“Early detection of any cancer, including colorectal cancer, markedly improves survival. Gold-centered spheres smaller than viruses — has been shown safe when administered by two alternative routes in a mouse study. This marks the first step up the ladder of toxicology studies that, within a year and a half, could yield to human trials of the tiny agents for detection of colorectal and possibly other cancers. “These nanoparticles’ lack of toxicity in mice is a good sign that they’ll behave well in humans,”
The widespread use of colonoscopy has significantly lowered colon-cancer mortality rates, he said. “But colonoscopy relies on the human eye. So this screening tool, while extremely useful, still misses many cancer lesions such as those that are too tiny, obscure or flat to be noticed.”
The new study is the first-ever successful demonstration of the safety of a new class of agents: tiny gold balls that have been coated with materials designed to be detected with very high sensitivity, then encased in see-through silica shells and bound to polyethylene glycol molecules to make them more biologically friendly. Molecules that home in on cancer cells can be affixed to them. The resulting nanoparticles measure a mere 100 nanometers in diameter.
The materials surrounding the nanoparticles’ gold centers have special, if subtle, optical properties. Typically, light bounces off of a material’s surface at the same wavelength it had when it hit the surface. But in each of the specialized materials, about one ten-millionth of the incoming light bounces back in a pattern of discrete wavelengths characteristic of that material. The underlying gold cores have been roughed up in a manner that greatly amplifies this so-called “Raman effect,” allowing the simultaneous detection of many different imaging materials by a sensitive instrument called a Raman microscope.
Gambhir’s group is now filing for FDA approval to proceed to clinical studies of the nanoparticles for the diagnosis of colorectal cancer.