A Bipolar Electrode-Electrochemiluminescence Sensor for Sensitive Detection of Escherichia coli O157:H7 Based on Loop-Mediated Isothermal Amplification

Escherichia coli O157:H7 (E. coli O157:H7) is a foodborne pathogen with high pathogenicity and lethality, capable of producing substantial amounts of Vero toxin (VT), posing a significant threat to human health. Consequently, a platform based on the bipolar electrode-electrochemiluminescence (BPE-ECL) and loop-mediated isothermal amplification (LAMP) was constructed for the detection of E. coli O157:H7. Firstly, LAMP technology is utilized to efficiently obtain the amplified product (double-stranded DNA, dsDNA) of E. coli O157:H7. On the one hand, SYBR Green was added to the amplified product to detect E. coli O157:H7 by colorimetric determination. The concentration of 10 CFU mL⁻¹ E. coli O157:H7 can only obtain qualitative analysis, to determine the presence of the target bacteria. On the other hand, methylene blue (MB) molecules were embedded in the dsDNA through electrostatic interactions. Then, by dropwise adding the mixture onto the cathode of the BPE, the ECL signal of Ru(bpy)₃²⁺ onto the anode was generated. Specifically, the BPE-ECL sensor displayed superior sensitivity for E. coli O157:H7 with a detection limit of 10 CFU mL⁻¹ and a wide linear concentration range of 10¹–10⁶ CFU mL⁻¹. In summary, this sensor can effectively enhance the sensitivity and reliability of detection when compared to traditional colorimetric methods, and achieve qualitative and quantitative detection of E. coli O157:H7 by measuring the anode ECL signal of Ru(bpy)₃²⁺.