Magnesium-substituted Hydroxyapatite Research Articles

Mechano-synthesized wollastonite-forsterite composite coatings on the plasma electrolytic oxidized Ti-6Al-4V alloy for dental implant

This study investigated an innovative approach for dental implant coatings by developing mechano-synthesized wollastonite-forsterite composite coatings (MC) on plasma electrolytic oxidized (PEO) Ti-6Al-4V alloy. The process involved PEO treatment using a pulsed DC power supply in an electrolyte solution of mono-calcium acetate and calcium glycerophosphate, followed by MC with mixed wollastonite (CaSiO3) and forsterite (Mg2SiO4) powders. After MC treatment, FESEM, EDS analysis, cross-section, XPS, Raman analysis, corrosion test, and an in vitro test for biocompatibility were performed. Comprehensive surface characterization revealed that wollastonite particles transformed into smaller needle-like shapes, while forsterite particles became slightly less uniform but retained their spherical shape. Higher wollastonite content resulted in greater pore filling with fine particles, whereas increased forsterite content led to fewer fine particles on the surface. Cross-sectional analysis showed Si concentration inside the pores. Notably, wollastonite-rich samples exhibited superior corrosion resistance and rapid initial apatite formation in simulated body fluid (SBF) studies. In contrast, forsterite-containing samples demonstrated more controlled and sustained bioactivity, forming magnesium-substituted hydroxyapatite over time. The novelty of this work lies in combining the bioactive properties of wollastonite and forsterite with enhanced PEO surface characteristics, resulting in coatings with tailored corrosion resistance and bioactivity profiles suitable for dental implant applications.

Effects of Sr and Mg doping on elastic, mechanical, and optical properties of hydroxyapatite: A first-principles study

Hydroxyapatite (HAp), with the chemical formula Ca10(PO4)6(OH)2, is a bioactive ceramic material typically used in the treatment of bone defects owing to the excellent biocompatibility and the ability to bond with bone tissues. Mechanical properties of HAp have drawn pronounced attention because of the crucial roles in the medical applications. Based on density functional theory (DFT), this work reports the structural, formation energy, mechanical, Vickers hardness, electronic properties, and optical properties of hydroxyapatite (HAp), strontium-substituted HAp (Sr-HAp), and magnesium-substituted HAp (Mg-HAp). The results reveal that the Sr2+ and Mg2+ ions mainly replace the Ca2+ ion at the Ca-1 site in HAp. Resistance to hydrostatic compression followed the order Mg-HAp > HAp > Sr-HAp. Sr-HAp has the capability to enhance thermal shock resistance and lattice thermal conductivity. In addition, the electronic properties of HAp change upon substitutional Sr2+ and Mg2+ doping. In comparison with pristine HAp, the energy gap of Sr-doped HAp relatively increases, whereas that of Mg-doped HAp decreases. Nevertheless, both Sr-HAp and Mg-HAp remain insulators. Intriguingly, Sr-HAp possesses the improved hardness by 11.31 % owing to the hybridization of the Sr (4p) and O (2p) states, which contributed to its high shear modulus and high hardness. Beyond that, we further investigate their optical properties. The presence of Mg states at approximately 10 eV in the conduction band leads to enhanced absorption within the 14 – 20 eV for Mg-doped HAp. Similarly, the presence of a deep Sr(4p) level in Sr-HAp amplifies absorption within the 20–25 eV range. These findings have raised a potential avenue for selectively boosting the optical absorption of HAp, thus improving its photocatalytic properties.

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.

