Ultrasmall, water-soluble magnetite nanoparticles with high relaxivity for magnetic resonance imaging

Fengqin Hu, Keith W. MacRenaris, Emily A. Waters, Taiyang Liang, Elise A. Schultz-Sikma, Amanda L. Eckermann, Thomas J. Meade

Research output: Contribution to journalArticlepeer-review

136 Scopus citations


Ultrasmall (3, 4, 5, and 6 nm), water-soluble Fe3O4 magnetic 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 Fe3O4 nanoparticles were dispersed in phosphate buffered saline, fetal bovine serum, or calf bovine serum for 1 week. Furthermore, the new Fe3O4 nanoparticles 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 Fe3O4 nanoparticles 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 Fe3O4 nanoparticles have little effect on NIH/3T3 cell viability.

Original languageEnglish (US)
Pages (from-to)20855-20860
Number of pages6
JournalJournal of Physical Chemistry C
Issue number49
StatePublished - 2009

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • General Energy
  • Surfaces, Coatings and Films
  • Physical and Theoretical Chemistry


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