A Single-Step Magnetic Bead-Based Sandwich Immunoassay for the Rapid Detection of Ciguatoxins in Fish Samples

Ciguatera poisoning (CP) is one of the most prevalent non-bacterial seafood-borne illnesses worldwide, caused by the consumption of fish contaminated with ciguatoxins (CTXs). Even though its prevention largely relies on avoidance of certain fishes and geographic regions, the development of rapid and user-friendly bioanalytical methods for effective CP management and surveillance is still necessary. In this work, four simplified strategies of a magnetic bead (MB)-based sandwich immunoassay were proposed for the rapid and highly sensitive detection of CTXs in fish. The one consisting of a single step was selected, which allowed the detection of CTXs in a fish extract in only 40 min at levels as low as 0.01 μg CTX1B equivalents/kg of fish, which is the safety guidance level proposed by the United States Food and Drug Administration (FDA). In this strategy, all components were incubated simultaneously with the sample, only requiring a subsequent washing and substrate incubation step before signal measurement, reducing the complexity and the time required for analysis in contrast with the classical sequential sandwich immunoassays. The ease of experimental handling, added to the short analysis time and appropriate sensitivity make this single-step immunoassay a promising tool for CP risk assessment and management.