(a) Schematic representation of the microfluidic design used in this study, with magnification of the array docking sites. (b) Interferometry imaging of the 2-layer fabricated master. (c) Droplet generation, with MCF7 cells labeled with CFSE (green) and CCD1129SK human mammary fibroblasts labeled with CMAC (blue). Upper pannel: 5X magnification, after droplet formation; lower pannel: 20X maginification, after hydrogel crosslinking and oil removal. In the lower panel, the edges of the hydrogel are highlighted in white in the bright field and the merged images. (d) Study workflow. Scaffolds were generated by mixing the cells in a partially cross-linked alginate, and infused into the device for droplet generation and final cross-linking. The scaffolds were then maintained by constant media perfusion, analyzed for viablity, Doxorubicin cytotoxicty, immunofluorescence, and finally collected and sorted for LC-MS proteomic profiling.Scale bar in ((b), and (c),(d) upper panels is 200 μm; scale bar in (c), (d) lower panels is 50 μm.