Photosensitizers distribution

Pigmentation e.g. oral contraceptives (chloasma in photosensitive distribution), phenothiazines, heavy metals, amiodarone, chloroquine (pigmentations of nails and palate, depigmentation of the hair), minocycline. 

A 52-year-old man developed pellagra with a classical photosensitive distribution after taking isoniazid for... 

Meyrick Thomas RH, Munro DD. Lichen planus in a photosensitive distribution due to quinine. Clin Exp Dermatol 1986 11(1) 97-101. 

Selectivity of PDT effects may also be enhanced by appropriate manipulation of the illumination process. The spatial control of the illumination is an obvious advantage of PDT, but it is also an important source of the complexity of this modality [48,49]. Since most photosensitizers are non-toxic in the dark at the clinically used doses, only illuminated areas will be damaged by the treatment. The introduction of fiber-optic coupling to lasers has opened a range of opportunities to treat not only superficial lesions, but also more complex body sites, such as the abdominal cavity. An additional way to achieve specificity is the timing of the illumination. Since photosensitizer distribution is dependent on the time after delivery (initially more vascular, later more in tumor cells) [50,51], the time of illumination is an important tool in tailoring PDT for specific applications. 

Figure 16. Detection of photosensitizer fluorescence in vivo, (a) fluorescence spectrum of ALA-PpIX fluorescence at different points in the esophagus within Barrett s (BE) and normal squamous epithelium (SE) at 3 h after 10 mg kg ALA orally (courtesy Dr N. Marcon, Toronto, Canada), (b) fluorescence camera imaging the photosensitizer distribution in tissue during brain tumor PDT, (c) fluorescence in the resection bed at the end of radical brain tumor resection at 24 h after 2 mg kg" Photofrin (courtesy Dr P. Muller, Toronto, Canada).

M.K. Fehr, C.F. Chapman, T. Krasieva, B.J. Tromberg, J.L. McCullough, M.W. Bems, Y. Tadir (1996). Selective photosensitizer distribution in vulvar condyloma acuminatum after topical application of 5-aminolevulinic acid. Am. J. Obstet. Gynecol, 174(3), 951-957. 

Inhomogeneous photosensitizer distribution within the tumor, including a gradual decrease of photosensitizer concentration with distance from blood vessels. ... 

Intermediate (fluence rates in the 10-20 mW/cm range short irradiation times sensitizer binding mainly to mitochondria) Intensive (prolonged irradiation at fluence rates as high as 50 mW/cm photosensitizer distribution in several membranous districts)... 

Katsumura, Kitaura and their coworkers [74] found and discussed the high reactivity of vinylic vs allylic hydrogen in the photosensitized reactions of twisted 1,3-dienes in terms of the interaction in the perepoxide structure. Yoshioka and coworkers [75] investigated the effects of solvent polarity on the product distribution in the reaction of singlet oxygen with enolic tautomers of 1,3-diketones and discussed the role of the perepoxide intermediate or the perepoxide-Uke transition state to explain their results. A recent review of the ene reactions of was based on the significant intervention of the perepoxide structure [76], which can be taken as a quasi-intermediate. 

Photodimerization of isoprene has also been observed using ferrocene as sensitizerproduct distribution in this case was similar to that observed using high-energy photosensitizers. To account for this behavior, the following mechanism was proposed, where 7 indicates a triplet level of isoprene higher than the lowest triplet ( ) ... 

Similarly, the direct [Eq. (11.24)] and photosensitized [Eq. (11.25)] decomposition of diazomethane in the presence of cyclohexene yielded product distributions indicative of greater selectivity in the triplet methylene addition ... 

The iodine-catalyzed photoisomerization of all-trans- a- and (3-carotenes in hexane solutions produced by illumination with 20 W fluorescence light (2000 lux) and monitored by HPLC with diode-array detection yielded a different isomer distribution (Chen et al. 1994). Four cis isomers of [3-carotene (9-cis, 13-cis, 15-cis, and 13,15-cli-r/.v) and three cis isomers of a-carotene (9-cis, 13-cis, and 15-ri.v) were separated and detected. The kinetic data fit into a reversible first-order model. The major isomers formed during the photosensitized reaction of each carotenoid were 13,15-di-d.v- 3-carotene and 13-ds-a-carotene (Chen et al. 1994). 

The isomerization of all-trans-[3-carotene under N2 atmosphere by photosensitization action of eight chlorophyll compounds naturally present in the extracts of green vegetables was investigated by illumination with fluorescent white light (3000 lux) at 12°C to minimize the thermal degradation (O Neil and Schwartz 1995). All chlorophylls showed similar isomeric distribution and efficiency, 9-d.s- 3-carotene is the main isomer formed. On the other hand, the illumination of all-fran.s-(3-car-otene without chlorophylls indicated that the main isomer formed was 13-d.s- 3-carotcnc, probably due to the population of a different triplet state manifold by direct photolysis. 

As will be discussed later, it is possible a4> that the thermolysis involves a metal-nitrene complex whereas the photolysis involves the free nitrene. The product distribution is not affected by the presence of a photosensitizer, but since ferrocene itself is both an efficient triplet quencher as well as a sensitizer 26,27) jt is very difficult to probe the spin state of ferrocenyl nitrene at the moment of reaction. The cycli-zation appears to be a singlet reaction since the yield of 27 in benzene solution is essentially unaffected by oxygen or the presence of hydro-quinone a5>. 

The luminance reaches 100 cd/m2 at 2.5 V with EL efficiency of 2.5 cd/ A. The corresponding external quantum efficiency is about 2% ph/el. At —10 V bias, the photosensitivity at 430 nm is around 90 mA/W, corresponding to a quantum yield of 20% el/ph [135], The carrier collection efficiency at zero bias was relatively low in the order of 10-3 ph/el. The photosensitivity showed a field dependence with activation energy of 10 2 eV [135], This value is consistent with the trap distribution measured in the PPV-based conjugated polymers [136,137],... 

Evenly distributed across pipe multiple injectors, a flash of light on photosensitive fluid... 

As has been pointed out earlier, the kinetic results (ft = k6/k9 independent of the nature of the sensitizer) as well as the observed product distributions obtained in photosensitized oxygenation reactions and in (chemically prepared) singlet oxygen oxygenation reactions (see p. 45, for example) leave but little doubt that 102(1Ag or 1S9+) is the common oxygenating species. ... 

Dimethylcyclohexene (209) is converted to two tertiary hydroperoxides, 210 (12%) and 211 (88%).85,135 1-Methylcyclohexene (30) gives rise to 45% of the tertiary hydroperoxide 31 and to 55% of a non-resolved mixture of secondary hydroperoxides, 52.135 Since the ratio tertiary/secondary hydroperoxides is the same as with limonene (16) and carvomenthene (19), a similar product distribution among the secondary hydroperoxides 32 as was found for 16 and 19 has been assumed. No product distribution has been reported for the photosensitized oxygenation of 1-methylcyclopentene, 213.85,123... 

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