EP0793512A1 - Structures orthopediques synthetiques a base de collagene telles que des greffons, des tendons et autres - Google Patents

Structures orthopediques synthetiques a base de collagene telles que des greffons, des tendons et autres

Info

Publication number
EP0793512A1
EP0793512A1 EP95941360A EP95941360A EP0793512A1 EP 0793512 A1 EP0793512 A1 EP 0793512A1 EP 95941360 A EP95941360 A EP 95941360A EP 95941360 A EP95941360 A EP 95941360A EP 0793512 A1 EP0793512 A1 EP 0793512A1
Authority
EP
European Patent Office
Prior art keywords
fibers
bundle
collagen
fiber
biodegradable
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP95941360A
Other languages
German (de)
English (en)
Inventor
Frederick H. Silver
Yasushi Pedro Kato
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of Medicine and Dentistry of New Jersey
Rutgers State University of New Jersey
Original Assignee
University of Medicine and Dentistry of New Jersey
Rutgers State University of New Jersey
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by University of Medicine and Dentistry of New Jersey, Rutgers State University of New Jersey filed Critical University of Medicine and Dentistry of New Jersey
Publication of EP0793512A1 publication Critical patent/EP0793512A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F4/00—Monocomponent artificial filaments or the like of proteins; Manufacture thereof
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/08—Muscles; Tendons; Ligaments
    • 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
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
    • A61L27/40—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material
    • A61L27/44—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material having a macromolecular matrix
    • A61L27/48—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material having a macromolecular matrix with macromolecular fillers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
    • A61L27/50—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
    • A61L27/58—Materials at least partially resorbable by the body
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2310/00—Prostheses classified in A61F2/28 or A61F2/30 - A61F2/44 being constructed from or coated with a particular material
    • A61F2310/00005—The prosthesis being constructed from a particular material
    • A61F2310/00365—Proteins; Polypeptides; Degradation products thereof

Definitions

  • This invention relates to high strength reconstituted collagen fibers which are particularly well suited as grafts for orthopaedic, dermal, cardiovascular, and dental implants, prosthesis and other applications particularly in living subjects, like animals, especially human subjects.
  • the fibers and grafts of the invention overcome many of the prior art difficulties and problems and have a combination of advantageous properties generally absent in the prior art.
  • the collagenous fibers and grafts of the invention can be manufactured without sacrifice of the host's tissue.
  • the graft of the invention quickly incorporates repair tissue, a necessary characteristic in the design of biomaterials that enhance the deposition of repair tissue in skin, tendon and the cardiovascular system.
  • collagen fibers of small diameter that can be processed into woven and non-woven textile prostheses which have the necessary properties that simulate or exceed those of the natural body part.
  • the collagen fibers of the invention are especially well suited for the repair of soft tissue injuries.
  • “Graft” means anything inserted into something else, or contacted upon something else so as to become an integral or associated part of the latter and it includes materials and substances which are either added to an already intact structure or serve as a replacement substitute or repair to a damaged or incomplete structure.
  • a “graft” is intended to be given the broadest possible meaning and encompasses a prothesis, implant or any body part substitute for any mammal (animal or human) .
  • Weight when referring to fibers or embodiments of the invention means more than 15% water content. "Dry” means 15% or less water conten .
  • the invention provides a high strength collagen fiber for grafts, as well as a method for the manufacture of the high strength collagen fibers.
  • the invention further provides a bundle of monofilament collagen fibers arranged in parallel in which the fibers are tensioned by stretching so that the bundled fibers retain a high percentage of their individual strength and so that the fibers fail simultaneously.
  • the invention further provides a method for the production of monofilament collagen fibers arranged or organized in parallel in which the fibers are tensioned by stretching so that the bundled fibers retain a high percentage of their individual strength and so that the fibers fail simultaneously.
  • the invention further provides a prosthetic device, such as a tendon or a ligament device, made from a multiplicity of the tensioned fibers arranged in parallel or from a multiplicity of the bundles arranged in parallel.
  • the invention also provides collagen devices like fibers and grafts for numerous applications, particularly where high tensile strength and biocompatibility are essential.
  • the invention also provides collagen proteoglycan fibrous grafts which have even greater tensile strength than the non- proteoglycan grafts of the invention.
  • the invention further provides a method for making improved collagen proteoglycan fibers for use in such grafts.
  • the invention provides further implants in which the collagen grafts are woven and secured into the surrounding tissue. The surrounding tissue then invades the graft material. The graft is revascularized and eventually replaced by the host's tissues.
  • the invention further provides for grafts with physical properties that can be manipulated or processed into a variety of shapes, thicknesses, stiffnesses in woven or non-woven forms.
