Heparin-decorated nanostructured lipid carriers of artemether-protoporphyrin IX-transferrin combination for therapy of malaria.

Heme is a prosthetic group of hemoglobin comprising protoporphyrin IX (PPIX) with Fe2+. Studies have shown that modulating heme synthesis pathway in Plasmodium could greatly affect the action mechanism and antimalarial effect of artemisinin and its derivatives. Herein, an intraerythrocytic parasite targeted nanostructured lipid carrier (NLC) was developed for potentiation of artemether (ARM) by combination with PPIX and iron-loaded transferrin (holo-Tf). Firstly, ARM and PPIX were co-loaded into NLCs with high entrapment efficiency. Then, a targeting ligand heparin (HP) was electrostatically adsorbed onto the periphery of NLCs, followed by conjugation with holo-Tf to receive the final formulation Tf-HP-NLC/ARM/PPIX. Tf-HP-NLC/ARM/PPIX exhibited nanoscale particle size (~188 nm) and was relatively stable in simulated gastrointestinal fluids and rat plasma. A sustained drug release characteristic was observed in PBS (pH 7.4). In vitro targeting assay confirmed that Tf-HP-NLC/ARM/PPIX could be specifically and efficiently internalized into intraerythrocytic parasites via HP receptor-meditated endocytosis. Furthermore, due to enhanced intraparasitic accumulation and activated mechanism of ARM, the combinational delivery system Tf-HP-NLC/ARM/PPIX showed increased inhibitory activity against Plasmodium falciparum in culture and enhanced antimalarial effect in Plasmodium berghei-infected murine model, suggesting a promising strategy for development of new therapy based on action mechanism of ARM.