478 JOURNAL OF COSMETIC SCIENCE NOVEL SILICONE VESICLES FOR DELIVERY OF ACTIVES IN PERSONAL (ARE Shaow B. Lin1, Ph.D., Stephanie Postiaux2 and Joanna Newton2, Ph.D. 1 Delivery Technology, Science Ei Technology, Specialty Chemicals Business, Dow Corning Corp., Midland, MI 'Application Development, Life Science Innovation Team, Dow Corning Europe, Seneffe, Belgium Introduction: Stabilization and efficacy enhancement of lipophilic actives in aqueous cosmetic products are important formulation needs in the personal care industry. Traditional encapsulating technologies convert the actives into capsules or particles of micron-sizes or larger, providing mainly the stabilization function with little efficacy benefit. There is a growing interest for a nano- to submicron-sized delivery system that provides both benefits. In response to these unmet needs, we successfully developed a novel method for preparing "assembly-required" silicone vesicles from hydrophobic silicone polyethers. Vesicles were made and shown stable from hydrophobic PEG-12 dimethicones (rake-type silicone polyethers) using this patent-pending process [1,2]. The relation between PEG-12 dimethicone architecture and vesicle-forming capability was also shown. These vesicles are fundamentally different from the self-assembly vesicles from hydrophilic PEG-12 dimethicones known in prior art [3,4]. This paper presents a new assembly-required silicone vesicle derived from an (AB) n silicone polyether block copolymer. The utility of this polymeric silicone vesicle as a topical delivery system for lipophilic personal care ingredients is discussed. Materials and Methods: Dimethicone PEG-12 copolymers (INCi name to be proposed) are (AB) n alternating block copolymers of PEG-12 polyether blocks (represented by A, where 12 is the average number of oxyethylene units in PEG block) and dimethicone blocks (represented by B), with n representing the number of AB repeats in the copol ym er. Dimethicone PEG-12 copolymers with various dimethicone block lengths, illustrated in Figure 1, were made at Dow Corning for this study. These dimethicone PEG-12 copolymers are hydrophobic, with poor solubility in water. [-� [� [- - PEG-12 block (A) � Dimethicone block (B) Figure 1. Dimethicone PEG-12 copol ym ers with different dimethicone block lengths. Cryogenic transmission electron microscopy (Cryo-TEM) was used to visualize the vesicles. This is done by freeze­ drying the vesicles at cryogenic temperature, then analyzing the dried specimens at cryogenic temperature. Vesicle size and distribution were determined using a Nanotrac particle analyzer. Formulation development was carried out to determine formulation latitude and compatibility with common cosmetic ingredients. Cryo-TEM was used to verify the integrity of vesicles in formulations, and HPLC assays to quantify the amount of vitamin in vesicles. Results and Discussion: The dimethicone PEG-12 copolymers prepared in this study were hydrophobic and exhibited poor to no solubility in water. We successfully prepared submicron-size vesicles from (AB)0 dimethicone PEG-12 copolymers of selected dimethicone block length, using a Dow Corning proprietary process. Water-insoluble dimethicone PEG-12 polymeric molecules arranged themselves into bilayers and vesicles in the presence of a specific medium. These structures were then kinetically locked to achieve stability. Figure 2 illustrates how the polymeric dimethicone PEG- 12 molecules transform themselves into orderly bilayers and vesicles.

2005 ANNUAL SCIENTIFIC SEMINAR - - - - Hydrophilic actives inside fflil vesicle Lipophilic actives within bilayer Figure 2. Formation of vesicles from dimethicone PEG-12 copolymers and the proposed actives payload sites. These polymeric vesicles are useful for delivery of actives. To prove the product concept, vitamin A palmitate 479 (VAP) was incorporated into the vesicles formed by the dimethicone PEG-12 copolymer. The vitamin-loaded vesicles were subsequently formulated into model skin care products. Formulation latitude and compatibility with common cosmetic ingredients also were investigated. The Cryo-TEM images in Figure 3 show the sustainability of silicone vesicles in body lotion and moisturizing geJ, as confirmed by the characteristic honeycomb vesicle aggregates found only in this type of vesicles. (A) Figure 3. Cryo-TEM images ofbody lotion (A) and moisturizing gel (B) containing vitamin A palmitate encapsulated within silicone vesicles from dimethicone PEG-12 copolymer. Conclusions: Novel silicone vesicles with distinctive honeycomb morphology have been successfully prepared from (AB)0 dimethicone PEG-12 copolymers. Copolymers of specific dimethicone chain architecture are essential to the formation of bilayers and vesicles, as illustrated in our proposed model. A proof-of-concept study was presented to show that these polymeric silicone vesicles are suitable for delivery of actives in personal care formulations. Vesicle-encapsulated vitamin A palmitate was further incorporated into gels, body lotions and creams. The sustainability of vesicle assemblies in gels and body lotions was shown via cryo-TEM. The stability of entrapped vitamin in vesicles and in formulations at 40 °C was quantified using HPLC. References: I. Lin, S.8., Postiaux, S., Kim, G., "Development of A Novel Silicone-based Vesicle Delivery System," 23nt IFSCC (October 2004, Orlando, FL). 2. Lin, S.B., Stoller, C., Newton, J., Starch M.S. and Postiaux, S. "Silicone Delivery Systems: Opportunities for Controlled Release," in "Advanced Technology Conference 2004" Milan, Italy, April 26-27, 2004. 3. Hill, R.M., He, M., Lin. Z., Davis, H.T., and Scriven, L.E. "Lyotropic Liquid Crystal Phase Behavior of Polymeric Siloxane Surfactants," Langmuir, 9, pp.2789-2798, /993. 4. Hill, R.M., Snow, S.A., US Patents 5,364,633 (Nov. 15, 1994 to Dow Coming) and 5,411,744 (May 2, 1995 to Dow Coming) "Silicone Vesicles and Entrapment."