Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Web – sheet or filament bases; compositions of bandages; or...
Reexamination Certificate
1999-05-21
2004-03-30
Travers, Russell (Department: 1617)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Web, sheet or filament bases; compositions of bandages; or...
C424S443000, C424S444000, C424S445000, C424S447000, C428S408000, C530S501000, C530S501000
Reexamination Certificate
active
06713083
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon PCT Application Serial No. PCT/GB97/00638, filed Mar. 7, 1997, which claims priority from European Patent Application Serial No. 9605422.6, filed on Mar. 15, 1996.
The present invention relates to coated bioabsorbable beads for use in a wound dressing or wound implant.
It is known to use collagen-based bioabsorbable beads for augmenting soft tissue in wound dressings and wound implants. U.S Pat. No 4,837,285 describes the use of collagen matrix beads, the beads being formed from a sponge of resorbable collagen. The beads have an average pore size of from 50 to 350&mgr;m, with the collagen comprising from 1 to 30% by volume of the beads. The size of the beads is preferably from 0.1 to 4 mm diameter. The collagen matrix is sufficiently open to simulate cellular ingrowth therethrough, and yet sufficiently stiff and non-compressible to fill and protect a wound, and sufficiently moisture and gas permeable to prevent liquid pooling on a wound and to permit sufficient oxygen diffusion for promoting wound healing.
EP-A-0648480 describes wound implant materials comprising a plurality of bioabsorbable microspheres bound together by a bioabsorbable matrix. The microspheres are preferably hollow microspheres or microcapsules bound together in a freeze-dried matrix. Preferably, at least 90% of the microspheres have diameters between 0.2 and 1.0 mm. The use of closely packed microspheres having controlled diameters is said to allow good control over the porosity of the implant material.
A need remains for improved materials for use in wound dressings and wound implants. Such a material should preferably be inexpensive and easy to manufacture in a range of wound treatment formats. The material should preferably be fully bioabsorbable and non-antigenic. The material should preferably allow precise control of wound healing kinetics so as to assist rapid wound healing with minimum scarring.
It is an object of the present invention to provide a material for use in a wound dressing or wound implant having the desirable properties listed above.
It is a further object of the present invention to provide a method of making bioabsorbable beads for use in a material for use in wound dressings or wound implants having the desirable properties listed above.
The present invention provides a material for use in a wound dressing or a wound implant. The material comprises a plurality of beads, wherein each bead comprises a porous core of a first bioabsorbable material and a substantially non-porous layer of a second bioabsorbable material around said core.
The first and second bioabsorbable materials may be any materials that are fully absorbable in the mammalian body. Such materials include synthetic bioabsorbable materials commonly used for surgical sutures, implants and the like, for example absorbable polymers and copolymers made from poly-glycolide, poly-lactide, &egr;-caprolactone, p-dioxanone, trimethylene carbonate and dimethyl trimethylene carbonate monomers.
Preferably, the first and second bioabsorbable materials are biopolymer materials or chemically modified biopolymer materials. Such materials include polysaccharides such as oxidised regenerated cellulose, alginates, chitosan or naturally occurring gums such as guar gum, xanthan gum or the like. Suitable biopolymers also include glucosaminoglycans, such as hyaluronic acid, chondroitin sulphate, heparin and heparan sulphate. However, the preferred biopolymers are hyaluronic acid and its salts, and the structural proteins such as collagen, fibrin, laminin or fibronectin. More preferred is collagen, which encompasses all collagen types including type I collagen, type II collagen, atelocollagen, pepsin-solubilised collagen and gelatin. Fibrous, insoluble collagen is most preferred.
Collagen is preferred because of its low antigenicity, ready availability at moderate cost, and well-understood properties.
Preferably, the first bioabsorbable material consists essentially of collagen. More preferably, both the first and second bioabsorbable materials consist essentially of collagen.
The porous core of the first bioabsorbable material is preferably a bioabsorbable sponge, for example a product of freeze-drying (lyophilising) or solvent drying a frozen liquid dispersion of the biopolymer. Such sponges generally have irregular, interconnected pores. Preferably, the average pore diameter is in the range of 50 &mgr;m to 350 &mgr;m, which is thought to be the optimum size range for fibroblast ingrowth.
Preferably, the beads are substantially spherical. More preferably, the substantially spherical beads comprise a substantially spherical porous core enclosed in a substantially non-porous layer of substantially uniform thickness.
Preferably, the mean outside diameter of the beads in the range 0.1 to 4.0 mm. More preferably, the mean outside diameter of said beads is in the range 0.2 to 1.0 mm. Preferably, the layer of the second bioabsorbable material is of substantially uniform thickness. Preferably, the average thickness of said layer is in the range 0.01 mm to 1.0 mm, more preferably 0.02 mm to 0.1 mm. Preferably, said layer forms a substantially continuous coating over the core to substantially prevent cellular invasion of the core until the layer has fully degraded in the body.
The beads may also comprise an active therapeutic agent in the porous core and/or in the layer around the core. Preferred active therapeutic agents include growth factors such as TGF&bgr;, platelet derived growth factor (PDGF) or fibroblast growth factor (FGF) that can promote the ingrowth of wound healing cells. The beads are especially suitable for achieving slow, more especially phased release of active therapeutic agents at the wound site. Such agents can include antiseptics such as chlorhexidine or silver sulphadiazine, antibiotics such as a penicillins or a tetracyclins, steroids such as cortisone or prednisone, or non-steroidal anti-inflammatory drugs such as Ibuprofen, naproxen or acetaminophen. Phased release of the active therapeutic agents can be achieved by having different concentrations of one or more different active agents in the porous core and the outer layer of the bead, respectively.
In certain preferred embodiments the material according to the present invention is a fluid, gel or paste comprising the coated beads as described above dispersed in a pharmaceutically acceptable liquid or gel carrier. The carrier can be a non-toxic base for forming an ointment, gel or injectable fluid incorporating the coated beads. The carrier is preferably an aqueous carrier, and may also comprise a polyhydric alcohol such as propyleneglycol as a humectant, a pharmaceutically acceptable gelling agent such as gelatin, or hyaluronic acid and its salts. The carrier may include pharmaceutical active agents, including any one or more of the pharmaceutical active agents for the beads enumerated above.
In other preferred embodiments the material according to the present invention may be a solid wound implant material comprising a plurality of the coated beads bound together by a bioabsorbable matrix, as described and claimed in our pending European patent application EP-A-0648480, the entire contents of which are expressly incorporated herein by reference.
Preferably, the matrix is a solid bioabsorbable material, preferably formed by freeze-drying an aqueous dispersion of a bioabsorbable material that has been used to bind the coated beads.
Preferably, the coated beads make up at least 30%, more preferably at least 40%, and most preferably at least 50% of the volume of the material according to the present invention.
The present invention also provides a method of making bioabsorbable beads for use in wound dressings or implants, the method comprising: providing a dispersion of a first bioabsorbable material in a liquid solvent; generating droplets of the dispersion; freezing the droplets to form frozen droplets; freeze-drying or solvent drying the frozen droplets to form discrete porous cores of said first bioabso
McGregor James
Watt Paul W.
Johnson & Johnson Medical Ltd.
Sharareh S
Shatynski Theodore
Travers Russell
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