High-performance electrochemical immunosensor for ultrasensitive detection of malachite green in food matrices using MOF-derived nanocomposites.

A highly specific and ultrasensitive electrochemical immunosensor for malachite green (MG) detection in complex food matrices is presented. The sensor was constructed through a stepwise assembly process incorporating gold nanoparticles, antibodies, and metal-organic framework (MOF)-derived Pd/CuO@NiO nanocomposites. Its structure and electrochemical performance were thoroughly validated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Key detection parameters, including pH and nanocomposite concentration, were systematically optimized to maximize sensor performance. The sensor demonstrated a broad linear detection range (10-4 to 100 ng/mL) and an ultralow detection limit (42 pg/L). Specificity tests confirmed the immunosensor's ability to selectively detect MG without interference from structurally similar compounds such as crystal violet, nitrofuran drugs, and chloramphenicol. Its practical applicability was verified using pretreated freshwater fish samples spiked with MG, yielding recoveries of 95%-105%. Furthermore, the results showed strong agreement with those of the conventional enzyme-linked immunosorbent assays (ELISA) method, with minimal difference ratios observed. These findings establish the immunosensor as a reliable, accurate, and rapid tool for detecting MG in food safety applications. Looking ahead, the platform's modular design and versatility provide opportunities to extend its application to other harmful contaminants in food and environmental monitoring, contributing to broader advancements in public health and safety.