Development and optimization of surfactants and UV filters formulation in sunscreens based on organic and nanocomposite molecules using experimental design and nanodispersion techniques

Optimization of skin care emulsions from the viewpoint of surfactants and ultraviolet filters formulation has been investigated using the experimental design. In this study, due to the variety of factors affecting the final product, the continuous process has been executed in two studies (optimization of basecream and sunscreen). For the first study, six variables such as surfactants nature (three mixture variables), the percentages of surfactant, solvent and temperature have been investigated and stability and viscosity have been measured as responses. Using the exchange algorithm based on D-optimality criteria, a multiplied model has been supposed and a series of 45 experiments has been selected. In the second study, by Box-Behnken design a set of 51 experiments of sunscreens from the photoprotective efficacy and photostability viewpoint have been formulated and evaluated. These sunscreens contain four photo-protective organic filters such as benzophenone-4, octyl salicylate, octyl methoxy cinnamate and avobenzone and a new nanocomposite in which nanoparticles of TiO2 are dispersed onto micrometric ZnO particles by dry nanodispersion methodology at different percentages. The method was based on UV spectroscopic indices such as SPF, UVA/UVB ratio, UVA1/UV ratio, critical wavelength (CW), spectral uniformity index (SUI) and area under curve (Auc). Finally, these studies have been presented the optimal formulation for skin care emulsions to improve the sunscreen UVA and UVB protection.