Design and Validation of a Molecularly Imprinted Polymer Electrochemical Sensor for Ultratrace Detection of Aflatoxin B1 in Nigerian Staple Foods

Aflatoxin B1 contamination of staple foods including maize, groundnut, and sorghum exacts a severe public health and economic toll across Nigerian food systems, yet existing analytical methods based on immunoaffinity chromatography and high-performance liquid chromatography are too costly, instrument-intensive, and technically demanding for routine food safety monitoring by regulatory agencies and commodity traders operating outside major laboratory centres in Nigeria. This study designs, fabricates, and validates a molecularly imprinted polymer-based electrochemical biosensor for the ultratrace detection of aflatoxin B1 in Nigerian staple food matrices. Molecular imprinting employs methacrylic acid as functional monomer and ethylene glycol dimethacrylate as crosslinker, optimised by computational molecular docking to select the highest-affinity template-monomer interaction configuration. The molecularly imprinted polymer is electrodeposited onto a screen-printed carbon electrode modified with gold nanoparticles and reduced graphene oxide to enhance charge transfer kinetics. Sensor characterisation employs cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. Analytical performance is assessed for sensitivity, detection limit, linear dynamic range, selectivity against aflatoxin B2, G1, G2, and ochratoxin A, reproducibility, and storage stability. A systematic matrix effect study evaluates sensor performance in extracts of maize, groundnut, and sorghum samples spiked at concentrations relevant to European Union and Codex Alimentarius maximum levels. Field validation is conducted by comparison with high-performance liquid chromatography-fluorescence reference method analysis of 120 real market samples from North East, North West, and North Central Nigerian markets. An original mathematical model for molecularly imprinted polymer rebinding kinetics under competitive matrix conditions is developed as a theoretical contribution. Keywords: molecularly imprinted polymer, electrochemical sensor, aflatoxin B1, ultratrace detection, food safety Nigeria