to 20 layers.
- the substrate may be a solid made of or comprising a metal oxide, a glass, or a polymer.
- biomaterials that is materials that do not elicit a negative response when put in contact with biological tissues, and especially materials that are intended to be placed within the living body, in particular implants and prosthesis.
- the described method can also be used on glass substrates to create antibacterial substrates. These films can also find applications in photovoltaic cells.
- the substrate can be used as such or eventually beforehand coated with a primer film.
- a primer film can be for instance a polyelectrolytic film formed of alternate layers of polycationic compounds such as polyethylene imine (PEI) or polyaminoacid and polyanionic compounds such as poly-4-styrene sodium sulfonate (PSS).
- PEI polyethylene imine
- PSS polyanionic compounds
- Such a primer film can be for instance a PEI (PSS-PAH) 5 architecture.
- the primer film is deposited by spray coating.
- the composite films thus obtained are intrinsically porous. This particular feature allows for the inclusion of active species in the film, which may then be released progressively, in particular within the body.
- the composite films may in particular contain one or more pharmaceutically active species. Such active species may be for instance drugs or enzymes.
- Composite films thus obtained display selective permeability towards small anions whereas pure mineral oxides such as silica gel is permeable towards small cations. This shows that the sign of the fixed charges in the composite material has been reversed from negative to positive upon polycation incorporation.
- titanium dioxyde particles for instance are negatively charged at pH 7.4.
- the composite film may, as described above, be coated on top of a primer film. Further, according to another embodiment, the composite film may further be coated with another film, in particular with a polyelectrolyte film.
- the composite films prepared according to the disclosed method comprise mineral oxide particles of nanometrical size and may therefore also be useful as optical films.
- composite films obtained with titanium oxide precursors can be useful as UV filters since the particles absorb light in the UV region, while having a high transmission in the visible region.
- the composite films may be used with suitable mineral oxides as high refractive index films.
- the composite films may also be useful as photocatalytic films, in antibacterial films, and for the preparation of photovoltaic cells.
- the composite films are porous and present an excess of immobile electrical charges compensated by small anions. Therefore, they may also be useful for filtration purposes, such as for water filtration.
- Fig.1 the absorbance at 350 nm of silicic acid solutions with different concentrations and after adding PAH;
- Fig. 2A the optical thickness of a film obtained according to the invention (o, ⁇ ,
- Fig. 2B the thickness increment per layer pair of a composite film obtained by spray deposition of silicic acid and PAH as a function of the concentration of the silicic acid solution used;
- Fig. 3 the thickness of a composite film obtained according to example 6 using different mineral oxide precursors
- FIG. 5A AFM image acquired by scanning perpendicularly to a scratched line on a PEI-(PSS-PAH) 5 -(silicic acid-PAH) 15 film according to example 1 ;
- Fig. 5B an ESEM micrograph of a PEI-(PSS-PAH) 2 -(SiO 2 -PAH) 6 film;
- Fig. 6 a voltamogram obtained with a scan rate of 100 mV/s of a PEI-PSS- (PAH-silicic acid)3o film according to example 10 in contact with (a) ferrocene methanol; (b) ferrocyanide, (c) ruthenium (III) hexamine;
- Fig. 7 the absorbance spectrum of a composite film according to example 11 on a quartz substrate for different numbers of layer pairs;
- Fig. 8 absorbance at 232 nm (o, left scale) and at 450 nm ( ⁇ , right scale) of a composite film according to example 11 as a function of the number of layer pairs and film layer thickness increase ( ⁇ , right scale);
- Fig. 7 the absorbance spectrum of a composite film according to example 11 on a quartz substrate for different numbers of layer pairs
- Fig. 8 absorbance at 232 nm (o, left scale) and at 450 nm ( ⁇ , right scale) of a composite film according to example 11 as a
- silica Number 24,305-1 , Mw « 70000 g/mol) and poly(allylamine hydrochloride) (PAH, Aldrich, Cat. Number 28, 322-3, Mw « 70000 g/mol) were used without further purification.
- Silicic acid was purchased from Riedel De Haen (ref 13729, lot 1219A), in the form of water glass. All films were made with polyelectrolytes and chemical species dissolved in 0.05 mol.L "1 Tris(hydroxymethyl amino methane), the pH of which was adjusted to 7.4. The pH of the silicic acid solution had to be adjusted again to 7.4 with concentrated hydrochloric acid after the dissolution of silicic acid whose mother solution contained 11 % NaOH. This high pH of the mother solutions prevents spontaneous polycondensation to produce some silica.
