Abstract
This study examines bacterial adhesion on titanium-substrates used for bone implants. Adhesion is the most critical phase of bacterial colonization on medical devices. The surface of titanium was modified by hydrothermal treatment (HT) to synthesize nanostructured TiO2-anatase coatings, which were previously proven to improve corrosion resistance, affect the plasma protein adsorption, and enhance osteogenesis. The affinity of the anatase coatings toward bacterial attachment was studied by using a green fluorescent protein-expressing Escherichia coli (gfp-E. coli) strain in connection with surface photoactivation by UV irradiation. We also analyzed the effects of surface topography, roughness, charge, and wettability. The results suggested the dominant effects of the macroscopic surface topography, as well as microasperity at the surface roughness scale, which were produced during titanium machining, HT treatment, or both. Macroscopic grooves provided a preferential site for bacteria deposit within the valleys, while the microscopic roughness of the valleys determined the actual interaction surface between bacterium and substrate, resulting in an "interlocking" effect and undesired high bacterial adhesion on nontreated titanium. In the case of TiO2-coated samples, the nanocrystals reduced the width between the microasperities and thus added nanoroughness features. These factors decreased the contact area between the bacterium and the coating, with consequent lower bacterial adhesion (up to 50% less) in comparison to the nontreated titanium. On the other hand, the pronounced hydrophilicity of one of the HT-coated discs after pre-irradiation seemed to enhance the attachment of bacteria, although the increase was not statistically significant (p > 0.05). This observation may be explained by the acquired similar degree of wetting between gfp-E. coli and the coating. No correlation was found between the bacterial adhesion and the ζ-values of the samples in PBS, so the effect of surface charge was considered negligible in this study.
Highlights
Over the past decade, the clinical demand for high-performance medical devices has contributed to a notable increase in research on biomaterials
The results suggested the dominant effects of the macroscopic surface topography, as well as microasperity at the surface roughness scale, which were produced during titanium machining, hydrothermal treatment (HT) treatment, or both
On the basis of the state-of-the-art research reviewed in the Introduction, we hypothesized that the hydrothermally treated nanocrystalline anatase coatings on titanium would favor the inhibition of bacterial adhesion due to the peculiar topography and good wettability of these coatings, especially after UV photoactivation
Summary
The clinical demand for high-performance medical devices has contributed to a notable increase in research on biomaterials. In the field of hard tissue replacement, several significant steps have improved titanium-based implants in terms of mechanical properties (to resemble the healthy bone performances as much as possible), osseointegration (to overcome the bioinertness of the raw metals), corrosion resistance, and the rate of the release of metal ions (to avoid aseptic loosening of the implant). The relevant number of biomaterial-centered infections (BCI) and, prosthetic implant infections (PIIs) represents a serious medical problem that significantly contributes to prosthetic implant failure and its aseptic loosening.[2,3] The primary cause of PIIs is presurgical contamination, which may result in infections within 3 months of implantation.[4] A 6 h postimplantation time is considered as the “decisive period” for implant surface colonization.[5] Chronic PIIs are usually due to the formation of a microbial biofilm. The most common approaches for Received: October 16, 2014 Accepted: December 26, 2014 Published: December 26, 2014
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