Effects of hydrogenated TiO2 nanotube arrays on protein adsorption and compatibility with osteoblast-like cells

Ran Lu,1–3,* Caiyun Wang,1–3,* Xin Wang,1 Yuji Wang,3 Na Wang,1 Joshua Chou,4 Tao Li,1,2 Zhenting Zhang,1 Yunhan Ling,2 Su Chen1 1Laboratory of Biomaterials and Biomechanics, Beijing Key Laboratory of Tooth Regeneration and Function Reconstruction, School of Stomatology, Capital Medical University, 2Laboratory of Advanced Functional Materials, Department of Materials Science and Engineering, Tsinghua University, 3School of Pharmaceutical Sciences, Capital Medical University, Beijing, People’s Republic of China; 4Advanced Tissue Regeneration and Drug Delivery Group, School of Life Sciences, University of Technology Sydney, Sydney, NSW, Australia *These authors contributed equally to this work Background: Modified titanium (Ti) substrates with titanium dioxide (TiO2) nanotubes have broad usage as implant surface treatments and as drug delivery systems. Methods: To improve drug-loading capacity and accelerate bone integration with titanium, in this study, we hydrogenated anodized titanium dioxide nanotubes (TNTs) by a thermal treatment. Three groups were examined, namely: hydrogenated TNTs (H2-TNTs, test), unmodified TNTs (air-TNTs, control), and Ti substrates (Ti, control). Results: Our results showed that oxygen vacancies were present in all the nanotubes. The quantity of -OH groups greatly increased after hydrogenation. Furthermore, the protein adsorption and loading capacity of the H2-TNTs were considerably enhanced as compared with the properties of the air-TNTs (P<0.05). Additionally, time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to investigate the interactions of TNTs with proteins. During the protein-loading process, the H2-TNTs not only enabled rapid protein adsorption, but also decreased the rate of protein elution compared with that of the air-TNTs. We found that the H2-TNTs exhibited better biocompatibility than the air-TNT and Ti groups. Both cell adhesion activity and alkaline phosphatase activity were significantly improved toward MG-63 human osteoblast-like cells as compared with the control groups (P<0.05). Conclusion: We conclude that hydrogenated TNTs could greatly improve the loading capacity of bioactive molecules and MG-63 cell proliferation. Keywords: titanium, hydrogenation, nanotubes, hydrophilicity, protein elution, cyto­compatibility