Nano-emulsions as vehicles for topical delivery of forskolin

Abstract

Two O/W forskolin-loaded nano-emulsions (0.075 % wt.) based on medium chain triglycerides (MCT) and stabilized by a nonionic surfactant (Polysorbate 80 or Polysorbate 40) were studied as forskolin delivery systems. The nano-emulsions were prepared by the PIC method. The mean droplet size of the nano-emulsions with Polysorbate 80 and Polysorbate 40 with oil/surfactant (O/S) ratios of 20/80 and 80 % water concentration, measured by Dynamic Light Scattering (DLS), was of 118 nm and 111 nm, respectively. Stability of the formulations assessed by light backscattering for 24h, showed that both nano-emulsions were stable at 25ºC. Studies of forskolin in vitro skin permeation from the nano-emulsions and from a triglyceride solution were carried out at 32ºC, using Franz-type diffusion cells. A mixture of PBS pH 7.4 / ethanol (60:40) was used as a receptor solution. The highest flux and permeability coefficient was obtained for the nano-emulsion stabilized with Polysorbate 80 (6.91±0.75 μg·cm-2·h-1 and 9.21·10-3 ± 1.00·10-3 cm/h, respectively) but no significant differences were observed with the flux and permeability coefficient value of forskolin dissolved in the oil. The results have shown that the nano-emulsions developed in this study could be used as effective carriers for topical administration of forskolin.