Dual-signal amplified SERS sensing based on aptamer-modified Au/Fe3O4 nanohybrids and Ag NPs-functionalized bacterial cellulose film for on-site marine toxin analysis

Okadaic acid (OA), a diarrhetic shellfish toxin, poses severe health risks to humans and causes substantial economic losses in aquaculture, creating an urgent need for rapid, sensitive, and field-deployable detection technologies for tracing its contamination in shellfish. Herein, we proposed a surface-enhanced Raman scattering (SERS) sensing method for OA in shellfish. The system was constructed by integrating Raman-active aptamer-modified gold/magnetic nanohybrids (Apt-Au/Fe₃O₄ NHs) with a complementary sequence-modified silver nanoparticle-functionalized bacterial cellulose film (CS-Ag NPs@BC-film). Upon the introduction of OA, it competitively bound with the Apt, leaving the CS-Ag NPs@BC-film after magnetic separation, thereby inducing a reduction in the Raman signal. Sensitive quantification of OA was achieved by measuring the difference in the Raman signal, achieving a detection limit as low as 2.82 × 10⁻² nM (S/N = 3). Analysis of the spiked real samples demonstrated good accuracy and precision of the method. Compared with commercial ELISA kits, the method presented with comparable detection results while offering simplified operational workflows. These findings highlight its potential as a practical tool for monitoring hazardous contaminants in aquatic environments and ensuring seafood safety.