PEG coating reduces NMR relaxivity of Mn0.5Zn0.5Gd0.02Fe1.98O4 hyperthermia nanoparticles
✍ Scribed by Bashar Issa; Shahnaz Qadri; Ihab M. Obaidat; Richard W. Bowtell; Yousef Haik
- Publisher
- John Wiley and Sons
- Year
- 2011
- Tongue
- English
- Weight
- 965 KB
- Volume
- 34
- Category
- Article
- ISSN
- 1053-1807
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✦ Synopsis
Abstract
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~0.5~Zn~0.5~Gd~0.2~Fe~1.98~O~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^ m__M__^−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. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.