Staphyloccocus aureus and Staphyloccocus epidermidis: Biofilm development on new titanium alloys for implant materials in orthopedy

Objectives Peri-prosthetic infections (PIs) are among the most serious complications following joint replacement surgeries and are caused by the adhesion of bacteria to the implant material. Bacteria can form biofilms on the implanted medical devices and these infections are difficult to treat. Often a replacement of the implant is needed. Modifications to the surface and/or to components of the implant material are amongst the strategies for inhibiting biofilm development on prostheses. Various types of titanium-aluminium-vanadium (TiAl6V4) alloys such as silver-, titanium nitride-, hydroxyapatite-, tricalcium phosphate- and rough blasted titanium-coatings as well as pure titanium, were tested to assess their anti-biofilm effects. The two most common causative agents of PIs - Staphylococcus aureus and Staphylococcus epidermidis were used as model organisms.

Methods To induce biofilm formation, sterile coin-formed alloy platelets were incubated with either S. aureus or S. epidermidis in 24 well plates. Cell solutions were prepared with a starting cell density of McFarland 0.5 in lysogeny broth for 48h (37°C and 90 rpm). The biofilms were collected by scratching them off the surface of the plates with cell scrapers and the suspension was transferred into test-tubes for homogenization in PBS (phosphate buffer) by vortexing. For assessment of the protein content of the biofilms the Pierce BCA protein assay (Thermo Fisher Scientific) was used. Polysaccharides were measured using the phenol-sulfuric acid method. A live/dead cell count was performed with flow cytometry and the LIVE/DEAD BacLight Bacterial Viability Kit (Thermo Fisher Scientific).

Statistical analysis of the data was performed using R studio.

Results and Conclusion Results show that biofilms formed on the rough surfaces - like TiAl6V4-tricalciumphosphate and rough blasted titanium - produced higher concentration of both, proteins and polysaccharides. On the smooth surfaces - like TiAl6V4-TiN

• lower concentrations of proteins and polysaccharides were detected. Consequently, the cell count of bacteria was higher on rough alloys compared to smooth materials. Interestingly however, alloys containing titanium-nitride and silver-coating display lower protein and polysaccharide concentrations than the other alloy types. These findings confirm that the right choice of implant material could lower the risks of PIs caused by S. aureus and S. epidermidis. More testing is needed to assess the transferability of the results to other bacterial organisms. Additionally, future studies should provide more insight into the compatibility and tolerance of the materials by human cells.

Stichwörter Biofilm, Staphylococcus, titanium

Publication History

Article published online:
15 October 2020