Liquid crystalline formulations containing modified surface TiO2 nanoparticles obtained by sol-gel process

Abstract

Titanium dioxide (TiO2) is an inorganic compound used as sunscreen in cosmetic/pharmaceutical formulations as a way to prevent the skin cancer. In this work we have used surface modified titania nanoparticles obtained by thermo-reversible sol-gel transition showing transparency in the range of temperature typical for sunscreen use (between 20 and 45 A degrees C). The goal of this work was to develop and characterize liquid crystalline cosmetic formulations containing surface modified titania nanoparticles. We have analyzed the citotoxicity of the nanoparticles, their zeta potential and the liquid crystalline phase behavior of the formulations. The violet crystal assay has shown no citotoxicity associated to the presence of surface modified groups on the two cell lines tested, human keratinocytes and fibroblasts, presenting more than 70% of cell viability for all analyzed nanoparticles. The zeta potential measurements revealed a negative charged surface for TiO2 nanoparticles at pH values in the range of 6.5-7.0, preventing the aggregation and maintaining the final transparency of the liquid crystalline sunscreen formulations. The polarized light microscopy, associated to SAXS, have shown the presence of liquid crystalline phases both with and without TiO2 nanoparticles. The charged surface of TiO2 nanoparticles maintains the stability of the formulations and the liquid crystalline structure. This renders this system a good candidate for being used simultaneously as sunscreen and as controlled release system of anti cancer drugs.