Biomimetic mineralization-driven in situ encapsulation of cellulase into ZIF-8: Enhanced enzyme stability and pH-responsive release

Assembling protective metal-organic framework (MOF) coatings for structurally fragile natural enzymes broadens their potential industrial applications. In this study, we developed an enhanced two-step biomimetic mineralization strategy, whereby cellulase acts as a biological template to pre-concentrate Zn 2+ on its surface, subsequently initiating the rapid in situ formation of zeolitic imidazolate framework-8 (ZIF-8). This approach yields a cellulase@ZIF-8 composite that effectively combines enzyme activity retention with the structural robustness of the MOF. Cellulase actively mediated ZIF-8 nucleation and framework construction through precise interfacial coordination with imidazole ligands and Zn 2+ , thus achieving in situ encapsulation. Compared with free cellulase, cellulase@ZIF-8 maintained over 90 % residual activity under acidic conditions and over 60 % activity at 80 °C. Remarkably, under alkaline conditions (pH = 9) or after 30 days of storage, cellulase@ZIF-8 residual activity exceeded twice that of the free enzyme. Even after 10 recycles, cellulase@ZIF-8 retained 60.5 % residual activity, exhibiting outstanding environmental tolerance and reusability. Our results suggest that the spatial confinement provided by ZIF-8, along with its ability to induce conformational rearrangement in the enzyme, underlies the enhanced stability and environmental tolerance observed. We further showed a pH-responsive release of cellulase facilitated by the ZIF-8 framework, enabling burst release of >90 % cellulase in a short time under acidic environment. This work offers valuable insights into enzyme-MOFs design and their applications in biocatalysis, controlled release, and adaptive biomaterials.