The effect of fluence rate and wavelength on the formation of protoporphyrin IX photoproducts.

Photodynamic diagnosis and therapy (PDD and PDT) are emerging techniques for diagnosing and treating tumors and malignant diseases. Photoproducts of protoporphyrin IX (PpIX) used in PDD and PDT may be used in the diagnosis and treatment, making a detailed analysis of the photoproduct formation under various treatment and diagnosis conditions important.Spectroscopic and mass spectrometric analysis of photoproduct formation from PpIX dissolved in dimethyl sulfoxide were performed under commonly used irradiation conditions for PDD and PDT, i.e., wavelengths of 405 and 635 nm and fluence rates of 10 and 100 mW/cm2. Irradiation resulted in the formation of hydroxyaldehyde photoproduct (photoprotoporphyrin; Ppp) and formyl photoproduct (product II; Pp II) existing in different quantities with the irradiation wavelength and fluence rate. Ppp was dominant under 635 nm irradiation of PpIX, with a fluorescence peak at 673 nm and a protonated monoisotopic peak at m/z 595.3. PpIX irradiation with 405 nm yielded more Pp II, with a fluorescence peak at 654 nm. A higher photoproduct formation was observed at a low fluence rate for irradiation with 635 nm, while irradiation with 405 nm indicated a higher photoproduct formation at a higher fluence rate.The photoproduct formation with the irradiation conditions can be exploited for dosimetry estimation and may be used as an additional photosensitizer to improve the diagnostics and treatment efficacies of PDD and PDT. Differences in environmental conditions of the present study from that of a biological environment may result in a variation in the photoproduct formation rate and may limit their clinical utilization in PDD and PDT. Thus, further investigation of photoproduct formation rates in more complex biological environments, including in vivo, is necessary. However, the results obtained in this study will serve as a basis for understanding reaction processes in such biological environments.

Ogbonna SJ ，Masuda K ，Hazama H 《-》

Mass Spectrometric Analysis of the Photobleaching of Protoporphyrin IX Used in Photodynamic Diagnosis and Therapy of Cancer.

Photobleaching and photoproduct formations are considered essential phenomena in improving the efficacy of photodynamic diagnosis and therapy (PDD and PDT). We investigated the photobleaching of protoporphyrin IX (PpIX) by measuring its concentration with mass spectrometry (MS). The reduction in the concentration of PpIX dissolved in dimethyl sulfoxide was measured during PDD and PDT conditions using lasers with wavelengths of 405 and 635 nm, respectively, at a power density of 10, 50 or 100 mW/cm2 . The obtained results were compared with the results of conventional fluorescence spectroscopy and previously reported results. Our results demonstrate the variation in the MS-based photobleaching coefficient of PpIX with the power density, while the fluorescence-based photobleaching coefficient was independent of the power density. The results of MS also show faster photobleaching of PpIX in comparison with that obtained from fluorescence. The difference may be attributed to the change in the fluorescence quantum yield of PpIX with its concentration and the effect of fluorescence emission from the PpIX photoproducts. Thus, an MS-based investigation of the photobleaching poses to be a more stable investigation form. Our finding highlights the importance of recognizing the potential significance of these discoveries in the PDD and PDT dosimetry and efficacy.

Ogbonna SJ ，Hazama H ，Awazu K 《-》

The photosensitizing effect of the photoproduct of protoporphyrin IX.

Ma L ，Bagdonas S ，Moan J 《JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY》

Increased fluorescence observation intensity during the photodynamic diagnosis of deeply located tumors by fluorescence photoswitching of protoporphyrin IX.

Photobleaching of the photosensitizer reduces fluorescence observation time and the intensity of fluorescence emitted for tumor detection during 5-aminolevulinic acid-based photodynamic diagnosis. This study aims to utilize the concept of fluorescence photoswitching, which uses the fluorescence emission from photosensitizer excitation followed by the simultaneous excitation of the photosensitizer and its photoproduct to increase the fluorescence detection intensity during PDD of deeply located tumors. The fluorescence photobleaching of protoporphyrin IX (PpIX) and the formation of its photoproduct, photoprotoporhyrin (Ppp), caused by exposure to 505 nm light were investigated in solution, ex vivo, and in vivo, and the fluorescence photoswitching was analyzed. The fluorescence observations of PpIX and Ppp were performed with 505 and 450 or 455 nm excitation, respectively, which is the suited wavelength for the primary excitation of each fluorophore. Fluorescence photoswitching was observed in all forms of PpIX investigated, and the fluorescence photoswitching time, fluorescence intensity relative to the initial PpIX and Ppp intensity, and fluorescence intensity relative to PpIX after photobleaching were obtained. The dependence of the fluorescence photoswitching time and intensity on the irradiation power density was noted. A fluorescence intensity increase between 1.6 and 3.9 times was achieved with simultaneous excitation of PpIX and Ppp after fluorescence photoswitching, compared with the excitation of PpIX alone. We have demonstrated the potential of fluorescence photoswitching for the improvement of the fluorescence observation intensity for the PDD of deeply located tumors.

Ogbonna SJ ，York WY ，Nishimura T ，Hazama H ，Fukuhara H ，Inoue K ，Awazu K ... -  《-》

Comparative study of phototoxicity of protoporphyrin IX synthetic and extracted from ssp Rattus novergicus albinus rats toward murine melanoma cells.

Reis ER ，Ferreira LP ，Nicola EMD ，Borissevitch I ... -  《-》