Combined Reflectometric Interference Spectroscopy and Quartz Crystal Microbalance Detect Differential Adsorption of Lipid Vesicles with Different Phase Transition Temperatures on SiO2, TiO2, and Au Surfaces.

Quantitative analysis of biomolecular adsorption on a substrate is crucial for understanding biomolecular interactions. A quartz crystal microbalance (QCM) is a highly sensitive device to detect such interactions based on mass. However, the physicochemical analysis by the QCM alone often leads to overestimation of the actual adsorbed mass. Here, a combined reflectometric interference spectroscopy (RIfS) and QCM is developed to simultaneously analyze adsorption of biomolecules. RIfS detects the adsorbed mass based on the reflectance and predicts the adsorbed condition by modeling the reflection spectra using the transfer matrix method. In contrast, the QCM detects physicochemical characteristics of the adsorbed molecules along with the adsorbed mass. The combined RIfS-QCM successfully detected the adsorption of proteins with different surface properties and lipid vesicles with different phase transition temperatures. The initial stage of adsorption revealed distinct individual properties of the adsorbates. Moreover, the RIfS-QCM revealed differential adsorption of the vesicles on silicon dioxide, titania, and gold surfaces, and the differences in adsorption were further interrogated by atomic force microscopy. The results demonstrate that the RIfS-QCM serves as a useful tool to quantitatively analyze molecular adsorption on various surfaces.