Adjuvant comprising nano-aluminum hydroxide pickering emulsion with polysialic acid for enhanced vaccination.

Adjuvants are pivotal components in vaccine formulations, serving to augment the extensiveness, breadth, and duration of antigen-specific immune responses. Conventional emulsions represent one successful category of vaccine adjuvant, while still with the thermodynamically unstable issue. In this study, a novel polysialic acid (PSA)-loaded Nano-Alum stabilized Pickering emulsion (NAPE or NAPE/PSA) formulation was prepared by anchoring Nano-Alum at the oil/water interface, subsequently integrating PSA and Ovalbumin (OVA) onto the Nano-Alum surface. The findings revealed that the innovative NAPE demonstrated exceptional physical stability and high protein loading efficiency, maintaining these properties for up to 52 weeks at both 25 °C and 40 °C, underscoring the robust stability of the NAPE adjuvant formulation. In vitro assessment indicated that NAPE and NAPE/PSA possess high cellular compatibility, enhancing the cellular adhesion and facilitating the endocytosis of OVA in RAW264.7 and DC2.4 cells, and upregulated TNF-α expression compared with Alhydrogel in RAW 264.7 and DC 2.4 cells. Moreover, both NAPE and NAPE/PSA elicited a potent and enduring OVA-specific immune response, achieving compared IgG1, IgG and IgG2a titers to the commercial adjuvant at day 42, and IgG and IgG2a titers performed a continuous increase trend over time after immunization. These outcomes suggest that NAPE or NAPE/PSA could serve as a potential carrier, offering dual functionalities in adjuvant activity and antigen delivery.