Functionalization of γ-Fe2O3 nanoparticles through the grafting of an organophosphorous ligand

An organophosphorous ligand terminated by an amine group has been used here for the first time to functionalize gamma-Fe2O3 nanoparticles and to immobilize an enzyme onto their surface in a covalent way. The immobilization of beta-glucosidase onto the maghemite nanoparticles was carried in this work out via a reductive amination reaction pathway which involves the terminal amine group on the ligand. The enzymatic activity of the bound enzyme was evaluated in terms of the classical Michaelis-Menten kinetics. Indeed, the affinity of the bound enzyme for the substrate is preserved and is not affected by the high amount of enzymes onto the surface of the nanoparticles. Moreover, the related enzymatic activity slightly decreases compared to that of the free enzyme. Such functionalized nanoparticles could help to improve the delivery and the recovery of biomolecules in biomedical applications by using a magnetic field. They could also provide a magnetic support which could be involved as a contrast agent, a biological label and a mediator for magnetic hyperthermia. (C) 2008 Elsevier B.V. All rights reserved