Indocyanine green-based photodynamic therapy with 785 nm light emitting diode for oral squamous cancer cells

Background: The efficiency of photodynamic therapy (PDT) used in combination with Indocyanine green (ICG) and the light emitting diode (LED) on oral cancer was evaluated. The safety risk of ICG is known to be very low and ICG has a strong peak in the vicinity of 700-800 nm range which is thought to be a good candidate as a photosensitizer for PDT due to the deep penetration depth into the oral cancer tissue. Methods: The radiation intensity of homemade LED array was 50 mW/cm(2) at 0.5 A. To evaluate the maximum efficiency of ICG-PDT on oral cancer, different wavelengths, ICG concentrations, irradiation interval times after administering ICG, and the time durations after PDT were tested. The cytotoxicity was determined by MTT assay, and apoptosis and necrosis were also observed by double staining with SYTO 16 green and PI. Results: The IC50 value was 10 mu M when 785 nm was irradiated, while it was very low in comparison with 630 nm and 895 nm. The values were not very different with varying interval time. The percentage of apoptotic cells increased gradually to 84% at 6 h after 20 mu M ICG-PDT and the percentage of necrotic cells dramatically increased to 65% at 3 h after 200 mu M ICG-PDT. Conclusion: Using ICG-PDT with 785 nm LED light, the LED is regarded as a satisfying light source since cancer treatments in the oral region do not require focusing and increased depth of penetration due to longer wavelength enhances treatment effectiveness. (C) 2011 Elsevier B.V. All rights reserved.