3.1.1. Scanning Electron Microscopy (SEM)

As shown in Figure 3, the surface morphologies of Ti, Hepa/Ti, PDGF/Hepa/Ti, BMP/Hepa/Ti, and PDGF/BMP/Hepa/Ti discs were investigated using SEM. Ti modified with rhHepa-DOPA, rhPDGF-BB, rhBMP-2, or rhPDGF-BB/rhBMP-2 had surface morphologies similar to Ti alone. These results indicate that the surfaces of Ti modified by small molecules, such as, Hepa-DOPA, rhPDGF-BB, rhBMP-2, or rhPDGF-BB/rhBMP-2 cannot be differentiated by SEM.

**Figure 3.** Scanning electron microscope (SEM) images of (**a**) Ti, (**b**) Hepa/Ti, (**c**) PDGF/Hepa/Ti, (**d**) BMP/Hepa/Ti, and (**e**) PDGF/BMP/Hepa/Ti.
