Industrial & Engineering Chemistry Research, Vol.51, No.25, 8616-8623, 2012
Continuous Supercritical Emulsions Extraction: Packed Tower Characterization and Application to Poly(lactic-co-glycolic Acid) plus Insulin Microspheres Production
The continuous supercritical emulsions extraction (SEE-C) process uses a countercurrent packed tower for the continuous extraction of the organic solvents from emulsions. The continuous operation allows the formation of microspheres that are recovered at the bottom of the tower in the form of a water suspension, avoiding coalescence problems and batch-to-batch repeatability, typical of traditional processes. In this work, the packed tower used for SEE-C was characterized from a fluidodynamic point of view: flooding conditions and the allowable density difference were calculated from the experimental data. Then, an active principle (insulin) was tested for its encapsulation in poly(lactic-co-glycolic acid) (PLGA) microspheres, starting from a double emulsion: particle size, morphology, and encapsulation efficiency of the produced microdevices were evaluated. Spherical, not collapsed microspheres with a mean diameter between 1.8 mu m (SD +/- 0.9) and 4.8 mu m (SD +/- 2.8) and encapsulation efficiencies up to 70% were obtained. The very fast solvent extraction rate did not influence the particle morphology but had a significant effect on the size distribution of the precipitates which were always smaller than the starting droplets. A solvent residue (ethyl acetate) lower than about 600 ppm was obtained in all the experiments performed.