Lipid nanoparticles containing oryzalin for the treatment of leishmaniasis

Oryzalin is a dinitroaniline drug that has attracted recent interest for the treatment of leishmaniasis. Its use as an antiparasitic therapeutic agent is limited by the low water solubility associated with an in vivo rapid clearance, leading to the administration of larger and possibly toxic doses in in vivo studies, and the use of solvents that may lead to undesirable side effects. In the present work oryzalin-containing lipid nanoparticles were produced by a emulsion-solvent evaporation technique using a composition suitable for parenteral administration, i.e., tripalmitin (solid lipid) and a complex mixture of three emulsifying agents (soya lecithin, Tween® 20 and sodium deoxycholate). Physicochemical characterization included the determination of mean particle size, polydispersity index, zeta potential, encapsulation efficiency and DSC studies. Final formulations revealed values of <140 nm (PI<0.2) and zeta potential of ≈-35 mV, as well as encapsulation efficiency >75%. The effects of various processing parameters, such as lipid and surfactant and composition and concentration, as well as the stability during the harsh procedures of autoclaving (121°C/15 min) and freeze-drying were also evaluated. Formulations revealed to be stable throughout freeze-drying and moist-heath sterilization without significant variations on physicochemical properties and no significant oryzalin losses. The use of a complex surfactant mixture proved crucial for preserving formulation stability. Particularly, lecithin appears as a key component in the stabilization of tripalmitin-based oryzalin-containing lipid nanoparticles. Finally, cell viability studies demonstrated that the incorporation of oryzalin in nanoparticles decreases cytotoxicity, thus suggesting this strategy may improve tolerability and therapeutic index of dinitroanilines.