Last updated: 8/16/2013
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
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.
3. Simultaneous QCM-D and Extended gate Field Effect Transistor (EGFET)
A merged quartz crystal microbalance with dissipation (QCM-D) sensor and extended gate field effect transistor (EGFET) was used to monitor biomolecular interactions. The biosimultaneously provides multiple on electrochemical, thickness/flexibility, and structural changes which accompany bio-molecular interactions. The sensing environment is separated from FET by wiring the gate to the external working electrode- the gold electrode of the QCM-D device- and thus reduce solution interference. The setup utilizes a commercial, affordable MOSFET, hard wired to the QCM-D setup without having to undergo complicated nanofabrication procedures. In this paper, characterization of I-V of the novel EGFET setup, monitoring of avidin-biotin, and binding between calmodulin and its binding moieties are presented. Combined electrochemical and thickness data clearly demonstrated data acquisition on electrochemical change, adlayer thickness change and structural change upon binding. .
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.
· Modeling and Simulation Study
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.