[Magnetic/luminescent quantum dots bifunctional nanoparticles labeling of rat bone mesenchymal stem cells].

Objective To evaluate the dual-labeling efficiency of magnetic and luminescent quantum dots bifunctional nanoparticles to rat bone mesenchymal stem cells ( BMSC). Methods Rat BMSC were isolated, purified, and expanded. Magnetic/luminescent bifunctional nanoparticles (Fe_3O_4@ CdTe@SiO_2) , were prepared by using silicon dioxide(SiO_2) to encapsulate simultaneously Fe_3O_4 and CdTe quantum dots. BMSC were incubated with the Fe_3O_4@ CdTe@ SiO_2 nanoparticles which iron concentration was 25 μg/mL Fluorescence microscope was used to detect the fluorescence of the intracellular nanoparticles. The dual-labeled BMSC with various concentration underwent ex vivo MR imaging with T_1, WI, T_2WI and T_2~* WI sequences. To show the intracellular iron of labeled cells, prussian blue stain was performed. Spectrophotometer was used to detect the iron concentration in the cells. Results Intracellular red fluorescence of Fe_3O_4@ CdTe@ SiO_2 can be observed via fluorescent microscopy. Rat BMSC could be effectively dual-labeled with approximately 90% efficiency. The MR images with T_2WI and T_2~* WI sequences, especially with T_2~* WI sequence, showed that the signals of the dual-labeled BMSC were lower than those of the unlabeled cells. Cellular total iron is 14.05 ± 4. 15 pg per cell. Iron containing intracytoplasmic vesicles could be observed with Prussian blue staining. Conclusion Rat BMSC can be dual-labeled successfully with Fe_3O_4@ CdTe @ SiO_2 magnetic/luminescent bifunctional nanoparticles successfully, and might serve as a tool for magnetic resonance imaging and in vivo optical imaging. Key words: Stem cells; Magnetic resonance imaging; Radioactive tracers