Conductometric immunosensors for the detection of staphylococcal enterotoxin B based bio-electrocalytic reaction on micro-comb electrodes

Staphylococcal enterotoxin B (SEB) is one of many toxins produced by the Gram-positive bacterium Staphylococcal aureus. While SEB is known as the causative agent of certain food poisonings it is also considered abiological select agent. Thus, rapid and accurate identification of SEB during either surveillance or in response to a biothreat is critical to the mitigation of the suspect agent. This report presents a new conductometric immune-biosensor for the detection of SEB based on immobilization of horseradish peroxidase (HRP)-labeled SEB antibody (HRP-anti-SEB) onto nanogold/chitosan-multiwalled carbon nanotube (Au/CTS-MWNT)-functionalized biorecognition interface. The formation of the antibody-antigen complex by a simple one-step immunoreaction between the immobilized HRP-anti-SEB and SEB in sample solution introduced a barrier of electrical communication between the immobilized HRP and the base surface, thus local conductivity variations could be evaluated by the bio-electrocatalytic reaction of HRP in 0.02 M PBS (pH 6.8) containing 0.15 mM H2O2, 0.06 M KI and 0.1 M NaCl. Under optimal conditions, the proposed immune-biosensor exhibited a good conductometric response relative to SEB concentration in a linear range from 0.5 to 83.5 ng/ml with a correlation coefficient of 0.998. The developed immune-biosensor showed an acceptable accuracy, reproducibility and stability. Milk samples spiked with various concentrations of SEB gave an average of 116% recovery of the toxin.