Prussian blue anchored Fe(Ⅲ)-Tannic acid composite-mediated colorimetric and photothermal dual-mode immunosensor for the detection of tetrodotoxin

Abstract

Tetrodotoxin (TTX) is a well-known and potent marine toxin, and the sensitive and specific detection of TTX is crucial for safeguarding seafood safety and protecting consumer health. This study describes the development of a nanozyme with enhanced peroxidase-like activity, photothermal properties, and biocompatibility, synthesized through the in-situ formation of Prussian blue (PB) on Fe (Ⅲ)-tannic acid coordination particle (FTAN), forming the FTAN@PB composite. This composite effectively catalyzes the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by hydrogen peroxide (H₂O₂), generating the one-electron oxidation product of TMB (oxTMB), which manifests as a discernible color change and exhibits a strong near-infrared (NIR) photothermal response upon irradiation with an 808 nm laser. Leveraging the inherent protein adsorption capacity of tannic acid, an immunoprobe with dual-signal readout capability was developed by conjugating goat anti-mouse IgG with FTAN@PB via a simplified mixing procedure that required no activating or condensing agents. A competitive immunoassay format was employed for TTX quantification, utilizing both colorimetric and photothermal signal detection with a microplate reader and a portable infrared imaging thermometer, respectively. Under optimal conditions, TTX in aquatic products was detectable within a range of 0.1–100 ng/mL, with detection limits of 0.26 ng/mL for the colorimetric mode and 0.44 ng/mL for the photothermometric mode. Validation of the dual-mode immunosensor was performed using real-world samples, demonstrating acceptable recovery rates, selectivity, and reliability, thus highlighting its potential utility in food safety analysis.