Mg-substituted Hydroxyapatite Research Articles

3D-printed Mg-substituted hydroxyapatite/ gelatin methacryloyl hydrogels encapsulated with PDA@DOX particles for bone tumor therapy and bone tissue regeneration

3D-printed Mg-substituted hydroxyapatite/ gelatin methacryloyl hydrogels encapsulated with PDA@DOX particles for bone tumor therapy and bone tissue regeneration

Influence of Magnesium Source on the Mechanochemical Synthesis of Magnesium-Substituted Hydroxyapatite.

Magnesium, as one of the most abundant cations in the human body, plays an important role in both physiological and pathological processes. In this study, it was shown that a promising biomedical material, Mg-substituted hydroxyapatite (Mg-HA), can be synthesized via a fast mechanochemical method. For this method, the nature of magnesium-containing carriers was shown to be important. When using magnesium oxide as a source of magnesium, the partial insertion of magnesium cations into the apatite structure occurs. In contrast, when magnesium hydroxide or monomagnesium phosphate is used, single-phase Mg-HA is formed. Both experimental and theoretical investigations showed that an increase in the Mg content leads to a decrease in the lattice parameters and unit cell volume of Mg-HA. Density functional theory calculations showed the high sensitivity of the lattice parameters to the crystallographic position of the calcium site substituted by magnesium. It was shown experimentally that the insertion of magnesium cations decreases the thermal stability of hydroxyapatite. The thermal decomposition of Mg-HA leads to the formation of a mixture of stoichiometric HA, magnesium oxide, and Mg-substituted tricalcium phosphate phases.

Hydroxyapatite-based dental inserts: Microstructure, mechanical properties, bonding efficiency and fracture resistance of molars with occlusal restorations.

This study aimed to (1) comparatively analyze properties of Sr- and Mg-substituted hydroxyapatite (HAP)-based dental inserts; (2) evaluate insert bonding to restorative materials, and (3) evaluate the effect of doped HAP inserts on fracture resistance (FR) of human molars with large occlusal restorations. By ion-doping with Sr or Mg, 3 insert types were obtained and characterized using XRD, SEM, Vickers hardness and fracture toughness. Shear bond strength (SBS) was determined between acid etched or unetched inserts and following materials: Maxcem cement (Kerr); Filtek Z250 (3M) bonded with Single Bond Universal (SBU; 3M) or Clearfil Universal (Cf; Kuraray). Modified Class I cavities were prepared in 16 intact molars and restored using insert + composite or composite only (control) (n = 8/group). FR of restored molars was determined by static load until fracture upon thermal cycling. Fracture toughness was similar between Sr/Mg-doped inserts (0.94-1.04 MPam-1/2 p = .429). Mg-doped inserts showed greater hardness (range 4.78-5.15 GPa) than Sr6 inserts (3.74 ± 0.31 GPa; p < .05). SBS for SBU and Cf adhesives (range 7.19-15.93 MPa) was higher than for Maxcem (range 3.07-5.95 MPa) (p < .05). There was no significant difference in FR between molars restored with insert-containing and control restorations (3.00 ± 0.30 kN and 3.22 ± 0.42 kN, respectively; p > .05). HAP-based inserts doped with Mg/Sr had different composition and mechanical properties. Adhesive bonding to inserts resulted in greater bond strength than cementation, which may be improved by insert acid-etching. Ion-doped HAP inserts did not affect FR of restored molars. In conclusion, HAP-based dental inserts may potentially replace dentin in large cavities, without affecting fracture resistance of restored teeth.

Evaluation of dental pulp stem cells behavior after odontogenic differentiation induction by three different bioactive materials on two different scaffolds

