A novel electrochemiluminescence biosensor for the detection of microRNAs based on a DNA functionalized nitrogen doped carbon quantum dots as signal enhancers.

An ultrasensitive electrochemiluminescence (ECL) biosensor for the detection of microRNA was developed based on nicking enzymes Nb.BbvCI mediated signal amplification (NESA). First, the hairpin probe1-N-CQDs with assistant probe and microRNA (miRNA) formed Y junction structure which was cleaved with the addition of nicking enzymes Nb.BbvCI to release miRNA and assistant probe. Subsequently, the released miRNA and assistant probe can initiate the next recycling process. The generation of numerous intermediate sequences nitrogen doped carbon quantum dots-DNA (N-CQDs-DNA) can further hybridize with hairpin probe2 immobilized on GO/Au composite modified electrode surface, the initial ECL intensity was enhanced. The ECL intensity would increase with increasing concentration of the target miRNA, and the sensitivity of biosensor would be promoted because of the efficient signal amplification of the target induced cycling reaction. The novel designed biosensor provided a highly sensitive and selective detection of miRNA-21 from 10 aM to10(4) fM with a relatively low detection limit of 10 aM. Thus, our strategy has a potential application in the clinical diagnosis.