Electrochemical Surface Treatment of a β-titanium Alloy to Realize an Antibacterial Property and Bioactivity

Takao Hanawa,Mitsuo Niinomi,Masaya Shimabukuro,Yusuke Tsutsumi,Masaaki Nakai,Hisashi Doi,Peng Chen,Maki Ashida

doi:10.3390/met6040076

Takao Hanawa, Mitsuo Niinomi + Show 6 more

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https://doi.org/10.3390/met6040076

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Abstract

In this study, micro-arc oxidation (MAO) was performed on a β-type titanium alloy, namely, Ti-29Nb-13Ta-4.6Zr alloy (TNTZ), to improve not only its antibacterial property but also bioactivity in body fluids. The surface oxide layer formed on TNTZ by MAO treatment in a mixture of calcium glycerophosphate, calcium acetate, and silver nitrate was characterized using surface analyses. The resulting porous oxide layer was mainly composed of titanium oxide, and it also contained calcium, phosphorus, and a small amount of silver, all of which were incorporated from the electrolyte during the treatment. The MAO-treated TNTZ showed a strong inhibition effect on anaerobic Gram-negative bacteria when the electrolyte contained more than 0.5 mM silver ions. The formation of calcium phosphate on the surface of the specimens after immersion in Hanks’ solution was evaluated to determine the bioactivity of TNTZ with sufficient antibacterial property. As a result, thick calcium phosphate layers formed on the TNTZ specimen that underwent MAO treatment, whereas no precipitate was observed on TNTZ without treatment. Thus, the MAO treatment of titanium-based alloys is confirmed to be effective in realizing both antibacterial and bioactive properties.

Highlights

Titanium (Ti) and Ti alloys are widely used in both the orthopedic and dental fields because of their good mechanical properties, high corrosion resistance, and biocompatibility
We found that the component elements such as calcium (Ca) and phosphorus (P) in the electrolyte were incorporated into the resultant porous oxide layer by micro-arc oxidation (MAO) treatment [13,14]
Treatment shows the images of TNTZ before and after MAO treatment

Summary

Introduction

Titanium (Ti) and Ti alloys are widely used in both the orthopedic and dental fields because of their good mechanical properties, high corrosion resistance, and biocompatibility. A β-type Ti alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ), which is composed of non-toxic and non-allergenic elements, has been developed It has a high potential for use in biomedical applications because of its excellent mechanical properties and low cytotoxicity along with a low Young’s modulus [1,2]. One of the most used methods is micro-arc oxidation (MAO), sometimes called plasma electrolytic oxidation (PEO), and it is known as a useful surface treatment based on electrochemical reactions under high voltage in a specific electrolyte Both in vitro [4] and in vivo [5] evaluations have revealed that MAO treatment improves the hard-tissue compatibility of Ti. MAO treatment is suitable for valve metals because a porous oxide layer is achieved by the competing growth and breakdown of the oxide with a high-electric resistance layer under high voltage.

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