Label free polyaniline based impedimetric biosensor for detection of E. coli O157:H7 Bacteria

A new and simple method for label free, rapid and inexpensive impedimetric sensing of Escherichia coli O157:H7 (a highly infectious and potentially fatal food and water borne pathogen) using antibody–antigen binding method based on covalently linked antibody on a conducting Polyaniline (PANI) film surface is reported. Electrochemical impedance spectroscopy (EIS) was used to test the sensitivity and effectiveness of the sensor electrode by measuring the change in impedance values of electrodes before and after incubation with different concentrations of bacteria. An equivalent electrical circuit model has also been proposed to explain the sensing mechanism. As small concentration as 102 CFU mL−1 of E. coli O157:H7 were successfully detected on the Au/PANI/Glu/antibody sensor with the upper detection limit of 107 CFU mL−1. The specificity of the sensor has been tested by comparing with two other strains of similar bacteria and found to be satisfactory. The mechanism of the detection is very simple and rapid, giving it a major advantage over DNA based techniques and other secondary antibody based labeled methods.