Comparison of photophysical properties of two zinc (II) phthalocyanines in dimethylformamide or into liposomes

MIRETTI, M; TEMPESTI, T; PRUCCA, C.; BAUMGARTNER,MT

Congreso; XIII ELAFOT; 2017

Photodynamic therapy (PDT) utilizes light in combination with a photosensitizing agent to induceseveral phototoxic reactions. Both components are innocuous if they act separately but incombination, are able to induce injury and cellular death [1]. Photodynamic reaction involves a lightabsorption by a photosensitizer to excite the molecule to the excited singlet state. This excited stateundergoes intersystem crossing to the long-lived triplet state, which can react with molecular oxygeninducing reactive species such as singlet oxygen, superoxide, and radicals. These reactive species canoxidize the surrounding bioorganic molecules leading to cell death [2].Phthalocyanines (Pcs), second generation photosensitizers, are characterized with far red wavelengthabsorption (>670 nm), long triplet life time (~1 ms), and high quantum yields of singlet oxygengeneration (>0.2) [3]. Pcs have been used as a treatment for a variety of cancers and non oncologicalapplications, such as actinic keratosis and mycosis fungoides.Due to hydrophobic character of Pcs, intravenous treatment is greatly hampered. Liposomalpreparations are currently used as an effective delivery system in experimental studies and clinicaltrials [4].In this work the photophysical properties of two Pcs (ZnPc and TAZnPc) in DMF(dimethylformamide) solution or carried into DipalmitoylPhosphatidylCholine (DPPC)-cholesterolliposomes in PBS (Phosphate Buffer Saline) and their effectiveness on glioblastoma cells wereevaluated. 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 λmax (702 nm)compared to ZnPc (670 nm). Fluorescence of ZnPc: λex:640 nm, λem:675 nm, TAZnPc λex:670 nm,λem:711 nm. Regarding singlet oxygen production in DMF, TAZnPc presents a ΦΔ of 0.45, similar tothat of non-modified ZnPc (0.56). In liposomes formulation didn´t show shift in wavelengthabsorption and emmision.DMF solution as well as liposomes were diluted in DMEM and DMEM/FBS. Fluorescence and UVVismesurements 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 wereadministrated in DPPC-cholesterol liposomes rather than in DMF.