An ultrasensitive and selective electrochemical biosensor for Escherichia coli based on bacteria-imprinted polydopamine and a magnetic nanocomposite modifier.

This study developed an electrochemical biosensor utilizing a polydopamine film for the highly selective, ultrasensitive, and efficient determination of E. coli. A nanocomposite containing a magnetic graphene oxide-ionic liquid-palladium (MGO-IL-Pd) was synthesized and used as a chemical modifier to create a modified glassy carbon electrode (MGCE). Subsequently, dopamine was deposited on the GCE as a monomer during the electropolymerization process to prepare a bacteria imprinted polymer (BIP). After removing the E. coli as a template, the MGCE was employed for detecting the bacteria. The electrochemical performance of the BIP-based sensor was studied through square wave voltammetry (SWV) and cyclic voltammetry (CV). When E. coli was introduced, a significant current shift was observed, indicating bacterial entry into the BIPs' cavities. The biosensor successfully detected E. coli over a wide concentration range of 5.0 to 1.0 × 10⁷ CFU/mL, with a low detection limit of 1.5 CFU/mL. The biosensor's performance was compared to a non-bacteria imprinted polymer (NBIP) control, revealing a significant synergistic enhancement in detection signal due to the selective BIP cavities. Under optimum conditions, the sensor can be effectively applied to determine E. coli in human urine and serum samples with high precision and excellent recovery percentages.