Surface Immobilization of TiO2 Nanotubes with Bone Morphogenetic Protein-2 Synergistically Enhances Initial Preosteoblast Adhesion and Osseointegration.

Ying Li,Yunjia Song,Changyi Li,Aobo Ma

doi:10.1155/2019/5697250

Abstract

Although titanium (Ti) alloys have been widely used as implant materials, the bioinertness of pristine Ti impairs their bioactivity and early osseointegration. In the present work, we prepared TiO2 nanotubes (TNT) layer on the titanium (Ti) surface by anodic oxidation. The anodized surface was functionalized with human bone morphogenetic protein-2 coating to form the hBMP-2/TNT surface. The release behavior of hBMP-2 on the hBMP-2/TNT surface displayed a controlled and sustained pattern, compared to that on the hBMP-2/Ti surface, which showed a rapid release. In vitro cellular activity tests demonstrated that both TNT and hBMP-2/Ti surfaces, particularly the hBMP-2/TNT surface, enhanced adhesion, proliferation, and differentiation of osteoblast cells. Increased cell adhesion, improved cytoskeleton organization, and immunofluorescence staining of vinculin were observed on the modified surfaces. The TNT, hBMP-2/Ti, and hBMP-2/TNT surfaces, especially the hBMP-2/TNT surface, further displayed an upregulated gene expression of adhesion and osteogenic markers vinculin, collagen type 1, osteopontin, and osteocalcin, compared to the pristine Ti surface. In vivo experiments using a rat model demonstrated that the TNT and hBMP-2/Ti surfaces, in particular the hBMP-2/TNT surface, improved osseointegration and showed a superior bone bonding ability compared to Ti. Our study revealed a synergistic role played by TiO2 nanotubes nanotopography and hBMP-2 in promoting initial osteoblast adhesion, proliferation, differentiation, and osseointegration, thus suggesting a promising method for better modifying the implant surface.

Highlights

Titanium (Ti) and its alloys are commonly used as dental and orthopedic implant materials because of their good biocompatibility, appropriate mechanical properties, and corrosion resistance [1, 2]
The human bone morphogenetic protein2 (hBMP-2) proteins loosely dispersed on the hBMP-2/Ti surface (Figure 1(d)), whereas the proteins compactly immobilized on the hBMP-2/TiO2 nanotubes (TNT) substrate, covering most of the nanotube openings, suggesting higher loading ability for the latter substrate (Figure 1(e))
The hBMP-2/TNT surface showed higher gene expression levels than the other surfaces after cultured for 7 days (p

Summary

Introduction

Titanium (Ti) and its alloys are commonly used as dental and orthopedic implant materials because of their good biocompatibility, appropriate mechanical properties, and corrosion resistance [1, 2]. Since the bioinertness of Ti hinders its cell/material interaction and early osseointegration [5], development of modified surfaces to improve the biocompatibility of Ti implant materials is of great value. Many efforts have been applied to alter the surface topography, hydrophilicity, and biological properties of Ti implant surfaces [6,7,8]. Among these techniques, anodic oxidation (AO) method has attracted much attention. The ordered and controllable TiO2 nanotube surface produced by anodization has been reported to effectively promote osteoblast cell adhesion, proliferation, and differentiation in vitro [11,12,13,14]. Several studies indicated that TiO2 nanotube layer could enhance osseointegration in vivo [15, 16]

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Discussion

Conclusion