Antibacterial metal ion release from diamond-like carbon modified surfaces for novel multifunctional implant materials
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Achim Wixforth and Christoph Westerhausena) Chair for Experimental Physics 1, University of Augsburg, Augsburg 86159, Germany; Nanosystems Initiative Munich, Munich 80799, Germany; and Augsburg Center for Innovative Technologies (ACIT), Augsburg 86159, Germany (Received 12 January 2016; accepted 13 July 2016)
The aim of this study was the synthesis of hard and low-abrasive novel implant materials with builtin time-dependent antibacterial properties, which can be tailored by a well-defined time-dependent and finite release of metal ions. We were able to synthesize such smart implant surfaces employing ECR (electron cyclotron resonance)-plasma on typical titanium implant material by transforming a polymer film into diamond-like carbon (DLC) which contains metal nanoparticles as reservoirs for controlled metal ion release. We found that the amount of released antibacterial metal ions is a biexponential function of time with a high release rate during the first few hours followed by a decreased ion release rate within the following days. To describe our experimental findings, we developed a kinetic model assuming that both nanoparticles near the surface and nanoparticles in the DLC bulk contribute to the total amount of ions released with different time constants.
I. INTRODUCTION
Despite many efforts in the field of clinical hygiene research, healthcare-associated infections are still a serious problem and frequently lead to revision surgeries. According to recent studies, joint replacements require still almost 7% revision, and infections due to surfaces harboring bacteria, such as gram positive Staphylococci,1 are amongst the most prominent post-operative incidents.1,2 As the aging population and hence the need for implants grows in Western countries, this serious problem will presumably even increase in the future. Novel and innovative scientific approaches thus, amongst others, aim toward an appropriate biofunctionalization of implant surfaces. Especially for articulated joint surfaces, the most important demands are biocompatibility, timedependent antibacterial activity, and profound corrosion as well as wear resistance. In terms of antibacterial performance, modern implant surfaces should ideally provide a tailored antibacterial behavior with a large initial antibacterial activity during the first 24 h after implantation. This way, implant-associated infections could be avoided and the implant surface would be protected against bacterial adhesion and subsequent biofilm formation.3,4 The initial fast action should be followed by a continuously decreasing antibacterial activity within the subsequent few days. Contributing Editor: Mauricio Terrones a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.275
To create such intelligent implant surfaces with optimized hardness, wear and corrosion resistance and at the same time exhibiting the desired antibacterial properties, we used an energetic ion treatment of a functionalized polymeric surface layer. This polymer layer
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