Highly selective and cost-effective impedimetric biosensor for cylindrospermopsin detection using an aptamer-functionalized pencil graphite electrode

Nutrient runoff from anthropogenic eutrophication, rising atmospheric CO₂ levels, and global warming have significantly contributed to the proliferation of harmful cyanobacterial blooms in freshwater ecosystems. These blooms release cyanotoxins, such as cylindrospermopsin (CYN), which pose genotoxic and cytotoxic effects. The detection and monitoring of CYN in water are essential for protecting public health and reducing environmental risks. In this study, an electrochemical aptasensor was developed by effective immobilization of CYN-specific aptamer (cynApt) onto a highly conductive pencil graphite electrode (PGE), which offers a sustainable alternative to expensive gold and graphene-based sensors. CYN was detected through electrochemical impedance spectroscopy (EIS) by monitoring changes in charge transfer resistance. The detection limits for CYN using PGE/cynApt electrodes were found to be 0.78 ng mL^-1 in deionized water and 0.97 ng mL^-1 in lake water, within a linear range of 1-20 ng mL^-1. The selectivity of the biosensor for CYN was also tested against other cyanotoxins, such as okadaic acid and saxitoxin, both in deionized and lake water.