Surface plasmon-enhanced electrochemiluminescence (SPEECL) with excellent sensitivity and simplicity has attracted increasing attention. In this work, we reported a novel SPEECL with DNA templated silver nanoclusters (DNA-AgNCs) as ECL emitters and gold nanoparticles (AuNPs) as localized surface plasmon resonance (LSPR) source. The SPEECL with DNA-AgNCs as ECL luminophores possessed low toxicity and avoided the labeling process, which is favorable for its further sensing application. In addition, by investigation of the SPEECL under different distances between DNA-AgNCs and AuNPs, it was demonstrated that the SPEECL was distance dependent. Meanwhile, the SPEECL intensity changed with the sizes and interdistance of AuNPs under different electrodeposition time. Furthermore, by the combination of a cyclic amplification process with enzyme-free catalytic hairpin DNA, a sensitive SPEECL biosensor was proposed for the detection of microRNA (miRNA-21) successfully with a wide linear range from 1 aM to 10 4 fM and a relatively low detection limit of 0.96 aM, which was applied in the detection of miRNA-21 in real samples with satisfying results. This novel, simple, sensitive, and selective SPEECL with label-free and low-toxic ECL emitters displayed a great potential for bioassay application.

An effective and precise electrochemiluminescence resonance energy transfer (ECL-RET), including the efficient regulation over the proximity of a donor and an acceptor and the reliable stimuli responsive as well as the avoidance of undesirable probes leakage, etc., is significant for the development of an accurate and sensitive ECL detection method; yet, the current literature in documentation involves only a limited range of such ECL-RET systems. Herein, we propose an ECL-RET strategy with dually quenched ultralow background signals and a dual-stimuli responsive, accurate signal output for the ultrasensitive and reliable detection of anatoxin-a (ATX-a). The dual quenching is accomplished by an integrated ECL-RET probe of metal organic frameworks (MOFs) encapsulated into Ru­(bpy)3 2+ (Ru-MOF) (donor) coated with silver nanoparticles (AgNPs) shell (acceptor 1) and close proximity with DNA-ferrocene (Fc) (acceptor 2). Multistimuli responsive DNAzyme facilitated the accurate signal switch by both target ATX-a and hydrogen peroxide (H2O2). Because of the specific recognition of the aptamer toward ATX-a, an intricate design of the DNA sequence enabled the exposure of the Ag+-dependent DNAzyme sequence and H2O2 in situ generated Ag+ triggering a catalytic cleavage reaction to freely release the two ECL-RET energy acceptors, thus switching the ECL signal significantly and achieving ultrasensitive detection. It is noteworthy that AgNPs are key in this ECL-RET strategy, serving both as the gate-keepers for avoiding ECL probes leakage and also the ECL energy acceptors, and mostly importantly serving as the redox substrate for the subsequent DNAzyme catalytic signal switch. The proposed ECL-RET aptasensor for ATX-a detection displayed splendid monitoring performance with a quite low detection limit of 0.00034 mg mL–1. This sensor not only led to the development of a dual-quenching ECL-RET system but also provided meaningful multistimuli responsive ECL biosensing platform construction, which shows a promising application prospect in complicated sample analysis.

Since fluorescence assays with high sensitivity for organophosphorus pesticides (OPs) are urgently required to protect the ecosystem and prevent disease, an environmentally friendly and label-free fluorescent probe is desirable.