In a major advance in cancer treatment, nanotechnology researchers have developed the first hollow gold nanospheres that search out and "cook" cancer cells.
The researchers say that the cancer-destroying nanospheres, smaller than the finest flecks of dust, particularly show promise as a minimally invasive future treatment for malignant melanoma, the most serious form of skin cancer.
The hollow gold nanospheres are equipped with a special "peptide" that draws them directly to melanoma cells, while avoiding healthy skin cells.
The nanospheres heat up when, after gathering inside the tumor, they are exposed to near-infrared light, which penetrates deeply through the surface of the skin.
The researchers said that in recent studies in mice, the hollow gold nanospheres did eight times more damage to skin tumors than the same nanospheres without the targeting peptides.
"This technique is very promising and exciting. It's basically like putting a cancer cell in hot water and boiling it to death. The more heat the metal nanospheres generate, the better," explained study co-author Dr. Jin Zhang, a professor of chemistry and biochemistry at the University of California in Santa Cruz.
The technique is actually a variation of photothermal ablation, also known as photoablation therapy (PAT), a technique in which doctors use light to burn tumors.
To develop more effective cancer-burning materials, the researchers focused on hollow gold nanospheres, each about 1/50,000th the width of a single human hair.
In 2006 Zhang announced that he had finally developed a nanoshell or hollow nanosphere with the "right stuff" for cancer therapy-gold spheres with an optimal light absorption capacity in the near-infrared region, small size, and spherical shape, perfect for penetrating cancer cells and burning them up.
"Previously developed nanostructures such as nanorods were like chopsticks on the nanoscale. They can go through the cell membrane, but only at certain angles. Our spheres allow a smoother, more efficient flow through the membranes," said Zhang.
Apart from being smaller than other nanoparticles previously designed for photoablation therapy, gold is also safer and has fewer side effects in the body than other metal nanoparticles.
The researchers equipped the nanospheres with a peptide to a protein receptor that is abundant in melanoma cells, giving the nanospheres the ability to target and destroy skin cancer.
In tests using mice, the resulting nanospheres were found to be significantly more effective than solid gold nanoparticles due to much stronger near infrared-light absorption of the hollow nanospheres, the researchers say.
Now, Zhang is planning to try the nanospheres in humans, which requires extensive pre-clinical toxicity studies.
The findings of the study were presented at the American Chemical Society's 237th National Meeting.