Silica-coated superparamagnetic iron oxide nanoparticles targeting of EPCs in ischemic brain injury

Long-term effects of magnetically targeted ferumoxide-labeled human neural stem cells in focal cerebral ischemia

The long-term effect of magnetically targeted neural stem cells in a rat focal cerebral ischemia model was investigated. In middle cerebral artery occlusion (MCAO) stroke model rats, ferumoxide-labeled human neural stem cells (hNSCs) were injected into the tail vein. MCAO rats were divided into three groups: ischemia only (IO), ischemia with NSC injection (IC), and ischemia with NSC injection and the use of magnet targeting (IM). Four weeks after MCAO and 3 weeks posttransplantation, a greater number of hNSCs were found in ischemic lesion sites in IM rat brain compared with IO and IC animals. In addition, differentiation of hNSCs into neurons or astrocytes and angiogenesis were markedly increased. In IM rats, infarct volume was considerably reduced, and function was significantly improved. The present study indicates that long-term use of magnetic fields may be a useful way to improve the efficacy of targeted migration of stem cells and functional deficits in stem cell-based therapy for ischemic brain injury.

Influence of nanoparticle-membrane electrostatic interactions on membrane fluidity and bending elasticity

The aim of this work is to investigate the effect of electrostatic interactions between the nanoparticles and the membrane lipids on altering the physical properties of the liposomal membrane such as fluidity and bending elasticity. For this purpose, we have used nanoparticles and lipids with different surface charges. Positively charged iron oxide (γ-Fe2O3) nanoparticles, neutral and negatively charged cobalt ferrite (CoFe2O4) nanoparticles were encapsulated in neutral lipid 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine and negatively charged 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine lipid mixture. Membrane fluidity was assessed through the anisotropy measurements using the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene. Though the interaction of both the types of nanoparticles reduced the membrane fluidity, the results were more pronounced in the negatively charged liposomes encapsulated with positively charged iron oxide nanoparticles due to strong electrostatic attractions. X-ray photoelectron spectroscopy results also confirmed the presence of significant quantity of positively charged iron oxide nanoparticles in negatively charged liposomes. Through thermally induced shape fluctuation measurements of the giant liposomes, a considerable reduction in the bending elasticity modulus was observed for cobalt ferrite nanoparticles. The experimental results were supported by the simulation studies using modified Langevin-Poisson-Boltzmann model.