A novel PEC biosensor based on dual SPR induced fluorescence and electron transfer co-quenching

The signal feedback of single-path energy transfer limited the detection accuracy of photoelectrochemical (PEC) biosensing. In this work, a superposed signal quenching strategy is employed, utilizing exciton-plasmon interactions (EPI) and plasmon-induced hot electron transfer (PHET) to detect miRNA-122, which plays a critical role in liver metabolism and gene regulation. Specifically, miRNA-122-modified Ag@Au core-shell nanoparticles are selectively immobilized onto complementary DNA-functionalized TiO 2 /CdS nanoflowers via base pairing and are constrained by the formed hybridized duplex at a distance around 10 nm from the substrate. Due to the energy overlap between the surface plasmon resonances (SPR) of Ag@Au and the absorption/emission spectra of TiO 2 /CdS, both fluorescence and electron transfer of the substrate are quenched through the combined effects of EPI and PHET. In addition, with the injection of counter current induced by dual SPR of the probes, a significant attenuation of photocurrent signal of the sensor is ultimately generated. Compared to the simple EPI effect between the substrate and miRNA-122/Au probes, this approach extends the attenuation of photocurrent by 3.7 times and achieves a limit of detection of 30 aM, demonstrating excellent analytical performance across a wide linear range (100 aM–100 pM). Furthermore, the enhancement of energy transfer efficiency by dual SPR is further elucidated through finite difference time domain simulations. This superposed signal quenching strategy significantly strengthens the interaction between the probes and the substrate, offering an innovative approach to PEC biosensing.