Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Wearing apparel – fabric – or cloth
Reexamination Certificate
2000-06-05
2002-10-08
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Wearing apparel, fabric, or cloth
C424S443000, C424S449000, C514S002600, C514S021800
Reexamination Certificate
active
06461628
ABSTRACT:
II. FIELD OF THE INVENTION
The present invention is related generally to a keratin composition and method for making same. More specifically, the present invention relates to an absorbent keratin powder or fiber. In particular, the present invention includes a hydratable keratin solid which forms a hydrogel upon addition of water for use in various applications including nonwoven films, diapers, skin treatments, prosthetic devices, excipients, tissue-engineering scaffolds and the like.
III. BACKGROUND OF THE INVENTION
Absorbent materials are currently used to absorb body fluids such as urine, menses, and wound exudate. The absorbent materials are placed near the skin to serve this purpose. One class of products includes diapers, where the absorbent material can be derived from wood pulp, cellulosic fibers, or super absorbent, synthetically produced material. Diapers commonly have an inner core designed to absorb urine and water. The core is typically formed from a superabsorbent polymer dispersed in a larger amount of less absorbent material. The absorbent materials typically contained in the core are separated from the skin by at least one layer of material. The absorbent materials absorb urine and can become saturated. It is believed that some material from the absorbent core leaches from the wet absorbent and travels back to the skin. In the case of chemically treated absorbent materials and films, depending on the chemicals, the leachate may be irritating and is not believed to be beneficial. Skin contact with urine can also occur and result in irritation. This type of irritation may exacerbate diaper rash problems.
Other products which contain absorbent materials for use next to the skin include feminine hygiene products such as tampons and pads. These products serve to absorb menses. Another class of products using absorbent materials includes wound dressings, both those designed for humans, and dressings for veterinary use for application to wounds or skin irritations or disorders in animals. For specific applications, wound dressings preferably absorb exudate from wounds while keeping the wounds relatively moist to promote healing. In some applications, a gel may be desirable as a wound dressing, where the gel can maintain a moist wound environment, while absorbing excess exudate.
What would be desirable is an absorbent material formed from a natural product. What would be beneficial is a non-toxic product derived from natural sources that would cause no concern when leachate from the material contacts the body or the material itself contacts the body. What would be advantageous is a material that can absorb urine and, when wet, leach out a natural product that is beneficial with respect to diaper rash. What would be desirable is a material that can return a skin healing leachate to the skin. What would be desirable is a material that aids wound healing. What would be desirable is a hydrogel made of natural products formable by adding water to a powder or fiber.
Tissue engineering is a rapidly growing field encompassing a number of technologies aimed at replacing or restoring tissue and organ function. The success of tissue-engineered implants rest on the invention of biocompatible materials that can act as cell-scaffolds and support cell growth. Of benefit are tissue-engineering scaffolds materials that are mitogenic or contain mitogenic factors. Such scaffolding materials can be used for in a wide array of tissue engineering implants containing cellular components, such as, for example, osteoblasts, chondrocytes, keratinocytes, and hepatocytes, to restore or replace bone cartilage, skin and liver tissue respectively.
IV. SUMMARY OF THE INVENTION
The present disclosure addresses at least some of the deficiencies in the art by providing a hydratable, hydrogel-forming solid derived from a keratinous source such as hair, fur, human hair and the like. In the context of the present invention, the term “hydratable keratin” and “hydratable keratin material” is a keratin or keratin material that when hydrated can form a hydrogel. In certain embodiments, a hydrogel-forming solid as disclosed herein may absorb up to 5 to 20 times its weight in water to form a hydrogel. Such a solid, as well as the hydrogel formed from the solid will be useful in various applications such as use as an absorbent with skin healing properties when incorporated into diapers, feminine hygiene products, wound dressings, including both human and veterinary uses, as a soft tissue augmentation medium when used in subdermal implants, tissue-engineering cell scaffolds, as a moisture containing agent in cosmetics, oils, lotions, or gels for use on the skin, in applications related to the healing of damaged skin, and as a pharmaceutical excipient for sustained release pharmaceutical applications.
A hydratable keratin solid may be made by methods that include providing a keratinous material, or keratin, having disulfide linkages and partially or substantially oxidizing the keratinous material with an oxidizing agent, for example, such that some disulfide linkages are cleaved and oxidized, forming hydrophilic sulfonic acid or cysteic acid residues. A preferred source of keratinous material is human hair, although the keratin may be obtained from hair or fur of animals including any mammal, or from finger or toenail material or from hooves, feet, beaks, skin, feather or horns. Human hair is a preferred source of keratin because of its ready availability from cuttings of barber and beauty shops, because it is expected to be less prone to cause undesirable immune or allergic reactions in a human, and because a keratin preparation may be made from the hair of a subject for whom the preparation will be used. This last advantage can be especially important in embodiments involving subdermal and tissue engineering implantations.
It is well known in the art that keratins contain substantial sulfur, that is, the amino acid sequence of keratin contains a high proportion of cysteine residues as compared to proteins in general. These cysteines each include a sulfhydryl moiety that is able to bond with another sulfhydryl moiety from another cysteine residue to form a disulfide bond. The second cysteine may reside within the same keratin molecule, or in another keratin molecule. These disulfide bonds are responsible for much of the tertiary and/or quaternary structure of this class of proteins. A suitable oxidizing agent is able to break this disulfide bond and to oxidize one or both of the sulfhydryl moieties so that they are no longer able to form a disulfide. Such an oxidation is a part of the process of forming the keratin products of the present disclosure. Preferred oxidizing agents include, but are not limited to peracetic acid, hydrogen peroxide, perborates, percarbonates, benzoyl peroxide, or ammonium sulfate peroxide. However, any suitable oxidizing agent known in the art can be used in the practice of the invention. After oxidation, the liquid oxidizing agent can be filtered from the oxidized keratin solid, and the solid may be washed to remove residual oxidizing agent, for example.
The resulting solid may then be suspended in a non-aqueous solvent and the pH may be adjusted upward with base—conveniently to at least neutral pH. Preferred solvents for this second solution do not include more than about 20 volume percent water, as the water may hydrolyze the peptide backbone during processing. Preferred solvents would include alcohols such as methanol, ethanol, or propanol, for example, and would also include non-aqueous polar, water-miscible solvents such as acetone and tetrahydrofuran, for example. An effective solvent should be able to solvate a Lewis base and should also be able to provide a medium able to keep the keratin sufficiently swelled to allow ionic associations or interactions between the base cations and anionic sulfonic acid groups in the keratin. Small amounts of water will assist in this regard, so blends of the aforementioned solvents in combination with water up to 20 volume percent may be used
Blanchard Cheryl R.
Siller-Jackson Arlene J.
Smith Robert A.
Timmons Scott F.
Van Dyke Mark E.
Corder Timothy S.
Ghali Isis A.D.
Keraplast Technologies Ltd.
Vinson & Elkins L.L.P.
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