Development of indirect-competitive quartz crystal microbalance immunosensor for C-reactive protein

A highly sensitive indirect-competitive quartz crystal microbalance immunosensor for a cardiovascular biomarker, C-reactive protein (CRP), was developed. The sensor system was constructed with a buffer reservoir, a micro-dispensing pump, an injector, a flow-through cell with a sensor chip, an oscillator module, a frequency response analyzer and a PC. The reaction buffer for the system was 0.1 M sodium phosphate buffer (pH 7.0). The optimum concentrations of CRP for immobilization and an anti-CRP antibody for competition reaction were 2 and 0.250 mg/mL, respectively. When plotted in double-logarithmic scale, a linear relationship between CRP concentration and sensor response was obtained in a wide concentration range of 0.130–25,016 ng/mL of CRP, together with the limit of detection of 0.130 ng/mL.