[Preparation and in vitro evaluation of rhein-loaded PEG-PCL-PEI nanoparticles]

This study was aimed to synthesize the polyethyleneglycol-polycaprolactone-polyethyleneimine (PEG-PCL-PEI) three block polymer material, prepareRhein (RH)-loaded PEG-PCL-PEI nanoparticles(PPP-RH-NPS), and then evaluate their physical and chemical properties and biological characteristics in vitro. PEG-PCL-PEI polymer was obtained by adopting thering-opening polymerization and Michael addition reaction, and their physical and chemical properties were analyzed by using NMR and gel permeation chromatography. PEG-PCL-PEI was then used as the carriers to prepare PPP-RH-NPS by applying spontaneous emulsification solvent diffusion method. The results showed that molecular weight of PEG-PCL-PEI polymer was 9.5×103, and critical micelle concentration was 0.723 mmol•L⁻¹. PPP-RH-NPS had pale yellow, opalescence faade, round and smooth without aggregation, formed of (118.3±3.6) nm in particle size with PDI of (0.19±0.08), Zeta potential of (6.3±1.5) mV, entrapment efficiency of (93.64±5.28)%, and drug loading of (8.57±0.53)%. The accumulative release percentage of PPP-RH-NPS was 75.92% in 48h, and the release profiles in PBS conformed to the Higuchi equation： Q=0.121 6t1/2+0.069 5 (R²=0.887 4), presenting slow release characteristics. Within the scope of the 0-0.05 mmol•L⁻¹, the nanoparticles had no obvious hemolysis on rabbit red blood cells and toxicity on HK-2 cells. In the investigation of uptake efficiency by flow cytometry, nanoparticles can be absorbed into cells quickly and internalized within 30 minutes fully, with a high uptake efficiency. In confocal laser scanning microscope observation, the nanoparticles can escape from lysosome into cytoplasm. Herein, this study synthesized the PEG-PCL-PEI polymer and prepared PPP-RH-NPS successfully; the nanoparticles showed uniform particle size, higher encapsulation efficiency and drug-loading rate, slow release characteristics, quick uptake and internalization, lysosome escape property and good biocompatibility. PPP-RH-NPS will be a promising pharmaceutical formulation for further development.