Abstract
Introduction
According to the Australian registry 2014, periprosthetic joint infection (PJI) is the fourth important reason for revision of a primary total hip arthroplasty (THA). PJI is frequently caused by commensal strains of the skin such as Staphylococcus aureus or Staphylococcus epidermis. Deep infection is depending on many factors, such as implant surface chemical and physical behaviour, device design, host site, surgery and host response. Nevertheless, a lack of knowledge is seen concerning the specific effects of different surfaces on the biological response of different biomaterials. In addition, it is difficult to discriminate the material chemico-physical properties by the topological features, such as surface roughness. Indeed, it has been widely demonstrated that surface composition, electric charge, wettability and roughness of implant surfaces have a strong influence on their interactions with biological fluids and tissues. Therefore, also bearing surface properties can influence the incidence of PJI, just shown recently.
Objectives
To verify the capability of ceramic bearings to reduce bacteria biofilm adhesion by means of their surface chemico-physical properties.
Methods
The surface chemico-physical properties of the most common materials in THA as monolithic alumina, zirconia platelet toughened alumina (ZPTA), zirconia (TZP), titanium alloy (Ti6Al4V), stainless-steel and cobalt alloy (Co28Cr6Mo) were compared. All materials were characterized using x-ray photoelectron spectroscopy (XPS), fourier transform spectroscopy (FTIR), x-ray diffraction (XRD) and zeta-potential. Additionaly wettability by contact angle measurement with various media as simulated body fluid (SBF), bacterial broth, cell culture media and fetal bovine serum (FBS) was determined. Furthermore, the surface protein adsorption amount was evaluated by bicinchoninic acid (BCA) assay analysis using FBS as protein source. Selective protein adsorption was also evaluated by electroforetic technique. The specimens' surface anti-bacterial adhesion activity was evaluated by Staphylococcus aureus biofilm formation after 24h by colonies forming units count. Cytocompatibility was assessed using human primary osteoblasts cell culture and MTT assay.
Results
The surface of all tested materials was found to be electronegative at physiological pH by means of zeta-potential measurement. Nevertheless, monolithic alumina and ZPTA have the isolectric point at lower pHs and adsorbed a larger amount of proteins (albumin and fibronectin) in comparison with metal surfaces. Such feature might be correlated with bacteria biofilm growth, since the ceramic surfaces were also less colonized by Staphylococcus aureus in comparison to metal surfaces (p<0.005) while they maintained the ability to promote osteoblasts adhesion and proliferation. The above results were confirmed by XPS technique where the ceramic surfaces had less hydroxyl groups and consequently were less prone to adhere with biological species as the bacteria. No correlation was observed using the FTIR and XRD surface characterization techniques.
Conclusions
The ceramic bearing surfaces were found to reduce the bacteria biofilm adhesion, because of their surface chemico-physical properties.
