Labeling of Mesenchymal Stem Cells by Bioconjugated Quantum Dots

Abstract

Long-term labeling of stem cells during self-replication and differentiation benefits investigations of development and tissue regeneration. We report the labeling of human mesenchymal stem cells (hMSCs) with RGD-conjugated quantum dots (QDs) during self-replication, and multilineage differentiations into osteogenic, chondrogenic, and adipogenic cells. QD-labeled hMSCs remained viable as unlabeled hMSCs from the same subpopulation. These findings suggest the use of bioconjugated QDs as an effective probe for long-term labeling of stem cells.

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“…Immortalized cell lines have been successfully labeled using synthetic transfection reagents, such as lipofectamine 19 and polyethylene imine (PEI); 20 however, such reagents are unacceptably cytotoxic at even low concentrations to a variety of primary somatic and stem cell types, limiting their utility for labeling of such cells. Surface conjugation of small molecules, such as cholera toxin B, and biologically active oligopeptides, such as arginineglycine-aspartic acid (RGD), to nanoparticles has also yielded high rates of endocytic cellular uptake; 21,22 however, trafficking through endo-lysosomal pathways beyond uptake causes these particles to be rapidly evacuated from cells. 21 Furthermore, engagement of specific cell surface receptors by these active molecules, ie, surface gangliosides by cholera toxin B 21 and a dozen known integrins by RGD, 23 not only enables cell labeling but also effects cell fate, which may be undesirable for the mechanistic studies such labeling is meant to support.…”

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“…This action revealed the formation of wide and flat leading lamellipodia filled with a dense actin network (Chang et al, 2009). Human mesenchymal stem cells labelled with quantum dots represented the same viability comparing with the unlabelled human mesenchymal stem cells from the same subpopulation (Shah et al, 2007), suggesting that quantum dots could be used safely for long term labelling of stem cells. Moreover, embryonic stem cells could be labelled with quantum dots for cellular tracking in vivo without affecting the viability, proliferation or differentiation of the embryonic stem cells (Lin et al, 2007).…”

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“…Information concerning participation and clustering of multiple cell surface molecules involved in stem cell migration and differentiation may be useful for the design of innovative scaffolds for homing stem cells before transplantation. QDs are also internalized by endocytosis, which is improved by the use of specific peptides such as RGD, phospholipids and cholera toxin [84][85][86]. A number of internalized QDs are transported via endosomes to the perinuclear region [87], while QDs that will not be used by the cells display an oxidative degradation [68] that could lead to mitochondria dysfunction and, ultimately, cell death [88].…”

“…A number of internalized QDs are transported via endosomes to the perinuclear region [87], while QDs that will not be used by the cells display an oxidative degradation [68] that could lead to mitochondria dysfunction and, ultimately, cell death [88]. It is possible that the composition and physical properties of QDs and magnetic nanoparticles lead to unique toxic responses [53,85,87]. To date there is no conclusive evidence of known human toxic responses that are exclusively caused by nanomaterials [53].…”

“…To date there is no conclusive evidence of known human toxic responses that are exclusively caused by nanomaterials [53]. Furthermore, most of the studies demonstrated no interference of these nanoparticles with stem cell differentiation [84,85]. However, variations in the composition, structure, size and surface coating of nanoparticles may influence stem cell behavior and fate [88,89].…”