Physicochemical stability evaluation of liquid crystalline O/W emulsions
Roberta B Rigon, Silas Arandas Monteiro e Silva, Gislaine Ricci Leonardi and Marlus Chorilli
São Paulo State University, Brazil
Freie Universität Berlin, Germany
Federal University of São Paulo, Brazil
University of Campinas, Brazil
: J Pharm Drug Deliv Res
Abstract
Liquid crystals are applied in the pharmaceutical and cosmetic industries due to the fact that they can promote a controlled drug delivery system and more physicochemical stability when it compare to emulsions. The aim of this study was verify the stability of liquid crystals in cosmetic formulations. Liquid crystal structures were confirmed by polarized light microscopy. Physicochemical characteristics were measured during 60 days and formulations were stored in different conditions of temperature. Organoleptic characteristics, centrifugation, pH value, viscosity and rheological behavior were evaluated to verify the formulations stability. The results demonstrated that there was no alteration in the organoleptic characteristics in any samples and there was no phase’s separation after centrifugation process. The pH values changed after 60 days when storage in different temperatures, however changes in pH may not affect the physiological skin surface pH. The lamellar liquid crystal was observed in all formulations analyzed; however some formulations presented also hexagonal liquid crystal. All samples presented non-Newtonian pseudoplastic behavior (n<1) and thixotropic. Cetearyl alcohol and sodium cetearyl sulfate promoted more stability in crystalline liquid and viscosity maintenance (p<0.01) for all storage temperature, during 60 days, proving the good physical stability. It was observed also good stability in viscosity and crystalline liquid structures maintenance (p<0.01) for the formulation composed by cetearyl alcohol, sodium cetearyl sulfate, triceteareth-4 phosphate and oleth-10. All results demonstrated that the presence of thick agent cetearyl alcohol and the surfactant sodium cetearyl sulfate can promote the formation of liquid crystal structures with good physicochemical stability.
Biography
Email: roberta_rigon@yahoo.com.br
