title: PEG coating reduces NMR relaxivity of Mn(0.5)Zn(0.5)Gd(0.02)Fe(1.98)O4 hyperthermia nanoparticles.
abstract: OBJECTIVE
  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.
  
  
  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) mM(-1), respectively, at a magnetic field 1.5T.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Physics, College of Sciences, United Arab Emirates University, Al Ain, UAE. b.issa@uaeu.ac.ae
authors.forename: Bashar
authors.initials: B
authors.lastname: Issa
authors.forename: Shahnaz
authors.initials: S
authors.lastname: Qadri
authors.forename: Ihab M
authors.initials: IM
authors.lastname: Obaidat
authors.forename: Richard W
authors.initials: RW
authors.lastname: Bowtell
authors.forename: Yousef
authors.initials: Y
authors.lastname: Haik
mesh_terms: D020099:Coated Materials, Biocompatible; D003460:Crystallization; D005682:Gadolinium / Q000737:chemistry; D005782:Gels / Q000737:chemistry; D006979:Hyperthermia, Induced / Q000379:methods*; D007501:Iron / Q000737:chemistry; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008345:Manganese / Q000737:chemistry; D008855:Microscopy, Electron, Scanning / Q000379:methods; D046529:Microscopy, Electron, Transmission / Q000379:methods; D015233:Models, Statistical; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D010100:Oxygen / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry*; D012685:Sepharose / Q000737:chemistry; D013696:Temperature; D015032:Zinc / Q000737:chemistry
chemical_list: D020099:Coated Materials, Biocompatible; D005782:Gels; D011092:Polyethylene Glycols; D008345:Manganese; D012685:Sepharose; D005682:Gadolinium; D007501:Iron; D015032:Zinc; D010100:Oxygen