Production of protein-loaded polymeric microcapsules by compressed CO2 in a mixed solvent

In view of developing new drug-delivery systems, microparticles of biocompa tible polymer loaded with protein were produced using a supercritical antis olvent technique. As the polymer, poly(lactic acid) (PLA) of about 100 000 Da was used, whereas insulin was chosen as the protein model. To achieve mi croencapsulation, we started from a homogeneous solution of protein and pol ymer, to which the supercritical antisolvent is added; mixtures of dichloro methane and dimethyl sulfoxide were used to ensure the solubility of both t he polymer and the protein. All experiments were performed in semicontinuou s mode. A preliminary study with PLA alone was done in order to select the best operative condition and to control the particle dimension and their di ameter distribution range, especially with mixtures of the two solvents. Th en, the microspheres of PLA charged with insulin were produced; the average diameters ranged from 0.5 to 2 mum The composition of these particles was determined analytically, and the protein bioactivity was checked.