Aktiv-Dry (United States)

This paper describes a newly patented CAN-BD (Carbon dioxide Assisted Nebulization with a Bubble Dryerr®) process, utilizing dense CO2 to micronize solutes to fine particles in a diameter range of 0.6 to 5 μm. The potential applications of this process are in thin film deposition, fine powder generation, and drug delivery. The fine particles are generated by (a) intimately mixing dense CO2 (at super- or sub-critical conditions) and a liquid solution (containing a dissolved solute of interest) in a small volume tee at about 83 bar and room temperature, (b) expanding this mixture through a 10 cm long capillary tube flow restrictor (with inner diameters of 50, 74 or 100 μm) into a drying chamber at atmospheric pressure to generate an aerosol, and (c) drying the aerosol plume with preheated air or nitrogen gas at temperatures between 10 and 65°C to form dry powders. Fine dry powders of disaccharide sugars, proteins, water-soluble and alcohol-soluble drugs have been generated with a lab CAN-BD unit (using a glass drying chamber with a volume of one to two liters) at a liquid flow rate of 0.3 to 2 mL/min. In a scaled up prototype unit (utilizing a 170-liter drying chamber with a thin stainless steel wall), aqueous solutions with 10% solute have successfully been nebulized and dried at a liquid flow rate of 20 mL/min. This paper presents experimental results of nebulizing aqueous solutions of mannitol and myo-inositol utilizing a lab CAN-BD unit. The effect of certain operating parameters on particle characteristics has been investigated. The particle size (a) decreases with reduction in solute concentration, and (b) decreases with increase in the ratio of dense CO2 to aqueous solution flow rates.