An enzyme-loaded reactor using metal-organic framework-templated polydopamine microcapsule

Ultrathin polydopamine microcapsules with hierarchical structure and porosity were prepared for the immobilization of multienzymes using metal-organic framework (MOF) as the template. The multienzyme/MOF composite was first prepared using a “one-pot” co-precipitation approach via the coordination and self-assembly of zinc ions and 2-methylimidazole in the presence of enzymes. The obtained nanoparticles were then coated with polydopamine thin layer through the self-polymerization of dopamine under alkaline condition. The polydopamine microcapsules with an ultrathin shell thickness of ~   48 nm were finally generated by removing the MOF template at acidic condition. Three enzymes were encapsulated in PDA microcapsules including carbonic anhydrase (CA), formate dehydrogenase (FateDH), and glutamate dehydrogenase (GDH). FateDH that catalyzed the main reaction of CO 2 reduction to formic acid retained 94.7% activity of equivalent free FateDH. Compared with free multienzymes, the immobilized ones embedded in PDA microcapsules exhibited 4.5-times higher of formate production and high catalytic efficiency with a co-factor-based formate yield of 342%.