Chinese researchers have discovered a way to use nanoparticles made from conductive polymers to destroy cancer cells.
Called photothermal therapy, the technique can kill cancer cells without harming surrounding healthy tissue. Other research has produced similar results but those results come from using inorganic nanomaterials, such as gold nanostructures, carbon nanotubes, and copper sulfide nanoparticles — which also can absorb 
near-infrared light — but persist in the body and potentially can cause long-term side effects, reports Laura Cassiday of Chemical & Engineering News.
Zhuang Liu of Soochow University in China has improved the therapy by developing organic light-absorbing nanoparticles that are more likely to degrade in the human body than inorganic particles. “Their potential in phototherapy may not be widely realized,” he says.
Organic nanoparticles already can deliver drugs or provide gene therapy, but those materials do not absorb near-infrared light. So Liu and his team decided to use a copolymer called poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate), or PEDOT:PSS. The trouble was that the material alone is toxic to cells. To reduce the toxicity, Liu added layers of other polymers. Those other layers allowed the team to attach the polymer, polyethylene glycol.
The final material was 100-nm in diameter. The team injected the nanoparticles into mice with breast cancer tumors. Cassiday explains the research further:
When the scientists shined near-infrared light on the mouse tumors, they watched the cancerous tissue heat up to about 51 °C, while the surrounding normal tissue’s temperature remained steady at around 30 °C. Within a day of this photothermal therapy, the tumors completely disappeared. Mice that received the therapy survived for more than 45 days after the treatment; untreated mice, mice treated with just a laser pulse, and mice who received just a nanoparticle injection survived only 16 to 18 days.
The team found no signs of toxicity from the nanoparticles in the mice after 45 days. Liu says his team will continue to examine the particles’ long-term toxicity and biodegradation.
Other scientists have weighed in on the Liu’s research. Jin Zhang, a chemist at the University of California, Santa Cruz, says Liu’s work is novel and interesting. However, he suggested that the nanoparticles be made more efficient by shrinking their size and the range of wavelengths of light they absorb.
Source: “Organic Nanoparticles Heat Up Tumors,” Chemical & Engineering News, 6/5/12
Image by Multiple Authors, used under its Creative Commons license.
Dale McGeehon has been a journalist and editor for more than 25 years, covering chemical regulation and testing for Pesticides and Toxic Chemical News and innovations in material sciences for the National Technology Transfer Center. His writing credits include Omni and College Park magazines and The New York Times.
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