Ultrasensitive Ratiometric Homogeneous Electrochemical MicroRNA Biosensing via Target-Triggered Ru(III) Release and Redox Recycling

2017 
A new label-free and enzyme-free ratiometric homogeneous electrochemical microRNA biosensing platform was constructed via target-triggered Ru(III) release and redox recycling. To design the effective ratiometric dual-signal strategy, [Ru(NH3)6]3+ (Ru(III)), as one of the electroactive probes, was ingeniously entrapped in the pores of the positively charged mesoporous silica nanoparticle (PMSN), and another electroactive probe, [Fe(CN)6]3– (Fe(III)), was selected to facilitate Ru(III) redox recycling due to its distinctly separated reduction potential and different redox properties. Owing to the liberation of the formed RNA–ssDNA complex from PMSN, the target miRNA triggered the Ru(III) release and was quickly electroreduced to Ru(II), and then, the in-site-generated Ru(II) could be chemically oxidized back to Ru(III) by Fe(III). Thus, with the release of Ru(III) and the consumption of Fe(III), a significant enhancement for the ratio of electroreduction current [Ru(NH3)6]3+ over [Fe(CN)6]3– (IRu(III)/IFe(I...
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