Objective: To prepare an O/W ginseng saponins-based nanoemulsion and investigate its amplified immune response.
Method: The formulation of ginseng saponins-based nanoemulsion was optimized via the range of nanoemulsion zone in phase diagrams and the solubility of ginseng saponins. Its physicochemical properties were investigated, including morphology, particle size distribution, pH, viscosity and stability. Ginseng saponins-based nanoemulsion as adjuvant was co-administrated with a model antigen ovalbumin (OVA) in mice. Two weeks after the boosting, the serum levels of OVA-specific antibody and its isotypes were determined.
Result: The optimized ginseng saponins-based nanoemulsion formulation consisted of ginseng saponins, IPM, Cremophor RH 40, glycerol and water (with the weight ratio of 2 : 4 : 17.8 : 17.8 : 58.4), which was a light yellow fluid. The shape of droplets was spherical under transmission electron microscopy with an average diameter of 72.20 nm and a polydispersity index of 0.052. The viscosity and pH value of it were 4.20 s and 6.02, respectively. And it showed good stability. When co-administered with OVA, no obvious side effects were observed in the mice immunized with ginseng saponin-based nanoemulsion. The serum levels of IgG, IgG1 and IgG2a antibody in the group of ginseng saponin-based nanoemulsion immunized mice was significantly increased compared to the groups of OVA and the saline solution of ginseng saponin. Compared with the adjuvant aluminium hydroxide, the serum levels of IgG and IgG1 antibodys in the groups of ginseng saponins-based nanoemulsion had no significant difference, but the level of IgG2a was obviously higher.
Conclusion: ginseng saponin-based nanoemulsion could amplify the Th1 and Th2 immune responses, and can be used as the vaccine adjuvant.