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The existing assays for detecting brevetoxin (BTX) depend on expensive equipment with a professional operator or on an antibody with limited stability, which requires complex processes, a high cost, and a considerable amount of time. The development of an alternative detection probe is another promising research direction. This paper reports the use of aptamers binding to BTX-2 in an analytical assay using the systematic evolution of ligands by exponential enrichment (SELEX). After 12 rounds of selection, the secondary structures of 25 sequences were predicted. Compared to other aptamers, Bap5 has relatively high affinity with the lowest dissociation constant of 4.83 μM, and IC50 is 73.81 ng mL−1. A good linear regression formula of y = 30.688x − 7.329 with a coefficient correlation of R 2 = 0.9798 was obtained using a biotin-avidin ELISA. Moreover, there is no cross-reaction with the detected marine toxins, except for BTX-2. Thus, Bap5 has potential to detect BTX-2 in shellfish in the future as a substitute for the recognition probe.

In this article, high-affinity single-stranded DNA (ssDNA) aptamer-targeting F(ab')₂ fragments of saxitoxin (STX) antibodies were selected from a random ssDNA library by the SELEX strategy. After 16 rounds of repeated selection, the enriched ssDNA library was sequenced, and all of the sequences were carefully identified by indirect enzyme-linked assay and indirect competitive enzyme-linked assay (icELISA). The candidate aptamers in the above identification were selected for further characterization by icELISA and the equilibrium filtration method. We successfully obtained an aptamer that mimics STX in antibody binding, and a substitute for STX in aptamer form has been developed. Further work is in progress aimed at using this aptamer substitute to replace the STX standard in an antibody-based, nontoxic detection method for field determination of STX in seafood products.

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