Aggregation study of Triarylmethane dyes

HANIEWICZ CINTHIA; VARA JIMENA; ORTIZ CRISTINA

Córdoba

Congreso; Tercera Reunión Internacional de Ciencias Farmacéuticas (RICiFa); 2014

UNITEFA

Photodynamic therapy (PDT) is a non-invasive medical technology that involves three key components: photosensitizer (PS), light and tissue oxygen to generate reactive oxygen species, which cause cells death. Numerous bibliography report that many PS tend to aggregate in aqueous solution. Due to these molecular assemblies present lower photochemical reactivity than the respective monomer, self-aggregation of New Fuchsin (NF) and its di-iodinated derivative (NFI2) were evaluated by UV-Visible spectroscopy. Dye concentration effect in N,N-Dimethylformamide (DMF), DMF: water mixtures and aqueous solution were compared. UV-Visible spectra obtained for NFI2 in DMF showed a unique band with a maximum absorption at 460 nm. When water proportion was increased, a new band at 574 nm was observed and this dye presented maxima absorption at 558 nm and 525 nm in pure aqueous media. Moreover, absorption spectra of NF in DMF showed a single band with a maximum absorbance at 558 nm, while in aqueous solution an increase in absorbance at 495 nm was observed with increasing dye concentration. The absorption band observed for NFI2 in DMF could be assigned to monomeric specie, due to this is a monomerizing solvent and formed J-aggregates (574 nm) when water was additioned. Moreover, high order assemblies were observed in aqueous solution (558 nm and 525 nm). Comparing these results with those obtained for NF, we can conclude that, under the experimental conditions, the monomeric species of NF was not observed. In conclusion, the substitution by iodine in the structure of the dye destabilized the J-aggregate, which allowed identify the monomeric form in DMF as well as to larger aggregates in aqueous solution. Due to NFI2 presented lower tendency to J-Aggregates formation than NF, it could present higher photochemical reactivity than its precursor and could be good candidate for use in PDT.