BackgroundTo study the odontogenic potential of dental pulp stem cells (DPSCs) after induction with three different bioactive materials: activa bioactive (base/liner) (AB), TheraCal LC (TC), and mineral trioxide aggregate (MTA), when combined with two different types of scaffolds.MethodsDPSCs were isolated from freshly extracted premolars of young orthodontic patients, cultured, expanded to passage 4 (P), and characterized by flow cytometric analysis. DPSCs were seeded onto two scaffolds in contact with different materials (AB, TC, and MTA). The first scaffold contained polycaprolactone-nano-chitosan and synthetic hydroxyapatite (PCL-NC-HA), whereas the second scaffold contained polycaprolactone-nano-chitosan and synthetic Mg-substituted hydroxyapatite (PCL-NC-Mg-HA). DPSC viability and proliferation were evaluated at various time points. To assess odontoblastic differentiation, gene expression analysis of dentin sialophosphoprotein (DSPP) by quantitative real-time polymerase chain reaction (qRT-PCR) and morphological changes in cells were performed using inverted microscope phase contrast images and scanning electron microscopy. The fold-change in DSPP between subgroups was compared using a one-way ANOVA. Tukey's test was used to compare the fold-change in DSPP between the two subgroups in multiple comparisons, and P was set at p < 0.05.ResultsDSPP expression was significantly higher in the PCL-NC-Mg-HA group than in the PCL-NC-HA group, and scanning electron microscopy revealed a strong attachment of odontoblast-like cells to the scaffold that had a stronger odontogenic differentiation effect on DPSCs than the scaffold that did not contain magnesium. MTA has a significantly higher odontogenic differentiation effect on cultured DPSCs than AB or TC does. The combination of scaffolds and bioactive materials improves DPSCs induction in odontoblast-like cells.ConclusionsThe PCL-NC-Mg-HA scaffold showed better odontogenic differentiation effects on cultured DPSCs. Compared to AB and TC, MTA is the most effective bioactive material for inducing the odontogenic differentiation of cultured DPSCs.

A Comparative EPR Study of Non-Substituted and Mg-Substituted Hydroxyapatite Behaviour in Model Media and during Accelerated Ageing

To assess the application potential of novel biomaterials, their behaviour in model media and upon sterilization should be investigated, as well as the stability related to their storage conditions. Such data are lacking for Mg-substituted HAP (Mg-HAP). Therefore, the changes in the local structure of non-substituted and Mg-HAP after irradiation and immersion in corrected simulated fluid and saline solution for 28 days were followed by electron paramagnetic resonance (EPR) spectroscopy for the first time. To better understand the stability of radical species induced by sterilization, EPR spectra of samples kept for 2 h at temperatures up to 373 K were recorded to provide an insight into the stability of the sample storage conditions by the accelerated aging method. Samples were characterized by PXRD, FTIR, SEM, EDS, AAS and TGA. Results confirmed that irradiation does not induce changes in the composition or the structure of any of the investigated materials. Fading or the complete disappearance of radical signals in the EPR spectra after immersion in both media was accompanied by the disappearance of other phases formed as a minor byproduct in the synthesis of substituted HAP, as confirmed by PXRD and FTIR analysis. Obtained results confirm the great potential of Mg-HAPs for biomedical applications, although closer attention should be given to the processes related to sample storage stability at different temperatures.

Influence of magnesium and strontium substitutions in the structure of hydroxyapatite lattice on the deposition rate and properties of the CaP coatings formed via RF-sputtering of the powder targets

This work is dedicated to studying of the properties of the calcium phosphate (CaP) coatings deposited on Ti substrates by radio-frequency magnetron sputtering (RFMS) of three hydroxyapatite-based powder targets: pure hydroxyapatite (HA), Mg-substituted HA (Mg-HA, Mg = 0.93 ± 0.13 at.%) and Sr-substituted HA (Sr-HA, Sr ∼ 0.47 at.%). The influence of ionic substitutions in the structure of the sputtered targets on the surface morphology, physicochemical properties of the coatings and their wettability were studied. It is revealed that Mg and Sr ionic substitutions in the crystal lattice of HA at these concentrations don’t affect deposition rate, however, it influences morphology, wettability and elemental and phase composition of deposited coatings.

Porous CaP Coatings Formed by Combination of Plasma Electrolytic Oxidation and RF-Magnetron Sputtering

The porous CaP subcoating was formed on the Ti6Al4V titanium alloy substrate by plasma electrolytic oxidation (PEO). Then, upper coatings were formed by radio frequency magnetron sputtering (RFMS) over the PEO subcoating by the sputtering of various CaP powder targets: β-tricalcium phosphate (β-TCP), hydroxyapatite (HA), Mg-substituted β-tricalcium phosphate (Mg-β-TCP) and Mg-substituted hydroxyapatite (Mg-HA), Sr-substituted β-tricalcium phosphate (Sr-β-TCP) and Sr-substituted hydroxyapatite (Sr-HA). The coating surface morphology was studied by scanning electron and atomic force microscopy. The chemical composition was determined by X-ray photoelectron spectroscopy. The phase composition of the coatings was studied by X-ray diffraction analysis. The Young’s modulus of the coatings was studied by nanoindentation test. RF-magnetron sputtering treatment of PEO subcoating resulted in multileveled roughness, increased Ca/P ratio and Young’s modulus and enrichment with Sr and Mg. Sputtering of the upper layer also helped to adjust the coating crystallinity.

