Photosensitizers, and singlet

While the correlation of in vitro photosensitization and singlet oxygen yield was good, exceptions were noted for compounds with low pKa values (near 5.0). Thus, at pH 7.4 (cell culture medium), these compounds exist primarily in the unprotonated imine form. It was shown that this form of the dyes is taken up poorly by the cells. However, it should be noted also that the neutral forms of these compounds absorb near 500 nm, with about half the extinction coefficient of the protonated forms absorbing near the mid-600nm range. 

Bartusik D, Aebisher D, Ghogare A, Ghosh G, Abramova I, Hasan T, Gtcct A (2013) A fiberoptic (photodynamic therapy t) pe) device with a photosensitizer and singlet oxygen delivery probe tip for ovarian cancer cell killing. Photochem Photobiol 89 936-941... 

Foote, C., Photosensitized oxidation and singlet oxygen conseqnences in biological systems, in Free Radicals in Biology, Pryor, W.A., Ed., Academic Press, New York, 1976. 

Comparison of these experimental results with the calculated charge densities (S0 and Si) at the 2 and 3 positions (Table 11.5) shows that this is the expected result. Except for those compounds discussed below, the failure to observe quenching with triplet quenchers and reaction in the presence of a photosensitizer indicated singlet reactions. Compound (89) was found to also undergo benzophenone-photosensitized substitution, indicating that the triplet state of this compound is also reactive. The reaction, however, was less clean than that observed in the direct photolysis. Similarly, 1,6-dinitro-naphthalene was found to undergo both direct and benzophenone-photosensitized substitution ... 

UV irradiation (335 nm) at pH 7.3 showed that some tetracyclines produced significant concentrations of the superoxide anion radical. Demeclocycline (122), oxytetracycline (123) and chlortetracycline (124) were the most active in this. These are all potent photosensitizers and probably give the observed exaggerated sunburn as a result of superoxide production in the skin [90]. Other photochemical experiments demonstrated the production of singlet oxygen. Yields obtained by luminescence measurements in alkaline ethanol were in the order (122) > (120) > (124) > (121) > (125). Chlortetracycline... 

Wang S, Gao R, Zhou F, Selke M (2004) Nanomaterials and singlet oxygen photosensitizers potential applications in photo dynamic therapy. J Mater Chem 14 487-493... 

Singlet oxygen can be chemically or photochemically produced. In the latter case, specific photosensitizers and suitable wavelengths are required. 

It was our intention when this new work began to outline, more fully, the effect of the polymeric structure on the effectiveness of rose bengal as a photosensitizer and to compare the behavior of the polymer-bound dye to the behavior of the dye - free - in solution. In the present paper, therefore, we report on the photochemical and spectral properties of new singlet oxygen sensitizers based on soluble polystyrenes. These new derivatives are referred to as P -RB. 

Sortino et al. reported the use of light irradiation on SAMs supporting the anticancer drug flutamide to study its photoreactivity and product release of nitric oxide. The authors were able to conduct studies in the absence of noxious side effects such as singlet-oxygen photosensitization and observed that nitric oxide production halted when the light was turned off [103], Another photoactive molecule, azobenzene, has recently been exploited in the SAM community to aid in studies on cell adhesion and enzyme inhibition [104], Pearson and coworkers described the use of photoisomerizable SAMs of azobenzene to conduct a series of serine and cysteine protease inhibition experiments. When light of 340-380 nm is used, the... 

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