The immobilization strategy between ZIF-8 and different
enzymes
has focused on in situ encapsulation and pore infiltration, while
the surface attachment has been seldom reported because of less functional
groups on the ZIF-8 surface. Here, a magnetic amine-functionalized
ZIF-8 with hierarchical pores was designed for efficient covalent
immobilization of α-amylase (α-Amy). By using Fe3O4 nanoparticles as the core and ZIF-8 as the shell, followed
by Au3+–Zn2+ exchange reaction and β-mercaptoethylamine
modification, the magnetic hollow ZIF-8 nanoparticle with amine groups
on the surface was synthesized. With the assistance of glutaraldehyde,
an α-Amy-magnetic hollow ZIF-8 composite was prepared and fully
characterized by scanning electron microscopy, transmission electron
microscopy, Fourier transform infrared spectrometry, X-ray photoelectron
spectroscopy, energy-dispersive X-ray spectroscopy element mapping
analysis, and vibration sample magnetometry. Then, the catalytic activity
of immobilized α-Amy was explored with a K
m of 2.307 mg/mL and V
max of 0.506
mg/mL·min, indicating excellent catalytic activity. The study
about stability and reusability demonstrated that the catalytic activity
of immobilized α-Amy remained above 50% after 10 times of reuse.
Thus, the designed magnetic amine-functionalized ZIF-8 was verified
to be a nice carrier for covalent enzyme immobilization.