title: Ultrasmall, Water-Soluble Magnetite Nanoparticles with High Relaxivity for Magnetic Resonance Imaging.
abstract: Ultrasmall (3, 4, 5, and 6 nm), water-soluble Fe3O4magnetic nanoparticles were synthesized in diethylene glycol (DEG) via a facile one-pot reaction. Hydrodynamic size and relaxation time measurements did not show particle aggregation when Fe3O4nanoparticles were dispersed in phosphate buffered saline, fetal bovine serum, or calf bovine serum for 1 week. Furthermore, the new Fe3O4nanoparticles tolerated high salt concentrations (≤1 M NaCl) and a wide pH range from 5 to 11. Surface modification of the nanoparticles with poly(ethylene glycol) bis(carboxymethyl) ether (HOOC-PEG-COOH, 600 g/mol) was accomplished through a ligand-exchange reaction. The effects of PEG modification on magnetization and relaxivity of the Fe3O4nanoparticles were investigated, and the results indicate that the increase in transverse relaxivity after PEG modification may be due to the increased volume of slowly diffusing water surrounding each nanoparticle. In vitro experiments showed that the DEG- and PEG-coated Fe3O4nanoparticles have little effect on NIH/3T3 cell viability.
authors.affiliation: Department of Chemistry, Biochemistry, Molecular Biology and Cell Biology, Neurobiology and Physiology, Radiology, Northwestern University, Evanston, Illinois 60208.
authors.forename: Fengqin
authors.initials: F
authors.lastname: Hu
authors.affiliation: Department of Chemistry, Biochemistry, Molecular Biology and Cell Biology, Neurobiology and Physiology, Radiology, Northwestern University, Evanston, Illinois 60208.
authors.forename: Keith W
authors.initials: KW
authors.lastname: MacRenaris
authors.affiliation: Department of Chemistry, Biochemistry, Molecular Biology and Cell Biology, Neurobiology and Physiology, Radiology, Northwestern University, Evanston, Illinois 60208.
authors.forename: Emily A
authors.initials: EA
authors.lastname: Waters
authors.affiliation: Department of Chemistry, Biochemistry, Molecular Biology and Cell Biology, Neurobiology and Physiology, Radiology, Northwestern University, Evanston, Illinois 60208.
authors.forename: Taiyang
authors.initials: T
authors.lastname: Liang
authors.affiliation: Department of Chemistry, Biochemistry, Molecular Biology and Cell Biology, Neurobiology and Physiology, Radiology, Northwestern University, Evanston, Illinois 60208.
authors.forename: Elise A
authors.initials: EA
authors.lastname: Schultz-Sikma
authors.affiliation: Department of Chemistry, Biochemistry, Molecular Biology and Cell Biology, Neurobiology and Physiology, Radiology, Northwestern University, Evanston, Illinois 60208.
authors.forename: Amanda L
authors.initials: AL
authors.lastname: Eckermann
authors.affiliation: Department of Chemistry, Biochemistry, Molecular Biology and Cell Biology, Neurobiology and Physiology, Radiology, Northwestern University, Evanston, Illinois 60208.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Meade