Preparation and Evaluation of Repaglinide-Loaded Liposomes via Thin Film Hydration: Impact of Excipients on Formulation Properties

Abstract

The study was undertaken to formulate and analyze repaglinide loaded liposomes to obtain a sustained release dosage form over an extended period of time. All the formulations were prepared by thin film hydration method one of the suitable methods for preparing liposomes. Different formulations were designed to observe the effect of lecithin, cholesterol, nigella oil, stearylamine, Tween 80, Span 80, and sodium lauryl sulfate on percent of drug entrapment efficiency, cumulative drug release, permeation through the membrane, stability, and uniformed vesicular structure, respectively. Microscopic observation was performed to confirm the presence of liposomal vesicles, in vitro dissolution study and ex vivo permeability studies were carried out according to USP-II paddle method in phosphate buffer (pH 7.4) for a period of 8 hours. Additionally, comparison between the formulated liposomes was performed to ensure sustained release characteristics of liposomal formulations. Stability study was executed by storing formulations under different environmental conditions for a period of 30 days. Visual observation under optical microscope displayed the presence of unilamellar liposomal vesicles formed by thin film hydration method. The percent drug entrapment efficiency of conventional liposomes was found to be highest for the formulation F-10 (73 .26%) with a ratio of 1:0.44 (phosphatidylcholine: cholesterol). Addition of tween 80 and span 80 to the formulations, stabilized liposomes which exhibited higher entrapment efficiencies for formulations F-24 (81.43%), F-29 (78.98%) and F-34 (89.67%) compared to non-ionic surfactants free liposomes. The drug release of repaglinide from conventional liposomes was found to be 96.23% at the 8^th hour. For non-ionic surfactants incorporated liposomes, 84.52% drug release obtained for the formulation F-34 at the 8^th hour from which it can be predicted that non-ionic surfactants incorporated liposomes can prolong drug release for more than 10 hours. The best data fitted with the highest correlation coefficient for liposomes was obtained for zero order kinetic models and the drug release was mostly by super class II diffusion transport for most of the formulations. Results from the stability study showed that the drug leakage from the vesicles was least when non-ionic surfactant was incorporated into the formulations and among the three storage conditions, all the liposomal formulations were found to be most stable at refrigeration temperature (2-8°C).

Bangladesh Pharmaceutical Journal 29(2): 161-171, 2026 (July)