Stable and nondisruptive in vitro/in vivo labeling of mesenchymal stem cells by internalizing quantum dots

Progress in stem cell research has prioritized the refinement of cell-labeling techniques for in vitro and in vivo basic and therapeutic studies. Although quantum dots, because of their optical properties, are emerging as favorable nanoparticles for bioimaging, substantial refinements or modifications that would improve their biocompatibility are still required. We report here that internalizing quantum dots (i-QDs) generated by their conjugation with an internalizing antibody against a heat shock protein-70 family stress chaperone, mortalin, offered an efficient, genetically noninvasive, nontoxic, and functionally inert way to label mesenchymal stem cells (MSCs). The i-QD-labeled MSCs underwent normal adipocyte, osteocyte, and chondrocyte differentiation in vitro and in vivo, suggesting the potential application of i-QDs in in vivo diagnostics, regenerative and therapeutic medicine.