Effect of photoactive pigment on photodynamic therapy for cancer cells

Photoactive pigment, a photosensitizer, accumulates preferentially in cancerous tissues and visible light irradiation using a wavelength matching the absorption spectrum of the photosensitizer generates singlet oxygen that kills nearby cancer cells. This process is known as photodynamic therapy (PDT). PDT can improve quality of life and is safe, innovative technology for cancer treatment, even in high-risk patients. In this study, we used Hypericin and Protoporphyrin IX (PpIX) as a photosensitizer. Hypericin is a natural photoactive pigment. PpIX was synthesized in a topical application of aminolaevulinic acid (ALA). A light emitting diode (LED) lamp with a maximum peak of 637 nm was used for ALA-PDT and Hypericin-PDT as a light source. A Na-Li lamp with a wavelength region of 560-730 nm was also used for Hypericin-PDT as a light source. We studied the effects of the photosensitizer on PDT of a leukemic monocyte lymphoma cell line (U 937). In Hypericin-PDT using the Na-Li lamp, after 30 min of irradiation there was nearly 0% cell viability. In ALA-PDT, cell viability decreased until 90 min of irradiation (1.84 J/cm2), then proliferated again. Hypericin-PDT was more effective than ALA-PDT. In Hypericin-PDT, the Na-Li lamp was more effective than the LED lamp. The LED lamp was verified to be viable in PDT, however. This suggests that an LED lamp can be used in a clinical setting.