A label-free electrochemical biosensor for microRNA detection based on catalytic hairpin assembly and in situ formation of molybdophosphate.

A label-free electrochemical biosensor for sensitive detection of miRNA-155 was presented by coupling enzyme-catalyzed in situ generation of electronic mediator for signal introduction with catalytic hairpin assembly (CHA) induced target recycling amplification strategy. In this work, alkaline phosphatase (ALP) was adopted to hydrolyze inactive substrate 1-naphthyl phosphate (NPP) to produce phosphate ion (PO43-), which could further react with acidic molybdate to form abundant molybdophosphate anion (PMo12O403-) on the surface of electrode. The produced PMo12O403- could directly generate a strong and stable electrochemical signal for quantitative detection of targets. In addition, CHA induced the cyclic reuse of the target was also employed as an effective strategy for improving the sensitivity of biosensor. This electrochemical method for miRNA-155 detection had achieved a good linear relationship ranging from 10fM to 1nM with a detection limit of 1.64fM. With this assay successfully applied in tumor cell lysates, it holds great potential for early cancer diagnosis by employing miRNA as the effective biomarker.