PEG coating reduces NMR relaxivity of Mn 0.5Zn 0.5Gd 0.02Fe 1.98O 4 hyperthermia nanoparticles

Bashar Issa, Shahnaz Qadri, Ihab M. Obaidat, Richard W. Bowtell, Yousef Haik

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)


Purpose: To investigate both T1 and T2 MR relaxation enhancement of Gd substituted Zn-Mn ferrite magnetic nanoparticles. Both uncoated and polyethylene glycol (PEG) coated particles were used. Materials and Methods: Chemical co-precipitation was used to synthesize particles in the form Mn 0.5Zn 0.5Gd 0.2Fe 1.98O 4 suitable for hyperthermia applications. Physical characterization of the magnetic nanoparticles included SEM, TEM, ICP, and SQUID. T1 and T2 measurements were performed at 1.5 Tesla (T). Results: The saturation magnetization was 12.86 emu/g while the particle's magnetic moment was 1.86 × 10 -19 J/T. The particle size increased due to coating, while 1/T1 and 1/T2 relaxivities (26°C) decreased from 2.5 to 0.7 and from 201.3 to 76.6 s -1 mM -1, respectively, at a magnetic field 1.5T. Conclusion: The reduction in both 1/T1 and 1/T2 is attributed to increased distance of closest approach between the protons and the magnetic core caused by the shielding provided by the high molecular weight PEG. 1/T2 data are compared with existing theoretical models using a modified radius that takes into account both possible agglomeration of the particles and increased inter-particle separation induced by PEG coating.

Original languageEnglish
Pages (from-to)1192-1198
Number of pages7
JournalJournal of Magnetic Resonance Imaging
Issue number5
Publication statusPublished - Nov 2011


  • NMR relaxation
  • coating
  • contrast agents
  • nanoparticles
  • susceptibility

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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