Magnetic Molecular Imprinted Polymers-Based Nanozyme for Specific Colorimetric Detection of Protocatechuic Acid

Magnetic molecular imprinted polymers nanozyme MIPs@Fe3O4-NH2 with high specificity and excellent peroxidase-like activity was prepared for colorimetric detection of protocatechuic acid (PCA). Firstly, MIPs@Fe3O4-NH2 was obtained by self-polymerization of dopamine as a functional monomer on the surface of Fe3O4-NH2, enabling the formation of specific recognition cavities. Later, the elution of PCA using polar solvents resulted in the creation of well-defined recognition sites on the surface of MIPs@Fe3O4-NH2. The synthesized MIPs@Fe3O4-NH2 exhibits rapid and selective magnetic separation of PCA. Meanwhile, MIPs@Fe3O4-NH2 possesses peroxidase-like activity, enabling it to undergo a colorimetric reaction 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 and leading to a distinct color change. When the 3D recognition cavities on the surface of MIPs@Fe3O4-NH2 specifically bind to PCA, they restrict the exposures of the nanozyme’s activity sites and hinder their contact with the chromogenic substrate, which decreases the absorbance of the system. Based on this phenomenon, it demonstrates a good linear relationship between the decrease in absorbance and the concentration of PCA within the range of 1 to 250 μM, with a detection limit of 0.84 μM. Notably, this method offers excellent selectivity, and presents a straightforward preparation process, allowing for easy visualization of detection results. Consequently, it provides a promising and versatile strategy for the subsequent development of colorimetric sensors based on molecular imprinted polymers.