154 JOURNAL OF COSMETIC SCIENCE its water activity is very low. These features allow the film to limit bacterial growth and to be preservative-free. As shown by SEM, after dissolution on its site of action, the film forms a continuous layer on the skin for at least one hour. Even after six hours, large film pieces are still visible, indicating that the film may serve as a sustained-release dosage form of cosmetic active ingredients. Adenosine is a rather hydrophilic molecule (clog P = -2.1) which could easily be in­ corporated into the film formulation at a level of 1 % . Precise and localized application of the film on the wrinkle area enables a significant level of adenosine, i.e., approxi­ mately 5 µg/cm2 to be delivered in the area to be treated. FOITS measurements in the periorbital region of women having received both adeno­ sine-containing formulations (cream or film) indicated that a significant anti-wrinkle effect was achieved over the placebo cream. The effect of a cream containing 0.1 % of adenosine was previously reported (8). The present data demonstrate that a very simple adenosine-containing product, i.e., the dissolvable film, can also significantly reduce wrinkles. Such a result supports the hypothesis that adenosine can act as an anti-wrinkle agent, as previously suggested (9). Some authors previously reported the use of self-adhesive films to deliver drugs topically (10). Similarly, S. Nicoli et al. (11) developed a bioadhesive film to enhance the trans­ dermal penetration of caffeine. Although not designed to adhere on the skin, the film we developed is slightly tacky when exposed to low moisture, which may contribute to enhancing the delivery of adenosine onto the skin. A direct physical effect of the film cannot also be ruled out. Indeed, SEM showed that once dissolved with water the film lies in the wrinkle depth for a period of a few hours. A slight tensile effect of the polysaccharide-type polymers that serve as the basic film composition, as well as the presence of glycerin, may also contribute to the overall anti-wrinkle efficacy of the dissolvable film. CONCLUSION The dissolvable films may represent a novel generation of solid, preservative-free cos­ metic delivery systems that open up a new avenue for the development of active cosmetic products. REFERENCES (1) S. Guilbert, N. Gontard, and B. Cug, Technology and applications of edible protective films, Packaging Technol. Sci., 8, 339-346 (1995). (2) F. F. Shih, Edible films from rice protein concentrate and pullulan, Cereal Chem., 73, 406-409 (1996). (3) I. Greener-Donhowe and 0. Fennema, "Edible films and Coatings: Characteristics, Formation, Defi­ nition, and Testing Methods," in Edible Coatings and Films to Improve Food Quality, J. M. Krochta, E. A. Baldwin, and M. Nisperos-Carriedo, Eds. (Technomic Publishing, Lancaster, PA, 1994), pp. 1-24. (4) M. Rohr and K. Schrader, Fast optical in vivo topometry of human skin (FOITS), SOFW ]., 124, 26-34 (1998). (5) M. Rohr, M. Brandt, and K. Schrader, Skin surface claim supported by FOITS, SOFW ]., 126, 2-11 (2000). (6) E. Ayranci, Moisture sorption of cellulose based edible films, Nahrung, 40, 274-276 (1996).

DISSOLVABLE ANTI-WRINKLE FILM 155 (7) H.J. Park, C. L. Weller, P. J. Vergano, and R. F. Testin, Permeability and mechanical properties of cellulose-based edible films,]. Food Sci., 58, 1361-1364 (1993). (8) M. L. Abella, Evaluation of the anti-wrinkle efficacy of adenosine-containing products using the FOITS technique, Int. J. Cosmet. Sci., 28, 447-451 (2006). (9) R. Bora, E. Kiheung, S. Yongin, and D. Kyunggi, Adenin, a new anti-wrinkle agent, IFSCC Conference, Seoul, Korea, 2003, abstract book poster 29. (10) S. Lieb, R. M. Szeimies, and G. Lee, Self-adhesive thin films for topical delivery of aminolevulinic acid, Eur. J. Pharm. Biopharm., 53, 99-106 (2002). (11) S. Nicoli, V. Amoretti, P. Colombo, and P. Santi, Bioadhesive transdermal film containing caffeine, Skin Pharmaco!. Physio!., 17, 119-123 (2004).