Microemulsions for Sprayable Delivery and Other Topics: Literature Findings

This month’s survey of recent patent and research literature describes moneymaking ideas for personal care product development, including fish DNA fragments for antiwrinkle skin care, soy peptides in cosmeceuticals, improvements in the efficacy of DHA, organo-sulfur compounds for skin lightening, and silicone foaming and detergency, among others.

Skin and Skin Care
Inhibiting melanin with thiazolamine: Shiseido Company Ltd. has disclosed thiazolamine derivatives or oxazolamine derivatives with melanin production-inhibitory activities.1 Also disclosed are skin lightening cosmetics containing the compounds; for example, 4,5-dihydro-4,4-dimethyl-N-phenyl-2-thiazolamine was prepared and tested in vitro for melanin production-inhibiting activities.

Soy peptides in cosmeceuticals: Sekine et al. have published2 on the production and skin permeation of soy derived peptides (SP). The effects of SP on type I collagen were evaluated to examine their potential for cosmeceuticals using the enzyme-linked immunosorbent assay (ELISA). A marked increase in type I collagen with SP application and a further increase with the simultaneous application of magnesium ascorbyl phosphate (VC-PMg) were shown. These effects were dependent upon the application concentration of the SP.

Also, amino acids such as glutamine and glutamic acid (GLU) entrapped in SP were found to easily permeate the skin, whereas the peptides GLU-GLU and GLU-GLU-GLU seldom permeated. However, an adjustment of the pH to that of amino acids and/or addition of l-menthol markedly increased the skin permeation of SP.

Picardin/oxybenzone interaction: Gu et al. have disclosed the in vitro permeation characterization of the repellent active picaridin and the sunscreen active oxybenzone.3 The authors performed a series of in vitro diffusion studies to evaluate the transmembrane permeation of picaridin and oxybenzone across human epidermis and a poly(dimethylsiloxane) (PDMS) membrane. The permeation of picaridin and oxybenzone across human epidermis was suppressed when both active ingredients were used concurrently. Increasing concentrations of the test compounds further reduced the permeation percentage of picaridin and oxybenzone.

While permeation characteristics were correlative between human epidermis and PDMS membrane, the permeability in the PDMS membrane was significantly larger than in human epidermis. The findings were found to be different with the concurrent use of DEET insect repellent and sunscreen oxybenzone, where a synergistic permeation enhancement was observed. Further comparative studies are therefore necessary to understand these permeation mechanisms and the interactions between picaridin and oxybenzone.

Improving DHA efficacy: Burkhart et al. published a review on the use of dihydroxyacetone (DHA) and methods to improve its performance as an artificial tanning agent.4 DHA binds to proteins in the stratum corneum to impart a non-toxic, bronze color. The resulting pigments are called melanoidins, or brown chromophores.

The color is not removed by simple washing, swimming or natural perspiration; however, it only lasts for 5–7 days, as skin cells are continuously shed. Exfoliation, tape stripping, prolonged water submersion or heavy sweating can lighten the tan, since all contribute to rapid dead skin cell peeling. Indeed, users may opt to reapply the product on a regular basis in order to maintain the skin color.

Possible improvements to DHA products include: the addition of perfluoropolyether phosphate to lower the formulation’s pH; exfoliation with polyethylene beads prior to treatment; wiping skin with an acidic toner prior to application; the addition of strong antioxidants such as caffeic acid phenethyl ester; using a polymer base; and pre-treating the skin with amino acids to increase binding sites of the DHA to skin.

Organo-sulfur compounds for skin lightening: Chu et al. investigated the effects of select organo-sulfur compounds, including: 1-propylmercaptan (PM), di-methyl disulfide (DMDS), diallyl disulfide (DADS), propyl disulfide (PDS), and 2,5-dimethylthiophene (DMT) on melanin formation.5 The inhibitory action of the organo-sulfur compounds on tyrosinase activity and melanin formation may be attributed to a reduced formation of reactive oxygen species (ROS) and the positive modulation of the glutathion/glutathione disulfide ratio in B16 cells.

Among the selected organo-sulfur compounds, only PM displayed a significant inhibitory effect on tyrosinase activity. It also showed the highest inhibitory action on o-quinone formation. Further analysis of the inhibitory kinetics revealed that PM is a mixed-type inhibitor. This is the first study indicating that organo-sulfur compounds tested may play an important role in the regulation of melanin formation, making them potent candidates for skin lightening agents.

Silencing the siRNA gene to inhibit tyrosinase: Avon Products Inc. disclosed siRNA-mediated gene silencing oligomers to inhibit tyrosinase and reduce pigmentation.6 The described invention discusses compositions and methods for treating, preventing and improving hyperpigmentation or other unwanted pigmentation such as age spots and skin discoloration. The compositions preferably are applied to the skin or delivered by directed means to the site in need.

