Preparation, Characterization, and Immune Activity of <i>Viola philippica</i> Polysaccharide PLGA Nanoparticles

Recent pharmacological studies have demonstrated that Viola philippica polysaccharide (VPP) exhibits a modulating effect on immune activity. However, its utilization has been hampered by its large particle size and complex spatial structure. Polylactic-co-glycolic acid (PLGA) copolymer is recognized as an effective drug delivery carrier, exhibiting excellent biochemical properties. In this experiment, VPP was encapsulated with PLGA to form VPP PLGA nanoparticles (VPP-PLGA NPs). The morphological structure and immunomodulatory effects of VPP-PLGA NPs were evaluated. The particle size of VPP-PLGA NPs was reduced compared to VPP, and the optimal preparation conditions were as follows: The ratio of the organic phase to the internal aqueous phase was 8:1, the ratio of the external aqueous phase to the primary emulsion was 7:1, and the concentration of PLGA was 20 mg/mL. Additionally, VPP-PLGA NPs significantly increased the nitric oxide (NO) content, IL-4, and IFN-γ levels in RAW264.7 cells, as well as enhanced their phagocytic activity. Furthermore, VPP-PLGA NPs were found to increase NO content and IFN-γ secretion in bone marrow-derived dendritic cells (BMDCs). These findings suggest that VPP-PLGA NPs could enhance the immune activity and may be utilized as a VPP delivery system for inducing strong immune responses.