Bipolar Electrochemiluminescence Detection of Ampicillin Resistance Genes via HRCA-Mediated Precipitation-Induced Conductivity Modulation

Antibiotic resistance genes pose a significant threat to public health, highlighting the urgent need for rapid and sensitive detection methods. In this study, a bipolar electrochemiluminescence (BPE-ECL) sensing strategy was developed for detecting ampicillin resistance genes (ARG_AMP) based on conductivity variation induced by the precipitation reaction from hyperbranched rolling circle amplification (HRCA). Initiated by ARG_AMP, HRCA generates ultralong DNA chains with pyrophosphate as a byproduct. Since solution conductivity is ion-dependent, the subsequent pyrophosphate-magnesium precipitation consumes free magnesium ions, significantly altering the solution conductivity within the sensing cell. This change directly modulates ECL intensity in the reporting cell due to the charge balance of BPE. The proposed BPE-ECL biosensing platform demonstrates the selective and sensitive detection of ARG_AMP in the range of 1 pM to 1 μM, with a low limit of detection (LOD) of 0.73 pM. Furthermore, the platform was successfully applied to detect ARG_AMP extracted from Escherichia coli plasmid, with recovery tests demonstrating its potential application in real environmental samples.