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fibroblast proliferation, growth factor syntheses, collagen production and angiogenesis. Lasers, however, have some inherent characteristics, which make their use in a clinical setting problematic, including limitations in wavelengths and beam width. The combined wavelengths of light optimal for wound healing cannot be efficiently produced, and the size of wounds which may be treated by lasers is limited. Light- emitting diodes (LED’s) offer an effective alternative to lasers. These diodes can be made to produce multiple wavelengths, and can be arranged in large, flat arrays allowing treatment of large wounds. Our experiments suggest potential for using LED light therapy at 680, 730 and 880 nm simultaneously, alone and in combination with hyperbaric oxygen therapy, both alone and in combination, to accelerate the healing process in Space Station Missions, where prolonged exposure to microgravity may otherwise retard healing. NASA LED’s have proven to stimulate wound healing at near-infrared wavelengths of 680, 730 and 880 nm in laboratory animals, and have been approved by the U.S. Food and Drug Administration (FDA) for human trials. Furthermore, near-infrared LED light has quintupled the growth of fibroblasts and muscle cells in tissue culture. The NASA LED arrays are light enough and mobile enough to have already flown on the Space Shuttle numerous times. LED arrays may prove to be useful for improving wound healing and treating problem wounds, as well as speeding the return of deconditioned personnel to full duty performance. Potential benefits to NASA, military, and civilian populations include treatment of serious burns, crush injuries, non-healing fractures, muscle and bone atrophy, traumatic ischemic wounds, radiation tissue damage, compromised skin grafts, and tissue regeneration. LED-PHOTODYNAMIC THERAPY FOR CANCER Photodynamic therapy (PDT) is a cancer treatment modality that recently has been applied as adjuvant therapy for brain tumors. PDT consists of intravenously injecting a photosensitizer, which preferentially accumulates in tumor cells, into a patient and then activating the photosensitizer with a light source. This results in free radical generation followed by cell death. The development of more effective light sources for PDT for brain tumors has been facilitated by applications of space light-emitting diode array technology; thus permitting deeper tumor penetration of light and use of better photosensitizers. Lutetium Texaphyrin (Lutex) and Benzoporphyrin Derivative (BPD) are new, second generation photosensitizers that can potentially improve PDT for brain tumors. Lutex and BPD have major absorption peaks at 730 nm and 680 nm respectively, which gives them two distinct advantages. First, longer wavelengths of light penetrate brain tissue easily so that larger tumors could be treated; and second, the major absorption peaks mean that more of the drug is activated upon exposure to light. Tumorcidal effects of Lutex and BPD have been studied in vitro using canine glioma and human glioblastoma cell cultures. Using light-emitting diedes (LED) with peak emissions of 728 nm and 680 nm as a light source, a greater than 50 percent cell kill was measured in both cell lines by tumor DNA synthesis reduction. The effectiveness of Lutex and BPD against tumor cells in vitro thus established, we have taken the first step toward determining their in vivo efficacy by performing experiments to determine the largest doses of both Lutex, or BPD, and light that can be administered to dogs before toxicity is seen, i.e. the maximum tolerated dose (MTD). Using this dose allows us to effect maximum tumor cell destruction during in vivo studies. For longer wavelengths of light, the improved NASA LED-technology is required. LED’s are an effective alternative to lasers for PDT. Laser conversion to near-infrared wavelengths is inherently costly and inefficient, using an argon ion or KTP/YAG laser beam that is converted by a dye module, usually to 630 nm. LED’s have been frequently used to emit longer wavelength broad spectrum near-infrared light of 25- 30 nm bandwidths. LED lamps traditionally consist of an array of semiconducting LED chips. In recent years, improvements in semiconductor technology have substantially increased the light output of LED chips. A novel type of LED chip is based on the semiconductor Aluminum Gallium Arsenide (AlGaAs). These LED chips have been manufactured to emit light with peak wavelengths of 680 and 730 nm, which are optimal wavelengths for the absorption spectrum of the new photosensitizers used for cancer PDT. Human trials have begun at the Medical College of Wisconsin, Naval Special Warfare Command and NASA-Marshall Space Flight Center. Photodynamic Therapy with NASA LED Human Subjects 2PDF Image | NASA Light-Emitting Diode Medical Program
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