CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority from U.S. Provisional Application

No. 61/665,972, filed June 29, 2012.

FIELD OF THE INVENTION

This invention is related to microneedle arrays having microneedles comprising cosmetic ingredients for insertion into human skin.

BACKGROUND OF THE INVENTION

It is well known that in order to provide decorating and/or functional effect cosmetic formulations such as solutions, ointments, creams, tapes, patches are commonly administered. The formulations are applied to skin, and they are often lost or removed due to perspiration, washing, or external forces. Such conditions prevent permeation of cosmetic actives into skin to obtain optimal efficacy. But, in addition to factors impacting the skin's surface, cosmetic actives are further prevented from delivering optimal efficacy due to the natural barrier properties of skin.

Recently, microneedles fabricated of metal or plastic, coated with pharmaceutical agents or cosmetic agents on their surface, have been used as an approach to deliver pharmaceutical agents to a desired site of skin. However, with this approach, a small quantity of pharmaceutical agents or cosmetic agents can be administrated, and there is a risk that solid microneedle fragments will remain in skin. Therefore, their use raises many safety concerns.

One approach to serve this need involves the design of microneedle arrays having water-soluble microneedles. For example, polysaccharides and starches have been formed into water-soluble microneedles. However, it is difficult to fabricate polysaccharide and starch-based needles with suitable mechanical strength to penetrate the skin then dissolve. Moreover, maltose has a disadvantage of poor practicability due to its high hydroscopicity.

Based on the foregoing, it is clear that there is a need for a microneedle array which is capable of delivering cosmetic ingredients into the skin without safety risks associated with metal or plastic microneedles. SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a microneedle array which can be easily inserted into skin, leave contained cosmetic agents under the surface of skin by dissolution, swell or break off of needles, and dissolve or disappear into skin. It is another object of the present invention to provide a microneedle array for the administration of soluble cosmetic agents to skin.

The present invention provides a microneedle array which comprises a substrate and cone-shaped or pyramid-shaped microneedles for skin insertion fixed on the substrate. The microneedles are readily dissolved after puncturing the outer surface of human skin.

BRIEF DESCRIPTION OF THE DRAWING

The lone figure is a schematic view of the microneedle array.

DETAILED DESCRIPTION OF THE INVENTION

The microneedle array of the present invention comprises a substrate and cone-shaped or pyramid-shaped microneedles for skin insertion on the substrate. The microneedles are comprised of one or more water soluble materials. For example, U.S. Patent Publication 2010/0228203 to Quan et al. discloses chitosan, collagen and gelatin, as a material which can dissolve or swell in the body. Other suitable materials include polysaccharides such as maltose, alginate and agarose, cellulose such as carboxymethylcellulose and hydroxypropylcellulose, starch. Particularly preferred, is an embodiment containing over 50 weight percent of hyaluronic acid.

Hyaluronic acid used in the present invention is a kind of glycosaminoglycan. Hyaluronic acid is composed of the repeating disaccharide unit of N-acetylglucosamine and glucuronic acid. Glycosaminoglycan is also called mucopolysaccharide. It is preferable to use the hyaluronic acid that obtained from organism such as crista galli and umbilical cord and that obtained with the with cultivation of lactic acid bacteria, streptococcus.

The microneedle product from hyaluronic acid becomes harder as the weight average molecular weight of hyaluronic acid is smaller. And its mechanical strength increases with the weight average molecular weight of hyaluronic acid. Thus, when the weight average molecular weight of hyaluronic acid as raw material is smaller, the microneedles for skin insertion become harder and it is easy to insert them into skin, while their mechanical strength decrease and the needles are easily broken during storage and insertion. Therefore, it is preferable to use the hyaluronic acid with the weight average molecular weight larger than 400,000. The weight average molecular weight is determined by the method of gel permeation chromatography.

In one form of the invention, the microneedles contain over 50 weight percent of hyaluronic acid and they are can be dissolve or swell in the body. The microneedles may contain over 50 weight percent of mentioned biomaterials, other biomaterials of less than 50 weight percent which can dissolve or swell in the body can be used. Hyaluronic acid is known to cause bulging skin. Accordingly, it is preferred to only use hyaluronic acid to fabricate the microneedles for skin insertion.

