3.2. Physical and mechanical properties of DP
The surface topographies of collagen, NP, and DP scaffolds were visualized by SEM and AFM (Figure 2A&B). As shown in the SEM images, NP had a relatively smooth surface, while COL and DP displayed uneven and porous surfaces with abundant collagen fibers randomly arranged in a network pattern. Masson trichrome staining revealed the collagen fiber structure in each group (Figure 2C). The structure and distribution of collagen did not differ significantly between DP and NP. Picrosirius red examination also showed that the arrangement and structure of collagen in DP was similar to that in NP (Figure 2D). Immunohistochemical staining of collagen I demonstrated the arrangement of type I collagen in each group (Figure 2E), and Safranin O staining showed the presence of identifiable GAGs in DP scaffolds after decellularization (Figure 2F). The surface hydrophilicity of each scaffold material was analyzed by water contact angle measurement as shown in Figure 2G. Both the NP and DP scaffolds showed good hydrophilicity. Analysis of the mechanical properties of each scaffold type showed no significant difference in yield stress among the groups, but that the DP scaffolds exhibited a moderate elastic modulus (Figure 2H).