  • One such embodiment is an improved biodegradable and biocompatible reconstituted monofilament collagen fiber which has increased strength and elasticity of the fiber when compared to fibers made by other than the method of the invention.
  • the fibers may be made from soluble or insoluble collagen and may be crosslinked or not crosslinked.
  • the fibers may be stretched from 2.5% to 100% of their length to increase the strength of the fibers. Generally, the fibers are stretched until the strength of the fibers reaches a maximum level. The stretching may be performed in a single stretching application or may be performed by repeated cycles of stretching, drying, wetting, and stretching as deemed appropriate under the circumstances.
  • the fibers may be left uncoated or may be coated with a suitable material, preferably biocompatible and biodegradable, to protect the fiber from the environment and from trauma during handling.
  • the coating is applied as a low weight fraction of the fibers, generally less than 10% of the weight of the fibers.
  • the fibers may or may not be embedded in a matrix compound of a suitable material, preferably biocompatible and biodegradable, to strengthen the fibers by binding the fibers together in a fiber/matrix composite.
  • the matrix is applied in a high weight fraction of the fibers, generally more than 10% of the weight of the fibers.
  • Proteoglycans may or may not be incorporated into the interfibrillar spaces to increase the tensile strength of the fibers.
  • a method for the production of the improved biodegradable and biocompatible collagen fibers is another embodiment of the invention.
  • Another embodiment is a bundle of physically associated collagen fibers arranged in parallel, or substantially parallel, in which the fibers are tensioned by stretching so that the fibers each have the same, or substantially same, strength and fail in, or substantially in, unison at the same load.
  • the bundles of the invention retain a high percentage, generally more than about 50%, of the combined strength of the individual fibers.
  • the load to failure of the bundle was about 60% of the calculated cumulative load to failure of the individual fibers.
  • the fibers of the bundle may or may not be coated or embedded in a matrix as described for the monofilament fibers.
  • Proteoglycans may or may not be incorporated in the bundle as described for the monofilament fibers.
  • a process for making bundles of fibers in which the fibers are tensioned and fail in unison or substantially in unison at the same or substantially the same load comprises the following. Fibers made in accordance with the invention, as disclosed in the parent applications, are attached at each end to a tensioning device which stretches the fibers from about 2.5 to about 100.0%, preferably from about 5 to about 7.5% of their original length. The stretching results in an increase in strength of the fibers and, very importantly, results in uniform strength of the fibers. Fibers other than those made by the process of the invention can likewise to treated in the same manner.
  • Another embodiment of the invention is a prosthetic device for a graft, such as a tendon or ligament device, which comprises the tensioned fibers of the invention, aligned in parallel, either bundled or unbundled.
  • the tendon or ligament prosthetic device has increased strength, compared with tendon or ligament devices comprising fibers made by means other than that of the invention, as the individual fibers of the device are stronger and fail in unison.
  • the invention as disclosed in the parent applications, has several embodiments.
  • the invention provides a high strength synthetic collagen graft constituted of high strength reconstituted crosslinked collagen fibers embedded into a loose uncrosslinked collagen matrix.
  • the grafts of the invention are biologically compatible with a host. They simulate the morphological and biomechanical characteristics of the host's natural tissue.
  • high molecular weight chondroitin sulfate proteoglycan is added during the latter stages of collagen fiber synthesis to be incorporated into interfibrillar spaces and as a result enhances the ultimate tensile strength of the collagen fibers formed.
  • a further embodiment of the invention is a process for the manufacture of the reconstituted collagen fibers.
  • the fibers of the invention are prepared from soluble or insoluble collagen.
  • the collagen is in solution or dispersion in an acid solution.
  • the solution or dispersion is extruded through polyethylene tubing into a fiber formation buffer ("FFB") .
  • FFB fiber formation buffer
  • the fibers are then successively bathed in alcohol, to dehydrate the fibers, and then again in water, following which the fibers are dried and wound on a tensioning spool. Prior to drying, as the wet fibers are collected and tensioned on the spool, the fibers may be stretched, up to about 100% of their original length. It was a surprising finding that for production of optimum strength in the manufactured fibers a water bath following the dehydration bath was so highly desirable. Methods of forming collagen fibers without this water bath yield fibers of inferior strength.
  • Other embodiments of the invention will become apparent to one of average skill in the art to which the invention pertains.
  • Figure l shows a diagrammatic example of an automated method for production of continuous collagen fibers.
  • Figure 2 is a diagram outlining the various embodiments of the fibers of the invention.
  • Figure 3 shows ultimate tensile strength of collagen fibers which were stretched by varying percentages of the original lengths of the fibers. Fibers stretched 5.0% had an increase in tensile strength of about 50%. Fibers stretched 7.5% had an increase in tensile strength of about 57%.
