Solvation Effects in the Quartz Crystal Microbalance with Dissipation Monitoring Response to Biomolecular Adsorption. A Phenomenological Approach

Quartz crystal microbalance with dissipation monitoring (QCM-D) has become a popular tool to investigate biomolecular adsorption phenomena at surfaces. In contrast to optical mass-sensitive techniques, which commonly detect the adsorbed nonhydrated mass, the mechanically coupled mass measured by QCM-D includes a significant amount of water. A mechanistic and quantitative picture of how the surrounding liquid couples to the deposited solutes has so far been elusive for apparently simple phenomena like the random adsorption of nanometer-sized particles on a planar surface. Using a setup that enables simultaneous measurements by reflectometry and QCM-D on the same support, we have quantified the variations in coupled water, as sensed by the QCM frequency response, as a function of coverage for the formation of monolayers of globular proteins, virus particles, and small unilamellar vesicles. We found a close-to-linear relationship between the surface coverage and the relative contribution of water to the freq...