Electropolymerization of Stable Leucoemeraldine Base Polyaniline Film and Application for Quantitative Detection of Escherichia coli O157:H7

Abstract

A stable leucoemeraldine base polyaniline (PANI) has been optimally electrodeposited on a bare screen-printed carbon electrode (SPCE) using a potentiostatic method and a nonenzymatic electrochemical immunosensor for quantitative detection of Escherichia coli O157:H7 (E. coli O157:H7) fabricated. The stability, electroactivity, and surface morphology of the PANI film were studied by cyclic voltammetry and scanning electron microscopy. The PANI film formed by the potentiostatic method was firmly attached to the SPCE, being more stable than PANI film electrodeposited by a cyclic voltammetric method. Gold nanoparticles (AuNPs) were linked to the PANI film and used as a connector to an antibody against E. coli O157:H7 (Ab). E. coli O157:H7 was quantitatively detected by differential pulse voltammetry based on the PANI/Ab-modified SPCE. The principle of this quantitative method is based on a prominent decrease of the current after specific binding to E. coli O157:H7. Under the optimized conditions, a linear relationship between the peak current change (ΔI) and the logarithm of the E. coli O157:H7 concentration was obtained in the range from 4.0 × 104 colony-forming units (CFU)/mL to 4.0 × 109 CFU/mL, with limit of detection (LOD) of 7.98 × 103 CFU/mL at signal-to-noise ratio (S/N) of 3. The immunoassay exhibited acceptable specificity, reproducibility, and stability for detection of E. coli O157:H7. In future work, the proposed approach could be used to prepare stable films which can withstand sonication and strong acid.