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Nanomaterials 2017, 7(8), 229;

Two-in-One Biointerfaces—Antimicrobial and Bioactive Nanoporous Gallium Titanate Layers for Titanium Implants

Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, Aichi Prefecture 487-8501, Japan
Australian Institute for Nanoscale Science and Technology, Charles Perkins Centre, Faculty of Pharmacy, University of Sydney, Pharmacy and Bank Building A15, Sydney, NSW 2006, Australia
Department of Infectious Diseases and Immunology, Sydney Medical School, University of Sydney, Sydney, NSW 2050, Australia
Authors to whom correspondence should be addressed.
Received: 10 July 2017 / Revised: 11 August 2017 / Accepted: 12 August 2017 / Published: 20 August 2017
(This article belongs to the Special Issue Frontiers in Toxicity and Functionalization of Nanomaterials)
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The inhibitory effect of gallium (Ga) ions on bone resorption and their superior microbial activity are attractive and sought-after features for the vast majority of implantable devices, in particular for implants used for hard tissue. In our work, for the first time, Ga ions were successfully incorporated into the surface of titanium metal (Ti) by simple and cost-effective chemical and heat treatments. Ti samples were initially treated in NaOH solution to produce a nanostructured sodium hydrogen titanate layer approximately 1 μm thick. When the metal was subsequently soaked in a mixed solution of CaCl2 and GaCl3, its Na ions were replaced with Ca and Ga ions in a Ga/Ca ratio range of 0.09 to 2.33. 8.0% of the Ga ions were incorporated into the metal surface when the metal was soaked in a single solution of GaCl3 after the NaOH treatment. The metal was then heat-treated at 600 °C to form Ga-containing calcium titanate (Ga–CT) or gallium titanate (GT), anatase and rutile on its surface. The metal with Ga–CT formed bone-like apatite in a simulated body fluid (SBF) within 3 days, but released only 0.23 ppm of the Ga ions in a phosphate-buffered saline (PBS) over a period of 14 days. In contrast, Ti with GT did not form apatite in SBF, but released 2.96 ppm of Ga ions in PBS. Subsequent soaking in hot water at 80 °C dramatically enhanced apatite formation of the metal by increasing the release of Ga ions up to 3.75 ppm. The treated metal exhibited very high antibacterial activity against multidrug resistant Acinetobacter baumannii (MRAB12). Unlike other antimicrobial coating on titanium implants, Ga–CT and GT interfaces were shown to have a unique combination of antimicrobial and bioactive properties. Such dual activity is essential for the next generation of orthopaedic and dental implants. The goal of combining both functions without inducing cytotoxicity is a major advance and has far reaching translational perspectives. This unique dual-function biointerfaces will inhibit bone resorption and show antimicrobial activity through the release of Ga ions, while tight bonding to the bone will be achieved through the apatite formed on the surface. View Full-Text
Keywords: gallium ion; apatite formation; gallium titanate; Ti metal; simulated body fluid; antibacterial gallium ion; apatite formation; gallium titanate; Ti metal; simulated body fluid; antibacterial

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Yamaguchi, S.; Nath, S.; Sugawara, Y.; Divakarla, K.; Das, T.; Manos, J.; Chrzanowski, W.; Matsushita, T.; Kokubo, T. Two-in-One Biointerfaces—Antimicrobial and Bioactive Nanoporous Gallium Titanate Layers for Titanium Implants. Nanomaterials 2017, 7, 229.

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