Evaluating hydrogenated nickel-titanium alloy for orthopedic implant

Nickel-titanium (NiTi) alloys are widely used in orthopedic implants for their good biocompatibility and mechanical properties. They are also applied for hydrogen storage capacity in energy application. Here we evaluated the use of NiTi alloys as carriers for delivering hydrogen molecules to wound sites, where these hydrogen molecules could be released to reduce the free radicals and inhibit the inflammatory reactions at these sites. The results of the XRD characterization, cyclic voltammetry, and thermal desorption analyses showed that the NiTi alloys used in this study could effectively carry hydrogen molecules after treating with cathodic hydrogen charging method. After hydrogen charging, the results of nano-indentation test revealed that the Young's modulus for these materials decreased from 81.45 GPa to 62.15 GPa, and its hardness decreased from 5.33 GPa to 4.50 GPa, which could help to improve the biocompatibility; and the water contact angle decreased from 75.04° to 63.83°, which is beneficial for cellular attachment. The results of the in vitro and in vivo study show that the use of hydrogen charged NiTi alloys could lead to higher cellular viability in human osteosarcoma cells (MG63), mouse fibroblasts (L929), and rat bone mesenchymal stem cells (BMSCs) and would significantly reduce inflammation.