Piezoelectric quartz crystal sensors applied for bioanalytical assays and characterization of affinity interactions

This review presents piezoelectric quartz crystals as transducers suitable for development of different types of bioanalytical assays. The components of measuring systems for piezosensors are described together with providers of commercial equipment. The piezoelectric biosensors are summarized for determination of viruses, bacterial and other cells, proteins, nucleic acids and small molecules as drugs, hormones and pesticides. In addition to mass changes, some agglutination assays employing viscosity effects are addressed. Finally, the direct label-free and real-time monitoring of affinity interactions using piezosensors is presented. The theoretical background for determination of appropriate kinetic rate and equilibrium constants is shown and the approach is demonstrated on the interaction of antibody with the corresponding antigen ( protein secalin). Several examples of affinity studies are provided, including interactions of proteins ( antibody and antigens, receptors and ligands), nucleic acids ( hybridization, intercalation of metal complexes), lipids and saccharide-based layers.