FTIR study on the phase transition of experimental and archaeological burnt ivory

Recent excavation of the elephant ivories at the Sanxingdui site of the Shang Dynasty in Sichuan, China brings attention to the burnt features of the ivories. However, burnt ivories cannot be assessed by the same criteria established for burnt bones because of the differences in the ways that the two materials respond to heat. This study examines differences in the phase transition characteristics of ivory and bone, and confirms that the threshold temperature of the alteration in ivories is lower than that in bones. In our analysis, elephant ivories and bovine bones burnt at the temperatures between 200 and 1000 °C in oxidizing or reducing atmosphere are prepared and comparatively investigated by attenuated total reflection Fourier transform infrared spectroscopy. The results show that the transformation from magnesium-substituted hydroxyapatite (Mg-HAp) to magnesium-substituted β-tricalcium phosphate in ivory dentin takes place at the temperature as low as 800 °C, while β-tricalcium phosphate is not observed in bovine bones burnt at 1000 °C or below mainly because of the different magnesium contents. Due to the destruction of Mg-HAp at 800 °C in ivories, cyanamidapatite that could form in bones burnt under reducing atmosphere is absent in burnt ivories. With reference to the experimental burnt ivories, archaeological burnt ivories from the Sanxingdui site can now be clearly determined to be burnt unevenly at temperatures up to around 800 °C. This study may provide further information for archaeological research on ivories from the Sanxingdui site and identification of burnt bioapatite materials in other archaeological findings.

Synthesis and Properties of Polymer Composites Based on Magnesium-Substituted Hydroxyapatite

Synthesis and Properties of Polymer Composites Based on Magnesium-Substituted Hydroxyapatite

Localized corrosion of magnesium alloys potentially applicable for medical implants: fundamental aspects

A comparative analysis of the corrosion activity of bioresorbable MA8 magnesium alloy (Mg– Mn – Ce system) in a medium for cultivation of mammalian cells (minimum essential medium, MEM) and 0.83 wt. % aqueous NaCl solution was performed. The development of the corrosion process on the surface of a magnesium alloy in two media was established using local scanning electrochemical methods (scanning vibrating electrode technique and scanning ion-selective electrode technique), traditional electrochemical methods (potentiodynamic polarization, electrochemical impedance spectroscopy) and hydrogen evolution measurements. The protective properties of the corrosion film formed on the alloy in MEM, as well as during exposure to NaCl solution, were established. The composition of the layer of corrosion products formed on the magnesium alloy in MEM was studied using confocal Raman spectroscopy, X-ray diffraction analysis, scanning electron microscopy, and energy dispersive X-Ray analysis. Calcium-phosphate compounds are the main products formed on the surface of a magnesium alloy during immersion in MEM. The model of corrosion mechanism of magnesium alloy in MEM, which includes three stages of the development of surface film, is proposed. The formation on the magnesium alloy in MEM of corrosion product layer, including magnesium-substituted hydroxyapatite, stabilizes the local pH below 9.0, which along with the presence of organic acids, does not allow increasing the pH during corrosion. A diagram that allows one to determine the possible reactions occurring on the surface of a magnesium alloy in MEM and the thermodynamic probability of the formation of chemical compounds based on the values of the local pH is designed. The obtained results indicate the prospect of using bioresorbable magnesium implants in surgery.

Investigation into Effect of Natural Shellac on the Bonding Strength of Magnesium Substituted Hydroxyapatite Coatings Developed on Ti6Al4V Substrates

The bioactive and biocompatible properties of hydroxyapatite (HA) promote the osseointegration process. To enhance other bio-functions of HA such as improving the antibacterial property of the implant, increasing the rate of cell proliferation, or improving tissue generation capability, HA is substituted with many elements such as Zn, Cl, Ba, Fe, Cu, Ag, Sr, F, Na, etc. This study reports development of Magnesium substituted HA (Mg-HA) coatings on Ti6Al4V substrates using the dip coating technique. To improve the adhesion and stability of the coating, an intermediate layer of shellac was applied between the coating and Ti6Al4V substrate. The dip coating process parameters were optimized using the Taguchi technique and it was found that dipping time of 35 s and 13% w/w of shellac concentration provided the maximum bonding strength of 12.5 MPa. The biocompatibility, dissolution, and corrosion study of the developed coating using the optimal parameters obtained were carried out in this study. An improvement in cell growth and cell proliferation was observed in the extract medium prepared from coated substrates. Release of Ca, P and Mg ions from the surface of the coated substrate into the simulated body fluid (SBF) was found to be almost constant which shows the stability of the thin film coating formed. The Mg-HA coated substrate also exhibited better corrosion resistance than the uncoated substrate.

