Detection of Staphylococcus enterotoxin B at picogram levels using piezoelectric-excited millimeter-sized cantilever sensors

We report a highly sensitive and rapid method for the detection of Staphylococcus aureus enterotoxin B (SEB) at picogram levels using a piezoelectric-excited millimeter-sized cantilever (PEMC) sensor. Affinity purified polyclonal antibody to Staphylococcal enterotoxin B (anti-SEB) was immobilized on the aminated cantilever glass surface, followed by exposure of SEB containing samples flowing at a rate of 1 mL/min. The binding of SEB was measured by monitoring the sensor's fundamental resonance frequency. The fundamental frequencies in air and under liquid immersion were 17.50 ± 0.01 kHz and 10.37 ± 0.01 kHz, respectively. Binding of SEB to the sensor surface resulted in an exponential decrease of the resonance frequency and reached a steady state frequency change of 31 ± 1 Hz (n = 2) and 208 ± 1 Hz (n = 2) corresponding to SEB concentrations of 50 pg/mL and 12.5 ng/mL, respectively. In each experiment, the bound SEB was released by a pH 2.0 HCl/PBS solution and the sensor response was nearly identical to the frequency change caused by attachment. Full antibody surface regeneration was obtained after the release by rinsing the sensor with PBS pH 7.4. We report the detection limit of PEMC sensors to SEB is between 12.5 pg/mL and 50 pg/mL.