Fabrication of polymer functionalized Mn2+-tannic acid coatings on magnetism-responsive nano-microspheres for Immobilized Penicillin G acylase

Firstly, Fe3O4 nanoparticles (Fe3O4 NPs) were synthesized by the inverse microemulsion method, and then, Mn2+ was doped in the process of coating tannin(TA) on the surface of Fe3O4 NPs to obtain Mn2+-Fe3O4@PTA NPs. The composite carrier containing Mn2+ could activate the catalytic activity of immobilized Penicillin G acylase (PGA). After the GMA was introduced into the carrier surface by ring-opening reaction, the above preparation carrier was modified by introducing RAFT reagent to obtain Mn2+-Fe3O4@PTA-GMA-g-RAFT NPs. Lastly, glycidyl methacrylate (GMA) and methyl methacrylate (MMA) were employed as the target monomer and the monomer for regulating the spacing between the targets, respectively. Herein, PGA was covalently immobilized on the surface of the magnetic microspheres by reaction of the amino groups of the PGA molecules with the epoxy groups of the magnetic polymer microspheres. Selections of immobilization conditions, including enzyme concentration, pH, temperature, and time of immobilization, were explored. The condition under which enzyme loading capacity (ELC), enzyme activity (EA), and enzyme activity recovery (EAR) of immobilized PGA were maximized as follows: enzyme concentration 2.5 vol%, pH = 8.0, time 20 h, and temperature 37 °C. Under the optimal immobilization conditions, ELC, EA, and EAR of immobilized PGA were 120 mg/g, 31,361 U/g, and 93.7%, respectively. Immobilized PGA remained 90.1% of initial activity and the carrier recovery was 97.8% after 14 successive cycles. These results indicated that the biocatalytic systems with potential use in biomedical application by the influence of polyhydroxy groups, target spacing, and Mn2+.