In vitro drug release mechanism from cholesteryl ester-composed liquid crystalline system

Abstract

The present study has investigated the in vitro ibuprofen release profiles from a liquid crystalline system, which is composed of cholesteryl nonanoate (CNN), cholesteryl chloride (CCL) and cholesteryl oleyl carbonate (COC), with a combination ratio of CNN/COC/CCL=10/80/10 w/w/w. The presence of organized liquid crystalline structures was confirmed by polarizing light microscopy and x-ray diffraction, and the structures were shown to remain relatively unchanged after drug loading. The inclusion drug molecules remained in a molecularly distributed amorphous state as no crystalline drug evidence was found in the matrix as shown by DSC and x-ray diffraction studies. The in vitro ibuprofen release profiles most aptly fitted to the square root Higuchi release model, indicating that drug release was predominantly controlled by Fickian diffusion. Drug release was influenced by the phase transition of the liquid crystalline matrix, initial drug loading, as well as the viscosity of the matrix system.