Biomimetic iron-imidazole sites into metal organic framework nanoflowers as high-affinity peroxidase mimic for colorimetric biosensing

Abstract

The active site of natural horseradish peroxidase (HRP) comprises iron coordinated equatorially by a porphyrin ring and axially by the imidazole group of His170. The low water solubility of porphyrin rings inspired us to investigate the potential of the iron-imidazole group as peroxidase mimic. Herein, iron-imidazole (Fe-MIM) was one-pot constructed using ascorbic acid stabilized Fe2+ and 2-methylimidazole in the presence of zinc acetate at room temperature in aqueous medium, along with the formation of ZIF-8 framework around Fe-MIM sites. Fe-MIM/ZIF-8 was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller surface measurements. Fe-MIM/ZIF-8 exhibits high peroxidase-like activity, efficiently catalyzing the redox reaction between H2O2 and 3, 3′, 5, 5′-tetramethylbenzidine, as made evident by the appearance of a UV–Vis signal at 652 nm. Fe-MIM/ZIF-8 displays higher catalytic activity than the material (Fe + MIM) prepared by ascorbic acid stabilized Fe2+ and MIM, due to its rich biomimetic architecture and large BET surface area. The Km of Fe-MIM/ZIF-8 for H2O2 was 28 μM, which is 132 and 98 times lower than those of HRP and hemin (ironIII porphyrin), respectively. This low Km value indicates the strong affinity of Fe-MIM/ZIF-8 for H2O2, which proves the superiority of biomimetic Fe-MIM sites and suggests Fe-MIM/ZIF-8′s potential for H2O2-related biosensing. The highly sensitive colorimetric methods for H2O2 and H2O2-related glucose detection has been proposed. The applicability of this method to glucose detection in serum samples was tested with satisfactory results.