Biocompatible Silver-containing a-C:H and a-C coatings: A Comparative Study

Biocompatible Silver-containing a-C:H and a-C coatings: A comparative Study Jose Luis Endrino, Matthew Allen, Ramon Escobar Galindo, Hanshen Zhang, Andre Anders, Jose Maria Albella ABSTRACT Hydrogenated diamond-like-carbon (a-C:H) and hydrogen-free amorphous carbon (a-C) coatings are known to be biocompatible and have good chemical inertness. For this reason, both of these materials are strong candidates to be used as a matrix that embeds metallic elements with antimicrobial effect. In this comparative study, we have incorporated silver into diamond-like carbon (DLC) coatings by plasma based ion implantation and deposition (PBII&D) using methane (CH 4 ) plasma and simultaneously depositing Ag from a pulsed cathodic arc source. In addition, we have grown amorphous carbon – silver composite coatings using a dual- cathode pulsed filtered cathodic-arc (FCA) source. The silver atomic content of the deposited samples was analyzed using glow discharge optical spectroscopy (GDOES). In both cases, the arc pulse frequency of the silver cathode was adjusted in order to obtain samples with approximately 5 at.% of Ag. Surface hardness of the deposited films was analyzed using the nanoindentation technique. Cell viability for both a-C:H/Ag and a-C:/Ag samples deposited on 24-well tissue culture plates has been evaluated. INTRODUCTION In order to manufacture novel biocompatible coatings with tunable bio-reactions, a promising approach is to start from an existing biocompatible coating such as DLC and alloying it with bioactive elements. Diamond-like-carbons are well known to prevent inflammatory and allergic reactions but, by themselves, cannot produce any antibacterial bioactivity. In a recent article, R. Hauert (Swiss Federal Laboratories, EMPA) described the biocidal function of DLC films doped with certain toxic elements such as silver, copper and vanadium [1]. In general, the underlying idea is that by varying the alloy element concentration, it is possible to tailor the biological reactions of a composite metal-DLC film to a desired point where the biocidal effect of the metal is maximized without jeopardizing the biocompatibility of the material. In the present study, we attempt to compare both the viability of mouse MC3T3 osteoblastic cells and the mechanical properties of nanocomposite hydrogenated and hydrogen-free DLC-Ag coatings prepared using two different deposition techniques: i) plasma based ion implantation and deposition (PBII&D)[2] and by ii) metal plasma immersion ion implantation and deposition (MePIIID) [3]. EXPERIMENTAL DETAILS The four doped and non-doped diamond-like carbon films discussed in this study have been deposited using the dual-cathode arc plasma source deposition system shown in figure 1. This system is equipped with a computer-controlled bias amplifier such as to synchronize substrate bias with the pulsed production of plasma. The hydrogen-free films were deposited in