Monitoring of release of cargo from nanocarriers by MRI/MR spectroscopy (MRS): Significance of T2/T2* effect of iron particles

Yoshinori Kato, Dmitri Artemov

Research output: Contribution to journalArticle

Abstract

To monitor the release of cargo molecules from nanocarriers, a novel MRI/MRS technique was developed and tested. This novel approach uses a simultaneous encapsulation of super-paramagnetic iron oxide (SPIO) nanoparticles and either a gadolinium (Gd)-based paramagnetic contrast agent, Gd-diethylenetriamine pentaacetic acid bismethylamide(GdDTPA-BMA), for MRI, or an anticancer agent, 5-fluorouracil (5-FU), for MRS. These agents have significantly different diffusion properties due to their different molecular sizes. Strong negative signal enhancement due to the T2 effects of SPIO dominates the positive T1 contrast generated by GdDTPA-BMA when SPIO and GdDTPA-BMA are in close proximity (intact form). Positive T1 contrast becomes evident upon release of GdDTPA-BMA from the carrier once the distance between GdDTPA-BMA and SPIO molecules is beyond the T2 enhancement range. Similarly, intact nanocarriers loaded with 5-FU and SPIO have a broad 19F resonance line because line-width is inversely proportional to T2*, while free 5-FU appears as a narrow resonance line once it is released from the liposomes. This technique allowed monitoring of the release of cargo molecules from liposomes encapsulating both SPIO and either GdDTPA-BMA or 5-FU by MRI/MRS in vitro using 2% agarose gel phantoms. Experimental results demonstrate successful demarcation of the released cargo molecules vs. encapsulated molecules.

Original languageEnglish (US)
Pages (from-to)1059-1065
Number of pages7
JournalMagnetic resonance in medicine
Volume61
Issue number5
DOIs
StatePublished - May 1 2009

Keywords

  • 5-fluorouracil
  • Activated MR contrast agent
  • Dual contrast technique
  • Fe-based contrast agents
  • Gd-based contrast agents
  • MRI
  • MRS

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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