October 17, 2014
Quantification of Charge-Mediated Fusion Events Between Giant Unilamellar Vesicle and Fusogenic Liposomes
Small cationic liposomes, termed “fusogenic liposomes”, as a drug carrier system, have been studied for almost twenty years. My summer research focused on quantifying charge-mediated fusion events between giant unilamellar vesicles (which acts as model cell membranes) and small liposomes (as drug capsules) using fluorescence microscopy. Two different assays were employed to accomplish this goal. In the lipid membrane-mixing assay, the vesicles were labeled with a FRET pair of fluorophores: the GUVs with Rhodomine (Rho) and the liposomes with nitro-2,1,3-benzoxadiazol-4-yl (NBD). Changes in fluorescence intensity of GUVs upon fusion were monitored using FRET and analyzed with a Matlab algorithm. In the content mixing assay, liposomes were loaded with highly concentrated calcein – fluorescent molecule- in sucrose. Changes in calcein fluorescence intensity inside the GUVs after fusion were analyzed to estimate the degree of calcein dilution, based on which the number of fused liposomes per GUVs can be approximated.