Abstract
Antibacterial coating of medical devices is a promising approach to reduce the risk of infection but has not yet been achieved on wear surfaces, e.g. polyethylene (PE). We quantitatively determined the antimicrobial potency of different PE surfaces, which had been conversed to diamond-like carbon (DLC-PE) and doped with silver ions (Ag-DLC-PE). Bacterial adhesion and planktonic growth of various strains of S. epidermidis on Ag-DLC-PE were compared to untreated PE 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 Ag-DLC-PE. (2) The antimicrobial effect was positively correlated with the applied fluences of Ag (fivefold reduced bacterial surface growth and fourfold reduced bacterial concentration in the surrounding medium with fluences of 1 × 1017 vs. 1 × 1016 cm−2 under implantation energy of 10 keV). (3) A low depth of Ag penetration using low ion energies (10 or 20 vs. 100 keV) led to evident antimicrobial effects (fourfold reduced bacterial surface growth and twofold reduced bacterial concentration in the surrounding medium with 10 or 20 keV and 1 × 1017 cm−2 vs. no reduction of growth with 100 keV and 1 × 1017 cm−2). (4) Biofilm formation was decreased by Ag-DLC-PE surfaces. The results obtained in this study suggest that PE-surfaces can be equipped with antibacterial effects and may provide a promising platform to finally add antibacterial coatings on wear surfaces of joint prostheses.
Highlights
The great success of surgically-implanted biomaterials may be compromised in every case by the challenging complication of bacterial periimplant infection (Liu et al 2012; Zimmerli and Ochsner 2003)
(1) A significant (p < 0.05) antimicrobial effect could be found for Ag-diamond-like carbon (DLC)-PE. (2) The antimicrobial effect was positively correlated with the applied fluences of Ag. (3) A low depth of Ag penetration using low ion energies (10 or 20 vs. 100 keV) led to evident antimicrobial effects. (4) Biofilm formation was decreased by Ag-diamond-like carbon coating on polyeth‐ ylene (DLC-PE) surfaces
On silver incorporated diamond-like carbon coating (Ag-DLC)-PE samples treated with only 60 keV a significantly and clinically relevant decreased bacterial growth was evident (Table 1; Fig. 3)
Summary
The great success of surgically-implanted biomaterials may be compromised in every case by the challenging complication of bacterial periimplant infection (Liu et al 2012; Zimmerli and Ochsner 2003). Alternatives to local antibiotic delivery systems are highly favored In this context employment of implant materials or coatings that control infection and biofilm formation would be advantageous (Schmidmaier et al 2006). In contrast non-antibiotic “active” antibacterial coatings release antibacterial agents, e.g. silver ions (Ag+), copper ions (Cu++), nitric oxide, chlorhexidine/chloroxylenol or chitosan (Kumar and Munstedt 2005; Hardes et al 2007; Gosheger et al 2004; Shirai et al 2009). Compared to antibiotics these agents act more broadly against a wide range of bacteria. At least proven for the use of Ag+, microbes without intrinsic resistance cannot gain resistance (Kumar and Munstedt 2005; Lee et al 2005)
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