  • Figure 4 shows load at failure of collagen fibers which were stretched by varying percentages of the original lengths of the fibers. The most dramatic increase in strength occurred at 5.0% stretch, which resulted in an increase in strength of about 160%. Fibers stretched 7.5% of their length almost doubled their strength. Fibers stretched by more than 7.5% or less than 5.0% had smaller strength gain, although these fibers were still stronger than control fibers.
  • Figure 5 shows strain at failure of collagen fibers which were stretched by varying percentages of the original lengths of the fibers. All stretched fibers had a higher amount of strain at maximum (point of breakage) . Fibers stretched 5.0% had the highest strain at maximum.
  • Figure 6 shows modulus (stress/strain) at low levels of applied stress of collagen fibers which were stretched by varying percentages of the original lengths of the fibers.
  • Figure 7 shows modulus (stress/strain) at high levels of applied stress of collagen fibers which were stretched by varying percentages of the original lengths of the fibers.
  • Collagen fibers are placed in or passed through a fiber formation buffer ("FFB") .
  • the collagen precursor fibers which are placed in the FFB may be soluble fibers in solution or insoluble collagen in a dispersion in a dilute acid solution.
  • the precursor collagen in the acid solution may be extruded through tubing with the desired diameter to yield fibers of the desired thickness.
  • the FFB may be an aqueous buffer which may contain neutral salts or it may be composed solely of distilled water.
  • the FFB comprises NaCl, TES (N- Tris(hydroxymethyl) methyl-2-aminoethane sulphonic acid), and sodium phosphate dibasic. Chemically similar or equivalent compounds may also be used as well as other collagen fiber formation buffers well known in the art.
  • the temperature of the fiber formation buffer should be sufficiently high to allow fiber formation to occur but should not be so high as to disturb the fiber formation process. Generally temperatures between about 4° to about 4i°C have been found to be suitable.
  • the pH of the FFB should be higher than the isoelectric point. A pH about 7.5 has been found to be acceptable.
  • the fibers remain in the FFB for a period of time sufficient to allow the fibers to become strong enough to support their own weight when lifted from the FFB.
  • the necessary time will vary depending on the temperature of the FFB, with lower temperatures requiring a longer immersion in the buffer. At higher temperatures, an immersion of 15 minutes may be sufficient whereas at lower temperatures, an immersion of 8 hours may be necessary at low FFB temperatures.
  • the water is removed from the collagen.
  • Water removal can be achieved by immersing the fibers in a dehydrating solvent, such as an alcohol for a period of time sufficient to remove of the water from the fibers, or may be achieved by air drying.
  • a dehydrating solvent such as an alcohol
  • the length of time of for this step will vary. Using an alcohol, times from 30 minutes to several hours may be employed. Any alcohol may be used which effects water removal from the collagen. That is, the solubility parameter of water in the alcohol used must be high.
  • alcohols are suitable for the dehydration step include lower alkanols (up to 6 carbon atoms), like methyl, ethyl, and isopropyl alcohols.
  • the fibers are placed in a water bath for a time sufficient to remove the excess solvent and other chemicals and to allow the fibers to align in or near parallel during the subsequent drying process.
  • the length of time required varies inversely with the temperature of the water bath. Generally, water temperatures between about 4° and about 41°C have been found to be suitable, with longer immersion times being required at lower water temperatures.
  • the water is preferably ion free water which may be distilled water.
  • the fibers are dried. The drying may be by air drying at room temperature or an external heat source, such as a «at lamp may be used. in a preferred embodiment, the drying is performed with the fibers under tension. Drying should preferably continue until the fibers retain from 0% to about 30% moisture by weight. Preferably, the fibers are dried to retain about 15% moisture by weight.
  • the collagen fibers are collected.
  • the fibers are collected onto a spool under tension.
  • the collagen fibers may be formed using a manual method such as the method described above or by means of a continuous automated process, such as described in Kato and Silver, Formation of Continuous Collagen Fibres: Evaluation of Biocompatibility andMechanical Properties, Biomaterials, 11:169- 175 (1990) which is incorporated herein by reference.
  • An automated method for production of continuous collagen fibers may be performed as follows: A collagen solution or dispersion is extruded through a continually flowing solution of FFB with the aid of a syringe pump (Sage Instruments, Cambridge MA) containing the collagen dispersion.
  • a micro gear pump Cold-Cene Palmer, Chicago, IL
  • a conveyor belt mechanism is used to carry the fibers through the various processes.
  • the fiber formation buffer is recycled and reheated to the desired temperature by a pump system.
  • the extruded collagen flows down a tubing conveyed under the flow of the fiber formation buffer and is collected on a conveyor belt.
  • the belt carries the collagen fiber via a pulley mechanism designed to immerse the belt in solution through an alcohol bath, followed by a water bath.
