Computational design strategy: an approach to enhancing the transdermal delivery of optimal capsaicin-loaded transinvasomes.

The aim of this study was to design and develop simultaneous optimal transinvasome formulations (OTV) to enhance the transdermal delivery of capsaicin. Using a central composite experimental design with duplicate centroids, 10 model formulations of transinvasomes (TVs) were demonstrated. The lipid compositions of the TV formulations were determined as formulation factors (Xn) and response variables (Yn), respectively. TV formulations containing a constant concentration of phosphatidylcholine, cholesterol, 0.15% capsaicin, and various percentages of d-limonene (X1) and cocamide diethanolamine (X2) were prepared. The physicochemical characteristics, e.g. the vesicle size, size distribution, zeta potential, entrapment efficiency, and skin permeability, of the TV formulations were experimentally investigated. The relationship among the formulation factor, the response variables, and the OTV was predicted using Design Expert® software. The accuracy and reliability of the OTV predicted using computer software were experimentally confirmed and investigated as an experimental transinvasome formulation (ETV). The results indicated that the skin permeability of the ETV was close to the OTV and was significantly higher than that of conventional liposomes and commercial products. The response surfaces estimated by the computer software were helpful in understanding the complicated relationship among the formulation factor, the response variables, and the stability of the TV formulation.