Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Peptide containing doai
Reexamination Certificate
1997-08-14
2001-04-17
Degen, Nancy (Department: 1636)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Peptide containing doai
C514S021800, C514S802000, C514S824000, C514S844000, C530S350000
Reexamination Certificate
active
06218357
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fibroin fluid for use as a main ingredient or an additive in the fields of pharmaceuticals, cosmetics, hygiene or foods.
2. Description of the Related Art
As far as fibroin is concerned, a fibroin in a gel state is known. The fibroin in a gel state is obtained by adding an acid such as citric acid or acetic acid to silk protein to decrease its pH to an isoelectric point, or by adding sericin or other polysaccharide as a gelating agent.
A fibroin in a gel state (“fibroin gel” hereinafter) has a network structure in its entire system so that it is of one mass as a whole gel, and as a result, it cannot be brought into a “cream” state. Further, the fibroin gel is poor in water retention, and when the gel is allowed to stand, it cracks since contained water is lost.
On the other hand, when a fibroin gel is prepared by adding an additive such as citric acid or the like, it is difficult to remove the additive after the gelation, and the residual additive as an impurity in the gel has an adverse effect on the quality of an end product obtained from the fibroin gel. Moreover, the added gelating agent such as citric acid or other acids is not only present as an impurity, but it works on the crosslinked structure of fibroin to prevent the fibroin gel from exhibiting the adsorption capacity inherent to the fibroin gel.
As described above, fibroin gel has physical problems that it cannot be brought into a cream state and is poor in water retention, and it also has a production-wise problem that it contains an additive which causes a poor product quality. Therefore, although fibroin itself has a potential for its wide applications in the fields of pharmaceuticals, foods and cosmetics, these applications of the fibroin gel are impossible, and the use of fibroin is limited to very narrow fields.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems, and the object thereof is to make it possible to apply fibroin widely to the fields of pharmaceuticals, foods and cosmetics.
The present invention relates to a fibroin fluid having a fluidity sufficient for bringing it into a cream state, unlike a conventional fibroin having only a jelly-like fluidity.
The present inventor has completed the present invention by finding the following. That is, a fibroin fluid obtained by a method in which carbon dioxide is added to a fibroin aqueous solution and the carbon dioxide is completely removed by pressure reduction or heating, has fibroin microstructures which are dispersed in a dispersing medium. Differing from a conventional fibroin gel, the above fibroin fluid has a fluidity sufficient for bringing it into the physical state of a cream, has the property of excellent humidity retention over a conventional fibroin gel and has wide usefulness as an agent for decreasing cholesterol or a cosmetic.
Unlike a homogeneous product such as a fibroin aqueous solution in which fibroin is dissolved in water, the fibroin fluid of the present invention is a mixture in which solid fibroin microstructures having a size of about 100 &mgr;m are dispersed in a dispersing medium.
Each of the fibroin microstructures constituting the fibroin fluid is a porous filmy substance having a steric branching structure. The fibroin microstructures of the fibroin fluid produced by the process of the present invention have a size of about 100 &mgr;m, and the distribution of sizes of the fibroin microstructures is not very broad.
Further, the dispersing medium in which the fibroin microstructures are dispersed is typically water, while the dispersing medium may be selected from media similar to water, such as lower alcohols. However, an organic solvent which may alter the fibroin itself cannot be used.
In the fibroin fluid of the present invention, fibroin microstructures which are of porous filmy substances having a steric branching structure present in a dispersed state. The fibroin fluid which is a mixture of units of the above fibroin microstructures, provided by the present invention, has a greater fluidity, and has excellent water retention as compared to a conventional fibroin gel.
The fibroin fluid of the present invention does not contain any of citric acid, polysaccharides or other gelating agent which inevitably remains in a conventional fibroin gel. The fibroin fluid of the present invention is therefore free of any adverse effects which these impurities have, and it can be used in the fields of pharmaceuticals, cosmetics, foods and other industrial products.
The fibroin fluid of the present invention can be easily and inexpensively produced by a method in which carbon dioxide is added to a fibroin solution to form a fluid and then the carbon dioxide is completely removed from the fluid by pressure reduction or heating. According to the process for the production of a fibroin fluid, provided by the present invention, the carbon dioxide added for forming a fibroin fluid can be completely removed in a short period of time by heat treatment or pressure-reduction treatment.
More specifically, first, carbon dioxide is mixed with a fibroin solution to adjust the pH of the solution close to a fibroin isoelectric point, whereby a fibroin fluid formed of units of fibroin microstructures is obtained. Then, the added carbon dioxide is removed from the system (fibroin fluid) by pressure reduction or heating. In this case, the carbon dioxide is completely removed from the system in a short period of time regardless of the structure of the fibroin microstructures. According to the above production process, therefore, a pure fibroin fluid can be easily obtained.
The fibroin aqueous solution can be obtained by a well known method. In the present invention, the fibroin aqueous solution is prepared by dissolving fibroin in a calcium chloride aqueous solution and then removing the calcium chloride from the aqueous solution by dialysis, the fibroin aqueous solution may be prepared by a method in which fibroin is dissolved in a copper-ethylenediamine complex salt solution, the resultant solution is neutralized with acetic acid and dialyzing the neutralized solution with flowing water, or by a method in which fibroin is dissolved in a lithium bromide aqueous solution or a calcium nitrate aqueous solution and then removing the lithium bromide or calcium nitrate by dialysis.
Further, the fibroin for preparing the fibroin aqueous solution is obtained by removing sericin from silkworm pod or silk yarn. The sericin can be removed from silkworm pod or silk yarn by a known method, for example, in which the silkworm pod or silk yarn is treated with hot water or a diluted alkali. For completely removing the sericin, it is preferred to use an alkali.
When carbon dioxide is dissolved in the fibroin aqueous solution, not much change takes place at the time the solution is formed. However, when the solution is allowed to stand for a while, the solution changes to a suspension to form a fibroin fluid. In general, the standing period of time is approximately 10 days to 2 weeks, while it is sometimes outside the above period. When the fibroin aqueous solution has a high concentration, the fibroin aqueous solution is brought into the state of a white cream. When it has a low concentration, a supernatant is formed in an upper portion. When a supernatant is formed since the fibroin aqueous solution has a low concentration, a precipitate portion itself is a fibroin fluid. When the precipitate portion is recovered by filtration, the obtained fibroin fluid has a water content of about 98% and can be directly used as a material for forming a product.
In the fibroin fluid obtained by the above production process, filmy fibroin microstructures having a size of about 100 &mgr;m and having steric branching structures are uniformly dispersed without crosslinking one another.
Each of the fibroin microstructures which are uniformly dispersed contains a large amount of water. The amount of water contained in the fibroin microstructures is adjusted, where
Degen Nancy
Terauchi Seiji
Wenderoth , Lind & Ponack, L.L.P.
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