Artesunate-heparin conjugate based nanocapsules with improved pharmacokinetics to combat malaria

Artesunate-heparin conjugate (ART-HEP) based nanocapsules as drug delivery vehicle was developed for intracellular release of ART in malaria therapy. Owing both hydrophobic and hydrophilic moieties, the conjugate was successfully self-assembled into artesunate-heparin nanocapsules (ART-HEP-NCPs) with lower critical micelle concentration (CMC) of about 20 µg/mL. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed that ART-HEP-NCPs has an average hydrodynamic diameter of 112.1 nm with a negatively charged surface (-11.2 mV) and typical micellar nanostructure, respectively. Interestingly, such modification achieved high drug loading efficiency (DLE) of ART (29.3 wt%), which is significantly higher than already reported conventional ART-loaded nanoparticles. The nanocapsules demonstrated lower in vitro ART release under neutral physiological environment (33.81%) but higher release rate was observed in simulated acidic microenvironment (92.74%) in 70 h test. This behavior of ART-HEP-NCPs will facilitate the intracellular release of ART under slightly acidic parasitic food vacuole for effective antimalarial effect. Storage stability and hemolytic studies exhibited that ART-HEP based nanocapsules were stable and safe for intravenous (i.v) injection. Notably, ART-HEP-NCPs has promising internalization into Plasmodium infected red blood cells (iRBCs) and also displayed in vitro inhibitory effect against P. falciparum 3D7 with half-maximal inhibitory concentration (IC₅₀) of 10.16 nM, which was slightly higher than free ART (IC₅₀ 6.27 nM). This expected slightly lower inhibitory effect of polymeric prodrug could be ascribed to the gradual release of ART from the polymer chain over time. More importantly, the in vivo pharmacokinetics study indicated that the nanoscale characteristic of nanocapsules substantially contributed to the extended circulation of ART in blood. In conclusion, such multifunctional ART-HEP-NCPs with higher ART loading and extended half-life could be a promising platform for targeted antimalarial drug delivery.