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Intracellular Aggregation of Multimodal Silica Nanoparticles for Ultrasound-Guided Stem Cell Implantation

Science Translational Medicine  20 Mar 2013:
Vol. 5, Issue 177, pp. 177ra35
DOI: 10.1126/scitranslmed.3005228

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Keeping Track of Stem Cells

The hype and the hope of stem cell therapy continue. Yet, clinical trials keep failing, partly because stem cells injected into the body are misplaced. To keep a close eye on stem cells and to implant them at the proper site, Jokerst and colleagues designed tiny silica particles for imaging in three different, yet complementary modes: ultrasound, fluorescence, and magnetic resonance.

The authors loaded the silica nanoparticles (SiNPs) with fluorescent dye and gadolinium ions to achieve multimodal imaging. The SiNPs were readily taken up by human mesenchymal stem cells (hMSCs) ex vivo, without affecting cell metabolism, viability, or pluripotency. Jokerst et al. then injected the particles into the left ventricle wall of healthy mice and were able to immediately track the cells by ultrasound and magnetic resonance. This allowed them to confirm accurate delivery to the heart, in real-time, and retention there for nearly 2 weeks. This multimodal cell-tracking technology is important for advancing stem cell therapy, especially for cardiovascular applications. However, testing in larger animals will be necessary to ensure successful imaging in human organs.