Fabrication of highly porous, functional cellulose-based microspheres for potential enzyme carriers

Here, we present highly porous, cellulose-based microspheres using (2,2,6,6-tetramethylpiperidine-1-oxyl) TEMPO-oxidized cellulose fibers (TOCFs) as starting materials. The TOCFs were first dissolved in a NaOH/urea solvent and transformed into microspheres via an emulsification method. The carboxyl groups on the surface of TOCFs were successfully carried on the cellulose-based microspheres, which provides them numerous reacting or binding sites, allowing them to be easily functionalized or immobilized with biomolecules for multi-functional applications. Furthermore, the introduction of magnetic nanoparticles awards these microspheres magnetic properties, allowing them to be attracted by a magnetic field. As a proof of concept, we demonstrate the application of using these carboxylate cellulose-based microspheres for enzyme immobilization. The cellulose-based microspheres can successfully create stable covalent bonds with enzymes after the activation of carboxyl groups. The enhanced pH tolerance, thermal stability, convenient recovery, and reusability position the emulsified microspheres as promising carriers for enzyme immobilization.