Nanocrystals self-stabilized Pickering emulsion loaded with active components of Tongmai prescription: preparation, characterization and evaluation by Caco-2 cell model

It is of great significance to apply the nanocrystals self-stabilized Pickering emulsion (NSSPE) to traditional Chinese medicine (TCM) compounds, and to study the effect of NSSPE on the oral absorption of various components with different solubility and permeability. In the study, NSSPE of Tongmai prescription was prepared by the high pressure homogenization method with nanocrystals of main active components (puerarin, ferulic acid, salvianolic acid B and tanshinone IIA) of Tongmai prescription as solid particle stabilizers and a mixture of Ligusticum chuanxiong essential oil and Labrafil M 1944 CS as oil phase. The NSSPE had better physical stability than nanocrystals suspension and blank emulsion. The adsorption of nanocrystals on the surface of oil droplets was confirmed by scanning electron microscopy and fluorescence microscopy. The surface adsorption rates of puerarin, ferulic acid, salvianolic acid B and tanshinone ⅡA in NSSPE were 15.40% ± 3.19%, 15.39% ± 5.07%, 10.97% ± 3.70% and 31.51% ± 1.60%, respectively. When solid active components were prepared into nanocrystals suspension, the cellular uptake and transport across Caco-2 cells were increased significantly for puerarin and tanshinone IIA. The uptake rates of ferulic acid, ligustilide and tanshinone IIA in NSSPE were further increased compared with the physical mixture of nanocrystals suspension and oil, and the transports of ligustilide and tanshinone IIA were also significantly improved. The main absorption mechanisms of NSSPE were passive diffusion and caveolin-mediated endocytosis, which were determined mainly by the microstructure of NSSPE. In conclusion, NSSPE could be applied to complicated TCM. The "micro" and "nano" synergistic microstructure with drug nanocrystals adsorbed on the surface of micron-sized oil droplets could not only improve the physical stability of NSSPE, but also promote the absorption of various components in NSSPE, which made NSSPE a promising oral drug delivery system for TCM.