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. (c) 2008 Elsevier B.V. All rights reserved.
mixture optimization biomimetic emulsion response surfaces combined experimental design