An ultrasensitive electrochemiluminescence biosensor for detection of MicroRNA by in-situ electrochemically generated copper nanoclusters as luminophore and TiO2 as coreaction accelerator

Herein, we constructed an ultrasensitive electrochemiluminescence (ECL) biosensor for detecting microRNA-21 (miR-21) based on in-situ generation of copper nanoclusters (Cu NCs) as luminophore and titanium dioxide (TiO2) as coreaction accelerator. First, numerous AT-rich double-stranded DNA (dsDNA) was produced from the conversion of a small amount of target miR-21 via the combination of exonuclease III (Exo III)-assisted amplification and hybridization chain reaction (HCR), which could reduce the aggregation-caused self-etching effect of Cu NCs and improve the emitting of Cu NCs. Simultaneously, the introduction of TiO2 in the sensing interface not just acted as the immobilizer of dsDNA-stabilized Cu NCs, more than acted as the coreaction accelerator to accelerate the reduction of the coreaction reagent (S2O82−) for significantly enhancing the ECL efficiency of Cu NCs. The biosensor showed an excellent linear relationship in the concentration range from 100 aM to 100 pM with the detection limit of 19.05 aM Impressively, the strategy not only opened up a novel and efficient preparation method for the Cu NCs, but expanded the application of Cu NCs in ultrasensitive biodetection owing to the addition of coreaction accelerator.