CA1295796C - Biodegradable matrix and methods for producing same - Google Patents
Biodegradable matrix and methods for producing sameInfo
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- CA1295796C CA1295796C CA000477358A CA477358A CA1295796C CA 1295796 C CA1295796 C CA 1295796C CA 000477358 A CA000477358 A CA 000477358A CA 477358 A CA477358 A CA 477358A CA 1295796 C CA1295796 C CA 1295796C
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- collagen
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- collagen matrix
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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
- 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
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
- A61K9/00—Medicinal preparations characterised by special physical form
- A61K9/70—Web, sheet or filament bases ; Films; Fibres of the matrix type containing drug
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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
- 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
- A61L15/32—Proteins, polypeptides; Degradation products or derivatives thereof, e.g. albumin, collagen, fibrin, gelatin
- A61L15/325—Collagen
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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
- 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
- A61L15/44—Medicaments
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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
- 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
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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
- A61L26/00—Chemical aspects of, or use of materials for, wound dressings or bandages in liquid, gel or powder form
- A61L26/0009—Chemical aspects of, or use of materials for, wound dressings or bandages in liquid, gel or powder form containing macromolecular materials
- A61L26/0028—Polypeptides; Proteins; Degradation products thereof
- A61L26/0033—Collagen
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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
- A61L27/14—Macromolecular materials
- A61L27/22—Polypeptides or derivatives thereof, e.g. degradation products
- A61L27/24—Collagen
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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
- A61L27/50—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
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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
- A61L27/50—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
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L89/00—Compositions of proteins; Compositions of derivatives thereof
- C08L89/04—Products derived from waste materials, e.g. horn, hoof or hair
- C08L89/06—Products derived from waste materials, e.g. horn, hoof or hair derived from leather or skin, e.g. gelatin
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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
- A61L2300/00—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
- A61L2300/20—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices containing or releasing organic materials
- A61L2300/23—Carbohydrates
- A61L2300/232—Monosaccharides, disaccharides, polysaccharides, lipopolysaccharides
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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
- A61L2300/00—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
- A61L2300/20—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices containing or releasing organic materials
- A61L2300/252—Polypeptides, proteins, e.g. glycoproteins, lipoproteins, cytokines
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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
- A61L2300/00—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
- A61L2300/20—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices containing or releasing organic materials
- A61L2300/252—Polypeptides, proteins, e.g. glycoproteins, lipoproteins, cytokines
- A61L2300/254—Enzymes, proenzymes
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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
- A61L2300/00—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
- A61L2300/40—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices characterised by a specific therapeutic activity or mode of action
- A61L2300/404—Biocides, antimicrobial agents, antiseptic agents
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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
- A61L2300/00—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
- A61L2300/40—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices characterised by a specific therapeutic activity or mode of action
- A61L2300/412—Tissue-regenerating or healing or proliferative agents
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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
- A61L2300/00—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
- A61L2300/40—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices characterised by a specific therapeutic activity or mode of action
- A61L2300/412—Tissue-regenerating or healing or proliferative agents
- A61L2300/414—Growth factors
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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
- A61L2300/00—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
- A61L2300/40—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices characterised by a specific therapeutic activity or mode of action
- A61L2300/432—Inhibitors, antagonists
- A61L2300/434—Inhibitors, antagonists of enzymes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S128/00—Surgery
- Y10S128/08—Collagen
Abstract
Abstract of the Disclosure There are disclosed processes for preparing biodegradable collagen-based matrices in sponge or sheet form wherein in one embodiment a collagen-based material including a collagen selected from the group consisting of types I, II and III collagens is freeze dried to form a collagen-based sponge which is contacted with a cross-linking agent selected from the group consisting of a carbodiimide or a succinimidyl active ester to form an intermediate collagen-based matrix which is subsequently subjected to conditions of severe dehydration to form the collagen-based matrix in sponge or sheet form. In another embodiment, a collagen-based sponge or sheet is first subjected to conditions of severe dehydration followed by contacting the thus formed intermediate collagen-based matrix with a carbodiimide crosslinking compound to form the collagen-based matrix in sponge or sheet form. In still another embodiment of the present invention the crosslinking agent is admixed with the collagen-based material prior to formation of the collagen-based sponge or sheet followed by processing steps of severe dehydration. In a particularly preferred form of the invention, a carrier compound is incorporated during processing to form a collagen-based matrix in sponge or sheet form impregnated with a carrier compound wherein the carrier compound is selected from the group consisting of types IV and V collagen, fibronectin, laminin, hyaluronate, proteoglycan, epidermal growth factor, platelet derived growth factor, angiogenesis factor, antibiotic, antifungal agent, spermacidal agent, enzyme and enzyme inhibitor.
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Description
S7~
BIODEGRAD~BLE MATRI~ AND
METHODS FOR PROD~CING SA~R
Field of the Invention This invention relates to a biodegradable matrix, and more particularly to a multifunctional collagen-based matrix and/or carrier system thereof.
Background of the Invention .
Delivery of drugs, growth factors, hormones, peptides and glycopeptides to external wounds has classically occurred by direct topical application and application to internal wounds by injection into the blood or by absorption into the blood through the digestive system. Controlled release of these agents has been achieved by encapsulation either in bulk or at a microscopic level using synthetic polymers, such as silicone, and natural polymers, such as gelatin and cellulose. The release rate can be controlled for periods of up to a year by proper choice of the polymeric system used to control the diffusion rate (Langer, R.S.
and Peppas, N.A., Biomaterials 2, 201,1981). Natural polymers, such as gelatin and cellulose slowly dissolve in a matter of minutes to hours while silicone remains intact for periods of months to years. Biodegradable polymers offer an advantage for controlled release to internal wounds since only a single surgical procedure is necessary.
.
7g6 Collagen is a biodegradable polymer found in animals and in man. It has been used as a plasma expander, vehicle for drug delivery, vitreous body replacement, hemostatic agent, suture material, corneal replacement, hemodialysis membrane, wound dressing and artificial skin, hernia patch, vessel prosthesis, vaginal contraceptive, and injectable agent for tissue augmentation (Chvapil et al., Int. Review of Connective Tissue Research 6, 1, 1973; Chvapil, in Biology of Collagen edited by A. Viidik and 3. Vuust, Academic Press, chapter 22, 1980). In most of these applications, the collagen is reconstituted and crosslinked into an insoluble form.
There is described in Yannas et al, (U.S. patent 4,060,081), the use of collagen and mucopolysaccarides as synthetic skin. Such material is crosslinked using glutaraldehyde, a bifunctional crosslinking agent, which reacts with free amines. One major drawback to using crosslinked collagen has been the adverse biological effects of free glutaraldehyde, a common agent used to crosslink and insolubilize collagen in many applications.
Leaching of glutaraldehyde from crosslinked collagens has been shown to be cytotoxic to cells, specifically fibroblasts (Speer et al., J. Biomedical Materials 25 Research 14,753,1980; Cooke et al., British J. Exp. Path. -64,172,1983). Recent evidence suggests that glutaralde-hyde polymers and not monomeric glutaraldehyde form crosslinks between collagen molecules; these crosslinks can then rearrange to release free glutaraldehyde and glutaraldehyde :1S ~`
polymers (Cheung, D.T. and Mimni, M.D., Connective Tissue Research 10, 187-217,1982).
Summary of the Invention The present invention provides in one embodiment a sponge or sheet of a collagen-based material including a collagen selected from the group consisting of types I, II and III collagens which sponge or sheet is contacted with a cross-linking agent selected from the group consisting of a carbodiimide or a succinimidyl active ester to form an intermediate collagen-based matrix which is subsequently subject:ed to conditions of severe dehydration to form a collagen-based matrix in sponge or sheet form. In another embodiment, the sponge or sheet of the collagen-based material is first sub~ected to conditions of severe dehydration followed by contacting tha thus formed intermediate collagen-based matrix with a carbodiimide cross-linking compound to form the collagen-based matrix in sponge or sheet form. In still another embodiment of the present invention, the cross-linking agent is admixed with the collagen-based material prior to formation of the intermediate collagen-based sponge or sheet followed by processing steps of severe dehydration. In a particularly preferred form of the invention, a carrier compound is ~5'~
incoxporated into the collagen based material during processing to form a collagen-based matrix in sponge or sheet form impregnated with a carrier compound wherein the carrier compound is selected from the group consisting of types IV and V collagen, fibronectin, laminin, hyaluronate, proteoglycan, epidermal growth factor, platelet derived growth factor, angiogenesis factor, antibiotic, antifungal agent, spermicidal agent, enzyme and enzyme inhibitor.
According to another aspect of the invention, a method of preparing a cross-lin:ked collagen matrix where the collagen in said matrix is selected from the group consisting of Types I, II and III collagen, said method comprising treating said selected collagen by carrying out one of the following steps (a) and (b) and following with the other:
a) contacting said selected collagen with a cross-linking agent selected from the group consisting of a carbodiimide, a bifunctional succinimidyl active ester and mixtures thereof; and b~ subjecting said selected collagen to elevated temperatures under a vacuum.
According to another aspect of the invention, a cross-linked collagen matrix which was cross-linked by chemical cross-linking a~d cross-linked by subjecting the collagen to elevated temperatures under a vacuum.
.~
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Detailed Description of the Invention The collagen-based carrier systems of the present invention are based on the use as a starting material of a soluble or insoluble collagen selected from the group consisting of types I, II and III collagens and mixtures thereof.
Soluble collagens of the types I, II and III
collagen are prepared by limited enzymatic digestion of tissue enriched in such collagen types and are formed into collagen-based solution (i.e., a soluble collagen dissolved in a suitable solvent, such as dilute hydrochloric acid, dilute acetic acid or the like).
Insoluble collagens are derived from the following typical sources: type I collagen; bovine, chicken and fish skin, bovine and chicken tendons and bovine and chicken bones including fetal tissues; type II collagen;
bovine articular cartilage, nasal septum, sternal cartilagej and type III collagen; bovine and human aorta and skin.
