Effect of the Structure and Length of Flexible Chains on Dendrimers Grafted Fe₃O₄@SiO₂/PAMAM Magnetic Nanocarriers for Lipase Immobilization

Polyamidoamine (PAMAM) dendrimers have been widely applied in biomacromolecule immobilization, catalysis carriers, gene therapy, and drug delivery. However, there is still a lack of systematic research about lipase and protein immobilized by PAMAM dendrimers. Herein, we used three types of amine reagents to graft dendritic macromolecules on Fe₃O₄ nanoparticles and obtained a variety of Fe₃O₄@SiO₂/PAMAM magnetic nanocarriers with different generations. The density of surface functional groups, the structure, and the length (generation) of the flexible chain play an important role in immobilizing Candida rugosa lipase (CRL). As a result, hexamethylenediamine (HMD) grafted dendritic magnetic carriers with the fourth generation (Gc-4) exhibited a superior performance in terms of immobilizing CRL. Then, polyethylenimine (PEI) instead of HMD was grafted to the Gc-4 to obtain a higher activity with respect to immobilized CRL (955.53 U/g) and free lipase. Furthermore, the immobilized CRL improved its tolerability performance in wider ranges of pH and temperature.