Allopurinol encapsulated in polycyanoacrylate nanoparticles as potential lysosomatropic carrier: preparation and trypanocidal activity.

The activity of allopurinol-loaded polyethylcyanoacrylate nanoparticles against Trypanosoma cruzi was compared to that of free allopurinol using in vitro cultures of epimastigotes. Ethylcyanoacrylate nanoparticles were prepared by an emulsion polymerization process, and formulations containing different concentrations of allopurinol, polyethylcyanoacrylate and surfactants were investigated and analyzed in size and amount of drug entrapped. The nanoparticles obtained were less than 200 nm in size, as measured by electron microscopy and cytometry. The peak amount of allopurinol entrapped in the nanoparticles was 62.8+/-1.9 microg mg(-1) of nanoparticles using 400 microl of polyethylcyanoacrylate, 200 microl of surfactant (Tween 20) and 20 mg of allopurinol in 50 ml of polymerization medium and the association efficiency was 100.7%. After 6 h of incubation at pH 7.4 the release of allopurinol from the nanoparticles was 7.4%, while at pH 1.2 only 3.1% was released after 4-6 h (t=42.8, P<0.0001). The in vitro studies, using cultures of T. cruzi epimastigotes, demonstrated considerable increases in the trypanocidal activity of the allopurinol-loaded nanoparticles in comparison with a standard solution of allopurinol (91.5 vs. 45.9%) at an allopurinol concentration of 16.7 microg ml(-1). In addition, it was shown that the unloaded nanoparticles, by mechanisms not completely elucidated, had a trypanocidal activity similar to that of standard solutions of allopurinol. To study cytotoxicity, increasing concentrations of unloaded nanoparticles were incubated on vero-line cell cultures. The concentration that killed 50% cells was 200 microg ml(-1), four times higher than that necessary to kill 50% of T. cruzi. It is concluded that the polyethylcyanoacrylate nanoparticles constitute a good carrier of drugs against the T. cruzi. The allopurinol loaded-nanoparticles significantly increased the trypanocidal activity in comparison to the free drug.