  • the fiber is then picked up by a spool a distance from the conveyor belt, drying under tension with a heat lamp during the time of travel between the conveyor belt and the spool.
  • Figure 1 A diagrammatic representation of an automatic process to produce continuous collagen fibers is shown in Figure 1.
  • the fibers may be treated in various ways to produce the various embodiments of the invention.
  • An outline of the treatment of the fibers is illustrated in Figure 2.
  • the bundles of the invention are comprised of a multiplicity of suitable monofilament collagen fibers bundled together in parallel alignment.
  • a method of making suitable collagen fibers is detailed herein, but other suitable methods can be used to make collagen fibers to be bundled in accordance with the invention.
  • Monofilament collagen fibers are placed side to side in parallel alignment to form a bundle.
  • the bundle may be placed in a fiber formation buffer solution or may be left dry.
  • the wet bundle is stretched.
  • the bundle is then air dried at which time the monofilaments will have become associated to form a single bundle.
  • the term "associated" in the context of the bundles means that the fibers are in contact with each other substantially throughout the entire lengths of the fibers and that the contact between the fibers is self-sustaining. If desired, the fibers of the stretched bundle may be crosslinked.
  • a bundle of collagen fibers of the invention comprises a multiplicity of fibers generally over 5 and may include several hundred fibers. For most applications, bundles comprising 7 to 15 fibers are suitable. For certain applications bundles comprising from about 2 fibers to about 100 fibers seem more suitable; for other applications, bundles comprising 100 fibers to about 10,000 fibers may be better suited. The number of fibers in what is termed a "bundle" is suited to the particular application or use selected.
  • Any suitable FFB may be used to wet the fibers for bundling in accordance with the method of the invention. Any of the FFBs described above to make the collagen fibers may be used in the bundling .process.
  • the tensioning of the fibers is carried out by any suitable means, such as a stretching device which may be a screw driven frame to which parallel oriented supports, which may be tongue depressors, are clamped at each end using screws.
  • a stretching device which may be a screw driven frame to which parallel oriented supports, which may be tongue depressors, are clamped at each end using screws.
  • the ends of collagen fibers to be stretched are attached to the supports by any suitable means so that the fibers do not slip when stretched.
  • the supports are separated, thus stretching the fibers, by turning a screw.
  • the amount of stretching can be adjusted by number of turns of the screw.
  • the stretching device acts like a rack to stretch the fibers.
  • the stretching device is manufactured from means (mechanical or otherwise) which accomplish the desired stretching function.
  • the fibers are stretched or tensioned to a degree that, when compared to unstretched fibers, the stretched fibers have increased strength.
  • the stretching, or tensioning, of collagen fibers, whether in bundles or as monofilaments, results in an increase in tensile strength of the fibers, especially when fibers are stretched from about 2.5 to about 10.0% of their original lengths. It has been found, in accordance with the invention, that the increase in strength of stretched fibers is optimal when fibers are stretched from 5.0 to 7.5% of their original length. See Figure 3. Stretched fibers have higher load at failure and strain at failure than unstretched fibers, the increase being most pronounced with stretching from 5.0 to 7.5% of the fibers' original lengths. See Figures 4 and 5. Additionally, stretched fibers are less stiff than unstretched fibers, especially with higher degrees of applied stress. See Figures 6 and 7.
  • the monofilament and bundled fibers of the invention having higher tensile strength than fibers previously known in the art, are especially well suited for implants requiring long lasting strength of fibers.
  • bundles of fibers made in accordance with the invention were found to retain a high percentage, approximately 60%, of the predicted strength computed by multiplying the load at failure of individual fibers times the number of fibers in the bundle. This compares favorably with other known methods of bundling fibers which result in a loss of up to 70 to 80% of predicted strength.
  • the bundle may be coated with a suitable protective material. Individual unbundled fibers may also be coated. The bundle may be embedded in a matrix. Individual unbundled fibers may also be embedded in a matrix.
  • the coating or matrix material is a biodegradable and biocompatible polymer, which may be a synthetic or natural polymer, and may be water or non-water soluble. Suitable polymers include water soluble polymers derived from natural sources, such as alginates, pectins, gelatins, and polysaccharides, and synthetic polymers such as polylactic acid, polyglycolic acid, polyurethane, and copolymers thereof.
  • the coating is performed by covering the bundles or the unbundled fibers with a liquid coating material.
  • the coating is performed by dipping the stretched bundles into, or running the fibers through, the liquid coating material, or spraying the coating material onto the bundles or fibers until the bundles or fibers are coated. Generally, less than a 10% weight fraction of coating material is applied to the fibers. After coating, the bundles may be dried and crosslinked.
