Amorphous Magnesium Phosphate Research Articles

Enhancing osteointegration and antibacterial properties of PEEK implants via AMP/HA dual-layer coatings

Polyetheretherketone (PEEK) is a widely used engineering plastic in orthopedic and dental implants, but its bioinertness leads to poor bone integration. To overcome this, a sulfonation treatment was applied to PEEK first to create a rough, microporous surface enhancing cellular adherence and integration. Subsequently, amorphous magnesium phosphate (AMP) nanosheets were produced through microwave-assisted synthesis, and hydroxyapatite (HA) was generated using a bionic solution hydrothermal method. A dual-layer coating system composed of an interlayer AMP and a top layer HA on the surface of PEEK was developed to enhance osteointegration. Surface analysis confirms the creation of increased surface area, improved hydrophilicity with introduced hydrophilic groups, and enhanced protein attraction. In vitro assessments on mouse embryonic osteoblasts (MC3T3-E1) demonstrate the non-toxicity of these coatings and their efficacy in promoting cell proliferation. Moreover, antimicrobial evaluations against E. coli and S. aureus highlight the potential of these composite coatings in preventing implant-related infections. The AMP/HA dual-layer coating on sulfonated PEEK emerges as a potent method for enhancing osteointegration and antibacterial properties, offering a promising approach to improve bone repair efficiency in clinical applications.

Nutrient recovery from freshwater aquaculture effluent by employing seawater driven zeolite-assisted forward osmosis process

This study focused on recovering nutrients from inland freshwater aquaculture effluent which contains dilute nutrients such as ammonium (NH4+) and phosphate (PO43-) ions. Forward osmosis (FO) process with the assistance of Mg-zeolite Y was employed to recover PO43- through chemical precipitation while NH4+ recovery was achieved by regenerating the zeolite. It showed that zeolite-assisted FO process requires 56.56 ± 2.88 h to dewater 87.5% of the feed solution while standalone FO process took only 51.08 ± 2.99 h. The difference in duration was due to the supplement of Mg2+ that reduces osmotic pressure gradient. The ammonium sorption process of Mg-zeolite Y introduced Mg2+ into the feed solution and facilitated the precipitation of PO43-. Phosphate recovery from the Ca-rich solution from standalone FO process resulted in amorphous calcium phosphate (ACP) with co-precipitation of calcite and dolomite. The zeolite-assisted FO process at pH 10.5 yielded optimal results with 98.46% phosphate recovery, forming mainly amorphous magnesium phosphate (AMP). Subsequently, a two-step precipitation process was proposed to recover Mg2+ as brucite. The concentrated feed solutions from the cycles underwent the proposed two-step precipitation study, resulting in 0.507 g/L of AMP and 5.4077 g/L of brucite. An average of 88.7% NH4+ recovery with high reuse efficiency of Mg-zeolite Y using magnesium sulfate as regenerating solution could be achieved. Reusability studies showed consistent or slightly higher water flux during the dewatering process. The composition of spent regenerant was investigated, and its reuse as liquid fertilizer was feasible after dilution.

Preparation of lithium-containing magnesium phosphate-based composite ceramics having high compressive strength, osteostimulation and proangiogenic effects

Fairly high concentrations of magnesium and lithium are conducive to improving the osteogenic and angiogenic capacities. In the current study, lithium-containing magnesium phosphate-based ceramics (AMP/LMPGs) were prepared from amorphous magnesium phosphate (AMP) at a low sintering temperature (650 °C), and the lithium/magnesium-containing phosphate glasses (LMPGs) were utilized as sintering additives. During the sintering procedure of AMP/LMPGs, the AMP reacted with LMPGs, producing new compounds. The AMP/LMPGs displayed nano-size grains and plentiful micropores. The addition of LMPGs noticeably increased the porosity as well as compressive strength of the AMP/LMPGs ceramics. The AMP/LMPGs sustainedly released Mg, P and Li ions, forming Mg-rich ionic microenvironment, which ameliorated cellular proliferation, osteogenic differentiation and proangiogenic capacities. The AMP/LMPGs ceramics with considerably high compressive strength, osteostimulation and proangiogenic effects were expected to efficiently regenerate the bone defects.

Exploring the potential of magnesium oxychloride, an amorphous magnesium phosphate, and newberyite as possible bone cement candidates.

