Microencapsulation Using Supercritical Carbon Dioxide

A new method for rapid expansion from supercritical solution with a nonsolvent (RESS-N) to obtain polymer microparticles containing proteins, medicine and inorganic microparticles is presented in the following. On this method, a suspension of microparticles such as protein in carbon dioxide(CO2) containing a cosolvent and dissolved polymer is sprayed through a nozzle into atmosphere. Polymer solubility, such as that of poly(ethylene glycol) and poly(methyl methacrylate), in CO2 was found to increase significantly through use of low molecular weight alcohols as cosolvents. Subsequent to expansion, the particles do not agglomerate, since pure cosolvent functions as nonsolvent for the polymer. Polymer coating thickness on about core materials, mean particle diameter and particle size distribution can be controlled according to polymer feed composition.