In one embodiment of the present invention, a collagen-based solution or an insoluble collagen dispersed and swollen in a suitable liquid medium (e.g.
dilute hydrochloric acid, dilute acetic 57~6 acid or the like) is subjected to a temperature of between about ooc. to -100Co to thereby solidify the collagen-based material. Thereafter, the solidified collagen-based material is subjected to a vacuum o~
less than about 50 millitorr at a temperature of from about 22C. to -100C. to form a collagen-based sponge to be further processed, as hereinafter more clearly described. Generally, a weight ratio of soluble or insoluble collagen to solvent or dispersion agent, respec~ively, of from 1 to 10,000 or ~rom 1 to 15 is used to form the collagen-b2ised solution or dispersion.
In another embodiment of the present invention such a collagen-based solution o~ a collagen-based dispersion is dried into sheet Porm prior to further processing as more fully hereinafter described. Dryiny is ef~ected at temperatures o~ from 4C. to 40C for a period of time of from ~ to 48 hours.
In one embodiment of the present invention to form a collagen-based matrix, a collagen-based sponge or sheet is first contacted with a crosslinking agent selected from the group consisting of a carbodiimide or N-hydroxysuccinimide deriv~d active esters (succinimidyl active ester) ~ollowed by severe dehydration to form the collagen-based matrix.
Examples o~ the carbodiimides include cyanamide and l-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride. Examples o~ bifunctional succinimidyl active esters including bifunctional ~-hydroxysuccinimide, 3,31-dithio (sulfosuccinimidyl) propionate and bis ~sulfosuccinimidyl) suberate. When using a carbodiimide crosslinking agent, the collagen-based sponge or sheet ., "
9~
is immersed in a carbodiimide solution at a concentration of from about 0.1 to 10% (W/V) maintained at a temperature of from about 2 to 40C. and at a pH of between 2 to 11 for a period of time of from about 2 to 96 hours. When using a succinimidyl active ester crosslinking agent, the collagen-based sponge or sheet is immersed in a solution thereof at a concentration of from about 0.1 to about 15.0~ ~W/V) maintained at a temperature of ~rom about 2 1:o 40C. for a period of time of from about 2 to g6 hours. The collagen-based sponge or sheet is placed in a solution containing 0.1 to about 15% (W/V) o~ N-hydroxysuccinimide and carbodiimide at a pH between 2 to 11 for a period of time between 2 to 96 hours at a temperature of from about 2~C. to 40C. The thus treated intermediate collagen-based matrix is exhaustively washed to remove excess crosslinking agent.
Severe dehydr~tion of the in~ermediate collagen-based matrix inv~lve# conditions of temperature of from 50C. to 200C. at a vacuum of 50 millitorr or less for a period of time of from 2 to 96 hour~ to thereby form the collagen-based matrix. Prior to severe dehydration, the intermediate collagen-based matrix in sponge form is preferably solidified at a temperature of between about 0C. to -100C. and thereafter subjected to a vacuum of at least 50 millitorr at a temperatura of between about 22C. and -lOO~C.
In another embodiment of the present invention to form the collagen based matrix when using a c~rbodiimide crosslinking agent, severe dehydration may be effected to form an intermediate collagen-based matrix prior to contacting such an intermediate collagen-based matrix with such a crosslinking agent.
~ ~"
In another embodiment of the present invention to form the collagen-based matrix, the cross-linking agent is premixed with the collagen-based material prior to drying or initiating of freeze drying processing steps.
The collagen-based matrix prepared in accordance with the present invention may be described as a "coral-like" or "scaffold" structure having interstices of a pore size of from 3 to 100 ~m., and of a molecular weight of from 10 X 106 to in excess of 50 X 106 with a molecular weight between crosslin~s from 1,000 to 100,000 via the formation of covalent bonds.
Another embodiment of the present invention is the incorporation of a carrier compound into the collagen-based matrix. Such a carrier compound is selected from the group consisting of collagen types IV and V, fibronectin, laminin, hyaluronate, proteoglycans, epidermal growth factor, platelet derived growth factor, angiogenesis factor, antibiotic, antifungal agent, spermacidal agent, hormone, enzyme and enzyme inhibitor.
Generally, the carrier compound may be introduced at any time during processing of the collagen-based material to the collagen-based matrix in sponge or sheet form.
Preferably, a carrier compound is incorporated prior to solidifying of the soluble or insoluble collagen in forming the intermediate collagen-based matrix, or prior to solidifying of the intermediate collagen-based matrix prior to severe dehydration. The carrier materials are added in an amount of from 1 to 30% (w/w) based on the weight of soluble or insoluble collagen. Generally, connective .
~2~7g~
tissue factors, such as fibronectin, types IV and V
collagens, lamini~, glycosaminoglycans and hyaluronate are incorporated during initial processing steps in forming the collagen-based sponge or after crosslinking of the intermediate collagen-based matrix. It is preferable to incorporate fibronectin and hyaluronate during forming of the intermediate collagen-based matrix.
There are many sources for the diverse carrier compounds for incorporation into the collagen-based matrix constituting one embodiment of the present invention. Type IV and V collagens are found associated with basement membranes and smooth muscle cells in tissues, respectively. Typical sources of Type IV
include the EHS mouse sarcoma tumor, bovine and human placenta, lens capsule and kidney; sources of Type V
collagen include placental membranes, ocular tissues and fetal skin (see for example, Trelstad, In Immunochemistry of the Extracellular Matrix, Vol. 1 edited by H. Furthmayr, CRC Press, chapter-2, 1982).
Typical sources of proteoglycans include bovine and human cartilage and synovial fluid, nasal s~ptum and sternal cartilage, and skin. Typical sources for glycoproteins include EHS tumor, bo~ine and human kidneys, cartilage, bone and placenta as well as bovine and human blood. Typical sources of hyaluronate include rooster comb and bovine vitreous.
Preferred carrier compounds for the collagen-based matrix include fibronectin, laminin, type IV collagen and complexes of hyaluronate and proteoglycans. A value of the swelling ratio of between 2.5 to 5 is required for a collagen-based matrix which . ~
.~
~Z~ 36 comes into contact with open wounds, while a swelling ratio of between 2.5 to 10 are useful for a collagen-based matrix including carrier compounds for subcutaneous implantation. The swelling ratio is de.fined as the volume of water absorbed per unit volume of collagen-based matrix.
In the case of internal ~ounds and short-term drug release, collagen-based matrix including a carrier compound in the form of a she~et or a tube is placed in direct contact with tissue.
The biodegradation rate and the release rate can be controlled by variation of thle crosslink density. For applications where long term release is desired, a nonporous diffusion layer of a biodegradable polymer, such as poly-3-(hydroxybutyrate) is applied to each side of the collagen-based matrix. For materials to be used on full thickness wounds, a diffusion control layer, such as described in the aforementioned U.S. Letters Patent to Yannas, is applied to prevent diffusion of water or other small volatile molecules from the collagen-based matrix; the diffusion control layer must adhere tightly to the collagen-based matrix layer. The combination of collagen-based matrix layer and diffusion control layer must be strong enough to be sutured and have a tensile strength of at least 100 psi and be able to deform at least 10% before failing. Synthetic non-biodegradable polymers, such as silicone polymers (Silastic Medical Grade Adhesive~) or biodegradable polymers, such as polylactic acid, polyglycolic acid, poly-3-(hydroxybutyrate) and copolymers of these materials can be used as the diffusion control layer.
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.. . ..
7~6 Silicone polymers are preferred materials to control the rata of diffusion of small molecules.
Curing of the adhesive in the diffusion control layer can occur without wetting the carrier compound in tne collagen-based matrix by desiccation at room temperature. A film 0.5 to 1.5 mm in thickness is applied to the matrix layer and is allowed to cure at room temperature for at least 2 hours using a vacuum of 14 in. of Hg.
The thickness of the collagen-based matrix can be varied from 1 to several hundred mm. For full thickness wounds, a thickness of 2 to 3 mm is dasired and enablas close contact between the carrier compound in the collagen-based matrix and the wound bed.
When implanted subcutaneously or directly on full thickness dermal wounds, any collagen-based matrix of the present invention does not stimulate the inflammatory process. In addition, chronic implantation results in fibroblast and endothelial cell migration into the collagen-based matrix. The degradation and resorption rate of collagen-based matrices are as assayed in vitro by determination of the time that 1 mg of the material resists solubilization by lOO units o~
bacterial collagenase. One unit of collagenase liberates amino acids in collagen e~uivalent to 1.0 micro mole of L-leucine in 5 hours at 37C. A
combination of succinimidyl active ester formation and severe dehydration or carbodiimide treatment and severe dehydration increases the collagenase resistance time significantly over that observed by any of the procedures heretofore used. These studies indicate that the crosslinking methods of the present invention result in resistance to collagenase dagradation and show no stimulation of inflammation.
:L2~S7~f~
EXAMPLES OF THE INVENT:CON
The following examples are illustrative of conditions for the process of the present invention and it is to be understood that the scope of the invention is not to be limited thereby.
Preparation of Soluble and Insoluble Collagens The collagen used is prepared from calf hides after the grain layer is separated from the corium or dermis.
The corium is cut into pieces, washed, swollen, freeze dried and stored at -20C.
