Glycyrrhiza Protein-Based Nanoparticles Enhance the Oral Bioavailability and Analgesic Efficacy of Paeoniflorin.

Purpose: In this study, Glycyrrhiza protein (GP) derived from Glycyrrhiza uralensis Fisch was used as a carrier to prepare Glycyrrhiza protein Paeoniflorin nanoparticles (GP-PF NPs), and its analgesic effects, pharmacokinetic characteristics, and cellular uptake mechanisms were investigated to evaluate its potential to improve the bioavailability of PF. Methods: We prepared GP-PF NPs through heating. A comprehensive structural characterization of the GP-PF NPs was conducted through particle size, zeta potential, electron microscopy, and spectroscopy studies, and their self-assembly mechanism was preliminarily elucidated through molecular dynamics and molecular docking. Subsequently, the analgesic effects of the GP-PF NPs and free PF were evaluated using an acetic acid writhing model, and the in vivo processes were analyzed using pharmacokinetic studies. Finally, the mechanism of transmembrane transport of GP-PF NPs was investigated in Caco-2 cells. Results: The GP-PF NPs showed a consistent spherical shape with a 150 nm diameter and a zeta potential of -84 mV, providing excellent stability. The molecular dynamics and docking results indicated that GP-PF NPs have stable molecular dynamic characteristics. In the writhing mouse models, GP-PF NPs reduced the number of writhing events compared with the PF group, indicating stronger analgesic effect. The pharmacokinetic analysis showed that the GP-PF NPs exhibited a significant 2.60-fold increase in the maximum plasma concentration of PF and a significant 0.95-fold increase in the area under the curve of PF compared with free PF (P<0.05), demonstrating improved oral bioavailability. In vitro uptake and mechanistic studies showed that the GP-PF NPs were transported across membranes through caveolin-mediated endocytosis rather than passive diffusion, significantly improving the oral bioavailability of PF. Conclusion: GP-PF NPs enhanced PF's oral bioavailability and analgesic performance by increasing intestinal absorption through caveolin-dependent endocytosis. Thus, GP may be a potential carrier for increasing the oral bioavailability of PF.