Carboxylated nanodiamond-mediated NH2-PLGA nanoparticle-encapsulated fig polysaccharides for strongly enhanced immune responses in vitro and in vivo.

Nanodiamonds (NDs), which are safe carbon nanomaterials, have been used for the transmission of DNA, proteins and drugs. The feasibility of utilizing NDs to deliver NH2-PLGA nanoparticle-encapsulated fig polysaccharides for strongly enhanced immune responses has not been clearly studied. In this study, we aimed to use NDs as carriers to deliver NH2-PLGA nanoparticle-encapsulated fig polysaccharides for strongly enhanced immune responses. ND particles with a diameter of 5 nm were functionalized by surface carboxylation and covalently conjugated with NH2-PLGA nanoparticle-encapsulated fig polysaccharides. NDs-PLGA-FP/OVA could promote antigen uptake and lymphocyte proliferation, increase the expression levels of MHC II, CD80 and CD86, and upregulate the ratio of Th1/Th2 cells in immunized mice. NDs-PLGA-FP/OVA could also upregulate the IL-17 signalling pathway for further immunological enhancement. NDs-PLGA-FP/OVA induced increased TNF-α, IFN-γ, IL-4, and IL-6 cytokine secretion and the levels of OVA-specific antibodies (IgG). These findings demonstrate that NDs-PLGA-FP/OVA have the potential to serve as an effective vaccine delivery and adjuvant system to induce vigorous and long-term immune responses.