Oleic Acid-Coated Magnetite Nanoparticles Synthesis

Oleic acid coated magnetite nanoparticles (NP-OA) were synthesized via thermal decomposition of iron oleate complex.[5 (link)] To a 5 ml of toluene solution containing 50 mg (iron content) of NP-OA, 40 mL of acetone was added, and the nanoparticles were collected by centrifugation. The nanoparticles were redispersed in 50 mL anhydrous toluene and transferred to a three-neck flask equipped with a heater. After the system was sealed and purged with nitrogen, 0.15 mL of SAS was injected, and the solution was heated to 100°C for 12 hours. The nanoparticles were precipitated by the addition of hexane, and collected using a rare earth magnet. The nanoparticles were washed twice with hexane and redispersed in anhydrous tetrahydrofuran (THF). To this solution, 100 mg of H₂NPEG-NH₂ and 2.5 mg of N,N′-dicyclohexylcarbodiimide (DCC) were added, and the reaction mixture was sonicated in a sonication bath for 12 hrs at 25°C. The nanoparticles was precipitated by the addition of 200 mL of hexane, and collected using a rare earth magnet. The precipitated nanoparticles were redispersed in 50 mL of anhydrous THF, and 250 mg of PEG-bis(amine) and 12.5 mg of DCC were added. The reaction mixture was kept in a sonication bath for 16 hrs at 25°C. The resulting product was precipitated by the addition of hexane, and collected using a rare earth magnet. After two additional cycles of THFredispersion and ether-precipitation, the residue solvent was evaporated and the nanoparticles were redispersed in 5 mL PBS. After passing through a 0.2 μm syringe filter, the nanoparticles were purified through gel filtration chromatography by Sephacryl S-200 column. The nanoparticles were stored in 0.1 M sodium bicarbonate buffer (pH 8.5). The concentration of nanoparticles was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES).