Preliminary evaluation of the in vitro and in vivo efficacy of a novel nanovesicle-doped nanoemulsion co-loading artemisinin and quercetin as a promising strategy to improve the oral malaria therapy

Since malaria is still a major problem for human health, especially in developing countries, the association of the most effective antimalarial drugs with complementary adjuvants and their loading in suitable delivery nanosystems seems promising to improve therapy effectiveness and minimize side effects. In this study, nanovesicle-doped nanoemulsions were developed and tested for the oral co-delivery of artemisinin and quercetin, using an easy, low-cost, and reproducible method along with cheap and naturally occurring components. The same formulations loading artemisinin or quercetin alone were prepared and used as comparison. Cryogenic transmission electron microscopy confirmed the formation of hybrid dispersions in which nanosized oil droplets coexisted with lamellar vesicles; both were sized ∼61 nm and had a negative zeta potential (∼-47 mV). Formulations were stable when diluted at gastrointestinal pHs and high ionic strength and had low in vitro cytotoxicity against Caco-2 and human umbilical vein endothelial cell lines (<15 %) when the lower concentrations were used (20, 10, 5, and 2.5 μg/mL). Nanovesicle-doped nanoemulsions co-loading artemisinin and quercetin effectively inhibited in vitro the growth of the 3D7 strain of Plasmodium falciparum with a half-maximal inhibitory concentration of 9 ng/mL. Following their oral administration in vivo to Plasmodium yoelii yoelii 17XL-infected mice, they improved the survival rate with respect to the animals treated with only the artemisinin solution. Results were promising since 33 % of mice treated with the nanovesicle-doped nanoemulsions co-loading artemisinin and quercetin completely recovered after clearing parasitaemia below detectable levels and developed immunity to malaria (no parasites were detected in blood upon reinfection without treatment). All in all, this study demonstrates the potential of nanovesicle-doped nanoemulsions as an effective oral delivery strategy for artemisinin-based combination therapies.