http://www.cd-bioparticles.com/p/PEI-Magnetic-Particles_20_196_248_437.htmlAbsolute Mag PEI Magnetic Particles, 100 nm (# WHM-X070) are water soluble iron oxide particles with organic layers consist of a monolayer of oleic acid, a monolayer of amphiphilic polymer and a monolayer of polyethylenimine (PEI). There is no linkable reactive groups on the surface of nanoparticles. PEI is very stable in most buffer solutions of pH 5-10 and can capture negatively charged molecules, such as DNA and RNA, through charge-charge interaction.DNA/RNA Purification