Facile molecular imprinting on magnetic nanozyme surface for highly selective colorimetric detection of tetracycline

Nanozymes have been intensively explored to develop analytical methods in the past decade. Nonetheless, most nanozymes lack the catalytic specificity toward substrates, which becomes the biggest barrier hindering their applications. How to achieve high-selectivity nanozyme sensing without the assistance of biological elements (aptamers, antibodies, etc.) is challenging. In this work, we introduced molecularly imprinted sites onto the Fe3O4 nanozyme surface via a facile process, and developed a colorimetric assay for the highly specific determination of tetracycline (TC). Self-polymerization of dopamine under mild conditions was employed to conveniently construct the proposed Fe3O4 @MIP, which possessed abundant channels for substrates access to the Fe3O4 core, showing a peroxidase-mimetic activity of catalyzing the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue species. When TC existed, it was specifically captured by the MIP shell and partially blocked the cavities for substrate access, and such that the catalyzed TMB chromogenic reaction was hampered. Based on the principle, highly selective colorimetric detection of TC against structural analogues was acquired, with a detection limit of 0.4 μM, and practical applications of the assay in environmental water matrices were also verified. Thanks to the magnetic characteristic, the molecularly imprinted nanozyme could be easily recovered and regenerated for recyclable sensing.