Physicochemical characteristics of pentamidine-loaded polymethacrylate nanoparticles: Implication in the intracellular drug release in Leishmania major infected mice

This work describes the preparation, the physicochemical properties, the tolerance and the intracellular trafficking of pentamidine loaded nanoparticles. Pentamidine was bound to the polymer by ionic interaction. This interaction involved the carboxylic acid functions of methacrylic acid (10% of the polymer) and the amine groups of the drug. Pentamidine fixation and release were pH dependent. An acidic pH led to a decrease of fixation or a release. At pH 5, which is the pH value of lysosomes and parasitophorous vacuoles, the release reached up to 50%. At this pH value, pentamidine is ionized and therefore can not traverse the biological membranes. Unloaded nanoparticles and pentamidine-loaded nanoparticles were tested in vitro on U937 cells and no cytotoxicity was observed. In vivo, in Leishmania infected mice, no significant weight loss was found. Ultrastructural studies showed the different steps of drug loaded nanoparticles trafficking inside Leismania-infected Kupffer cells. The nanoparticle uptake by macrophagic cells led to the location of nanoparticles inside phagocytosis vacuoles which fused with primary lysosomes to form secondary lysosomes. Ultimate fusion of secondary lysosomes containing nanoparticles with parasitophorous vacuoles was also observed. Nanoparticles were identified close to amastigotes but internalization by the parasite was not observed.