Viscoelastic adlayers of collagen and lysozyme studied using quartz crystal microbalance with dissipation monitoring

In this study the effects of molecular structure of proteins on their adsorption behaviour and viscoelasticity are investigated using a QCM-D method. The adsorption measurements show that spherical lysozyme is rapidly adsorbed on the gold surface as a stiff monolayer, as indicated by a sharp drop in the oscillation frequency (Deltaf) of the sensor, and by a very small increase in the energy dissipation of the adlayer (DeltaD). Fibrous calfskin collagen (CSC) is, however, adsorbed on the same surface rather slowly in two steps to form a thick and soft multilayer (large Deltaf and DeltaD) at pH 3 in salt-free conditions. The two-step adsorption is not observed for stiffly aggregated CSC. This study clearly demonstrates that the polymer structure strongly affects not only how adsorption develops but also the viscoelastic properties of the adlayer.