Biomimetic iron-imidazole sites into metal organic framework nanoflowers as high-affinity peroxidase mimic for colorimetric biosensing
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 Fe 2+ 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 H 2 O 2 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 Fe 2+ and MIM, due to its rich biomimetic architecture and large BET surface area. The K m of Fe-MIM/ZIF-8 for H 2 O 2 was 28 μM, which is 132 and 98 times lower than those of HRP and hemin (iron III porphyrin), respectively. This low K m value indicates the strong affinity of Fe-MIM/ZIF-8 for H 2 O 2 , which proves the superiority of biomimetic Fe-MIM sites and suggests Fe-MIM/ZIF-8′s potential for H 2 O 2 -related biosensing. The highly sensitive colorimetric methods for H 2 O 2 and H 2 O 2 -related glucose detection has been proposed. The applicability of this method to glucose detection in serum samples was tested with satisfactory results.
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