Aqueous dispersions of organogel nanoparticles - Potential systems for cosmetic and dermo-cosmetic applications

OBJECTIVE: The preparation and physicochemical characteriza- tion of organogel nanoparticles dispersed in water have been devel- oped. These systems could be employed as nanocarrier for cosmetic applications or as hydrophobic reservoirs for drug delivery. METHODS: Gelled particles of organic liquid and 12-hydroxystea- ric acid (organogelator) were obtained by hot emulsification (T>Tgel), with a surfactant (acetylated glycol stearate) and poly- mers (sodium hyaluronate and polyvinyl alcohol) as stabilizing agents, and cooling at room temperature (T<Tgel). An organic UVB sunscreen molecule, obtained by microwave activation, was used as a hydrophobic model molecule. The physicochemical prop- erties of the starting organogel (gelation tests; rheological study) and the dispersed gelled particles (rheological study; particle mean size, size distribution, zeta-potential measurements; physical stabil- ity evaluation; UVB absorption and water resistance ability) were studied. The synthesis of sunscreen compound using microwave activation was also described. RESULTS: According to the gelation test results, organogels were obtained with various organic liquids. Vaseline and almond oils were selected as organic medium for the gelled nanoparticle prepa- ration. A preliminary formulation study was carried out in order to determine the optimal experimental conditions to obtain stable nanoparticle dispersions. Gelled nanoparticles contained the sun- screen model molecule, with mean size of 450 nm, polydispersity index of 0.18 and zeta-potential value above 30 mV, were obtained by ultrasound probe homogenization method. A compara- tive study of their dispersion ageing showed a greatly enhanced stability after gelation. According to the UVB absorption evalua- tion, gelled particles improved the photoprotective ability and the photostability of immobilized UVB blocker. They showed a high water resistance (~83%) even after 40 min of immersion. CONCLUSION: The obtained results demonstrate the interest of these gelled nanoparticles and their aqueous dispersion for the Correspondence: Universite Claude Bernard Lyon 1, EA4169 “Aspects fondamentaux, cliniques et therapeutiques de la fonction barriere cutanee”, SFR Lyon-Est Sante - INSERM US 7 – CNRS UMS 3453, ISPB, Laboratoire de Pharmacie Galenique Industrielle, plateforme FRIPHARM, 8 Avenue Rockefeller, F-69373 Lyon cedex 08, France. Tel.: +33 4 78 77 72 47; fax: +33 4 78 77 42 47; e-mail: plamen.kiri- lov@univ-lyon1.fr preparation of new formulations for cosmetic and dermo-cosmetic applications.