Nanoparticles packed with high concentrations of a proven cancer-killing drug may provide a safer and more effective way to target brain tumors, researchers at the University of Michigan Comprehensive Cancer Center have found. Administration of the light-sensitive drug Photofrin into the system to attack cancer cells usually is accompanied by a number of potentially serious side effects, including sensitivity to light that can last up to six weeks. The powerful PDT drug also can damage healthy tissue en route to the diseased site. To overcome these problems, investigators led by Brian D. Ross and Raoul Kopelman incorporated the photosensitizer, along with iron oxide, into nanoparticles that served as couriers, directly delivering the dose to the cancerous tumor (see figure). A laser then activated the drug. The iron oxide served as a contrast agent for an enhanced MRI. The nanoparticle delivery system was tested in vivo on rats with brain tumors, and the researchers found less exposure to surrounding healthy tissue and increased concentrations of the drug in tumoral areas. Rats that received the photosensitizer by a traditional systemic injection survived 13 days, while those treated with the nanoparticle delivery system survived an average of 33 days. Forty percent of the rats were disease-free after six months. The results appeared in the Nov. 15 issue of Clinical Cancer Research. The research suggests that the nanoparticle method could carry higher doses of virtually any drug harmful to healthy tissue, delivering a more powerful payload directly to the disease. If nanoparticle delivery is found to be safe in humans, it could result in drugs with particularly harmful side effects being reintroduced for use. Further research is needed before the method can be tested in clinical trials.