**5. Conclusions**

Anodized Ti surfaces were successfully functionalized by surface grafting heparin and subsequently immobilizing rhBMP-2 and/or rhPDGF-BB. rhBMP-2 immobilized, heparin-grafted Ti implants were found to provide a suitable delivery system that enhanced osseointegration and bone regeneration in defect areas around implants. However, the study failed to reveal any synergetic effect resulting from the co-immobilization of rhBMP-2 and rhPDGF-BB.

**Acknowledgments:** This study was supported by a National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2017R1A2B4005820).

**Author Contributions:** Jung-Bo Huh conceived and designed the experiments; So-Hyoun Lee, Eun-Bin Bae, Sung-Eun Kim, Young-Pil Yun, Hak-Jun Kim, Jae-Won Choi and Jin-Ju Lee performed the experiments; So-Hyoun Lee, Sung-Eun Kim, Young-Pil Yun, Hak-Jun Kim and Jung-Bo Huh analyzed the data; So-Hyoun Lee, Eun-Bin Bae, and Jung-Bo Huh wrote the paper.

**Conflicts of Interest:** The authors have no conflict of interest to declare.
