Application of biomimetic titanium surfaces to control bacterial attachment

The design of bacterial antifouling surfaces by surface structuring is one attractive solution for the prevention of bacterial adhesion and the subsequent formation of a biofilm. Two tier micro- and nanoscale quasi periodic self-organized structures were fabricated on titanium surfaces using femtosecond laser ablation. The first tier was comprised of large, grain-like convex features with a size ranging between 10 µm and 20 µm. The surface of the grains formed a second tier, possessing 200 nm (or less) wide irregular undulations. The biomimetic surface structuring transformed initially hydrophilic titanium surfaces with water contact angle of θW 73° ± 3° into superhydrophobic surfaces with a water contact angle θW of 166° ± 4°. Investigations of S. aureus and P. aeruginosa interactions with superhydrophobic surfaces at the surface-liquid interface revealed a highly selective adhesion pattern for two pathogenic bacteria. It was found that while S. aureus cells were able to successfully colonise the superhydrophobic titanium surfaces, the attachment of the P. aeruginosa cells was vastly reduced, with the adhered cell numbers being found to be below the estimated lower detection limit

Bacterial retention on superhydrophobic titanium surfaces fabricated by femtosecond laser ablation

Two-tier micro- and nanoscale quasi-periodic self-organized structures, mimicking the surface of a lotus Nelumbo nucifera leaf, were fabricated on titanium surfaces using femtosecond laser ablation. The first tier consisted of large grainlike convex features between 10 and 20 μm in size. The second tier existed on the surface of these grains, where 200 nm (or less) wide irregular undulations were present. The introduction of the biomimetic surface patterns significantly transformed the surface wettabilty of the titanium surface. The original surface possessed a water contact angle of θW 73 ± 3°, whereas the laser-treated titanium surface became superhydrophobic, with a water contact angle of θW 166 ± 4°. Investigations of the interaction of S. aureus and P. aeruginosa with these superhydrophobic surfaces at the surface−liquid interface revealed a highly selective retention pattern for two pathogenic bacteria. While S. aureus cells were able to successfully colonize the superhydrophobic titanium surfaces, no P. aeruginosa cells were able to attach to the surface (i.e., any attached bacterial cells were below the estimated lower detection limit)

Effect of titanium surface topography on plasma deposition of antibacterial polymer coatings

Plasma processing, e.g., functionalisation and deposition of antibacterial coatings, is often used to enhance surface properties of biomaterials. Plasma is, however, a non-uniform active medium, and the result of processing depends on the nature of both the plasma and the substratum. Here we show that when an antibacterial coating (i.e., polyterpenol) is plasma polymerised onto four types of titanium substrata that differ in their micro- and nano-scale topography (but not the bulk chemistry), the distribution of functional groups, e.g., --OH and --C==O, in the polymer across the surface differs sufficiently, and so does the antibacterial activity of the resulting material system. While the addition of a coating hinders biofilm formation by Staphylococcus aureus and Pseudomonas aeruginosa, the bactericidal effect is significantly stronger in polymers deposited onto surfaces possessing lower degrees of nanoscale roughness, e.g., substrata after mechanical and chemical polishing. The reduced antibacterial efficacy of polymers on substrata with greater surface roughness (e.g., on mechanically polished or lotus leaf-like surfaces) is attributed to a greater extent of thickness non-uniformity and heterogeneity in the functional group distribution across the surface. These findings suggest that the magnitude and distribution of topographical features of the substratum should be considered when designing plasma-enabled surface modification strategies

Strontium substituted tricalcium phosphate bone cement: short and long-term time-resolved studies and in vitro properties

Due to a significant influence of strontium (Sr) on bone regeneration, Sr substituted beta-tricalcium phosphate (Sr-TCP) cement is prepared and investigated by short- and long-term time-resolved techniques. For short-term investigations, energy-dispersive X-ray diffraction, infrared spectroscopy, and, for the first time, terahertz time-domain spectroscopy techniques are applied. For long-term time-resolved studies, angular dispersive X-ray diffraction, scanning electron microscopy, mechanical tests, and behavior in Ringer solution are carried out. After 45 min of the cement setting, the Sr-TCP phase is no longer detectable. During this time period, an appearance and constant increase of the final brushite phase are registered. The compressive strength of the Sr-TCP cement increases from 4.5 MPa after 2 h of setting and reaches maximum at 13.3 MPa after 21 d. After cement soaking for 21 d in Ringer solution, apatite final product, with an admixture of brushite and TCP phases is detected. The cytotoxicity aspects of the prepared cement are investigated using NCTC 3T3 fibroblast cell line, and the cytocompatibility-by human dental pulp mesenchymal stem cells. The obtained results allow to conclude that the developed Sr-TCP cement is promising for biomedical applications for bone tissue