Electrically-conductive polymers, commonly used in solar energy applications, have been modified so that infrared light causes them to generate heat that can be used to kill colorectal cancer cells.
A research team developed a novel formulation that gives the polymers two important capabilities for medical applications. The polymers can be made into nanoparticles that are easily dispersed in water, and they generate a lot of heat when exposed to infrared light.
The investigators found that when colorectal cancer cells incubated with the polymer nanoparticles were exposed to 5 minutes of infrared light, up to 95% of the cells were killed. The polymer nanoparticles could undergo repeated cycles of heating and cooling without having their heating ability affected. This offers advantages over metal nanoparticles, which can melt during photothermal treatments, leading to a loss of heating efficiency. This also allows for subsequent treatments to target cells that are resistant to heat-induced killing.
The ability of electrically conductive polymers to absorb across a wide range of infrared light is a challenge for the other electrically conductive polymers that have been recently explored for photothermal therapy. First author Christopher M. MacNeill, PhD, of Wake Forest Baptist Medical Center noted that, “we have specifically used electrically conductive polymers designed to absorb a very narrow region of infrared light, and have also developed small, 50 to 65 nm, polymer nanoparticles in order to optimize both biological transport as well as heat transfer.” For example, 50 nm is about 2,000 times smaller than a human hair.
The polymer nanoparticles are organic and did not show any evidence of toxicity, which helps to alleviate concerns about the effects of nanoparticles that may potentially linger in the body.
“There is a lot more research that needs to be done so that these new nanoparticles can be used safely in patients,” cautioned Nicole H. Levi-Polyachenko, PhD, also of Wake Forest Baptist Medical Center, “but the field of electrically conductive polymers is broad and offers many opportunities to develop safe, organic nanoparticles for generating heat locally in a tissue. We are very enthusiastic about future medical applications using these new nanoparticles, including an alternative approach for treating colorectal cancer.”
This study was published in Macromolecular Bioscience (2012; doi:10.1002/mabi.201200241).