A novel single-step fabrication technique to create heterogeneous poly(ethylene glycol) hydrogel microstructures containing multiple phenotypes of mammalian cells.

In this study, a novel method for the one-step fabrication of stacked hydrogel microstructures using a microfluidic mold is presented. The fabrication of these structures takes advantage of the laminar flow regime in microfluidic devices, limiting the mixing of polymer precursor solutions. To create multilayered hydrogel structures, microfluidic devices were rotated 90 degrees from the traditional xy axes and sealed with a cover slip. Two discreet fluidic regions form in the channels, resulting in the multilayered hydrogel upon UV polymerization. Multilayered patterned poly(ethylene glycol) hydrogel arrays (60 mum tall, 250 mum wide) containing fluorescent dyes, fluorescein isothiocyanate, and tetramethylrhodamine isothiocyanate were created for imaging purposes. Additionally, this method was used to generate hydrogel layers containing murine fibroblasts and macrophages. The cell adhesion promoter, RGD, was added to hydrogel precursor solution to enhance fibroblast cell spreading within the hydrogel matrix in one layer, but not the other. We were able to successfully generate patterns of hydrogels containing multiple phenotypes by using this technique.