In addition to hyaluronic acid, other suitable polysaccharides include those such as maltose, alginate and agarose, cellulose derivatives such as carboxymethylcellulose and hydroxypropylcellulose, starch.

In one form of the invention, the microneedles are characterized by containing 50 to 70 weight percent of collagen and 50 to 30 weight percent of hyaluronic acid.

The microneedles for skin insertion which contain 50 to 70 weight percent of collagen and 50 to 30 weight percent of hyaluronic acid, which are dissolvable and swellable in the body, have suitable mechanical strength and are easy to be inserted into skin and have good solubility in the skin. Thus, it is preferred that the microneedles are composed of biomaterials of 50 to 70 weight percent of collagen and 50 to 30 weight percent of hyaluronic acid which can dissolve or swell in the body.

The figure is a general view of the microneedle array 10. As shown in the figure, a plurality of microneedles 1 for skin insertion are attached or integrally formed to the substrate 2.

The microneedles 1 for are necessary to be penetrated into skin. Moreover, the tops of the microneedles 1 inserted into skin are essential to remain in skin with dissolution, swelling and breaking off in the skin. Thus, the microneedles 1 become gradually finer from the base to the top and are preferred to have sharp tops. In detail, the shape of the microneedles 1 is preferred to be circular cone or polygonal pyramid such as triangulate pyramid, quadrangular pyramid, hexagonal pyramid and octagonal pyramid.

The diameter or the length of one side to another at the base of the microneedles 1 for skin insertion is preferred to be 100 to 300 um. The height of the microneedles 1 for skin insertion is preferred to be 100 to 1200 um. The space between microneedles 1 is not specially defined and is preferred generally to be 100 to 1000 μιη. A variety of cosmetic ingredients may be delivered as components of the dissolvable microneedle array herein. For example, whitening ingredients, antiwrinkle ingredients, blood circulation promotion ingredients, dietary aid, antibacterial agents; vitamins may be included in the microneedle compositions.

As whitening ingredients, for example, are vitamin C and derivatives such as ascorbyl glucoside, ascorbyl palmitate, licorice extract, yeast extracts, trametes, aspergillus, exophilia, resveratrol and derivatives such as resveratrol phosphate, resveratrol ferulate, and oxyresveratrol, ferulic acid and its derivatives, kojic acid, ellagic acid, hinokitiol, soybean extracts, Scutellaria extract, mulberry extract, molasses, tetrahydrocurcumins, glycyrrhetinic acid, pomegranate, grape seed extract, viapure hops, BV-OSC - tetrahexyldecylascorbate, ascorbic acid disodium phosphate, ascorbic acid glucoside, a(P)-arbutin, ascorbyl palmitate, resorcinol, and tranexamic acid.

As antiwrinkle ingredients, for example, are retinol, tretinoin, retinol acetate, vitamin A palmitate. As blood circulation promotion ingredients, for example, are tocopheryl acetate, capsacin. As dietary aids, for example, are centella asiatica, chlorella extract, boswellia extract, whey protein, ursolic acid, white birch, biopeptide EL -palmitoyloligopeptide, pycnogenol, zincidone, siegesbeckia, silymarin, argireline, dill extract, NAB fennel seed extract, anogeissus bark extract, viapure menyanthes, tetrahexyldecylascorbate, aminopropylascorbylphosphate, yeast ferments, phytomatrix, N-acetyl glucosamine, urea, resveratrol and derivatives its derivatives, raspberry ketone, evening primrose, and seaweed extract.

As antibacterial agents, for example, are isopropylmethylphenol, photosensitizers, zinc oxide. As vitamins, for example, are vitamin D2, vitamin D3, vitamin K. Other suitable cosmetic ingredients include roxisome, photosome, ultrasomes growth factors, RNA, DNA fragments, genes hyaluronic acid and salicylic acid.

In one embodiment, the microneedles comprise at least one water-insoluble benefit agent. Such agents may be selected from, for example, lipids, oils, waxes, proteins, hydrophobically surface-modified pigments and inorganic compounds, and mixtures thereof. The water-insoluble benefit agents may be delivered superficially, so as to only slightly penetrate the skin. This may be achieved by reducing the length of the microneedles according to the desired effect. It is believed that this technique would enhance efficacy of, for example, moisturizing agents, in skin. Although either of the mentioned cosmetic agents has the molecular weight of less than 600, the one has high molecular weight also can be used. As preferable cosmetic agents that have high molecular weight, for example, are bioactive peptide and its derivative, nucleinic acid, oligonucleotide, various kinds of antigens, bacteria, virus fragment.

