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.