Response surface methodology for the optimization of ubiquinone self-nanoemulsified drug delivery system

The aim of the present study was to prepare and evaluate an optimized, self-nanoemulsified drug delivery system of ubiquinone. A 3-factor, 3-level Box-Behnken design was used for the optimization procedure with the amounts of Polyoxyl 35 castor oil (X1), medium-chain mono- and diglyceride (X2), and lemon oil (X3) as the independent variables. The response variable was the cumulative percentage of ubiquinone emulsified in 10 minutes. Different ubiquinone release rates were obtained. The amount released ranged from 11% to 102.3%. Turbidity profile revealed 3 regions that were used to describe the progress of emulsion formation: lag phase, pseudolinear phase, and plateau turbidity. An increase in the amount of surfactant decreased turbidity values and caused a delay in lag time. Addition of cosurfactant enhanced the release rates. Increasing the amount of the eutectic agent was necessary to overcome drug precipitation especially at higher loading of surfactants and cosurfactants. Mathematical equations and response surface plots were used to relate the dependent and independent variables. The regression equation generated for the cumulative percentage emulsified in 10 minutes was Y1 = 90.9 - 22.1X1 + 5.03X2 + 13.95X3 + 12.13X1X2 + 15.13X1X3 - 14.40X1(2) - 6.25X3(2). The optimization model predicted a 93.4% release with X1, X2, and X3 levels of 35, 35, and 30 respectively. The observed responses were in close agreement with the predicted values of the optimized formulation. This demonstrated the reliability of the optimization procedure in predicting the dissolution behavior of a self-emulsified drug delivery system.