Soluble collagen is obtained by placing 250 gr of the freeze dried insoluble collagen in 1.5 liters of HCl at a pH of 2.5 containing 1.5 gr of crystalline pepsin (Sigma Chemical Company). The mixture is stirred overnight at 4~C. and then filtered through cheese cloth, Whatman~ filter paper #4 followed by Whatman #42, Gelman 5 ~m and 1.2 ~m filters and finally through Millipore~ 0.65 ~m and 0.45 ~m filters. ~he soluble fraction obtained after sequential filtration contains types I, III and V collagens. The soluble collagen fraction is dialyzed against a 1.0 M NaCl solution containing 50 mM Tris [tris(hydroxymethyl)aminomethane buffering agent] adjusted to pH 7.5 and enough solid NaCl is àdded to raise the molarity of the solution to 1.7. The precipitate at 1.7 M NaCl is type III
collagen and is collected by centrifugation at 10,00 x g for 60 minutes and then dialyzed versus 0.005 M
acetic acid, freeze dried and stored at -20~C. To the supernatant is added additional NaCl to raise the molarity to ~29~i7~36 2.5 M and the precipitate (type I collagen) is pelleted by centrifugation, dialyzed versus 0.005 M acetic acid, freeze dried and stored at -20C. The remaining supernatant contains type V collagen and is dialyzed against 0.005 M acetic acid, freeze dried and stored at -20C.
Insoluble collagen solutions are obtained by dispersing freeze dried corium ground using a Wiley Mill in HCl at pH of 2.5. The swollen collagen is then dialyzed against 0.005 M acetic acid and freeze dried.
If mature bovine hide is the source of the corium, the insoluble collagen produced is typically type I.
Soluble type IV collagen is extracted from the mouse EHS sarcoma tumor after washing the tumor in cold distilled water 3 times by spin filtration at 10,000 x g for 30 minutes. The pellet (0.500 gr) is homogenized in 0.5 liters of 0.5 M acetic acid adjusted to pH 2.5 with HCl and 0.5 gr of pepsin is added. The homogenate is allowed to mix at 4C. for 24 to 48 hours, filtered through cheese cloth, spun at 10,000 x g for 30 minutes.
The pellet is re-suspended in 0.5 M NaCl containing 50 mM
Tris, NaCl is added until a final concentration of 4.5 M
is obtained, centrifuged at 10,000 x g for 30 minutes and the pellet is dialyzed against 0.1 N acetic acid 3 times and freeze dried.
EX~MPL~ 2 Preparation of Bovine Serum Fibronectin Freshly drawn bovine blood (80 ml) is collected in a polypropylene tube containing 20 ml. of 5% trisodium citrate and ~35796 O.1 mM phenylmethysulfonyl fluoride. The blood is centrifuged at 300 x g for 10 minutes and the plasma is then separated from the cell layer and further centrifuged at 30,000 x g at a temperature of 15C. for 30 minutes. To the plasma is then added an additional 1 mM of phenylmethylsulfonyl fluoride and then it is poured through a gelatin-sepharose col~mn. The column is washed with a phosphate buffer solution (0.182 M phosphate and 0.145 M NaCl), 2 column volumes of lM NaCl in a phosphate buffer, 2 column volumes of phosphate buffer solution, 2 column volumes of 4 M urea in a phosphate buffer. The optical density of column fractions is monitored at a wavelength of 280 nm with the bulk of the fibronectin normally present in the fractions containing 4 M urea.
Fibronectin containing fractions having optical densities greater than 0.1 are dialyzed against 0.180 M phosphate buffer containing 0.145 M Nacl (pH 7.2). The sample is then dialyzed against 0.05 M Tris-HCl containing 4.5 M
urea ~pH 7.2) and applied to a DEA (diethylaminoethyl cellulose) ion exchange column at room temperature. The column is eluted with a 0 to 0.3 M NaCl linear gradient in a 0.05 M Tris-HCl buffer solution (pH 7.2) containing 4.5 M urea. The eluted fibronectin is dialyzed against 0.180 M phosphate containing 0.145 M NaCl and 1.0 M urea and frozen at -20C.
~L295~
Preparation of Laminin Laminin is prepared ~or lathrytic EHS tumors grown C57/6J mice. The tumors are dissected and homoganized in 3.4 M NaCl containing 50 mM Tris-HCl adjusted to pH
7.4 and protease inhibitors. The homogenate is centrifuged at 16,000 x g for 60 minutes and the pellet is collected and resuspended in 3.4 M NaCl. Following centrifugation at 16,000 x g for 60 minute~ a second time, the homogenate is resuspended in 0.5 M NaCl containing 50 mM Tris-HCl pH 7.4 and protease inhibitors stirred for 18-24 hours at 4C. followed by centrifugation at 16,000 x g ~or 60 min. The supernatant is brought to 3.5 M by addition of solid NaCl, stirred overnight at 4C. and the precipitate is collected by centrifugation. Laminin is ~urther purified by redissolving in 0.5 M NaCl containing 50 mM
Tris-HCl pH 7.4 followed by centrifugation at 10,000 x g for 60 minutes the supernatant is dialyzed against 2 M
urea containing 2.5 NaCl and 50 mM Tris-~Cl pH 8.6 and chromatographed over a 2.5 x 2.5 cm column containing DEAE cellulose eguilibrated with the same bu~fer at 4C.
The unbound fraction is dialyzed against 2 M urea containing 50 mM Tri~-HCl pH 8.6 and rechromatographed on the DEAE~ column eguilibrated with the same buffer.
The unbound fraction is concentrated by vacuum dialysis and chromatographed on Sephacryl S-300~e~uilibrated with _ _ __ ~2~57~6 1.0 M CaCl2, 50 mM Tris-HCl pH 7.5 at 22C. the void volume is collected and dialyzed against 0.4 M NaCl, 50 mM Tris-Hcl pH 7.4 and stored at 4C. Laminin is resolubilized in 0.1 M ammonium hydroxide pH 11.0 and then the pH is adjusted to 7.2.
Preparation of Collagen-based Sponges and Sheets Soluble or insoluble collagen (1.2 gr.) is added to 120 ml. of a dilute HCl solution of pH 3.0 and the mixture is ground in a Wariny Blender at low speed for 1 minute and thereafter at high speed for 1 minute. The solution or dispersion is then poured into a vacuum flask and deaerated at a vacuum of 100 millitorr for 10 minutes. Collagen dispersions and solutions to be converted into sponges are cooled to 0C. and frozen at -100C. before freeze drying at -65C. under a vacuum of less than 10 millitorr. Collagen dispersion or solutions to be processed into sheets were placed in a sterile hood and allowed to air dry for 2~ to 48 hours at 22C.
EX~MPL~ 5 Preparation of Succinylated, Succinimidyl Ester Crosslinked Intermediate Collagen-Based Matrix Nine grams of succinic anhydride are dissolved in 80 ml. of distilled water and mixed for 30 minutes at 37C.
After the succinic anhydride is in solution, the pH is adjusted to 7.2 and the volume brought to 100 ml. This solution is placed in a Waring t7~6 Blender and 1.0 gr of collagen is added, ground ~or 2 minutes allowed to stand at 22C. for 1 hour, placed on Whatman #4 filter paper to remove unreacted succinic anhydride and then washed with 100 ml o~ distilled water.
The residue is placed in a solution o~ 20 ml of phosphate buffer (0.182 M phosphate and 00145 M NaCl) and 2 gr of N-hydroxysuccinimide and 2 gr of cyanamide are added. The solution pH :is then adjusted to 7.2.
The residue is allowed to react for 3 hours at room temperature and then washed with distilled water in a Buchner funnel under a vacuunn of 14 in. of Hg. Sheets and sponges of succinylated, succinimidyl ester crosslinked intermediata collagen-based matrices are produced in acrordance with the processes described in Example 4.
Preparation of Collagen-3asèd Matrix Containing Fibronectin 20To 1.2 gr solubls or insoluble collagen in 120 ml of HCl pH 3.0 is added to 0.12 gr of fibronectin in (2.5 mg. fibronectin/ml) 0.1 M urea containing O.la2 M
phosphate and 0.145 ~ NaCl and the mixture is dispersed ~ _n a ',~aring Blender~ for 2 minutes. Sheets and sponges are prepared in accordance with the processes described in Example 4.
~;~9~;~96 Sponges and Sheets Formed by Coating Type I Collagen With Laminin, Fibronectin, and Type IV Collagen Collagen sheets and sponges formed according to Examples 4 and 6 are swollen in a 0.1 ammonium acetate pH
7.2 containing 1 to 5~ laminin, fibronectin or type IV
collagen. The swollen sponge or sheet is then frozen and freeze dried at -56C. and in a vacuum less than 50 millitorr.
Preparation of Collagen-Based Matrix Containing Hyaluronate and Proteogycans To 1.2 gr. of soluble and insoluble collagen in HCl pH 3.0 as added to 0.12gr. of a complex of hyaluronate and proteoglycans (Sigma Chemical Company Grade III-P~ in a HCl pH 2.0 to a final volume of 120 ml. The mixture is dispersed in a Waring Blender and eith~r freeze dried or air dried in accordance with the processes of Example 4.
EXAMPL~ 9 Preparation of Collagen-Based Matrix Containing Type IV Collagen To 1.2 gr. of soluble or insoluble collagen type I
in HCl pH 2.0 is added to 0.012 gr. of type IV collagen in a 0.1 M ammonium acetate pH 7.2 to a final volume of 120 ml. The mixture is ~95796 dispersed in a Waring Blender for 2 minutes and formed into sheets or sponges in accordance with the processes of Example 4.
Cyanamide Crosslinking of Collagen-Based Matrix The product of Examples 4 and 6 to 9 are crosslinked by immersion in an aqueous solut:ion containing 1% by weight of cyanamide at pH 5.5 ~or a period o~ 24 hours at 22C. After removal, the sponges and sheets are exhaustively washed in several changes of water over 24 hours, frozen and freeze dried at -65C. in a vacuum of less than 50 millitorrs.
EX~MPI.~ 11 Crosslinking of Collagen-Based Matri~
By Severe Dehydration The products of Examples 4 and 6 to 10 are placed in a vacuum oven at room temperature and exposed to a vacuum of less than 50 millitorr. After one hour the samples are heated to 110C. and remain at this temperature for 72 hours at which time the temperature is lowered to 40C. The samples are then removed from the vacuum oven and stored -29C.
