Fundamentals of photodynamic therapy: cellular and biochemical aspects

Photodynamic therapy of cancer is based on the photosensitizing ability of dyes which, after administration, are present in a somewhat higher concentration in tumors than in surrounding normal tissue. After light activation of the sensitizer, singlet oxygen and probably oxygen free radicals are formed and consequently all kinds of cellular components are affected. This review focuses on cellular and biochemical aspects of photodynamic therapy. Both damage to different cellular targets and cellular responses after photodynamic treatment are discussed.