Immobilization of trypsin onto polyamidoamine dendrimer functionalized iron oxide nanoparticles and its catalytic behavior towards spirooxindole-pyran derivatives in aqueous media

A novel biocatalyst of trypsin (Fe 3 O 4 @SiO 2 @D-NHCS-Tr) was prepared based on PAMAM dendrimer immobilized on the surface of magnetic nanoparticles. Then, the catalyst performance was evaluated by the green synthesis of spirooxindole-pyran derivatives for the first time.In the first step, Magnetic Fe 3 O 4 nanoparticles prepared by the co-precipitating method were coated with a layer of silica. Afterward, the PAMAM dendrimer was grown step by step on the surface of the magnetic nanoparticles. Finally, the trypsin enzyme was immobilized via CS 2 as a cross-linker on the dendrimer surface. Successful steps synthesis of Fe 3 O 4 @SiO 2 @D-NHCS-Tr was examined and characterized by FT-IR, XRD, TGA, EDX, TEM, and SEM analyses. Briefly, this catalyst is easyto separate, recycle and reusable and has shown excellent performance in chemical reactions in terms of time and efficiency in the water solvent. It is hoped that this catalyst could serve as a candidate for industrial applications to be in the future.