Functionalized cascaded tapered optical fiber sensor for simultaneous detection of dengue II E and SARS-CoV-2 S proteins

This work demonstrates a label-free dual-sensing biosensor utilizing cascaded single-mode tapered fiber (SMTF) for the concurrent detection of Dengue II envelope (E) and SARS-CoV-2 spike (S) proteins. Two fiber tapers of different dimensions were employed in-line, with each taper functionalized with specific complementary antibodies to the targeted antigens. The cascaded interferometric effect yielded composite spectral output that exhibited discrete response toward localized refractive index changes due to binding of antigens and antibodies. Consistent red shifts were observed with increasing concentration of the targeted analyte, which led to sensitivity values of 6.91 nm/nM for SMTF1 and 9.96 nm/nM for SMTF2, with a detection limit of 0.1 pM. This dual-sensing platform demonstrates high sensitivity and specificity, rapid response times, and the potential for integration into portable diagnostic devices, presenting it as a promising tool for point-of-care diagnostics and simultaneous detection of multiple disease biomarkers.