Figure 2.

(A) Transmission electron microscopy images of gadolinium-doped mesoporous silica MCM-41 (Gd₂O₃@MCM-41)-labeled mesenchymal stem cells (MSCs). Gd₂O₃@MCM-41 nanoparticles are observed as black particles in the secondary lysosome (black arrow) and the cytoplasm (double black arrows). The white spots (white arrow) were the result of the nanoparticles being separated into sections. Scale bar = 500 nm. (B) T₁-weighted magnetic resonance image of MSCs incubated with Gd₂O₃@MCM-41 at different concentrations (50, 20, and 10 μg/mL). (C) The proliferation of Gd₂O₃@MCM-41-labeled MSCs at different concentrations (50 and 20 μg/mL) and non-labeled MSCs by MTT assay after 2, 4, 8, and 12 days of treatment.

Abbreviations: PBS, phosphate-buffered saline; OD, optical density; MTT, 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide.