Tetrad metal ion mediated molecular switch aptamer sensor for fluorescence assay of plasma IP-10 in clinical tuberculosis

Interferon-γ-inducible protein 10 (IP-10) has demonstrated enormous potential as a novel biomarker for tuberculosis (TB), particularly in the monitoring of patient progression for active or latent tuberculosis infection (LTBI). Herein, we established a tetrad metal ion-mediated molecular switch aptamer sensor for the convenient detection of IP-10 in plasma and the diagnosis of TB. The simple sensor relied on the partially complementary IP-10 aptamer and four DNA hairpin strands rich in cytosine (C), which can form a relatively stable tetrad C-Ag+-C structure when combined with Ag+ without additional modification. Based on the specific recognition of IP-10 and aptamer, a large amount of Ag+ could be released in a short time. Combining with cadmium telluride quantum dots (CdTe QDs) as the signal reporter, we achieved superior analytical performance, with the limits of detection (LOD) reaching 3 fg/mL for IP-10 analysis in 1h. Clinical practicality was confirmed by evaluating 38 clinical samples (19 TB-positive patients, 14 non-TB patients, and 5 latent TB infection patients). The results showed that the detected IP-10 levels were significantly different between the non-TB and TB/LTBI groups, and the results aligned with clinical computed tomography (CT) results, indicating that the method could represent a reliable diagnostic technique for TB.