The QCM biosensor is based on the use of immunomagnetic beads as a separator/concentrator for sample pretreatment as well as marker for signal amplification with simultaneous measurement of the changes in resonant frequency and resistance (Δ F and ΔR). The >ΔR measurement is more reliable than the ΔF measurement, and the detection limit based on the ΔR measurement is 10² cells/ml for Salmonella Typhimurium, which is 1,000~ 10,000 times lower than those of the ΔF and ΔR measurements without magnetic beads.

Temporal responses of resonant frequency and resistance of the QCM biosensor in the presence of anti-Salmonella magnetic beads. Numbers indicate concentrations (cells/ml) of S. Typhimurim in chicken meat sample.

X.-L. Su, Y. Li. 2005. A QCM immunosensor for Salmonella detection with simultaneous measurements of resonant frequency and motional resistance, Biosens.