title: Synthesis of superparamagnetic nanotubes as MRI contrast agents and for cell labeling.
abstract: OBJECTIVE
  Magnetic nanoparticles have been studied widely as MRI contrast agents to increase the sensitivity of this technique. This work describes the synthesis and characterization of magnetic nanotubes (MNTs) as a novel MRI contrast agent.
  
  
  METHODS
  MNTs with high saturation magnetization were fabricated by the synthesis of superparamagnetic iron oxide nanoparticles (SPIONs) directly in the pores of silica nanotubes (SNTs). The MNTs were characterized by electron microscopy, superconducting quantum interference device and MRI. Preliminary studies on in vitro cytotoxicity and cell labeling were carried out.
  
  
  RESULTS
  The MNTs retained the superparamagnetic characteristics in bulk solutions with a considerably high saturation magnetization of 95 emu/gFe. The nuclear magnetic resonance (NMR) relaxivities for MNTs of 500 nm in length and of 60 nm in diameter were r(1) = 1.6 +/- 0.3 mM(-1)s(-1) and r(2) = 264 +/- 56 mM(-1)s(-1) and, for the MNTs of 2 microm in length and 70 nm in diameter, the r(1) and r(2) were 3.0 +/- 1.3 and 358 +/- 65 mM(-1)s(-1), respectively. In vitro cell labeling showed promising results with excellent labeling efficiency. No cellular toxicity was observed in vitro.
  
  
  CONCLUSIONS
  The integration of SPIONs with SNTs imparts the superparamagnetic characteristics of SPIONs onto the SNTs, creating unique magnetic nanoparticles with multifunctionality. The MNTs showed promising results as a MRI contrast agent with high NMR relaxivities, little cytotoxicity and high cell-labeling efficiency.
authors: University of Maryland College Park, Department of Chemistry & Biochemistry, MD 20742, USA.
authors: Xia
authors: X
authors: Bai
authors: Sang Jun
authors: SJ
authors: Son
authors: Shixiong
authors: S
authors: Zhang
authors: Wei
authors: W
authors: Liu
authors: Elaine K
authors: EK
authors: Jordan
authors: Joseph A
authors: JA
authors: Frank
authors: Thirumalai
authors: T
authors: Venkatesan
authors: Sang Bok
authors: SB
authors: Lee
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects*; D003287:Contrast Media / Q000008:administration & dosage*; D052203:Ferrosoferric Oxide / Q000008:administration & dosage; D005910:Glioma / Q000473:pathology*; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D043942:Nanotubes; D051381:Rats; D013194:Staining and Labeling
chemical_list: D003287:Contrast Media; C427127:superparamagnetic blood pool agent; D052203:Ferrosoferric Oxide