Tetrodotoxin detection in puffer fish by a sensitive planar waveguide immunosensor

A nanoarray planar waveguide biosensor was developed for the detection of tetrodotoxin (TTX). This technique, specifically designed for the first time for TTX, provided a compact versatile user friendly device that obtained a test result in ten minutes. The device consisted of nanoprinted toxin-conjugate arrays constructed in the manner of an indirect competitive immunoassay, for the analysis of puffer fish samples under high flow conditions. The applicability to natural samples was investigated through the study of matrix effects and toxin recovery. The biosensor enabled the detection of TTX from 0.4 to 3.29 μg g⁻¹ puffer fish tissue. The sensitivity attained demonstrates this assay as a rapid and sensitive screening method to detect TTX in different species of puffer fish, well below the Japanese maximum permitted level (2 μg g⁻¹) and the estimated safety level used in the EU and the US (0.8 μg g⁻¹). Assay repeatability and reproducibility were assessed at 0.4 and 0.8 μg g⁻¹, showing relative standard deviation (RSD) values below 15% and toxin recovery within 85–115%. The appropriate correlation of data obtained from the biosensor compared to that reported by ELISA, RBA, SPR biosensor and LC–MS/MS for the analysis of 12 puffer fish samples, proved the feasibility and reliability of this immunosensor to support monitoring programs and research activities.