A highly stable norcantharidin loaded lipid microspheres: preparation, biodistribution and targeting evaluation

The purpose of this study was to prepare norcantharidin (NCTD)-loaded lipid microspheres (LMs) with a high encapsulation efficiency (EE) and stability during sterilization. The NCTD-phospholipid complex (NPC) was produced and characterized to increase the lipophilic properties of NCTD and a novel concentrated homogenization method was applied for the preparation of LMs. The results of the UV, DSC and IR investigations confirmed the formation of NPC. The oil-water partition coefficient (log P) of NPC was significantly increased with a value of -1.34 ± 0.06 at pH 7.4, nearly 224 times higher than that of NCTD. A concentrated emulsion was prepared based on a homogenization method and then diluted with water. After optimization of the NPC formation and emulsion preparation process, the EE was dramatically increased from 21.6% to 84.6%, and a highly sterilization stability was achieved with only a minor change in particle size from 168.2 ± 39.4 nm to 173.4 ± 43.5 nm. The tissue distribution of NPCLM was measured after intravenous administration to rats of a dose of 3.9 mg/kg with NCTD injection (NI) as the reference. Considerably increased concentrations of NCTD in the liver, spleen and lung were detected with NPCLM and the values were 1.67, 1.49 and 1.06 times higher than in the NI group, respectively while, in the kidney, the concentration was slightly reduced 0.96-fold. Overall, based on these techniques, this NPCLM with an improved EE and stability offers great promise in clinical applications and industrial-scale production along with a potentially increased targeting effect on the liver and reduced toxicity in the kidney.