Recent advances in nanomaterial-based electrochemical aptasensors for detecting aquatic toxins in shellfish and freshwater. A review

Aquatic toxins are potent, naturally occurring compounds produced by dinoflagellates, cyanobacteria, and diatoms during harmful algal blooms (HABs) in both freshwater and marine ecosystems. These toxins can accumulate in seafood, such as scallops, oysters, mussels, and certain fish, posing a significant global threat to human health and the environment. The current methods for detecting these aquatic toxins, such as mouse bioassays, liquid chromatography-tandem mass spectrometry (LC-MS/MS), and high-performance liquid chromatography (HPLC), are limited by time-consuming procedures, high costs, and ethical problems. Therefore, there is an immediate need for the advancement of methods that are sensitive, specific, rapid, and affordable for detecting aquatic toxins. Electrochemical biosensors, particularly those incorporating nanomaterials and their composites, exhibit significant potential for enhancing sensitivity due to their large surface area, enhanced catalytic activity, superior electrical conductivity, chemical stability, tunable optical properties, and potential for functionalization. The integration of nanomaterials and their composites with aptamers further enhances the selectivity and specificity of these electrochemical aptasensors. Aptamers, single-stranded oligonucleotides with remarkable affinity and recognition capabilities, are highly valuable in designing nanomaterial-based electrochemical sensors. In comparison to antibodies, aptamers offer numerous benefits, including lower production costs, a smaller molecular weight, enhanced stability, lack of immunogenicity, rapid chemical synthesis, independence from animal sources for their production, ease of transportation, and storage. Therefore, the integration of electrochemical platforms with nanomaterials and aptamers is an effective tool for detecting aquatic toxins, thereby contributing to the protection of public and environmental health. This review focuses on the latest developments in electrochemical aptasensors based on nanomaterials for the detection of aquatic toxins, particularly microcystin-LR (MC-LR), saxitoxins (STX), microcystin-RR (MC-RR), okadaic acid (OA), and cylindrospermopsin (CYN). It explores their fundamental construction principles, methods of signal transduction, performance characteristics, and real-world sample applications of these electrochemical aptasensors in the detection of aquatic toxins. Furthermore, the review addresses existing challenges and outlines future research directions in this vital area of study.