Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
  • C08J3/09—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in organic liquids
  • C08J3/091—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in organic liquids characterised by the chemical constitution of the organic liquid
• • A61F13/01—
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/04—Hollow or tubular parts of organs, e.g. bladders, tracheae, bronchi or bile ducts
  • A61F2/06—Blood vessels
• • 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
  • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
  • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
  • A61L15/22—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons containing macromolecular materials
  • A61L15/26—Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives thereof
• • 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
  • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
  • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
  • A61L15/42—Use of materials characterised by their function or physical properties
  • A61L15/425—Porous materials, e.g. foams or sponges
• • 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
  • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
  • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
  • A61L15/42—Use of materials characterised by their function or physical properties
  • A61L15/64—Use of materials characterised by their function or physical properties specially adapted to be resorbable inside the body
• • 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
  • A61L27/50—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
  • A61L27/56—Porous materials, e.g. foams or sponges
• • 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
  • A61L27/50—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
  • A61L27/58—Materials at least partially resorbable by the body
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F13/00—Bandages or dressings; Absorbent pads
  • A61F2013/00089—Wound bandages
  • A61F2013/00165—Wound bandages not touching the wound
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F13/00—Bandages or dressings; Absorbent pads
  • A61F2013/00089—Wound bandages
  • A61F2013/00217—Wound bandages not adhering to the wound
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F13/00—Bandages or dressings; Absorbent pads
  • A61F2013/00089—Wound bandages
  • A61F2013/00217—Wound bandages not adhering to the wound
  • A61F2013/00221—Wound bandages not adhering to the wound biodegradable, non-irritating
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F13/00—Bandages or dressings; Absorbent pads
  • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
  • A61F13/15577—Apparatus or processes for manufacturing
  • A61F2013/15821—Apparatus or processes for manufacturing characterized by the apparatus for manufacturing
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F13/00—Bandages or dressings; Absorbent pads
  • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
  • A61F13/51—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the outer layers
  • A61F13/514—Backsheet, i.e. the impermeable cover or layer furthest from the skin
  • A61F13/51401—Backsheet, i.e. the impermeable cover or layer furthest from the skin characterised by the material
  • A61F2013/51409—Backsheet, i.e. the impermeable cover or layer furthest from the skin characterised by the material being a film
  • A61F2013/51411—Backsheet, i.e. the impermeable cover or layer furthest from the skin characterised by the material being a film being impervious to fluids but not for air or vapours
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2375/00—Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
  • C08J2375/04—Polyurethanes

Definitions

• the present invention relates to a body tissue replacement product constituted by a degradable, flexible material comprising a synthetic polymer matrix having a porous structure.
• the general concept of this invention is to provide new products of varying rates of degradation. This can be achieved in different ways, one example of which is varying the molecular weight of the polymer.
• a material of low molecular wei ⁇ t degrades faster than one with high molecular weight and in accordance with this invention a balance of the molecular weight can be provided to obtain a material which on the one hand maintains structural integrity for a sufficient period of time and on the other hand will degrade at a sufficient rate to permit fast endothelization or epithelialization to take place.
• the present invention has for its main object to solve the problem outlined above while providing a body tissue replacement product which meets the requirements of its practical use.
• the invention provides a product, wherein the rate of degradation of the polymer of the matrix varies, with the distance from the exposed surface of the product.
• exposed surface refers to one o ⁇ two surfaces of the product to make it clear that the rate of degradation of the polymer varies throughout the thickness of the material as seen in a lateral direction.
• the exposed surface of the product is the surface facing the wound.
• a vascular prosthesis there are exposed two surfaces, one constituted by the lumen side of the product, the other facing the surrounding tissue.
• the rate of degradation may decrease or increase in the direction from one side to the other of the product.
• a wound dressing wh.e ⁇ ein it is desirable to have a higher degradation rate and higher pore size on the side of the dressing facing the wound, whereas it is desirable to use a polymer of lower rate of degradation or imdegradable and lower pore size on the outer side of the dressing to protect from e.g. bacterial invasion.
