Continuous supercritical emulsions extraction: a new technology for biopolymer microparticles production

Supercritical emulsion extraction (SEE) was recently proposed for the production of biopolymer microparticles starting from oil-in-water emulsions. This technology can improve the product quality because of the fast and selective extraction of the dispersed oily phase by using supercritical carbon dioxide (SC-CO(2) ). However, until now, SEE was proposed in batch configuration, sharing with the traditional processes an intrinsically discontinuous operation and problems of batches reproducibility and process yield. In this study, by using a countercurrent packed column, the SEE process was proposed in a continuous operating mode (SEE-CM) for the production of poly-lactic-co-glycolic acid (PLGA) microparticles. The new process design takes advantage of the large contact area between the SC-CO(2) and emulsion allowing the production of PLGA microparticles with controlled and narrow size distributions in only few minutes. SEE-CM operating parameters such as pressure, temperature, and flow rate ratios were analyzed and the process efficiency in terms of recovered material and its size distribution compared with SEE (batch mode operation) and conventional evaporation technology. PLGA microparticles showed a mean particle size between 1-3 µm (depending on the droplet sizes) with a SD that was always smaller than that associated with particles produced by discontinuous processes. Single and double emulsions were successfully treated and the microparticles physico-chemical properties showed no morphological and structural differences between the SEE-CM-produced microparticles and the ones obtained by conventional evaporation technology.