Halloysite Nanotube-Reinforced Ion-Incorporated Hydroxyapatite-Chitosan Composite Coating on Ti-6Al-4 V Alloy for Implant Application

To develop the corrosion resistance and improve the biological performance of a titanium implant (Ti6Al4V alloy), a series of mineral (M = Zn and Mg)-substituted hydroxyapatite (MHA), chitosan-MHA (CS-MHA), halloysite nanotube-MHA (HNT-MHA), and HNT-CS-MHA composite coatings were fabricated on the anodized titanium alloy by electrodeposition. The surface morphology and cross section of various coated composites were investigated by high-resolution scanning electron microscopy (HR-SEM). Furthermore, the functional groups and phase structure of the composite coatings were investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometry (XRD). Corrosion behaviors of the composite coatings were also investigated by polarization and impedance spectroscopy (EIS). Moreover, the cell-material interaction of the composite coating was observedin vitrowith human osteoblast MG63 cells for cell proliferation at 1, 4, and 7 days of incubation. Consequently, HNT-CS-MHA-Ti may have potential applications in the field of orthopedic and dental implants.

Electroactive Mg2+-Hydroxyapatite Nanostructured Networks against Drug-Resistant Bone Infection Strains.

Surface colonization competition between bacteria and host cells is one of the critical factors involved in tissue/implant integration. Current biomaterials are evaluated for their ability both of withstanding favorable responses of host tissue cells and of resisting bacterial contamination. In this work, the antibacterial ability of biocompatible Mg2+-substituted nanostructured hydroxyapatite (HA) was investigated. The densities of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli strains were significantly decreased after culture in the presence of Mg-substituted HA materials in direct correlation with Mg2+-Ca2+ switch in the HA lattice. It was noticed that this decrease was accompanied by a minimal alteration of bacterial environments; therefore, the Mg2+-HA antibacterial effect was associated with the material surface topography and it electroactive behavior. It was observed that 2.23 wt % Mg2+-HA samples exhibited the best antibacterial performance; it decreased 2-fold the initial population of E. coli, P. aeruginosa, and S. aureus at the intermediate concentration (50 mg mL-1 of broth). Our results reinforce the potential of Mg-HA nanostructured materials to be used in antibacterial coatings for implantable devices and/or medicinal materials to prevent bone infection and to promote wound healing.

Comparative study of surface properties of Mg-substituted hydroxyapatite bioceramic microspheres

Mg-substituted hydroxyapatite (HAp) bioceramic microspheres were prepared by spray drying and subsequent processing at 1173, 1273 and 1373K. Influence of various Mg substitution levels (up to 0.84±0.10wt%) on physicochemical properties of the HAp bioceramic microspheres was evaluated. Obtained results were used for the elucidation of the compositional and structural characteristics of the microspheres in conjunction with adsorption of protein, namely, bovine serum albumin (BSA). The primary difference among the microspheres processed at various temperature was the presence or absence of the micropores (<2nm in diameter) and mesopores (between 2 and 50nm). Presence of the micro- and mesopores resulted in higher specific surface area (SSA), enhanced solubility, i.e., ion release, and, accordingly, increase in the amount of BSA adsorbed on the microspheres. Furthermore, the BSA adsorption capacity of the microspheres decreased with increasing Mg content despite of higher SSA.

Magnesium substituted hydroxyapatite whiskers: synthesis, characterization and bioactivity evaluation

Magnesium (Mg) substituted hydroxyapatite (Mg-HAp) whiskers were hydrothermally synthesized using acetamide as a homogeneous precipitation reagent.

Effect of mechanical alloying on the phase evolution, microstructure and bio-corrosion properties of a Mg/HA/TiO2/MgO nanocomposite

