2.7 Swelling ratio and residual mass test
GelMA samples with different crosslinking times were weighed as (Wo) and gently shaken in DPBS and DI water at 37 ℃ for two days to remove the uncrosslinked GelMA. The swelling mass was recorded as (Ws) and the expanded samples were lyophilized to obtain the mass (Wr).
Swelling ratio=(Ws-Wr)/Wr×100 %
Residual ratio=Wr/(Wo×5%) ×100%