Figures & data
Figure 1. Overview of spray drying process [Adapted from Kanojia et al. (reference 11)] . The liquid vaccine excipient mixture enters the nozzle along with nitrogen via 2 different inlets. The mixing of liquid and nitrogen occurs just before end of the nozzle resulting in formation of aerosols. The heating mantle is located around the nozzle and the actual temperature is displayed on the equipment control panel (not shown). The dried particles enter the cyclone, following the airflow as depicted due to the special design of the cyclone. The nitrogen is separated, filtered and dehumidified before re-circulating back into the system and powder ends up in the collection vessel.
![Figure 1. Overview of spray drying process [Adapted from Kanojia et al. (reference 11)] . The liquid vaccine excipient mixture enters the nozzle along with nitrogen via 2 different inlets. The mixing of liquid and nitrogen occurs just before end of the nozzle resulting in formation of aerosols. The heating mantle is located around the nozzle and the actual temperature is displayed on the equipment control panel (not shown). The dried particles enter the cyclone, following the airflow as depicted due to the special design of the cyclone. The nitrogen is separated, filtered and dehumidified before re-circulating back into the system and powder ends up in the collection vessel.](/cms/asset/80ce2ea4-873a-4bac-9544-2aca414aedd8/khvi_a_1356952_f0001_c.jpg)
Table 1. Spray drying process parameters affecting product characteristics. The process parameters influence different stress factors experienced by the antigen. Shear stress (‡), heat stress (*) and dehydration stress (†).
Table 2. Summary of spray dried vaccine formulations with the process parameters and key findings (inlet: inlet drying temperature, outlet: outlet temperature, fr: feed flow rate into the system, atom: atomization pressure and n.a: not available).
Figure 2. Pulmonary delivery of spray dried powders (Adapted from references 89 and 99, with permission from Elsevier). A. PuffHaler® Device (AktivDry LLC, USA): Air from the activation bulb lofts vaccine powder from the disperser into the reservoir once the pressure threshold of the burst valve is exceeded. The reservoir filled with powders are directly inhaled through a mouthpiece with adults and adolescents or mask (not shown) placed over the nose and mouth with infants and young children. B. Solovent™ Device (Becton, Dickinson & Company, USA): Air from the activation syringe ruptures the membrane of the vaccine capsule, releasing vaccine powder in to the reservoir. Patient inhales it through the mask. C. Twincer (University of Groningen, The Netherlands): A dry powder inhaler for pulmonary delivery. The vaccine powder is placed between the plates in an aluminum blister for moisture protection. The powder can be made available for inhalation by removal of a pull off blister strip.
