RESUMO
Here, we report the syntheses of two pentamethine cyanine dyes containing quinolinium rings and substituted with either hydrogen (3) or bromine (4) at the meso carbon. The electron withdrawing bromine atom stabilizes dye 4 in aqueous buffer, allowing complex formation to occur between the dye and double-helical DNA. UV-visible, CD, and fluorescence spectra recorded at low DNA concentrations suggest that dye 4 initially binds to the DNA as a high-order aggregate. As the ratio of DNA to dye is increased, the aggregate is converted to monomeric and other low-order dye forms that interact with DNA in a non-intercalative fashion. The brominated dye 4 is relatively unreactive in the dark, but, under 707-759 nm illumination, generates hydroxyl radicals that cleave DNA in high yield (pH 7.0, 22 °C). Dye 4 is also taken up by ES2 ovarian carcinoma cells, where it is non-toxic under dark conditions. Upon irradiation of the ES2 cells at 694 nm, the brominated cyanine reduces cell viability from 100 ± 10% to 14 ± 1%. Our results suggest that 2-quinolinium-based carbocyanine dyes equipped with stabilizing electron withdrawing groups may have the potential to serve as sensitizing agents in long-wavelength phototherapeutic applications.
Assuntos
Carbocianinas/química , Clivagem do DNA , DNA de Neoplasias/química , Corantes Fluorescentes/química , Neoplasias Ovarianas/metabolismo , Fotoquímica , Compostos de Quinolínio/química , Apoptose , Proliferação de Células , Feminino , Fluorescência , Humanos , Neoplasias Ovarianas/patologia , Espectroscopia de Luz Próxima ao Infravermelho , Células Tumorais CultivadasRESUMO
With the goal of designing a lysosomal phospholipase mimic, we optimized experimental variables to enhance Ce(IV) -assisted hydrolysis of phosphatidylcholine (PC) liposomes. Our best result was obtained with the chelating agent bis-tris propane (BTP). Similar to the hydrolytic enzyme, Ce(IV) -assisted hydrolysis of PC phosphate ester bonds was higher at lysosomal pH (â¼4.8) compared to pH 7.2. In the presence of BTP, the average cleavage yield at â¼pH 4.8 and 37 °C was: 67±1 %, 5.7-fold higher than at â¼pH 7.2 and roughly equivalent to the percent of phospholipid found on the metal-accessible exo leaflet of small liposomes. No Ce(IV) precipitation was observed. When BTP was absent, there was significant turbidity, and the amount of cleavage at â¼pH 4.8 (69±1 %) was 2.1-fold higher than the yield obtained at â¼pH 7.2. Our results show that BTP generates homogenous solutions of Ce(IV) that hydrolyze phosphatidylcholine with enhanced selectivity for lysosomal pH.
Assuntos
Cério/química , Lipossomos/química , Fosfatidilcolinas/química , Trometamina/análogos & derivados , Concentração de Íons de Hidrogênio , Hidrólise , Lisossomos/química , Trometamina/químicaRESUMO
We have synthesized symmetrical carbocyanine dyes in which two 4-quinolinium rings are joined by a pentamethine bridge that is meso-substituted with H or Cl. Irradiation of the halogenated dye at 830 nm produces hydroxyl radicals that generate DNA direct strand breaks. This represents the first reported example of DNA photocleavage upon single photon excitation of a chromophore at wavelengths above 800 nm.