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

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.

Screening of a ScFv Antibody With High Affinity for Application in Human IFN-γ Immunoassay

“…Compared to the ECD method, the developed method based on ic-ELISA has high specificity and accuracy, and the principal advantages of this method are simple, quick, efficient, and does not require sophisticated instruments and tedious sample pre-treatments. Ic-ELISA indicated that the linear range to detect IFN-γ was 6–60 pg/mL with IC 50 of 25 pg/mL, and the LOD was 1.3 fm, which is lower than any other LOD reported previously ( Liu et al, 2010 ; Miao et al, 2017 ).…”

“…Hence, it is critical to develop an accurate method to detect IFN-γ secretion in real samples. At present, some different kinds of methods based on electrochemical detection (ECD) and ELISA are used to IFN-γ ( Liu et al, 2010 ; Sanchez et al, 2014 ; Miao et al, 2017 ), but the above method based on ECD is improper for the actual sample detection because complex samples treatment and need expensive equipment/professional technicians. To date, immunoassays based on different kinds of antibodies, such as poly-clonal antibody, monoclonal antibody, and genetic engineering antibody, have also been used widely in immunological detection of target protein and pathogens in samples ( Wang et al, 2012 , 2014b , 2016 ; Saeed et al, 2017 ).…”

“…To date, some traditional techniques have been used to detect IFN-γ in real samples, including cyclometalated iridium (III) complex conductor ( Miao et al, 2017 ), micropatterned aptamer-modified electrodes ( Liu et al, 2012 ), DNA aptamer-based electrochemical biosensor ( Liu et al, 2010 ) and ELISpot ( Sanchez et al, 2014 ). Although these methods are effective and accurate for detection of IFN-γ, but they are often inconvenient, time-consuming, and need expensive equipment ( Wang et al, 2016 ).…”

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

“…Correspondingly, a linear regression equation of I peak ¼ 14.40 + 3.36 log C IFN-g (R 2 ¼ 0.995) with a low detection limit of 2 pM (S/N ¼ 3) was achieved. Although more analytical time was required comparing with some other reported IFN-g aptasensors (shown in Table S2 †), 17,18,[55][56][57][58][59] the performance of prepared aptasensor was comparable or better than most of reported biosensors. Besides, the proposed aptasensor could not be regenerated due to the involved target recycling strategy assisted with exonuclease.…”

Inorganic Complexes and Metal-Based Nanomaterials for Infectious Disease Diagnostics

“…(B) The redox reaction of [Ir(ppy) 2 (phen-dione)] + was achieved by differential pulse voltammetry, which produced a current that was correlated to the presence of IFN-γ. Adapted with permission from ref (145). Copyright 2017 Nature Publishing Group ().…”