Much of what we know about stem cells comes from optical imaging, but even common optical imaging techniques and probes can be disruptive or even toxic for the highly sensitive cells. Researchers have been seeking to create a method of labeling stem cells that minimizes toxicity and the concentration of probe inside the cells without diminishing their brightness or the ability to understand the biology of the cells. Inorganic nanocrystals have potential as bright optical probes, but using them often involves imaging conditions that can kill stem cells. New work from Foundry Users overcomes this limitation, showing that that barium titanate nanocrystals can be imaged in stem cells without associated phototoxicity. The work was recently featured as a Small cover article.
Foundry User Pantazis Periklis of ETH Basel, working with Staff Scientist Bruce Cohen, have created Second Harmonic Generating (SHG) nanocrystals to label and image hematopoietic stem cells (HSCs) with high contrast. The new SHG probes are bright enough that researchers are able to clearly label cells using at least one order of magnitude fewer nanoparticles than with other probes. Furthermore, the researchers established a cell labeling procedure that does not affect the HSC differentiation potential, their ability to generate different types of new cells, and are able to study the HSCs using both multiphoton and electron microscopy.
The research team found that freshly isolated HSCs show limited nanoparticle uptake, while HSCs entering a proliferative state display a 2.5-fold increase in uptake. Understanding the interaction between nanoparticles and stem cells will allow researchers to establish an effective and safe nanoparticle labeling strategy for somatic stem cells that can critically contribute to an understanding of their in vivo therapeutic potential.