Gold standard

Nanotechnology's go-to material

Although nanoparticles can be made from just about anything, gold is a popular choice. Yes, gold. It’s dense and has other properties that make it easy to visualize with standard imaging techniques, and it’s relatively inert, so it doesn’t cause many side effects. And even though gold nanoparticles are made from a precious metal, they are relatively inexpensive and simple to produce.

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Stanford’s Sam Gambhir, MD, PhD, is using gold nano­particles to seek out and bind to colon cancer cells in the bowel. He’s also used them to locate brain cancer cells in patients by coating them with signaling molecules that can be detected with imaging. But it’s possible humankind has been unknowingly using gold as nanomedicine for millennia.

Kattesh Katti, PhD, a professor of radiology and of physics who directs the Cancer Nanotechnology Platform at the University of Missouri, has found that some common plants like tea contain a naturally occurring chemical that not only facilitates the production of gold nanoparticles from ionic gold compounds, but also coats the particles and causes them to target and kill cancer cells. This may be why gold was considered an essential component of ancient medicines. “Perhaps the use of gold nanoparticles today is providing a scientific rationale for what our ancestors did 5,000 years ago,” muses Katti.

Now Katti has found a way to supercharge gold nanoparticles to fight cancer by making them radioactive. Although only about 5 to 10 percent of gold nanoparticles in a solution become radioactive with his technique, the benefits appear to be many.

“The idea is to deliver potent radioactivity directly into the cancer cell and selectively destroy it,” says Katti. “We have shown that not only is it feasible at the cellular levels, the nanoparticles can combat tumors in small animals.”

Katti has tested his technique, first in mice and then in dogs, with prostate tumors. Although the number of animals tested is small, the results appear nothing short of remarkable — the animals are left with no detectable tumor burden.

“Ten or 15 years ago, everything was nano this, nano that,” says Gambhir. “It could have been considered a kind of hype. But we are far beyond that now. We’ve learned that nanotechnology offers something no other technique can: sensitivity, speed, multiplexing and signal amplification — all at a relatively low cost. It’s a very exciting time.”

Krista Conger is a science writer for the medical school's Office of Communication & Public Affairs. Email her at kristac@stanford.edu.

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