- Concentration range of the silicic acid and Ti(IV)(bisammonium lactate) dihydroxyde solutions The concentration range of silicic acid that allows to spray monomers or small oligomers of silicic acid alternately with a polycation was defined by following the turbidity changes of silicic acid (at pH 7.4) as a function of time at a wavelength of 350 nm (at which neither silicic acid nor silica absorb light).
- An increase in turbidity means that colloidal silica particles are formed in solution. Such colloidal particles would then also form in the bottles in which silicic acid is stored before spraying.
- Silicic acid solutions with a concentration between 0 and 0.04 M were prepared in a 0.05 M Tris buffer. After adjustment of the pH to 7.4, they were introduced into a 1 cm path quartz cuvette and the absorbance followed as a function of time at a wavelength of 350 nm with a time resolution of 1 min during at least three hours. This duration corresponded to the longest spray experiments.
- any increase in absorbance corresponds to light lost by scattering and hence reflects the spontaneous appearance of silica particles.
- turbidity evolution with time is represented for different concentrations of silicic acid in Fig. 1. It appears that colloidal particles are not formed for at least two hours as long as the silicic acid concentration is lower than 0.02 M. This duration is sufficient to deposit more than 40 pairs of silicic acid - PAH deposition. The fact that turbidity of the solution remains close to zero does not allow us to exclude that some small silica oligomers are growing in solution.
- TiO 2 namely Ti(IV)(bisammonium lactate) dihydroxyde
- its solution displayed no absorbance increase at a wavelength of 500 nm for at least 10 hours and for Ti(IV)(bisammonium lactate) dihydroxyde concentrations as high as 0.1 M.
- the thickness of the grown silicon oxide film atop the silicon substrate was measured by means of ellipsometry (Jobin Yvon, model PZ 2000, France) at a constant angle of incidence (70") after nitrogen drying. At the working wavelength of 632.8 nm, the refractive index of silicon oxide was taken equal to 1.465. A single one layer Fresnel model was used to evaluate the data.
- the silicon wafer was hydrated again and immersed in a 0.5 mg/mL positively charged PEI solution during 5 min to allow for the deposition of a primer polyelectrolyte later.
- the substrate was then immobilised in a close to vertical orientation and hold with a tweezer on its upper part to allow for optimal liquid drainage upon spraying.
- the (PSS-PAH) 5 polyelectrolyte multilayer film was then deposited by spraying each polyelectrolyte solution (at 0.5 mg/mL in 0.05 M Tris buffer) during
- the thickness of the PEI-(PSS-PAH) 5 multilayer was then determined by means of ellipsometry after water rinse (to avoid the appearance of crystals from the buffer molecules) and drying under a nitrogen flow.
- the deposited film was assumed to have a refractive index of 1.465, which in the case of PEI-(PSS-PAH) 5 is very close to the values obtained in situ by means of Brewster angle reflectometry and optical waveguide lightmode spectroscopy.
- a composite silica-polycation film was deposited by alternately spraying a silicic acid solution at 10,8 mM and a polycation solution of polyallylamine hydrochloride
- Tris buffer was sprayed during 5s to wash away any non reacted and deposited species. Buffer drainage was also allowed during 15 s.
- the silicon chip with the deposited material was water rinsed, dried with a nitrogen flow, and characterized by ellipsometry every two deposition-reaction cycles, where a deposition-reaction cycle corresponds to the spraying of silicic acid and the polycation.
- a deposition-reaction cycle corresponds to the spraying of silicic acid and the polycation.
- the film was rehydrated again with a short pulse (about 2s) of Tris buffer spray.
- the total thickness of the obtained composite was then compared to the thickness of a PEI-(PSS-PAH) 5 film onto which two deposition-reaction cycles were performed five times with intermediate drying steps. Every value of the film thickness corresponds to the average over 5 measurements performed on regularly spaced points along the main axis of the rectangular silicon chip along which solution drainage occurred.
- example 1 was repeated by varying the concentration of the silicic acid between 0 and 25 mM.
- example 1 Preparation of a silicic acid-PAH composite film by dipping and characterisation by ellipsometry
- example 1 is repeated, except that instead of spray coating, the silicic acid and PAH are deposited alternatively by the classical dipping method.
- the evolution of the optical thickness was measured by ellipsometry, according to the procedure described above. The results are illustrated on Fig. 2b.
- the thickness increment per layer is smaller (5.7 ⁇ 1.0 nm per layer pair) than by the spray deposition method (11.0 ⁇ 1.5 nm per layer pair).
