Gold-Polyaniline Supercapacitive Biosensor for Selective Detection of E. Coli DH 5α

Bacterial identification is challenging due to several problems, such as low sensitivity, poor selectivity, and the lack of quantitative methods. To address these obstacles, a gold nanoparticles (AuNPs)@Polyaniline (PANI)/Phage electrode was developed. The bacteriophage was immobilized on the AuNPs@PANI modified electrode, serving as an electrochemical biosensor of Escherichia coli (E. coli) DH5 $\alpha$ . In application, this biosensor can detect of E. coli DH5 $\alpha$ within a dynamic range of 10–107 CFUmL-1 with the detection limit of 1.0 CFUmL-1. Modified AuNPs@ PANI/Phage electrode exhibits a signal/noise ratio equal to 3.0, but only AuNPs@ PANI displayed 1.025 in [Fe(CN)6]3−/4− This biosensor selectively detected of E. coli DH5 $\alpha$ bacteria in the presence of comparable concentrations of different bacterial strains. In addition, the modified electrode exhibited supercapacitive behavior during electrochemical characterization and showed a high specific capacitance of 782.61 Fg-1 at 1.0 Ag-1 and 94.7% retention over 10 000 GCD cycles. Further analysis was conducted using galvanostatic charge-discharge to measure capacitance and self-discharge to assess capacity retention over time, and the Dunn method to analyze the charge storage mechanism within the electrode material. In conclusion, the developed nanostructure displayed dual electrochemical behavior as a supercapacitor and biosensor. This is the first reported PANI functionalized capacitive-controlled electrodes for bacterial detection. The fabrication and detection process for a single glass carbon electrode (GCE)/AuNPs@PANI pernigraniline salt (PANI-PS)/Phage/E. coli electrode requires ~90 min, with an estimated material cost of U.S. ${\$}$ 5.28 per electrode. Furthermore, smartphone-based testing confirmed portable, realtime detectionwith <1.5% deviation, indicating promise for multichannel clinical biosensing.