Coreactant-Free Dual Amplified Electrochemiluminescent Biosensor Based on Conjugated Polymer Dots for the Ultrasensitive Detection of MicroRNA

Generally, electrochemiluminescence (ECL) assays are performed in the presence of a coreactant. The addition of the coreactant in the detection solution would make the ECL system lack sufficient stability. In the case of dissolved oxygen as the coreactant, the unknown concentration of dissolved O2 would result in an inevitable error and a lack of reproducibility in detection. A coreactant-free ECL assay could overcome the above shortcomings and thus is an ideal choice. In this work, a coreactant-free dual amplified ECL strategy was constructed for ultrasensitive detection of microRNA (miRNA). Here, target-catalyzed hairpin assembly and enzyme-triggered DNA walker recycling amplification were integrated to achieve dual signal amplification. Carboxyl-functionalized poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1′-3}-thiadiazole)] (PFBT-COOH) dots were used as luminophores, which displayed prominent ECL performance without adding any coreactants and removing the dissolved O2. As a result, the detection of miRNA was achieved, and the linear range was from 10 aM to 5 pM, and the detection limit was low to 3.3 aM. Meanwhile, the practicability of our biosensor was investigated by analyzing the expression of miRNA in cell lysates. The PFBT-COOH dots provided a great platform for constructing coreactant-free ECL biosensors and expanded the application of conjugated polymer dots in clinical analysis.