A superparamagnetic iron oxide (SPIO) nanoparticle is emerging as an ideal probe for noninvasive cell tracking. However, its low intracellular labeling efficiency has limited the potential usage and has evoked great interest in developing new labeling strategies. We have developed fluorescein isothiocyanate (FITC)-incorporated silica-coated core-shell SPIO nanoparticles, SPIO@SiO2(FITC), with diameters of 50 nm, as a bifunctionally magnetic vector that can efficiently label human mesenchymal stem cells (hMSCs), via clathrin- and actin-dependent endocytosis with subsequent intracellular localization in late endosomes/lysosomes. The uptake process displays a time- and dose-dependent behavior. In our system, SPIO@SiO2(FITC) nanoparticles induce sufficient cell MRI contrast at an incubation dosage as low as 0.5 microg of iron/mL of culture medium with 1.2x105 hMSCs, and the in vitro detection threshold of cell number is about 1x104 cells. Furthermore, 1.2x105 labeled cells can also be MRI-detected in a subcutaneous model in vivo. Labeled hMSCs are unaffected in their viability, proliferation, and differentiation capacities into adipocytes and osteocytes which can still be readily MRI detected. This is the first report that hMSCs can be efficiently labeled with MRI contrast nanoparticles and can be monitored in vitro and in vivo with a clinical 1.5-T MRI imager under low incubation concentration of iron oxide, short incubation time, and low detection cell numbers at the same time.
Tumblerlike magnetic/fluorescein isothiocyanate (FITC)-labeled mesoporous silica nanoparticles, Mag-Dye@MSNs, have been developed, which are composed of silica-coated core-shell superparamagnetic iron oxide (SPIO@SiO(2)) nanoparticles co-condensed with FITC-incorporated mesoporous silica. Mag-Dye@MSNs can label human mesenchymal stem cells (hMSCs) through endocytosis efficiently for magnetic resonance imaging (MRI) in vitro and in vivo, as manifested by using a clinical 1.5-T MRI system with requirements of simultaneous low incubation dosage of iron, low detection cell numbers, and short incubation time. Labeled hMSCs are unaffected in their viability, proliferation, and differentiation capacities into adipocytes and osteocytes, which can still be readily detected by MRI. Moreover, a higher MRI signal intensity decrease is observed in Mag-Dye@MSN-treated cells than in SPIO@SiO(2)-treated cells. This is the first report that MCM-41-type MSNs are advantageous to cellular uptake, as manifested by a higher labeling efficiency of Mag-Dye@MSNs than SPIO@SiO(2).
It
is a great challenge for nickel-based catalysts to obtain high-temperature
stable Ni nanoparticles with high dispersion at high loadings. To
address this problem, a group of three-dimensional (3D) networked
nickel phyllosilicate catalysts were prepared through the hydrothermal
reaction of 3D-SBA-15 and soluble nickel salts (Ni(NO3)2 or Ni(CH3COO)2) and were used for the
CO2 methanation reaction to produce CH4 (substitute
natural gas). The flower-like nanosheets corresponding to Ni3Si2O5(OH)4 are uniformly generated
on the surface of 3D-SBA-15 and become much denser with increasing
hydrothermal time, with Ni contents varying in the range of 24.22–30.72
wt %. Upon 750 °C reduction of phyllosilicate materials, small-sized
Ni particles (<5 nm) can highly disperse and be confined into the
silica and unreduced phyllosilicate support due to the strong interaction
of the nickel and complex support. In addition, a Ni/3D-SBA-15 catalyst
with the high Ni content of 30 wt % was also synthesized for comparison
by an incipient wetness impregnation method. For the CO2 methanation reaction, the fabricated phyllosilicate catalyst achieved
a higher maximum CH4 yield of 80.4% at 400 °C and
exhibited a higher long-term stability of 100 h as compared to the
impregnated sample. It was noted that the phyllosilicate catalyst
also exhibited high hydrothermal stability at 600 °C under 100%
steam. The enhanced catalytic performance was attributed to the excellent
property of nickel phyllosilicate and the special pore structure derived
from 3D-SBA-15, which could significantly improve the Ni dispersion
and increase CO2 adsorption and H2 uptake as
well as the interaction of nickel–support.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.