• a wound dressing which has higher degradation rate and lower po ⁇ e size such as 5-10 ⁇ m on the exposed face of the dressing, higher degradation rate and higher pore size such as 50-100 ⁇ m in the intermediate part of the dressing and nondegradable protective outer layer with porosity of an order of 1 ⁇ m.
• the product is in the form of a multilayered but integral material, wherein each layer independently of the others contains polymer of same rate of degradation.
• multilayering technique it is possible, as further outlined below, to build up a product by stepwise application and precipitation of layers wherein the desired gradient of degradation rate across the product will be obtained.
• a vascular prosthesis it is thus possible to arrange layers on the lumen side of the wall of the prosthesis containing polymers of a high degradation rate, to ensure rapid endothelization, some interior layers of the material containing polymer of lower rate of degradation so that the constructional integrity of the product will be maintained for a sufficient period of time.
• the degradation rate of the different layers may diminish outwardly from the center of the product or the product may contain at intervals layers of lower degradation rate alternating with layers of higher degradation rate.
• the multilayered varieties of the product of this invention can be prepared starting from a solution of a copolymer in a suitable solvent and coating a substrate with a uniform thickness of such solution .
• the initial layer resulting from coating the substrate is then precipitated by treating the coating to displace solvent present in the coating with a precipitating solution which comprises a fluid which is miscible with said solvent but functions as a precipitating non-solvent with respect to the polymer. This procedure is then repeated the desired number of times to form a multilayered material.
• the polymer used for preparing same can be any polymer useful in the context, viz. a polymer showing biocompatibility and in some cases blood compatibility and being degradab le in the desired manner when implanted. It is preferred, however, to use a copolyuretane, particularly a segmented copolyurethane.
• a solution containing less than 5% and especially less than about 3% by weight of polymer it is preferred to use a solution containing less than 5% and especially less than about 3% by weight of polymer. The lower limit is not critical but is preferably not less than 0,1% by weight.
• solvent there may be used any solvent having the ability to dissolve the polymer used, but preferred solvents are those selected f ⁇ om the group consisting of tetrahydrofurane, amide solvents and sulfoxide solvents. Among such solvents there may be mentioned in addition to tetrahydrofurane dimethylacetamide, dimethylformamide and dimethylsulfoxide.
• any fluid having the capacity to precipitate the polymer there may be used any fluid having the capacity to precipitate the polymer.
• a preferred solvent is water but also lower alkanols, such as ethanol, may be used, optionally in combination with water.
• segmented aliphatic polyurethanes or segmented aromatic polyurethanes may be used in applying the technique of this invention.
• segmented aliphatic polyurethanes or using another expression aliphatic segmented polymers may be conventionally prepared from aliphatic polyurethanes based on diisocyanates, e.g.
• 1,2-diisocyanatoethane 1,5- diisocyanato pentane, hexamethylene diisocyanate, methane diisocyanato pentane, 1,9-diisocyanato nonane, 1,8-diisocyanato octane, 1,4-diisocyanato butane, 4,4'-methylenebiscyclohexyl diisocyanate, lysine diisocyanate, 1,4-t ⁇ anscyclohexane diisocyanate, dimethyldiisocyanato silane, diethyldiisocyanato silane.
• polyols having average molecular weight within the range of 100 to 10 000, e.g. polyethylene adipate) , poly (tetramethylene adipate) , poly(1,4- cyclohexyldimethylene adipate) , poly(hexamethylene oxalate), poly(hexamethylene glutarate) , poly(E-aprolactone) , poly (tetramethylene oxide), poly(ethylene oxide), poly (1,2-propylene oxide).
• Chain extenders e.g.
• 1,4-butandiol 2,4,6-tris(dimethylaminomethyl) ⁇ henol glycerol, 3,6-dioxaoctane 1-8-diol, ethylene diol , diathylene diol, tetramethylene diamine, ethylene diamine, hexamethylene diamine, propylene diamine.
• copolyurethanes are conventionally formed by e.g. reacting a prepolymer such as a polyether diol, with a diisocyanate, and the product resulting from such reaction may then be chain extended by reacting with a diol or diamine.
