Green-Synthesized Nanomaterials for Electrochemical Cyanotoxin Biosensing: Analytical Performance, Environmental...

Cyanobacterial blooms pose a persistent threat to aquatic ecosystems and public health through the production of diverse cyanotoxins, including microcystins, saxitoxins, cylindrospermopsin, and anatoxin-a. Electrochemical biosensors offer promising solutions for rapid, portable cyanotoxin monitoring; however, the environmental sustainability of nanomaterials and their synthesis requires critical evaluation. This review examines electrochemical cyanotoxin biosensors incorporating demonstrably green-synthesized or biomass-derived nanomaterials reported between 2013 and 2026. Particular emphasis is placed on biomass-derived carbon materials, their influence on bioreceptor immobilization, interfacial charge transfer, signal generation, and analytical performance. Confirmed green-synthesis approaches are distinguished from conventional nanomaterials and studies involving partially green processing or broader sustainability claims. Analytical performance is assessed through linear range, detection limit, selectivity, reproducibility, stability, and validation in environmental matrices. The available evidence reveals that genuinely green nanomaterial-based electrochemical cyanotoxin biosensing remains limited, with microcystin-LR dominating the qualifying studies. Key challenges include inconsistent material characterization, insufficient assessment of energy and resource consumption, limited life-cycle information, batch-to-batch variability, and inadequate validation using untreated environmental samples. Future research should prioritize reproducible and scalable sensing platforms while demonstrating sustainability through transparent reporting of synthesis conditions, resource requirements, environmental impacts, and end-of-life considerations, rather than relying solely on low detection limits or green-synthesis claims.