An electrochemical impedimetric immunosensor for label-free detection of Campylobacter jejuni in diarrhea patients’ stool based on O-carboxymethylchitosan surface modified Fe3O4 nanoparticles

A novel electrochemical impedimetric immunosensor based on O-carboxymethylchitosan surface modified Fe3O4 nanoparticles (denoted as OCMCS-Fe3O4 nanoparticles) was developed for rapid detection of Campylobacter jejuni, which is becoming the most common cause of gastroenteritis in developed countries and raising major public health concerns worldwide. In the present study, anti-FlaA monoclonal antibodies 2D12 (denoted as 2D12McAbs) were immobilized on OCMCS-Fe3O4 nanoparticles. The detection was performed by measuring relative change in impedance before and after 2D12McAbs-Campylobacter jejuni reaction with the technique of electrochemical impedance spectroscopy. Under the optimized conditions, the relative change in impedance was proportional to the logarithmic value of Campylobacter jejuni concentrations in the range of 1.0 × 103 to 1.0 × 107 CFU/mL (r = 0.991). The advantages of the OCMCS-Fe3O4 nanoparticle-based immunosensor are simplicity of use, fast response, wide linear range, acceptable reproducibility and long stability. Moreover, the immunosensor could be regenerated by being treated with glycine–HCl buffer solution (pH 2.8). We demonstrate the convenient application of the novel immunosensor for the detection of Campylobacter jejuni in diarrhea patients’ stool samples.