The Taiwan and Korea team has also found that ZnO NPs quantum dots (QDs) show promise for biological labelling and the researchers have been looking at how the materials may be used to label stem cells. They have found that the ZnO QDs are antibacterial, have low cytotoxicity and can be used as efficient labels on a variety of cells, including stem cells.

In this work, researchers in Prof. Lee’s labs began by synthesizing green fluorescent ZnO QDs that were around 2 nm in size on average, in methanol. Prof. Hsu’s team then further modified the ZnO QDs using polyethylene glycol (PEG) to form water-dispersible ZnO QDs. Fourier transform infrared spectroscopy (FTIR) spectra on the materials revealed that PEG molecules were attached to the ZnO QDs and no obvious size alteration was observed for ZnO QDs after PEG conjugation as seen by high-resolution TEM. The water-dispersible ZnO QDs remained antibacterial and fluorescent. They also remained biocompatible.

Cytotoxicity evaluations showed that the ZnO QDs were generally safe in concentrations of 30 ppm or below and ZnO QD-labelled adipose-derived adult stem cells (ADAS) maintained their ability to differentiate (differentiation is a hallmark of stem cells). Moreover, the reduced oxygen consumption upon exposure to a low amount of ZnO QDs may even facilitate their differentiation by metabolic compensation through glycolysis.

The team now plans to study the materials in more detail and fully explore their potential in biological labelling and other applications.

More information can be found in the journal Nanotechnology (in press).

Further reading

Fluorescent nanoparticles enhance stem-cell tracking (Sep 2009)
Tuneable emissions from zinc oxide QDs (Sep 2008)