A new optical fiber-based drug delivery device promises to unlock the potential of photosensitive chemicals to kill drug-resistant infections and perhaps cancer tumors as well. The device was designed and constructed by researchers Jie Chen, Thomas C. Cesario and Peter M. Rentzepis of the University of California. Photosensitive chemicals are molecules that release single oxygen atoms and chemical radicals when illuminated. These radicals are very active chemically and can rip apart and destroy bacteria, said Rentzepis, a professor of chemistry at the university. Yet photosensitive chemicals are highly toxic and difficult to activate beneath the skin because light penetrates only a few millimeters into the body. They also cause severe reactions, including headaches, nausea and light sensitivity for 30 days. They kill healthy cells as well as bacteria. Although several have therapeutic potential, they are too toxic for human use by injection. The chemicals are not approved for use in the US and are used relatively rarely in Europe. Designed to address these problems, the optical fiber device can deliver very small amounts of photosensitive chemicals to internal organs with pinpoint accuracy. The device consists of three components: An imaging component similar to the charge coupled devices (CCDs) in digital cameras enables a physician to guide the device to the infection. A 1-mm-diameter flexible optical fiber attached to a microsize high-power LED or laser diode provides the light for the CCD. Once the physician positions the device, the same light source shines with greater intensity to activate the medicine. A hollow tube connected to a syringe delivers the medicine to the infection. Rentzepis adds glycol, a thickening agent used in surgical soaps, to keep the medicine from spreading to healthy cells. Pulling the syringe backward creates a vacuum that sucks up any remaining chemical after the procedure. “We can insert the instrument through the nose, bowels, mouth, or almost any opening, and direct it where we want,” Rentzepis said. “It lets us deliver very small amounts of these chemicals right to an infection or tumor, then remove them before they damage healthy cells.” The researchers plan to test the device on animals that have infections and cancer. Their work is reported in Review of Scientific Instruments, a journal published by the American Institute of Physics, based in College Park, Md. For more information, visit: www.aip.org