Development of a skin care formulation using experimental designs

New cosmetic emulsion with biomimetic molecules have been investigated using experimental designs. For this purpose, six variables have been studied: the nature of surfactant (three mixture variables), the percentages of surfactant, co-surfactant and squalene, and five properties have been measured: stability, centrifugation, viscosity, pH, microscope analysis. Because of the complexity of the study, the optimization of these five responses has been carried out in two steps. First, a simple additive model has been postulated, in order to define a smaller domain of interest. A Doehlert, a grid and a simplex centriod designs have been built in order to generate candidate points. Exchange algorithm has allowed to extract a design with only 28 experiments. Results have shown that the percentage of squalene exhibits the greatest influence on the stability and on the viscosity of the emulsions. Secondly, a multiplicative model has been postulated using composite and simplex centroid design to generate candidate points. A set of 36 experiments has been selected. Conditions for the percentage of surfactant and co-surfactant, and for mixture variables have been determined in order to obtain a good compromise between the five responses.Finally, these studies have allowed to determine in the whole domain of interest an optimal formula composed only with biomimetic products and presenting good physico-chemical characteristics and stability.