Piezoelectric crystal immunosensor for sensitive detection of methamphetamine (stimulant drug) in human urine

We have developed an immunosensor based on a piezoelectric quartz resonator, which detects methamphetamine (MA) in liquids from a shift of the resonant frequency. The sensor has MA-albumin conjugates immobilized on the resonator and its resonant frequency shifts downward on contact with the monoclonal antibody to MA dissolved in the phosphate buffer solution. Under the condition of a fixed concentration of the antibody, the frequency shift is attenuated by mixing MA with the antibody solution. Based on this principle, it has been possible to detect 0.02–100 ppm MA with a detection time of about 7 min. The sensor has proved to be sensitive and stable enough to detect the critical concentration (1 ppm) of MA in human urine.