Nanoparticles hunt down and kill tumors.

An innovative therapy that uses gold nanoparticles to destroy tumors could someday offer patients a new weapon against cancer, recent animal studies suggest. Researchers at Rice University in Houston injected gold-coated silica spheres into mouse tumors. Light shined onto the particles triggered the release of heat that destroyed the cancer cells. Because this phototherapy would be less invasive than surgery, it could offer an alternative to typical cancer treatments, the team says.

Each particle, which the researchers call a nanoshell, measures about 130 nanometers in diameter. The team designed the nanoshells to absorb near-infrared light, which can penetrate tissue without damaging it.

After injecting the nanoshells into the mouse tumors, Jennifer West and her colleagues shined near-infrared light over the tumor site for several minutes. The resulting temperature rise of nearly 40[degrees]C was enough to cause irreversible tissue damage. Untreated tissues near the tumors, however, remained unharmed. The Rice team reports its results in the Nov. 11 Proceedings of the National Academy of Sciences.

The nanoshells might work against tumors in places where surgery is difficult, such as the brain, or for cancers that have spread in the body, say the researchers. To show that potential, the Rice team injected nanoshells into the bloodstreams of mice with cancer. Because tumors are surrounded by leaky blood vessels, the tiny particles slipped out of the vessels predominantly at the cancer sites and accumulated there, says coinvestigator Leon Hirsch.