Generation of fine powders of recombinant human deoxyribonuclease using the aerosol solvent extraction system

Purpose. To investigate the feasibility of using the Aerosol Solvent Extraction System (ASES) to produce fine powders of recombinant human deoxyribonuclease (rhDNase), lysozyme-lactose and rhDNase lactose powders from aqueous based solutions. Methods. The ASES technique using high pressure carbon dioxide modified with ethanol or ethanol and triethylamine was used for the generation of rhDNase powders and protein-lactose powders from aqueous based solutions. Particle size, morphology, size distributions, crystallinity, and powder aerosol performance were measured. The biochemical integrity of the processed rhDNase was assessed by testing the monomer content and the degree of deamidation. Results. RhDNase precipitated as spherical particles in the size range between 50 and 500 nm. The primary nano-sized particles were agglomerated to micron-sized clumps of particles during the precipitation process. The median particle size and the fine particle fraction were functions of the operating temperature and the nozzle system used. RhDNase was substantially denatured in the ASES process using carbon dioxide modified with ethanol as anti-solvent. However almost complete recovery of the monomer was achieved using carbon dioxide modified with ethanol-triethylamine as an anti-solvent. Lysozyme-lactose and rhDNase-lactose powders were also precipitated as agglomerated spheres using the ASES process. The powders were amorphous except for those with lactose content higher than 45%. Conclusions. Micron-sized particles of rhDNase suitable for inhalation delivery were generated from aqueous based solutions using the modified ASES technique. The biochemical integrity of the rhDNase powder is a function of the antisolvent and the operating temperature.