The use of fluorescence resonance energy transfer to study the disintegration kinetics of liposomes containing lysolecithin and oleic acid in rat plasma

Purpose. To validate Fluorescence Resonance Energy Transfer (RET) as method to monitor disintegration of fluorescently labeled liposomes varying in ly solecithin/oleic acid (equimolar) content, lysolecithin fatty acid composit ion and vesicle size in rat blood plasma and buffer. Methods. NBD-PE and Rho-PE were used for RET. The measurements were perform ed on a Perkin Elmer LS-50 spectrofluorimeter. Liposomes were prepared by t he extrusion method. Results, Analysis of the RET data was optimised using a fitting procedure t o correct for fluorescence interference by plasma. The disintegration patte rns of liposomes could be described by a biexponential decay model. Disinte gration rate increased at increasing lysolecithin/oleic acid content and de creasing size. In contrast, all liposomes showed no disintegration in buffe r. Conclusions. RET is a suitable method to monitor liposome disintegration in non-diluted plasma. Rate and extent of liposome disintegration increases a t decreasing liposome size and increasing lysolecithin/oleic acid content.