A smartphone-controlled amperometric immunosensor for the detection of Pacific ciguatoxins in fish

[Display omitted] •A portable immunosensor for the detection of Pacific ciguatoxins in fish was developed.•The biosensor uses a smartphone-controlled potentiostat for signal readout.•The biosensor allows detection of Pacific ciguatoxins in fish at the FDA guidance level.•Fish samples from Japan and Fiji were analyzed with different techniques.•Excellent correlations were obtained with ELISA, CBA and LC-MS/MS. Ciguatoxins (CTXs) are marine neurotoxins produced by microalgae of the genera Gambierdiscus and Fukuyoa. CTXs may reach humans through food webs and cause ciguatera fish poisoning (CFP). An immunosensor for the detection of Pacific CTXs in fish was developed using multiwalled carbon nanotube (MWCNT)-modified carbon electrodes and a smartphone-controlled potentiostat. The biosensor attained a limit of detection (LOD) and a limit of quantification (LOQ) of 6 and 27 pg/mL of CTX1B, respectively, which were 0.001 and 0.005 μg/kg in fish flesh. In the analysis of fish samples from Japan and Fiji, excellent correlations were found with sandwich enzyme-linked immunosorbent assays (ELISAs), a cell-based assay (CBA) and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Stability of at least 3 months at −20 °C was predicted. In just over 2 h, the biosensor provides reliable, accurate and precise Pacific CTX contents in fish extracts, being suitable for monitoring and research programs.