(603g) Theoretical and Experimental Analysis of QCM-D Sensor for Monitoring of Biomolecular Binding

The quartz crystal microbalance with dissipation (QCM-D) sensor offers great potential as a biosensor for the fast, reliable, and economical monitoring of biomolecular binding. Thus far, most applications of the QCM-D sensor have employed high concentration(> microM) and large volume of analytes (~ml). In this study, protocols were optimized for characterization of biomolecular binding models at the level lower than micro and with minimal amount of analytes. The mass adsorption on the sensing surface was also simulated using COMSOL software to aid in the optimization of the sensing protocols. The molecules used for this study was calmodulin (CaM), which is a ubiquitous Ca2+ sensor protein which can regulate many important biological functions, and its multiple binding partners - calcinuerin protein and several CaM binding peptides. The sensor surface was modified by various methods including direct absorption to the gold surface, amino coupling on mixed self-assembled monolayer (SAM), and biotin-avidin capture. The optimized sensing protocols were presented as well as the simultaneous fluid and mass transfer within the sensing chamber was visualized through simulation. Binding between CaM and its binding partners was successfully monitored using the QCM-D sensor at nanomolar concentrations. Moreover, the frequency and dissipation change of the QCM-D sensor also indicated structural change during the binding if the molecules undergo major structural change. In conclusion, this study demonstrated that the QCM-D sensor was capable of monitoring biomolecular interactions in real time with high sensitivity and versatility in surface modification, reading small volume samples (less than 200uL) at low concentrations (~nM).