Three-dimensional ordered macro-microporous ZIF-8-α-Glu microreactors for α-glucosidase inhibitors screening from green tea.

Due to the larger pore structure, the macroporous material can be used as the immobilized carrier to not only increase the enzyme loading capacity, but also facilitate the transfer of reactants and substrates. Based on this, a three-dimensional ordered macro-microporous ZIF-8 (SOM-ZIF-8) was prepared using three-dimensional ordered stacked polystyrene spheres as the hard template. The morphology and structure of SOM-ZIF-8 were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and so on. The macropore size of SOM-ZIF-8 was tested to be about 100 nm by N adsorption-desorption isotherms. Then α-glucosidase (α-Glu) was encapsulated into the macropore of SOM-ZIF-8 by physical adsorption method to prepare the immobilized enzyme microreactor. Under the optimal immobilization conditions, the loading capacity of SOM-ZIF-8 to α-Glu reached 113.42 μg/mg. Due to the encapsulation in the three-dimensional macropores, the conformational changes of the enzyme are restricted, endowing the immobilized enzyme with excellent acid and alkali resistance, a long storage time, and almost unchanged relative activity after 7 cycles. Finally, the SOM-ZIF-8-α-Glu microreactors combined with high performance liquid chromatography (HPLC) were applied to offline screen α-Glu inhibitory active components from tea extract. Several components including gallocatechin, catechin and epicatechin gallate were successfully screened out, which verified the application feasibility of the immobilized enzyme microreactor.