Influence of Magnesium Content on the Physico-Chemical Properties of Hydroxyapatite Electrochemically Deposited on a Nanostructured Titanium Surface

In Vitro Characterization of Hydroxyapatite-Based Coatings Doped with Mg or Zn Electrochemically Deposited on Nanostructured Titanium

Biomaterials are an important and integrated part of modern medicine, and their development and improvement are essential. The fundamental requirement of a biomaterial is found to be in its interaction with the surrounding environment, with which it must coexist. The aim of this study was to assess the biological characteristics of hydroxyapatite (HAp)-based coatings doped with Mg and Zn ions obtained by the pulsed galvanostatic electrochemical method on the surface of pure titanium (cp-Ti) functionalized with titanium dioxide nanotubes (NTs TiO2) obtained by anodic oxidation. The obtained results highlighted that the addition of Zn or Mg into the HAp structure enhances the in vitro response of the cp-Ti surface functionalized with NT TiO2. The contact angle and surface free energy showed that all the developed surfaces have a hydrophilic character in comparison with the cp-Ti surface. The HAp-based coatings doped with Zn registered superior values than the ones with Mg, in terms of biomineralization, electrochemical behavior, and cell interaction. Overall, it can be said that the addition of Mg or Zn can enhance the in vitro behavior of the HAp-based coatings in accordance with clinical requirements. Antibacterial tests showed that the proposed HAp-Mg coatings had no efficiency against Escherichia coli, while the HAp-Zn coatings registered the highest antibacterial efficiency.

Preparation and characterizations of antibacterial iodine-containing coatings on pure Ti

Iodine-containing coatings were prepared on pure Ti surfaces via electrochemical deposition to enhance their antibacterial properties. The factors influencing iodine content were analyzed using an orthogonal experiment. The electrochemically deposited samples were characterized using scanning electron microscopy with energy dispersive spectroscopy and X-ray photoelectron spectroscopy, and their antibacterial properties and cytotoxicity were evaluated. The results showed that changing the deposition time is an effective way to control the iodine content. The iodine content, coating thickness, and adhesion of the samples increased with deposition time. Iodine in the coatings mainly exists in three forms, which are I2, I3-, and pentavalent iodine. For samples with iodine-containing coatings, the antibacterial ratios against E. coli and S. aureus were greater than 90% and increased with increasing iodine content. Although the samples with iodine-containing coatings showed some inhibition of the proliferation of MC3T3-E1 cells, the cell viabilities were all higher than 80%, suggesting that iodine-containing coatings are biosafe.

Effect of Magnesium Substitution on Structural Features and Properties of Hydroxyapatite

Hydroxyapatite (HAP) is the main mineral component of bones and teeth. It is widely used in medicine as a bone filler and coating for implants to promote new bone growth. Ion substitutions into the HAP structure highly affect its properties. One of the most important substituents is magnesium. This paper presents new results obtained using high-precision hybrid density functional theory calculations for Mg/Ca substitutions in HAP in a wide magnesium concentration range within a 2 × 2 × 2 supercell model. Experimental data on the mechanochemical synthesis of HAP-Mg samples with different Mg concentrations are also presented. A comparison between the experiment and the theory showed good agreement: the HAP-Mg unit cell parameters and volume decreased with increasing degree of Mg/Ca substitution. The changes in the distances between the Ca and O, Ca and H, and Mg and O ions upon Mg/Ca substitution in different calcium positions was analyzed. The resulting asymmetry and distortion of the cell parameters were evaluated. It was shown that bulk modulus, energy levels, and band gap depend on the degree of Mg substitutions in the Ca1 and Ca2 positions. The formation energies of Mg/Ca substitutions showed non-monotonic behavior that was different for Ca1 and Ca2 positions. The Ca2 position had a slightly higher probability (~5 meV/f.u.) of substitution than Ca1 position at a Mg concentration x = 0.5. At x = 1, substitution in both positions can coexist. The simulated IR spectra for different Mg/Ca substitutions showed that Mg in the Ca2 position changes the IR spectrum more significantly than Mg in the Ca1 position. Similar changes were recorded in the IR spectra of the synthesized samples. The electronic structure is shown to be sensitive to the number and position of substitutions, which may be used to tweak the optical properties of the HAP-Mg material.