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Classical photodynamic therapy (PDT) has a drawback of limited penetration of visible light. It has been proposed that by utilizing two-photon absorption (TPA), where illumination is carried out at near-IR wavelengths falling into tissue transparency window, the PDT can be used for deeper treatment of tumors. Here we introduce new porphyrin photosensitizer 5-(4-diphenylaminostilbene),15-(2,6-dichlorophenyl)-21H,23H- porphine (hereafter referred as DPASP) with greatly enhanced TPA cross-section in near-IR range of wavelengths. The design of DPASP was based on structure-property relationships, empirically known to enhance TPA cross-section in organic (pi) -conjugated chromophores. In our case introduction of a 4-(diphenylaminostilbene)-substituent into the 5-position of the tetrapyrrole ring results in 20-fold enhancement of TPA cross-section at (lambda) exc = 780 nm as compared with parent molecule 5-phenyl,15-(2,6-dichlorophenyl)-21H,23H-porphine (DPP). The high value of TPA cross-section of DPASP enables to reliably detect for the first time an efficient luminescence of singlet oxygen produced upon two-photon excitation of porphyrin. Singlet oxygen luminescence was also measured upon two-photon excitation of several other porphyrins including water-soluble derivative 5,10,15,20-tetrakis-(4-N-methylpyridyl)-21H,23H-porphine (TmpyP).© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
