Abstract
MicroRNAs (miRNAs), a kind of important biomarker, are traced and quantitatively detected in early clinical analysis. An ultrasensitive photoelectrochemical (PEC) sensing platform was constructed for microRNA 141 (miR-141) detection based on target triggered DNA walker amplification and silver nanoparticle assisted cation exchange. In this protocol, DNA walker was made of assembled DNA structure on the surface of gold nanoparticles (AuNPs), which powered by target to generate intermediate DNA. After hybridization and endonuclease digestion, the intermediate DNA was converted to numerous silver ions through the T7 exonuclease-aided recycling and acidolysis. Then, the released silver ions were introduced to CdSe QDs and initiated the ion exchange reaction on the electrode, resulting in largely change of PEC signal. The CdSe QDs/TiO2 composites with high photocatalytic activity were employed as PEC substrate. The photocurrent was decreased after ion exchange reaction. Through introducing amazing signal amplification strategy, the developed PEC “on-off” biosensor permitted a detection limit down to 3.0 aM for miR-141, and with a linear range from 1.0 × 10−17 to ×10-13 M.
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