Quartz crystal microbalance with dissipation monitoring and the real-time study of biological systems and macromolecules at interfaces

QCM-D technique is based on the physical phenomenon that generates an acoustic shear wave with an oscillating resonance in quartz resulting in an evanescent wave that arises at the interface of the quartz and the solution. The amplitude of the acoustic wave is influenced by the deposition of material onto the quartz surface and from the subsequent decrease of the frequency the bound mass can be calculated. The dissipation shift which arises inform about viscoelasticity and flexibility of the adsorbed material. QCM-D can be applied for real-time studies of several biological systems since it is a simple, fast, low-cost and sensitive technique without having to label any sample. Common applications in biological field include measurements on adsorption of lipids, proteins, DNA and cells directly onto the surface of the sensor, which generally are chemically modified by self-assembled monolayer (SAM) technique or by spin-coated polymers. QCM-D can also be used to study molecular interactions between macromolecules and adsorbed materials. Three examples of the use of this technique are presented, namely the docking orientation of the C2 domain of PKC epsilon on phospholipid membranes, the conformational changes of fibrinogen adsorbed to model acrylic polymers and the attachment of endothelial cells to carboxylated polymers of different configuration.