Mucosal immunisation is one opportunity of non-invasive administration. The respiratory tract comprises immune competent cells, which are part of the MALT (mucosa associated lymphoid tissue) and thereby represents an excellent possibility to induce both local and systemic immune reactions. Since alum is ineffective as adjuvant to enhance the immune response of safe antigens on the mucosa, two different formulations with zinc oxide (ZnO) as an alternative to alum are investigated in this study. In order to combine the advantages of nano- and microparticles, a composite particle was formulated using spray drying, whereby the model antigen is incorporated in the spray dried formulation. Round, wrinkled particles with visible ZnO particles in the matrix were gained. With an D50 > 10 µm the dry powder formulations are theoretically suitable for nasal administration, but the nasal deposition profile tested with the Next Generation Impactor (NGI) showed a remarkable post-nasal fraction. Nonetheless, it is worth considering the complete deposition profile, because MALT is located not only in the nose but also in lower parts of the respiratory tract as bronchus and larynx as well. As the formulation increased the viscosity of simulated nasal mucus and because of the adhesive properties of the formulation, the residence time in the nose may be increased and even small amounts of the formulation may induce a good immune response. Further investigations with regard to immunological reactions and characteristics of the dry formulation will be carried out.
Spray dried formulations with ZnO are suitable for nasal application. Due to an increase in viscosity and the adhesive nature of the formulations, residence time in the nose may be increased. This promising characteristic could result in a better dissolution, absorption and finally immune reaction.