Detection of human κ-opioid antibody using microresonators with integrated optical readout.

Label-free detection of the interaction between hexahistidine-tagged human κ-opioid receptor membrane protein and anti-His antibody is demonstrated in liquid by an optical microelectromechanical system utilizing electromagnetically actuated microresonators. Shift in resonance frequency due to accretion of mass on the sensitive surface of microresonators is monitored via an integrated optical readout. A frequency resolution of 2Hz is obtained. Together with a sensitivity of 7 ppm/(ng/ml) this leads to a minimum detectable antibody concentration of 5.7 ng/ml for a 50-kHz device. The measurement principle is shown to impart immunity to environmental noise, facilitate operation in liquid media and bring about the prospect for further miniaturization of actuator and readout leading to a portable biochemical sensor.