Flower-like L-Cys-FeNiNPs nanozyme aptasensor for sensitive colorimetric detection of aflatoxin B1

It is vital to create a sensitive and trustworthy sensor for aflatoxin B1 (AFB1) considering the potential hazards this substance poses to the safety of food. Herein, a colorimetric sensor, namely, aptamer-modified flower-like L-cysteine-functionalized FeNi bimetallic nanoparticles (L-Cys-FeNiNPs) with peroxidase-mimicking enzymatic activity, was established for the detection of aflatoxin B1. Interestingly, based on the synergies between FeNi bimetals and the protection and regulation of morphology by L-Cys on FeNiNPs, we successfully synthesized flower-like L-Cys-FeNiNPs, which were employed as outstanding peroxidase-mimic enzymes to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2. Kinetic analysis showed that the flower-like L-Cys-FeNiNPs have an ultralow Michaelis constant (Km) and an ultrahigh affinity for H2O2. Furthermore, based on the peroxidase-mimicking activity of flower-like L-Cys-FeNiNPs, a new colorimetric aptamer sensing strategy was employed for the easy and specific detection of AFB1 with a wide response range (0.12–2 μg/mL) and a low detection limit (36.57 ng/mL). Finally, to verify the practicality of this aptamer detection strategy, we successfully applied it to the detection of AFB1 in actual millet and maize samples.