Parallel Bipolar Electrode Array Modified by Hetero-Charged Silica Nanochannels for Ratiometric Electrochemiluminescence Detection of Escherichia coli Lysed by T4 Phage

Development of user-friendly biosensors for bacterial detection remains a critical concern in public health. The bipolar electrode-based electrochemiluminescence (BPE-ECL) systems are distinguished by their inherent spatial separation of sensing and reporting functions, representing a promising approach for biosensor development. This work innovatively presents a parallel BPE-ECL biosensor, wherein the cathodes are interdigitally inserted and the anodes are functionalized with vertically ordered mesoporous silica films (VMSFs) bearing negative and positive charges, to achieve dual-channel ratiometric ECL detection. The infection of Escherichia coli (<i>E. coli</i>) by T4 phage induces host cell lysis, resulting in a significant increase in the surrounding conductivity. This conductivity alteration within the sensing cell of VMSFs/pBPE-ECL leads to a decrease in the ECL signal of Ru(bpy)₃²⁺/TPrA in detection channel 1 and an increase in the ECL signal of Luminol/H₂O₂ in detection channel 2 independently, due to the enhanced polarization of the BPEs and the nanoconfinement effects of hetero-charged silica nanochannels on the ECL luminophors. By using the ratio of ECL intensities (<i>I</i>_Lu/<i>I</i>_Ru) from the two detection channels, E. coli can be detected with improved accuracy and resistance to interference. This biosensing approach is operationally straightforward, avoiding complicated probe immobilization or modification, rendering it a user-friendly platform for bacterial detection. Moreover, by replacing the specific phage-bacteria lysis bioreaction, this biosensing platform could be used for various bacterial detections, highlighting its promising applications.