Disclosed is a novel photosensitizer based on polymer derivatives-photosensitizer conjugates for photodynamic therapy capable of being selectively accumulated in cancerous tissues and producing singlet oxygen or free radical by laser irradiation. The polymer derivatives-photosensitizer conjugates for photodynamic therapy are prepared as nano-sized particles, and have excellent selection and accumulation ratio for cancerous tissues. The photosensitizer conjugates can produce singlet oxygen or free radical by a specific laser wavelength. Owing to the excellent selection and accumulation ratio for cancerous tissues, the conjugates minimizes photo-cytotoxicity of the conventional photosensitizer having a low molecular amount. Accordingly, the conjugates are very useful as a photosensitizes for photodynamic therapy with reduced side effects and excellent therapeutic effectiveness.
