Label-free and simultaneous detection of vitamins K1 and D3 by a dual-channel fiber optic LSPR-based on MSM Concave Tip

• Dual-channel LSPR FOBS with MSM concave tip for simultaneous VK 1 & VD 3 sensing. • 2Ch-LSPR were excited by Au and Au@Ag core-shell nanoparticles. • MWCNT-chit nanohybrid for VK 1 ; MIP method with MWCNT-polypyrrole for VD 3 detection. • Detection limit ∼ 7.8 × 10 − 6 μ g / l (VK 1 ) and 3.6 × 10 − 5 μ g / l (VD 3 ) with high selectivity. • Applicability of the FOBS was tested with mixed vitamins and human serum samples. This research reports a dual-channel fiber optic LSPR biosensor utilizing a multimode-single mode-multimode (MSM) concave tip fiber for the label-free and simultaneous detection of Vitamin K 1 (VK 1 ) and 25(OH)Vitamin D 3 (VD 3 ) levels. The concave structure, fabricated by HF etching of the MSM fiber tip, functions as a microlens that enhances the evanescent field (EF) intensity to excite LSPR modes efficiently. The sensor was developed by exploiting two distinct LSPR modes associated with Au nanoparticles (AuNPs) on Channel 1 (Ch 1 ) and Au@Ag core-shell NPs (CSNPs) on Channel 2 (Ch 2 ). The selectivity of Ch 1 for VK 1 and Ch 2 for VD 3 is realized by coating a multi-walled carbon nanotube-chitosan (MWCNT-Chit) nanohybrid on the AuNPs-functionalized Ch 1 surface, and a MWCNT-polypyrrole/VD 3 molecularly imprinted polymer (MWCNT-PPy/VD 3 MIP) matrix on the CSNPs-functionalized Ch 2 surface, respectively. This selectivity results from increased dielectric functions of the nanohybrid and MIP matrix, due to selective redox reactions between MWCNT-Chit and VK 1 molecules, as well as the trapping of VD 3 molecules in the active imprinted cavities of MWCNT-PPy/VD 3 MIP. The obtained limit of detection of the sensor was LO D V K 1 ∼ 7.8 × 10 − 6 μ g / l and LO D V D 3 ∼ 3.6 × 10 − 5 μ g / l in the range of 0-10 −3 g/l. The proposed sensor was checked for the detection of VK 1 and VD 3 in standard mixed samples and the human serum samples. The results demonstrate the applicability of the designed sensor for label-free, simultaneous detection of VK 1 and VD 3 , exhibiting high selectivity, repeatability, and stability. Moreover, the sensor supports miniaturization, making it suitable for in vivo and in vitro clinical sensing applications.