- Email: [email protected]
Generation of singlet oxygen by UVB-irradiation of endogenous molecules
152 Results: UV-induced papules of actinic keratosis could occur as early as week 12, which could be delayed by ALA-PDT. The median time of tumor-free survival of UV + ALA-PDT group longer than that of UV group (P < 0.05). ALA-PDT could significantly reduce the average number of UV-induced tumors. ALA-PDT could induce cytokine over-expression in UV-induced squamous cell carcinomas. In addition, the mitochondrial apoptotic pathway-associated proteins were significantly increased after ALA-PDT. Conclusion: This in vivo study demonstrated that ALA-PDT could delay and inhibit UV-induced skin carcinomas. Immune regulation and apoptosis may play a role in this process. doi:10.1016/j.pdpdt.2011.03.097 O090 Generation of singlet oxygen by UVB-irradiation of endogenous molecules J. Regensburger, A. Knak, A. Felgenträger, W. Bäumler University Regensburg, Department of Dermatology, Regensburg, Germany UVA radiation (320—400 nm) and UVB radiation (280—320 nm) cause damage of cells or bacteria. Usually, the mechanisms of cell damage are classified to either to DNA strand breaks for UVB radiation or oxidative damage for UVA-radiation. This oxidative damage is predominantly mediated by singlet oxygen, which is generated after absorption of UVA radiation in various endogenous photosensitizers. It has been already suggested that likewise UVB radiation can generate singlet oxygen. The present study aimed to detect and quantify singlet oxygen that was generated by endogenous photosensitizers under UVB irradiation. Different potential endogenous photosensitizers in solution such as fatty acids, vitamins or amino acids were excited by applying the emission of XeCl-Excimer-laser at 308 nm. Singlet oxygen was directly detected by its luminescence in the near infrared spectrum time- and spectral resolved. For most of the investigated molecules, a clear luminescence signal could be obtained by time-resolved measurements. Spectral-resolved measurements in the range of 1150—1400 nm revealed a clear signal maximum at 1270 nm, which confirmed the generation of singlet oxygen. In addition, absorption spectra of the solutions were recorded before and after the laser irradiation to prove the photostability of endogenous photosensitizers and hence their ability to generate singlet oxygen. By comparison with well-known photosensitizers like PNS or TMPyP the singlet oxygen quantum yield of endogenous photosensitizers could be estimated ranging from 0.07 to 0.6. These results demonstrate that singlet oxygen can also be generated by UVB-irradiation by many molecules that are present in cells or tissue. Thus, comparable to UVA radiation, UVB might also induce oxidative damage of cells that may contribute to the hazard of ultraviolet radiation. doi:10.1016/j.pdpdt.2011.03.098 O091 Detection of early cancers by endoscopic fluorescence imaging G. Wagnieres Swiss Federal Institute of Technology (EPFL), ISIC, Lausanne, Switzerland The principle of cancer detection by fluorescence imaging is based on the exploitation of a spectral and/or intensity contrast existing between the lesions and their surrounding normal tissues. Depending on the fluorophore, wavelengths ranging between the UV-A and about 460 nm are used to induce the fluorescence of
Oral Abstracts endogenous fluorophores, i.e. that are responsible for native tissue fluorescence (autofluorescence), fluorophores synthesized in the tissue after external administration of a precursor molecule, specifically porphyrins induced by 5-aminolevulinic acid (ALA) or derivatives thereof, or fluorophores administered as exogenous drugs. Two illustrative applications of endoscopic fluorescence imaging for the detection of early- pre-cancers in the bladder and the tracheo-bronchial tree will be described and critically discussed in this presentation. The detection of early bladder cancer by endoscopic fluorescence imaging in based on the filling of the bladder over a period of about one hour with a 50 ml solution, called Hexvix® (Cysview® in the USA), containing an ALA derivative. This formulation induces the selective production of fluorescing porphyrins in early stage bladder cancers, including those flat ‘‘in situ’’ lesions that are very difficult to detect by classical white light cystoscopy. Illumination of the bladder wall with violet light causes the cancers to light up in the red. However, other tissue abnormalities, such as inflammation, can induce false-positives limiting the specificity of this very sensitive procedure. Similarly, autofluorescence bronchoscopy presents a high sensitivity but its specificity is limited due to metaplasia/hyperplasia and inflammation that produce false positive findings. One approach to characterize fluorescence positive sites in these two organs is to visualize and analyze the texture of their ‘‘micro’’-vascularisation by high magnification reflectance imaging. The performance and optimization of this characterization procedure will be described for these two medical applications, both