The heat is on: NIR tumour ablation

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  • Published: Dec 1, 2012
  • Author: David Bradley
  • Channels: Infrared Spectroscopy
thumbnail image: The heat is on: NIR tumour ablation

NPs + NIR vs. cancer

Low Band Gap Donor-Acceptor Conjugated Polymer Nanoparticles and their NIR-mediated Thermal Ablation of Cancer Cells

In work supported by the Department of Plastic and Reconstructive Surgery at Wake Forest Baptist Medical Center, Nicole Levi-Polyachenko and colleagues there and in the Center for Nanotechnology and Molecular Materials at Wake Forest University have modified electrically conductive polymers, more commonly used in solar energy applications, to develop nanoparticles for a medical application.

Levi-Polyachenko and her team developed a new formulation that gives their polymers two important properties: the polymers can easily be made into nanoparticles which can disperse rapidly in water and secondly they generate a lot of heat when exposed to near-infrared light. Exposure to NIR (808 nanometres) raises the temperature to 50 Celsius. Crucially, body tissues are transparent in the NIR range 700-1100 nm. The team's nanoparticles are based on 2-ethylhexyl cyclopentadithiophene co- polymerized with 2,1,3-benzothiadiazole (for nano-PCPDTBT) or 2,1,3-benzoselenadiazole (for nano-PCPDTBSe). The resulting nanoparticles are stable in water and have low toxicity up to 1 milligram per microlitre. 

Heat treatment

The team has carried out photothermal ablation studies using their polymer nanoparticles against RKO and HCT116 colorectal cancer lines cells. The team found that when these cancer cells were incubated with the polymer nanoparticles under exposure to NIR for just five minutes 95 percent of the cells were killed. "The results of this study demonstrate how new medical advancements are being developed from materials science research," Levi-Polyachenko enthuses.

Team member Christopher MacNeill of Wake Forest explains that the problem with other electrically conductive polymers has been that they absorb across too wide a range of wavelengths and so have not proven themselves effective in photothermal therapy. "We have specifically used electrically conductive polymers designed to absorb a very narrow region of infrared light, and have also developed small, 50-65 nanometre, polymer nanoparticles in order to optimize both biological transport as well as heat transfer." 

Running hot and cold

The polymer nanoparticles are capable of undergoing repeated heating-cooling cycles without any detrimental effects on their ability to generate heat under NIR exposure. This offers advantages over metal nanoparticles, which can melt during photothermal treatments, which would lower heating efficiency. The use of organic materials also allows for subsequent treatments to target those cells that are resistant to the initial heat-induced killing.

Levi-Polyachenko concedes that much work is yet to be done before a clinically viable technology emerges from this research. "There is a lot more research that needs to be done so that these new nanoparticles can be used safely in patients," she says, "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 next steps include in vivo testing to evaluate systemic delivery, toxicity, and therapeutic photothermal effect," Levi-Polyachenko told SpectroscopyNOW. "We are also working to functionalize the new nanoparticles to specifically target the cancer cells only. Ultimately, we are hoping to develop a new, and safe, class of materials for photothermal ablation treatment of cancer."

Related Links

Macromol Biosci, 2012: "Low Band Gap Donor-Acceptor Conjugated Polymer Nanoparticles and their NIR-mediated Thermal Ablation of Cancer Cells"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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