Morphology control of protein microparticles produced using microfluidic droplets in a non-equilibrium state

Here we present microfluidic systems to produce micrometer-sized particles made of proteins, using monodisperse droplets in a non-equilibrium state. Droplets of an aqueous solution of protein were formed in the continuous phase of a water-dissolving polar organic solvent, and then the droplets were shrunk because of the dissolution of water molecules. Protein molecules were precipitated, and then stable protein microparticles were obtained after the crosslinking reaction. We obtained spherical/non-spherical protein microparticles using several types of proteins, and examined factors affecting the particle morphology. In particular, highly unique tear-drop-shaped particles and hemispherical particles were obtained when incompletely dehydrated droplets were crosslinked. In addition, we cultured mammalian cells on the particles made of collagen, demonstrating the applicability of the particles as cell-culture scaffolds. The presented protein microparticles would be useful as carriers or scaffolds for various biological/medical applications.