Enzyme Stabilization and Catalytic Activity Enhancement by Single-Chain Nanoparticles of Fluorinated Zwitterionic Random Copolymers

To achieve convenient storage of bioactive materials such as protein enzymes (proteases) at ambient temperature, with both their spatial structure and biocatalytic activity well retained, is highly appealing but challenging. Herein, a variety of amphiphilic random copolymers have been well synthesized via reversible addition–fragmentation chain transfer (RAFT) copolymerization of sulfobetaine methacrylate (SBMA) and various length fluoroalkyl methacrylate monomers. By simultaneously introducing fluoroalkyl and zwitterionic segments in random copolymerization, such kinds of amphiphilic random copolymers combined the advantages of both polyzwitterionic and fluoropolymers, which were capable of constructing uniform tiny single-chain nanoparticles (SCNPs) of around 10 nm in a wide range of compositions and fabrication conditions from aqueous solutions. Through intramolecular self-folding of the fluorinated alkyl segments to constitute the compact inner cores and the superhydrophilic zwitterionic SBMA polymer segments forming the outer passivated layer, the thus obtained SCNPs exhibited remarkable enzyme stabilizing capability through morphological adjustment, hydration, and heterocoagulation mechanisms for the investigated glucose oxidase (GOx) and horse radish peroxidase (HRP), acting like artificial molecular chaperones. Moreover, enzyme catalytic activity enhancement in the HRP@SCNPs system was well demonstrated with a representative enzyme-catalyzed cascade oxidization reaction for the synthesis of an azobenzene chromophore. Therefore, this work provides a facile fabricating strategy for SCNPs from well-synthesized amphiphilic random copolymers via RAFT, which may serve as promising stabilizers for ambient temperature storage and activity preservation of proteases.