Objective To prepare paeoniflorin-glycyrrhiza protein self-assembled nanoparticles (Pae-GP/SAN) with good bioavailability and investigate its intestinal absorption mechanism. Methods In this study, glycyrrhiza protein (GP) was used as the carrier to prepare Pae-GP/SAN by ultrasonic dispersion method. The formulation and preparation process were optimized using average particle size, polydispersity index (PDI), encapsulation efficiency, and drug loading as evaluation indicators, and the prepared nanoparticles were characterized. A rat in situ single-pass intestinal perfusion model was established to investigate and compare the intestinal absorption behaviors of paeoniflorin solution (Pae/Sol), paeoniflorin-glycyrrhiza protein physical mixture (Pae-GP/PM), and Pae-GP/SAN. Additionally, an aggregation-caused quenching (ACQ) fluorescent probe was used to observe the intestinal absorption of GP/SAN by confocal laser scanning microscopy (CLSM), aiming to initially clarify its penetration-enhancing mechanism. Results The optimized Pae-GP/SAN had an average particle size of (178.2 ± 6.3) nm, a PDI of 0.152 1 ± 0.011 2, a ζ potential of (−14.91 ± 1.13) mV, an encapsulation efficiency of (36.45 ± 2.32)%, and a drug loading of (21.70 ± 1.30)%, with a uniform spherical micromorphology. Intestinal perfusion experiments indicated that the absorption efficiency of Pae-GP/SAN in the ileum was superior to that in the jejunum (P < 0.05, 0.01). The formation of nanoparticles significantly promoted the absorption of paeoniflorin. Moreover, the absorption parameters of high mass concentration Pae-GP/SAN were significantly higher than those of low mass concentration Pae-GP/SAN (P < 0.001), while mass concentration had no significant effect on the absorption of Pae/Sol and Pae-GP/PM. Transporter inhibitor intervention experiments showed that indomethacin and reserpine had no significant effect on the absorption of the three formulations. Verapamil significantly increased the absorption of Pae/Sol and Pae-GP/PM (P < 0.01, 0.001) but had no significant effect on Pae-GP/SAN. CLSM observations confirmed that GP/SAN can be absorbed by the intestine in the form of intact nanoparticles. Conclusion Pae-GP/SAN can be endocytosed and absorbed by the intestine as intact nanoparticles, effectively evading the barrier effect of P-gp efflux protein, thereby significantly improving the oral bioavailability of Pae.

paeoniflorin  /  glycyrrhiza protein  /  traditional Chinese medicine self-assembled nanoparticles  /  intestinal perfusion  /  intestinal absorption