A label-free IFN-γ aptasensor based on target-triggered allosteric switching of aptamer beacon and streptavidin-inorganic hybrid composites.

A label-free electrochemical aptasensor was developed for the sensitive detection of interferon-gamma (IFN-γ). To do this, a diblock dual-aptamer allosteric hairpin (DDAH) was designed, followed by conjugation with gold nanoparticles (DDAH&AuNP). The presence of target destroyed the stable hairpin structure, and then the catalytic cleavage of DNAzymes removed the IFN-γ-binding molecules, triggering the allosteric switching from inactive hairpin to active streptavidin aptamer (A-DDAH&AuNP) in homogeneous system. Moreover, streptavidin-inorganic hybrid nanoflowers decorated with graphene composites (SFG) were synthesized and used as substrates to modify glassy carbon electrodes (SFG/GCE). SFG specifically bind to the A-DDAH&AuNP to realize high-efficient readout of signals. Under the optimal conditions and by using differential pulse stripping voltammetry (DPSV), the response peak currents increases linearly with the logarithm of the IFN-γ concentration in the range between 0.1 pg mL-1 and 500 ng/mL. The detection limit is as low as 19 fg mL-1. The aptasensor also has excellent electrochemical performances, which exhibits broad application prospects in biometric analysis.