Functionalization of magnetic nanoparticles with peptide dendrimers

Surface functionalization of magnetic nanoparticles (MNPs) has been an exciting area of interest for researchers in biomedicine. In this paper, we introduce a new family of peptide dendritic ligands for functionalizing MNPs of superior quality. L-Lysine- and L-glutamic acid-based dendritic ligands with dopamine located at the focal points were fully designed and synthesized before the functionalization. Then ligands of different dendritic generations (G1 to G3) were immobilized on the surface of oleic-acid-coated hydrophobic MNPs via ligand-exchange method to realize phase transfer. The two series of modified MNPs were systematically studied via FTIR, TGA, XRD, TEM, DLS, VSM and zeta potential measurements. The modified MNPs exhibited an adjustable number of terminal functional groups and superior stability in aqueous solutions in a broad pH range. The surface existence of water-soluble polypeptide ligands promoted monodispersity of the particles and led to an increased hydrodynamic diameter under 30 nm from G1 to G3. After the ligand exchange process, the superparamagnetic behavior was successfully retained. The two series of modified MNPs exhibited approximate magnetization in the same generation, while the saturation magnetization of the MNPs decreased with increasing surface dendritic generation. MNPs functionalized with G1 L-glutamic acid dendritic ligands had the highest saturation magnetization (55 emu g(-1)), which was larger than for the initial MNPs. This novel functionalization strategy provides a potential platform for designing and preparing highly stable ultrafine MNPs with high magnetization for biomedicinal applications.