The production of protein-loaded microparticles by supercritical fluid enhanced mixing and spraying

In this study, we use supercritical carbon dioxide as a processing medium for the fabrication of poly(dl-lactic acid) P(DLLA) microparticles that encapsulate a protein material. We have previously demonstrated that this polymer and a dry powder of a protein can be mixed under supercritical carbon dioxide conditions (above 31.1 °C and 73.8 bar) and that the protein component retains its biological activity. In this paper, we progress the work to demonstrate that the plasticized polymer and dry powder protein mixture can be sprayed to form solid polymer particles that encapsulate the protein. Particle size range is between 10 and 300 μm after spraying. Ribonuclease A and lysozyme were encapsulated in the polymer without significant loss of enzymatic activity. Biological assays of insulin and calcitonin confirm retention of activity after fabrication of the microparticles and release of the peptides/proteins.