Magnesium phosphate-based bone cements, particularly struvite (MgNH4PO4∙6H2O)-forming cements, have attracted increased scientific interest in recent years because they exhibit similar biocompatibility to hydroxyapatite while degrading much more rapidly in vivo. However, other magnesium-based minerals which might be promising are, to date, little studied. Therefore, in this study, we investigated three magnesium-based bone cements: a magnesium oxychloride cement (Mg3(OH)5Cl∙4H2O), an amorphous magnesium phosphate cement based on Mg3(PO4)2, MgO, and NaH2PO4, and a newberyite cement (MgHPO4·3H2O). Because it is not sufficiently clear from the literature to what extent these cements are suitable for clinical use, all of them were characterized and optimized regarding setting time, setting temperature, compressive strength and passive degradation in phosphate-buffered saline. Because the in vitro properties of the newberyite cement were most promising, it was orthotopically implanted into a partially weight-bearing tibial bone defect in sheep. The cement exhibited excellent biocompatibility and degraded more rapidly compared to a hydroxyapatite reference cement; after 4months, 18% of the cement was degraded. We conclude that the newberyite cement was the most promising candidate of the investigated cements and has clear advantages over calcium phosphate cements, especially in terms of setting time and degradation behavior.

Simultaneous Urea and Phosphate Recovery from Synthetic Urine by Electrochemical Stabilization.

Urine is a widely available renewable source of nitrogen and phosphorous. The nitrogen in urine is present in the form of urea, which is rapidly hydrolyzed to ammonia and carbonic acid by the urease enzymes occurring in nature. In order to efficiently recover urea, the inhibition of urease must be done, usually by increasing the pH value above 11. This method, however, usually is based on external chemical dosing, limiting the sustainability of the process. In this work, the simultaneous recovery of urea and phosphorous from synthetic urine was aimed at by means of electrochemical pH modulation. Electrochemical cells were constructed and used for urea stabilization from synthetic urine by the in situ formation of OH- ions at the cathode. In addition, phosphorous precipitation with divalent cations (Ca2+, Mg2+) in the course of pH elevation was studied. Electrochemical cells equipped with commercial (Fumasep FKE) and developmental (PSEBS SU) cation exchange membranes (CEM) were used in this study to carry out urea stabilization and simultaneous P-recovery at an applied current density of 60 A m-2. The urea was successfully stabilized for a long time (more than 1 month at room temperature and nearly two months at 4 °C) at a pH of 11.5. In addition, >82% P-recovery could be achieved in the form of precipitate, which was identified as amorphous calcium magnesium phosphate (CMP) by using transmission electron microscopy (TEM).

Effect of milling on the compounding of poly-ether-ether ketone (PEEK) and amorphous magnesium phosphate (AMP) composites

Polyetheretherketone (PEEK) is a high-performance polymer; however, it is bioinert. Hence, in this study, we created a novel bioactive ceramic known as amorphous magnesium phosphate nanoparticles and incorporated it into PEEK using ball milling. We analyzed the influence of milling parameters, such as speed, duration, and the ball-to-powder ratio (BPR), on the extent of AMP mixing in PEEK. Our results indicate that 300 rpm and 2h were optimum to homogenously disperse AMP in PEEK. Interestingly, we noticed a decrease in the crystallinity of the unfilled PEEK and an increase in the crystallinity of the PEEK-AMP composite post-milling. Finally, a lower BPR such as 2:1 was apt for dispersing the AMP particles in PEEK. Overall, our study provides a comprehensive analysis of the influence of milling parameters on the mixing of the novel AMP in PEEK and determines an optimized set of milling parameters for developing bioactive PEEK-AMP composites.

Fabrication of nanocrystalline magnesium phosphate-based composite bioceramics using magnesium-containing phosphate glass as sintering additives

Magnesium-rich microenvironment is beneficial to both osteogenic and proangiogenic activities. To construct magnesium-rich microenvironment, the magnesium phosphate bioceramics could not be sintered at high temperatures, leading to low mechanical strength. In this study, magnesium phosphate-based composite (AMP/MPG) bioceramics were fabricated at low sintering temperatures (650 and 800 °C) using amorphous magnesium phosphate (AMP) and magnesium-containing phosphate glass (MPG) powders as starting materials. In the sintering of AMP/MPG, the MPG crystallized and reacted with AMP to form new phases. The AMP/MPG showed nanocrystals and pronouncedly higher compressive strength, in contrast with the bioceramics prepared from crystalline magnesium phosphate powders. The AMP/MPG continuously released high concentrations of magnesium ions, which accounted for the remarkably enhanced cell proliferation, osteogenic and angiogenic activities. The AMP/MPG bioceramics with high mechanical strength, osteostimulative and proangiogenic capacity were considered promising biomaterials to effectively regenerate the critical-size bone defects.