Biological behavior of magnesium-substituted hydroxyapatite during bone repair.

The aim of this study was to analyze the biological behavior and osteogenic potential of magnesium (Mg) substituted hydroxyapatite (HA) microspheres, implanted in a critical bone defect, considering that this ion is of great clinical interest, since it is closely associated with homeostasis and bone mineralization. For the purpose of this study, 30 rats were used to compose three experimental groups: GI - bone defect filled with HA microspheres; GII - bone defect filled with HA microspheres replaced with Mg; GIII - empty bone defect; evaluated at biological points of 15 and 45 days. The histological results, at 15 days, showed, in all the groups, a discrete chronic inflammatory infiltrate; biomaterials intact and surrounded by connective tissue; and bone neoformation restricted to the borders. At 45 days, in the GI and GII groups, an inflammatory response of discrete granulomatous chronic type was observed, and in the GIII there was a scarce presence of mononuclear inflammatory cells; in GI and GII, the microspheres were seen to be either intact or fragmented, surrounded by fibrous connective tissue rich in blood vessels; and discrete bone neoformation near the edges and surrounding some microspheres. In GIII, the mineralization was limited to the borders and the remaining area was filled by fibrous connective tissue. It was concluded that the biomaterials were biocompatible and osteoconductive, and the percentage of Mg used as replacement ion in the HA did not favor a greater bone neoformation in relation to the HA without the metal.

Preparation of HAp whiskers with or without Mg ions and their effects on the mechanical properties and osteogenic activity of poly(d,l-lactide)

Hydroxyapatite whiskers (HAp-Ws) and magnesium-substituted hydroxyapatite whiskers (Mg-HAp-Ws) with 1, 3, and 5 mol% magnesium (Mg) ion substitution contents were successfully prepared by the hydrothermal method. The incorporation of Mg ion into the HAp-Ws led to a morphology including a combination of whiskers and particles and a decrease in the crystal interplanar spacing. Then, the HAp-Ws and Mg-HAp-Ws were further introduced into a poly(d,l-lactide) (PDLLA) matrix to prepare HAp-Ws/PDLLA and Mg-HAp-Ws/PDLLA composite films. The existence of HAp-Ws or Mg-HAp-Ws can endow composite films with superior hydrophilicity and tensile properties. Moreover, since the HAp-Ws have a good morphology and a large aspect ratio, the tensile strength and modulus of the HAp-Ws/PDLLA composite film were reasonably higher than those of the Mg-HAp-Ws/PDLLA composite film. The Mg-HAp-Ws/PDLLA composite films were more beneficial for MC3T3-E1 cell adhesion, proliferation and differentiation due to the presence of Mg ions. More importantly, the osteogenic effect of Mg ions on MC3T3-E1 cells is dose-dependent, and the Mg-HAp-Ws/PDLLA composite films with 1–3 mol% Mg ion contents in the Mg-HAp-Ws showed relatively good cytocompatibility and osteogenic activity. In short, the mechanical properties and osteogenic activity of Mg-HAp-Ws/PDLLA composite films can be regulated by adjusting the Mg/Ca content to better meet the needs of bone repair.

Localized currents and pH distribution studied during corrosion of MA8 Mg alloy in the cell culture medium

Electrochemical behaviour of MA8 magnesium alloy in minimum essential medium (MEM) and 0.83 wt. % NaCl solution is compared using SVET, local pH measurements and hydrogen evolution tests. Corrosion products formed on the alloy surfaces are characterized using XRD and SEM-EDX analysis. Potential by-products of cells and bacteria activities increase the sample activity in MEM at the initial stage of material immersion. Hydrogen evolution rate is higher for samples in NaCl solution in comparison with MEM. Formation of partially protective magnesium-substituted hydroxyapatite stabilizes the local pH of MEM below 9.0 and does not allow to increase the pH during corrosion.

