Absolute Mag™ PEG Coated Iron Oxide Nanoparticles, which are amphiphilic polymer and PEG coated, are water soluble iron oxide nanoparticles. They do not have any linkable reactive groups on the surface. Their zeta potential is from -10mV to 0. The organic layer is about 6 nm thickness and the hydrodynamic size is abouy 12-14 nm larger than their inorganic core size measured by TEM. Also Absolute Mag™ PEG Coated Iron Oxide Nanoparticles are expected to have high colloidal stability. They are stable in most buffer solutions with a pH ranges from 4-10, also they can survive autoclaving process (121°C for 30 min).