Embedding Dual-Responsive Polymer@Enzyme in Zeolitic Imidazolate Frameworks with a Hollow Space for Improving Its...

Area of Science:

• Materials Science
• Biocatalysis
• Nanotechnology

Background:

• Enzyme immobilization in porous materials often faces challenges in maintaining catalytic activity, stability, and tolerance to harsh conditions.
• Zeolitic imidazolate framework-8 (ZIF-8) offers a promising porous structure for enzyme encapsulation but requires strategies to enhance enzyme performance.
• Stimuli-responsive polymers can offer dynamic control over the microenvironment, potentially improving enzyme function.

Purpose of the Study:

• To develop a stimuli-responsive polymer-support and sacrificial template strategy for fabricating hollow ZIF-8 composites.
• To modulate enzyme conformation freedom and generate nanoconfinement for improved catalytic performance, tolerance, and stability.
• To investigate the potential of these smart composites for enzyme activity evaluation in biological systems.

Main Methods:

• Synthesis of a thermo- and pH-responsive polymer via reversible addition-fragmentation chain transfer polymerization.
• Immobilization of alanine aminotransferase (AAT) onto the smart polymer via chemical bonding.
• Fabrication of hollow ZIF-8 composites (HSZIF-8) using pluronic F-127 as a sacrificial template and in situ ZIF-8 shell growth.

Main Results:

• The fabricated smart polymer@AAT@HSZIF-8 composites exhibited a 13.92-fold enhancement in catalytic activity compared to free AAT under specific conditions (45.0 °C, pH 4.5).
• The smart polymer acted as a 'tunable switch,' altering morphology with temperature and pH to create nanoconfinement, thereby improving enzyme performance.
• The composites demonstrated outstanding stability against harsh pH, heating, and organic solvents, and were successfully applied in evaluating AAT activity in mouse organs.

Conclusions:

• The study successfully demonstrates a novel strategy for creating enzyme-loaded hollow ZIF-8 composites with enhanced catalytic activity and stability.
• The integration of stimuli-responsive polymers and nanoconfinement within MOFs is crucial for improving enzyme performance.
• These smart MOF-based carriers show significant potential for practical bioapplications in real biological systems.