A highly sensitive electrochemical IFN-gamma aptasensor based on a hierarchical graphene/AuNPs electrode interface with a dual enzyme-assisted amplification strategy

In this work, we have developed a new electrochemical aptasensor for IFN-gamma assay, based on a hierarchical graphene/AuNPs modified electrode coupled with a dual enzyme-assisted signal amplification strategy. The graphene/AuNPs modified electrode with a large specific area, high conductivity, excellent stability and biocompatibility was used for the immobilization of plentiful duplex DNA strands of capture probes and IFN-gamma aptamers. In the presence of IFN-gamma , hybridized aptamers were released from the electrode surface due to the formation of aptamer/IFN-gamma complexes. Meanwhile, aptamers were digested with RecJf exonuclease and IFN-gamma was available for target recycling, creating numerous free capture probes on the electrode surface. Then the hybridization chain reaction was initiated with the help of linker probes and biotin-labeled reporter probes. Thus cascade duplex DNA polymers were produced on the electrode surface, providing lots of binding sites for streptavidin-alkaline phosphatase to generate robust enzyme-catalyzed signals. Due to this dual enzyme-assisted amplification strategy, the prepared aptasensor exhibited a wide linear range from 5 pM-5 nM with an ultralow detection limit of 2 pM (S/N = 3). Besides, the aptasensor showed an excellent selectivity, satisfactory reproducibility and stability, and a great potential in serum analysis. Importantly, the versatility of the designed sensing strategy makes it easily extended for analyzing other biomolecules.