Double bipolar electrode electrochemiluminescence color switch for food-borne pathogens detection

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-H₂O₂ 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.