title: Modifying excitation light dose of novel photosensitizer PVP-Hypericin for photodynamic diagnosis and therapy.
abstract: Conventional photodynamic diagnosis (PDD) and therapy (PDT) makes use of photosensitizers that are excited by continuous light irradiation of specific wavelengths. In the case of PDT, the overdose of continuous excitation may lead to an expansion of necrosis in cancer cells or morbidity in healthy surroundings. The present study involves 5-h fluorescence imaging of living human lung epithelial carcinoma cells (A549) in the presence of a novel photosensitizer, PVP-Hypericin (PVP: polyvinylpyrrolidone) to optimize the excitation light doses for PDD and PDT. A number of time-lapse imaging experiments were performed using a low-power blue LED operating in either continuous or pulsed mode. The irradiances I(*) were 1.59, 6.34 and 14.27mW/cm(2), the pulse lengths L being 0.127, 1.29, 13, 54.5, 131 and 60,000ms. Then, the relation between irradiance, various exposure times, photobleaching and phototoxicity of PVP-Hyperycin was investigated. Results showed a nonlinear relationship between the amounts of excitation dose, cell viability and toxicity. For all experimental I(*), minimal phototoxicity and photobleaching was detected when cells were exposed to brief pulses of light (L⩽13ms). On the other hand, pulsed excitation with I(*)=14.27mW/cm(2) and L=131ms induced high percentages of apoptosis comparable to the long exposures of L=60,000ms and the continuous excitation. Thus, replacement of continuous excitation by a pulsed method seems applicable for PDT.
authors: University of Vienna, Faculty of Physics, Physics of Physiological Processes, Boltzmanng. 5, A-1090 Vienna, Austria. rozhin.penjweini@uhasselt.be
authors: Rozhin
authors: R
authors: Penjweini
authors: Hans G
authors: HG
authors: Loew
authors: Maria
authors: M
authors: Eisenbauer
authors: Karl W
authors: KW
authors: Kratky
mesh_terms: D000873:Anthracenes; D000970:Antineoplastic Agents / Q000494:pharmacology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D003952:Diagnostic Imaging / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D005452:Fluoresceins / Q000378:metabolism; D006801:Humans; D008027:Light; D010569:Perylene / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D038761:Photobleaching; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000494:pharmacology / Q000627:therapeutic use; D011205:Povidone / Q000494:pharmacology / Q000627:therapeutic use*; D013388:Succinimides / Q000378:metabolism; D013997:Time Factors
chemical_list: C087165:5-(6)-carboxyfluorescein diacetate succinimidyl ester; D000873:Anthracenes; D000970:Antineoplastic Agents; D005452:Fluoresceins; D017319:Photosensitizing Agents; D013388:Succinimides; D010569:Perylene; C004965:hypericin; D011205:Povidone