*2.2. Surface Modification of Titanium (Ti) with Heparin-Dopamine (Hepa-DOPA) and rhPDGF-BB and/or rhBMP-2*

In order to immobilize rhPDGF-BB and/or rhBMP-2, Ti surfaces were modified with heparin-dopamine (Hepa-DOPA). Ti discs were placed in 10 mL Tris·HCl buffer (pH 8.0, 10 mM) containing 2 mg/mL Hepa-DOPA in the darkroom for 24 h. The Hepa-DOPA modified Ti disc was rinsed with distilled water (DW) and dried under nitrogen. Hepa-DOPA modified Ti is hereafter referred to as Heparinized-Ti (Hepa/Ti). To immobilize both rhPDGF-BB and rhBMP-2 on the surface of Hepa/Ti, a Hepa/Ti disc was immersed in MES buffer solution (pH 5.6, 0.1 M), and then rhPDGF-BB (50 ng/mL) and rhBMP-2 (50 ng/mL) were added. The reaction was allowed to proceed for 24 h at room temperature (RT), and then the disc was rinsed with DW and dried. rhPDGF-BB and rhBMP-2 immobilized on Hepa/Ti disc are hereafter referred to as PDGF/BMP/Hepa/Ti disc. rhPDGF-BB (100 ng/mL) or rhBMP-2 (100 ng/mL) modified Hepa/Ti disc were also fabricated using the same method. rhPDGF-BB or rhBMP-2 immobilized on Hepa/Ti disc are hereafter referred to as PDGF/Hepa/Ti or BMP/Hepa/Ti disc, respectively.
