Opening new operating windows for polymer and protein micronisation using the PCA process

To avoid the existing limitations of the PCA process for the precipitation of proteins and polar polymers a new approach based on the use of water to modify the phase behaviour of the system DMSO–CO2 was developed. The addition of water to the DMSO displaces the mixture critical pressure of the solution–CO2 system to higher pressures and produces a new operating region in which the PCA process can be carried out. Following this approach, it was possible to develop a process to produce 1–10 μm particles of N-trimethylchitosan chloride (TMC) suitable for inhalation. Encapsulation of proteins in TMC using this technique could also be successfully achieved.