*2.3. Characterization of Ti, Hepa/Ti, PDGF/Hepa/Ti, BMP/Hepa/Ti, and PDGF/BMP/Hepa/Ti Substrates*

#### 2.3.1. Scanning Electron Microscope (SEM) Image

The surfaces of Ti, Hepa/Ti, PDGF/Hepa/Ti, BMP/Hepa/Ti, and PDGF/BMP/Hepa/Ti disc were observed by scanning electron microscopy (SEM; S-2300, Hitachi, Tokyo, Japan). Samples were coated with gold using a sputter coater (Eiko IB, Eiko Engineering, Tokyo, Japan) and SEM was performed at 3 kV.
