Fabrication of Bacillus cereus electrochemical immunosensor based on double-layer gold nanoparticles and chitosan

A novel Bacillus cereus electrochemical immunosensor was fabricated using double-layer gold nanoparticles and chitosan. The sensing element of the immunosensor was comprised of gold nanoparticles fixed with monoclonal antibodies of B. cereus. Chitosan, as the bridge cross-linker, was used to immobilize the sensing element onto the glassy carbon electrode because of its excellent adhesion, film forming ability and biocompatibility properties. To examine the quality of the synthesized gold nanoparticles, the size, shape and dispersion of the gold nanoparticles were characterized by transmission electron microscopy (TEM) and UV–visible spectral scanning. To assess the quality of the different steps in immunosensor fabrication, each procedure in its assembly was monitored by cyclic voltammetric and alternating current impedance. Chronoamperometry was used to measure the concentration of B. cereus. The biosensor sensitivity in pure cultures of B. cereus was found to be 5.0 × 101 to 5.0 × 104 cfu/mL (R = 0.9966) with a detection limit (S/N = 3) of 10.0 cfu/mL. In summary, we fabricated an immunosensor that exhibited a fast detection response and high sensitivity to bacterial contamination. Moreover, the immunosensor exhibited high reproducibility and long-term stability thus making it ideal for applications in food quality and safety control.