Synergistic effects of lanthanum and strontium to enhance the osteogenic activity of TiO2 nanotube biological interface

Abstract According to the clinician's experience, the main reason for the inefficiency of osseointegration between biometal and surrounding bone tissue is still caused by the biological inertness on the surface. Due to the osteogenic effects of its titanium dioxide nanotubes (TiO2) and strontium ions, strontium-containing TiO2 nanotube (STN) coatings have been widely used for titanium surface modification. Trace amounts of rare earth elements (such as lanthanum (La)) show some potential in the performance of repairing bone tissue. In this study, in order to shorten the osseointegration time of titanium implants, we first introduced lanthanum into the biological interface of SrTiO3 nanotubes (LSTN) to achieve the best osteogenesis effect. The AFM, SEM, EDS, FTIR, XPS analyses revealed that the nanocomposite structure of the LSTN was successfully fabricated. LSTN exhibits excellent hydrophilicity and protein adsorption capacity, which are essential for the adhesion of pre-osteoblasts to the surface of nanotubes. LSTN did not show any cytotoxicity in pro-osteoblast proliferation and differentiation experiments. Just the opposite, the cells stretched well on the surface of the LSTN, showing a large number of stress fibers and actin filaments. Furthermore, compared with La-free nanotubes, LSTN showed the potential to excellently up-regulate the expression of osteoblast-related genes such as OCN, ALP, Col-1, and RUNX2. Our results show that LSTN exhibits excellent osteogenic potential due to the osteogenic effect of lanthanum and strontium and the protein adsorption capacity of nanotubes, which provides the possibility for accelerating bone healing in patients with bone damage.