Telluride quantum dot-amplified immunosensor for interferon gamma – A TB antigen test biomarker

Interferon-gamma (IFN-γ) is a cytokine (i.e. a microprotein involved in cell signaling and immunomodulation) which is known to be expressed in response to Mycobacterium tuberculosis (Mtb) infections. For this reason, IFN-γ has gained prominence as a diagnostic biomarker for TB antigen tests, such as Interferon-Gamma Release Assays (IGRAs). Recent research efforts have focused on improving the sensitivity of TB tests based on IFN-γ. In this study, a new and sensitive chalcogenide-based electrochemical IFN-γ immunosensor was developed. The chalcogenide is a 9.30 nm average diameter bimetallic copper zinc telluride (CuZnTe) quantum dot (QD) particles, which were stabilised by sequential triple-capping with thioglycolic acid (TGA), (3-mercaptopropyl)trimethoxysilane (MPS) and tetraethylorthosilicate (TEOS) (i.e. CuZnTe-TGA-MPS-TEOS QD). The morphologies of the quantum dots were determined by X-ray transmission electron microscopy (TEM) and small angle X-ray scattering spectroscopy (SAXS); while their structural characteristics were ascertained with Raman and X-ray diffraction (XRD) spectroscopic analyses. A gold disk electrode (AuE) surface was functionalized with CuZnTe-TGA-MPS-TEOS QD, anti-interferon-gamma antibody (Anti) and bovine serum albumin (BSA) to create a BSA/Anti/CuZnTe-TGA-MPS-TEOS QD/AuE amperometric immunosensor bioelectrode. The immunosensor exhibited a linear detection range (LDR) value of 2–20 pg/mL IFN-γ, a limit of detection (LOD) value of 0.82 pg/mL IFN-γ and was highly sensitive in human serum samples with recovery rates of 97–99 %.