Action of the anti-tumoral zinc(II)phthalocyanine in solution or encapsulated into nanoparticles of poly-ε-caprolactone internalized by peritoneal macrophages

Amanda Santos Franco da Silva Abe, Eduardo Ricci-Júnior, Morgana Teixeira Lima Castelo Branco and Lycia de Brito Gitirana

Abstract

Nanoparticles (NPs) have been used as drug delivery systems (DDS) exhibiting high cell penetration power. As an antitumor photosensitizer, zinc(II) phthalocyanine (ZnPc) was applied in photodynamic therapy (PDT) since its phototoxic activity promotes death of tumor cells in the presence of laser light. Since drugs do not interact only with tumor cells in living organisms, this study aimed to analyze the action of ZnPc-loaded in nanoparticles (ZnPc-NPs) and in solution (free ZnPc) using peritoneal macrophages as a model of non-neoplastic cells that inhabit the tumoral stroma. NPs were produced by emulsion and evaporation of solvent  and characterized by dynamic light scattering and transmission electron microscopy. Assays as 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, light microscopy and laser scanning confocal microscopy were performed to evaluate the drug effects in the presence or absence of laser light applied in PDT. NPs exhibited dimensions between 290 and 350 nm and rounded shape. Empty NP did not affect cell viability, showing that these nanocarriers are biocompatible DDS. Free ZnPc was randomly distributed in the cytoplasm, while ZnPc-NP was preferably located near the nucleus. At 5 μg ml⁻¹, free ZnPc caused greater loss of cell viability in the absence of laser when compared to ZnPc-NPs, in the presence or absence of irradiation. In contrast, free ZnPc and ZnPc-NPs (0.5 μg ml⁻¹) promoted cell death to the same extent in cells treated with laser light or not. This demonstrates that the performance of this drug is dose dependent in its free form, but not in its nanoencapsulated form. Cells irradiated with laser (100 mW) and treated with free ZnPc or with ZnPc-NPs showed morphological changes. These observations show that both free ZnPc and ZnPc-NPs irradiated with laser light cause cell damage in peritoneal macrophages