Effect of HF/HNO₃-treatment on the porous structure and cell penetrability of titanium (Ti) scaffold

Porous titanium (Ti) implants have been used in orthopedic and dental applications because of their superior mechanical properties. Sufficient pore interconnectivity is required for effective bone regeneration and growth inside the Ti scaffold pore structure. We proposed post-treatment with HF/HNO₃ to efficiently modify the internal pore structure of a Ti scaffold and achieve controllable mechanical properties with a pore neck structure. The porosity, pore size, wall thickness, and pore neck size were easily controlled by varying the acid treatment time, which produced a Ti scaffold with mechanical properties that were suitable for bone tissue engineering. As the mixed acid treatment time increased, internal isolated pores were gradually interconnected with adjacent pores. After 10 min of treatment, nearly all the pores were interconnected. The post-treatment with HF/HNO₃ also affected the surface properties. Surface carbon contaminants were significantly reduced after treatment with no hydride formation. Micron-scale surface roughness was uniformly generated across the whole surface. The actual cell penetrability of the Ti scaffold was evaluated using a perfusion-based in vitro cell test. Over 90% of the surface pores depict cell penetrability with a sufficient number of cells attached to the wall surface of the pore after performing acid treatment for 12 min.