Original Article
Long-term release of antibiotics by carbon nanotube-coated titanium alloy surfaces diminish biofilm formation by Staphylococcus epidermidis

https://doi.org/10.1016/j.nano.2017.01.002Get rights and content

Abstract

Bacterial biofilms cause a considerable amount of prosthetic joint infections every year, resulting in morbidity and expensive revision surgery. To address this problem, surface modifications of implant materials such as carbon nanotube (CNT) coatings have been investigated in the past years. CNTs are biologically compatible and can be utilized as drug delivery systems. In this study, multi-walled carbon nanotube (MWCNT) coated TiAl6V4 titanium alloy discs were fabricated and impregnated with Rifampicin, and tested for their ability to prevent biofilm formation over a period of ten days. Agar plate-based assays were employed to assess the antimicrobial activity of these surfaces against Staphylococcus epidermidis. It was shown that vertically aligned MWCNTs were more stable against attrition on rough surfaces than on polished TiAl6V4 surfaces. Discs with coated surfaces caused a significant inhibition of biofilm formation for up to five days. Therefore, MWCNT-modified surfaces may be effective against pathogenic biofilm formation on endoprostheses.

Graphical Abstract

Rough TiAl6V4 titanium alloy surfaces covered homogenously with multi-walled carbon nanotubes (MWCNTs) can be effectively loaded with antibiotics by means of capillary forces. Here, very low concentrations of Rifampicin caused notable inhibition zones and suppression of S. epidermidis biofilm formation even after 5 days, suggesting a slow release of the antibiotic agent. This promising finding can be helpful to design prosthetic implant devices with antibacterial properties, yet allowing for attachment and survival of host cells such as osteoblasts. Thus, initial healing after surgery can be promoted and the incidence of harmful prosthetic joint infection may be reduced.

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Section snippets

MWCNT-coating of titanium alloy discs and scanning electron microscopy (SEM)

Vertically aligned MWCNTs were grown on roughened TiAl6V4 titanium alloy disc surfaces via plasma enhanced chemical vapor deposition (PECVD).23 The roughness of the surfaces is specified with Rz = 10 μm. Prior to the MWCNT growth, a 10 nm thin layer of nickel was deposited via electron beam evaporations that forms Ni droplets upon melting at the PECVD process temperature of approximately 750 °C. These liquid Ni droplets act as catalysts in a tip growth type vapor–liquid–solid (VLS) mechanism

Results

A major problem of current anti-microbial coatings (e.g. silver) is the massive cytotoxic effect, which impairs biofilm formation but also prevents bone regeneration.29 Therefore, anti-microbial nanostructures have to be capable of preventing biofilm formation for prolonged periods of time. At the same time, they must allow for, or even stimulate, differentiation of stem cells into bone. Based on our previous work showing that MWCNT are ideal substrates for differentiation of osteoblasts from

Discussion

CNTs and materials based on nanotubes have several potential applications in medicine and biomedicine. They can act as growth substrates, tissue scaffolds or as carriers for various therapeutic and diagnostic agents.33, 34, 35 In the literature, loading of CNT and other nanotubular structures with osteogenic substances and growth factors has been described.36, 37, 38 Data on loading of CNTs with AB for prolonged drug delivery in this context, however, are limited.39, 40 The present study is, to

Acknowledgments

The authors would like to thank Dr. Klaus Ellmer from the Helmholtz Zentrum Berlin and Prof. Dr. James Deschner from the Center of Dental and Oral Medicine in Bonn for their valuable support throughout this study.

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      Citation Excerpt :

      Due to the increasing number of untreatable biofilms by conventional antimicrobial therapies, there is a strong need for the development of novel strategies to prevent biofilm development on biomedical surfaces. Surfaces coated with CNTs succeed in preventing bacterial adhesion and the subsequent biofilm growth on medical devices and prosthetic implants (Aslan et al., 2010; Hirschfeld et al., 2017). However, there are some concerns about the possible toxicity of CNTs in both human and animal cells, and their hydrophobic nature and biocompatibility (Saliev, 2019; Upadhyayula and Gadhamshetty, 2010).

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    Author Contributions: E.M.A. and M.G. designed and manufactured the MWCNT-covered TiAl6V4 titanium alloy surfaces. J.H. conducted the microbiological assays. M.G. and A.L. conceived the projects and designed the experiments. D.C.W. and M.H. provided input on implementing the experiments. A.H., I.B.-D. and S.J. contributed to the manuscript revision. The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

    Conflict of interest and financial disclosure: The authors declare that there is no conflict of interest regarding the publication of this paper. This work was supported by the German Society for Dental and Oral Medicine (DGZMK) and by the German Society of Periodontology (DGParo/2-RST-13).

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    These authors contributed equally.

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