An amplified label-free electrochemical aptasensor of γ-interferon based on target-induced DNA strand transform of hairpin-to-linear conformation enabling simultaneous capture of redox probe and target.

In this work, a novel and signal-amplified label-free electrochemical aptasensor was developed and enabled efficient determination of γ-interferon (IFN-γ), based on target-induced DNA strand transform of hairpin-to-linear conformation combining with simultaneous capture of redox probe and target. Gold nanoparticles (AuNPs) were electrodeposited in the matrix of poly(amidoamine) dendrimer (PAMAM), followed by drop-casting addition on MoS2 nanosheets to prepare AuNPs- PAMAM/MoS2 composites. HS-terminated hairpin-DNA aptamer of IFN-γ was conjugated with AuNPs to prepare aptamer-AuNPs-PAMAM/MoS2 onto glassy carbon electrode (GCE), by using bovine serum albumin as the cross-linker and stabilizer. Methylene blue (MB) as a redox probe was absorbed on IFN-γ aptamer. In the presence of IFN-γ, MB electrochemical signal increased gradually. The preparation processes, mechanisms and optimal experiment conditions of aptamer- AuNPs-PAMAM/MoS2/MB/GCE sensing platform were studied by electron microscope imaging technologies, spectral curves and electrochemical measurements. There is a well plotting linear relationship between the peak current intensities of MB and IFN-γ contents in the range of 0.01-1000 pg mL-1, showing a low detection limit of 2 fg mL-1. Experimental results testified that the aptasensor had highly sensitive and selective responses toward IFN-γ, over potential interferents. In real biological samples, the aptasensor of IFN-γ had superior detection recoveries, indicating its high detection performance and feasibility for practicability.