Biodegradation of Silk Rods Using Protease XIV

Protease XIV (EC 3.4.24.31, Sigma-Aldrich, Shanghai, China) was used for biodegradation studies as it has been shown to be effective in the digestion of casein as compared to trypsin, chymotrypsin and several other proteases [26 (link)]. Silk rods were incubated in a shaker at 37 °C in a solution of Protease XIV (20 ± 1 mg, pH = 7.4, 3.5 U/mg) and PBS for 28 days. Each specimen contains an approximately equivalent dry mass (1.00 ± 0.02 g) of silk-based rods and each specimen has five replicates. During the degradation, the enzymatic aqueous solutions were replenished weekly. The samples were harvested at different time points followed by rinsing with distilled water 3 times. The residual mass was dried at 60 °C for 24 h to determine the degradation ratio of silk rods.