Design and optimization of liposomal formulation intended for phagocyte targeting in cancer treatment

Abstract

For the first time, we have developed a liposomal formulation for Nω-hydroxy-nor-L-arginine (nor-NOHA). nor-NOHA is an arginase inhibitor that has potential in cancer treatment. The work aimed to develop a formulation that would have high encapsulation efficiency (EE%) for nor-NOHA in liposomes. Optimization of liposomes was conducted stepwise, namely liposomal characteristics were investigated concerning lipid compositions and preparation methods used to prepare liposomes. Three different lipids were utilized to form liposomes by thin film hydration (TFH), reverse phase evaporation (RPE), and active loading of liposomes methods. The lipids were as follows: 1. Distearoylphosphatidylcholine (DSPC). 2. Dipalmitoylphosphatidylcholine (DPPC). 3. Dimyristoylphosphatidylcholine (DMPC). Liposomes were characterized by their size, polydispersity expressed as polydispersity index (PDI), and zeta potential that indicates their surface charge. Additionally, dialysis protocols that were employed to separate liposomal nor-NOHA from free nor-NOHA were also optimized. The encapsulation efficiency (EE%) and release of nor-NOHA from the liposomes were evaluated using LC-MS analysis. We were able to prepare liposomes of a size suitable for intravenous administration. DSPC liposomes consistently demonstrated the highest EE% among the lipid compositions tested, indicating their suitability for nor-NOHA encapsulation. No significant differences were observed in EE% between TFH and RPE manufacturing methods, and both produced satisfactory results. The release of nor-NOHA from liposomes was slower compared to the permeation of the drug from stock solution, with DSPC liposomes showing the slowest release rate followed by DPPC and DMPC liposomes. VIII In conclusion, the choice of lipid composition proved crucial for successful encapsulation, with DSPC being the most effective lipid. The TFH method was selected as the preferred method due to its safety and comparable results to the RPE method. However, more optimizations will be required to further improve encapsulation efficacy. These findings provide valuable insights into optimizing liposomal formulations for nor-NOHA encapsulation, facilitating its potential use in therapeutic applications.