Detection of Phase Transition in Photosensitive Liposomes by Advanced QCM

In this work an impedance-based quartz crystal microbalance (QCM) is used to detect heat-induced changes in the viscoelastic properties in the films of adsorbed liposomes. Liposomes are bound to a polymer-modified QCM surface, and heat is induced in the bilayer via light absorption into gold nanoparticles (GNPs) embedded in the liposomes. Because of very rapid heat transfer at the nanoscale, nanoparticles can reside either in the liposome cavity or within the bilayer to cause changes in the lipid viscoelasticity. The changes are observed as changes in the film relaxation time as well as by mapping the measured resonance frequency versus resistance. The QCM results indicate that viscoelastic changes occur throughout the vesicle layer, possibly causing fusion between the liposomes. The ultimate goal of the work is to develop a smart drug delivery system for the eye, whereby a drug loaded in the liposome can be released in a controlled manner by light triggering.