A sensitive, label free electrochemical aptasensor for ATP detection

A sensitive, label free electrochemical aptasensor for small molecular detection has been developed in this work based on gold nanoparticles (AuNPs) amplification. This aptasensor was fabricated as a tertiary hybrid DNA–AuNPs system, which involved the anchored DNA (ADNA) immobilized on gold electrode, reporter DNA (RDNA) tethered with AuNPs and target-responsive DNA (TRDNA) linking ADNA and RDNA. Electrochemical signal is derived from chronocoulometric interrogation of [Ru(NH3)6]3+ (RuHex) that quantitatively binds to surface-confined DNA via electrostatic interaction. Using adenosine triphosphate (ATP) as a model analyte and ATP-binding aptamer as a model molecular reorganization element, the introduction of ATP triggers the structure switching of the TRDNA to form aptamer–ATP complex, which results in the dissociation of the RDNA capped AuNPs (RDNA–AuNPs) and release of abundant RuHex molecules trapped by RDNA–AuNPs. The incorporation of AuNPs in this strategy significantly enhances the sensitivity because of the amplification of electrochemical signal by the RDNA–AuNPs/RuHex system. Under optimized conditions, a wide linear dynamic range of 4 orders of magnitude (1 nM–10 μM) was reached with the minimum detectable concentration at sub-nanomolar level (0.2 nM). Those results demonstrate that our nanoparticles-based amplification strategy is feasible for ATP assay and presents a potential universal method for other small molecular aptasensors.