Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Implant or insert
Reexamination Certificate
1998-02-27
2001-10-30
Dudash, Diana (Department: 1619)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Implant or insert
C424S444000, C514S953000
Reexamination Certificate
active
06309661
ABSTRACT:
The present invention relates to solid polysaccharide materials that are particularly suitable for use as wound dressings.
It is known to use biopolymers in both naturally occurring and chemically modified forms as wound dressings, either alone or in combination with other materials. Various biopolymers and derivatives have been found to accelerate wound healing, reduce infection and/or reduce scarring when used as wound dressings. The advantages of biopolymers can include low cost and low antigenicity. In addition, the water absorbency, gelling and humectant properties of biopolymers can help to maintain the desired fluid balance at the surface of the wound. In addition, many biopolymers are naturally bioabsorbable, which eliminates the trauma normally associated with removal of a non-bioabsorbable dressing from the surface of a wound. Finally, certain biopolymers such as collagen have been found to exhibit a positive therapeutic effect on wound healing by promoting the growth of certain wound healing cells. All of these advantages have resulted in much research activity in the field of biopolymer wound dressings, and a large number of patent applications.
The two main classes of biopolymers are polypeptides and polysaccharides. Of the polysaccharides, most interest has focused on wound dressings and wound treatment compositions containing alginic acid and the salts and derivatives thereof. Alginate gels, films, fibres and/or fabrics have been proposed as wound dressings. The solubility of the alginate is regulated by varying the ratio of sodium alginate (soluble) to calcium alginate (insoluble) in the compositions.
EP-A-0227553 describes a freeze-dried sodium/calcium alginate sponge for use as a wound dressing. The sponge is formed by mixing an aqueous solution of sodium alginate with a solution of calcium chloride in an inert atmosphere, followed by freeze-drying the mixture. We have found that alginate sponges formed in this way are either too soluble (at high sodium contents), or too brittle (at high calcium contents) to be optimal for use as wound dressings.
Many other polysaccharides have been proposed for use as or in wound dressing materials. These polysaccharides include glucosaminoglycans, such as hyaluronic acid and its derivatives and heparan, and other naturally occurring polysaccharides, especially chitin. It has also been suggested to use naturally occurring polysaccharide gums to form wound dressing gels. In particular, WO-A-9106323 and WO-A-9306802 teach the use of xanthan or guar gums as gelling agents in the preparation of wound dressing gels. However, these references do not appear to teach the use of freeze-dried sponges as wound dressings, and also do not appear to teach the use of gels containing both xanthan and a galactomannan gum, such as guar gum.
U.S. Pat. No. 4994277 describes aqueous gels containing xanthan for use in surgery to reduce tissue adhesions. The gels may also contain a galactomannan such as guar gum to increase viscosity or gelation.
U.S. Pat. No. 4341207 describes a multi-layer decubitus ulcer dressing including a wound contacting layer comprising a mixture of one or more water soluble or swellable hydrocolloids such as guar gum and a natural or synthetic viscous substance, such as a rubber, which acts as a binder for the hydrocclloids.
It is an object of the present invention to provide improved solid bioabsorbable materials for use as wound dressings. The desired properties for the improved materials include high liquid absorbency, durable but controllable consistency, low solubility in body fluids, bioabsorbability and low cost. The materials of the present invention further provide related advantages.
It is a further object of the present invention to provide a method of making solid bioabsorbable materials having the above desired characteristics.
Accordingly, the present invention provides a solid bioabsorbable material for use as a wound dressing, said material comprising at least 50% by weight of a mixture of xanthan and at least one galactomannan such that the weight ratio of xanthan: total galactomannans is 1:99 to 99:1.
It has been found that, whilst solid materials formed from xanthan alone or galactomannan alone are soluble in water, and hence unacceptable for most wound dressing applications, the use of a mixture of these two polysaccharide types results in a material having a lower, highly controllable solubility that can be optimised for each wound dressing application. Preferably, the weight ratio of xanthan to total galactomannans is in the range 10:90 to 90:10. More preferably, the ratio is in the range 25:75 to 75:25.
