Synthesis of post-modified poly(ester-amino) microspheres via aza-Michael precipitation polymerization and its use for enzyme immobilization

Uniform poly(ester-amino) microspheres (PEAs) were prepared by catalyst-free aza-Michael addition precipitation polymerization of trihydroxymethylpropyl triacrylate (TMPTA) and piperazine (PA) in acetonitrile. The effects of monomer feed ratio and concentration, polymerization temperature, and time on the size and morphology of PEAs were investigated. Monodisperse PEAs with size about 4 μm were successfully obtained at 2/3 molar ratio of TMPTA/PA and 4°C. The chemical structure of PEAs was characterized. There were amount of unreacted acrylate groups remained on the surface of PEAs prepared at the imino/acrylate molar ratio of 1/1.1, which provide lots of active sites for further chemical modification, especially for bioactivator immobilization. Laccase was used as an example to determine bio-immobilization activity of PEAs. Immobilized laccase exhibited higher tolerance to pH and temperature. The immobilized laccase was used as biocatalyst for degradation of Malachite Green. About 53% of its initial catalytic activity was retained after 4 cycles of reuse.