Quantum dot labeled human mesenchymal stem cells undergoing proliferation. hMSCs were incubated for 16 hrs in a 30 nM solution of bioconjugated QDs (a-a2). Following the removal of extracellular QDs, QD-labeled hMSCs and unlabeled hMSCs of the same subpopulation were continuously cultured for 4, 7 and 22 days (b-b2, c-c2, d-d2, respectively). Scale bar: 30 μm. QDs were internalized in the cytoplasm, even after 22 days of culture-expansion (e-e2), apparently endocytosed as aggregates. Scale bar: 5 μm. Reproduced from  and contributed by Jeremy Mao (Columbia University, New York).
Kherlopian et al. BMC Systems Biology 2008 2:74 doi:10.1186/1752-0509-2-74