Ultrasensitive Electrochemiluminescence Biosensor Based on 2D Co 3 O 4 Nanosheets as a Coreaction Accelerator and Highly Ordered Rolling DNA Nanomachine as a Signal Amplifier for the Detection of MicroRNA.

A novel ultrasensitive electrochemiluminescence (ECL) biosensor was constructed using two-dimensional (2D) Co 3 O 4 nanosheets as a novel coreaction accelerator of the luminol/H 2 O 2 ECL system for the detection of microRNA-21 (miRNA-21). Impressively, coreaction accelerator 2D Co 3 O 4 nanosheets with effective mutual conversion of the Co 2+ /Co 3+ redox pair and abundant active sites could promote the decomposition of coreactant H 2 O 2 to generate more superoxide anion radicals (O 2 •- ), which reacted with luminol for significantly enhancing ECL signals. Furthermore, the trace target miRNA-21 was transformed into a large number of G-wires through the strand displacement amplification (SDA) process to self-assemble the highly ordered rolling DNA nanomachine (HORDNM), which could tremendously improve the detection sensitivity of biosensors. Hence, on the basis of the novel luminol/H 2 O 2 /2D Co 3 O 4 nanosheet ternary ECL system, the biosensor implemented ultrasensitive detection of miRNA-21 with a detection limit as low as 4.1 aM, which provided a novel strategy to design an effective ECL emitter for ultrasensitive detection of biomarkers for early disease diagnosis.