A Dual-Recognition Electrochemical Sensor Using Bacteria-Imprinted Polymer and Concanavalin A for Sensitive and Selective Detection of Escherichia coli O157:H7

The accurate detection and quantification of pathogenic bacteria is crucial for ensuring public health. In this work, we propose a sensitive and selective sandwich electrochemical sensor for detecting <i>Escherichia coli</i> O157:H7 (<i>E. coli</i> O157:H7). The sensor employs a dual-recognition strategy that combines a bacteria-imprinted polymer (BIP) and concanavalin A (ConA). The BIP is formed in situ on the electrode surface as the capture probe, while gold nanoparticles co-functionalized with ConA and the electroactive molecule 6-(ferrocenyl)hexanethiol (Au@Fc-ConA) serve as the signaling probe. When <i>E. coli</i> O157:H7 is present, the bacteria are selectively captured by the BIP. The captured bacteria interact with Au@Fc-ConA through ConA's sugar-binding properties, triggering Fc oxidation and generating a current proportional to the bacterial concentration. The sensor exhibits a linear detection range of 10¹-10⁵ CFU mL^-1 and a low detection limit of 10 CFU mL^-1. Additionally, it demonstrates high sensitivity in complex milk samples, detecting <i>E. coli</i> O157:H7 at concentrations as low as 10 CFU mL^-1, with recoveries ranging from 94.16% to 110.6%. Even in the presence of a 100-fold higher concentration of <i>E. coli</i> O6, the sensor effectively distinguishes <i>E. coli</i> O157:H7 from it. Moreover, it exhibits high reproducibility with a relative standard deviation of 2%. This study proposes a unique dual recognition strategy that combines simplicity and high performance. This method enables the selective detection of <i>E. coli</i> O157:H7 in real samples, providing a promising tool for food safety monitoring.