Breast-Specific Gamma Imaging with [99mTc]Tc-Sestamibi: An In Vivo Analysis for Early Identification of Breast Cancer Lesions Expressing Bone Biomarkers.

The main purpose of this pilot investigation was to evaluate the possible relationship among [99mTc]Tc-Sestamibi uptake, the presence of breast osteoblast-like cells, and the expression of molecules involved in bone metabolism, such as estrogen receptor, bone morphogenetic proteins-2, and PTX3. To this end, forty consecutive breast cancer patients who underwent both breast-specific gamma imaging with [99mTc]Tc-Sestamibi and breast bioptic procedure were retrospectively enrolled. From each diagnostic paraffin block collected in the study, histological diagnosis, immunohistochemical investigations, and energy dispersive X-ray microanalysis were performed. Our data highlight the possible use of breast-specific gamma imaging with [99mTc]Tc-Sestamibi for the early detection of breast cancer lesions expressing bone biomarkers in the presence of breast osteoblast-like cells. Specifically, we show a linear association among sestamibi uptake, the presence of breast osteoblast-like cells, and the expression of estrogen receptor, bone morphogenetics proteins-2, and PTX3. Notably, we also observed an increase of [99mTc]Tc-Sestamibi in breast cancer lesions with magnesium-substituted hydroxyapatite. In conclusion, in this pilot study we evaluated data from the nuclear medicine unit and anatomic pathology department on breast cancer osteotropism, identifying a new possible interpretation of Breast Specific Gamma Imaging with [99mTc]Tc-Sestamibi analysis.

Исследование свойств биокомпозитных плазменных покрытий «титан-магнийзамещенные кальцийфосфаты»

Complex investigations of the physicochemical properties of coatings obtained by plasma spraying of magnesium-substituted hydroxyapatite and tricalcium phosphate powders on a titanium base are carried out, and their comparative characteristics are given. Infrared spectroscopy and X-ray phase analysis of substituted powders confirmed their structure. According to transmission electron microscopy, the powder particles of magnesium-substituted hydroxyapatite have an elongated rectangular shape, flat edges, the size of individual particles from 500 nm to 2-3 μm. The magnesium-substituted tricalcium phosphate powder is represented by particles ranging in size from 300 nm to 7 μm, nanometer-scale particles are cylinders, whereas the shape of larger particles is close to rectangular. Scanning electron microscopy of plasma-dust coatings shows that a coating based on magnesium-substituted tricalcium phosphate, unlike magnesium-substituted hydroxyapatite, is formed by smaller particles with clear boundaries, resulting in a more uniform microrelief, but in turn a coating based on magnesium-substituted hydroxyapatite contains more micro- and nano-formations . The maximum force at which the samples with the plasma-dust coating on the basis of magnesium-substituted hydroxyapatite were taken off was 5.4 kN, and the magnesium-substituted tricalcium phosphate was 5 kN. The calculated adhesion values for coatings are 14.9 and 13 MPa, respectively. The coatings under investigation are characterized by pronounced hydrophilic properties. The surface energy for both types of coating is determined primarily by the polar component, and not by the dispersion component, which indicates the presence of polar groups on the surface.

Magnesium incorporated hydroxyapatite nanoparticles: Preparation, characterization, antibacterial and larvicidal activity

Mosquito-borne diseases cause several deaths every year in tropical and subtropical climate countries. Control of vectors is an alarming problem in today’s world due to the resistance matters. In this study magnesium incorporated hydroxyapatite nanoparticles have been synthesized by microwave irradiation method. Magnesium chloride hexahydrate (MgCl2·6H2O) calcium nitrate tetra hydrate (Ca (NO3)2·6H2O) and disodium hydrogen phosphate (Na2HPO4) were used as magnesium, calcium and phosphorous sources to prepare hydroxyapatite nanoparticles. The FT-IR studies show the presence of hydroxyl and phosphate functional groups. The structural properties have been studied using X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and Transmission Electron Microscope (HRTEM). The energy dispersive X-ray analysis (EDAX) revealed the presence of Ca, Mg, P and O in the prepared samples. The antibacterial activity of the as-synthesized nanoparticles was evaluated against two prokaryotic strains, the gram negative bacteria Escherichia coli for three different concentrations of as-synthesized nanoparticles and they showed excellent antibacterial activity. The as-synthesized Mg-HAp nanoparticles were tested against fourth instar larvae of Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus and the nanoparticles exhibited significant mortality against the selected mosquitoes. The observed results suggest that the magnesium incorporated hydroxyapatite nanoparticles have the potential to be used as an effective mosquito larvae control agent against Ae. aegypti, An. stephensi, and Cx. quinquefasciatus. From the detailed literature review it has been observed that no work has been carried out so far on the larvicidal activity using hydroxyapatite (HAp) nanoparticles and magnesium substituted hydroxyapatite (Mg-HAp) nanoparticles.

