Understanding the Effect of Surface Chemistry of Mesoporous Silica Nanorods on Their Vaccine Adjuvant Potency

Mesoporous silica nanoparticles are reported as adjuvants in nanovaccines in generating robust antigen-specific immunity. However, the effect of surface chemistry in initiating and modulating the immune response remains largely unexplored. In this study, mesoporous silica nanorods (MSNRs) are modified with NH₂ and C₁₈ groups to investigate the influence of surface functional groups (OH, NH₂, and C₁₈) on their adjuvant efficacy. It is found that compared to OH and NH₂ groups, the hydrophobic C₁₈ modification significantly enhances antigen uptake by antigen presenting cells and endosomal–lysosomal escape in vitro, dendritic cells, and macrophages maturation ex vivo, and elicits secretion of interferon-γ level and antibody response in immunized mice. Moreover, bare MSNR and MSNRNH₂ exhibit T-helper 2 biased immune response, while MSNRC₁₈ shows a T-helper 1 biased immune response. These findings suggest that the surface chemistry of nanostructured adjuvants has profound impact on the immune response, which provides useful guidance for the design of effective nanomaterial based vaccines.