Combination of exciton-plasmon interaction and programmable DNA cyclic amplification for electrochemiluminescence/photoelectrochemical sensing of serotonin.

A novel dual-mode electrochemiluminescence (ECL)/photoelectrochemistry (PEC) biosensor was developed for sensitive serotonin detection. In this system, the PEC signal was produced by CdS quantum dots (QDs), while the ECL signal originated from L-Au NPs (luminol decorated Au nanoparticles), thereby avoiding the external interference and signal fluctuations that typically arose from using the same materials for both signals. The presence of target serotonin initiated the non-enzymatic toehold-mediated strand displacement reaction (TSDR) on magnetic bead (MB), which was followed by catalytic hairpin assembly (CHA) on the sensing interface, leading to the aggregation of many L-Au NPs. The strong exciton-plasmon interactions (EPI) induced the energy transfer between CdS QDs and Au NPs, causing the significant suppression of the photocurrent. In addition, this design assured that the ECL and PEC respond in opposing manners and that no background ECL signal was detected, thereby greatly improving the sensitivity of the biosensor. Ultimately, the biosensor demonstrated a broad linear range from 5 pM to 1 μM with a detection limit of 1.6 pM, and also could be used for the assay of serum and urine samples with satisfactory results. With the advantages of high sensitivity, selectivity, accuracy and signal stability, this sensing strategy was helpful for disease diagnosis and the fundamental research of neurotransmitters.