Facilitated receptor-recognition and enhanced bioactivity of bone morphogenetic protein-2 on magnesium-substituted hydroxyapatite surface.

Biomaterial surface functionalized with bone morphogenetic protein-2 (BMP-2) is a promising approach to fabricating successful orthopedic implants/scaffolds. However, the bioactivity of BMP-2 on material surfaces is still far from satisfactory and the mechanism of related protein-surface interaction remains elusive. Based on the most widely used bone-implants/scaffolds material, hydroxyapatite (HAP), we developed a matrix of magnesium-substituted HAP (Mg-HAP, 2.2 at% substitution) to address these issues. Further, we investigated the adsorption dynamics, BMPRs-recruitment, and bioactivity of recombinant human BMP-2 (rhBMP-2) on the HAP and Mg-HAP surfaces. To elucidate the mechanism, molecular dynamic simulations were performed to calculate the preferred orientations, conformation changes, and cysteine-knot stabilities of adsorbed BMP-2 molecules. The results showed that rhBMP-2 on the Mg-HAP surface exhibited greater bioactivity, evidenced by more facilitated BMPRs-recognition and higher ALP activity than on the HAP surface. Moreover, molecular simulations indicated that BMP-2 favoured distinct side-on orientations on the HAP and Mg-HAP surfaces. Intriguingly, BMP-2 on the Mg-HAP surface largely preserved the active protein structure evidenced by more stable cysteine-knots than on the HAP surface. These findings explicitly clarify the mechanism of BMP-2-HAP/Mg-HAP interactions and highlight the promising application of Mg-HAP/BMP-2 matrixes in bone regeneration implants/scaffolds.

Rod-shaped and substituted hydroxyapatite nanoparticles stimulating type 1 and 2 cytokine secretion

A Th1 immune response is required for modern vaccines as the most commonly used alum adjuvant has weak capacity for inducing Th1 immune response. Herein, rod-shaped hydroxyapatite (HA), magnesium-substituted HA (MgHA) and zinc-substituted HA (ZnHA) nanoparticles with irregular nanopores were synthesized and used as immunoadjuvants. Magnesium and zinc substitution in HA showed no influence on morphology, particle size, zeta potential and surface area of the nanoparticles. The rod-shaped MgHA and ZnHA nanoparticles promoted the cellular uptake of a molecular immunopotentiator, stimulated both type 1 and 2 cytokine secretion in vitro that relate to Th1 and Th2 immunity of bone marrow dentritic cells, respectively. The MgHA and ZnHA nanoparticles may be useful as immunoadjuvants for human.

Properties of magnesium-substituted hydroxyapatite and the plasma coatings based on it

Magnesium-substituted hydroxyapatite is synthesized and deposited by plasma spraying, and the coating and the products of hydroxyapatite decomposition are analyzed. The phase composition of magnesium- substituted hydroxyapatite deposited by plasma spraying undergoes changes. The coating consisting of molten magnesium-substituted hydroxyapatite powder particles with pores between them has a homogeneous structure over the surface and throughout the internal structure and adhesion characteristics that exceed those of hydroxyapatite coatings.