~ ~, Crosslinking of Collagen-Based Matrix Using Succinimidyl Active Ester Two grams of succinimidyl active ester crosslinked collagen prepared according to Example 5 is placed in a Waring Blender containing 400 ml. of HCl pH 2.0 and dispersed for two minutes. This mixture is deaerated by placing in a vacuum of 300 millitorr and is then placed at room temperature in a 100% reLative humidity environment for 24 hours. The material is then cooled to 0C., frozen and freeze dried at -65C. using a vacuum of less than 50 millitorr or air dried to make sponges or sheets, respectively.
Prepara~ion of Collagen-Based Matrix Containing Protease Inhibitors Sponges and sheets prepared according to Examples 4 to 9 are placed in 20 ml. of HCl at pH 2.0 containing 25%
cysteine or 0.1% (W/V) a-2 macroglobulin. The mixture is frozen and freeze dried at -65C. at a vacuum of less than 50 millitorr or air dried at room temperature.
, ~ , ~'~9579~
In Vitro Enzymatic Degradation One cm. of each of the products of the above Examples is placed in 2.0 ml of 10 mM Tris-HCl pH 7.4 containing 25 mM calcium chloride and 100 unites of type IV collagenase from Clostridium histolyticum (Sigma Chemical Co.) is added per mg of sample. The samples are placed in a 37C. environment and the intactness of each sample is visually checked every 10 minutes. The time is recorded when each sample has visibly degraded into pieces smaller than about 0.5 ~m. The results are presented in Table I.
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EK~MPL~ 15 In Vitro Determination of Swelling Ratio The swelling ratio of denatured collagen is inversely related to the degree of crosslinking. The products of the above Examples were boiled for 2 minutes in distilled water and then blotted between two napkins.
A 1 kg. weight was placed on top of the napkins containing the materials for 20 seconds. The wet sample weight was recorded and the sample was then dried at 110Ç. for 3 hours. After drying the weight was again recorded and the swelling ratio (r) was calculated from the following relationship:
r = l/Vf DW/PC ; and where 15 where V
DW) + (WW - DW) ( Pc ) ( P~l20 ) DW and WW are the dry and wet weights, Pc and PH20 are the material and water densities, respectively. The results are presented in the aforementioned Table I.
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Mechanical Properties of Collagen~Based Matrices Sponges and sheets prepared in accordance with the above Examples were cut into rectangular (4.0 cm x 1.0 cm) strips and immersed in phosphate buffer solution pH
7.5 for 20 minutes prior to mechanical testing. The strips were tested in uniaxial tension at 22C. at a strain rate of 10%/minute using an Instron~ Model 1122 testing device. The ends of the strips were placed in pneumatic grips that were closed under a pressure of 40 psig with a gage length of 20 mm. Stress-strain curves were obtained from which the Young's moduli at high (HSM) and low strains were calculated. The strain at which the low modulus region anded was designated eL and the strain at failure was denoted efO The strain results are presented in Table I, above.
Subcutaneous Biocompatibility of Collagen-Based Matrix Sponges and sheets prepared in accordance with to the above Examples were tested for biocompatibility subcutaneously after sterilization by exposure 2.5 M
rads of gamma radiation. Implantation was carried out under sterile conditions using 350 gr white f~male guinea pigs as test animals.
A 1 cm cutaneous incision was made on one side of the back and the skin was separated from the fascial layer and a 1 cm. x 1 cm. piece of the implant was placed in this space. The edges of the skin were fastened together over th~ implant using wound clips.
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Animals were sacri~ied on the 6th, 9th and 12th post implantation day and the tissue containing the carrier was placed in Carson's fixative and processed for histological studies. The results are presented in the following Table II.
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~Z~7~36 Preparation of Diffusion Control Layer on a Matrix La~er Using sponges and sheets prepared in accordance with Examples 4 to 10, a 1 mm. layer of Silastic Medical Grade adhesive was applied to the surface of the matrix layer using a spatula. The diffusion control layer is cured by application of a vacuum of 100 millitorr for a pariod of 2 hours at 22C. The resultant complex of the diffusion control and matrix layers was placed in contact with full thickness dermal wounds.
Biocompatibility of Diffusion Control and Matrix Layers on Full Thickness Dermal Wounds Sponges and sheets prepared according to Example 18 were tested after radiation sterilization as dressings on open dermal wounds on female Hartley Albino 350 gr.
white guinea pigs. Each animal was separately fed and weighed for 4 days prior to testing. One day before testing, the animal was shaved using an electric clipper followed by depilatory treatment with Nair~ (a depilatory) and washed. The animal was then anesthetized by exposure to ether and its back washed with providone-iodine and alcohol solutionsO A 2 cm x 2 cm piece of material composed of matrix and diffusion control layers soaked in a phosphate buffer solution (0.182 M phosphate and 0.154 M NaCl), was placed on a full thickness dermal wound on the same area with the matrix layer against the panniculus carnosus.
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The matrix and the diffusion control layers were sutured to the wound bed at the edges of the dressing using chrome tanned gut sutures. The animal was bandaged by placing sterile cotton dressing sponge over the wound dressing and then wrapped with an Elasticon~
elastic tape (Johnson and Johnson Products, Inc.) secured around the neck. Animals were housed three to a cage during the experiment.
The animals were monitorled daily and their bandages examined for tears. Animals were sacrificed at 6, 9 and 12 day post implantation and the implant and wound beds were excised, fixed and processed for histological examination. The results are presented in Table III.
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BIODEGRAD~BLE MATRI~ AND
METHODS FOR PROD~CING SA~R
Field of the Invention This invention relates to a biodegradable matrix, and more particularly to a multifunctional collagen-based matrix and/or carrier system thereof.
Background of the Invention .
Delivery of drugs, growth factors, hormones, peptides and glycopeptides to external wounds has classically occurred by direct topical application and application to internal wounds by injection into the blood or by absorption into the blood through the digestive system. Controlled release of these agents has been achieved by encapsulation either in bulk or at a microscopic level using synthetic polymers, such as silicone, and natural polymers, such as gelatin and cellulose. The release rate can be controlled for periods of up to a year by proper choice of the polymeric system used to control the diffusion rate (Langer, R.S.
and Peppas, N.A., Biomaterials 2, 201,1981). Natural polymers, such as gelatin and cellulose slowly dissolve in a matter of minutes to hours while silicone remains intact for periods of months to years. Biodegradable polymers offer an advantage for controlled release to internal wounds since only a single surgical procedure is necessary.
.
7g6 Collagen is a biodegradable polymer found in animals and in man. It has been used as a plasma expander, vehicle for drug delivery, vitreous body replacement, hemostatic agent, suture material, corneal replacement, hemodialysis membrane, wound dressing and artificial skin, hernia patch, vessel prosthesis, vaginal contraceptive, and injectable agent for tissue augmentation (Chvapil et al., Int. Review of Connective Tissue Research 6, 1, 1973; Chvapil, in Biology of Collagen edited by A. Viidik and 3. Vuust, Academic Press, chapter 22, 1980). In most of these applications, the collagen is reconstituted and crosslinked into an insoluble form.
There is described in Yannas et al, (U.S. patent 4,060,081), the use of collagen and mucopolysaccarides as synthetic skin. Such material is crosslinked using glutaraldehyde, a bifunctional crosslinking agent, which reacts with free amines. One major drawback to using crosslinked collagen has been the adverse biological effects of free glutaraldehyde, a common agent used to crosslink and insolubilize collagen in many applications.
Leaching of glutaraldehyde from crosslinked collagens has been shown to be cytotoxic to cells, specifically fibroblasts (Speer et al., J. Biomedical Materials 25 Research 14,753,1980; Cooke et al., British J. Exp. Path. -64,172,1983). Recent evidence suggests that glutaralde-hyde polymers and not monomeric glutaraldehyde form crosslinks between collagen molecules; these crosslinks can then rearrange to release free glutaraldehyde and glutaraldehyde :1S ~`
polymers (Cheung, D.T. and Mimni, M.D., Connective Tissue Research 10, 187-217,1982).
Summary of the Invention The present invention provides in one embodiment a sponge or sheet of a collagen-based material including a collagen selected from the group consisting of types I, II and III collagens which sponge or sheet is contacted with a cross-linking agent selected from the group consisting of a carbodiimide or a succinimidyl active ester to form an intermediate collagen-based matrix which is subsequently subject:ed to conditions of severe dehydration to form a collagen-based matrix in sponge or sheet form. In another embodiment, the sponge or sheet of the collagen-based material is first sub~ected to conditions of severe dehydration followed by contacting tha thus formed intermediate collagen-based matrix with a carbodiimide cross-linking compound to form the collagen-based matrix in sponge or sheet form. In still another embodiment of the present invention, the cross-linking agent is admixed with the collagen-based material prior to formation of the intermediate collagen-based sponge or sheet followed by processing steps of severe dehydration. In a particularly preferred form of the invention, a carrier compound is ~5'~
incoxporated into the collagen based material during processing to form a collagen-based matrix in sponge or sheet form impregnated with a carrier compound wherein the carrier compound is selected from the group consisting of types IV and V collagen, fibronectin, laminin, hyaluronate, proteoglycan, epidermal growth factor, platelet derived growth factor, angiogenesis factor, antibiotic, antifungal agent, spermicidal agent, enzyme and enzyme inhibitor.
According to another aspect of the invention, a method of preparing a cross-lin:ked collagen matrix where the collagen in said matrix is selected from the group consisting of Types I, II and III collagen, said method comprising treating said selected collagen by carrying out one of the following steps (a) and (b) and following with the other:
a) contacting said selected collagen with a cross-linking agent selected from the group consisting of a carbodiimide, a bifunctional succinimidyl active ester and mixtures thereof; and b~ subjecting said selected collagen to elevated temperatures under a vacuum.
According to another aspect of the invention, a cross-linked collagen matrix which was cross-linked by chemical cross-linking a~d cross-linked by subjecting the collagen to elevated temperatures under a vacuum.
