Electrically conductive polymers, commonly used in solar energy applications, have been modified to kill colorectal cancer cells when exposed to infrared light. Wake Forest Baptist Medical Center researchers have developed a novel formulation that gives these polymers two important capabilities for medical applications: They can be made into nanoparticles that are easily dispersed in water, and they can generate a lot of heat when exposed to infrared light. Previous electrically conductive polymers considered for photothermal therapy have proved challenging because they absorb across a wide range of infrared light. The Wake Forest polymers absorb a very narrow region, optimizing both biological transport and heat transfer, first author Dr. Christopher M. MacNeill said. The polymer nanoparticles, 50 to 65 nm, are organic and did not show any evidence of toxicity, alleviating concerns about the effects of nanoparticles that may linger in the body. When colorectal cancer cells incubated with the polymer nanoparticles were exposed to 5 minutes of infrared light, the scientists observed that up to 95 percent of the cells were killed. These nanoparticles can undergo repeated cycles of heating and cooling without affecting their heating ability, offering advantages over metal nanoparticles that can melt during photothermal treatments, leading to a loss of heating efficiency. The new method also allows for subsequent treatments to target cells that are resistant to heat-induced killing. “There is a lot more research that needs to be done so that these new nanoparticles can be used safely in patients,” said Dr. Nicole H. Levi-Polyachenko, an assistant professor of plastic and reconstructive surgery who directed the study done in collaboration with colleagues at Wake Forest University. “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.” The study was published in Macromolecular Bioscience (doi:10.1002/mabi.201200241). For more information, visit: www.wakehealth.edu
Photosensitizers