Photodynamic therapy (PDT) uses a combination of ultraviolet or visible light and a light-sensitive chemical, or photosensitizer, to kill cancer cells using reactive oxygen.
PDT has become an important option for treating or relieving the symptoms of esophageal cancer and non-small cell lung cancer, but its wider use in cancer therapy is limited by a number of factors, including the toxicity of the photosensitizer dyes. But now, using a biocompatible polymer nanoparticle, researchers at the University of Michigan have developed a nontoxic photodynamic dye that appears to be particularly lethal to brain cancer cells.
The leader of the team that conducted this work, Raoul Kopelman, Ph.D., was one of the first investigators to study nanoparticles for use in cancer therapy as part of the National Cancer Institute's Unconventional Innovations Program. The success of this nanotechnology pilot program played an important role in the NCI's decision to establish the Alliance for Nanotechnology in Cancer. Kopelman and his colleagues published this latest work in the journal Nano Letters.
In creating their PDT nanoparticle, the Michigan investigators chose as the photosensitizer a commercially available dye that can simultaneously absorb two low-energy, near-infrared photons and use the combined energy to produce a highly reactive form of oxygen known as singlet oxygen. Singlet oxygen is exceedingly toxic to cells, so for PDT to be successful, investigators need to develop methods that limit exposure of healthy cells to the PDT dyes. Nanoparticles, it turns out, appear to be an ideal vehicle for doing just that.