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Color-switch electrochemiluminescence (ECL) sensing platform based on a dual-bipolar electrode (D-BPE) is reported in this work. The D-BPE was composed of a cathode filled with buffer and two anodes filled with [Ru(bpy) 3 ]2+-TPrA and luminol-H 2 O 2 solutions, respectively. Both anodes were modified with capture DNA and served as ECL reporting platforms. After introducing ferrocene-labeled aptamer (Fc-aptamer) on both anodes, the ECL emission signal of the [Ru(bpy) 3 ]2+ was difficult to be observed (anode 1), while luminol emitted a strong and visible ECL signal (anode 2). Ferrocene (Fc) did not only prevent the oxidation of [Ru(bpy) 3 ]2+ due to its lower oxidation potential, its oxidation product Fc+ also quenched the [Ru(bpy) 3 ]2+ ECL through efficient energy transfer. For luminol, Fc+ catalyzes the accelerated formation of the excited-state of the luminol anion radical, which leads to the enhancement of the luminol ECL. In the presence of food-borne pathogens, the aptamer was assembled with them, leading to the leaving of Fc from the surface of the D-BPE anodes. The ECL intensity of [Ru(bpy) 3 ]2+ was enlarged, meanwhile, the blue emission signal of luminol became weakened. By self-calibrating the ratio of the two signals, 1–106 CFU mL−1 food-borne pathogenic bacteria can be sensitively detected with a detection limit of 1 CFU mL−1. Ingeniously, the color-switch biosensor can be used to detect S. aureus , E. coli and S. typhimurium by assembling the corresponding aptamers onto the D-BPE anodes. [ABSTRACT FROM AUTHOR]

After discovery of electron transfer from bacteria, most bacteria known to be electrochemically active are utilized as a self-regenerable catalyst at the anode of microbial fuel cells (MFCs). However, the reverse phenomenon, cathodic catalysts is not so widely researched. This present study demonstrated that E. coli O157:H7 was electrochemically active, and it was able to catalyze oxygen reduction at the cathode of bipolar electrode (BPE). Applying a constant potential to the BPE, E. coli O157:H7 can catalyze electrochemical reduction of O 2 , decrease the overpotential of O 2 reduction at the cathode, which in turn generates an electrochemiluminescence (ECL) reporting intensity change at the anode. Significantly, a majority of food matrix does not exhibit catalytic activity for electrochemical reduction of O 2. Meanwhile, due to the physically separation of two poles of closed BPE, complex food matrix at the cathode does not interfere with the ECL reaction at the anode. Therefore, the effect of food matrix is negligible when measuring E. coli O157:H7 levels in food. A low detection limit of 10 CFU mL−1 E. coli O157:H7 could be identified within 1 h. Thus, biocathodes reducing oxygen in BPE-ECL system has shown excellent characteristics in the field of rapid detection of electroactive bacteria in food. [ABSTRACT FROM AUTHOR]