Potent in vivo antimalarial activity of water-soluble artemisinin nano-preparations

Abstract

Artemisinin is a remarkable compound whose derivatives and combinations with multiple drugs have been utilized at the forefront of malaria treatment. However, the inherent issues of the parent compound such as poor bioavailability, short serum half-life, and high first-pass metabolism partially limit further applications of this drug. In this study, we enhanced the aqueous phase solubility of artemisinin by encapsulating it in two nanocarriers based on the polymer polycaprolactone (ART-PCL) and lipid-based Large Unilamellar Vesicles (ART-LIPO) respectively. Both nanoformulations exhibit in vitro parasite killing activity against Plasmodium falciparum with the ART-LIPO performing at comparable efficacy to the control drug solubilized in ethanol. These water-soluble formulations showed potent in vivo antimalarial activity as well in the mouse model of malaria at equivalent doses of the parent drug. Additionally, the artemisinin-PCL nanoformulation used in combination with either pyrimethamine or chloroquine increased the survival of the Plasmodium berghei infected mice for more than 34 days and effectively cured the mice of the infection. We highlight the potential for polymer and liposome-based nanocarriers in improving not only the aqueous phase solubility of artemisinin but also concomitantly retaining its therapeutic efficacy in vivo as well.

Fig. 1. Characterization of artemisinin loaded nanoparticles. (A) Particle size distribution of ART-PCL. (B) Particle size distribution of ART-LIPO particles. The DLS plots were drawn from the mean of results obtained from three technical replicate runs. (C) SEM image of ART-PCL. (D) SEM image of ART-LIPO. L1 and L2 are diameters of individual particle.

Fig. 2. Artemisinin (ART) based nano formulations have potent anti-malarial activity. Dose response curves of (A) artemisinin native, (B) artemisinin PCL (C) artemisinin liposomes were generated by incubating synchronized ring stage parasites with increasing concentrations of the drug formulation for a period of 48 h and the parasitemia was estimated by SYBR green I assay.

Fig. 3. In vivo antimalarial activity of artemisinin nano-formulations. Drug treatment was given for a period of 5 days. Artesunate (50 mg kg⁻¹) was used as a positive control. (A) Shows mean parasitemia at various days post infection upon treatment with artemisinin PCL and artemisinin liposome nano-formulations. (B) Represents average parasitemia at day 9 post infection upon treatment with ART-PCL and ART-LIPO. Values are plotted as means ± the standard error of the mean, SEM (n = 4 mice/group). Statistical significance was established after performing one-way ANOVA followed by Sidak's multiple comparisons test where *p < 0.05, **p < 0.01, ***p < 0.001.

Fig. 4. In vivo antimalarial activity of artemisinin PCL nano-formulation given in combination with chloroquine or pyrimethamine. Artemisinin (50 mg kg⁻¹) was given for 3 days via oral route. Chloroquine (20 mg kg⁻¹) and pyrimethamine (10 mg kg⁻¹) were given for 2 days via intraperitoneal injections. (A) Shows mean parasitemia at various days post infection upon treatment with artemisinin PCL nano-formulation and the partner drugs. (B) Represents average parasitemia at day 14 post infection. (C) Kaplan Meier survival curve showing the survival of the combination and monodrug treated mice against an untreated control for a period of 28 days. Values are plotted as means ± the standard error of the mean, SEM (n = 4 mice/group). Statistical significance was established after performing one-way ANOVA followed by Sidak's multiple comparisons test where *p < 0.05, **p < 0.01, ***p < 0.001.