Abstract
INTRODUCTION
Biomaterial-related infections are an important complication in orthopaedic surgery [1], and Staphylococcus sp. accounts for more than half of the prosthetic joint infection cases [2]. Adhesion of bacteria to biomaterial surfaces is a key step in pathogenesis of such infections [3]. Titanium alloys are widely used in orthopaedic implants because their biocompatibility [4]. Surface incorporation of ions with antimicrobial properties, like fluorine, is one strategy previously studied with good results [5].
MATERIAL AND METHODS
A 18mm diameter rod of Ti–6Al–4V alloy ELI grade according to the standard ASTMF136-02 supplied by SURGIVAL was cut into 2 mm thick disk specimens, ground through successive grades of SiC paper to 1200 grade, degreased with a conventional detergent and rinsed in tap water followed by deionised water. The specimens were then chemically polished (CP).
The disks were anodized only on one side by using a two electrode cell in a suitable electrolyte. TiO2 barrier layers, without fluoride (BL), were produced by anodizing in 1 M H2SO4 at 15 mA cm-2 to 90 V, reaching 200 nm of thickness.
Fluoride barrier layers (FBL) were produced in an electrolyte containing 1 M NH4H2PO4 and 0.15 M NH4F, at constant voltage controlled at 20 V for 120 min at 20°C; the thickness of the layer is 140 nm.
Laboratory biofilm-forming strains of Staphylococcus aureus 15981 [6] and Staphylococcus epidermidis ATCC 35984 were used in adherence studies, which were performed using the protocol by Kinnari et al [7]. Photographs obtained were studied by ImageJ software. Statistical analysis was performed by EPI-INFO software. The experiments were performed in triplicates
RESULTS
Lower adherence was detected when compared FBL with unmodified controls (CP and BL). A statistical significant difference (p<0.01) was detected in the adhesion to modified material between both species, being the adherence of S. aureus lower than that of S. epidermidis (Figure 1).
DISCUSSION & CONCLUSIONS
There is currently a discussion about the actual antibacterial properties of fluorine when incorporated in biomaterial surfaces. In this study we have demonstrated that both S. aureus and S. epidermidis strains showed a decrease of bacterial adhesion to modified surfaces with fluorine, a decrease that cannot be due to other surface modifications. Further studies, including adhesion studies with clinical strains [8], must be performed to confirm these results, which can lead to the development of new materials with a potential use in orthopaedic surgery.
