Self-assembly of magnetite nanocrystals with amphiphilic polyethylenimine: structures and applications in magnetic resonance imaging.

Wang Z¹, Liu G, Sun J, Wu B, Gong Q, Song B, Ai H, Gu Z.

Author information

• ¹National Engineering Research Center for Biomaterials, Sichuan University, Chengdu 610064, PR China.

Abstract

Controlled self-assembly of magnetic nanocrystals has important applications in biomedical fields. In this study, hydrophobic superparamagnetic iron oxide （SPIO） nanocrystals are self-assembled into small clusters （mean diameter <100 nm） in water phase with the help of partially alkylated hyper-branched polycation, polyethylenimine （PEI）. The amphiphilic PEI can wrap one or multiple SPIO nanocrystals inside micelle cores depending on different polycation/SPIO mass ratios. These SPIO nanocrystal containing micelles are superparamagnetic at room temperature. At the magnetic field of 1.5 T, single SPIO nanocrystal containing micelles have a T2 relaxivity of 118 Fe mM（-1）s（-1）, while multiple SPIO nanocrystals micelles have relatively higher T2 relaxivities up to 323 Fe mM（-1）s（-1）. Next, these potential magnetic resonance imaging （MRI） probes are tested for labeling rabbit mesenchymal stem cells. The formulation with a low polymer/SPIO ratio （0.2） is biocompatible and effective in labeling. Under a clinical MRI scanner, 3 x 10（6） labeled cells in gelatin phantom present much darker images than controlled ones. The T2 relaxation rate of the labeled cells is approximately 74.2 s（-1）, significantly higher than the control cells of approximately 3.4 s（-1）. This new amphiphilic polycation/SPIO nanocomposite may provide opportunities in cell labeling and tracking their behaviors in vivo.

J Nanosci Nanotechnol. 2009 Jan;9（1）:378-85.

PMID: 19441322 [PubMed - indexed for MEDLINE]