Electrical Detection of Biomolecules Using Newly Proposed Measurement Principle of Dynamic Microcantilever Sensors

Electrical Detection of Biomolecules Using Newly Proposed Measurement Principle of Dynamic Microcantilever Sensors
Issue Date
Biosensors 2014
Over the last two decades, miniaturized cantilever sensors have been widely used for biological and chemical sensing applications. While cantilever sensors in air or vacuum condition have outstanding sensitivity, cantilever sensors in liquid environment where most of bioreactions occur has sensitivity degradation issue caused by reducing quality factor in liquid viscous damping. There have been introduced techniques to overcome this critical issue such as microchannel-suspended resonators and resonating in air-liquid interface. However these approaches still have a limitation to apply in portable analysis system because they utilized a bulky optical apparatus for measurement of resonant property. Here we fabricated a novel piezoelectric-driven microcantilever sensor with micro-slit for continuous monitoring of bioreactions in liquid. Our microcantilever sensor allowed electrical sensing of resonant frequency of cantilever in liquid damping-minimized environment. Electrical DC signal from two pairs of Pt electrodes on the free end of vibrating cantilever transmitted to fixed two electrodes crossing the micro-slit. We could measure the resonant frequency of cantilever by monitoring the magnitude of DC signal from two pair electrodes on the cantilever sensor. The micro-slit with distance of 5 µm separated liquid-air interface between upper and bottom sides at a meniscus for improving resonating characteristics. The quality factors of our microcantilever sensors after liquid injection on the top surface of cantilever were more than 25 which was much better than value (2~4) in case of filling out at top and bottom surface of cantilever. With these microcantilever sensors, we detected prostate specific antigen (PSA). When PSA antigen with concentration of 1, 10 and 100 ng/mL was injected, change in resonant frequency cantilever sensor with PSA antibody receptor after reach at stabilization region were 60, 113, 16
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