Nano-in-microparticle powders for mucosal vaccination – understanding the particle forming process

Judith Heidland & Regina Scherließ

Nanoparticulate antigen encapsulation to induce a local immune response upon nasal application is a promising alternative to the commonly used parenteral vaccination. In this study, the particle forming process of such nanoparticles, consisting of chitosan and a low viscosity sodium carboxymethylcellulose sodium salt – produced via ionic gelation, is illustrated. Ovalbumin as model antigen was incorporated into the particles for some experiments. Different qualities of chitosan (varying degree of deacetylation as well as molecular weight) were investigated regarding their influence on the resulting particle sizes, showing an increase of size for qualities with a higher molecular weight. For selected qualities a closer look into the particle forming process was taken to improve its understanding. For this, gel permeation chromatography and 1H-NMR experiments were performed to assess whether changes in the chitosan regarding molecular weight or degree of deacetylation occur during particle formation, to get an idea about the “reactive share” of the chitosan used. To gain further information regarding the binding mechanisms between the components isothermal titration calorimetry experiments were performed finding differences between the different chitosan qualities. Moreover, a different counterion (sodium deoxycholate) was utilised to detect potential differences depending on the counterion (large carboxymethylcellulose sodium salt, approximately 90 kDa vs. small sodium deoxycholate, 0.4 kDa) regarding the particle size as well as the zeta potential. Nanoparticles can be incorporated in a microparticulate stabilising matrix to allow respiratory application and deposition.

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