Alternative Techniques for Porous Microparticle Production: Electrospraying, Microfluidics, and Supercritical CO₂

Microparticles have been established as injectable drug carriers designed to enable a long-term release of the encapsulated active pharmaceutical ingredients (API). To regulate this release, the diffusion barrier provided by the matrix material - typically hydrolytically degradable polyesters - must be controlled through precise levels of matrix porosity. This mini-review presents processing methods that are alternatives to the most common batch emulsification techniques for the manufacturing of porous polymer particles. A focus is placed on mechanistically describing the particle and pore formation in droplet-based microfluidics, electrospraying, and by supercritical fluids, critically discussing their opportunities and challenges. Ultimately, this review assesses the potential of these techniques in advancing the engineering of porous polymeric carrier systems in the light of scale-up and continuous production.