In this study, a magnesium-matrix nanocomposite comprising bioactive ceramics of Mg-substituted hydroxyapatite (HA), farringtonite (Mg3(PO4)2), perovskite (CaTiO3), geikielite (MgTiO3) and brucite (Mg(OH)2) was synthesised through mechanical alloying and annealing of a Mg–HA–TiO2–MgO mixture by mechanically induced self-propagating reactions. The phase evolution and microstructure were analysed using X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. The results indicated that after 16h of milling, the powder mixture exhibited a homogenous distribution of fine agglomerates composed of spherical particles with an average size of 83nm. The crystallinity and thermal stability of the HA phase decreased with increasing milling time because of the substitution of Mg atoms in the HA structure. The mean crystallite size of the product phases was approximately 75nm after 8h of mechanical alloying, and these values increased slightly to 82 and 88nm after 1h of annealing at 500 and 630°C, respectively. The bio-corrosion properties of the nanocomposites were investigated using electrochemical tests and immersion tests after different milling times and subsequent annealing. The electrochemical tests revealed that the corrosion potential (Ecorr) of the as-blended samples shifted towards a nobler direction from −1565 to −1457mVSCE by increasing the amount of HA from 12.5wt% to 25wt%. After 16h of milling, the corrosion resistance of the milled samples comprising 12.5wt% and 25wt% HA increased to 4.63 and 4.97kΩcm2, respectively. The milled samples annealed at 630°C exhibited lower corrosion rates compared with those annealed at 500°C. The present study suggests that the high-energy ball milling of the Mg–HA–TiO2–MgO mixture accompanied with post annealing is a promising option for controlling the rapid corrosion rate.

Effect of different synthesis conditions on the microstructure, crystallinity and solubility of Mg-substituted hydroxyapatite nanopowder

A series of the Mg-substituted nano-hydroxyapatite (Mg-n-HA) nanopowders were synthesized by chemical co-precipitation method under different conditions, including two reaction temperature of 70°C and 40°C, and two water-soluble macromolecules of carboxyl methyl cellulose and poly(acrylic acid). The influence of magnesium content, reaction temperature and macromolecules on the microstructure, crystallinity and solubility of Mg-n-HA were characterized using SEM, XRD, FTIR techniques and soaking in simulated body fluid (SBF) solution. The results showed that needle-like Mg-n-HA nanoparticle with Mg being successfully incorporated in HA lattice could be synthesized, and there was no obvious morphology difference among the Mg-n-HA nanoparticles synthesized under different conditions. However, the crystallite sizes, cell parameters and crystallinity evidently decreased with the increasing magnesium content, the lowering reaction temperature and the introducing of macromolecules. Moreover, the solubility in SBF soaking was greatly improved in comparison with n-HA due to their lower crystallinity.

The Study of Magnesium Substitution Effect on Physicochemical Properties of Hydroxyapatite

In the present study, pure and Mg-substituted hydroxyapatite powders made up of needle-like and plate-like particles, respectively, have been synthesized by wet chemical precipitation of CaO, MgO and H3PO4. The influence of different amounts of MgO addition into synthesis media on properties of as-synthesized and sintered powders has been evaluated. Through the phase and chemical composition analysis it has been determined that the prepared powders contain various amounts of Mg (in the range between 0.21–4.72 wt%). The substitution of Mg promoted the decomposition of hydroxyapatite to β-tricalcium phosphate.

Characterization of Mg-substituted hydroxyapatite synthesized by wet chemical method

Mg-substituted hydroxyapatite made up of needle-like and plate-like particles containing different amounts of Mg (between 0.21wt% and 2.11wt%) were prepared via wet chemical precipitation method of a homogenous suspension of Mg(OH)2/Ca(OH)2 and an aqueous solution of H3PO4. According to the data of Brunauer–Emmett–Teller method and field emission scanning electron microscopy, high specific surface area Mg-substituted hydroxyapatite was obtained. Specific surface area of as-synthesized powders increased from 94.9m2g−1 to 104.3m2g−1 with increasing concentration of Mg up to 0.64wt%. Fourier transform infrared spectroscopy, X-ray powder diffraction, differential thermal analysis, and heating microscopy, were used to evaluate thermal stability and sintering behavior of synthesis products. Increase in concentration of Mg in synthesis products (≥0.83wt%) promoted decomposition of Mg-substituted hydroxyapatite to Mg-substituted β-tricalcium phosphate after thermal treatment.

Synthesis of Mg-substituted hydroxyapatite nanopowders: Effect of two different magnesium sources

Two different magnesium sources of magnesium nitrate and magnesium stearate were used to synthesize Mg-substituted hydroxyapatite (Mg-n-HA) nanoparticles by a co-precipitation method. The obtained produces were characterized using SEM, FTIR, XRD and TEM. It was revealed that two magnesium ions were both incorporated successfully in HA lattice by partially replacing calcium ion, noted as Mg-n-HA-1 and Mg-n-HA-2, respectively. There was no obvious difference of needle-like morphology, nanoparticles size and thermal stability among n-HA, Mg-n-HA-1 and Mg-n-HA-2. However, crystallinity in Mg-n-HA-2 was remarkably decreased. More importantly, the dispersibility of Mg-n-HA-2 in dichloromethane was greatly improved, as comparing to Mg-n-HA-1 and n-HA. The above results demonstrated that magnesium stearate was a better magnesium source to obtain Mg-n-HA than magnesium nitrate, which could effectively reduce the powder crystallinity and prevent the aggregation of Mg-n-HA nanoparticles resulting from the introduction of organic magnesium source.

