Liposomes of dimeric artesunate phospholipid: A combination of dimerization and self-assembly to combat malaria

Artemisinin and its derivatives are highly effective drugs in the treatment of P. falciparum malaria. However, their clinical applications face challenges because of short half-life, poor bioavailability and growing drug resistance. In this article, novel dimeric artesunate phospholipid (Di-ART-GPC) based liposomes were developed by combination of dimerization and self-assembly to address these shortcomings. Firstly, Di-ART-GPC conjugate was synthesized by a facile esterification of artesunate (ART) and glycerophosphorylcholine (GPC) and confirmed by MS, 1H NMR and 13C NMR. The conjugate was then assembled to form liposomes without excipient by thin film hydration method. The assembled Di-ART-GPC liposomes have typical multilamellar vesicle structure with bilayer morphology as determined by transmission electron microscopy (TEM) and cryogenic electron microscopy (cryo-EM). Moreover, the liposomes displayed an average hydrodynamic diameter of 190 nm and negative zeta potential at −20.35 mV as determined by Zetasizer. The loading capacity of ART was calculated approximately 77.6% by weight with this liposomal formulation after a simple calculation. In vitro drug release and degradation results showed that the Di-ART-GPC liposomes were stable in neutral physiological conditions but effectively degraded to release parent ART in simulated weakly acidic microenvironment. In vivo pharmacokinetics study revealed that Di-ART-GPC liposomes and conjugate have longer retention half-life in bloodstream. Importantly, Di-ART-GPC liposomes (IC50 0.39 nM) and the conjugate (IC50 1.90 nM) demonstrated excellent in vitro antiplasmodial activities without causing hemolysis of erythrocytes, which were superior to free ART (IC50 5.17 nM) and conventional ART-loaded liposomes (IC50 3.13 nM). Furthermore, the assembled liposomes resulted in enhanced parasites killing in P. berghei-infected mice in vivo with delayed recrudescence and improved survivability, compared to free ART administration. Based on these encouraging results, Di-ART-GPC liposomal formulation could be a replacement to parent ART in clinical malarial therapy after thorough investigation.