Effect of Oxidation Time on the Structure and Corrosion Resistance of Micro-Arc Oxidation Coating of AZ91D Magnesium Alloy in (NH4)2ZrF6 Electrolyte System

Micro-arc oxidation (MAO) coatings were obtained from an AZ91D magnesium alloy at different oxidation times (5, 10, 15, and 20 min), using a zirconium salt electrolyte system, with (NH4)2ZrF6 as the main salt. The morphology of the coatings was studied using a scanning electron microscope (SEM) and confocal laser scanning microscopy (CLSM). Energy dispersive spectrometry (EDS), X-ray diffractometry (XRD), and X-ray photoelectron spectroscopy (XPS) were employed to determine the type of element and the composition of its phase. The potentiodynamic polarization curve (PDP) was applied to illustrate the corrosion resistance of the coatings. We found the coatings had minor porosity and the best compactness when the MAO treatment time was 10 min. The coatings mainly comprised MgO, ZrO2, MgF2, and Zr3O2F8 phases and amorphous magnesium phosphate. Among the MAO coatings prepared in this experiment, the 10 min coating had the lowest corrosion current density (Icorr), and the Icorr was 4.864 × 10−8 A/cm2, which was three orders of magnitude lower than the uncoated AZ91D magnesium alloy.

Amorphous calcium magnesium phosphate nanocomposites with superior osteogenic activity for bone regeneration.

The seek of bioactive materials for promoting bone regeneration is a challenging and long-term task. Functionalization with inorganic metal ions or drug molecules is considered effective strategies to improve the bioactivity of various existing biomaterials. Herein, amorphous calcium magnesium phosphate (ACMP) nanoparticles and simvastatin (SIM)-loaded ACMP (ACMP/SIM) nanocomposites were developed via a simple co-precipitation strategy. The physiochemical property of ACMP/SIM was explored using transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD) and high-performance liquid chromatograph (HPLC), and the role of Mg2+ in the formation of ACMP/SIM was revealed using X-ray absorption near-edge structure (XANES). After that, the transformation process of ACMP/SIM in simulated body fluid (SBF) was also tracked to simulate and explore the in vivo mineralization performance of materials. We find that ACMP/SIM releases ions of Ca2+, Mg2+ and , when it is immersed in SBF at 37°C, and a phase transformation occurred during which the initially amorphous ACMP turns into self-assembled hydroxyapatite (HAP). Furthermore, ACMP/SIM displays high cytocompatibility and promotes the proliferation and osteogenic differentiation of MC3T3-E1 cells. For the in vivo studies, lamellar ACMP/SIM/Collagen scaffolds with aligned pore structures were prepared and used to repair a rat defect model in calvaria. ACMP/SIM/Collagen scaffolds show a positive effect in promoting the regeneration of calvaria defect after 12 weeks. The bioactive ACMP/SIM nanocomposites are promising as bone repair materials. Considering the facile preparation process and superior in vitro/vivo bioactivity, the as-prepared ACMP/SIM would be a potential candidate for bone related biomedical applications.

Comparative Study of Technologies for Tubule Occlusion and Treatment of Dentin Hypersensitivity.

This study aimed to evaluate the occluding/remineralization performance and resistance to acid attacks of the mineralization layer formed by a tooth-desensitizing gel containing amorphous calcium magnesium phosphate (ACMP) particles and compare it to six other desensitizing products available on the market. Similar comprehensive studies are few and there is especially a lack of studies that are up to date. A dentin-disc model was used for in vitro evaluation of the desensitizing toothpastes/gels. Application of the products was performed twice daily for seven days. One set of specimens were evaluated using scanning electron microscopy (SEM) directly after the final treatment and another set was evaluated after an acid challenge, exposing specimens to 2 wt% citric acid. The ACMP desensitizing gel was the only product resulting in complete occlusion by the formation of mineralized material on the dentin surface and inside the tubules. Particle deposition was dominant after treatment with the other desensitizing products, with little or no mineralization, resulting in partial occlusion only. Sensodyne Repair & Protect and Oral-B Pro-Expert showed the highest resistance toward acid attacks. Material inside the tubules remained relatively unaffected by acid attacks in all specimens. The results in this study indicated a great variability among the occluding agents in terms of occlusion and acid resistance of the mineralization layer. The high degree of occlusion and intra-tubular mineralization that could mitigate the effect of acid solubilization indicate that the ACMP desensitizing gel may be a superior option for the treatment of dentin hypersensitivity.

