Surface PEGylation and ligand exchange chemistry of FePt nanoparticles for biological applications

FePt magnetic nanoparticles (MNPs) were functionalized with a mixed monolayer of poly(ethylene glycol)-terminated thiol and dopamine ligands. The resulting nanoparticles were soluble and stable in aqueous media, including water, ionic solutions, and cell culture medium. The surface thiol ligands are readily exchanged with other thiols bearing chain-end functionalities. MNPs featuring either a cationic or an anionic surface were synthesized by ligand exchange chemistry to afford ligand peripheries capable of binding biomolecules. Surface binding of cationic MNPs to DNA and anionic MNPs to chymotrypsin was enabled by incorporation of a charged functionality on the nanoparticle surface. This approach represents a general strategy to synthesize functionalized FePt nanoparticles that form stable solutions in water and facilitates the use of these magnetic FePt nanoparticles in biological applications.