Fish DNA fragments for anti-wrinkle skin care: Jung has disclosed the preparation of DNA fragments from fish semen or egg by enzymic hydrolysis and their use in antiwrinkle skin care.7 The fish semen or egg must first be thawed, followed by hydrolyzing the DNA with enzymes at pH 7.0–7.4 under a temperature range of 43–47 °C; then sterilizing the DNA fragments under a temperature range of 100–109°C for 10–30 min in weak acidic solution and reducing the molecular weight of the fragments at pH 4.0–4.4 under a tempurature range of 68–72°C; and finally, precipitating and performing dry granulation. This method can be used to increase the efficacy of the preparation by 7% and the DNA fragments can be used in antiwrinkle skin care.

Hair and Hair Care
Indigofera tinctoria hair loss prevention: Shiseido Co., Ltd. discloses hair nourishment preparations containing an Indigofera tinctoria extract active solution to inhibit caspase 3.8 A hair loss preventive formula containing the caspase 3 inhibitor was also disclosed.

Emulsified hair styling composition: Shiseido Co., Ltd. also published a patent on an emulsified hair composition that exhibited excellent hair styling and hair moisturizing effects with no stickiness.9 The composition contained a polyhydric alcohol, a hydrophilic nonionic surfactant, an amphoteric surfactant and/or a semipolar surfactant, a higher fatty acid, and a high molecular weight silicone. An example of a hair styling composition is shown in Formula 1.

Makeup Long wear, effect color cosmetics: Kosei Co., Ltd. has disclosed w/o emulsion makeup with special effects and that protects from easy removal.10 The makeup includes eye, highlighting and cheek color cosmetics containing lipophilic silicone surfactants with: a hydrophilic-lipophilic balance of 3–7, acrylic silicone graft copolymers, high viscosity oils, volatile silicone oils and powders. An example of an eye makeup is shown in Formula 2. The preparation imparted a transparent gloss and three-dimensional appearance to the skin, showing good application and retention on the skin for 8 hr.

Ascorbic acid UVA filter: Merck GmbH has patented a UVA filter based on ascorbic acid derivatives and the use of the derivatives in hair and skin compositions.11 The company prepared 2-(4-dihexylamino-2-hydroxybenzoyl)-benzoic acid ascorbyl ester from vitamin C and 2-(4-dihexylamino-2-hydroxybenzoyl)-benzoic acid. The derivative was formulated at 1% w/w in a UVA w/o emulsion, as shown in Formula 3.

Photostabilization of UV filters: An anonymous article reviewed the photostabilization of cosmetic UV filters before decomposition by UV irradiation.12 Target UV filters were: butyl dibenzoylmethanea; cinnamate UV filters such as ethylhexyl methoxycinnamateb, octyl methoxycinnamate and octinoxate; or filters such as diethylamino hydroxybenzoyl hexyl benzoate. Photostabilizers included diphenylcyanoacrylate derivatives such as octocrylene, polycrylene, undecylcrylene dimethicone or naphthalates such as diethylhexyl 2,6 naphthalatec. Photo-unstable UV filters can be stabilized with antioxidants such as hydroxy dimethoxybenzyl malonate and hydroxy dimethoxybenzylidenmalonate. Formulations were given for w/o emulsions, hair care products, cosmetic foams, o/w emulsions and hydrodispersions for use as lotions/sprays.

Interesting Compositions and Ingredients
Silicone foaming and detergency: Shiseido Company Ltd. and Dow Corning Toray Co., Ltd. have disclosed silicone compounds for cleansing compositions with excellent foaming properties and detergency.13 The cleansing composition contains an organosiloxane derivative salt with the structure shown in either Eq. 1 or Eq. 2, and one or more anionic surfactants from a carboxylic acid salt group with an alkyl group of 10–20 carbon atoms including sulfuric acid salts, sulfonic acid salts and phosphoric acid salts.

R1R2R3Si(CH2)2ACOOM     Eq. 1

MO2CQ(CH2)2(SiR4R5O)p SiR6R7(CH2)2QCOOM     Eq. 2

In Eq. 1, R1-3 = silyloxy groups, A = alkylene groups and M = metal or organic cations. In Eq. 2, R4-7 = hydrocarbyl groups, M = metal or organic cations and Q = alkylene groups. Adding trimethylsilyl undecylenate dropwise to 1,1,1,3,5,5,5-heptamethyltrisiloxane in the presence of a platinum catalyst produced an adduct useful for cleansing compositions.

Measuring antioxidative power: Graf et al. reviewed the antioxidative power of formulations over their lifetime and described unique actives superior to vitamins.14 The human skin is situated at the interface of the organism and its environment and is thus exposed to a variety of physical and chemical assaults. Exposure to ionizing, UV radiation or xenobiotics generates free radicals in excessive quantities that quickly overwhelm tissue antioxidants and stress-degrading pathways. There is an apparent need for providing the skin with potent antioxidants to prevent accelerated aging processes. Commonly used antioxidants vitamin C and its derivatives or vitamin E are effective but highly unstable during storage. Ideal anti-photoaging concepts should provide maximum efficacy paired with excellent stability and galenic elegance.