• a prepolymer such as a polyether diol
• a diisocyanate such as a diisocyanate
• copolymers may be produced having preferred molecular weights and preferred viscosity in solution.
• the rate of degradation and porosity of the material prepared may be controlled.
• various polymers with different rate's of deg ⁇ adation can be used in the different layers.
• the selected polymer material is dissolved in a suitable solvent of the type indicated above and the proportions between polymer and solvent are suitably selected so as to give a percentage of solids in the resulting solution of less than 5% by weight and p ⁇ eperably less than 3% and suitably no less than 0,1% by weight.
• the coating solution is then used to coat a substrate to form an initial coating of uniform thickness.
• a substrate there may be used, any mechanical means of suitable tv ⁇ e. such as a metal or glass plate or a metal or glass mandrel, preferably coated with a resistant, plastic, such as polytetrafluoro ethylene.
• the coating can be provided by spraying, immersion or dipping or in some other conventional manner.
• the molecular weight of the polymer used in preparing the products of this invention can vary within fairly wide limits but when using polyurethanes the average molecular weight preferably lies within the range of from about 5x10 3 to 10 6 .
• a particularly preferred range is from about 2x10 4 to 3x10 5 .
• the tissue replacement product of this invention can be used in a multitude of medicinal applications.
• it can be used as a vascular graft, as a skin graft or as a wound dressing.
• it can be used as elastic membran for ear drum replacement, as elements for orthopedic surgery and as anticoagulant tubing for blood transfusion.
• the invention will now be further described by specific examples which, however, must not be construed to limit the scope of the invention.
• the casting device shown in the drawing includes a frame carrying a rotary cylinder A.
• the cylinder may be of sintered glass or its surface may be covered with polytetrafluoroethylene, viz. "FLUON", manufactured by ICI Limited, England.
• Cylinder A is arranged to be driven by an electric motor C through gears and a gear shaft B. The rotational speed of cylinder A can be easily adjusted for controlling the coating formed on the cylinder.
• the level of polymer solution is indicated at D.
• Example I Example I.
• the cylinder A is dip-coated at room temperature with a polymer solution, the polymer coating applied being then precipitated with a non-solvent possibly containing a minor amount of solvent. After the first layer of polymer is precipitated this procedure is repeated for the desired number of cycles to prepare superimposed layers of polymer coatings on the cylinder to produce a multilayered prosthesis material of the required mechanical strength and thickness. After the deposition of the desired number of layers on cylinder A the material produced is soaked in deionized water to remove all residual solvents and non-solvents, and the material may then be washed with ethanol and dried on the cylinder at for example 30°C in a vacuum oven.
• the average thickness of the individual polymer layer is in the range of about 0.01 to 0.2 mm, and the average pore size in the material prepared is in the range about 0.5 to 500 pm.
• the average pore size in the material prepared is in the range about 0.5 to 500 pm.
• the initial coating resulting from applying polymer solution on the substrate is precipitated by treating the coating to displace solvent present in the coating with a precipitating solution which comprises, as a major constituent, a fluid which is miscible with said solvent but functions as a precipitating non-solvent with respect to the polymer, and further comprising, as a minor constituent, a solvent for the polyurethane. This procedure is then repeated the desired number of times to form a multilayered material.
• the product or material of this invention may, of course, include reinforcing materials, such as materials in fibrous, woven or pleated form.
• Such reinforcing material may be degradable or non-degradable.
• the invention is not limited to the casting technique described above but other methods of applying the polymer solution onto a substrate may be used equally well. Thus, application by spraying is also useful and brushing technique is also conceivable. Example II.
• a series of casting solutions was prepared from polyester urethane based on hexamethulene diisocyanate, poly (hexamethulene glutanate)diol and 1,4-butane diol. Solutions were prepared from polyurethanes having molecular weights of 2x10 4 , 4x10 4 , 5x10 4 , 6x10 4 and 3x10 5 . These individual casting solutions contained 4, 3, 2, 2 and 1. by weight, respectively, of the said polyurethanes. Another casting solution is prepared by dissolving
• Esthane-polyether urethane (Trade Mark, Goodrich) in tetrahydrofurane at room temperature.
