Mostafa El-Sayed and Ivan El-Sayed, at the Georgia Institute of Technology, showed in former research that gold nanoparticles coated with a cancer antibody were very effective at binding to tumour cells. When bound to the gold, the cancer cells scattered light, making it very easy to identify the noncancerous cells from the malignant ones. The nanoparticles also absorbed the laser light more easily, so that the coated malignant cells only required half the laser energy to be killed compared to the benign cells. This makes it relatively easy to ensure that only the malignant cells are being destroyed.
Now, they've discovered that by changing the spheres into rods, they can lower the frequency to which the nanoparticles respond from the visible light spectrum used by the nanospheres to the near-infrared spectrum.
"With the nanospheres we’re using visible lasers, but most of the solid cancer is under the tissues and visible light doesn’t go but a few millimeters deep. But by using the nanorods we can tune them to react to the infrared lasers, which can penetrate the tumour without being absorbed by the tissues,” said Mostafa El-Sayed, director of the Laser Dynamics Laboratory at Georgia Tech.
Many cancer cells have a protein, known as Epidermal Growth Factor Receptor (EFGR), all over their surface, while healthy cells typically do not express the protein as strongly. By conjugating the gold nanorods to an antibody for EFGR, suitably named anti-EFGR, researchers were able to get the nanoparticles to attach themselves to the cancer cells.
"This makes it more practical than the sphere in terms of treating cancer,” said Mostafa El-Sayed. “For laser phototherapy treatment of skin cancer or, for diagnostic biopsies, the spheres are fine, but for phototherapy of cancer deep under the skin, like breast cancer, then one really needs to use the nanorods treatment.”
MEDICA.de; Source: Georgia Institute of Technology