  • Embedding of the bundled or unbundled fibers in a matrix is performed in substantially the same way as the coating. However, a higher weight fraction of matrix compound is used than is used in coating so that the matrix compound becomes embedded between the fibers of the bundle. When applying a matrix to unbundled fibers, the matrix is applied as a coating.
  • the collagen fibers may be embedded in a biodegradable and biocompatible polymer matrix to bind the fibers together.
  • the procedure for producing the matrix/fibers composite may be identical to the process for coating except that a higher weight portion of the matrix is used, greater than 10% of the fibers.
  • the tendon or ligament prosthetic devices for grafts of the invention are constructed as follows.
  • the device may be made in various ways, as illustrated in Figure 2.
  • individual fibers made in accordance with the invention are placed in parallel alignment.
  • the fibers are made into bundles and the ends of each bundle is secured.
  • the parallel fibers are wrapped with a braided bundle of fibers.
  • the parallel fibers are secured at each end to form the final device.
  • fibers are made into bundles which are then wetted, stretched, and dried. The stretched bundle may be crosslinked. The bundles are arranged in parallel and secured at the ends to form the final prosthetic device.
  • the parallel bundles are wrapped with a bundle of fibers which may be braided. The ends of the parallel bundles are secured to form the prosthetic device.
  • the graft of the invention has numerous applications which can assume different physical embodiments or different geometrical shapes.
  • the synthetic collagen graft material of the invention is useful as a mesh, sheet, film, tube, circular casing, filament, fiber or as a woven or non-woven fabric.
  • the graft material comprise collagen fibers with a dry diameter in the range of about 20-60 microns.
  • the diameter of the wet collagen fibers may be much greater, often 1.5 to more than 2 times as thick.
  • the collagen fibers used in the grafts of the invention have tensile strengths in the range of about 30 to about 91 MPa. It is a noteworthy aspect of the invention that the fibers of the invention can have ultimate tensile strengths exceeding that of autograft materials or naturally occurring tendon fibers in laboratory animals.
  • the fibers of the invention also have improved strength compared to fibers made by means other than the method of the invention.
  • the collagen materials of the invention can have an index of refraction in the range of about 1.4 to about 1.7, generally about 1.6.
  • the graft material is biodegradable with the host's naturally produced repair tissue supplanting the graft material. Furthermore, the graft is biologically, morphologically and biomechanically compatible with surrounding tissue of the subject treated.
  • proteoglycans are associated with the collagen fibers of the invention.
  • the extruded fibers are immersed in a fiber formation buffer containing the proteoglycan.
  • the fibers are Soaked for a sufficient time at an appropriate temperature to cause the proteoglycan to be incorporated into the fibrous structure.
  • the fibers can be soaked for 60 minutes at 37°C.
  • the fibers are then rinsed with appropriate liquids to remove excess proteoglycan and dried. Soaking temperature can be in the range from about 15°C to 50 or 60°C with either longer or shorter soaking periods, as may be desirable.
  • this embodiment of the invention may be prepared as follows.
  • Proteoglycans in a concentration between 0.01 and 0.02 g/100 ml were added to the fiber formation buffer and stirred.
  • a 1% w/v collagen dispersion was placed in a syringe to which polyethylene tubing of internal diameter 0.58 mm was attached.
  • Fibers were extruded into a fiber formation buffer.
  • the fiber formation buffer is composed of l35mM NaCl, 30mM TES (N-Tris(hydroxymethyl) methyl -2- aminomethane sulfonic acid) and 30mM sodium phosphate dibasic.
  • the final pH is adjusted to about the neutral range such in the range of about 6.5 to 7.5. Chemically similar or equivalent compounds may also be used as well as other collagen fiber formation buffers well 22
  • the extruded fibers were left in the tray containing fiber formation buffer for 60 minutes. The buffer was maintained at 37°C. The buffer was removed and replaced by isopropanol. The fibers were soaked in isopropanol overnight and were then soaked in distilled water for 15 minutes. The fibers were then removed from the distilled water and air dried under tension. The extruded collagen fibers were then crosslinked by exposure to glutaraldehyde. Fibers which were formed in the presence of high molecular weight proteoglycan were found to have significantly increased ultimate tensile strengths compared to low molecular weight, chondroitin sulfate, glycosaminoglycans or controls. Furthermore collagen fibers formed in the presence of high molecular weight proteoglycans exhibit higher tensile strength than collagen fibers that are crosslinked. Further details are given in Example III below.
  • the high molecular weight proteoglycans which are generally preferred in the invention are large proteoglycans with a core protein with a molecular weight greater than about 100,000 and glycosaminoglycans chain with a molecular weight greater than about 5,000.
  • proteoglycan generally have a molecular weight of the range of about 1,000,000 to about 3,000,000 typically about 1,200,000.
