Evaluation of the efficacy of graphene oxide quantum dots as an ovalbumin delivery platform and adjuvant for immune enhancement

The improved Hummers method was used to obtain GOQDs from flake graphite, which contained rich hydroxyl and carboxyl groups. With the as-fabricated GOQDs in hand, we constructed a GOQDs/OVA nano-vaccine using chicken ovalbumin (OVA) as a model antigen to evaluate the immune efficacy and safety. Results showed that GOQDs/OVA nano-vaccine had high water dispersibility and stability with a diameter of around 5 nm for 30 d. The maximum loading capacity of GOQDs for OVA was about 500 mg center dot g(-1), and release rates of OVA were 74.65% and 56.93% in pH 5.5 and 7.4 after 24 h, respectively, displaying pH stimulus responsive release merits. With the concentration of GOQDs below 500 mu g center dot mL(-1), the biosecurity of GOQDs indicated that they were not causing hemolysis, cell damage, and pathological changes in important tissues. After immunization, GOQDs/OVA nano-vaccines could excite the high levels of immunoglobulin G (IgG), immunoglobulin G1 (IgG1), and immunoglobulin G2a (IgG2a) antibodies and improve secretions of interleukin-1 beta (IL-1 beta), interleukin-4 (IL-2), interleukin- 4 (IL-4), interleukin-6 (IL- 6), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma), compared with the group of OVA alone. Meanwhile, GOQDs promoted an increase in the percentage of CD4+ and CD8+ T lymphocytes in the spleen.