Saxitoxin (STX) is a potent toxin produced by marine dinoflagellates and freshwater or brackish water cyanobacteria, and is a member of the paralytic shellfish toxins (PSTs). As a highly specific blocker of voltage-gated sodium channels (NaVs), STX blocks sodium ion influx, thereby inhibiting nerve impulse transmission and leading to systemic physiological dysfunctions in the nervous, respiratory, cardiovascular, and digestive systems. Severe exposure can lead to paralysis, respiratory failure, and mortality. STX primarily enters the human body through the consumption of contaminated shellfish, posing a significant public health risk as the causative agent of paralytic shellfish poisoning (PSP). Beyond its acute toxicity, STX exerts cascading impacts on food safety, marine ecosystem integrity, and economic stability, particularly in regions affected by harmful algal blooms (HABs). Moreover, the complex molecular structure of STX—tricyclic skeleton and biguanide group—and its diverse analogs (more than 50 derivatives) have made it the focus of research on natural toxins. In this review, we traced the discovery history, chemical structure, molecular biosynthesis, biological enrichment mechanisms, and toxicological actions of STX. Moreover, we highlighted recent advancements in the potential for detection and treatment strategies of STX. By integrating multidisciplinary insights, this review aims to provide a holistic understanding of STX and to guide future research directions for its prevention, management, and potential applications.

The accurate and sensitive detection of toxin contamination remains a pressing challenge for food safety, environmental integrity, and public health, because conventional analytical methods suffer from high costs, poor field stability, and inadequate sensitivity for trace-level emerging contaminants. In this review, we provide a comprehensive overview of biosensor technologies for toxin detection, with a dedicated focus on nucleic acid aptamers and SELEX (Systematic Evolution of Ligands by Exponential Enrichment) technology. We systematically categorize nine SELEX variants developed for toxin detection, covering target-immobilized, library-immobilized, non-immobilized, cell-based, and high-throughput platforms, with an emphasis on their selection principles, applicability, and limitations. This review discusses computationally assisted aptamer discovery (e.g., AI-based sequence generation and molecular docking) as well as experimental post-SELEX optimization strategies such as cyclization, multivalent assembly, and structure-switching design. We then discuss key challenges and future perspectives, highlighting the shift from method-oriented to demand-oriented aptamer development through integrated SELEX strategies and AI-assisted design. Overall, this review covers mainstream SELEX technologies, aptamer selection, computational design, experimental optimization, and sensor integration to serve as a reference for next-generation toxin detection applications.