Polymeric nanoparticles favor the in vitro dermal accumulation of Protoporphyrin IX (PpIX) with optimal biocompatibility and cellular recovery in culture of healthy dermal fibroblasts after Photodynamic Therapy

Abstract

The aim of this study was to investigate (i) the cutaneous accumulation of photosensitizer (PS) protoporphyrin IX (PpIX) encapsulated in nanoparticles (Np) by confocal laser scanning microscopy (CLSM) in animal model skin (ii) the in vitro dark cytotoxicity and phototoxicity of PpIX-Nps in dermal fibroblast cells (L929 fibroblast cells and (iii) the recovery of cell viability after PDT. The CLSM has shown higher PS concentration in the superficial skin; the stratum corneum (SC) for both encapsulated and free PpIX for all times evaluated (4 h, 8 h and 24 h). Although with lower PS accumulation in the deeper layers of the skin, ie; Epidermis + Dermis (EP + D) after 8 h the PS accumulation was significantly higher when encapsulated in Np. In brief, PpIX-Np was not cytotoxic to fibroblast cells in the dark (˜ 100% viable cells; excellent biocompatibility) and in the presence of light 8 h post incubation (phototoxicity) reached CC50 = 7.01 μg / ml (compared to free PpIX, CC50 = 0.84 μg / ml) meaning that PpIX in Nps were phototoxic to cells as expected; however at higher concentrations than free PpIX. Moreover, PpIX-Np has shown 100% of cell recovery 24 h post PDT in the fibroblast cells, indicating photoactivation protection of PpIX by the Nps in the healthy cells.