Liu Menglong,Wang Ying,Xiao Jingyi,Liu Yiyao,Ren Yi,Gao Xue
Based on the peroxidase activity of Cu-hemin metal–organic framework (Cu-hemin MOF) nanozyme, a colorimetric enzyme-linked immunosensor was developed for the detection of furazolidone (FZD). Cu-hemin MOF is a bimetallic nanozyme that exhibited a stronger catalytic effect compared with single-metal organic framework nanoenzymes. Cu-hemin-MOF catalyzes hydrogen peroxide (H 2 O 2 ) to produce hydroxyl radicals (•OH), which oxidizes the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxidized TMB (oxTMB). The absorbance change is at 650 nm. The content of AOZ in animal food can be quickly and accurately determined by changes in absorbance. The linear range of the colorimetric biosensor for detecting FZD was 0.01 ~ 62.52 ng/mL, and the limit of detection was as low as 0.01 ng/mL. The recovery of spikes samples was in the range 94.2-108.0 % and reproducibility was less than 4.8%. In addition, the cross-reaction rate was less than 0.1% when detecting other metabolites except AOZ, indicating that the sensor has good applicability and specificity. This study not only provides a better understanding of the relationship between the dispersion of nanoenzymes and enzyme-like activity but also offers a general method for detecting antibiotics using the nanoenzyme colorimetric method.
Hemin as the organic linker ligand and Cu (II) as the metal center were applied to prepare a copper-metal-organic framework (Cu-hemin-MOF) via one-step hydrothermal method. Characterization using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD) demonstrate that the acquired Cu-hemin-MOF possesses the appearance of 3D ball-flower shape with the existence of C, N, O, Fe, and Cu on the surface. Further study found that this 3D ball-flower shaped Cu-hemin-MOF exhibits peroxidase-like activity, which can catalyze the peroxidase substrate of o-phenylenediamine (OPD) to generate 2,3-diaminophenazine (DAP) in the presence of H 2 O 2 . DAP has a yellow color and also emits a strong fluorescence when excited by ultraviolet light. Interestingly, Cu-hemin-MOF’s peroxidase-like activity can be strongly inhibited by glutathione (GSH). In view of this, a dual readout (fluorescence and colorimetry) was proposed to detect GSH for the first time. Under optimal conditions, the proposed method exhibits good linear relationship between the signal response (fluorescence and colorimetry) and the concentration of GSH, and low limits of detection (LOD) of 2.3 and 26.6 nM, respectively. Graphical abstract
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