Detection of Staphylococcus Enterotoxin B at Picogram Levels Using Piezoelectric-Excited Millimeter-Sized Cantilever Sensors

Authors: CAMPBELL, GOSSETT - DREXEL UNIVERSITY; Medina, Marjorie; MUTHARASAN, RAJ - DREXEL UNIVERSITY

Submitted to: Sensors and Actuators B: Chemical
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2007
Publication Date: 9/1/2007
Citation: Campbell, G.A., Medina, M.B., Mutharasan, R. Detection of Staphylococcus Enterotoxin B at Picogram Levels Using Piezoelectric-Excited Millimeter-Sized Cantilever Sensors. Sensors and Actuators B: Chemical.126:354-360

Interpretive Summary: Foodborne pathogenic bacteria, Staphylococcus aureus, produce toxins that can cause serious gastroenteritis and many other discomforts even with trace quantities. Common heat processing of foods and normal cooking temperatures can kill the bacteria but the produced toxins, staphylococcal enterotoxin B (SEB), are not destroyed. Therefore, ingestion of heated or cooked contaminated foods can still cause enteric illness. The heat resistance of the SEB makes it also a potential bioterrorism agent. Thus, there is a need of good methods to detect trace levels of SEB in foods. In this research, we developed a novel biosensor system for detection of SEB in picograms or parts per trillion. The biosensor method successfully detected the presence of 12.5 to 50 parts per trillion of SEB in a buffer system. This biosensor technique is more sensitive than other previously reported methods and the novel method will be utilized for detection in food systems. This information will be useful for the food industry and regulatory agencies for monitoring the safety and the bio-security of our foods.

Technical Abstract: We report a highly sensitive and rapid method for thhe detection of Staphylocoiccus aureus enterotoxin B (SEB) at picogram levels using a piezolelectric-excited millimeter 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 resonant 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 resonant frequency and reached a steady state frequency change of 31 +/- 1 (n=2) and 208 +/- 1 (n=2) corresponding to SEB concentrations of 50 pg/mL and 12.5 pg/mL. Respectively. In each experiment, the bound SEB was released by a pH 2.) 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 buffer, pH 7.4. We also determined the detection limit of PEMC sensors to SEB detection to be between 12.5 and 50 pg/mL. At a concentration of 12.5 pg/mL, no significant change in resonant frequency was observed. The observed 1st order binding rate constant ranged from 0.104 to 0.029 per min in the concentration range of 50 pg/mL and 12.5 pg/mL.