Ultrasensitive LSPR-based detection of deoxynivalenol using Mo–MnO₂ nanoparticle–palladium nanocube hybrid fiber-optic nanoplatform

Deoxynivalenol (DON) is a widespread and harmful mycotoxin in cereal grains that impairs intestinal barrier function and poses severe health threats to humans and animals. In this study, a localized surface plasmon resonance (LSPR) optical fiber biosensor based on a tapered multimode fiber-nanomaterial-doped fiber-multimode fiber (MMF-NDF-MMF) structure was constructed for the quantitative detection of DON. The tapered fiber structure effectively enhances the evanescent field intensity and excites the sensitive LSPR responses of gold nanoparticles (AuNPs). Mo‑MnO 2 acts as an additional high‑specific‑surface‑area component on the pre‑deposited AuNP layer to further accommodate PdNCs and increase available surface sites. Combined with the local dielectric polarization and interfacial field enhancement expected for PdNCs, subtle refractive index (RI) variations triggered by specific aptamer‑DON binding can be further amplified, contributing to improved LSPR spectral sensitivity. The entire sensing mechanism relies purely on evanescent field-induced LSPR wavelength shifts caused by local RI changes, with no involvement of photocatalytic, electrochemical, or nanozyme‑mediated chemical signal‑amplification pathways. The experimental results demonstrate that the proposed sensor exhibits a favorable linear detection range of 0.169–675 nM for DON. The sensor exhibited excellent reusability, reproducibility, long-term stability, and anti-interference performance. This LSPR biosensor provides a simple, low-cost, and reliable strategy for the rapid and on-site monitoring of DON contamination in grain samples, showing promising application prospects in food safety supervision and agricultural quality control.