  • Other proteoglycans desirable for use in the invention include large proteoglycans from tendon with chondroitin sulfate chains of average molecular weight of 17,000 and a core protein molecular weight of 200,000. It is not unlikely that other proteoglycans will also be useful in the invention providing they impart the desirable properties to the collagen fibers, in particular the desired tensile strength.
  • the fibers are collected.
  • the collected fibers are shaped, pressed or formed into sheets, tubes and numerous other shapes of varying dimensions and thickness as desired for the particular application.
  • the fibers can be processed into woven materials. They can be packed with various pharmacologically active agents. These structures then can be directly used as the graft, prosthesis or implant of the invention depending on the need and how the particular structure has been prepared.
  • the fibrous graft can be woven or secured to surrounding tissue as an implant or graft or topically applied and topically secured.
  • EXAMPLE I Collagen fibers were prepared from a 1% (w/v) dispersion of insoluble type I collagen derived from bovine corium in dilute HC1, pH 2.0. This collagen dispersion was extruded through polyethylene tubing with an inner diameter of 0.28mm into a 37°C bath of aqueous sodium phosphate fiber formation buffer as described elsewhere. After immersion of 45 minutes, the fibers were placed in isopropanol for at least four hours. They were then rinsed in distilled water for 15 minutes and allowed to air dry under tension overnight.
  • Fibers were placed in a sealed desiccator containing 10 ml of a 25% (w/v) glutaraldehyde solution at room temperature and allowed to vapor crosslink for 24 hours.
  • collagen fibers were placed in an oven at 110°C in a vacuum of between 50 and 100 m torr for 72 hours. These fibers were then placed in a sealed desiccator containing 20 g of cyanamid in 5 ml of distilled water for 24 hours.
  • Prostheses containing 200 to 250 individual crosslinked collagen fibers were coated with a 1% (w/v) collagen dispersion in HC1, pH 2.0, air dried overnight and then extensively washed in distilled water.
  • One ml Alcide ® activator and one ml Alcide ® base were added to 10 ml of distilled water and after 10 minutes diluted with 24 ml of phosphate buffer solution.
  • Each implant was immersed in this cold sterilant for at least four hours, and then soaked in one liter of sterile physiological saline prior to implantation.
  • EXAMPLE II Reconstituted Collagen Fibers Insoluble collagen type I from fresh, uncured corium was obtained from Devro, Inc. (Somerville, NJ, USA) .
  • a 1% (w/v) dispersion of type I collagen in dilute HC1, ph 2.0 was prepared by adding i.2g of lyophilized collagen to 120ml of HC1 solution in a blender (Osterizer) and mixing at a speed of 10,000 rev min "1 for 4 min. The mixture was allowed to settle for 10 min and then remixed at 10,000 rev min "1 for 4 min. The resulting dispersion was placed under a vacuum of 0.01 m torr at room temperature to remove any trapped air bubbles.
  • Collagen fibers were produced by extruding the collagen dispersion through polyethylene tubing with an inner diameter of 0.28 mm into a 37°C bath of aqueous fiber formation buffer composed of 135mm NaCl, 30mM TES (N-Tris(hydroxymethyl) methyl - 2- aminomethane sulfonic acid) and 30mM sodium phosphate dibasic. The final bath pH was adjusted to 7.5 by adding 5.On NaOH drop- wise. Fibers were allowed to remain in the buffer for 45 min, and then placed in 500 ml of isopropyl alcohol for at least 4 hours. The fibers were immersed in distilled water for 15-20 min and air dried under tension.
  • aqueous fiber formation buffer composed of 135mm NaCl, 30mM TES (N-Tris(hydroxymethyl) methyl - 2- aminomethane sulfonic acid) and 30mM sodium phosphate dibasic.
  • the final bath pH was adjusted to 7.5 by adding 5.On NaOH drop- wise. Fibers were allowed to
  • Collagen fibers were crosslinked using glutaraldehyde or by a combination of severe dehydration and treatment with cyanamid.
  • Glutaraldehyde crosslinking was accomplished by placing air-dried collagen fibers in a sealed desiccator containing 10 ml of a 25% (w/v) aqueous glutaraldehyde solution in a petri dish. The fibers were placed on a shelf in the desiccator and were crosslinked in a glutaraldehyde vapor for 1-4 d at room temperature.
  • Collagen fibers were also cross-linked by placing in an oven at 110°C and at vacuum of 50-100 m torr for 3 d.
  • DHT dehydrothermal crosslinking
  • Acid soluble type I collagen was extracted from tail tendons of young rats.
  • the tendons were stripped from the tails and dissolved in 0.01 M HC1 at 4°C followed by centrifugation for 30 min. at 30,000 X g.
