An ultrasensitive sensing platform for microRNA-155 based on H

A strong hydroxide (OH-)-dependent ECL emission of carboxyl functionalized-poly (9,9-di-n-octylfluorenyl-2,7-diyl) polymer dots (PFO Pdots) was observed at +1.25 V, which is significantly stronger than the emission at +1.95 V reported in previous work. Moreover, hydrogen peroxide (H2O2) can efficiently quench OH--dependent ECL emission of PFO Pdots. Based on this discovery, a signal "off-on" ECL biosensing platform for microRNA-155 (miRNA-155) was developed. Firstly, PFO Pdots were modified onto the electrode to capture DNA duplex track-locker. In the presence of H2O2 in the test solution, the ECL signal of PFO Pdots was quenched to obtain a signal-off state. Subsequently, the DNA walker produced through the target miRNA-155-triggered catalytic hairpin assembly (CHA) walked along the DNA duplex track-locker to output amounts of G-rich short chain, forming a hemin/G-quadruplex. With the consumption of H2O2 by hemin/G-quadruplex, the ECL signal would be restored to a signal-on state, thus achieving an ultrasensitive detection of miRNA-155. The detection limit was low as 12.2 aM. Furthermore, our proposed biosensor demonstrated a tremendous selectivity and admirable stability, and exhibited a satisfactory performance for determinating intracellular miRNA-155. The integration of excellent ECL performance of PFO Pdots without any exogenous species or dissolved O2 as co-reactant and a highly efficient quenching effect of H2O2 on such an ECL emission will provide an attractive ECL platform for bioanalysis and clinical diagnosis.