Low-temperature manufacturing of fine pharmaceutical powders with
supercritical fluid aerosolization in a Bubble Dryer®*
R. E. Sievers1,**, E. T. S. Huang1, J. A. Villa1, J. K. Kawamoto1,
M. M. Evans1, and P. R. Brauer2
1Department of Chemistry and Biochemistry, 215 UCB,
University of Colorado, Boulder, CO 80309-0215, USA; 2Temco, Inc., 4616
Mingo Rd., Tulsa, OK 74117, USA
Abstract: Aerosols play an important role in thin film deposition,
fine powder generation, and drug delivery. Green processes to form aerosols
are needed to eliminate the use of toxic organic solvents and minimize
the production of liquid wastes and the emission of halogenated and
oxidant-forming organic compounds. We have developed a new patented
process, Carbon Dioxide-Assisted Nebulization with a Bubble Dryer®
(CAN-BD), that can generate a dense aerosol with small droplet and microbubble
sizes that are dried to form particles less than 3 µm in diameter
[19]. The process uses carbon dioxide as an aerosolization aid,
and this permits drying at lower temperature than usually needed in
conventional spray-drying. Intimate mixing of supercritical carbon dioxide
with aqueous protein solutions causes the formation of microbubbles,
which are rapidly dried in less than 5 s. The process is more environmentally
benign than traditionally used methods, and is superior when thermally
unstable materials are being processed. Fine-particle pharmaceutical
powders can be rapidly and easily made by this new CAN-BD process, requiring
less energy and eliminating residues of toxicologically or environmentally
objectionable solvents. Manufacturing dry powders of pharmaceuticals
for pulmonary drug delivery and increasing bioavailability are the purposes
of developing and marketing the new Temco Bubble Dryer.
*Lecture presented at the IUPAC CHEMRAWN
XIV Conference on Green Chemistry:Toward Environmentally Benign Processes
and Products, Boulder,Colorado, USA, 9-13 June 2001. Other presentations
are published in this issue, pp.1229 1330.
**Corresponding author