Last updated: April 2010
A sensing unit of QCM-D sensor is a thin quartz crystal (diameter 2.5 cm, thickness 1mm) with thin gold electrodes coated in both sides. The crystal is piezoelectric resonators where the resonant frequency varies linearly with the mass of adsorbed layers on the surface when it is in contact with air. After it was shown that the QCM might be used in the liquid phase, the number of applications for the QCM has increased dramatically. In liquid, an adsorbed film may consist of a considerably high amount of water, which is sensed as a mass uptake. By measuring several frequencies and the dissipation it becomes possible to determine whether the adsorbed film is rigid or water-rich. The QCM-D sensor monitors dissipation, allowing biomolecular detection in liquid. Read more in www.qsense.com
QCM-D sensor setting
It is critical to develop a reliable deposition method that can ensure sufficient amount of protein/peptides can be deposited onto the QCM surface in a controllable manner. Several strategies are known to effectively deposit proteins onto the sensor surface. They include direct adsorption onto citrate coated surface, amine or thiol coupling onto self assembled monolayers (SAM) or via linkage of streptavidin – biotin.
Detection of specific DNA/RNA sequences is important in numerous applications including clinical diagnosis such as genetic disorders and pathogen detection. The detection of mismatched base pairs in DNA plays a crucial role in the diagnosis of genetic-related diseases and conditions, especially for early stage treatment. The Quartz Crystal Microbalance with Dissipation (QCM-D) sensor combined with electrochemical impedance spectroscopy (EIS) are used to monitor DNA hybridization and mismatched base pair detection. The QCM-D technique measures the adsorbed mass change while EIS gives additional electrochemical signal change.
My post-doc research topic was elucidating a role of olfactory marker protein (OMP) in the olfactory signal transduction cascade. Using the confocal imaging of intracellular Ca2+ in the living olfactory tissue, the intake and extrusion of Ca2+ was studied in normal and OMP-KO mice. Study of enigmatic OMP is still on-going quest.
Schematic of olfactory transduction in OSN cilia and effects of calmodulin (Ca2+/CaM).
Simultaneous fluid, diffusion-convection, and mass adsorption model in the biosensor was developed and studied using the COMSOL Multiphysics. Effects of feed concentration, flow rates, and binding rate constants on the sensor gram are often simulated. The study can be used to optimize the sensing conditions and guide determination of the affinity upon biomolecular interaction. The study can be used to optimize the sensing conditions and guide determination of the affinity upon biomolecular interaction. See details in http://www.comsol.com/papers/6561/
Transient concentration profile of the species B (left) and bound complex (right) at the upper surface for time points of 1, 15, 30, 45, 60, 75 seconds.
Novel MEMS or NEMS based biosensor development is being pursued.