Hemolytic toxicity caused by primaquine (PQ) is a high-risk condition that hampers the wide use of PQ to treat liver-stage malaria. This study demonstrated that phospholipid-free small unilamellar vesicles (PFSUVs) composed of Tween80 and cholesterol could encapsulate and deliver PQ to the hepatocytes with reduced exposure to the red blood cells (RBCs). Nonionic surfactant (Tween80) and cholesterol-forming SUVs with a mean diameter of 50 nm were fabricated for delivering PQ. Drug release/retention, drug uptake by RBCs, pharmacokinetics, and liver uptake of PFSUVs-PQ were evaluated in invitro and invivo models in comparison to free drugs. Additionally, the stress effect on RBCs induced by free PQ and PFSUVs-PQ was evaluated by examining RBC morphology. PFSUVs provided >95% encapsulation efficiency for PQ at a drug-to-lipid ratio of 1:20 (w/w) and stably retained the drug in the presence of serum. When incubated with RBCs, PQ uptake in the PFSUVs group was reduced by 4- to 8-folds compared to free PQ. As a result, free PQ induced significant RBC morphology changes, while PFSUVs-PQ showed no such adverse effect. Intravenously (i.v.) delivered PFSUVs-PQ produced a comparable plasma profile as free PQ, given i.v. and orally, while the liver uptake was increased by 4.8 and 1.6-folds, respectively, in mice. Within the liver, PFSUVs selectively targeted the hepatocytes, with no significant blood or liver toxicity in mice. PFSUVs effectively targeted PQ to the liver and reduced RBC uptake compared to free PQ, leading to reduced RBC toxicity. PFSUVs exhibited potential in improving the efficacy of PQ for treating liver-stage malaria.
Keywords: liver targeting; liver-stage malaria; phospholipid-free small unilamellar vesicles (PFSUVs); primaquine (PQ); red blood cells (RBCs).