Three-dimensional photopatterning of hydrogels using stereolithography for long-term cell encapsulation

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 10000 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.