Encapsulation of p-THPP into Nanoparticles: Cellular Uptake, Subcellular Localization and Effect of Serum on Photodynamic Activity¶

Abstract

The cellular uptake, localization and efflux of meso-tetra-(4-hydroxyphenyl)porphyrin (p-THPP)-loaded nanoparticles have been studied in EMT-6 tumor cells. The effect of blood serum on photocytotoxicity has also been evaluated. Sub-130 nm nanoparticles based on poly(D,L-lactide-co-glycolide) (PLGA) (50:50 PLGA and 75:25 PLGA) and poly(D,L-lactide) (PLA) have been examined in comparison with free p-THPP. For all formulations tested, uptake of photosensitizer into cells was dependent on concentration, time and temperature. All nanoparticulate formulations accumulated within the cells to a greater extent relative to free drug. Indeed, the fluorescence intensities measured on EMT-6 cells treated with p-THPP-loaded nanoparticulate formulations were at least two-fold higher than those obtained with free dye. Furthermore, the highest accumulation level was found with PLGA nanoparticles. Fluorescence microscopy revealed that endocytosis is a major intracellular sequestration mechanism of these p-THPP formulations and that these were localized into early and late endosomes. The efflux study performed on both nonirradiated and irradiated cells indicated that free and p-THPP-loaded nanoparticles gradually escaped from EMT-6 cells as a function of time. This was more pronounced when cells were treated with nanoparticles and irradiated, reflecting important photodamage. It was also found that regardless of the nanoparticulate formulations tested, p-THPP photocytotoxicity was influenced by the concentration of the serum.

Nanodrug applications in photodynamic therapy

“…Examples of encapsulation of hydrophobic photosensitizers into nanomaterials are polymeric nanoparticles [88], e.g., a hydrophobic photosensitizer meso-tetra(phydroxyphenyl)porphyrin (m-THPP) encapsulated into polymeric nanoparticle poly(D,Llactide-co-glycolide) [89,90], dendrimer phthalocyanine (DPc)-encapsulated polymeric micelles (DPc/m) [32], polymeric protoporphyrin IX micelles [55], and organically modified silica-based nanoparticles [91] entrapping the photosensitizing anti-cancer drug 2-devinyl-2-(1-hexyloxyethyl) pyropheophorbide [59] have been used.…”

Photobiological and Ultrastructural Studies of Nanoparticles of Poly(lactic-co-glycolic acid)-Containing Bacteriochlorophyll-aas a Photosensitizer Useful for PDT Treatment

“…Simillar conclusions were observed by Konan et al (2003) with sub-130 nm nanoparticles of PLGA loaded with Meso-tetra(4-hydroxyphenyl)porphyrin (p-THPP) with incubating time of 15 or 30 min on EMT-6 mammary tumor cells evaluated subcellular localization and efflux of EMT-6 tumor mammary cells in comparison with the free dye. These results suggest that for each cell line the incubation time is an important parameter to be investigated to obtain the best results in PDT.…”

Cell Delivery of Therapeutic Nanoparticles

“…130,131,193–195 Once the particles are internalized, intracellular trafficking is dependent on the physicochemical properties of the particles, such as surface charge, polymer coat, and surface modifications. 85 Konan and coworkers observed that meso-tetra-(4-hydroxyphenyl)porphyrin ( p -THPP)-PLGA nanoparticles were accumulated intracellularly 1.3-fold better than p -THPP-poly (D,L-lactide) (PLA) nanoparticles, 196 suggesting that the presence of glycolic acid, imparting a hydrophilic character to the nanoparticle, enhanced cellular sequestration. Cerium nanoparticles were taken up by a clathrin-dependent mechanism and trafficked throughout the cell, supporting the use of these nanoparticles as intracellular scavengers of reactive oxygen and reactive nitrogen species.…”