Multiple signal amplification and selective recognition reactions-assisted homogeneous binary visual aptasensor of tuberculosis interferon γ in clinical samples

Interferon-γ (IFN-γ) analysis is critical for tuberculosis (TB) diagnosis. However, the existing conventional immunoassay methods are less sensitive and laborious. We describe cadmium telluride quantum dots (CdTe QDs) and calcein-based binary visual and fluorescence homogeneous aptamer sensing strategy for IFN-γ analysis. This strategy integrates enzyme-free catalytic hairpin assembly (CHA) amplification, selective recognition properties of QDs and calcein for Ag+ and C-Ag+-C structures, and ink-jet printing technology for making test strips. Using QDs- and calcein-based fluorescence modes, respectively, IFN-γ with limits of detection (LODs) as low as 0.3 ag/mL and 0.25 ag/mL were obtained at optimum conditions. Color and distance reading modes enabled the analysis of 100 ag/mL IFN-γ with naked eyes. Quantitative findings of IFN-γ analysis in 51 clinical plasma samples using dual fluorescence modes were in line with those obtained by enzyme-linked immunosorbent assay (ELISA), sputum culture, polymerase chain reaction (PCR), Xpert MTB/rifampin (RIF) and computed tomography (CT). Additionally, findings from IFN-γ analysis in 12 clinical samples obtained using QDs- and calcein-based distance reading strips were highly consistent with those of ELISA. Therefore, our analytical system may provide an additional and more sensitive tool for early diagnosis of TB.