.~
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Detailed Description of the Invention The collagen-based carrier systems of the present invention are based on the use as a starting material of a soluble or insoluble collagen selected from the group consisting of types I, II and III collagens and mixtures thereof.
Soluble collagens of the types I, II and III
collagen are prepared by limited enzymatic digestion of tissue enriched in such collagen types and are formed into collagen-based solution (i.e., a soluble collagen dissolved in a suitable solvent, such as dilute hydrochloric acid, dilute acetic acid or the like).
Insoluble collagens are derived from the following typical sources: type I collagen; bovine, chicken and fish skin, bovine and chicken tendons and bovine and chicken bones including fetal tissues; type II collagen;
bovine articular cartilage, nasal septum, sternal cartilagej and type III collagen; bovine and human aorta and skin.
In one embodiment of the present invention, a collagen-based solution or an insoluble collagen dispersed and swollen in a suitable liquid medium (e.g.
dilute hydrochloric acid, dilute acetic 57~6 acid or the like) is subjected to a temperature of between about ooc. to -100Co to thereby solidify the collagen-based material. Thereafter, the solidified collagen-based material is subjected to a vacuum o~
less than about 50 millitorr at a temperature of from about 22C. to -100C. to form a collagen-based sponge to be further processed, as hereinafter more clearly described. Generally, a weight ratio of soluble or insoluble collagen to solvent or dispersion agent, respec~ively, of from 1 to 10,000 or ~rom 1 to 15 is used to form the collagen-b2ised solution or dispersion.
In another embodiment of the present invention such a collagen-based solution o~ a collagen-based dispersion is dried into sheet Porm prior to further processing as more fully hereinafter described. Dryiny is ef~ected at temperatures o~ from 4C. to 40C for a period of time of from ~ to 48 hours.
In one embodiment of the present invention to form a collagen-based matrix, a collagen-based sponge or sheet is first contacted with a crosslinking agent selected from the group consisting of a carbodiimide or N-hydroxysuccinimide deriv~d active esters (succinimidyl active ester) ~ollowed by severe dehydration to form the collagen-based matrix.
Examples o~ the carbodiimides include cyanamide and l-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride. Examples o~ bifunctional succinimidyl active esters including bifunctional ~-hydroxysuccinimide, 3,31-dithio (sulfosuccinimidyl) propionate and bis ~sulfosuccinimidyl) suberate. When using a carbodiimide crosslinking agent, the collagen-based sponge or sheet ., "
9~
is immersed in a carbodiimide solution at a concentration of from about 0.1 to 10% (W/V) maintained at a temperature of from about 2 to 40C. and at a pH of between 2 to 11 for a period of time of from about 2 to 96 hours. When using a succinimidyl active ester crosslinking agent, the collagen-based sponge or sheet is immersed in a solution thereof at a concentration of from about 0.1 to about 15.0~ ~W/V) maintained at a temperature of ~rom about 2 1:o 40C. for a period of time of from about 2 to g6 hours. The collagen-based sponge or sheet is placed in a solution containing 0.1 to about 15% (W/V) o~ N-hydroxysuccinimide and carbodiimide at a pH between 2 to 11 for a period of time between 2 to 96 hours at a temperature of from about 2~C. to 40C. The thus treated intermediate collagen-based matrix is exhaustively washed to remove excess crosslinking agent.
Severe dehydr~tion of the in~ermediate collagen-based matrix inv~lve# conditions of temperature of from 50C. to 200C. at a vacuum of 50 millitorr or less for a period of time of from 2 to 96 hour~ to thereby form the collagen-based matrix. Prior to severe dehydration, the intermediate collagen-based matrix in sponge form is preferably solidified at a temperature of between about 0C. to -100C. and thereafter subjected to a vacuum of at least 50 millitorr at a temperatura of between about 22C. and -lOO~C.
In another embodiment of the present invention to form the collagen based matrix when using a c~rbodiimide crosslinking agent, severe dehydration may be effected to form an intermediate collagen-based matrix prior to contacting such an intermediate collagen-based matrix with such a crosslinking agent.
~ ~"
In another embodiment of the present invention to form the collagen-based matrix, the cross-linking agent is premixed with the collagen-based material prior to drying or initiating of freeze drying processing steps.
The collagen-based matrix prepared in accordance with the present invention may be described as a "coral-like" or "scaffold" structure having interstices of a pore size of from 3 to 100 ~m., and of a molecular weight of from 10 X 106 to in excess of 50 X 106 with a molecular weight between crosslin~s from 1,000 to 100,000 via the formation of covalent bonds.
Another embodiment of the present invention is the incorporation of a carrier compound into the collagen-based matrix. Such a carrier compound is selected from the group consisting of collagen types IV and V, fibronectin, laminin, hyaluronate, proteoglycans, epidermal growth factor, platelet derived growth factor, angiogenesis factor, antibiotic, antifungal agent, spermacidal agent, hormone, enzyme and enzyme inhibitor.
Generally, the carrier compound may be introduced at any time during processing of the collagen-based material to the collagen-based matrix in sponge or sheet form.
Preferably, a carrier compound is incorporated prior to solidifying of the soluble or insoluble collagen in forming the intermediate collagen-based matrix, or prior to solidifying of the intermediate collagen-based matrix prior to severe dehydration. The carrier materials are added in an amount of from 1 to 30% (w/w) based on the weight of soluble or insoluble collagen. Generally, connective .
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tissue factors, such as fibronectin, types IV and V
collagens, lamini~, glycosaminoglycans and hyaluronate are incorporated during initial processing steps in forming the collagen-based sponge or after crosslinking of the intermediate collagen-based matrix. It is preferable to incorporate fibronectin and hyaluronate during forming of the intermediate collagen-based matrix.
There are many sources for the diverse carrier compounds for incorporation into the collagen-based matrix constituting one embodiment of the present invention. Type IV and V collagens are found associated with basement membranes and smooth muscle cells in tissues, respectively. Typical sources of Type IV
include the EHS mouse sarcoma tumor, bovine and human placenta, lens capsule and kidney; sources of Type V
collagen include placental membranes, ocular tissues and fetal skin (see for example, Trelstad, In Immunochemistry of the Extracellular Matrix, Vol. 1 edited by H. Furthmayr, CRC Press, chapter-2, 1982).
Typical sources of proteoglycans include bovine and human cartilage and synovial fluid, nasal s~ptum and sternal cartilage, and skin. Typical sources for glycoproteins include EHS tumor, bo~ine and human kidneys, cartilage, bone and placenta as well as bovine and human blood. Typical sources of hyaluronate include rooster comb and bovine vitreous.
Preferred carrier compounds for the collagen-based matrix include fibronectin, laminin, type IV collagen and complexes of hyaluronate and proteoglycans. A value of the swelling ratio of between 2.5 to 5 is required for a collagen-based matrix which . ~
.~
~Z~ 36 comes into contact with open wounds, while a swelling ratio of between 2.5 to 10 are useful for a collagen-based matrix including carrier compounds for subcutaneous implantation. The swelling ratio is de.fined as the volume of water absorbed per unit volume of collagen-based matrix.
In the case of internal ~ounds and short-term drug release, collagen-based matrix including a carrier compound in the form of a she~et or a tube is placed in direct contact with tissue.
The biodegradation rate and the release rate can be controlled by variation of thle crosslink density. For applications where long term release is desired, a nonporous diffusion layer of a biodegradable polymer, such as poly-3-(hydroxybutyrate) is applied to each side of the collagen-based matrix. For materials to be used on full thickness wounds, a diffusion control layer, such as described in the aforementioned U.S. Letters Patent to Yannas, is applied to prevent diffusion of water or other small volatile molecules from the collagen-based matrix; the diffusion control layer must adhere tightly to the collagen-based matrix layer. The combination of collagen-based matrix layer and diffusion control layer must be strong enough to be sutured and have a tensile strength of at least 100 psi and be able to deform at least 10% before failing. Synthetic non-biodegradable polymers, such as silicone polymers (Silastic Medical Grade Adhesive~) or biodegradable polymers, such as polylactic acid, polyglycolic acid, poly-3-(hydroxybutyrate) and copolymers of these materials can be used as the diffusion control layer.
.
.. . ..
7~6 Silicone polymers are preferred materials to control the rata of diffusion of small molecules.
Curing of the adhesive in the diffusion control layer can occur without wetting the carrier compound in tne collagen-based matrix by desiccation at room temperature. A film 0.5 to 1.5 mm in thickness is applied to the matrix layer and is allowed to cure at room temperature for at least 2 hours using a vacuum of 14 in. of Hg.
The thickness of the collagen-based matrix can be varied from 1 to several hundred mm. For full thickness wounds, a thickness of 2 to 3 mm is dasired and enablas close contact between the carrier compound in the collagen-based matrix and the wound bed.
When implanted subcutaneously or directly on full thickness dermal wounds, any collagen-based matrix of the present invention does not stimulate the inflammatory process. In addition, chronic implantation results in fibroblast and endothelial cell migration into the collagen-based matrix. The degradation and resorption rate of collagen-based matrices are as assayed in vitro by determination of the time that 1 mg of the material resists solubilization by lOO units o~
bacterial collagenase. One unit of collagenase liberates amino acids in collagen e~uivalent to 1.0 micro mole of L-leucine in 5 hours at 37C. A
combination of succinimidyl active ester formation and severe dehydration or carbodiimide treatment and severe dehydration increases the collagenase resistance time significantly over that observed by any of the procedures heretofore used. These studies indicate that the crosslinking methods of the present invention result in resistance to collagenase dagradation and show no stimulation of inflammation.
:L2~S7~f~
EXAMPLES OF THE INVENT:CON
The following examples are illustrative of conditions for the process of the present invention and it is to be understood that the scope of the invention is not to be limited thereby.
Preparation of Soluble and Insoluble Collagens The collagen used is prepared from calf hides after the grain layer is separated from the corium or dermis.
