Development and characterization of micellar systems for application as insect repellents.

N,N-diethyl-meta-toluamide (DEET) is a widely used insect repellent due to its high efficacy. In this work, micellar systems based on poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer were developed and studied for the purpose of controlling the release and cutaneous permeation of DEET, using concentrated solutions of the copolymer Pluronic F127 to form thermoreversible gels. The formulations presented thermoreversible gelation above 5°C and altered rheological behavior at 15 and 25°C. The presence of the drug drastically changed the sol-gel transition temperatures. The micrographs suggest that DEET induced the formation of anisotropic structures, and Maltese Crosses were observed. The formulation containing 10wt% DEET and 15wt% Pluronic F127 presented sustained drug release for up to 7h. DEET release profile followed the Higuchi kinetics model. There was a reduction of approximately 35% in the amount of DEET absorbed through the skin after 6h. About 62% of DEET from the formulation consisting of Pluronic F127 and DEET remain retained on the skin. The anisotropic structure may constitute a barrier to diffusion and thereby controlling the drug release effectively. These tests suggest that the tested samples exhibit safety profile greater than some commercially available products.