Detailed analysis of liposome adsorption and its rupture on the liquid-solid interface monitored by LSPR and QCM-D integrated sensor

Liposomes have been attracted attention, because liposomes can mimic the lipid bilayer membrane of cells. Scientists apply liposomes for drug delivery systems (DDSs) and for artificial cells. Hence, the handling of liposomes is very important. In particular, it is difficult to control the adsorption of the liposome onto the target selectively and the release of the drug by its own rupture. Therefore, scientists are looking for the way to carefully monitor the behavior of liposomes from adsorption to rupture in deep. We integrated quartz crystal microbalance dissipation (QCM-D) and localized surface plasmon resonance (LSPR) into a single sensor and monitored the signals from the sensor on the adsorption and rupture of liposome. The integrated sensor detected resonance frequency and dissipation from QCM-D, and wavelength shifts from LSPR simultaneously. The integrated sensor successfully monitored conformational changes of liposomes in real time upon exposure to the surfactant, Triton X-100. The data clearly revealed liposome adsorption and deformation, and disruption of membrane integrity by normalizing three signals, resonance frequency, resonance resistance and wavelength shift. In fact, we found that normalized signals were divided into 5 steps through the experiment: liposome adsorption, liposome deformation slightly, liposome conjugated with micelles of surfactant, liposome disruption and lipid bilayer covered on the surface. These results indicate that our device provides a powerful tool to gain deeper insights into biomolecular interactions, expanding numerous applications such as monitoring of conformational changes in proteins, oligonucleotides, viruses, bacteria, vesicles, and cells.