  • the supernatant was sequentially filtered through 0.8. , 0.65, and 0.45 ⁇ m Millipore filters.
  • the collagen preparation was analyzed by SDS polyacrylamide gel electrophoresis and amino acid analysis.
  • the raw material (bovine corium) was prepared from fresh uncured bovine hide which was obtained from Devro, Inc. (Somerville, N.J.). The hides were split into two components, the grain layer (papillary dermis) and the corium (reticular dermis) . Fresh corium was frozen and stored at -20°C until it was used. One liter of the frozen raw material was defrosted at room temperature and placed in an 18 liter Nalgene processing tank (Consolidated Plastics, Twinsburg, Ohio) , equipped with air and water lines. Distilled water was added until the total volume of the processing mixture reached 14 liters.
  • the liquid phase was then removed using a Becton siphon pump (Consolidated Plastic, Twinsburg, Ohio) and 8 liters of 99.8% isopropyl alcohol was mixed with the solid phase. The mixture was then placed on the shaker for another 12 hours. After removal of the liquid phase, the material was washed with 2 liters of distilled water, poured into plastic trays and placed in a freezer until frozen solid.
  • Becton siphon pump Consolidated Plastic, Twinsburg, Ohio
  • the frozen material was then placed in the cold trap of a freeze dryer (Freeze Mobile 12, Virtis, Inc., Gardner, N.Y.) at -65°C. A vacuum of 10 microns was then applied for 48 to 96 hours. The vacuum was then released and material removed. The freeze dried collagen was removed from the trays and stored in air tight bags.
  • a freeze dryer Freeze Mobile 12, Virtis, Inc., Gardner, N.Y.
  • CS-PG Chondroitin sulfate proteoglycan
  • DS-PG dermatan sulfate proteoglycan
  • PGi articular cartilage
  • FIBRIL ASSEMBLY STUDIES Turbidity-Time Studies Lyophilized soluble type I collagen was dissolved at l mg/ml in HC1, pH 2.0, stirred at 4°C for 24 hours, dialyzed against HC1, pH 2.0, centrifuged at 1600 g for 60 minutes and the supernatant was then filtered through a 0.65 ⁇ m Millipore filter. This collagen stock solution was stored at 4°C for periods of up to one week.
  • Fibril formation was initiated by mixing 0.9 ml of a collagen solution with 0.1 ml of buffer on ice to give a final composition of 30 M n-tris [hydroxymethyl]methyl-2- aminoethanesulfonic acid (TES) , 30 mM phosphate and NaCl to a final ionic strength of 0.225 at pH 7.3.
  • Cuvettes were filled with sample, sealed and transferred to a water-jacketed sample compartment of a Gilford Model 250 spectrophotometer. The compartment was maintained at the desired experimental temperature and the absorbent was recorded as function of time.
  • Absorbent was defined as the natural logarithm of the ratio of the incident light and the scattered light intensities. Absorbent at 131 nm was converted to turbidity by multiplying by 2.303.
  • Collagen concentrations between 0.20 and 0.45 mg/ml and proteoglycan concentration between 0.001 and 0.2 g/lOOm were evaluated at temperatures from 27 to 37°C.
  • aqueous fiber formation buffer composed of 135 mM NaCl, 30 mM TES and 30 mM sodium phosphate dibasic at a final pH of 7.5 was heated to 37°C in a temperature controlled water bath.
  • Glycosaminoglycan concentration between 0.001 and 0.2 g/l00 ml
  • proteoglycan concentration between 0.01 and 0.02 g/lOOml
  • a 1% w/v collagen dispersion (lg/iOOml) was placed in a syringe to which a polyethylene tubing (Clay Adams, PE-50) of internal diameter 0.58 mm was attached.
  • a syringe pump (Sage Instruments, Model 341A) at a speed of 7 ml/minute was used to extrude the fibers into fiber formation buffer. Extruded fibers were left in the tray containing fiber formation buffer maintained at 37°C for 60 minutes. Fiber formation buffer was then emptied out from the tray using a vacuum hose and was replaced by isopropanol and left overnight. Isopropanol was removed and was replaced by distilled
  • Collagen Fiber Crosslinking Extruded collagen fibers were crosslinked by exposure to glutaraldehyde vapor for 24 hours (Glut 1) at room temperature in a sealed desiccator as described previously.
  • Proteoglycan concentrations present on collagen fibers were also less than 1% (data not shown) . This is another distinctive characteristic of the fibers which are particularly useful in the invention.
  • Collagen monofilament fibers were prepared from soluble type I collagen from fetal calf skin.
