Electrochemical\nBiosensor for the Assessment of Cell\nViability Using Methylene Blue. Application to the Detection of Ciguatoxins\nin Fish from the Canary Islands

Cell-based biosensors (CBBs) for\nthe detection of marine\nneurotoxins\nsuch as ciguatoxins (CTXs) are of high interest due to the composite\ntoxicological response they can provide and the low limits of quantification\n(LOQs) they can achieve with the use of sensitive neural cells. However,\nthe development and validation of CBBs are challenging due to the\nuse of living material and the need for appropriate signal transduction\nstrategies. In this work, Neuro-2a cells have been immobilized on\nthin-film gold electrodes, and their viability after exposure to CTX1B\nhas been evaluated with light optical microscopy as well as cyclic\nvoltammetry (CV) and differential pulse voltammetry (DPV) using methylene\nblue (MB) as a redox indicator. An LOQ of 0.93 pg CTX1B/mL has been\nobtained. The CBB has been applied to the analysis of fish samples\nfrom the Canary Islands, one of them implicated in a ciguatera poisoning\n(CP) outbreak, and results have been compared with those obtained\nwith a conventional cell-based assay (CBA), showing a very good agreement.\nThe combination of the benefits of cells with those provided by biosensor\nplatforms in terms of ease of use, miniaturization, automatization,\nand portability could result in the ideal analytical tool for CP management.\nAdditionally, this is the first time MB is used as a cell viability\nindicator in a CBB, providing a new versatile approach for multiple\napplications.