Enzyme nanocapsules armored by metal-organic frameworks: A novel approach for preparing nanobiocatalyst

Abstract A promising approach was developed to fabricate nanobiocatalysts through the combination of enzyme nanocapsules (enzyme encapsulated in a polymer nanocapsule by an in situ free-radical polymerization technique) with metal-organic frameworks encapsulation. Catalase (CAT) was chosen as the model enzyme. The nanobiocatalyst (nCAT@ZIF-8) was synthesized first by in situ polymerization around CAT molecules (nanocapsules of CAT, denoted as nCAT) and a subsequent MOFs encapsulation process. The obtained nCAT@ZIF-8 was characterized by transmission electron microscopy, scanning electron microscopy, confocal laser scanning microscopy et al. nCAT@ZIF-8 showed improved thermal stability, reusability and storage stability than the free CAT, nCAT and CAT encapsulated in ZIF-8 by co-precipitation method (CAT@ZIF-8). After incubation at 65 °C for 60 min, nCAT@ZIF-8 can retain 78.79% of its original activity, which was better than that of nCAT (48.95%), CAT@ZIF-8 (40.38%) and free CAT (5.774%). After recycling 10 times, nCAT@ZIF-8 can retained 87.12% of its original activity, while CAT@ZIF-8 only remained about 65% of its original activity. nCAT@ZIF-8 retained 95.96% of original activity after 28 days of storage, which was also better than that of free CAT, CAT@ZIF-8 and nCAT. In addition, the versatility of this approach was validated by using penicillin G acylases (PGA) and the obtained PGA nanobiocatalyst also showed excellent catalytic performance.