  • Collagen fibers were prepared from 1% (w/v) solution of type I collagen in dilute HC1. The solution was extruded through polyethylene tubing with an inner diameter of 0.28 mm into a 37°C bath containing aqueous sodium phosphate fiber formation buffer. The fibers were extruded into a tray containing fiber formation buffer and then the fiber was pulled over a transfer device into a bath of isopropanol and then through a bath of distilled or demineralized water. The fiber left the last bath and was air dried using a heat lamp.
  • Bundles are made using about 400 monofilament fibers. Bundles are also made using about 10,000 monofilament fibers.
  • EXAMPLE VI Formation of Coated Bundle Collagen fibers were produced as in Example IV. Ten collagen monofilaments were placed side-by-side to form a bundle. A wet bundle of collagen fibers that was attached to support beams and stretched to 7 to 7.5% as described in Example V above was dipped in a 4% aqueous solution of sodium alginate at room temperature. The alginate coated bundle was then air dried and then crosslinked for 5 days at 110°C.
  • Collagen mono ilaments and bundles were mechanically tested while wet using an instron Model 1122 at a strain rate of 50% per minute using a 2 cm gauge length.
  • the materials were mounted on a 2 cm gauge length frame using 2 ton epoxy (Devron Corp., Denver, CO) .
  • Monofilaments and bundles mounted on paper frames were immersed in phosphate buffer solution (pH 7.5) for 25 minutes. The paper was cut and the samples were pulled to failure in tension. Load and strain at failure were found to be 38.0 g and 14.5% respectively for monofilament and 219 g and 10.5% for uncoated intermediate bundles.
  • This bundle retains 219 g of the predicted 380 g or 58% of the load to failure.
  • the bundle breaks uniformly, has a strain at failure of about 10% and can be fashioned into a tendon/ligament device by forming either thin tapes of intermediate bundles, braiding monofilament around a group of parallel bundles, or by wrapping monofilament around groups of parallel bundles.
  • One hundred collagen monofilament fibers are placed onto spools. The fibers are then tensioned in parallel by stretching them over a pulley. An outer layer of collagen fibers is wrapped or braided around the parallel fibers. The ends of the fibers are secured to stabilize the outer layer and to preserve the parallel alignment of the fibers.
  • the above process is performed using 400 and using 10,000 collagen monofilament fibers.
  • the fibers are tensioned in parallel and wrapped by an external layer of fibers which may be braided.
  • the ends of the parallel fibers are secured to stabilize the prosthetic device.
  • Ten stretched crosslinked bundles each having ten collagen monofilament fibers are placed in parallel.
  • An outer layer of collagen fibers is wrapped or braided around the parallel bundles.
  • the ends of the bundles are secured to stabilize the outer layer and to preserve the parallel alignment of the bundles.
  • the same process is performed using 400 collagen monofilament fibers in 40 bundles, each containing 10 fibers.
  • the process is performed using 10,000 collagen monofilament fibers in 1000 bundles, each containing 10 fibers.
  • the bundles are placed in parallel and wrapped by an external layer of fibers which may be braided.
  • the ends of the parallel bundles are secured to stabilize the prosthetic device.

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  • Health & Medical Sciences (AREA)
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  • Orthopedic Medicine & Surgery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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  • Cardiology (AREA)
  • Biomedical Technology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Vascular Medicine (AREA)
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  • Prostheses (AREA)

Abstract

L'invention se rapporte à une fibre de collagène monofilament améliorée, reconstituée, biodégradable et biocompatible, présentant une résistance et une élasticité améliorées. Le procédé de fabrication de la fibre, qui comprend une étape de passage dans un bain d'eau et une étape de déshydratation, est également décrit. L'invention porte en outre sur plusieurs modes de réalisation de la fibre de collagène, permettant d'obtenir des greffons, des dispositifs prothétiques et des faisceaux de fibres dans lesquels les fibres sont tendues ensemble de manière à présenter pratiquement le même seuil de rupture, ainsi que sur les procédés associés. Les fibres selon l'invention, ou leurs variantes, peuvent être enrobées d'un polymère ou noyées dans un polymère qui les protège et les relie entre elles. En outre, on peut incorporer des protéoglycanes dans les fibres afin d'en augmenter la résistance finale à la traction.
EP95941360A 1994-11-07 1995-11-07 Structures orthopediques synthetiques a base de collagene telles que des greffons, des tendons et autres Withdrawn EP0793512A1 (fr)

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US33554394A 1994-11-07 1994-11-07
US335543 1994-11-07
PCT/US1995/014308 WO1996014095A1 (fr) 1994-11-07 1995-11-07 Structures orthopediques synthetiques a base de collagene telles que des greffons, des tendons et autres

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EP1746952A1 (fr) * 2004-05-20 2007-01-31 Cook Incorporated Appareil endoluminal avec matériau de matrice extracellulaire et méthodes
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