Enhanced osteogenic differentiation of MC3T3-E1 on rhBMP-2 immobilized titanium surface through polymer-mediated electrostatic interaction

Titanium and its alloy are widely used in osteointegration. However, osteogenic activity requires enhancements in order to meet clinical needs. To enhance the osteogenic activity of titanium, human recombined bone morphogenetic protein 2 (rhBMP-2) was immobilized on a titanium surface through self-assembly driven by electrostatic interaction. Pure titanium foil (10 mm in diameter and 0.3 mm thickness) was coated with gold nanoparticles (TA) by magnetron sputtering, and then the gold dots were decorated with negatively charged polymer (TA/BPP) in order to generate positively charged rhBMP-2 complex (TA/BPP/BMP-2) on the surface. The surface characteristics and the bioactivity and osteogenic activity of the surface-modified titanium were detected. The results showed that rhBMP-2 was successfully complexed on the titanium surfaces. The zeta potential of TA surfaces decreased after contacting with BPP solutions but rebounded after rhBMP-2 coating. The loading efficiency of rhBMP-2 reached 83.4% +/- 2.02%, and the amount of rhBMP-2 released at physiological pH conditions was minimum and increased at extreme acidic conditions. The osteogenic capability was significantly elevated when MC3T3-E1 cells were cultured on TA/BPP/BMP-2 rather than other surfaces. In conclusion, rhBMP-2 can be successfully immobilized on titanium surfaces by electrostatic adsorption using negative polymer, which results in enhanced bioactivity, osteogenic capability in vitro.