I was wondering on why my cells (3T3 and airway smooth muscles) did not attach on my gelatin methacrylate hydrogels. When I encapsulated 3T3 fibroblasts, they proliferated and seem to have protrusions after 4 days of cukture, which I suppose is a differentiated phenotype state of it. However, when I seeded them on top of the crosslinked hydrogel, I do not see cells that attach on the gels. I used 5 and 10% GelMA w/ 0.5% I2959 at DMEM, irradiated them for 5 mins, incubated and sterilized with DMEM with 2% AB/AM for 24 h, and then seeded the cells on top with DMEM containing 10% FBS, 1% Antibiotic/Antimycotic stock soln and 1% L-glutamine. Cell density is 30,000/well on a 24 well plate (seeded at 500 uL volume); hydrogel dimensions are: Diameter- 12mm, thickness-3 mm. Degree of substitution of GelMA - 95%, pore size = 30-50 um.