Antibacterial efficacy of titanium-containing alloy with silver-nanoparticles enriched diamond-like carbon coatings.

Norbert Harrasser,Hans Gollwitzer,Sebastian Jüssen,Ingo J Banke,Ralf Kmeth,Ruediger Von Eisenhart-Rothe,Rainer Burgkart,Bernd Stritzker

doi:10.1186/s13568-015-0162-z

Norbert Harrasser, Hans Gollwitzer + Show 6 more

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Silver ions (Ag+) have strong bactericidal effects and Ag-coated medical devices proved their effectiveness in reducing infections in revision total joint arthroplasty. We quantitatively determined the antimicrobial potency of different surface treatments on a titanium alloy (Ti), which had been conversed to diamond-like carbon (DLC-Ti) and doped with high (Ag:PVP = 1:2) and low (Ag:PVP = 1:10 and 1:20) concentrations of Ag (Ag-DLC-Ti) with a modified technique of ion implantation. Bacterial adhesion and planktonic growth of clinically relevant bacterial strains (Staphylococcus epidermidis,Staphylococcus aureus, and Pseudomonas aeruginosa) on Ag-DLC-Ti were compared to untreated Ti by quantification of colony forming units on the adherent surface and in the growth medium as well as semiquantitatively by determining the grade of biofilm formation by scanning electron microscopy. (1) A significant (p < 0.05) antimicrobial effect could be found for all Ag-DLC-Ti samples (reduced growth by 5.6–2.5 logarithmic levels). (2) The antimicrobial effect was depending on the tested bacterial strain (most for P. aeruginosa, least for S. aureus). (3) Antimicrobial potency was positively correlated with Ag concentrations. (4) Biofilm formation was decreased by Ag-DLC-Ti surfaces. This study revealed potent antibacterial effects of Ag-DLC-Ti. This may serve as a promising novel approach to close the gap in antimicrobial protection of musculoskeletal implants.

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With a constantly rising demand for orthopedic surgery with approximately 2.6 million orthopedic implants performed annually in the United States, the frequency of associated infections is bound to increase (Liu et al 2012; Zimmerli and Ochsner 2003; Kurtz et al 2008)
On untreated Ti plates on average 2.1 × colony forming units (CFU) of S. epidermidis, 7.3 × CFU of S. aureus and 1.6 × 106 CFU of P. aeruginosa adhered after 24 h of incubation (Fig. 3)
We found significant antibacterial activity in the surrounding environment of the tested samples showing release of embedded bactericidal agents from the diamond-like carbon (DLC) coating. In this context main properties of the tested coatings could be identified: 1. Antimicrobial effectiveness increased with higher concentrations of Ag in diamondlike carbon coating on titanium (DLC-Ti)

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Introduction

With a constantly rising demand for orthopedic surgery with approximately 2.6 million orthopedic implants performed annually in the United States, the frequency of associated infections is bound to increase (Liu et al 2012; Zimmerli and Ochsner 2003; Kurtz et al 2008). Promising could be the use of non-antibiotic “active” antibacterial coatings which release antibacterial agents, e.g. silver ions (Ag+) (Gosheger et al 2004; Hardes et al 2007; Harrasser et al 2015), copper ions (Cu++) (Shirai et al 2009; Baena et al 2006), nitric oxide (Holt et al 2011; Nablo et al 2005), chlorhexidine/chloroxylenol (Darouiche et al 1998) or chitosan (Bumgardner et al 2003). The risk of detachment of the DLC coating from the surface, even under shear forces is minimized (Schwarz and Stritzker 2010; Popa et al 2013) In this context, among the techniques described for the synthesis of DLC coatings a modified method of plasma immersion ion implantation (PIII) has proven promising advantages (Schwarz and Stritzker 2010)

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