As Featured In: Title: Three-dimensional Photopatterning of Hydrogels Using Stereolithography for Long-term Cell Encapsulation Three-dimensional Photopatterning of Hydrogels Using Stereolithography for Long-term Cell Encapsulation †

Mernier Electrical lysis device with dielectrophoretic cell sorting Baroud Dynamics of microo uidic droplets Adapting stereolithographic technology for long-term encapsulation of living cells in complex 3D hydrogels. The spatial distribution of cells and bioactive molecules can be controlled by repetitive deposition and processing of individual layers using computer-controlled devices. Cell-encapsulated hydrogels with complex three-dimensional (3D) structures were fabricated from photopolymerizable poly(ethylene glycol) diacrylate (PEGDA) using modified 'top-down' and 'bottoms-up' versions of a commercially available stereolithography apparatus (SLA). Swelling and mechanical properties were measured for PEGDA hydrogels with molecular weights (M w) ranging from 700 to 10 000 Daltons (Da). Long-term viability of encapsulated NIH/3T3 cells was quantitatively evaluated using an MTS assay and shown to improve over 14 days by increasing the M w of the hydrogels. Addition of adhesive RGDS peptide sequences resulted in increased cell viability, proliferation, and spreading compared to pristine PEG hydrogels of the same M w. Spatial 3D layer-by-layer cell patterning was successfully demonstrated, and the feasibility of depositing multiple cell types and material compositions into distinct layers was established.