RESUMO
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.
RESUMO
Functionalization of titanium (Ti)-based alloy implant surfaces by deposition of calcium phosphates (CaP) has been widely recognized. Substituted hydroxyapatites (HA) allow the coating properties to be tailored based on the use of different Ca substitutes. The formation of antibacterial CaP coatings with the incorporation of Zn or Cu by an RF magnetron sputtering is proposed. The influence of RF magnetron targets elemental composition and structure in the case of Zn-HA and Cu-HA, and the influence of substrate's grain size, the substrate's temperature during the deposition, and post-deposition heat treatment (HT) on the resulting coatings are represented. Sintering the targets at 1150 °C resulted in a noticeable structural change with an increase in cell volume and lattice parameters for substituted HA. The deposition rate of Cu-HA and Zn-HA was notably higher compared to stochiometric HA (10.5 and 10) nm/min vs. 9 ± 0.5 nm/min, respectively. At the substrate temperature below 100 °C, all deposited coatings were found to be amorphous with an atomic short-range order corresponding to the {300} plane of crystalline HA. All deposited coatings were found to be hyper-stochiometric with Ca/P ratios varying from 1.9 to 2.5. An increase in the substrate temperature to 200 °C resulted in the formation of equiaxed grain structure on both coarse-grained (CG) and nanostructured (NS) Ti. The use of NS Ti notably increased the scratch resistance of the deposited coatings from18 ± 1 N to 22 ± 2 N. Influence of HT in air or Ar atmosphere is also discussed. Thus, the deposition of Zn- or Cu-containing CaP is a complex process that could be fine-tuned using the obtained research results.
RESUMO
The additive manufacturing of low elastic modulus alloys that have a certain level of porosity for biomedical needs is a growing area of research. Here, we show the results of manufacturing of porous and dense samples by a laser powder bed fusion (LPBF) of Ti-Nb alloy, using two distinctive fusion strategies. The nanostructured Ti-Nb alloy powders were produced by mechanical alloying and have a nanostructured state with nanosized grains up to 90 nm. The manufactured porous samples have pronounced open porosity and advanced roughness, contrary to dense samples with a relatively smooth surface profile. The structure of both types of samples after LPBF is formed by uniaxial grains having micro- and nanosized features. The inner structure of the porous samples is comprised of an open interconnected system of pores. The volume fraction of isolated porosity is 2 vol. % and the total porosity is 20 vol. %. Cell viability was assessed in vitro for 3 and 7 days using the MG63 cell line. With longer culture periods, cells showed an increased cell density over the entire surface of a porous Ti-Nb sample. Both types of samples are not cytotoxic and could be used for further in vivo studies.
RESUMO
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.
