Effect of oil and co-surfactant on the formation of Solutol HS 15 based colloidal drug carrier by Box–Behnken statistical design

The present study provides an overview to design and optimize self-emulsifying system as colloidal drug carrier for oral delivery of hydrophobic drug using a new surfactant Solutol HS15. The formulation components i.e. surfactant, co-surfactant and oil were investigated to construct a pseudoternary phase diagram. Box–Behnken experimental design was employed as statistical tool to optimize the formulation variables, X1 (Propylene glycol monocaprylate as oil), X2 (Solutol HS15 as surfactant), and X3 (Transcutol HP as cosurfactant). Formulations were assessed for percentage transmittance, droplet size and emulsification efficacy. Transcutol HP was found to be better than other investigated cosurfactants with Solutol HS15, to solubilize the aqueous and the oil phase. Furthermore, the results revealed the significant influence of the surfactant/cosurfactant mass ratio (Km) to form self-emulsifying system of colloidal dimension. Km value 2 was observed to exert a synergistic effect. There was a good correlation between percentage transmittance of diluted self-emulsifying system and droplet size analysis (R2 = 0.951).