Comparison of photophysics properties of two zinc (II) phthalocyanines

MARIANA MIRETTI; TOMAS C. TEMPESTI; CESAR PRUCCA; MARIA TERESA BAUMGARTNER

Carlos Paz

Encuentro; XIII ELAFOT; 2017

Photodynamic therapy (PDT) utilizes light in combination with a photosensitizing agent to induce several phototoxic reactions. Both components are innocuous if they act separately but in combination, are able to induce injury and cellular death [1]. Photodynamic reaction involves a light absorption by a photosensitizer to excite the molecule to the excited singlet state. This excited state undergoes intersystem crossing to the long-lived triplet state, which can react with molecular oxygen inducing reactive species such as singlet oxygen, superoxide, and radicals. These reactive species can oxidize the surrounding bioorganic molecules leading to cell death [2].Phthalocyanines (Pcs), second generation photosensitizers, are characterized with far red wavelength absorption (>670 nm), long triplet life time (~1 ms), and high quantum yields of singlet oxygen generation (>0.2) [3]. Pcs have been used as a treatment for a variety of cancers and non oncological applications, such as actinic keratosis and mycosis fungoides.Due to hydrophobic character of Pcs, intravenous treatment is greatly hampered. Liposomal preparations are currently used as an effective delivery system in experimental studies and clinical trials [4].In this work the photophysical properties of two Pcs (ZnPc and TAZnPc) in DMF (dimethylformamide) solution or carried into DipalmitoylPhosphatidylCholine (DPPC)-cholesterol liposomes in PBS (Phosphate Buffer Saline) and their effectiveness on glioblastoma cells were evaluated. In vitro studies were performed using Dulbecco´s Modified Eagle´s Medium (DMEM) supplemented with Fetal Bovine Serum (FBS) as cell culture.In DMF, absorption spectra UV-Vis for TAZnPc presents a higher red-shifted ?Émax (702 nm) compared to ZnPc (670 nm). Fluorescence of ZnPc: ?Éex:640 nm, ?Éem:675 nm, TAZnPc ?Éex:670 nm, ?Éem:711 nm. Regarding singlet oxygen production in DMF, TAZnPc presents a ?³?¢ of 0.45, similar to that of non-modified ZnPc (0.56). In liposomes formulation didn?Lt show shift in wavelength absorption and emmision.DMF solution as well as liposomes were diluted in DMEM and DMEM/FBS. Fluorescence and UV-Vis mesurements presented only changes in the intensity of absorbtion or emmision. In in vitro studies both Pcs show an increase in their photosensitizing activity when they were administrated in DPPC-cholesterol liposomes rather than in DMF