Opto-fiber biosensor for tetrodotoxin detection using novel optical fiber structure functionalized with MoS₂ and...

Tetrodotoxin (TTX) is one of the most potent neurotoxins, with complex structures and analgesic effects. This toxin exists mainly in aquatic organisms, such as pufferfish, and has high biological activity. In this study, a novel three-tapered opto-fiber biosensor based on the localized surface plasmon resonance (LSPR) phenomenon was developed for the detection of TTX at different concentrations. A combiner manufacturing system and advanced fusion splicer processing technologies were used to produce a novel and unique tapered structure. Molybdenum disulfide (MoS₂-NSs)/multi-walled carbon nanotubes (MWCNTs) were immobilized on the surface of the probe to enhance biocompatibility. This composite layer was deposited prior to gold nanoparticles (AuNPs), which not only provided sufficient space for the immobilization of nanoparticles but also increased the specific surface area for biomolecule attachment. Through the immobilization of AuNPs on the probe surface, the evanescent field can excite AuNPs to generate LSPR, thereby realizing the detection of TTX. The surface of the sensing probe was functionalized with bovine serum albumin, which significantly improved the selective recognition ability of TTX. The experimental results showed that the sensor had a sensitivity of 0.0016 nm/(ng/mL) in the linear detection range of 0-800 ng/mL, with a detection limit of 32.7 ng/mL. Additionally, the reusability, reproducibility, stability, and selectivity of the probe were tested and verified. The results for various indicators confirmed that the probe has high application potential in the field of TTX detection.