Colloidal stability of amino acid coated magnetite nanoparticles in physiological fluid

We investigated the surface charge effect of surface coating ligands on the colloidal stability of magnetite nanoparticles in a physiological saline solution. We employed the l-lysine and the l-glutamic acid as the surface coating ligands. We investigated the colloidal stability of the l-lysine and the l-glutamic acid coated magnetite nanoparticles by measuring their precipitation times, hydrodynamic diameter distributions, and zeta potentials in a physiological saline solution. From these three measurements, we found that the l-lysine coated magnetite nanoparticles are more stable as colloids than the l-glutamic acid coated magnetite nanoparticles. Based on the bonding structures of the l-lysine and the l-glutamic acid to magnetite nanoparticles, we successfully discussed the colloidal stability in terms of the surface charge effect of the amino acids.