Detection of <i>E. coli</i> O157:H7 using a molecularly imprinted bacterial bipolar electrode and an Au@metal–organic framework

A molecularly imprinted bacterial bipolar electrode (BPE) sensor combined with an Au@metal-organic framework (Au@MOF) was developed for <i>E. coli</i> O157:H7 detection. Firstly, dopamine (DA) was mixed with <i>E. coli</i> O157:H7 through an electropolymerization process to form a polymer film on the BPE cathode. After bacteria removal, the molecularly imprinted bacterial polydopamine (PDA) film remained on the cathode, exhibiting high specificity for bacterial recognition and binding. Secondly, the <i>E. coli</i> O157:H7 aptamer was integrated into the Au@MOF surface by Au-SH covalent bonds. Then, <i>E. coli</i> O157:H7 was present at the cathode, and the Au@MOF was assembled onto the electrode surface through the specific binding of aptamers to <i>E. coli</i> O157:H7. Finally, a 3,3',5,5'-tetramethylbenzidine/H₂O₂ (TMB/H₂O₂) solution was added to the cathode. Au@MOF exhibited peroxidase-like activity and could catalyze the reduction reaction of the TMB/H₂O₂ system. Due to the electrical neutrality principle of the BPE, the oxidation reaction of the [Ru(bpy)₃]²⁺/tripropylamine ([Ru(bpy)₃]²⁺/TPA) system occurred at the anode, generating a distinct electrochemiluminescence (ECL) signal. The sensor detected <i>E. coli</i> O157:H7 within a concentration range of 1 to 10⁶ CFU mL^-1, with a detection limit of 1 CFU mL^-1, demonstrating high selectivity and sensitivity. This BPE platform, integrating molecular imprinting and Au@MOF-assisted oxygen reduction, shows significant potential for bacteria detection in various applications.