2.3 Characterization of DP
The surface morphology of DP scaffolds was analyzed by scanning electron microscopy (SEM; Model: JSM-6700F, JEOL, Japan) and atomic force microscopy (AFM; Model: Multimode & Dimension 3100, Varian, USA). Additionally, the scaffolds were stained with Picrosirius Red (Solarbio, China) and viewed under a polarizing microscopy (Leica, Germany) for observation of the collagen structure. DP samples were also histologically examined using Masson trichrome staining and safranin-O/fast green staining. Immunohistochemical analysis was performed using antibody against type I collagen (dilution: 1:200, Abcam, USA). The surface hydrophilicity was evaluated by measuring the water contact angle with a contact angle goniometer (Dataphysics OCA 35, Germany) using the sessile drop method. The mechanical properties of the DP scaffolds were tested using a universal testing machine (Model: AG-IC 50KN, SHIMADZU, Japan). Dumbbell-shaped samples measuring 4 mm × 50 mm were prepared for mechanical testing, and the crosshead speed was set at 15 mm/min with a load capacity of 50 N. The yield stress, failure strain, and modulus data were obtained.