A sensitive and regenerative electrochemical immunosensor for quantitative detection of Escherichia coli O157:H7 based on stable polyaniline coated screen-printed carbon electrode and rGO-NR-Au@Pt

Abstract

A sensitive and quantitative sandwich electrochemical immunosensor was constructed for the detection of Escherichia coli O157:H7 (E. coli O157:H7) using immune gold@platinum nanoparticles (Au@Pt), neutral red (NR), reduced graphene oxide nanocomposite (rGO) and regenerative leucoemeraldine base polyaniline (PANI)/gold nanoparticles (AuNPs) modified screen-printed carbon electrode (SPCE). The batch production advantages of the SPCE were retained, its disposable characteristic was replaced by the possibility for reuse. The anti-E. coli O157:H7 monoclonal antibody (Ab₁) was automatically adsorbed on the SPCE-PANI-AuNPs platform through the amino and AuNPs interaction. rGO-NR-Au@Pt as the non-enzyme signal label can enhance the performance of the immunoassay for the catalytic reduction of H₂O₂ and amplify the current signal. All characterization steps were monitored by cyclic voltammetry (CV). Based on electrochemical detection of E. coli O157:H7, the linear range was from 8.9 × 10³ to 8.9 × 10⁹ CFU mL⁻¹, and limit of detection (LOD) was 2.84 × 10³ CFU mL⁻¹. To ensure that the immunosensor can be used repeatedly, ultrasound sonication was used to remove as many surface-bound antibodies as possible. This allows Ab₁ to bind to the SPCE-PANI-AuNPs again after the electrode was re-incubated with the antibody solution, and hence, the displacement assay can be repeated and the sensor reused. Furthermore, it was demonstrated that the microchips can be regenerated and reused at least 5 times.