Glucometer-based electrochemical biosensor for determination of microRNA (let-7a) using magnetic-assisted extraction and supersandwich signal amplification.

A sensitive and portable biosensor is proposed for simple detection of microRNAs based on a supersandwich hybridization signal amplification strategy and a glucometer transducer. The presence of a target microRNA triggers the cascading hybridization chain reaction to create long supersandwich assemblies containing multiple biotin-labelled DNA probes. Then, large amounts of biotin-modified invertase signal molecules can attach to the supersandwich assemblies to generate an amplified signal for the glucometer readout. With such supersandwich format, a single target microRNA can introduce many biotin-invertase signal molecules, resulting in a one-to-multiple amplification effect. Thus, the accurate quantification of microRNAs can be achieved in a simple detection fashion without the requirement of expensive or precise instrumentation. The linear range of the biosensor for microRNA was from 0.05 to 100 nM with a detection limit of 48 pM. The proposed biosensor can discriminate the target microRNA from its family members with high selectivity and can be successfully applied to the detection of target microRNA spiked in serum samples with a good recovery (96.0-108.0%). Therefore, the proposed biosensor is expected to provide more information for early and accurate cancer diagnosis.