Synthesis and characterization of a novel catalyst based on magnetic chitosan beads for oxidoreductase enzyme biomimetic immobilization

Enzymes are biological catalysts intensively researched in several fields, including wastewater treatment. However, the structural vulnerability of enzymes limits their application. The design of enzyme mimetics is an interesting challenge in terms of selecting appropriate support for a (bio)mimetic and maintaining activity and stability after immobilization. In this work, a novel spherical solid composed of chitosan and magnetite nanoparticles was formulated to support hematin (as an oxidoreductase biomimetic). Magnetic chitosan beads were prepared via coprecipitation and gelification of Fe₃O₄ nanoparticles and chitosan, respectively. The solid combines chitosan advantages (non-toxicity, abundance, physicochemical stability, and flexibility to be shaped into beads) with nanoparticulated Fe₃O₄ properties (superparamagnetism and oxidoreductase mimic activity). A black solid with a regularly spherical shape, approximately 2 mm in diameter, was obtained. The solid was able to support hematin. Under optimal conditions, the incorporation of 3-aminopropyltriethoxysilane increased hematin immobilization efficiency. The synthesized solid presents catalase activity, decomposing 56% of hydrogen peroxide under optimal conditions, while without hematin, it only decomposes 33%. The solid presented catalytic activity and low leaching of iron in reaction medium, which makes it a potential catalyst to be applied in wastewater remediation in future work.