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The acid-catalyzed interaction of melanin with nitrite ions. An EPR investigation

100%

Matuszak Z., Chignell C. F., Reszka K. J.

Nukleonika

2015

vol. 60

issue 3

475-481

The interaction of synthetic dihydroxyphenylalanine (DOPA) melanin (DM) with nitrite ions, NO2−, in the pH 3.6–7.0 range, has been investigated using electron paramagnetic resonance (EPR). We found that especially at pH <5.5 (from ca. 5.5 to 3.6) the reaction of DM with nitrite generated large quantities of new melanin radicals, which implies the involvement of nitrous acid, HNO2, in the radical formation process. Measurements carried out at constant pH of 3.6 showed that the melanin signal increased together with nitrite concentration, reaching a plateau level which was more than fourfold larger compared to the initial signal amplitude observed in a nitrite-free buffer of the same pH. The effects of nitrite and DM concentrations on the melanin-free radical content were also investigated. It is proposed that the radicals are generated by one electron oxidation of melanin ortho-hydroquinone groups to ortho-semiquinones by HNO2 or related nitrogen oxides such as NO2• radicals. The possible involvement of nitric oxide (•NO) and peroxynitrite (ONOO−) in DM oxidation was also examined. In air-free solutions, nitric oxide per se did not generate melanin radicals; however, in the presence of oxygen a marked increase in the melanin EPR signal intensity was observed. This result is interpreted in terms of the generation of radicals via the oxidation of DM by peroxynitrite. Our findings suggest that melanin can function as a natural scavenger of nitrous acid and some nitrous acid-derived species. This property may be relevant to physiological functions of melanin pigments in vivo.

Indocyanine green as a prospective sensitizer for photodynamic therapy of melanomas.

76%

Urbanska K., Romanowska-Dixon B., Matuszak Z., Oszajca J., Nowak-Sliwinska P., Stochel G.

Spectroscopic, photochemical and biological properties of indocyanine green (ICG) are presented. Light over 800 nm is effectively absorbed by ICG. This property as well as photochemical behaviour of ICG make it a very suitable dye for photodynamic treatment of melanoma cells. Cytotoxicity of ICG itself and the effect of photodynamic therapy (PDT) were evaluated by following the growth of human (SKMEL 188) and mouse (S91) melanoma cells. The surviving fraction of the cells irradiated (λex = 830 nm) vs non-irradiated, treated with the same dose of ICG, is significantly decreased (5- to 10-fold). These results show that ICG is a very promising dye for photodynamic therapy of melanomas.

Tritolylporphyrin dimer as a new potent hydrophobic sensitizer for photodynamic therapy of melanoma.

64%

Drzewiecka A., Urbańska K., Matuszak Z., Pineiro M., Arnaut L. G., Habdas J., Ratuszna A., Stochel G.

Acta Biochimica Polonica

2001

vol. 48

issue 1

277-282

We report the synthesis, photochemical and photophysical properties and preliminary studies on biological effect of a new tritolylporphyrin dimer (T-D). Absorption and emission properties of T-D suggest its possible use in photodynamic therapy. T-D is capable of singlet oxygen production with 0.8 quantum yield. It also has a high photostability. The photodynamic properties of the dimer were examined following the growth of SKMEL 188 (human melanoma) cells irradiated with red light (cut off <630 nm). The surviving fraction of the cells decreased about 3-fold (vs. non-irradiated cells) for an 81 J/cm2 dose. Our results suggest that tritolylporphyrine dimer T-D may be an interesting hydrophobic sensitizer for photodynamic therapy.

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2 Acta Biochimica Polonica

1 Nukleonika

1 2015

1 2002

1 2001

3 Matuszak Z.

2 Stochel G.

1 Arnaut L. G.

1 Chignell C. F.

1 Drzewiecka A.

1 Habdas J.

1 Nowak-Sliwinska P.

1 Oszajca J.

1 Pineiro M.

1 Ratuszna A.

1 Reszka K. J.

1 Romanowska-Dixon B.

1 Urbanska K.

1 Urbańska K.

Search results

The acid-catalyzed interaction of melanin with nitrite ions. An EPR investigation

Indocyanine green as a prospective sensitizer for photodynamic therapy of melanomas.

Tritolylporphyrin dimer as a new potent hydrophobic sensitizer for photodynamic therapy of melanoma.