The corium is cut into pieces, washed, swollen, freeze dried and stored at -20C.
Soluble collagen is obtained by placing 250 gr of the freeze dried insoluble collagen in 1.5 liters of HCl at a pH of 2.5 containing 1.5 gr of crystalline pepsin (Sigma Chemical Company). The mixture is stirred overnight at 4~C. and then filtered through cheese cloth, Whatman~ filter paper #4 followed by Whatman #42, Gelman 5 ~m and 1.2 ~m filters and finally through Millipore~ 0.65 ~m and 0.45 ~m filters. ~he soluble fraction obtained after sequential filtration contains types I, III and V collagens. The soluble collagen fraction is dialyzed against a 1.0 M NaCl solution containing 50 mM Tris [tris(hydroxymethyl)aminomethane buffering agent] adjusted to pH 7.5 and enough solid NaCl is àdded to raise the molarity of the solution to 1.7. The precipitate at 1.7 M NaCl is type III
collagen and is collected by centrifugation at 10,00 x g for 60 minutes and then dialyzed versus 0.005 M
acetic acid, freeze dried and stored at -20~C. To the supernatant is added additional NaCl to raise the molarity to ~29~i7~36 2.5 M and the precipitate (type I collagen) is pelleted by centrifugation, dialyzed versus 0.005 M acetic acid, freeze dried and stored at -20C. The remaining supernatant contains type V collagen and is dialyzed against 0.005 M acetic acid, freeze dried and stored at -20C.
Insoluble collagen solutions are obtained by dispersing freeze dried corium ground using a Wiley Mill in HCl at pH of 2.5. The swollen collagen is then dialyzed against 0.005 M acetic acid and freeze dried.
If mature bovine hide is the source of the corium, the insoluble collagen produced is typically type I.
Soluble type IV collagen is extracted from the mouse EHS sarcoma tumor after washing the tumor in cold distilled water 3 times by spin filtration at 10,000 x g for 30 minutes. The pellet (0.500 gr) is homogenized in 0.5 liters of 0.5 M acetic acid adjusted to pH 2.5 with HCl and 0.5 gr of pepsin is added. The homogenate is allowed to mix at 4C. for 24 to 48 hours, filtered through cheese cloth, spun at 10,000 x g for 30 minutes.
The pellet is re-suspended in 0.5 M NaCl containing 50 mM
Tris, NaCl is added until a final concentration of 4.5 M
is obtained, centrifuged at 10,000 x g for 30 minutes and the pellet is dialyzed against 0.1 N acetic acid 3 times and freeze dried.
EX~MPL~ 2 Preparation of Bovine Serum Fibronectin Freshly drawn bovine blood (80 ml) is collected in a polypropylene tube containing 20 ml. of 5% trisodium citrate and ~35796 O.1 mM phenylmethysulfonyl fluoride. The blood is centrifuged at 300 x g for 10 minutes and the plasma is then separated from the cell layer and further centrifuged at 30,000 x g at a temperature of 15C. for 30 minutes. To the plasma is then added an additional 1 mM of phenylmethylsulfonyl fluoride and then it is poured through a gelatin-sepharose col~mn. The column is washed with a phosphate buffer solution (0.182 M phosphate and 0.145 M NaCl), 2 column volumes of lM NaCl in a phosphate buffer, 2 column volumes of phosphate buffer solution, 2 column volumes of 4 M urea in a phosphate buffer. The optical density of column fractions is monitored at a wavelength of 280 nm with the bulk of the fibronectin normally present in the fractions containing 4 M urea.
Fibronectin containing fractions having optical densities greater than 0.1 are dialyzed against 0.180 M phosphate buffer containing 0.145 M Nacl (pH 7.2). The sample is then dialyzed against 0.05 M Tris-HCl containing 4.5 M
urea ~pH 7.2) and applied to a DEA (diethylaminoethyl cellulose) ion exchange column at room temperature. The column is eluted with a 0 to 0.3 M NaCl linear gradient in a 0.05 M Tris-HCl buffer solution (pH 7.2) containing 4.5 M urea. The eluted fibronectin is dialyzed against 0.180 M phosphate containing 0.145 M NaCl and 1.0 M urea and frozen at -20C.
~L295~
Preparation of Laminin Laminin is prepared ~or lathrytic EHS tumors grown C57/6J mice. The tumors are dissected and homoganized in 3.4 M NaCl containing 50 mM Tris-HCl adjusted to pH
7.4 and protease inhibitors. The homogenate is centrifuged at 16,000 x g for 60 minutes and the pellet is collected and resuspended in 3.4 M NaCl. Following centrifugation at 16,000 x g for 60 minute~ a second time, the homogenate is resuspended in 0.5 M NaCl containing 50 mM Tris-HCl pH 7.4 and protease inhibitors stirred for 18-24 hours at 4C. followed by centrifugation at 16,000 x g ~or 60 min. The supernatant is brought to 3.5 M by addition of solid NaCl, stirred overnight at 4C. and the precipitate is collected by centrifugation. Laminin is ~urther purified by redissolving in 0.5 M NaCl containing 50 mM
Tris-HCl pH 7.4 followed by centrifugation at 10,000 x g for 60 minutes the supernatant is dialyzed against 2 M
urea containing 2.5 NaCl and 50 mM Tris-~Cl pH 8.6 and chromatographed over a 2.5 x 2.5 cm column containing DEAE cellulose eguilibrated with the same bu~fer at 4C.
The unbound fraction is dialyzed against 2 M urea containing 50 mM Tri~-HCl pH 8.6 and rechromatographed on the DEAE~ column eguilibrated with the same buffer.
The unbound fraction is concentrated by vacuum dialysis and chromatographed on Sephacryl S-300~e~uilibrated with _ _ __ ~2~57~6 1.0 M CaCl2, 50 mM Tris-HCl pH 7.5 at 22C. the void volume is collected and dialyzed against 0.4 M NaCl, 50 mM Tris-Hcl pH 7.4 and stored at 4C. Laminin is resolubilized in 0.1 M ammonium hydroxide pH 11.0 and then the pH is adjusted to 7.2.
Preparation of Collagen-based Sponges and Sheets Soluble or insoluble collagen (1.2 gr.) is added to 120 ml. of a dilute HCl solution of pH 3.0 and the mixture is ground in a Wariny Blender at low speed for 1 minute and thereafter at high speed for 1 minute. The solution or dispersion is then poured into a vacuum flask and deaerated at a vacuum of 100 millitorr for 10 minutes. Collagen dispersions and solutions to be converted into sponges are cooled to 0C. and frozen at -100C. before freeze drying at -65C. under a vacuum of less than 10 millitorr. Collagen dispersion or solutions to be processed into sheets were placed in a sterile hood and allowed to air dry for 2~ to 48 hours at 22C.
EX~MPL~ 5 Preparation of Succinylated, Succinimidyl Ester Crosslinked Intermediate Collagen-Based Matrix Nine grams of succinic anhydride are dissolved in 80 ml. of distilled water and mixed for 30 minutes at 37C.
After the succinic anhydride is in solution, the pH is adjusted to 7.2 and the volume brought to 100 ml. This solution is placed in a Waring t7~6 Blender and 1.0 gr of collagen is added, ground ~or 2 minutes allowed to stand at 22C. for 1 hour, placed on Whatman #4 filter paper to remove unreacted succinic anhydride and then washed with 100 ml o~ distilled water.
The residue is placed in a solution o~ 20 ml of phosphate buffer (0.182 M phosphate and 00145 M NaCl) and 2 gr of N-hydroxysuccinimide and 2 gr of cyanamide are added. The solution pH :is then adjusted to 7.2.
The residue is allowed to react for 3 hours at room temperature and then washed with distilled water in a Buchner funnel under a vacuunn of 14 in. of Hg. Sheets and sponges of succinylated, succinimidyl ester crosslinked intermediata collagen-based matrices are produced in acrordance with the processes described in Example 4.
Preparation of Collagen-3asèd Matrix Containing Fibronectin 20To 1.2 gr solubls or insoluble collagen in 120 ml of HCl pH 3.0 is added to 0.12 gr of fibronectin in (2.5 mg. fibronectin/ml) 0.1 M urea containing O.la2 M
phosphate and 0.145 ~ NaCl and the mixture is dispersed ~ _n a ',~aring Blender~ for 2 minutes. Sheets and sponges are prepared in accordance with the processes described in Example 4.
~;~9~;~96 Sponges and Sheets Formed by Coating Type I Collagen With Laminin, Fibronectin, and Type IV Collagen Collagen sheets and sponges formed according to Examples 4 and 6 are swollen in a 0.1 ammonium acetate pH
7.2 containing 1 to 5~ laminin, fibronectin or type IV
collagen. The swollen sponge or sheet is then frozen and freeze dried at -56C. and in a vacuum less than 50 millitorr.
Preparation of Collagen-Based Matrix Containing Hyaluronate and Proteogycans To 1.2 gr. of soluble and insoluble collagen in HCl pH 3.0 as added to 0.12gr. of a complex of hyaluronate and proteoglycans (Sigma Chemical Company Grade III-P~ in a HCl pH 2.0 to a final volume of 120 ml. The mixture is dispersed in a Waring Blender and eith~r freeze dried or air dried in accordance with the processes of Example 4.
EXAMPL~ 9 Preparation of Collagen-Based Matrix Containing Type IV Collagen To 1.2 gr. of soluble or insoluble collagen type I
in HCl pH 2.0 is added to 0.012 gr. of type IV collagen in a 0.1 M ammonium acetate pH 7.2 to a final volume of 120 ml. The mixture is ~95796 dispersed in a Waring Blender for 2 minutes and formed into sheets or sponges in accordance with the processes of Example 4.
