Figure 2. Proteolysis assay of silk fibroin.
(a) Proteolysis of silk fibroin by MMP-2. MMP-2 degraded silk fibroin in a dose-dependent manner. Proteolysis of silk fibroin was completely blocked by an MMP-2 inhibitor (1: No enzyme, 2: 0.05 nM MMP-2, 3: 0.1 nM MMP-2, 4: 0.5 nM MMP-2, 5: 1 nM MMP-2, 6: 2 nM MMP-2, 7: 3 nM MMP-2, 8: 3 nM MMP-2 + 100 nM MMP-2 inhibitor). (b) Proteolysis of silk fibroin by MMP-3. MMP-3 degraded silk fibroin in a dose-dependent manner (1: No enzyme, 2: 0.25 nM of MMP-3, 3: 0.5 nM of MMP-3, 4: 0.75 nM of MMP-3, 5: 1 nM of MMP-3, 6: 2 nM of MMP-3, 7: 5 nM of MMP-3). (c) Proteolysis of silk fibroin by MMP-9. MMP-9 degraded silk fibroin in a dose-dependent manner (1: No enzyme, 2: 1 nM of MMP-3, 3: 2 nM of MMP-3, 4: 3 nM of MMP-3, 5: 4 nM of MMP-3, 6: 5 nM of MMP-3, 7: 10 nM of MMP-3). (d) The relationship between the applied enzyme concentration and the residual amount of protein. With increasing enzyme concentrations, the amount of residual protein decreased. The dotted line was drawn based on regression analysis.