Mesoporous silica-mediated controllable electrochemiluminescence quenching for immunosensor with simplicity, sensitivity and tunable detection range.

Straightforward and accurate measurement of medical biomarkers is of essential importance in clinical diagnostics and treatments. However, the major challenge is the diversity in dynamic range of different biomarkers ranging from pg mL-1 to µg mL-1 in various body fluids and tissues among patients. Here, we develop a mesoporous silica (MS)-mediated controllable electrochemiluminescence (ECL) quenching of immunosensor that allows accurate immunoassays with simplicity, sensitivity and tunable sensing range. MS is employed to enhance the sensitivity and tune ECL quenching to broaden the detection range just by altering luminophore (Ru(bpy)32+) and coreactant (DBAE) concentration without additional modifications. The immunoassay is followed: homogeneous sandwich immunoreaction, magnetic separation, and ECL quenching detection. As a proof-of-concept, simple and sensitive detection of IgG is achieved ranging from pg mL-1 to µg mL-1, and applications of the strategy are extended by the combination of ECL immunosensor with commercial ELISA kit. This study will not only be expected to serve as a new avenue for the assay of physiological and clinical implications of immunological biomarkers, but also benefit a wide range of applications that require a tunable detection range and ultrahigh sensitivity.

Quenching of the electrochemiluminescence of RU-complex tagged shared-stem hairpin probes by graphene oxide and its application to quantitative turn-on detection of DNA.

Efficient and stable quenching of electrochemiluminescence (ECL) of tris(2,2'-bipyridine)-ruthenium(II) (Ru(bpy)3(2+))/tri-n-propylamine (TPrA) system by graphene oxide (GO) at the glassy carbon electrode (GCE) was reported. For figuring out the possible reasons of the quenching mechanism, the electrochemical and ECL performance of GO, different reduction degree of reduced graphene oxide (RGOs) and polymer wrapped GO modified GCEs were systematacially investigated. The results demonstrated that the oxygen-containing groups and poor electrical conductivity of GO, along with the distance between GO and Ru(bpy)3(2+) was suggested as the reasons for quenching ECL. On the basis of this essential quenching mechanism, a novel "signal on" ECL DNA biosensor for ultrasensitive detection of specific DNA sequence was constructed by self-assembling the ECL probe of thiolated shared-stem hairpin DNA (SH-DNA) tagged with Ru complex (Ru(bpy)3(2+) derivatives) on the surface of GO/gold nanoparticles (AuNPs) modified GCE. The ECL probe sequences have their ECL signal efficiently quenched when they are self-assembled on the surface of GO unless they hybridizes with their target DNA (t-DNA) sequence. The designed ECL biosensor exhibited excellent stability and reproducibility, outstanding selectivity, and an extremely sensitive response to t-DNA in a wide linear range of 100 aM-10 pM with a low detection limit of 65 aM. Our findings and the design of biosensing switch would open a new avenue in the application of GO based ECL quenching strategy for ultrasensitive bioassays.