Cyanamide Crosslinking of Collagen-Based Matrix The product of Examples 4 and 6 to 9 are crosslinked by immersion in an aqueous solut:ion containing 1% by weight of cyanamide at pH 5.5 ~or a period o~ 24 hours at 22C. After removal, the sponges and sheets are exhaustively washed in several changes of water over 24 hours, frozen and freeze dried at -65C. in a vacuum of less than 50 millitorrs.
EX~MPI.~ 11 Crosslinking of Collagen-Based Matri~
By Severe Dehydration The products of Examples 4 and 6 to 10 are placed in a vacuum oven at room temperature and exposed to a vacuum of less than 50 millitorr. After one hour the samples are heated to 110C. and remain at this temperature for 72 hours at which time the temperature is lowered to 40C. The samples are then removed from the vacuum oven and stored -29C.
~ ~, Crosslinking of Collagen-Based Matrix Using Succinimidyl Active Ester Two grams of succinimidyl active ester crosslinked collagen prepared according to Example 5 is placed in a Waring Blender containing 400 ml. of HCl pH 2.0 and dispersed for two minutes. This mixture is deaerated by placing in a vacuum of 300 millitorr and is then placed at room temperature in a 100% reLative humidity environment for 24 hours. The material is then cooled to 0C., frozen and freeze dried at -65C. using a vacuum of less than 50 millitorr or air dried to make sponges or sheets, respectively.
Prepara~ion of Collagen-Based Matrix Containing Protease Inhibitors Sponges and sheets prepared according to Examples 4 to 9 are placed in 20 ml. of HCl at pH 2.0 containing 25%
cysteine or 0.1% (W/V) a-2 macroglobulin. The mixture is frozen and freeze dried at -65C. at a vacuum of less than 50 millitorr or air dried at room temperature.
, ~ , ~'~9579~
In Vitro Enzymatic Degradation One cm. of each of the products of the above Examples is placed in 2.0 ml of 10 mM Tris-HCl pH 7.4 containing 25 mM calcium chloride and 100 unites of type IV collagenase from Clostridium histolyticum (Sigma Chemical Co.) is added per mg of sample. The samples are placed in a 37C. environment and the intactness of each sample is visually checked every 10 minutes. The time is recorded when each sample has visibly degraded into pieces smaller than about 0.5 ~m. The results are presented in Table I.
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EK~MPL~ 15 In Vitro Determination of Swelling Ratio The swelling ratio of denatured collagen is inversely related to the degree of crosslinking. The products of the above Examples were boiled for 2 minutes in distilled water and then blotted between two napkins.
A 1 kg. weight was placed on top of the napkins containing the materials for 20 seconds. The wet sample weight was recorded and the sample was then dried at 110Ç. for 3 hours. After drying the weight was again recorded and the swelling ratio (r) was calculated from the following relationship:
r = l/Vf DW/PC ; and where 15 where V
DW) + (WW - DW) ( Pc ) ( P~l20 ) DW and WW are the dry and wet weights, Pc and PH20 are the material and water densities, respectively. The results are presented in the aforementioned Table I.
, ,~ , i7~
Mechanical Properties of Collagen~Based Matrices Sponges and sheets prepared in accordance with the above Examples were cut into rectangular (4.0 cm x 1.0 cm) strips and immersed in phosphate buffer solution pH
7.5 for 20 minutes prior to mechanical testing. The strips were tested in uniaxial tension at 22C. at a strain rate of 10%/minute using an Instron~ Model 1122 testing device. The ends of the strips were placed in pneumatic grips that were closed under a pressure of 40 psig with a gage length of 20 mm. Stress-strain curves were obtained from which the Young's moduli at high (HSM) and low strains were calculated. The strain at which the low modulus region anded was designated eL and the strain at failure was denoted efO The strain results are presented in Table I, above.
Subcutaneous Biocompatibility of Collagen-Based Matrix Sponges and sheets prepared in accordance with to the above Examples were tested for biocompatibility subcutaneously after sterilization by exposure 2.5 M
rads of gamma radiation. Implantation was carried out under sterile conditions using 350 gr white f~male guinea pigs as test animals.
A 1 cm cutaneous incision was made on one side of the back and the skin was separated from the fascial layer and a 1 cm. x 1 cm. piece of the implant was placed in this space. The edges of the skin were fastened together over th~ implant using wound clips.
.
Animals were sacri~ied on the 6th, 9th and 12th post implantation day and the tissue containing the carrier was placed in Carson's fixative and processed for histological studies. The results are presented in the following Table II.
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~Z~7~36 Preparation of Diffusion Control Layer on a Matrix La~er Using sponges and sheets prepared in accordance with Examples 4 to 10, a 1 mm. layer of Silastic Medical Grade adhesive was applied to the surface of the matrix layer using a spatula. The diffusion control layer is cured by application of a vacuum of 100 millitorr for a pariod of 2 hours at 22C. The resultant complex of the diffusion control and matrix layers was placed in contact with full thickness dermal wounds.
Biocompatibility of Diffusion Control and Matrix Layers on Full Thickness Dermal Wounds Sponges and sheets prepared according to Example 18 were tested after radiation sterilization as dressings on open dermal wounds on female Hartley Albino 350 gr.
white guinea pigs. Each animal was separately fed and weighed for 4 days prior to testing. One day before testing, the animal was shaved using an electric clipper followed by depilatory treatment with Nair~ (a depilatory) and washed. The animal was then anesthetized by exposure to ether and its back washed with providone-iodine and alcohol solutionsO A 2 cm x 2 cm piece of material composed of matrix and diffusion control layers soaked in a phosphate buffer solution (0.182 M phosphate and 0.154 M NaCl), was placed on a full thickness dermal wound on the same area with the matrix layer against the panniculus carnosus.
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The matrix and the diffusion control layers were sutured to the wound bed at the edges of the dressing using chrome tanned gut sutures. The animal was bandaged by placing sterile cotton dressing sponge over the wound dressing and then wrapped with an Elasticon~
elastic tape (Johnson and Johnson Products, Inc.) secured around the neck. Animals were housed three to a cage during the experiment.
The animals were monitorled daily and their bandages examined for tears. Animals were sacrificed at 6, 9 and 12 day post implantation and the implant and wound beds were excised, fixed and processed for histological examination. The results are presented in Table III.
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1.~9579~i Numerous modifications and variations of the present invention are possible in ight of the above teachings and, therefore, within the scope of the appended claims, the invention may be practised otherwise than as particularly described.
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1.~9579~i Numerous modifications and variations of the present invention are possible in ight of the above teachings and, therefore, within the scope of the appended claims, the invention may be practised otherwise than as particularly described.
Claims (70)
1. A method of preparing a cross-linked collagen matrix where the collagen in said matrix is selected from the group consisting of Types I, II and III collagen, said method comprising treating said selected collagen by carrying out one of the following steps (a) and (b) and following with the other:
a) contacting said selected collagen in a liquid medium with a cross-linking agent selected from the group consisting of a carbodiimide, a bifunctional succinimidyl active ester and mixtures thereof; and b) subjecting said selected collagen to elevated temperatures under a vacuum.
a) contacting said selected collagen in a liquid medium with a cross-linking agent selected from the group consisting of a carbodiimide, a bifunctional succinimidyl active ester and mixtures thereof; and b) subjecting said selected collagen to elevated temperatures under a vacuum.
2. A method as defined in claim 1 further comprising introducing Type IV collagen or Type V collagen as a carrier compound into said matrix.
3. The method as defined in claim 1 wherein said collagen is prepared by admixing said selected collagen with a liquid medium, said liquid medium being a solvent for said collagen or a dispersing agent for said collagen.
4. The method as defined in claim 1 wherein said cross-linking agent is said carbodiimide and is in solution at a concentration of from about 0.1 to 10% (W/V).
5. The method as defined in claim 4 wherein said carbodiimide solution and collagen are maintained at a temperature of from 2 to 40°C for a period of 2 to 96 hours prior to further processing.
6. The method as defined in claim 5 wherein said carbodiimide solution is at a pH of from 2 to 11.
7. The method as defined in claim 1, 3 or 4 wherein step a) is performed prior to step b).
8. The method as defined in claim 5 or 6 wherein step a) is performed prior to step b).
9. The method as defined in claim 1, 3 or 4 wherein step b) is performed prior to step a).
10. The method as defined in claim 5 or 6 wherein step b) is performed prior to step a).
11. The method as defined in claim 1 wherein said cross-linking agent is said bifunctional succinimidyl active ester and is in solution at a concentration of from about 0.1 to about 15.0% (W/V).
12. The method as defined in claim 11 wherein said bifunctional succinimidyl active ester solution and said collagen-based substrate are maintained at a temperature of from 2 to 40°C for a period of 2 to 96 hours prior to further processing.
13. The method as defined in claim 11 or 12 wherein step a) is performed prior to step b).
14. The method as defined in claim 11 or 12 wherein step b) is performed prior to step a).
15. The method as defined in claim 1 wherein excess cross-linking agent is removed prior to step b) in the instance where step a) is performed prior to step b).
16. The method as defined in claim 1 wherein step b) is effected at a temperature of from 50°C to about 200° C at a vacuum of less than 50 millitorr.
17. The method as defined in claim 16 wherein step b) is effected for a period of time of from 2 to 96 hours.
18. The method as defined in claim 15, 16 or 17 wherein step a) is performed prior to step b).
19. The method as defined in claim 15, 16 or 17 wherein step b) is performed prior to step a).
20. The method as defined in claim 3 wherein said collagen admixed with said liquid medium is subjected to freeze drying after step a) or step b) whichever of said steps is first in a method of forming a collagen in sponge form.
21. The method as defined in claim 20 wherein said collagen admixed with said liquid medium is solidified prior to said step of freeze drying.
22. The method as defined in claim 21 wherein the step of freeze drying is effected under a vacuum of less than about 50 millitorr and at a temperature of from about 22°C to -100°C.
23. The method as defined in claim 22 wherein said collagen-based substrate is solidified at a temperature of from 0°C to -100°C.
