Dynamic behavior of photosensitizers after multiphoton excitation

The spectroscopy and photochemistry of protoporphyrin IX (PpIX) in ethanol and in Triton X-100 micelle solution and Verteporfin in methanol and Triton X-100 micelle solution have been examined using near infrared two-photon excitation (TPE). TPE will allow photodynamic therapy with highly localized light dosage. For PpIX, we have determined that the photochemistry subsequent to TPE is very similar to that found for one-photon excitation. Moreover, the photoproducts observed possess very intense two-photon excitation fluorescence spectra, which allows their detection at low relative concentrations. Verteporfin displays photodynamic behavior in methanol similar to that of PpIX in ethanol. However, in micelle solution Verteporfin exhibits photodynamic behavior indicative of two sensitizer populations, excimers and monomers. Photochemical models are presented.