Recyclable magnetic nanoparticle grafted with pH-responsive polymer for adsorption with DNA

Magnetite nanoparticles (MNPs) grafted with positively charged poly(2-(diethylamino) ethyl methacrylate (PDEAEMA) were prepared via a combination of atom transfer radical polymerization (ATRP) and click reaction and used as recyclable nanosupports for adsorption with DNA. Alkyne-terminated PDEAEMA was synthesized via ATRP and then grafted to azide-functionalized MNPs. Quaternized PDEAEMA-grafted MNPs were used as recyclable nanosupports for adsorption with negatively charged DNA via electrostatic interactions. The particles with the size of 3-8 nm in diameter were well dispersible in water. They responded to the change in their solution pH as observed by a consistent decrease in hydrodynamic size when solution pH changed from basic to acidic pH. Recycling efficiency of the MNPs was investigated by determining the percent adsorption of the particles after multiple cycles of the adsorption-separation-desorption process. Adsorption ability of the MNPs to T-9 DNA tagged with fluorescein at 5'-position (FAM-dT(9)) retained higher than 80 % after 5-recycling process, indicating that these novel positively charged MNPs might be efficiently used as magnetic nanosupports for any negative biomolecules with good recycling efficiency.