Nanospheres Facilitate Photothermal Tumor Treatment

Peptide-bound particles target melanoma

Electron microscope partial view of gold nanosphere magnified by a factor of 1 billion. The darker ring is the "wall" of the nanosphere, and the lighter area is the interior of the shell.

Hollow gold nanospheres increased the effectiveness of photothermal ablation of melanomas in mice, researchers found. The spheres, linked to a peptide that binds to a receptor on melanoma cells, gather preferentially in the tumor and help to "cook" the cancer cells during near-infrared light exposure, the researchers said. Gold is an ideal material for this application, said Jin Zhang, PhD, a professor of chemistry and biochemistry at the University of California, Santa Cruz.

Gold is an ideal material for this application, said Jin Zhang, PhD, a professor of chemistry and biochemistry at the University of California, Santa Cruz, because it strongly absorbs the near-infrared light energy used in photothermal ablation and has fewer side effects in the body than other nanomaterials.

"The next stage in our research is to push for clinical studies in humans and to study toxicity and potential side effects," Dr. Zhang said in an e-mail to PFQ. "These are expected to be minimal, but the work still needs to be done."

The next stage in our research is to push for clinical studies in humans and to study toxicity and potential side effects. These are expected to be minimal, but the work still needs to be done.

Jin Zhang, PhD, University of California, Santa Cruz

Dr. Zhang described this work in a presentation last month at the American Chemical Society meeting in Salt Lake City. He was also senior author, along with Chun Li, PhD, of the M.D. Anderson Cancer Center in Houston, of a recent paper describing the research. (Lu W, Xiong C, Zhang G, et al. Targeted photothermal ablation of murine melanomas with melanocyte-stimulating hormone analog-conjugated hollow gold nanospheres. Clin Cancer Res. 2009;15(3):876-886.)

When mice were injected with the peptide-conjugated hollow gold nanospheres, photothermal treatment caused eight times more damage to melanomas than in mice injected with similar nanospheres without the targeting peptide, the researchers found.

While photothermal treatment with near-infrared light is effective only near the surface of the body, Dr. Zhang said the hollow gold nanospheres have potential applications deeper inside tissues as well.

"Potentially, these nanospheres could be used for drug delivery, or they could be activated by other sources of radiation, instead of light,"