Electrochemical biosensors for saxitoxin detection: advances, limitations, and challenges for market transition.

Saxitoxins, produced by freshwater cyanobacteria and marine dinoflagellates, block neuronal sodium channels and can cause paralysis or death. They contaminate drinking water, bioaccumulate in aquatic organisms, and pose serious health risks. Conventional detection methods, though reliable, are costly, time-consuming, and require specialized personnel, limiting rapid or on-site use. Biosensors have emerged as attractive alternatives, with electrochemical platforms standing out for their high sensitivity, low cost, miniaturization potential, and easy integration into portable devices. These advantages make them promising tools for in situ monitoring of saxitoxins and justify a dedicated review. This work critically analyzes electrochemical biosensors for STX detection, highlighting advances, limitations, and challenges toward commercialization. We discuss operating principles, recognition elements, analytical performance, and classify devices by electrochemical technique (potentiometric, impedimetric, voltammetric), providing a comparative perspective on their respective strengths and limitations. Despite remarkable sensitivity-often below regulatory limits-key obstacles remain: lack of fabrication standardization, poor long-term stability, limited validation with naturally contaminated samples, insufficient robustness for complex matrices, low reproducibility, and absence of regulatory approval pathways. In addition, challenges associated with fabrication scalability and interlaboratory reproducibility continue to hinder the transition from proof-of-concept devices to commercially viable technologies. Overcoming these barriers is crucial for translating laboratory prototypes into reliable, field-deployable devices for environmental monitoring and food safety applications. Future developments should focus on improving robustness, reproducibility, and analytical validation to accelerate the practical implementation of electrochemical STX biosensors.