Ultrasonic spray-drying process factors and their effect on the particle size of a water-based peptide-solution

Particle size plays an important role when using spray-dried powders for preparing solid oral dosage forms. In this study, a 25 kHz ultrasonic nozzle was used for spray-drying of a low-concentration water-based peptidesolution to increase the particle size of the resulting spray-dried powder compared to a bi-fluid nozzle. Firstly, the effect of the nozzle type (ultrasonic or bi-fluid nozzle) on particle size was investigated, where it was shown that the ultrasonic nozzle increased the spray-dried particle size. Secondly, using a Design of Experiments (DoE) approach, it was investigated which process parameters, namely inlet air temperature, feed rate and gas flow, affect the particle size using an ultrasonic nozzle at a fixed feed concentration of 10 mg/mL. Here, it was found that feed rate was the predominant parameter affecting particle size, and an optimum was found at 4 g/min. Lastly, the effect of the feed concentration on the particle size using an ultrasonic nozzle was investigated, where it was shown that the particle size increased with increasing feed concentration. Overall, it was shown that large particles with a d(10) > 10 mu m can be obtained using an ultrasonic nozzle with a frequency of 25 kHz.