Co-reactant-free electrochemiluminescence biosensor enabled by photoelectron transfer and DNA amplification for trace...

Ochratoxin A (OTA) is a mycotoxin contaminant that poses a significant threat to human health. It is a common naturally occurring contaminant toxin that is widely found in agricultural and food products worldwide. Therefore, there is an urgent need for simpler and more sensitive analytical methods to detect OTA in food.

In this study, a co-reactant-free annihilation electrochemiluminescence (ECL) biosensor was developed for the ultrasensitive detection of OTA. The emitter, Ru-Cu NCs@MOFs, was constructed by anchoring copper nanoclusters (Cu NCs) onto amino-functionalized metal-organic frameworks (NH₂-MOFs), followed by coordination with Ru(H₂dcbpy)₃²⁺. Density functional theory (DFT) and Tauc plot analysis revealed that the structure exhibited a narrowed bandgap, which promoted interfacial photoelectron transfer and facilitated the generation of excited Ru∗-Cu NCs@MOFs species. This is the first reported instance of Cu-to-Ru electron transfer in ECL systems, effectively mitigating ACQ and significantly enhancing luminescence efficiency. To further improve sensitivity, a cyclic DNA amplification mechanism was integrated into the biosensing interface, thereby amplifying the ECL response. The resulting biosensor exhibited a wide linear range from 1 pg/mL to 100 ng/mL and an ultralow detection limit of 0.47 pg/mL.

The OTA concentrations detected in actual samples using the ECL biosensor were consistent with the enzyme-linked immunosorbent assay (ELISA) results, confirming the effectiveness of the designed ECL biosensor in detecting OTA in actual samples. This work presents a highly sensitive ECL sensing strategy, offering strong potential for trace-level OTA monitoring in food safety analysis.