ABSTRACT
The method of micro-arc oxidation has been utilized to synthesize a protective biocompatible coating for a bioresorbable orthopedic Mg implant. This paper presents the results of comprehensive research of micro-arc coatings based on diatomite-a biogenic material consisting of shells of diatom microalgae. The main focus of this study was the functionalization of diatomite-based micro-arc coatings by incorporating particles of titania (TiO2) into them. Various properties of the resulting coatings were examined and evaluated. XRD analysis revealed the formation of a new magnesium orthosilicate phase-forsterite (Mg2SiO4). It was established that the corrosion current density of the coatings decreased by 1-2 orders of magnitude after the inclusion of TiO2 particles, depending on the coating process voltage. The adhesion strength of the coatings increased following the particle incorporation. The processes of dissolution of both coated and uncoated samples in a sodium chloride solution were studied. The in vitro cell viability was assessed, which showed that the coatings significantly reduced the cytotoxicity of Mg samples.
ABSTRACT
In the present work, the surface of a biodegradable Mg alloy was modified to create porous diatomite biocoatings using the method of micro-arc oxidation. The coatings were applied at process voltages in the range of 350-500 V. We have studied the influence of the addition of ZrO2 microparticles on the structure and properties of diatomite-based protective coatings for Mg implants. The structure and properties of the resulting coatings were examined using a number of research methods. It was found that the coatings have a porous structure and contain ZrO2 particles. The coatings were mostly characterized by pores less than 1 µm in size. However, as the voltage of the MAO process increases, the number of larger pores (5-10 µm in size) also increases. However, the porosity of the coatings varied insignificantly and amounted to 5 ± 1%. It has been revealed that the incorporation of ZrO2 particles substantially affects the properties of diatomite-based coatings. The adhesive strength of the coatings has increased by approximately 30%, and the corrosion resistance has increased by two orders of magnitude compared to the coatings without zirconia particles.
ABSTRACT
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.
