Regulation of Ru(bpy)32+ Electrochemiluminescence Based on Distance-Dependent Electron Transfer of Ferrocene for Dual-Signal Readout Detection of Aflatoxin B1 with High Sensitivity

Ferrocene (Fc) is a common quencher of Ru(bpy)(3)(2+) luminescence. However, interactions between Fc and Ru(bpy)(3)(2+) can be extremely complicated. In this work, we reported the first use of Fc to regulate the electrochemiluminescence (ECL) of Ru(bpy)(3)(2+) by tuning the length of the DNA sequence between Fc and the luminophore of nitrogen-doped graphene quantum dots-Ru(bpy)(3)(2+)-doped silica nanoparticles (SiO2@Ru-NGQDs). The ECL of SiO2@Ru-NGQDs was depressed when the distance between Ru(bpy)(3)(2+) and Fc was less than 8 nm; a stronger ECL was observed when the distance was more than 12 nm. The switching of the ECL of Ru(bpy)(3)(2+) by Fc was attributed to the electron transfer mechanism, in which Fc participated in the redox of Ru(bpy)(3)(2+) for signal-off ECL; this favored electron transfer at the electrode fabricated with an Fc-labeled aptamer (Fc-apt) and SiO2@Ru-NGQDs for signal-on ECL depending on the length of the DNA sequence. Here, a dual-signal readout aptasensor for aflatoxin B1 (AFB1) detection was developed via the enhanced ECL of SiO2@Ru-NGQDs by Fc-apt. The redox currents of Fc and the ECL of Ru(bpy)(3)(2+) were simultaneously collected as yardsticks, and both decreased with higher concentrations of AFB1. The aptasensor allowed linear ranges of 3 x 10(-5) to 1 x 10(2) ng mL(-1) for ECL mode and 1 x 10(-3) to 3 x 10(3) ng mL(-1) for electrochemical mode. Our work provides insight into the interactions between Fc and Ru(bpy)(3)(2+). The dual-signal readout strategy is a potential platform for the versatile design of aptasensors.

Automated summary

The study reported a novel method for regulating the electrochemiluminescence of Ru(bpy)(3)(2+) by tuning the DNA sequence length, demonstrating the role of Fc in controlling the ECL of SiO2@Ru-NGQDs. A dual-signal readout aptasensor was developed using Fc-apt for AFB1 detection, showing potential for versatile design of aptasensors.