Sensitive sandwich-type electrochemical biosensor with gold nanoparticles and enzyme catalytic amplification for specific detection of MicroRNA-26a

A high sensitive sandwich-type electrochemical biosensor utilizing capture probe (CP), target probe (TP), and signal probe (SP) was first developed for specific detection of microRNA-26a (miR-26a), a biomarker with diagnostic significance for atherosclerosis. In general, gold nanoparticles (Au NPs) were electrodeposited on to a glassy carbon electrode to enhance conductivity, followed by immobilization of 5′-thiolated CP through a gold-sulfur bond. Subsequently, the modified electrode was hybridized with the mixture of miR-26a and 3′-biotin-tagged SP in sequence. Furthermore, horseradish peroxidase-streptavidin (HRP) with potent reducing capability was finally grafted on the SP via the strong affinity between biotin and streptavidin. Additionally, the fabrication process of the miR-26a biosensor was thoroughly investigated. Based on the dual amplification mechanism facilitated by Au NPs and HRP-catalytic activity, the proposed biosensor demonstrated outstanding electrochemical properties, including good reproducibility and stability, as well as high sensitivity for miR-26a detection down to 0.88 fM with a linear range from 1 fM to 1 nM. The biosensor also displayed exact specificity, which could discriminate miR-26a from a range of base mismatched microRNAs. Moreover, it was successfully applied to the determination of miR-26a in serum samples. In conclusion, given the excellent analytical performance, this biosensor shows promise for potential use in clinical diagnostics for atherosclerosis.