In vitro antibacterial properties and UV induced response from Staphylococcus epidermidis on Ag/Ti oxide thin films

Early-stage corrosion, ion release, and the antibacterial effect of copper and cuprous oxide in physiological buffers: Phosphate-buffered saline vs Na-4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid

Copper surfaces are well known for their antibacterial effects due to the release of copper ions. This benefit has been shown in many antibacterial efficiency tests, however, without considering the corrosion behaviors of copper in the physiological solutions, which could play an indispensable role in ion release from the metallic surface. This study compared the ground copper surface and sputtered cuprous oxide (Cu₂O) coating in two common physiological buffers: phosphate-buffered saline (PBS) and Na-4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (Na-HEPES). The growth of the cuprous oxide (Cu₂O) layer was found on copper in pure PBS, inhibiting further copper ion release. In contrast, a continuous release of copper ions was recorded in Na-HEPES for 3 h, where no oxide formation was observed. The antibacterial efficiency of copper (against E. coli) was measured and discussed with the ion release kinetics in the presence of E. coli. Similar results were obtained from Cu₂O coating, ruling out its assisting role in showing the antibacterial property from copper surfaces, but they did indicate the importance of taking environmental parameters into consideration in interpreting the antibacterial efficiency of copper surfaces.

Development of Antibacterial Ti-Cux Alloys for Dental Applications: Effects of Ageing for Alloys with Up to 10 wt% Cu

Peri-implantitis, a disease caused by bacteria, affects dental implants in patients. It is widely treated with antibiotics, however, with growing antibiotic resistance new strategies are required. Titanium-copper alloys are prospective antibacterial biomaterials, with the potential to be a remedy against peri-implantitis and antibiotic resistance. The aim of this study was to investigate Ti-Cu_x alloys, exploring how Cu content (up to 10 wt%) and ageing affect the material properties. Electron microscopy, X-ray diffraction, hardness testing, bacteriological culture, and electrochemical testing were employed to characterize the materials. It was found that alloys with above 3 wt% Cu had two phases and ageing increased the volume fraction of Ti₂Cu. An un-aged alloy of 5 wt% Cu showed what could be Ti₃Cu, in addition to the α-Ti phase. The hardness gradually increased with increased Cu additions, while ageing only affected the alloy with 10 wt% Cu (due to changes in microstructure). Ageing resulted in faster passivation of the alloys. After two hours the aged 10 wt% Cu alloy was the only material with an antibacterial effect, while after six hours, bacteria killing occurred in all alloys with above 5 wt% Cu. In conclusion, it was possible to tune the material and antibacterial properties of Ti-Cu_x alloys by changing the Cu concentration and ageing, which makes further optimization towards an antibacterial material promising.

Investigation of the Antibacterial Effect of Mesoporous Magnesium Carbonate

Mesoporous magnesium carbonate (MMC) was first presented in 2013, and this material is currently under consideration for use in a number of biotechnological applications including topical formulations. This study presents the first evaluation of the antibacterial properties of the material with mesoporous silica and two other magnesium-containing powder materials used as references. All powder materials in this study are sieved to achieve a particle size distribution between 25 and 75 μm. The Gram-positive bacterium Staphylococcus epidermidis is used as the model bacterium due to its prevalence on human skin, its likelihood of developing resistance to antibiotics, for example, from routine exposure to antibiotics secreted in sweat, and because it is found inside affected acne vulgaris pores. Quantification of bacterial viability using a metabolic activity assay with resazurin as the fluorescent indicator shows that MMC exerts a strong antibacterial effect on the bacteria and that alkalinity accounts for the major part of this effect. The results open up for further development of MMC in on-skin applications where bacterial growth inhibition without using antibiotics is deemed favorable.