Influence of Magnesium Ion Substitution on Structural and Thermal Behavior of Nanodimensional Hydroxyapatite

Hydroxyapatite (HA), incorporating small amount of magnesium, shows attractive biological performance in terms of improved bone metabolism, osteoblast and osteoclast activity, and bone in-growth. This article reports a systematic investigation on the influence of magnesium (Mg) substitution on structural and thermal behavior of nanodimensional HA. HA and Mg-substituted HA nanopowders were synthesized through sol-gel route. The morphology and size of nanopowders were characterized by transmission electron microscopy. The BET surface area was evaluated from N2 adsorption isotherms. Structural analysis and thermal behavior were investigated by means of Fourier transform infrared spectroscopy, x-ray diffraction, thermogravimetry, and differential thermal analysis. As-synthesized powders consisted of flake-like agglomerates of HA and calcium-deficient HA. The incorporation of magnesium in HA resulted in decrease of crystallite size, crystallinity, and lattice parameters a and c and increase in BET surface area. β-tricalcium phosphate formation occured at lower calcination temperature in Mg-substituted HA than HA.

Synthesis of Mg&lt;sup&gt;2+&lt;/sup&gt; Incorporated Hydroxyapatite by Ion Implantation

Mg substituted hydroxyapatite (Mg-HA) has been reported to promote activity of osteoblast and inhibit function of osteoclast in vitro. Mg-HA was synthesized by ion implantation of Ca2+, P2+ and Mg2+ beams by using an electrostatic medium energy accelerator. Oxygen injection had a major role in the formation of HA on Ti substrate. The osteoblast cells spread and formed lamellae on the coating surfaces. But Mg2+ ion implanted HA had shown higher osteoblast cell count and higher protein activity. The presence of Mg in the coating had better osteoblast activity and differentiation. Implantation of Ca and P ions into Ti substrate to successfully form HA and subsequent Mg ion incorporation in this layer shows that medium energy ions are very helpful in increasing the tensile strengths drastically.

Incorporation of Magnesium Ions into Synthetic Hydroxyapatite: Synthesis and Characterization

The objective of this work is to synthesize pure and Mg-substituted hydroxyapatite (HAp) powders with different MgO content in synthesis media (in the wide range of 0.1-10.0 wt% in respect to Ca), and to study the influence of Mg2+ ions substitution on the physicochemical properties of HAp materials. In this work HAp and magnesium-substituted hydroxyapatite (Mg-HAp) were synthesized by modified wet chemical precipitation of homogenous suspension of Mg(OH)2/Ca(OH)2 and H3PO4 solution. Systematic investigation on as-synthesized and sintered Mg-HAp and HAp samples shows that the incorporation of MgO promotes decomposition of HAp to β-tricalcium phosphate (β-TCP) and significantly modified its microstructure. The effect and evidence of incorporation of Mg2+ ions into HAp structure is discussed.

25Mg Solid-State NMR of Magnesium Phosphates: High Magnetic Field Experiments and Density Functional Theory Calculations

Natural-abundance 25Mg solid-state NMR data obtained using very high magnetic fields of 17.6, 20.0, and 30.0 T are reported for a series of magnesium phosphate compounds, some of which are of potential biomedical interest. The 25Mg NMR parameters have been calculated by using the DFT PAW and GIPAW methods, for both the experimental and DFT atomic position optimized structures. For most of the studied compounds, the geometry optimization step improves significantly the accuracy of the calculations and good correlations between experimental and calculated 25Mg chemical shifts and quadrupolar coupling constants were achieved showing that this approach can be used to obtain unambiguous assignments of the 25Mg resonances in more complex phosphate compounds. The possibility of recording natural abundance 25Mg NMR spectra in materials with very low Mg content is illustrated for a ∼10% Mg-substituted hydroxyapatite sample. In this case, the distribution of 25Mg quadrupolar coupling measured experimentally has bee...