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Proceedings Paper

Importance of pulsed laser intensity in porphyrin-sensitized NADH photo-oxidation
Author(s): V. Kirveliene; Ricardas Rotomskis; B. Juodka; Algis S. Piskarskas
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Paper Abstract

Porphyrin-type photosensitizers are the subject of intensive studies because of their successful use in photodynamic therapy. The suggestion that singlet molecular oxygen 1o2(1g),produced after the primary photophysical process, is the active agent in the cytotoxic action of porphyrin and light has gained general acceptance. However, this suggestion may not be relevant to the mechanism of intracellular photodamage to cells, where high concentration of reducing agent (i. e. NAD(P)H) and prevailing oxygen levels should favor the pathway, in which semi-oxidized substrate radical and semi-reduced dye radicals are generated. Excitation of the dye using a pulsed laser might lead to biphotonic processes and radical reactions not involving oxygen in the primary steps, thus overcoming tumor anoxia. The main documented results of the use of high peak power laser for photosensitized reactions were: 1, HP-sensitized tryptophan photodegradation induced by 20 MW cm2 peak intensity pulses (5 ns, 630 nm) was identical with that induced by cw light;1 2, protoporphyrin IX dimethyl ether irradiated with 2 GW cm peak intensity pulses (30 ps, 530 nm) showed a yield of photodecomposition substantially higher than that induced by cw irradiation. It is assumed that multi-step excitation is responsible for photodecomposition under powerful picosecond pulses;2 3, irradiation of Rose Bengal and red blood cells suspension with increasing intensities (40 ps, 532 nm) resulted in a decrease in acetyicholinesterase inhibition.3 On the other side the law of time-intensity reciprocity was verified in a wide range using cw irradiation sources.4

Paper Details

Date Published: 1 May 1991
PDF: 3 pages
Proc. SPIE 1403, Laser Applications in Life Sciences, (1 May 1991); doi: 10.1117/12.57384
Show Author Affiliations
V. Kirveliene, Vilnius Univ. (Lithuania)
Ricardas Rotomskis, Vilnius Univ. (Lithuania)
B. Juodka, Vilnius Univ. (Lithuania)
Algis S. Piskarskas, Vilnius Univ. (Lithuania)

Published in SPIE Proceedings Vol. 1403:
Laser Applications in Life Sciences

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