In the described study, cosmetic formulations containing different antioxidants were tested for their antioxidative power (AP) directly after processing and after different periods of time at different storage conditions. Vitamin-containing formulations show a dramatic decrease in AP, and some show undesirable discolorations. The company presented bis-ethylhexyl hydroxydimethoxy benzylmalonated as an antioxidant that did not show Galenic disadvantages such as yellowing of the formulation. The company also found it to remain stable without a loss in antioxidative activity and therefore recommends the antioxidant for antiaging products and sunscreens.

Microemulsions for sprayable delivery: Payne et al. disclosed the use of microemulsions as sprayable delivery systems.15 Many desired cosmetic ingredients such as organic sunscreens, vitamins, essential oils and ester emollients are not water-soluble. Commercial products that incorporate these materials are typically opaque emulsions. Microemulsion technology can therefore be utilized to create a clear to translucent water-based active delivery system without the use of ethanol or other short-chain alcohol, which can be drying to the skin. Additionally, using microemulsion technology in sprayable delivery systems allows for environmentally friendly manufacturing processes.

The emulsion blend offers a mild, vegetable-derived, pre-dispersed vehicle for actives, perfumes and emollients, leading to a significant reduction of mechanical and thermal energy and allowing for cold process formulations. This technology finds uses in market segments such as sun care, antiaging, skin care and pharmaceuticals.

Cleansing with extended fragrance: Henkel AG & Co. KGaA disclosed porous polyamide bead-containing hair and body cleaning agents with extended fragrance effect.16 The cleansers contained 0.05–40% w/w surfactant(s), 0.0001–5.0% w/w fragrance and 0.1–10.0% w/w porous polyamide beads. The beads were characterized by: a medium particle diameter of 1–30 µm, a specific surface according to a BET of 5 m2/g or larger, oil absorption capacity (boiled linseed oil) of 200 mL/100 g or larger, crystallinity (DSC measurement) of 40% or larger and a 1.0:1.5 ratio of medium particle diameter to average medium particle diameter. An example is shown in Formula 4.

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1. WO 2009 99,194, Skin whitening agents comprising thiazolamine derivatives or analogs thereof, Shiseido Company Ltd., Japan (Aug 13, 2009)
2. T Sekine et al, Skin permeation of soy derived peptides as cosmeceuticals, Daizu Tanpakushitsu Kenkyu, 11 127–131 (in Japanese) (2008)
3. X Gu et al, In vitro permeation characterization of repellent picaridin and sunscreen oxybenzone, Pharmaceutical Development and Technology, (in English) 14(3) 332–340 (2009)
4. CG Burkhart et al, Dihydroxyacetone and methods to improve its performance as artificial tanner, Open Dermatol J, 3 42–43 (2009)
5. Heuy-Ling Chu et al, Effects of selected organo-sulfur compounds on melanin formation, J Agric Food Chem 57(15) 7072–7077 (2009)
6. US 2009 202,458, siRNA-mediated gene silencing technology to inhibit tyrosinase and reduce pigmentation, Avon Products Inc., USA (Aug 13, 2009)
7. KR 2009 79,413, Preparation of DNA fragments from fish semen or egg by enzymic hydrolysis and their use for skin care, Jung, Rae Jun, S. Korea (Jul 22, 2009)
8. JP 4,321,957, Hair nourishments containing Indigofera tinctoria extracts, Shiseido Co., Ltd., Japan (Sep 11, 2009)
9. JP 2009 191,017, Emulsified hair cosmetic compositions, Shiseido Co., Ltd., Japan (Aug 27, 2009)
10. JP 2009 184,975, Water-in-oil emulsion makeups with spacial effect and comes-off protection properties, Kosei Co., Ltd., Japan (Aug 20, 2009)
11. WO 2009 97,951, UVA filter based on ascorbic acid derivatives and their use in cosmetic hair and skin compositions, Merck GmbH, Germany (Aug 13, 2009)
12. Photostabilization of cosmetic UV filters, IP.com Journal 8(9B), 17, No. IPCOM000174517D (in German) (Sep 12, 2008)
13. WO 2009 99,007, Silicone compounds for cleansing composition having both excellent foaming properties and detergency, Shiseido Company Ltd. and Dow Corning Toray Co., Ltd., Japan (Aug 13, 2009)
14. R Graf et al, Antioxidative power of formulations over life time: Unique active superior than vitamins, SÖFW 134(9) 52, 54–56, 58, 60 (2008)
15. J Payne et al, Microemulsions as sprayable delivery systems, SÖFW 134(9) 65–66, 68 (2008)
16. DE 102,008,008,754, Porous polyamide bead-containing hair and body cleaning agents with extended fragrance effect, Henkel AG & Co. KGaA, Germany (Aug 13, 2009)

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