Reduced Graphene Oxide Field-Effect Transistor Biosensor for Microcystin Detection: Proof-of-Concept Using Water Samples

Microcystins are hepatotoxic cyanotoxins associated with severe adverse health effects and represent an important public health concern due to their widespread occurrence in contaminated water sources. Rapid and sensitive detection of these toxins is essential to support exposure monitoring and the development of future biomedical applications. In this study, a reduced graphene oxide field-effect transistor (rGO FET)-based biosensor was developed for microcystin detection using water as an initial proof-of-concept validation matrix. Gold interdigitated electrodes were functionalized with electrochemically reduced graphene oxide and biofunctionalized with microcystin-specific antibodies through physical adsorption. The devices were characterized by cyclic voltammetry, Raman spectroscopy, optical microscopy, and electrical measurements. Analytical validation was performed using standard solutions and water samples spiked with microcystin-LR at the World Health Organization (WHO) guideline concentration for drinking water (1 µg/L). The biosensor successfully detected microcystin-LR, exhibiting distinguishable electrical responses between toxin-containing and blank samples in both ultrapure water and rainwater. These findings demonstrate the feasibility of the proposed platform and establish a foundation for future studies involving the detection of microcystins in biological fluids and tissues, contributing to toxin exposure assessment, toxicological investigations, and health surveillance.