Abstract
A novel iridium(III) complex was prepared and used as a conductor for sensitive and enzyme-free electrochemical detection of interferon gamma (IFN-γ). 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-γ interact strand was modified onto the (+)AuNP surface via the formation of Au-S bonds. Upon addition of IFN-γ, the loop-stem structure of CP was opened, and the newly exposed “sticky” region of CP then hybridized with DNA hairpin-1 (H1), which in turn opened its hairpin structure for hybridizing with DNA hairpin-2 (H2). Happen of HCR between H1 and H2 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-γ concentration. Thus, sensitive detection of IFN-γ 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-γ in human serum samples.
Highlights
Interferon gamma (IFN-γ) is a type of cytokine that can activate multiple signal transduction pathways through the transcriptional regulation of immunologically relevant genes[1]
Zhao et al constructed an electrochemical aptasensor for IFN-γsensing based on the hybridization chain reaction (HCR) coupled with enzyme-signal amplification[8]; Luo and Pu groups realized IFN-γdetection using a dual signal amplification approach by exonuclease-mediated surface-initiated enzymatic polymerization[2]; Wang and He groups developed a sensitive label-free electrochemical aptasensor for IFN-γdetection through nuclease cleavage-assisted target recycling amplification[9]
Iridium(III) complex could bind with the grooves of the dsDNA polymer, producing a strong current signal that was proportional to IFN-γconcentration (Fig. 1)
Summary
Interferon gamma (IFN-γ) is a type of cytokine that can activate multiple signal transduction pathways through the transcriptional regulation of immunologically relevant genes[1]. Zhao et al constructed an electrochemical aptasensor for IFN-γsensing based on the hybridization chain reaction (HCR) coupled with enzyme-signal amplification[8]; Luo and Pu groups realized IFN-γdetection using a dual signal amplification approach by exonuclease-mediated surface-initiated enzymatic polymerization[2]; Wang and He groups developed a sensitive label-free electrochemical aptasensor for IFN-γdetection through nuclease cleavage-assisted target recycling amplification[9]. These methods have certain drawbacks, such as the use of enzymes and/or the labelling of probe molecules, which limit the utilization of them for the routine detection of IFN-γ. The iridium(III) complex used here could interact in a stable fashion with the unlabelled dsDNA polymers, making the detection of IFN-γsimple and low-cost[24,25]
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