Magnetic covalent organic framework nanospheres with enhanced peroxidase-like activity for colorimetric detection of H2O2 and glucose

The nanomaterials-based artificial enzymes have attracted great attention because of their high stability, good biocompatibility, high catalytic efficiency, and low cost in recent years. Herein, we synthesized a new covalent organic framework (COFs) through the dehydration reaction of 2,5-dihydroxyterephthalaldehyde and tetra-(4-aminophenyl) porphyrin, which was then used to fabricate the core-shell structured nanospheres (Fe3O4 @COFs) by decorating on magnetic Fe3O4. In the presence of hydrogen peroxide (H2O2), the Fe3O4 @COFs nanospheres were able to catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue product (ox-TMB), indicating their high peroxidase-like activity. Based on this phenomenon, the Fe3O4 @COFs was used as a colorimetric probe for sensitive and selective detection of H2O2 and glucose. The detection limit (LOD) of H2O2 was calculated to be 2.6 μM in a linear range from 0.1 to 4 mM, while the LOD of glucose was valued as 6 μM ranging from 0.05 to 0.9 mM. Finally, this method was applied in the determination of the glucose concentration in human serum with high accuracy. Thus, the as-prepared Fe3O4 @COFs could be used as a highly sensitive and selective peroxidase mimic to detect hydrogen peroxide-related molecules, suggesting their great potential in biomedical application.