Dip Coated Magnesium-Substituted Hydroxyapatite Coatings on Magnesium Alloy for Biomedical Applications

Magnesium-substituted hydroxyapatite coatings have been deposited on magnesium alloy for biomedical applications by sol–gel technology. The Ca(10−x)Mgx(PO4)6(OH)2coatings obtained, with magnesium contents up to x = 1.5, show dense and compact and with visible cracks. The results of Hydrogen (H2) evolution testing in Hank’s solution show that magnesium-substituted hydroxyapatite coatings can improve the corrosion resistance of magnesium alloy.

Osteoblast cell proliferation on magnesium-substituted hydroxyapatite (Mg-HA) coatings

Osteoblast cell proliferation on magnesium-substituted hydroxyapatite (Mg-HA) coatings

Microcalcifications in breast cancer: an active phenomenon mediated by epithelial cells with mesenchymal characteristics.

BackgroundMammary microcalcifications have a crucial role in breast cancer detection, but the processes that induce their formation are unknown. Moreover, recent studies have described the occurrence of the epithelial–mesenchymal transition (EMT) in breast cancer, but its role is not defined. In this study, we hypothesized that epithelial cells acquire mesenchymal characteristics and become capable of producing breast microcalcifications.MethodsBreast sample biopsies with microcalcifications underwent energy dispersive X-ray microanalysis to better define the elemental composition of the microcalcifications. Breast sample biopsies without microcalcifications were used as controls. The ultrastructural phenotype of breast cells near to calcium deposits was also investigated to verify EMT in relation to breast microcalcifications. The mesenchymal phenotype and tissue mineralization were studied by immunostaining for vimentin, BMP-2, β2-microglobulin, β-catenin and osteopontin (OPN).ResultsThe complex formation of calcium hydroxyapatite was strictly associated with malignant lesions whereas calcium-oxalate is mainly reported in benign lesions. Notably, for the first time, we observed the presence of magnesium-substituted hydroxyapatite, which was frequently noted in breast cancer but never found in benign lesions. Morphological studies demonstrated that epithelial cells with mesenchymal characteristics were significantly increased in infiltrating carcinomas with microcalcifications and in cells with ultrastructural features typical of osteoblasts close to microcalcifications. These data were strengthened by the rate of cells expressing molecules typically involved during physiological mineralization (i.e. BMP-2, OPN) that discriminated infiltrating carcinomas with microcalcifications from those without microcalcifications.ConclusionsWe found significant differences in the elemental composition of calcifications between benign and malignant lesions. Observations of cell phenotype led us to hypothesize that under specific stimuli, mammary cells, which despite retaining a minimal epithelial phenotype (confirmed by cytokeratin expression), may acquire some mesenchymal characteristics transforming themselves into cells with an osteoblast-like phenotype, and are able to contribute to the production of breast microcalcifications.

501 スパッタリング法によるマグネシウム置換HA薄膜の作製とマグネシウム置換量の評価(OS5-(1),OS5 オーガナイズドセッション《ライフサポートにおける工学技術》)

Magnesium substituted hydroxyapatite (Mg-HA) thin films were prepared using rf-magnetron sputtering method. The Mg-HA films were coated onto a titanium (Ti) substrate from a mixed HA/MgO powder target. The molar ratio of Mg to Ca in the mixture target was varied in the ratio of 0:10, 2:8, 4:6, 6:4 and 8:2. The Mg-HA films were heated or subjected to hydrothermal treatment. The chemical compositions of the Mg-HA films were determined by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The crystal lattice parameters from XRD patterns of Mg-HA films were calculated. The chemical analysis by XPS showed that the non-heated, heated, subjected to hydrothermal treatment Mg-HA films contained Mg. The XRD patterns showed that the heated Mg-HA films composed of HA, beta-tricalcium phosphate (β-TCP) and MgO. The subjected to hydrothermal treatment Mg-HA films composed of HA and MgO. The lattice parameters of the HA in the heated and subjected to hydrothermal treatment Mg-HA films (Mg:Ca=2:8, 4:6, 6:4, 8:2) were smaller than that in the heated and subjected to hydrothermal treatment HA films (Mg:Ca=0:10).