Preparation and evaluation of temperature and magnetic dual-responsive molecularly imprinted polymers for the specific enrichment of formononetin.

Thermo-responsive magnetic molecularly imprinted polymers were prepared by simple surface molecular imprinting polymerization for the selective adsorption and enrichment of formononetin from Trifolium pretense by temperature regulation. Using formononetin as a template, N-isopropylacrylamide as the thermo-responsive functional monomer, and methacrylic acid as an assisting functional monomer, the polymers were synthesized on the surface of the magnetic substrate. The results show that imprinted polymers attained controlled adsorption of formononetin in response to the temperature change, with large adsorption capacity (16.43 mg/g), fast kinetics (60 min) and good selectivity at 35°C compared with that at 25 and 45°C. The selectivity experiment indicated that the materials had excellent recognition ability for formononetin and the selectivity factors were between 1.32 and 2.98 towards genistein and daidzein. The excellent linearity was attained in the range of 5-100 μg/mL, with low detection limits and low quantitation limits of 0.017 and 0.063 μg/mL, respectively. Furthermore, the thermo-responsive magnetic molecularly imprinted polymers were successfully utilized for enriching and purifying formononetin from Trifolium pretense. The analytical results indicate that the imprinted polymers are promising materials for selective identification and enrichment of formononetin in complicated herbal medicines by simple temperature-responsive regulation.