Comparative investigation of antibacterial yet biocompatible Ag-doped multicomponent coatings obtained by pulsed electrospark deposition and its combination with ion implantation

The aim of this work is to obtain antibacterial yet biocompatible coatings using pulsed electrospark deposition (PED). For this purpose new composite electrodes were fabricated from reaction mixtures Ti-C-20%Fe-10%Ca3(PO4)2-3.4%Mg-X%Ag with different amount of antibacterial component (X = 0, 0.5, 1.0, 1.5 and 2.0 at% of Ag) using self-propagating high-temperature synthesis method. The electrodes consisted of TiC grains surrounded by TiFe2 and TiFeP intermetallic matrix, CaO and MgO inclusions, and Ag-based phase. The influence of Ag content on the electrode mass transfer kinetics was studied by comparing the total substrate weight gain and electrode mass loss during PED. The structure, elemental composition, and surface roughness of coatings were studied by means of X-ray diffraction, scanning electron microscopy, and optical profilometry. The coatings were characterized in terms of Ag+ ion release, mechanical and electrochemical properties, as well as biocompatibility. The antibacterial characteristics of Ag-doped PED coatings were compared with those obtained by PED using Ag-free electrode and then implanted with Ag+ ions. The results indicated that an increase in the Ag content in electrode leads to a decrease in electrode erosion and substrate weight gain, but the efficiency of the PED process increases. Doping with a small amount of Ag (≤ 1 at%) resulted in 100% antibacterial effect against both gram-positive S. aureus and gram-negative E. сoli bacteria. In addition, the dynamics of МС3Т3-Е1 cell proliferation on the surface of PED coatings with 0.6-0.7 at% of Ag was similar to that in control samples, hereby indicating their biocompatibility. The coating biological characteristics were discussed based on the results of Ag+ ion release and electrochemical tests.