Hybrid materials achieved by polypeptide grafted magnetite nanoparticles through a dopamine biomimetic surface anchored initiator

Abstract

Herein we report the preparation of well-defined hybrid materials based on magnetite nanoparticles coated with a polypeptide shell attached covalently through dopamine. Highly crystalline and hydrophobic magnetite nanoparticles have been modified at the surface using a biomimetic adhesive, dopamine, which provides the magnetite particles with primary amine groups. Hybrid magnetite–polypeptide systems have been, then, obtained by ring opening polymerization (ROP) of γ-benzyl-L-glutamate N-carboxyanhydride. These core–shell nanoparticles, magnetite–polypeptide, constitute an interesting alternative to other magnetite–polymer structures (PEG or dextran) because they present the following advantages: (1) the stability provided by a polypeptide shell covalently bonded to the magnetite surface through a dopamine anchor molecule instead of other non-covalent interactions; (2) the posterior chain deprotection of a poly(γ-benzyl-L-glutamate) (PBLG) shell transforms the system into magnetite–poly(glutamic acid) nanoparticles (PLGA), with high stability in aqueous solutions and a large amount of carboxylic acid groups; and (3) the easiness to incorporate compounds with biological activity into the PBLG structure, for instance, by loading procaine by aminolysis reaction. Therefore, the magnetite–PBLG nanoparticles depicted herein can be potentially employed as magnetic drug carriers or as scaffolds to engineer more complex hybrid materials. The structure and composition of these systems have been extensively characterized.