MOF-based fluorescent molecularly imprinted polymer nanosensor for the determination of aflatoxin M1 in water and cow milk with exceptional sensitivity
Contamination of food and feed with fungal aflatoxins is a major problem. Even extremely minute amounts of aflatoxins can be fatal to humans and animals if ingested with food or feed. Therefore, presenting analytical methods for the detection/determination of aflatoxins (e.g., aflatoxin M1, AFM1) is highly required for food contamination control. Here, we report a novel, highly sensitive fluorometric nanosensor for the rapid determination of AFM1 in water and cow milk. The proposed nanosensor is based on a fluorescent molecularly imprinted polymer (FMIP) comprising a molecularly imprinted polymer coating onto a chitosan-coated fluorescent metal organic framework (MOF). The FMIP was fabricated from a newly synthesized functional monomer, which was then conjugated with chitosan and used to coat the fluorescent MOF prior to its polymerization. The synthesized materials, including functional monomer, MOF, and FMIP were characterized using FTIR, 1H-NMR, DSC, XRD, dynamic light scattering, zeta potential measurement, and transmission electron microscopy (TEM) imaging. The analytical performance of the nanosensor was investigated and the incubation time was found to be 20 min, indicating the rapid analytical procedure. The nanosensor exhibited a limit of detection of 2.89 pg L−1 and a limit of quantification of 9.63 pg L−1, supporting the ultra-high sensitivity of the nanosensor. In addition, the fluorescence vs. concentration relationship is linear (r2 = 0.9945) over a wide concentration range of 3.3–63.3 pg L−1. Furthermore, the obtained recovery values are in the range 95.76–105.41% with a standard deviation of 1.72–2.65, indicating the high accuracy and precision of the nanosensor. Therefore, the FMIP-based nanosensor can be successfully applied to the determination of AFM1 in profoundly dilute water and cow milk samples.