GEI is a group of water soluble iron oxide nanoparticles with amphiphilic polymer and polyethylenimine (PEI) coating. There is no linkable reactive group on the surface of nanoparticles. The zeta potential of GEI is about +50 mV. Their organic layers consist of a monolayer of dodecanethiol, a monolayer of amphiphilic polymer and a monolayer of PEI. The total thickness of the organic layers is about 10 nm. The hydrodynamic size of the nanoparticles is about 20 nm larger than their inorganic core size measured by TEM.
GEI is very stable in most buffer solutions in the pH range of 5-10 and can survive autoclaving process (121 °C for 30 min).
GEI can capture negatively charged molecules, such as DNA, RNA, through charge-charge interaction.