The dissipative QCM-D technique: interfacial phenomena and sensor applications for proteins, biomembranes, living cells and polymers

Biological substances in contact with solid, non-biological materials, is a situation of broad scientific interest and technological importance, and there is a growing need for new tools to study these interactions. Among many different properties of the biological films formed at the interfaces, the viscoelastic properties are of central interest, since these properties can be used as a discriminator in biosensing and in the study of polymer films. We have developed a sensor system based on the traditional quartz crystal microbalance (QCM) technique, but where both the resonant frequency (f) and the energy dissipation (D) are measured simultaneously for a non-driven (freely oscillating) sensor crystal. This provides accurate and precise measurements of f and D in the gaseous and liquid phases. The performance of this so called QCM-D system is illustrated by measurements of protein adsorption and antibody-antigen reactions, biomembrane formation on surfaces from vesicles in solution, cell attachment experiments, and polymer cross-linking kinetics.