A cyclometalated iridium(III) complex used as a conductor for the electrochemical sensing of IFN-γ

A novel iridium(III) complex was prepared and used as a conductor for sensitive and enzyme-free electrochemical detection of interferon gamma (IFN-gamma). This assay is based on a dual signal amplification mechanism involving positively charged gold nanoparticles ((+) AuNPs) and hybridization chain reaction (HCR). To construct the sensor, nafion (Nf) and (+) AuNPs composite membrane was first immobilized onto the electrode surface. Subsequently, a loop-stem structured capture probe (CP) containing a special IFN-gamma interact strand was modified onto the (+) AuNP surface via the formation of Au-S bonds. Upon addition of IFN-gamma, the loop-stem structure of CP was opened, and the newly exposed sticky region of CP then hybridized with DNA hairpin-1 (H-1), which in turn opened its hairpin structure for hybridizing with DNA hairpin-2 (H-2). Happen of HCR between H-1 and H-2 thus generated a polymeric duplex DNA (dsDNA) chain. Meanwhile, the iridium(III) complex could interact with the grooves of the dsDNA polymer, producing a strong current signal that was proportional to IFN-gamma concentration. Thus, sensitive detection of IFN-gamma could be realized with a detection limit down to 16.3 fM. Moreover, satisfied results were achieved by using this method for the detection of IFN-gamma in human serum samples.