Labeling and imaging of human mesenchymal stem cells with quantum dot bioconjugates during proliferation and osteogenic differentiation in long term.

Quantum dots (QDs) are semiconductor nanocrystals that serve as promising alternatives to organic dyes for cell labeling. Because of their unique spectral, physical and chemical properties, QDs are useful for concurrently monitoring several intercellular and intracellular interactions in live normal cells and cancer cells over periods ranging from less than a second to over several days (several divisions of cells). Here, peptide CGGGRGD is immobilized on CdSe-ZnS QDs coated with carboxyl groups by cross linking with amine groups. These conjugates are directed by the peptide to bind with selected integrins on the membrane of human Mesenchymal stem cells. Upon overnight incubation with optimal concentration, QDs effectively labeled all the cells. Here, we report long-term labeling of human bone-marrow-derived mesenchymal stem cells (hMSCs) with RGD-conjugated QDs during self replication and differentiation into osteogenic cell lineages.