Size controlled production of biodegradable microparticles with supercritical gases.

Polymer microparticles were produced by means of the aerosol solvent extraction system. A solution of 3% w/w poly(L-lactic acid) in dichloromethane was sprayed into supercritical or near critical carbon dioxide gas phase. The mean particle size by volume moderately depended on the nozzle diameter and the spraying pressure used. When the polymer solution was saturated with carbon dioxide up to 5.0 MPa, the particle size and morphology of the particles were unchanged and the product was less agglomerated. Microparticles with mean diameters from 6 to 50 microns were achieved by decreasing the carbon dioxide density from 690 to 250 kg/m3. The surface structure of the particles sprayed in low density carbon dioxide showed cracks and holes. All other particles were non-porous with a smooth surface.