In vitro release behavior of BSA from composite hydrogel. A: release behavior of S1, S3, an S6 hydrogel with the same hydrogel concentration (30 wt%) and initial drug loading amount (4 mg). B: release behavior of 30 wt% S4 hydrogel with different initial drug loading amount (4 mg and 8 mg). C: release behavior of 4 mg BSA loaded S4 hydrogel with different hydrogel concentration (20 wt% and 30 wt%). D: SDS-PAGE results of BSA in vitro release profile; Lane 1: marker; Lane 2: BSA standard; Lane 3: S1 at 24th hour; Lane 4: S1 at 168th hour; Lane 5: S1 at 360th hour; Lane 6: S3 at 24th hour; Lane 7: S3 at 168th hour; Lane 8: S3 at 360th hour; Lane 6: S3 at 12th hour; Lane 10: S3 at 48th hour. Error bars represent the standard deviation (n = 3).