- the optical thickness of the film remains constant and equal to its value at the end of the first silica deposition (Fig.2A (•)). This can be explained by the hypothesis that that the excess of amino groups afforded by the polycation deposition induces the polycondensation from silicic acid provided by the spray. If some charge reversal occurs then (silica particles will be negatively charged at pH 7.4) the reactive layer by layer spray coating could be continued. Indeed electrostatic layer-by-layer coating is driven through charge inversion at each coating step.
- a film having the following layer structure is obtained: PEI-(PSS-PAH) 12 - (silicic acid-PAH)i2-(PAH-PSS)i 2 .
- the thickness increment per layer of the top film (0.83 nm per layer) is very close to the thickness increment per layer in the PEI-(PSS-PAH) 5 precursor film (0.78 nm per layer) and significantly different from the optical thickness increment in the reactive silicic acid-PAH deposition (1.9 nm per layer).
- the example 1 is repeated, except that the polycation solution of PAH is replaced by a polycation solution of polydiallyldimethyl ammonium chloride (PDADMAC) of the same concentration. Further, a silicic acid solution of a concentration of 10.8 mM is used.
- PDADMAC polydiallyldimethyl ammonium chloride
- the evolution of the optical thickness was measured by ellipsometry, according to the procedure described above. The results are illustrated on Fig. 3.
- the thickness increment of the PDADMAC - silicic acid composite film is 5.6 nm/layer.
- the thickness increment of a film obtained with a PAH solution in the same conditions is 6.0 nm/layer.
- the example 1 is repeated, except that the polycation solution of PAH is replaced by a polycation solution of polyethylene imine (PEI) of the same concentration. Further, a silicic acid solution of a concentration of 10.8 mM is used.
- PEI polyethylene imine
- the evolution of the optical thickness was measured by ellipsometry, according to the procedure described above. The results are illustrated on Fig. 3.
- the thickness increment of the PEI - silicic acid composite film is 4.3 nm/layer.
- the evolution of the optical thickness was measured by ellipsometry, according to the procedure described above. The results are illustrated on Fig. 3.
- the thickness increment of the poly-L-lysine - silicic acid composite film is 2.3 nm/layer.
- the surfaces were imaged in the contact mode with a Nanoscope IV microscope (Veeco) using silicon nitride cantilevers and tips with a nominal spring constant of 0.05 N m "1 .
- the film was rapidly rinsed with distilled water, blown dry with a stream of nitrogen and scratched with an ethanol cleaned syringe needle.
- the film was then imaged dry (or wet in presence of a NaCI solution) in the contact mode in a scan direction perpendicular to the scratched line.
- the stability of the visualized structures was checked by allowing several scans over the investigated area.
- ESEM Environmental scanning electron microscopy Multilayer films were sprayed as previously described onto cleaned glass slides, air dried and subsequently sputter-coated (Hummer-Junior, Siemens, Germany) with gold. Secondary electron imaging was performed by using scanning electron microscopy FEI Quanta 400, FEI Company TM, Hillsboro, Or USA) operating in the high-vacuum mode with an acceleration voltage of the electrons of 30 kV.
- the precursor film was made from only one PEI and one PSS layer because it has been demonstrated that PSS-PAH multilayers build up from solutions of small ionic strength become rapidly impermeable when increasing the number of deposited pairs of layers (Fahrat, T., Schlenoff, J. B.
- a (PAH-silicic acid) 30 multilayer was deposited on top of this precursor film by means of alternately dipping the gold electrode in the PAH and silicic acid solutions.
- This deposition performed by alternatively dipping the gold electrode in the PAH and silicic acid solutions, is sufficient to build up a continuous film and the oxidation and reduction currents that may be measured are then due to electroactive species that permeate through the film.
- All electrochemical equipment used was purchased from CH instruments: it is made from a potentiostat model 604B with a Farraday cage linked to a regular 3 electrodes system.
- the Ag/AgCI/KCI (3 rnol.L "1 ) reference electrode and a platinum wire as counter electrode were coupled with gold working electrodes 2 mm in diameter.
- These gold working electrodes were cleaned before each experiment according to the following protocol: three polishing cycles with aluminum oxide powder solutions of 1 , 0.3 and 0.05 ⁇ m granulometry, respectively. Each polishing cycle lasted over 2 min. It was followed by ultrapure water rinsing and repeated two additional times and finally sonicating the electrode twice. Finally the working electrodes were stored in water.
- the working electrodes were submitted to an electrochemical treatment, consisting in applying 1000 complete cycles between 0.2 and 1.6 volts at a scanning rate of 10 V.s "1 .