As a bioactive peptide and its derivative, for example, are calcitonin, adrenocorticotropic hormone, parathormone (PTH), hPTH (1→34), EGF, insulin, secretin, oxytocin, angiotensin, β-endorphin, glucagon, vasopressin, somatostatin, gastrin, luteinizing hormone-releasing hormone, enkephalin, neurotensin, atrial natriuretic peptide, somatotropin, somatotropin-releasing hormone, bradykinin, substance P, dynorphin, thyroid stimulating hormone, mammotrophic hormone, interferon, interleukin, G-CSF, glutathione peroxidase, superoxide dismutase, desmopressin, somatomedin, endothelin, placenta extract and salts of them. As antigens, for example, are HBs surface antigen, HBe antigen, tetanus toxoid, diphtheria toxoid, amyloidPprotein.

As mentioned above, in the microneedle array 10, a plurality of microneedles 1 inserted into skin are fixed on the substrate 2. The substrate 2, which the microneedles 1 inserted into skin can be formed on, is not specially defined to have affinity of attachment with the microneedles 1 inserted into skin. The substrate 2 can be a film or sheet made of materials such urethane resin, polyvinyl alcohol and aluminum. The thickness of the substrate 2 can be, for example, 100 to 1000 μιη. In addition, the substrate 2 can be fabricated of materials that can dissolve or swell in the body like the microneedles 1 inserted into skin.

The method of manufacturing of the microneedle array 10 is not specially limited. The microneedle array 10 can be fabricated by any well-known method, such as the following method (1) to (4).

In the method (1), the solution which contains over 50 weight percent of biomaterials chosen from chitosan, collagen, gelatin, hyaluronic acid as solute that can dissolve or swell in the body, and if necessary, the cosmetic agents are put on the mold in which the holes corresponding to the microneedle shapes 1 have been patterned. Then dry the solution at room temperature or by heating to evaporate water. After laminating the substrate 2 to the needles, the microneedles 1 for skin insertion and substrate 2 are obtained by peeling them off from the mold.

In the method (2), the solution described above is put on the mold mentioned above to form a substrate layer on the mold and microneedles in the mold. After evaporating the water of the solution at room temperature or by heating, the microneedle array is obtained by peeling the substrate off from the mold.

According to the method (2), can be obtained the microneedle array 10, of which the substrate 2 and the microneedles 1 for skin insertion are both fabricated. The above microneedles contain over 50 weight percent of biomaterials chosen from chitosan, collagen, gelatin, hyaluronic acid which can dissolve or swell in the body, and can contain cosmetic agents.

In the method (3), the solution which contains over 50 weight percent of biomaterials chosen from chitosan, collagen, gelatin, hyaluronic acid, materials that can dissolve or swell in the body, and cosmetic agents; is injected as the microneedles 1 for skin insertion onto the substrate 2. And then the microneedle array is obtained by drying the solution at room temperature or by heating.

In the mentioned methods of manufacturing, as a material of the microneedles 1, the needles can be composed of over 50 weight percent of the biomaterials chosen from chitosan, collagen, gelatin, and other materials those can dissolve or swell in the body. It is preferred to use collagen from biological origin with 50 to 70 weight percent and hyaluronic acid from biological origin with 50 to 30 weight percent and other biomaterials dissolve or swell in the body.

The composition of the microneedle array 10 is as mentioned above. The microneedles 1 for skin insertion of the microneedle array 10 have suitable mechanical strength, toughness and hardness, and can be easily inserted into skin without breaking followed by dissolving and disappearing in the skin.

Therefore, it is possible to actually deliver the biomaterials chosen from chitosan, collagen, gelatin or hyaluronic acid to the desired part of skin. It is also possible to deliver cosmetic agents to the desired part of skin by adding them in the microneedles 1 for skin insertion. In addition, the microneedles 1 for skin insertion are able to contain a great quantity of cosmetic agents if the cosmetic agents are water soluble. Moreover, it is not necessary to fabricate the microneedle array by heating when soluble biomaterials are used as the material of the microneedles for skin insertion. In this way, the decrease in the effect of cosmetic agents and cosmetic agents due to heat decomposition can be avoided.