Cell viability of 3D GelMA hydrogels encapsulating OD21 cells after exposure to DL and UV and cultured in vitro for 1, 3 and 5 days. Cell viability increased after 5 days in vitro culture (A). Representative uorescent images of OD21 cells stained for live (blue) and dead (green) cells on day 5 (DL images B to E, UV images F to H). UV 5s did not polymerize. p<0.05 (*), p<0.01(**), p<0.001(***), p<0.0001(****).