Comparative Study of the Structure, Properties, and Corrosion Behavior of Sr-Containing Biocoatings on Mg0.8Ca.

A comparative analysis of the structure, properties and the corrosion behavior of the micro-arc coatings based on Sr-substituted hydroxyapatite (Sr-HA) and Sr-substituted tricalcium phosphate (Sr-TCP) deposited on Mg0.8Ca alloy substrates was performed. The current density during the formation of the Sr-HA coatings was higher than that for the Sr-TCP coatings. As a result, the Sr-HA coatings were thicker and had a greater surface roughness Ra than the Sr-TCP coatings. In addition, pore sizes of the Sr-HA were almost two times larger. The ratio (Ca + Sr + Mg)/P were equal 1.64 and 1.47 for Sr-HA and Sr-TCP coatings, respectively. Thus, it can be assumed that the composition of Sr-HA and Sr-TCP coatings was predominantly presented by (Sr,Mg)-substituted hydroxyapatite and (Sr,Mg)-substituted tricalcium phosphate. However, the average content of Sr was approximately the same for both types of the coatings and was equal to 1.8 at.%. The Sr-HA coatings were less soluble and had higher corrosion resistance than the Sr-TCP coatings. Cytotoxic tests in vitro demonstrated a higher cell viability after cultivation with extracts of the Sr-HA coatings.

Modification of titanium surface via Ag-, Sr- and Si-containing micro-arc calcium phosphate coating.

The current research is devoted to the study of the modification of the titanium implants by the micro-arc oxidation with bioactive calcium phosphate coatings containing Ag or Sr and Si elements. The coatings' microstructure, phase composition, morphology, physicochemical and biological properties were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). Ag-containing and Sr-Si-incorporated coatings were formed in alkaline and acid electrolytes, respectively. The formation of the coatings occurred at different ranges of the applied voltages, which led to the significant difference in the coatings properties. The trace elements Ag, Sr and Si participated intensively in the plasma-chemical reactions of the micro-arc coatings formation. Ag-containing coatings demonstrated strong antibacterial effect against Staphylococcus aureus AТСС 6538-P. MTT in vitro test with 3T3-L1 fibroblasts showed no cytotoxicity appearance on Sr-Si-incorporated coatings.