Manganese-Loaded
Dual-Mesoporous Silica Spheres for Efficient T1- and T2-Weighted Dual
Mode Magnetic Resonance Imaging
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Abstract
A novel
class of manganese-based dual-mode contrast agents (DMCAs) based on
the core–shell structured manganese-loaded dual-mesoporous
silica spheres (Mn-DMSSs) for simultaneous T1- and T2-weighted magnetic
resonance imaging (MRI) has been successfully reported. The in vitro
MR tests demonstrate that the Mn-based DMCAs display an excellent
simultaneous T1-weighted and T2-weighted MR imaging effect with a
noticeably high T1 relaxivity (<i>r</i><sub>1</sub>) of
10.1 mM<sup>–1</sup>s<sup>–1</sup> and a moderately
high T2 relaxivity (<i>r</i><sub>2</sub>) of 169.7 mM<sup>–1</sup>s<sup>–1</sup>. The Mn-based DMCAs exhibit
negligible cytotoxicity with >80% cell viability at a concentration
of up to 200 μg/mL in human liver carcinoma (HepG2) and mouse
macrophage (RAW264.7) cells after 24 h. Confocal laser scanning microscopy
(CLSM) results show that the Mn-DMSSs were internalized via endocytosis
and located in the cytoplasm but not in the nucleus. The in vivo experiment
shows that the signals of rat liver increased by 29% under T1-weighted
imaging mode and decreased by 28% under T2-weighted imaging mode in
5 min postinjection of Mn-DMSSs, which reveal that the novel Mn-loaded
DMSSs can be used as both positive (T1-weighted) and negative (T2-weighted)
MR contrast agents in further biomedical applications