Characterisation of Zinc Oxide as an Alternative to Aluminium Hydroxide in Nasal Vaccination
Marie Hellfritzsch & Regina Scherließ
Department of Pharmaceutics and Biopharmaceutics, Kiel University, Grasweg 9a, 24118 Kiel, Germany
To evoke a mucosal immune response via nasal administration a safe antigen needs an adjuvant. Because aluminium hydroxide, a commonly used adjuvant for intramuscular administration, is not effective on mucosa and has other disadvantages, Zinc Oxide (ZnO) is evaluated as an alternative in this study. The aim of the present work is to characterise ZnO, especially with regard to adsorption capacity of Ovalbumin (OVA) and aerodynamic characterisation for nasal administration. That is why adsorption capacity, desorption profile and particle size distribution of ZnO are measured. With lower adsorption capacity but similar desorption profile ZnO shows comparable properties to the reference material aluminium hydroxide. Due to its particle size in the nanoscale and its resulting high surface area, ZnO has a high tendency to build agglomerates. In this study, a nasal dry powder device (UDS powder device) is used to disperse and apply ZnO. Particle sizes that are more suitable for nasal administration than for pulmonary administration are the result of the low dispersion forces in the device. Aerodynamic characterisation confirms these results with almost 90 % ZnO in the nasal expansion chamber of the NGI by using the UDS powder device. Part of the characterisation are also saturation solubility and pH studies at different pH levels. ZnO is slightly soluble in acidic solutions, but solubility is decreasing with increasing pH. At neutral pH, ZnO is practical insoluble. Compared to solubility the effect of increasing pH to an almost neutral pH after 24 h is independent of starting pH. The study gives a first idea of ZnO as a compound for adsorbed vaccines.