Antiparasitic properties of miltefosine-based nanoformulations against protozoan pathogen, Acanthamoeba castellanii

Background: Acanthamoeba castellanii genotype T4 is the causative agent of the progressively increasing sight-threatening Acanthamoeba keratitis and central nervous system infections. Because of the increased prevalence and the ineffectiveness of the current antiamoebic drugs, we synthesized miltefosine poly(lactic-co-glycolic acid) nanoparticles (miltefosine PLGA NP) as a potential potent and biocompatible antiamoebic drug. The advantage to use PLGA NP is to preserve the cells from the toxic effect of miltefosine drug. In particular, miltefosine PLGA nanoformulation offers a better cellular uptake and a sustained drug release compared with the free drug that presents potent cytotoxicity at high concentrations against human colon cancer cell lines. Methods: The miltefosine NP were synthesized using a double emulsion-solvent evaporation method, characterized, and then assessed for their antiamoebic activity against A. castellanii belonging to the T4 genotype. Blank PLGA NP and miltefosine were used as controls. Results: Amoebicidal assays revealed that at 25 and 50 µM, unmodified miltefosine eradicated 83% and 93% of amoebae, respectively. At these same concentrations of 25 and 50 µM, the amount of miltefosine released form PLGA NP formulation was limited to 22.6%. However, it killed 36% and 56% of the protozoa, respectively. Thus, the efficacy of PLGA NP formulation was similar to that of the unmodified miltefosine. Both miltefosine and its PLGA NP significantly inhibited the pretreated amoebae (minimum inhibitory concentration 50% = 37.23 and 55.26 µM, respectively, compared with 147.2 µM of the blank NP; P < 0.05) and reduced amoebae-mediated host cell death. The blank NP and miltefosine NP exhibited minimal cytotoxicity against colon epithelial cell lines. In contrast, the unmodified miltefosine caused 37%, 71%, and 88% of cytotoxicity at 10, 25, and 50 µM, respectively. Conclusion: Overall, these findings suggest that controlling the release of miltefosine from PLGA NP for a short time was almost as effective as miltefosine alone against A. castellanii genotype T4 while reducing host cell toxicity. Hence, this study demonstrates the feasibility of using PLGA NP for the treatment of Acanthamoebic infections.