Abstract

Liposomes are bilayer membrane vesicles that have been used as drug delivery system. Advancing this delivery system through membrane asymmetry has attracted attention on liposomal research.
This research goal is to formulate asymmetric liposomes via a simpler cyclodextrin-lipid exchange method compared to that firstly produced by E. London and co-workers. Our method includes preparing the cyclodextrin, CD, in an aqueous solution and adding the organic solution with the lipid (POPC, DOTAP) dropwise into the CD solution, hence CD-lipid complex (donner) will form. Complexation was confirmed by infrared spectroscopy, differential scanning calorimetry, and nuclear magnetic resonance. Thin film hydration method applied to form large unilamellar vesicles (acceptor). Then, equal volumes of CD-lipid complex and acceptor vesicles mixed at 22°C for about 1 hour to permit lipid exchange. Then formed asymmetric liposomes were pelleted and collected after centrifugation. The asymmetry of liposomes was proven by fluorescence quenching and zetapotential methods. Bromocresol green, BCG, was used to study asymmetric membrane’s integrity and the most optimised formulation included POPC in the outer leaflet and POPC (15%), DOTAP (45%), and cholesterol (40%) in the inner leaflet. This formula entrapped 92.5% salmon sperm DNA.