Effects of the position of galactose units to Zn(II) phthalocyanine on the uptake and photodynamic activity towards breast cancer cells

Abstract

Zn(II)-phthalocyanines with tetra-substitution of D-galactose group on non-peripheral (nGalPc) and peripheral (pGalPc) positions have been studied as photodynamic sensitizers. The both complexes are water-soluble and highly aggregated in water and cell culture medium. The non-peripheral galactose units attached to the phthalocyanine macrocycle (nGalPc) lead to far red shift of absorbance maximum at 703 nm as compared to peripherally substituted pGalPc with maximum at 683 nm. The fluorescence maxima of the studied GalPcs were red shifted (8-14 nm) depending on the used solvent as compared to the absorption maxima. The relatively low fluorescence quantum yields in dimethylsulfoxide (0.06 for nGalPc and 0.21 for pGalPc) were determined. The singlet oxygen generation was determined with lower quantum yield for pGalPc (0.21) as compared to nGalPc (0.38). The lack of dark toxicity towards breast cancer cell line (MCF-7) in wide concentration range (0.125 - 10 μM) was observed. The uptake into the tumor cells and the subcellular localization in MCF-7 cells were determined with higher accumulation for pGalPc, compared to nGalPc. The in vitro photodynamic activity of GalPcs towards breast cancer cells was investigated for different dye concentrations and soft light parameters of 635 nm irradiation. The antitumor activity of nGalPc was superior to the pGalPc-induced cytotoxicity, due to higher generation of singlet oxygen and other reactive oxygen species.