Optimizing gold nanoparticles for better medical imaging, drug delivery, and cancer therapy

Health care professionals use tiny particles of gold (nanoparticles) for a variety of medical applications -- from diagnostic imaging to cancer treatment. Gold works well for these applications because it doesn’t cause adverse reactions inside the body, it doesn’t break down easily, and it’s easy to see on imaging tests.

Ontario researchers used the Canadian Light Source at the University of Saskatchewan to determine whether the size of gold nanoparticles affects how they interact with an amino acid called L-cysteine. L-cysteine plays a key role in many biological processes inside the human body. It can prevent gold nanoparticles from clumping together, which is important for ensuring medical treatments work properly. L-cysteine can form a strong bond with gold, which in turn enables it to more easily attach to specific targets, such as cancer cells.

Yolanda Hedberg, a professor of chemistry at Western University, says that while many different sizes of gold nanoparticles are used in medicine, little is known about how size affects their performance. “We’re trying to understand what they do in the body and where they go. It is important to know if the (gold) particle stays the same size, because each size has specific properties and you design the particle in this way, and then don't want it to change in the human body.”

Using ultrabright synchrotron light -- combined with other techniques -- Hedberg and her team discovered that smaller gold nanoparticles (5 nanometer) bond more strongly with L-Cysteine than larger ones (10, 15, and 20 nm). For reference, a human hair is about 100,000 nm wide.

They also found that the smallest gold nanoparticles didn't clump together as much when L-Cysteine was present. Clumping can negatively affect the effectiveness, stability, and safety of nanoparticles. “This shows they can maintain their size and properties in a biological environment,” says Hedberg.

Hedberg says their findings can be used to inform production of optimally sized nanoparticles, to improve drug delivery, cancer therapy, and imaging.

“When we understand exactly how the size is affecting the reaction with the environment, we can design the particle size in a way that we make the nanomedicine as effective as possible.”

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Kalantarian, S. Marzieh, Peter Slovenský, Zhiqiang Wang, Valentin Romanovski, Elena Romanovskaia, Maroš Halama, Michael Auinger, Heng‐Yong Nie, and Yolanda S. Hedberg. "Effect of Nanoparticle Size on Cysteine‐Gold Surface Interactions." Particle & Particle Systems Characterization (2025): 70001. https://doi.org/10.1002/ppsc.202400230

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Greg Basky
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