Hydrothermal and plasma treatments drastically reduce bacterial adhesion to Ti-based materials used in medicine

Abstract

Event Abstract Back to Event Hydrothermal and plasma treatments drastically reduce bacterial adhesion to Ti-based materials used in medicine Martina Lorenzetti1, Špela Koželj2, Iztok Dogša2, Ita Junkar3, Mitjan Kalin4, David Stopar2 and Saša Novak1, 5 1 Jožef Stefan Institute, Department for Nanostructured Materials, Slovenia 2 University of Ljubljana, Biotechnical Faculty, Slovenia 3 Jožef Stefan Institute, Department of Surface Engineering and Optoelectronics, Slovenia 4 University of Ljubljana, Faculty of Mechanical Engineering, Slovenia 5 Jožef Stefan International Postgraduate School, Slovenia Introduction: Even though titanium and its alloys are generally considered good materials for load-bearing orthopaedic implants, microbial pre-surgical infections and biofilm formation pose a serious threat, known as “prosthetic implant infections”[1]. The infection contributes to a number of implant failures and revisions and it will become even more problematic in the near future, when a massive increase of arthroplasties is expected. In this study we focused on the production of bacterial anti-adherent coatings by applying hydrothermal treatment (HT) and/or highly reactive oxygen plasma (PL) to medical-grade titanium substrates. The microbial interaction at the biointerface was tested as the fraction of adhered bacteria to the surface. Materials and Methods: Nanocrystalline TiO2-anatase coatings were synthesised on titanium discs by HT in the presence of Ti-isopropoxide, as described previously[2]. The non-treated titanium was used as control. In addition, the samples were treated by highly reactive oxygen plasma. The samples were characterised in terms of crystal morphology (electron microscopy), wettability (sessile drop contact angle), topography and roughness (optical interferometer), surface charge (streaming potential), and chemical composition (X-ray photoelectron spectroscopy). The adhesion of a green fluorescent protein-tagged Escherichia coli bacterium on the different surfaces was tested after 1h of incubation. The fraction of strongly adhered bacteria was determined by fluorescence microscopy. Results and Discussion: The HT and PL treatments shape the surface topography, and modify the surface hydrophilicity as well as surface charge, in comparison to the pristine titanium substrate. Moreover, both HT and PL surface modifications affect the surface chemistry of titanium, as demonstrated by the increased surface oxygen content. The bacterial adhesion tests showed that after 1 h of incubation approximately 15 % of seeded bacteria strongly adhere on the bare, non-treated titanium surface. As given in Figure 1, the HT-coating significantly decreased the bacterial adhesion by an order of magnitude (2.6 %). Similar decrease was observed with the plasma treatment applied on bare titanium (2.9 %). However, when the two surface treatments were combined, a two-orders of magnitude decrease in bacterial adhesion was observed (0.25 %). The results suggest that the modification of surface topography, wettability and surface chemistry by HT and PL treatments led to a beneficial combination of surface properties which dramatically reduced the bacterial adhesion to titanium surfaces. Figure 1. Fraction of bacteria adhered to different surfaces. Ti, titanium substrate; Ti Pl, plasma-treated titanium substrate; HT, hydrothermally coated titanium substrate; HT+PL, hydrothermally coated and plasma-treated titanium substrate. Conclusion: This study demonstrates how the fine tuning of TiO2 surface properties by hydrothermal and plasma treatments significantly diminish bacterial adhesion and, consequently, prevents the biofilm formation. Therefore it is expected that the combination of the two treatments may contribute to the reduction of pre-surgical prosthetic implant infections. Authors wish to thank the Slovenian Research Agency for the financial support (P2-0084, P4-0116).