Design and Antimalarial Evaluation of Polydopamine-Modified Methyl Artelinate Nanoparticles

Targeted nanodrug delivery systems are highly anticipated for the treatment of malaria. It is known that Plasmodium can induce new permeability pathways (NPPs) on the membrane of infected red blood cells (iRBCs) for their nutrient uptake. The NPPs also enable the uptake of nanoparticles (NPs) smaller than 80 nm. Additionally, Plasmodium maintains a stable, slightly acidic, and reductive internal environment with higher glutathione (GSH) levels. Based on this knowledge, methyl artelinate (MA, a prodrug-like derivative of dihydroartemisinin) nanoparticles (MA-PCL-NPs) were developed using poly(ethylene glycol)-b-poly(ε-caprolactone) (mPEG-PCL) by a thin-film dispersion method and were further coated with polydopamine (PDA) to obtain MA-PCL@PDA-NPs with a particle size of ∼30 nm. The biomaterial PDA can be degraded in slightly acidic and reductive environments, thereby serving as triggers for drug release. MA could generate reactive oxygen species and decrease GSH levels, consequently causing parasite damage. The in vitro release experiment results indicated that the cumulative release percentage of MA from MA-PCL@PDA-NPs was considerably higher in phosphate buffer with 10 mM GSH at pH 5.5 (88.10%) than in phosphate buffer without GSH at pH 7.4 (16.98%). The green fluorescence within iRBCs of coumarin 6, the probe of NPs (C6-PCL@PDA-NPs), could be reduced significantly after adding the NPP inhibitor furosemide (p < 0.001), which demonstrated that MA-PCL@PDA-NPs could be ingested into iRBCs through NPPs. In vivo antimalarial pharmacodynamics in Plasmodium berghei K173-bearing mice showed that the inhibition ratio of MA-PCL@PDA-NPs (93.96%) was significantly higher than that of commercial artesunate injection (AS-Inj, 63.33%). The above results showed that the developed MA-PCL@PDA-NPs possessed pH-GSH dual-responsive drug release characteristics and targeting efficacy for iRBCs, leading to higher antimalarial efficacy against Plasmodium.