Label-free impedimetric aptasensor based on PEDOT‑gold nanocomposite for the selective detection of Escherichia coli...

In this study, a label-free impedimetric aptasensor employing a glassy carbon electrode (GCE) modified with a nanocomposite of poly (3,4-ethylenedioxythiophene) and gold nanoparticles was developed. Following surface preparation, specific aptamer strands were covalently immobilized onto the electrode to enable the selective recognition of Escherichia coli O157:H7. Under optimized conditions, the aptasensor exhibited a linear response range from 5 to 5 × 10⁷ CFU/mL and an impressive limit of detection of 1.3 CFU/mL. The structural and chemical properties of the nanocomposite were characterized using Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FE-SEM), and Energy Dispersive X-ray Spectroscopy (EDS) analyses. Among various electrochemical approaches, electrochemical impedance spectroscopy served as the primary technique to probe the interfacial behavior of the modified GCE, while differential pulse voltammetry provided complementary insights into charge-transfer dynamics. The proposed sensor offered remarkable sensitivity and selectivity, combined with low fabrication cost and straightforward preparation. Its performance was successfully validated with milk samples. This study establishes a robust framework for the development of impedimetric aptasensors based on nanocomposites integrating inorganic nanoparticles and conductive polymers. Owing to its straightforward fabrication and the inherently automatable nature of impedance-based microbiological analysis, the proposed biosensor holds significant promise for incorporation into industrial monitoring platforms and portable diagnostic systems.