- This electrochemical treatment was performed in a 0.5 mol.L "1 sulphuric acid solution.
- film deposition on treated working electrodes was performed by a conventional dipping layer-by-layer method, since it was impossible to control spray deposition on the 2 mm diameter gold electrodes.
- the precursor layer was formed by successive dipping in PEI (1 mg/mL) solution, buffer rinsing, dipping into a 0.5 mg/mL PSS solution and a final buffer rinse.
- the further deposition of a (PAH-(silicic acid) n -PAH film was then performed using a dipping Robot (Riegler & Kirstein GmbH, Berlin, Germany), as described in detail elsewhere (C.Porcel, Ph.Lavalle, V.Ball, G.Decher, B. Senger, J.-C. Voegel, P. Schaaf, Langmuir, 2006, 22, 4376-4383).
- the composite film is highly permeable to ferrocene methanol. Indeed, the oxidation and reduction peaks of ferrocene methanol are symmetric and spaced by about 70 mV which is characteristic of a quasi reversible behaviour.
- the permeation in the films as well as the release kinetics are rapid (quantitative release from the film is achieved in less than ten minutes when the ferrocene methanol solution is replaced by pure Tris buffer).
- a composite titanium dioxyde-polycation film was deposited by alternately spraying with Ti(IV)(bis ammonium lactate) dihydroxyde solution at 10 imM in a solution of 50 mM Tris buffer and a polycation solution of poly(diallyldimethylammoniunn chloride) (PDADMAC) which was kept at 0.5 mg/mL
- Ths buffer was sprayed during 5s to wash away any non reacted and deposited species. Buffer drainage and reaction between the species was then allowed during 15 s.
- the same film was coated onto a transparent quartz substrate.
- the results are shown in Fig.7. Il is noted that the film absorbance is very strong in the far UV region while it is weak in the visible region. Further, the absorbance at 232 nm as well as the optical thickness of the film increase linearly with the number of layer pairs (Fig. 8).
- the extinction coefficient of the films is (9 ⁇ 2) ⁇ 10 ⁇ 3 nm "1 .
- the thickness of the films obtained is remarkably homogeneous. Indeed, the thickness varies less than 10 nm over several cm 2 after coating with15 layer pairs, which leaves a film with a thickness of around 160 nm. This homogeneity is visible to the eye for the coated quartz glass.
- a film was prepared by immersing a quartz glass alternately into a PDADMAC solution and a solution of TiO 2 (mean particle size
- mineral oxide-polycation composite films by alternatively spraying precursors of mineral oxide such as silica and different polycations. These films have been characterised with respect to their morphology and chemical composition.
- the obtained material displays high permeability to negatively charged ferrocyanide but the permeability to positively charged ruthenium hexamine is modified which suggests that the films contain an excess of positively charged polycation chains that do not directly interact with the spray produced mineral oxide particles.
- This novel method of reactive layer by layer coating may be extended to different metal oxide precursors such as alkoxydes and should allow coating biomaterials with active bioceramics able to direct complex responses, like osteoconduction, in vivo.
- the films were prepared by alternately spraying solutions of PDADMAC (at 0.5 mg/mL), Tris buffer at pH 7.5, solutions of Ti(IV)(bisammonium lactate)(TiBislac) (at various concentrations between 0.5 and 40 mM) and finally Tris buffer again. These four spraying steps correspond to the deposition of a layer pair.
- PDADMAC 0.5 mg/mL
- Tris buffer pH 7.5
- Ti(IV)(bisammonium lactate)(TiBislac) at various concentrations between 0.5 and 40 mM
- a composite titanium dioxyde-polycation film was deposited by alternately spraying with titanium tetrabutoxide solution at 5 mM in absolute ethanol and a polycation solution of polyallylamine hydrochloride (PAH) which was kept at 0.5 mg/mL in 50 mM TRIS buffer at pH 8.5.
- PAH polyallylamine hydrochloride
- Each species was sprayed during 5s with an additional 15s of drainage. Between each deposition, absolute ethanol was sprayed during 5s to wash away any non reacted and deposited species. Buffer drainage and reaction between the species was then allowed during 15 s.
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EP08708836A EP2121060A1 (de) | 2007-02-08 | 2008-02-08 | Verfahren zur bereitstellung eines kompositfilms auf einem substrat |
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PCT/EP2008/051569 WO2008096008A1 (en) | 2007-02-08 | 2008-02-08 | Method for providing a composite film onto a substrate |
EP08708836A EP2121060A1 (de) | 2007-02-08 | 2008-02-08 | Verfahren zur bereitstellung eines kompositfilms auf einem substrat |
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