Zap Diseased Cells with Targeted Heat from Nanoparticles
Researchers are looking to nanotechnology for ways to replace radiation therapy for the treatment of cancer. An interesting alternative is hyperthermia therapy made possible by advances in nanotechnology.
Sadly, many of us have seen the debilitating effects of currently available radiation therapies on the patients undergoing them. The problem with radiation therapy is that the radiation can cause severe side effects by damaging surrounding healthy tissue while trying to target diseased tissue.
Hyperthermia therapy raises the temperature of diseased tissue, such as cancer tumors, to kill it off. Researchers have found that raising the temperature of cells above 45 degrees centigrade does the trick. Nanoparticles are used to absorb energy from sources such as infrared light and convert that energy into heat, which is then applied directly to diseased cells with no or little damage to surrounding tissue.
Several researchers are using gold nanoparticles for hyperthermia therapy because gold has the capability to convert certain wavelengths of light into heat. As with all metals, gold contains electrons that are not tied to any particular atom but are free to move throughout the material. These electrons help to conduct a current when you apply a voltage.
Depending on the size and shape of the nanoparticles, these free electrons absorb the energy from a particular wavelength of light. At the right wavelength, light makes the cloud of free electrons on the surface of the gold nanoparticles resonate, heating them and transferring that heat to the target cells.
Two types of gold nanoparticle shapes are most efficient in converting light into heat:
Gold nanorods: These solid cylinders of gold have a diameter as small as 10 nm. By using nanorods with various combinations of diameter and length, researchers can change the wavelength of light that the nanorod absorbs.
Nanoshells: These types of nanoparticles consist of a gold coating over a silica (silicon dioxide, the same material as glass) core. By using nanospheres with variations in the thickness of the gold coating and the diameter of the silica core, researchers can change the wavelength of the light that the nanosphere absorbs.
Various researchers are using nanorods, nanoshells, or other nanoparticles that convert light to heat (such as carbon nanotubes) to develop methods for localized heat treatment of diseased regions of the body.
An interesting alternative to hyperthermia therapy uses nanoparticles composed of titanium dioxide functionalized by attaching an antibody that is attracted to cancer cells. When researchers shine visible light on the cancer tumor, the titanium dioxide, which is a photocatalyst, donates electrons to oxygen in the bloodstream, creating negatively charged oxygen atoms. These oxygen atoms react with molecules in the cancer cells, killing them.
Because visible light can’t penetrate very far into the body, this method will work only for cancer cells close to the surface.