• the polymer solution is stirred fo ⁇ half an hour and is then filtered and stored in dark, closed bottles until use thereof.
• a wound dressing is manufactured according to the procedure outlined in Example I using a casting device provided with a cylinder made of sintered glass. In the casting procedure the cylinder is continuously flushed with deionized water. Water penetrates through the pores of the sintered cylinder causing uniform precipitation of the polymer on the surface of the cylinder.
• the upper layer made from non-degradable polyurethane ensures the proper fluid transport rate
• This layer is finally stripped off the rehealed wound.
• This artificial skin protects the wound for at least 20 to 60 days without rejection and without requiring an immune supression.
• Example II were used, namely that containing polyurethane of molecular weight 2 x 10 4 and that of molecular weight 3 x 10 5 .
• the procedure described in Example I is used for the manufacture using a mandrel rather than a cylinder.
• the prosthesis wall is composed of 30 layers of polyurethane having a molecular weight of 2 x 10 4 on the lumen side of the prosthesis and 3 x 10 5 on the opposite side of the prosthesis wall.
• the sixth eleventh, sixteenth, twentyfirst, twentysixth and the outermost layer are all made from polyurethane with a molecular weight of 3 x 10 5 .
• the other layers are made from polyurethane having a molecular weight of 2 x 10 4 .
• Using the polymer with a lower molecular weight results in higher rate of degradation. High rate of degradation is desirable to ensure rapid endothelization and growth of tissue.
• high molecular weight of the polymer results in lower rate of degradation. The degradation process of the prosthesis is thus slowed down so that its mechanical integrity will be maintained for a sufficient period of time to fulfil its function until newly grown tissue will impart sufficient mechanical stability where implantation has been made.
• Example IV Example IV.
• a polyether urethane having an average molecular weight of 4 x 10 5 based on 4,4'-methylene-biscyclohexyl diisocyanate, poly(tetramethylene oxide) and 1,4-butanediol is dissolved in tetrahydrofurane at room temperature and precipitated with water/ethanol(9-1v./v.). The precipitated polymer is washed with distilled water and dried under vacuum. The dried polymer is then dissolved in dichloromethane to produce a solution having a concentration of polymer of 2 % by weight. The polyurethane is precipitated with n-hexane and dried to constant weight.
• the polyurethane thus prepared is used for preparing a casting solution by dissolving the purified polymer in tetrahydrofurane at room temperature, the concentration thereof being 1.8 % by weight.
• Example I partially degradable vascular prostheses are prepared from the solution described above. However, before applying layers of polymer from such casting solution there are initially applied on the cylinder three layers from a casting solution containing degradable polyurethane of the type described in Example II but having an average molecular weight of about 3 x 10 4 . This will form a membrane having small pores in the range of 5-10 ⁇ m on top of which there are then applied 35 to 50 layers using the casting solution described initially in the present example. The average pore size of these additional layers is larger than that of the initial membrane and within the range 30-60 ⁇ m.
• vascular prostheses are prepared by casting on the mandrel 10 layers of solution B followed by depositing on these layers next 40 layers of solution A according to the procedure described in Example I as a mandrel instead of a cylinder.
• the endothelization process is enhanced while the remaining part of the prosthesis prepared from the other material having a lower rate of degradation maintains the required mechanical integrity of the prosthesis during the healing process.

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Citations (5)

• 1984
  • 1984-02-03 SE SE8400569A patent/SE448821B/sv not_active IP Right Cessation
• 1985
  • 1985-01-17 WO PCT/SE1985/000017 patent/WO1985003444A1/en unknown
  • 1985-01-17 AU AU38337/85A patent/AU3833785A/en not_active Abandoned
  • 1985-01-17 EP EP85900796A patent/EP0171410A1/en not_active Withdrawn
  • 1985-01-30 IT IT19297/85A patent/IT1184145B/it active

Patent Citations (5)

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