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In this work, a label-free electrochemical apta-nanosensor was fabricated on a single gold nanodisk electrode (AuNDE) for thrombin sensing with high sensitivity via a novel signal amplification strategy. This recognition platform was fabricated via self-assembly of helper DNA (HP-DNA), thrombin-binding aptamer (TBA) and gold nanoparticle (AuNP)-DNA complexes to form a sandwich structure on the AuNDE surface. A novel signal amplification strategy via designed AuNP-DNA complexes was introduced using Ru(NH3)63+ as the signal reporter based on the electrostatic interaction. In the presence of thrombin, the strong interaction between the TBA and target led to the dissociation of sandwich DNA complexes from the AuNDE, which resulted in the reduction current of Ru(NH3)63+. This proposed sensing platform showed a wide detection range of 0.1 pM–5 nM and a low detection limit of 0.02 pM. Considering the small overall dimensions and high sensitivity, this nanosensor can be potentially applied for bioanalysis in living biosystems. [ABSTRACT FROM AUTHOR]

A new approach for the sensitive and selective sensing of a protein has been developed. Cytochrome c could quench the fluorescence of a fluorophore labeled aptamer efficiently. The specific binding between the aptamer and the target protein resulted in a turn-on emission signal, which could be used for protein quantification. [ABSTRACT FROM AUTHOR]