Droplet-based Microfluidics for Making Uniform-sized Cellular Spheroids in Alginate Beads with the Regulation of Encapsulated Cell Number

Droplet-based microfluidic devices are a promising strategy for generating highly-reproducible, massive cellular spheroids. However, there were challenges in the previously-reported microencapsulation device for forming uniformly-sized cellular spheroids because of difficulty in regulating the number of encapsulated cells in the alginate beads. Here, I introduce an advanced droplet-based microfluidic device that is capable of generating the number of encapsulated cells in a more uniform fashion than the previously-reported microencapsulation device via dispersing cell clusters formed by self-assembly into an individual single cell at a cell-scattering component. When cell clusters were introduced in the cell scattering component, the initial large-sized cell clusters were scattered into single cells via about 10 iterations of sequential processes (split, stretch, and bump). After cell encapsulation, the number of encapsulated cells coincided with the Poisson distribution in the cell-scattering encapsulation device, while the number of encapsulated cells was rather randomized in the previous device; the cell clusters were encapsulated in 20% of all alginate beads. In addition, more uniform-sized cellular spheroids were generated in the beads by the cell-scattering encapsulation than by the previously-reported device via adjusting the number of cells in the beads. The proposed method provides a valuable tool for generating massive and uniform cellular spheroids, which will contribute to the development of a new quantitative analysis of stem cell differentiation and cancer research.