Synthesis of brightly PEGylated luminescent magnetic upconversion nanophosphors for deep tissue and dual MRI imaging

Hongyu Chen, Bin Qi, Thomas Moore, Daniel C. Colvin, Thomas Crawford, John C. Gore, Frank Alexis, O. Thompson Mefford, Jeffrey N. Anker

Research output: Contribution to journalArticlepeer-review

61 Scopus citations


A method is developed to fabricate monodispersed biocompatible Yb/Er or Yb/Tm doped β-NaGdF4 upconversion phosphors using polyelectrolytes to prevent irreversible particle aggregation during conversion of the precursor, Gd2O(CO3)2•H 2O:Yb/Er or Yb/Tm, to β-NaGdF4:Yb/Er or Yb/Tm. The polyelectrolyte on the outer surface of nanophosphors also provided an amine tag for PEGylation. This method is also employed to fabricate PEGylated magnetic upconversion phosphors with Fe3O4 as the core and β-NaGdF4 as a shell. These magnetic upconversion nanophosphors have relatively high saturation magnetization (7.0 emu g-1) and magnetic susceptibility (1.7 × 10-2 emu g-1 Oe -1), providing them with large magnetophoretic mobilities. The magnetic properties for separation and controlled release in flow, their optical properties for cell labeling, deep tissue imaging, and their T1- and T2-weighted magnetic resonance imaging (MRI) relaxivities are studied. The magnetic upconversion phosphors display both strong magnetophoresis, dual MRI imaging (r1 = 2.9 mM-1 s -1, r2 = 204 mM-1 s-1), and bright luminescence under 1 cm chicken breast tissue. Multifunctional magnetic upconversion nanophosphors are developed with strong magnetic moments and bright upconversion luminescence for cell labeling and deep tissue imaging. These particles are also used to visualize a novel magnetic capture and release technique. Furthermore, these magnetic nanophosphors with gadolinium and iron contents are shown to be good dual-modal (T1 and T 2-weighted) MRI contrast agents.

Original languageEnglish
Pages (from-to)160-168
Number of pages9
Issue number1
StatePublished - 15 Jan 2014
Externally publishedYes


  • MRI
  • capture and release
  • deep tissue imaging
  • magnetic nanoparticles
  • upconversion nanophosphors


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