Laminarin-Loaded Solid-in-Oil Nanodispersion for Enhanced Non-Invasive Transdermal Immunization

Simple and non-invasive transdermal vaccination is an attractive alternative to conventional injection-based immunization. However, the effectiveness of transdermal vaccines is often constrained by the stratum corneum barrier. Although the use of solid-in-oil (S/O) nanodispersion technology has successfully facilitated skin permeation to induce an immunological response, the antibody titers remain suboptimal. Herein, a dectin-1 selective ligand, laminarin, was used as an immunostimulatory adjuvant to enhance the immune response. S/O nanodispersions loaded with laminarin and ovalbumin (OVA) were systematically developed and characterized in terms of particle size, in vitro OVA release behavior, and skin permeation performance using excised mouse skin. In vivo immunization via transcutaneous administration was performed to evaluate biocompatibility and antigen-specific immunoglobulin-G (IgG) responses. Laminarin-loaded S/O nanodispersions demonstrated long-term stability and efficient ex vivo skin permeability. All the prepared laminarin-loaded S/O nanodispersions showed increased OVA-specific IgG responses compared with the laminarin-free S/O formulation. Among the formulations, the S/O nanodispersion containing OVA and laminarin at a 1:4 weight ratio induced 20-fold higher OVA-specific IgG responses than PBS and 7-fold higher responses than laminarin-free S/O formulations. This study clearly demonstrates the potential of laminarin-loaded S/O nanodispersions as a non-invasive vaccine delivery platform for enhancing antigen-specific antibody responses.