Co-delivery of buparvaquone and polymyxin B in a nanostructured lipid carrier for leishmaniasis treatment

•The low-water-soluble drug buparvaquone was successfully encapsulated in nanostructured lipid carrier by high-pressure homogenisation.•The co-encapsulation of buparvaquone as the main drug, and polymyxin B as an adjuvant drug, possibly used nanostructured lipid carrier formulation.•Biopolymers chitosan and dextran coating were used for nanoparticle coating as moieties for macrophage-targeted delivery.•In vitro cytotoxicity test revealed formulation safety, even for cationic nanoparticles.•In vitro leishmanicidal test against amastigotes of Leishmania.chagasi showed increased activity of nanoparticles compared with a free drug, up to 3.0-fold. This study aimed to describe the preparation and in vitro evaluation of a surface-modified nanostructured lipid carrier (NLC) using chitosan and dextran for co-delivery of buparvaquone (BPQ) and polymyxin B (PB) against leishmaniasis. The NLC was prepared using high-pressure homogenisation. Polymyxin B binding and surface modification with biopolymers were achieved by electrostatic interaction. In vitro cytotoxicity was assessed in mouse peritoneal macrophages, and leishmanicidal activity in amastigotes of Leishmania infantum. The performance attributes of BPQ-NLC, BPQ-NLC-PB[A−] (anionic) and BPQ-NLC-PB[C+] (cationic) were respectively: Z-average 173.9 ± 1.6, 183.8 ± 4.5 and 208.8 ± 2.6 nm; zeta potential −19.6 ± 1.5, −20.1 ± 1.1 and 31.1 ± 0.8 mV; CC50 583.4 ± 0.10, 203.1 ± 0.04 and 5.7 ± 0.06 μM; IC50 229.0 ± 0.04, 145.7 ± 0.04 and 150.5 ± 0.02 nM. The NLC in vitro leishmanicidal activity showed up to 3.1-fold increase when compared with free BPQ (P