In vitro anti-trypanosomal activity of 3-(aryl)-6-piperazin1,2,4-triazolo[3,4-a]phthalazines-loaded ultrathin polymeric particles: effect of polymer type and particle size†

Abstract

3-(Aryl)-6-piperazin-1,2,4-triazolo[3,4-a]phthalazines have shown great potential as leishmanicidal agents. Herein, we prepared a series of PLGA-, PLA- and PCL-based-microparticles/nanoparticles of different particle sizes and loaded them with active 3-(aryl)-6-piperazin-1,2,4-triazolo[3,4-a]phthalazines TF1 and TF2. The synthesized microparticles/nanoparticles seek to improve the leishmanicidal activity of 3-(aryl)-6-piperazin-1,2,4-triazolo[3,4-a]phthalazines and extend its effect to the T. cruzi parasite. The encapsulates were prepared using a microemulsification method, achieving an encapsulation percentage between 89% and 99% for PLGA-, PLA- and PCL-microparticles/nanoparticles. The encapsulation of triazolo-phthalazines was confirmed through UV-Vis or EDX analyses. From SEM analysis, two nanoparticle or microparticle/nanoparticle system-loaded TF1 or TF2 with mean sizes of 250, 400, 600–900 or 900–2000 nm were obtained for each of PLGA, PLA and PCL polymeric matrices. TEM analysis revealed that all the prepared microparticles/nanoparticles consisted of particles and not spheres. The microencapsulates/nanoencapsulates showed an acceptable drug release under physiological conditions, achieving a continuous release for up to 96 hours for most of the studied cases. From biological evaluation, encapsulation with PLGA and PLA showed a positive effect against the in vitro model of both parasites showing a decrease in their EC₅₀ values compared with free compounds. Conversely, no improvement in trypanosomaticidal activity was found with PCL encapsulation. Importantly, it was found that that either the small particle size of the capsulate system or facile drug release favored anti-trypanosomatid activity. The three polymeric matrices showed a discrete but slight increase in toxicity toward J774.1 macrophages compared to free compounds. This may be associated with the facile penetration of the polymeric matrix across the macrophage membrane, favoring against intracellular forms of parasites. This study shows that either the particle size or the type of polymer represent key issues for improving the trypanosomaticidal activity of polymeric nanoformulations.