in terms of magnification and spectral design. doi:10.1016/j.pdpdt.2011.03.099 O093 Optical coherence tomography (OCT) for early diagnosis of tumors and online-control of photodynamic therapy (PDT) Gereon Hüttmann Institute of Biomedical Optics, Peter-Monnik-Weg 4, 23562 Lübeck, Germany Introduction: Optical coherence tomography is a non-invasive imaging modality, which uses backscattered infrared light for the reconstruction of anatomical structures. Doppler imaging can add functional information on tissue perfusion. With an imaging depth of a few millimeters OCT is able to visualize superficial tumors, which may be treated by PDT. In addition OCT has the potential to control the effect of photodynamic treatment. Methods: In the past years we have developed and tested different OCT devices for the diagnosis of early tumors of the bladder, the skin, brain and the vocal fold. In addition we are currently trying to utilize OCT for the control of laser treatments. Results: Two principle mechanisms for identifying early tumors were found. Premalignant and early malignant tissue changes are characterized by thickening of the superficial tissue layer. Polarization OCT can here also improve visualization of the local extension of the tumor. Solid tumors are characterized by change of the microstructure and the local scattering. During brain tumor surgery OCT can show tumor borders and has the potential to quantify the tumor cell density. Conclusion: OCT may improve the diagnosis and staging of early local tumors. This could help in planning of local PDT. The rapid progress in OCT may also allow a therapy control in near future. doi:10.1016/j.pdpdt.2011.03.100
Oral Abstracts endogenous fluorophores, i.e. that are responsible for native tissue fluorescence (autofluorescence), fluorophores synthesized in the tissue after external administration of a precursor molecule, specifically porphyrins induced by 5-aminolevulinic acid (ALA) or derivatives thereof, or fluorophores administered as exogenous drugs. Two illustrative applications of endoscopic fluorescence imaging for the detection of early- pre-cancers in the bladder and the tracheo-bronchial tree will be described and critically discussed in this presentation. The detection of early bladder cancer by endoscopic fluorescence imaging in based on the filling of the bladder over a period of about one hour with a 50 ml solution, called Hexvix® (Cysview® in the USA), containing an ALA derivative. This formulation induces the selective production of fluorescing porphyrins in early stage bladder cancers, including those flat ‘‘in situ’’ lesions that are very difficult to detect by classical white light cystoscopy. Illumination of the bladder wall with violet light causes the cancers to light up in the red. However, other tissue abnormalities, such as inflammation, can induce false-positives limiting the specificity of this very sensitive procedure. Similarly, autofluorescence bronchoscopy presents a high sensitivity but its specificity is limited due to metaplasia/hyperplasia and inflammation that produce false positive findings. One approach to characterize fluorescence positive sites in these two organs is to visualize and analyze the texture of their ‘‘micro’’-vascularisation by high magnification reflectance imaging. The performance and optimization of this characterization procedure will be described for these two medical applications, both in terms of magnification and spectral design. doi:10.1016/j.pdpdt.2011.03.099 O093 Optical coherence tomography (OCT) for early diagnosis of tumors and online-control of photodynamic therapy (PDT) Gereon Hüttmann Institute of Biomedical Optics, Peter-Monnik-Weg 4, 23562 Lübeck, Germany Introduction: Optical coherence tomography is a non-invasive imaging modality, which uses backscattered infrared light for the reconstruction of anatomical structures. Doppler imaging can add functional information on tissue perfusion. With an imaging depth of a few millimeters OCT is able to visualize superficial tumors, which may be treated by PDT. In addition OCT has the potential to control the effect of photodynamic treatment. Methods: In the past years we have developed and tested different OCT devices for the diagnosis of early tumors of the bladder, the skin, brain and the vocal fold. In addition we are currently trying to utilize OCT for the control of laser treatments. Results: Two principle mechanisms for identifying early tumors were found. Premalignant and early malignant tissue changes are characterized by thickening of the superficial tissue layer. Polarization OCT can here also improve visualization of the local extension of the tumor. Solid tumors are characterized by change of the microstructure and the local scattering. During brain tumor surgery OCT can show tumor borders and has the potential to quantify the tumor cell density. Conclusion: OCT may improve the diagnosis and staging of early local tumors. This could help in planning of local PDT. The rapid progress in OCT may also allow a therapy control in near future. doi:10.1016/j.pdpdt.2011.03.100