A triple-helix molecular switch-based electrochemical aptasensor for interferon-gamma using a gold electrode and Methylene Blue as a redox probe

Detection and quantitation of interferon-gamma (IFN-gamma) in blood is of vital importance for diagnosis of latent tuberculosis. The authors describe an electrochemical aptasensor for IFN-gamma that is based on a triple-helix molecular switch (THMS). The combination of a THMS with amperometry makes the sensor selective, sensitive and fast (50 min). In the presence of IFN-gamma, the structure of the THMS is disassembled and the electrochemical probes, Methylene Blue (MB), can only bind to the signal transduction probe (STP) on the surface of the gold electrode, this leading to a weak peak current. However, in the absence of IFN-gamma, the structure of THMS is preserved and MB can interact with the THMS to result in strong current (typically measured at -0.24 V vs. silver reference electrode). Under optimized conditions, the assay has a 3 pg.mL(-1) detection limit and a linear range that extends from 10 to 1500 pg.mL(-1). Employed to the determination of IFN-gamma in spiked serum samples, it gave recoveries that ranged from 91.3% to 102.8%.