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Associate Professor Christine Payne and graduate student Sabiha Runa study the interaction of titanium dioxide nanoparticles with cells. On the screen is a fluorescent microscopy image of human cancer cells.

 

A nanoparticle commonly used in food, cosmetics, sunscreen, and other products can have subtle effects on the activity of genes expressing enzymes that address oxidative stress inside at least two types of living cells. While the titanium dioxide nanoparticles are considered nontoxic because they don’t kill cells at low concentrations, these cellular effects could add to concerns about long-term exposure to the nanomaterial.

Researchers used high-throughput screening techniques to study the effects of titanium dioxide nanoparticles on the expression of 84 genes related to cellular oxidative stress. The work found that six genes, four of them from a single gene family, were affected by a 24-hour exposure to the nanoparticles.

Image shows HeLa cells incubated with serum-coated titanium dioxide nanoparticles. Proteins are tagged with a red fluorophore, while cell nuclei are stained blue.

The effect was seen in two different kinds of cells exposed to the nanoparticles: human HeLa cancer cells commonly used in research, and a line of monkey kidney cells. Polystyrene nanoparticles similar in size and surface electrical charge to the titanium dioxide nanoparticles did not produce a similar effect on gene expression.

“This is important because every standard measure of cell health shows that cells are not affected by these titanium dioxide nanoparticles,” said Christine Payne, an associate professor in Georgia Tech’s School of Chemistry and Biochemistry. “Our results show that there is a more subtle change in oxidative stress that could be damaging to cells or lead to longterm changes. This suggests that other nanoparticles should be screened for similar low-level effects.”

Melissa Kemp, an associate professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, collaborated with Payne on the study. The research was reported in the Journal of Physical Chemistry C and was supported by the National Institutes of Health through the HERCULES Center at Emory University as well as by a Vasser Woolley Fellowship. — John Toon

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