Evaluation of optimum conditions for Achyranthes bidentata polysaccharides encapsulated in cubosomes and immunological activity in vitro

Cubosomes, as biocompatible carriers in drug delivery systems, consist of curved bicontinuous lipid bilayers. With a honeycombed structure divided into two internal aqueous channels, cubosomes could be used for many bioactive ingredients. Achyranthes bidentata polysaccharides (ABPs) are isolated from the roots of Achyranthes bidentata, used in Chinese herbal medicine, and present a noticeable effect as an immunomodulator. This study investigates the optimal preparation of combined cubosome-ABP (Cub-ABP) nanoparticles using response surface methodology and explores their characteristics and stability. The encapsulation efficiency of optimized Cub-ABPs was 72.59%. In-vitro stability studies demonstrated the stability of Cub-ABPs and cubosome nanoparticles without ABPs; both were stable for up to 25 days. Safe concentrations of Cub-ABPs and cubosome nanoparticles without ABPs are 104.06 μg/mL and 208.13 μg/mL with comparatively low cytotoxicity against lymphocytes. Moreover, the feasible immunomodulatory effects of Cub-ABPs were determined by evaluating their proliferation and change of CD4+/CD8+ ratio on splenic lymphocytes in vitro. Proliferation and flow cytometry studies revealed that, compared with free ABPs and blank cubosomes, Cub-ABPs proved more effective in promoting lymphocyte proliferation and in triggering the transformation of T-lymphocytes into Th-cells.