Phytosterol ester-based liposomes for improved oral delivery of puerarin: enhanced stability and mucus penetration

Puerarin (Pue), an isoflavone with diverse pharmacological activities, exhibits poor oral bioavailability due to its low solubility and permeability. To improve its oral delivery, phytosterol ester (PE) was employed as a membrane stabilizer to replace cholesterol (CH) in liposomal formulations. Two Pue-loaded nanoliposomes, CH-Pue-NLs and PE-Pue-NLs, were successfully prepared via ethanol injection. PE-Pue-NLs exhibited a particle size of 219.80 ± 1.81 nm, a zeta potential of 48.76 ± 1.65 mV, and an encapsulation efficiency (EE) of 74.59 ± 1.25%, outperforming CH-Pue-NLs. FTIR and DSC analyses confirmed successful encapsulation of Pue. During 15 days of storage at 4 °C, PE-Pue-NLs showed superior physical stability, maintaining PDI < 0.3, zeta potential > +35 mV, and higher EE (59.42 ± 1.17%) than CH-Pue-NLs, which exhibited marked aggregation and drug leakage. In simulated gastrointestinal fluids, PE-Pue-NLs demonstrated enhanced structural stability and a slower biphasic release profile, with a lower cumulative release in simulated intestinal fluid at 6 h (36.87 ± 1.47%) compared with CH-Pue-NLs (50.29 ± 2.57%). Furthermore, PE-Pue-NLs exhibited reduced binding with mucin and a 1.32-fold higher apparent permeability coefficient (Papp) in Transwell studies, indicating enhanced mucus penetration. In vivo intestinal fluorescence imaging further confirmed improved mucosal permeability of PE-Pue-NLs. These findings suggest that phytosterol ester is a promising alternative to cholesterol for constructing liposomes with improved gastrointestinal stability and intestinal permeability for poorly soluble bioactive compounds.