Auburn researcher studies how tiny particles affect the health of cells

A gold nanoparticle can be helpful, harmful or something in between. 

Priscila Lotsch wants to know what makes the difference. 

“Gold in nanoscale presents an amazing combination of features that make it ideal for biological applications depending on the physicochemical properties,” Lotsch said. “But also, gold nanoparticles can be toxic depending on those properties.” 

Lotsch, an assistant professor in the Department of Biological Sciences in the College of Sciences and Mathematics, studies gold nanoparticles, engineered materials so small they interact with human cells in ways that can change depending on their properties, such as shape, size and surface chemistry. 

Gold nanoparticles already appear in products like cosmetics and some supplements, and they are among the most studied nanoparticles for biomedical applications, including nanomedicine. Researchers have also been exploring their potential in areas such as neurodegenerative diseases and cancer. That makes understanding how they behave in cells more than a theoretical question. 

The tension between promise and risk drives Lotsch’s NIH-funded project, which looks for answers through mitochondria, the structures inside cells often described as the cell’s powerhouse. 

But mitochondria are much more than that. 

“Mitochondria are central hubs of cell physiology,” she said. “If mitochondria are bad, the cell is bad. If mitochondria are healthy, this cell is healthy.” 

Because mitochondria help regulate cell behavior, stress responses and cell fate, they offer a powerful way to study how cells respond to repeated, low-dose exposure over time. 

“In real life, we are all exposed to different substances,” Lotsch said. “Think about pollutants. We are exposed to mixtures, but usually at low doses of each one individually.” 

Most laboratory studies examine acute exposure over 24, 48 or 72 hours. Lotsch is interested in what happens when cells encounter particles again and again, over weeks or months. That longer view can reveal whether cells adapt, recover or sustain lasting damage. 

“Cells can adapt in a way that is magical,” she said. 

A short-term response may look harmful at first, but longer studies can show whether cells are adapting, recovering or experiencing damage that lasts. 

In a recent study, Lotsch’s lab exposed human cells to four types of gold nanoparticles made in the lab. Some cells encountered the particles briefly, while others were exposed repeatedly over two months. After a recovery period, the team looked for signs that the cells, and especially their mitochondria, had bounced back. 

Some cells appeared to recover. Others did not. 

In one case, Lotsch found that a specific particle shape and surface chemistry caused persistent mitochondrial changes even after the particles were no longer detected inside the cells. The stress, she said, appeared to be intense enough that the mitochondria could not fully recover. 

The finding gets at one of the central ideas behind her work, showing how even small changes in particle design can lead to very different biological outcomes. 

In her lab, Lotsch can change the particles themselves, making them into spheres, rods or more complex forms, and altering the molecules on their surface. 

“All of these modifications change the way these particles interact with biological systems,” she said. 

Those interactions can point in more than one direction. If certain particles cause harmful effects, Lotsch’s findings could help guide safe-by-design materials. If others improve mitochondrial function in disease models, they could point toward future therapeutic applications. 

“If it’s toxic, we can guide safe-by-design nanomaterials,” Lotsch said. “And we can also have the therapeutic perspective for the use of these particles.” 

To understand those effects, Lotsch’s lab studies cells from the inside out, using tools that can show where particles go, how much gold enters the cells and whether mitochondria show signs of stress. 

For Lotsch, those fundamentals matter because better understanding can lead to better design. The more researchers know about how nanoparticle features such as shape, size and surface chemistry affect cells, the better they can build nanomaterials with safety and potential medical use in mind. 

“We can improve the use of nanotechnology,” Lotsch said. “But to propose new designs, we need to understand the fundamentals.”