Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Web – sheet or filament bases; compositions of bandages; or...
Reexamination Certificate
1998-04-08
2001-08-14
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Web, sheet or filament bases; compositions of bandages; or...
C424S445000
Reexamination Certificate
active
06274163
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to wound dressing materials. More specifically, the present invention is related to a keratin-based material applied directly to wounds to aid in the wound healing process.
BACKGROUND OF THE INVENTION
Chronic wounds can be caused by a variety of events, including surgery, prolonged bedrest and traumatic injuries. Partial thickness wounds can include second degree burns, abrasions, and skin graft donor sites. Healing of these wounds can be problematic, especially in cases of diabetes mellitus or chronic immune disorders. Full thickness wounds have no skin remaining, and can be the result of trauma, diabetes (e.g., leg ulcers) and venous stasis disease, which can cause full thickness ulcers of the lower extremities. Full thickness wounds tend to heal very slowly. Proper wound care technique including the use of wound dressings is extremely important to successful chronic wound management. Chronic wounds affect an estimated four million people a year, resulting in health care costs in the billions of dollars. “Treatment of Skin Ulcers with Cultivated Epidermal Allografts,” T. Phillips, O. Kehinde, and H. Green,
J. Am. Acad. Dermatol.,
V. 21, pp. 191-199 (1989).
The wound healing process involves a complex series of biological interactions at the cellular level which can be grouped into three phases: homeostasis and inflammation; granulation tissue formation and reepithelization; and remodeling. “Cutaneous Tissue Repair: Basic Biological Considerations,” R. A. F. Clark,
J. Am. Acad. Dermatol.,
Vol. 13, pp. 701-725 (1985). Keratinocytes (epidermal cells that manufacture and contain keratin) migrate from wound edges to cover the wound. Growth factors such as transforming growth factor-&bgr; (TGF-&bgr;) play a critical role in stimulating the migration process. The migration occurs optimally under the cover of a moist layer. Keratins have also been found to be necessary for reepithelization. Specifically, keratin types K5 and K14 have been found in the lower, generating, epidermal cells, and types K1 and K10 have been found in the upper, differentiated cells. Wound Healing: Biochemical and Clinical Aspects, I. K. Cohen, R. F. Diegleman, and W. J. Lindblad, eds., W. W. Saunders Company, 1992. Keratin types K6 and K10 are believed to be present in healing wounds, but not in normal skin. Keratins are major structural proteins of all epithelial cell types and appear to play a major role in wound healing.
An optimum wound dressing would protect the injured tissue, maintain a moist environment, be water permeable, maintain microbial control, deliver healing agents to the wound site, be easy to apply, not require frequent changes and be non-toxic and non-antigenic. Although not ideal for chronic wounds, several wound dressings are currently on the market, including occlusive dressings, non-adherent dressings, absorbent dressings, and dressings in the form of sheets, foams, powders and gels. Wound Management and Dressing, S.Thomas, The Pharmaceutical Press, London, 1990.
Attempts have been made to provide improved dressings that would assist in the wound healing process using biological materials such as growth factors. To date, these biologicals have proven very costly and, due to the lack of an appropriate delivery vehicle, have shown minimal clinical relevance in accelerating the chronic wound healing process. In cases of severe fall thickness wounds, autografts (skin grafts from the patient's body) are often used. Although the graft is non-antigenic, it must be harvested from a donor site on the patient's body, creating an additional wound. In addition, availability of autologous tissue may not be adequate. Allografts (skin grafts from donors other than the patient) are also used when donor sites are not an option. Allografts essentially provide a “wound dressing” that provides a moist, water permeable layer, but is rejected by the patient, usually within two weeks, and does not become part of the new epidermis.
What would be desirable, and has not heretofore been provided, is a wound dressing that protects the injured tissue, maintains a moist environment, is water permeable, maintains microbial control, is easy to apply, does not require frequent changes and is non-toxic and non-antigenic, and most important, delivers effective healing agents to the wound site.
SUMMARY OF THE INVENTION
The present invention includes a wound healing dressing containing the protein keratin. Keratin can be obtained from a number of sources including human or animal hair, and finger or toe nails, with the preferred source being hair from the patient or a compatible donor. A further preferred source is, in general, human hair. This avoids any deleterious effects related to allergies to animal tissue. Non-soluble keratin, as a wound healing agent, can be applied as a wound dressing to a wound in the form of a sheet or a powder. The term “non-soluble keratin” is used herein to describe a form of keratin that is nominally insoluble in a neutral aqueous environment. Experimentally, a low molecular weight fraction of keratin ranging from 45-200 kilodaltons does go into solution from aqueous suspensions containing the non-soluble keratin. Non-soluble keratin powder is obtained from hair using mechanical techniques. Hair can be processed mechanically by cleaning the hair with shampoo, suspending the hair in a liquid carrier, homogenizing the hair into keratin particles, removing the liquid carrier from the keratin, and sterilizing the resulting powder. See U.S. Pat. No. 5,358,935. A soluble form of keratin powder (the term “soluble keratin” as used herein describes a form of keratin that is nominally soluble in an aqueous environment) can be processed chemically by incubating the hair in a hair matrix dissolving solvent, separating the soluble and insoluble keratins, removing the solvent from the soluble keratins thereby creating a soluble keratin powder, and sterilizing the keratin powder. See U.S. patent application Ser. No. 08/979,456, entitled “Keratin-Based Hydrogel for Biomedical Applications and Method of Production”. This soluble keratin can then be used as a binder in a sheet wound dressing.
The non-soluble keratin powder can be further processed into a sheet wound dressing. To create a sheet dressing, a polymeric binder material is dissolved in a solvent such as acetone or ethanol. Non-soluble keratin powder can then be added to the solvent/polymer solution. The polymer/keratin suspension can be poured into molds, and the solvent flashed off, forming a sheet. The polymer/keratin suspension can also be cast into a sheet and the solvent flashed off. In addition, the sheet can be pressed with an applied nominal load of 200 lb., but could range from 10 lb. to 300 lb., for a time period ranging from 3 minutes to 3 hours at a temperature of 200° F., but could range from 100° F. to 300° F., to provide a coherent, flat sheet. The resulting sheet can be cut and shaped as needed before being applied to the wound. In addition, the soluble form of keratin can be used as the binder material, resulting in a wound healing sheet that is nominally all keratin, with the soluble component of the keratin able to easily resorb into the wound site.
Keratin can be applied directly to the wound in powder or sheet form. The keratin can also be incorporated into carriers including lotions, creams and gels. Applicants believe the applied keratin is supplying keratin to the wound site thereby accelerating the wound healing process. Keratin powder or sheets are easy to apply directly to a wound and provide a non-toxic, non-antigenic wound dressing that maintains wound moisture and protects the wound area, yet does not have to be replaced. Where keratin is obtained from the hair of the patient or a compatible donor, the keratin is particularly non-antigenic.
REFERENCES:
patent: 2993794 (1961-07-01), Moshy
patent: 4135942 (1979-01-01), Kikkawa
patent: 4141888 (1979-02-01), Matsuda et al.
patent: 4570629 (1986-02-01), Widra
patent: 4711780 (1987-12-01), Fahim
pate
Blanchard Cheryl R.
Siller-Jackson Arlene J.
Smith Robert A.
Corder Timothy S.
Howard S.
Keraplast Technologies Ltd.
Moloney Stephen J.
Page Thurman K.
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