Galactomannans are polysaccharides containing both galactose and mannose residues. Preferably, the galactomannans are selected from the group consisting of guar gums (wherein the galactose to mannose ratio is about 1:2), locust bean gums (wherein the galactose to mannose ratio is about 1:4) and mixtures thereof. Preferably, at least 75% by weight of the solid bioabsorbable material consists of the mixture of xanthan and galactomannans. More preferably, at least 90% by weight of the material consists of the said mixture. The balance of the material comprises water (up to about 10% by weight), optionally salts such as sodium chloride, and therapeutic agents including antiseptics such as silver sulfadiazine or chlorhexidine, antibiotics such as penicillin tetracyclin or streptomycin, steroids and the like. Particularly preferred therapeutic agents in the wound dressing materials are those that actively promote wound healing such as glycosaminglycans (e.g. hyaluronic acid, heparan sulfate or chondroitin sulfate) and in particular cell growth factors, such as fibroblast growth factor and platelet derived growth factor. The therapeutic agents are preferably present in an amount up to 10% by weight, more preferably 0.01-2% by weight of the material.
The materials according to the present invention may be in any solid form, such as solid films or pellets. However, preferably, the materials are in the form of a sponge.
The sponge material according to the present invention may be provided in any shape, but is preferably provided as a wound dressing layer having a thickness of from 1 to 5 mm. Preferably, the sponge material has a water absorbency as hereinafter defined of at least 25 g/g.
The present invention also provides a method of making a solid bioabsorbable material for use as a wound dressing, the method comprising: dispersing a mixture of xanthan and one or more galactomannans in the weight ratio xanthan: total galactomannans range from 1:99 to 99:1 in a solvent to form a mixed dispersion, and freeze-drying the dispersion to produce the material in the form of a sponge.
Preferably, the dispersion in a solution or gel, and the solvent is an aqueous solvent, more preferably the solvent consists essentially of water. Preferably, the total weight concentration of the xanthan and the galactomannans in the dispersion is in the range of 2 to 20 mg/ml. The dispersion will typically be a transparent aqueous gel.
Specific embodiments of the present invention will now be described further, by way of example, as follows.
REFERENCES:
patent: D. 370263 (1996-05-01), Falkenberg et al.
patent: 3902559 (1975-09-01), Everingham et al.
patent: 4341207 (1982-07-01), Steer et al.
patent: 4394930 (1983-07-01), Korpman
patent: 4415388 (1983-11-01), Korpman
patent: 4524064 (1985-06-01), Nambu
patent: 4624868 (1986-11-01), Muller
patent: 4675009 (1987-06-01), Hymes et al.
patent: 4692273 (1987-09-01), Lawrence
patent: 4994277 (1991-02-01), Higham et al.
patent: 5009890 (1991-04-01), DiPippo
patent: 5059189 (1991-10-01), Cilento et al.
patent: 5424064 (1995-06-01), Schmidt et al.
patent: 5456745 (1995-10-01), Roreger et al.
patent: 5620706 (1997-04-01), Dumitriu et al.
patent: 5804213 (1998-09-01), Rolf
patent: 43 43 947 A1 (1995-06-01), None
patent: 0 030 435 (1981-06-01), None
patent: 0 049 944 (1982-04-01), None
patent: 0 227 553 (1987-07-01), None
patent: 0 307 187 (1989-03-01), None
patent: 0 340 945 (1989-11-01), None
Haynes Carla A.
Lorimer Elaine
Berman Alysia
Dudash Diana
Harrington James
LandOfFree
Solid polysaccharide materials for use as wound dressings does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Solid polysaccharide materials for use as wound dressings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solid polysaccharide materials for use as wound dressings will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2579195