Impedimetric biosensor based on bimetallic AgPt nanoparticle-decorated carbon nanotubes as highly conductive film surface

In the present study, an ultrasensitive impedimetric aptasensor for the quantitative detection of diclofenac (DCF) was fabricated based on a novel signal amplification strategy. As a transducer material, acid-oxidized carbon nanotubes (CNT-COOH) and Pt and Ag nanoparticles (PtAgNPs) were used for promoting electron transfer between the electroactive probe and electrode. It is worth noting that the proposed nanocomposite revealed significant properties through the synergistic effects of the nanocomponent materials. In this strategy, aminated capture probe (ssDNA1) and DCF aptamer (ssDNA2) as a detection probe were attached at the surface of a modified electrode via the formation of covalent amide bond and hybridization, respectively. The proposed nanoaptasensor combined the advantages of the deposition of neatly arranged PtAgNPs and the covalent attachment of the capture probe at the surface of the modified electrode. The change of interfacial charge transfer resistance (Rct) recorded by [Fe(CN)6]3−/4− as a redox probe was monitored for sensitive quantitative detection of DCF. Addition of DCF resulted in the increase of the value of Rct due to suppression of the electron exchange between [Fe(CN)6]3−/4− in the surface layer. Under optimized conditions, the proposed aptasensor showed good detection range from 10 pM to 800 nM with unprecedented detection limit of 2.8 pM. More importantly, the developed strategy showed highly sensitive responses to DCF, responses that are more sensitive than those of previously reported methods.