A droplet-based microfluidic process to produce yarn-ball-shaped hydrogel microbeads

A simple microfluidic process for producing yarn-ball-shaped hydrogel microbeads was devised. The mechanism employed parallel flows of aqueous solutions of a hydrogel precursor, a gelation agent, and a buffer to generate incompletely gelled alginate hydrogel microfibers. Water-in-oil droplets were generated simultaneously to fragment the fibers and fold the fragments into a yarn-ball-like shape. Alginate beads with an average outer diameter of similar to 200 mu m and fiber width of 10-30 mu m were fabricated, which had a relatively large void volume and a high surface-to-volume ratio, enabling the efficient transport of molecules in and out of the hydrogel matrix. It was found that the concentration of the gelation agent was critical for obtaining the yarn-ball-shaped beads. In addition, to test the feasibility of the beads for use in bioencapsulation, mammalian cells were encapsulated within the hydrogel matrices of the beads at high densities, and the proliferation ability of the cells was investigated by changing the precursor concentration. The fabricated hydrogel beads should be useful as a new material for bioimmobilization and bioencapsulation and could find applications in cell transplantation therapies.