Gold nanoparticles might help doctors detect colon cancer sooner, which could lead to easier and more successful treatment.
Most experts believe that colon cancer usually starts in small growths called polyps. That's one of the main things a doctor looks for during a colonoscopy. Larger polyps can be seen easily, but small ones may be overlooked.
What's needed is something that will draw attention to those nearly invisible, but possibly pre-cancerous polyps. "And what we're trying to do is develop little molecular beacons, little nanoparticles," says Sanjiv Gambhir of Stanford University.
He and his colleagues have been testing a variation on a nanoparticle used in, of all things, anti-counterfeiting measures.
Gold-silica nanoparticles are embedded into paper money and other security documents to verify their authenticity. These particles scatter light in a very distinctive way, making it easy to tell a genuine banknote from a forgery.
The Stanford researchers took the idea one step further - adding a surface layer to the nanoparticles so they would attach to cancer cells.
"On the surface of them, we put little molecules - sometimes peptides, sometimes larger proteins - that are designed to recognize targets on early cancer. And so the nanoparticles latch on because they're functionalized to, in fact, bind to cancer cells."
For colon cancer tests, the patient would drink a fluid containing hundreds of millions, or even billions of the microscopic nanoparticles. As they make their way down the bowel, they would stick to any tumor cells they encounter.
During the course of the colonoscopy, a doctor would see the bright reflection of the nanoparticles attached to the cancer cells. It might stand out sort of the way a reflective stop sign shines brightly when hit by a car's headlights on a dark night.
According to Gambhir, regulatory approval could come by the end of next year.
"Our longer term goals are to also use these to look at ovarian cancer and gliomas - brain tumors - as well as other cancers," he says. "But we do have the long-term goal of making these useful for different types of cancers and then will be used to detect low quantities of that cancer hidden in the body."
Sanjiv Gambhir and his colleagues report on the safety and promise of using nanoparticles to help find early signs of cancer in the journal Science Translational Medicine.