Investigation of the Long-Term Antibacterial Properties of Titanium by Two-Step Micro-Arc Oxidation Treatment

Takao Hanawa,Kunio Ishikawa,Peng Chen,Maki Ashida,Masaya Shimabukuro,Hideki Katayama,Tomoyo Manaka,Harumi Tsutsumi,Yusuke Tsutsumi

doi:10.3390/coatings11070798

Abstract

Recently, biofilm formation caused by bacterial adhesion and colonization has been recognized as the major cause of failure in orthopedic and dental implant surgeries. In this study, a customized micro-arc oxidation (MAO) treatment technique was developed to obtain desirable antibacterial properties on Ti surfaces. The two-step MAO treatment was applied in the fabrication of specimens with Ag and with/without Zn in their surface oxide layer. In order to simulate practical usage, surface analyses and immersion tests were performed to evaluate the incorporation of Ag and Zn into the resulting oxide layer and ion release behavior, respectively. Additionally, the antibacterial properties of the specimens after long-term immersion in physiological saline were evaluated using Gram-negative facultative anaerobic bacteria. The MAO-treated specimens containing Ag and Zn exhibited excellent antibacterial properties against Escherichia coli, which were sustained even after 6 months of immersion in physiological saline to simulate practical usage. Moreover, the Ag ions released from the surface oxide indicate the antibacterial properties of the specimen in the early stage, while the release of the corrosion products of Zn demonstrates its antibacterial properties in the later stage.

Highlights

Ti and its alloys are widely used in medical fields, such as orthopedics and dentistry, due to their excellent mechanical properties and biocompatibility
We reported the effectivity of Ag and Zn in inhibiting the proliferation of Escherichia coli (E. coli) and/or Staphylococcus aureus (S. aureus), respectively [29,30,31,32]
After pouring the electrolyte into the electrochemical cell, the electrodes were connected to a direct current (DC) power supply (PL-650-0.1, Matsusada Precision Inc., Shiga, Japan), and a positive voltage with a constant current density of 251 Am−2 was applied for 10 min

Summary

Introduction

Ti and its alloys are widely used in medical fields, such as orthopedics and dentistry, due to their excellent mechanical properties and biocompatibility. In recent years, the major cause of failure in orthopedic and dental implant surgeries has been determined to be biofilm formation due to bacterial adhesion and subsequent colonization on biomaterials [5,6,7,8,9]. The easiest strategy to prevent biofilm formation on metallic devices is polishing, as a rough surface promotes bacterial adhesion. For dental implants and orthodontic fixators in contact with bones, a rough surface is preferred to ensure hard-tissue compatibility; surface polishing is not the most effective approach for this application. Another method to prevent biofilm formation is the application of antibacterial agents. Surface modification should enable the formation of a biofunctional layer that supports Ag and Zn ions to overcome problems associated with biofilms on metallic biomaterials

Methods

Results

Conclusion