Ionic Silver and Electrical Treatment for Susceptibility and Disinfection of Escherichia coli Biofilm-Contaminated Titanium Surface

In this work, surface disinfection and biofilm susceptibility were investigated by applying ionic silver of 0.4–1.6 µg/mL and cathodic voltage-controlled electrical treatment of 1.8 V and a current of 30 mA to Escherichia coli (E. coli) ATCC 25922 biofilm-contaminated titanium substrates. Herein, it is evident that the treatment exhibited the potential use to enhance the susceptibility of bacterial biofilms for surface disinfection. In vitro studies have demonstrated that the ionic silver treatment of 60 min significantly increased the logarithmic reduction (LR) of bacterial populations on disinfectant-treated substrates and the electrical treatment enhanced the silver susceptibility of E. coli biofilms. The LR values after the ionic silver treatments and the electric-enhanced silver treatments were in the ranges of 1.94–2.25 and 2.10–2.73, respectively. The treatment was also associated with morphological changes in silver-treated E. coli cells and biofilm-contaminated titanium surfaces. Nevertheless, the treatments showed no cytotoxic effects on the L929 mouse skin fibroblast cell line and only a slight decrease in pH was observed during the electrical polarization of titanium substrate.

The Effect of Silicon in Al-Si Alloys and Electrical Treatment Modes on Structure and Properties of MAO-Coatings

The work shows the influence of the content of silicon in the aluminum alloy and the regimes of micro-arc oxidation (MAO) on the structure and properties of the formed coatings. Treatment of samples from high-silicon aluminum alloys AK12pch (Si ~12 %) and M244 (Si ~25 %) was carried out in two modes, which have different installation capacity MAO. The thickness, micro-hardness, porosity of the formed MAO coatings was investigated. It is established that the increase in the proportion of silicon in the aluminum alloy leads to the formation of MAO coatings of significant thickness (~230 μm), with low micro-hardness (HV ~650) and high porosity (up to ~16 %). Increase 4 times the installation capacity of MAO causes the growth of the thickness of the coating, reduces the porosity of the coating on the alloy AK12pch and increases the porosity of the coating on the alloy M244.