Surface Functionalization of Orthopedic Titanium Implants with Bone Sialoprotein

• Published in: PloS one 2016-04, Vol.11 (4), p.e0153978-e0153978
• Main Authors: Baranowski, Andreas, Klein, Anja, Ritz, Ulrike, Ackermann, Angelika, Anthonissen, Joris, Kaufmann, Kerstin B, Brendel, Christian, Götz, Hermann, Rommens, Pol M, Hofmann, Alexander
• Format: Article
• Language: English
• Subjects: Adhesion; Alkaline phosphatase; Analysis; Animal models; Biocompatibility; Biology and Life Sciences; Biomedical materials; Bone growth; Bone implants; Bone marrow; Bone sialoprotein; Bone surgery; Bone turnover; Calcification; Calcium; Cbfa-1 protein; Cell adhesion; Cell adhesion & migration; Cell culture; Cell differentiation; Cell migration; Coating effects; Collagen; Composite materials; Coupling; Covalence; Deposition; Disks; Engineering and Technology; Femur; Fibroblasts; Gene expression; Genetic aspects; Hydrogels; Hydroxyapatite; Integrin-Binding Sialoprotein - chemistry; Loosening; Medicine and Health Sciences; Mineralization; Morphology; Nanocomposites; Nanoparticles; Orthopedics; Osseointegration; Osteoblasts; Osteogenesis; Physical Sciences; Physiological aspects; Properties; Prostheses and Implants; Proteins; Ribonucleic acid; RNA; Stability; Surface Properties; Surgical implants; Tissue engineering; Titanium; Transcription factors; Transplants & implants
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0153978

Orthopedic implant failure due to aseptic loosening and mechanical instability remains a major problem in total joint replacement. Improving osseointegration at the bone-implant interface may reduce micromotion and loosening. Bone sialoprotein (BSP) has been shown to enhance bone formation when coated onto titanium femoral implants and in rat calvarial defect models. However, the most appropriate method of BSP coating, the necessary level of BSP coating, and the effect of BSP coating on cell behavior remain largely unknown. In this study, BSP was covalently coupled to titanium surfaces via an aminosilane linker (APTES), and its properties were compared to BSP applied to titanium via physisorption and untreated titanium. Cell functions were examined using primary human osteoblasts (hOBs) and L929 mouse fibroblasts. Gene expression of specific bone turnover markers at the RNA level was detected at different intervals. Cell adhesion to titanium surfaces treated with BSP via physisorption was not significantly different from that of untreated titanium at any time point, whereas BSP application via covalent coupling caused reduced cell adhesion during the first few hours in culture. Cell migration was increased on titanium disks that were treated with higher concentrations of BSP solution, independent of the coating method. During the early phases of hOB proliferation, a suppressive effect of BSP was observed independent of its concentration, particularly when BSP was applied to the titanium surface via physisorption. Although alkaline phosphatase activity was reduced in the BSP-coated titanium groups after 4 days in culture, increased calcium deposition was observed after 21 days. In particular, the gene expression level of RUNX2 was upregulated by BSP. The increase in calcium deposition and the stimulation of cell differentiation induced by BSP highlight its potential as a surface modifier that could enhance the osseointegration of orthopedic implants. Both physisorption and covalent coupling of BSP are similarly effective, feasible methods, although a higher BSP concentration is recommended.