Photodynamic therapy effect

G. Jori, C. Fabris (1998). Relative contributions of apoptosis and random necrosis in tumor response to photodynamic therapy effect of the chemical structure of Zn(II)-phthalocyanines. J. Photochem. Photobiol. B Biol., 43, 181-185. 

Given stringent requirements for effective sensitizers and the desire to use wavelengths further to the red for therapeutic appHcations, definition of newer sensitizers has been a principal area of research since about 1987. Expanded theoretical and experimental understanding of photophysics has been a key element in identifying new classes of potential sensitizers (93—98). Research has focused on cationic derivatives of Nile Blue (93), metaHo-phthalocyanines (94), naphthalocyanines (95), chlorin-type compounds (96), expanded ring porphyrinoids (97), as well as porphyrins other than hematoporphyrin and its derivatives (98). This work has also been reviewed (10,91). Instmmentation for photodynamic therapy has been reviewed (99). 

There is also evidence that individual chlorophyll derivatives exhibit cytostatic and cytotoxic activities against tumor cells. Studies have been started on electronic structures, in particular the electronic state of the phorphyrin macrocycle, and progress in this area is expected regarding photodynamic therapy for tumors, since the strong absorption of hght in the visible region is effective for laser excitation. Nevertheless, httle is known to date about the influences of peripheral groups on the electronic state of the macrocycle n system in chlorophyll derivatives. ... 

Photodynamic therapy is based on a phenomenon known as photodynamic action, or the photodynamic effect, which are terms used to describe the damage to living tissue caused by certain photosensitizers in the presence of visible light and oxygen. Again, there is an extensive historical record, which has been reviewed several times during the 1990s.4,9-15... 

Over the past 20 years, the principal biomedical application for (free or metal-substituted) porphyrins has been Photodynamic Therapy (PDT), with extensive literature in the area including a number of comprehensive reviews (114-116). Porphyrins offer scope for optical imaging as they are potent fluorophores in the red region of the electromagnetic spectrum. Although, to date, the emphasis has been on their therapeutic effects, due to their... 

Fingar VH, Wieman TJ, Karavolos PS, Doak KW, Ouellet R, van Lier JE (1993) The effects of photodynamic therapy using differently substituted zinc phthalocyanines on vessel constriction, vessel leakage and tumor response. Photochem Photobiol 58 251-258. 

Abstract The supramolecular composites containing fullerenes C60 immobilized at nanosilica were used for the design of the molecular systems that can be an effective agent in cancer photodynamic therapy (PDT). In particular, it was shown that photoexcited fullerene C60-containing composites decrease viability of transformed cells, intensify the process of lipid peroxidation (LPO) in cell membranes and accumulation of low-molecular weight DNA fragments, and also decrease the activity of electron-transport chain of mitochondria. 

The obtained results have shown that cell cultures of tumor origin are more sensitive to phototoxic damage induced by solid-phase C60 than the cultures of nontumor origin (normal or spontaneously transformed ones) - the effect that could be interesting for the perspective of possible fullerene usage in photodynamic therapy of tumors. 

Work during the last ten years on photodynamic therapy (PDT) has established the methodology as effective in the early treatment of cancers, and in the treattnent of certain skin disorders and viral infections. Approval by the regulatory authorities for sensitisers in this process began in 1993 when Canada allowed the use of Photofrin (QLT Therapeutics), an action followed later by most countries around the world. Now many other companies have sensitisers at late stage clinical dials (2001), see below in Table 4.5. An excellent introduction to the chemistry of this topic is provided in the book written by Bonnett. ... 

The use of photochemical treatment to stimulate translocation of endocytosed macromolecules into the cytosol is a novel technology to improve therapeutic efficacy. The technology as described in this review is derived from photodynamic therapy (PDT) and is named PCI. In both cases a photosensitizer is used in combination with light to exert the treatment effects. The basic mechanisms of the photosensitizers and their tissue interaction in combination with light will be described with emphasis on the properties of the photosensitizers used in PCI before describing the use of PCI for cytosolic delivery of macromolecules. 

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