24. The method as defined in claim 20 wherein said collagen is subjected to freeze drying prior to step b).
25. The method as defined in claim 24 wherein said collagen is solidified prior to freeze drying prior to step b).
26. The method as defined in claim 24 wherein the step of freeze drying is effected under a vacuum of less than about 50 millitorr and at a temperature of from about 22°C to -100°C.
27. The method as defined in claim 24 wherein said collagen is solidified at a temperature of from 0°C to -100°C.
28. The method as defined in claim 20, 24 or 25 wherein step a) is performed prior to step b).
29. The method as defined in claim 20, 24 or 25 wherein step b) is performed prior to step a).
30. The method as defined in claim 1 wherein said collagen is dried prior to either of step a) and step b) and further comprising forming said cross-linked collagen into a sheet form.
31. The method as defined in claim 30 wherein drying is effected at a temperature of from 4°C to 40°C for a time from 2 to 96 hours.
32. The method as defined in claim 30 or 31 wherein step a) is performed prior to step b).
33. The method as defined in claim 30 or 31 wherein step b) is performed prior to step a).
34. The method as defined in claim 3 wherein a carrier compound is introduced into said collagen in the formation of said collagen matrix, said carrier compound being selected from the group consisting of type IV
collagen, type V collagen, fibronectin, laminin, hyaluronate, proteoglycan, epidermal growth factor, platelet derived growth factor, angiogenesis factor, antibiotic, antifungal agent, spermicidal agent, enzyme and enzyme inhibitors.
collagen, type V collagen, fibronectin, laminin, hyaluronate, proteoglycan, epidermal growth factor, platelet derived growth factor, angiogenesis factor, antibiotic, antifungal agent, spermicidal agent, enzyme and enzyme inhibitors.
35. The method as defined in claim 34 wherein said collagen admixed with said liquid medium is subjected to freeze drying after step a) or step b) whichever of said steps is first in a method of forming a collagen in sponge form.
36. The method as defined in claim 35 wherein said collagen admixed with said liquid medium is solidified prior to the step of freeze drying.
37. The method as defined in claim 36 wherein the step of freeze drying is effected under a vacuum of less than about 50 millitorr and at a temperature of from about 22°C to -100°C.
38. The method as defined in claim 37 wherein said collagen admixed with said liquid medium is solidified at a temperature of from 0°C to -100°C.
39. The method as defined in claim 35 wherein said collagen matrix is subjected to freeze drying prior to either of step a) or step b).
40. The method as defined in claim 39 wherein said collagen matrix is solidified prior to freeze drying prior to either of step a) or step b).
41. The method as defined in claim 39 wherein the step of freeze drying is effected under a vacuum of less than about 50 millitorr and at a temperature of from about 22°C to -100°C.
42. The method as defined in claim 39 wherein said collagen admixed with said liquid medium is solidified at a temperature of from 0°C to -100°C.
43. The method as defined in claim 34 wherein said collagen admixed with said liquid medium is dried after step a) or step b) whichever of said steps is first and further comprising after the remaining step a) or step b) forming said cross-linked collagen matrix into a sheet form.
44. The method as defined in claim 43 wherein drying is effected at a temperature of from 4°C to 40°C for a time of from 2 to 96 hours.
45. The method as defined in claim 44 and further including the step of overlaying said collagen matrix in sheet form with a diffusion layer.
46. The method as defined in claim 45 wherein said diffusion layer is non-porous.
47. The method as defined in claim 46 wherein said diffusion layer which is non-porous is biodegradable.
48. The method as defined in claim 45 wherein said diffusion layer is formed on a non-biodegradable polymer.
49. The method as defined in claim 34, 39 or 43 wherein step a) is performed prior to step b).
50. The method as defined in claim 34, 39 or 43 wherein step b) is performed prior to step a).
51. A cross-linked collagen matrix which was cross-linked by chemical cross-linking and cross-linked by subjecting the collagen to elevated temperatures under a vacuum, said collagen being selected from the group consisting of Types I, II and III collagen.
52. A collagen matrix as defined in claim 51 wherein said chemical cross-linking was performed using a chemical agent selected from the group comprising carbodiimide and N-hydroxysuccinimide derived esters and mixtures thereof.
53. A collagen matrix as defined in claim 51 wherein said chemical cross-linking was performed using a carbodiimide.
54. A collagen matrix as defined in claim 51 wherein said chemical cross-linking was performed using a N-hydroxysuccinimide derived ester.
55. The collagen matrix as defined in claim 52 wherein said collagen is selected from the group consisting of type I, II and III collagen of a molecular weight of at least 1.0 x 106.
56. The collagen matrix as defined in claim 55 wherein said molecular weight is in excess of 50 x 106.
57. The collagen matrix as defined in claim 56 basing a molecular weight between cross-links of from 1,000 to 100,000 via covalent bonding.
58. The collagen matrix as defined in claim 55 having interstices of a pore size of from 3 to 100 µm.
59. The collagen matrix as defined in claim 55 and further including a carrier compound selected from a group consisting of type IV collagen, type V collagen, fibronectin, laminin, hyaluronate, proteoglycan, epidermal growth factor, platelet derived growth factor, angiogenesis factor, antibiotic, antifungal agent, spermicidal agent, enzyme and enzyme inhibitors.
60. The collagen matrix as defined in claim 55 in sheet form.
61. The collagen matrix as defined in claim 60 and further including a diffusion layer.
62. The collagen matrix as defined in claim 51 and further including a non-porous diffusion layer applied to either side of said collagen matrix.
63. The collagen matrix as defined in claim 62 wherein said non-porous diffusion layer is biodegradable.
64. The collagen matrix as defined in claim 61 wherein said diffusion layer is adhered tightly to said collagen matrix.
65. The collagen matrix as defined in claim 64 wherein said collagen-based matrix and said diffusion layer have a combined tensile strength of at least 100 psi.
66. The collagen matrix as defined in claim 64 wherein said collagen matrix and said diffusion layer have a deformation of at least 10%.
67. The collagen matrix as defined in claim 60 having a swelling ratio of at least about 2.5.
68. The collagen matrix as defined in claim 60, 61 or 62 further including a carrier compound selected from a group consisting of type IV collagen, type V collagen, fibronectin, laminin, hyaluronate, proteoglycan, epidermal growth factor, platelet derived growth factor, angiogenesis factor, antibiotic, antifungal agent, spermicidal agent, enzyme and enzyme inhibitors.
69. The collagen matrix as defined in claim 63, 64 or 65 further including a carrier compound selected from a group consisting of type IV collagen, type V collagen, fibronectin, laminin, hyaluronate, proteoglycan, epidermal growth factor, platelet derived growth factor, angiogenesis factor, antibiotic, antifungal agent, spermicidal agent, enzyme and enzyme inhibitors.
70. The collagen matrix as defined in claim 66 or 67 further including a carrier compound selected from a group consisting of type IV collagen, type V collagen, fibronectin, laminin, hyaluronate, proteoglycan, epidermal growth factor, platelet derived growth factor, angiogenesis factor, antibiotic, antifungal agent, spermicidal agent, enzyme and enzyme inhibitors.
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-
1985
- 1985-03-25 CA CA000477358A patent/CA1295796C/en not_active Expired - Fee Related
- 1985-03-25 IL IL74715A patent/IL74715A0/en unknown
- 1985-03-25 MX MX204720A patent/MX163953B/en unknown
- 1985-03-26 IT IT47869/85A patent/IT1182725B/en active
- 1985-03-27 JP JP60501598A patent/JPH0811121B2/en not_active Expired - Lifetime
- 1985-03-27 DE DE8585901827T patent/DE3585069D1/en not_active Expired - Fee Related
- 1985-03-27 AR AR29989585A patent/AR240608A1/en active
- 1985-03-27 ES ES541629A patent/ES8605988A1/en not_active Expired
- 1985-03-27 WO PCT/US1985/000504 patent/WO1985004413A1/en active IP Right Grant
- 1985-03-27 AU AU42105/85A patent/AU4210585A/en not_active Abandoned
- 1985-03-27 EP EP85901827A patent/EP0177573B1/en not_active Expired - Lifetime
- 1985-03-27 BR BR8506206A patent/BR8506206A/en unknown
- 1985-04-01 CN CN198585101396A patent/CN85101396A/en active Pending
- 1985-11-26 NO NO854723A patent/NO854723L/en unknown
- 1985-11-27 DK DK547485A patent/DK547485A/en not_active Application Discontinuation
- 1985-11-27 FI FI854692A patent/FI854692A0/en not_active Application Discontinuation
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1986
- 1986-03-26 US US06/843,828 patent/US4703108A/en not_active Expired - Lifetime
- 1986-06-18 US US06/875,827 patent/US4970298A/en not_active Expired - Lifetime
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FI854692A (en) | 1985-11-27 |
IT1182725B (en) | 1987-10-05 |
DE3585069D1 (en) | 1992-02-13 |
US4970298A (en) | 1990-11-13 |
ES541629A0 (en) | 1986-04-01 |
ES8605988A1 (en) | 1986-04-01 |
NO854723L (en) | 1985-11-26 |
MX163953B (en) | 1992-07-03 |
WO1985004413A1 (en) | 1985-10-10 |
FI854692A0 (en) | 1985-11-27 |
IT8547869A1 (en) | 1986-09-26 |
IL74715A0 (en) | 1985-06-30 |
AU4210585A (en) | 1985-11-01 |
JPS61502129A (en) | 1986-09-25 |
EP0177573A1 (en) | 1986-04-16 |
US4703108A (en) | 1987-10-27 |
CN85101396A (en) | 1987-01-31 |
DK547485D0 (en) | 1985-11-27 |
IT8547869A0 (en) | 1985-03-26 |
BR8506206A (en) | 1986-04-15 |
EP0177573B1 (en) | 1992-01-02 |
DK547485A (en) | 1986-01-24 |
JPH0811121B2 (en) | 1996-02-07 |
AR240608A1 (en) | 1990-06-30 |
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