Inhalable peptide powders produced by a Nano Spray Dryer B-90

Purpose. To produce inhalable powders of pharmaceutical peptides by using a new generation, high yield, spray-dryer. Methods. Capreomycin sulfate and bacitracin powders were produced using a new generation spray-dryer (Nano Spray Dryer B-90, BÜCHI Italia S.r.l., Milan, Italy). The instrument differs from conventional spray-dryers for the nebulising system, that uses a piezoelectric actuator incorporating a thin, perforated, stainless steel membrane (4.0, 5, and 7.0 μm pore size). An ultrasonic frequency (60 kHz) causes membrane vibration with the generation of droplets in the micron/submicron range. In addition, a long drying chamber, where is possible to obtain a laminar flow, coupled with an electrostatic particle collector, permit high yields even with small volume samples. The obtained particles were characterized for their mean size and distribution (Accusizer C770, and Nicomp 380 autocorrelator, PSS Inc., Santa Barbara, CA), and morphology using scanning electron microscopy (SEM) (Philips XL30 SEM, Heindoven, NL). Results. Following preliminary experiments, the best working parameters were individuated and reported hereafter: inlet temperature, 110°C; air flow, 100 L/min; pressure, 45 mbar; pump, 1; spray, 100%. Peptides were solubilised in deionized water and the obtained solutions were sprayed using the 5 μm pore size membranes. Peptide powders were in the micrometer range with size suitable for inhalation (2-5 μm) and, under this experimental setup, only a small fraction was in the submicron range. SEM analysis evidenced the presence of spherical particles with a smooth surface. Particle diameters were compatible with that obtained by dynamic light scattering and single particle optical sensing technique. The employed method had in both cases a particle recovery higher than 85%. Conclusion. The Nano Spray Dryer B-90 has been successfully employed for the production of pharmaceutical peptide powders suitable for pulmonary delivery.