Fused Filament Fabrication (Three-Dimensional Printing) of Amorphous Magnesium Phosphate/Polylactic Acid Macroporous Biocomposite Scaffolds.

The ultimate goal of this paper is to develop novel ceramic-polymer-based biocomposite orthopedic scaffolds with the help of additive manufacturing. Specifically, we incorporate a bioceramic known as amorphous magnesium phosphate (AMP) into polylactic acid (PLA) with the help of the melt-blending technique. Magnesium phosphate (MgP) was chosen as the bioactive component as previous studies have confirmed its favorable biomaterial properties, especially in orthopedics. Special care was taken to develop constant diameter AMP-PLA composite filaments, which would serve as feedstock for a fused filament fabrication (FFF)-based three-dimensional (3D) printer. Before the filaments were used for FFF, a thorough set of characterization protocols comprising of phase analysis, microstructure evaluations, thermal analysis, rheological analysis, and in vitro degradation determinations was performed on the biocomposites. Scanning electron microscopy (SEM) results confirmed a homogenous dispersion of AMP particles in the PLA matrix. Rheological studies demonstrated good printability behavior of the AMP-PLA filaments. In vitro degradation studies indicated a faster degradation rate in the case of AMP-PLA filaments as compared to the single phase PLA filaments. Subsequently, the filaments were fed into an FFF setup, and tensile bars and design-specific macroporous AMP-PLA scaffolds were printed. The biocomposite exhibited favorable mechanical properties. Furthermore, in vitro cytocompatibility results revealed higher pre-osteoblast cell attachment and proliferation on AMP-PLA scaffolds as compared to single-phase PLA scaffolds. Altogether, this study provides a proof of concept that design-specific bioactive AMP-PLA biocomposite scaffolds fabricated by FFF can be potential candidates as medical implants in orthopedics.

Highly tunable bioactive fiber-reinforced hydrogel for guided bone regeneration

One of the most damaging pathologies that affects the health of both soft and hard tissues around the tooth is periodontitis. Clinically, periodontal tissue destruction has been managed by an integrated approach involving elimination of injured tissues followed by regenerative strategies with bone substitutes and/or barrier membranes. Regrettably, a barrier membrane with predictable mechanical integrity and multifunctional therapeutic features has yet to be established. Herein, we report a fiber-reinforced hydrogel with unprecedented tunability in terms of mechanical competence and therapeutic features by integration of highly porous poly(ε-caprolactone) fibrous mesh(es) with well-controlled 3D architecture into bioactive amorphous magnesium phosphate-laden gelatin methacryloyl hydrogels. The presence of amorphous magnesium phosphate and PCL mesh in the hydrogel can control the mechanical properties and improve the osteogenic ability, opening a tremendous opportunity in guided bone regeneration (GBR). Results demonstrate that the presence of PCL meshes fabricated via melt electrowriting can delay hydrogel degradation preventing soft tissue invasion and providing the mechanical barrier to allow time for slower migrating progenitor cells to participate in bone regeneration due to their ability to differentiate into bone-forming cells. Altogether, our approach offers a platform technology for the development of the next-generation of GBR membranes with tunable mechanical and therapeutic properties to amplify bone regeneration in compromised sites. Statement of SignificanceIn this study, we developed a fiber-reinforced hydrogel platform with unprecedented tunability in terms of mechanical competence and therapeutic features for guided bone regeneration. We successfully integrated highly porous poly(ε-caprolactone) [PCL] mesh(es) into amorphous magnesium phosphate-laden hydrogels. The stiffness of the engineered hydrogel was significantly enhanced, and this reinforcing effect could be modulated by altering the number of PCL meshes and tailoring the AMP concentration. Furthermore, the fiber-reinforced hydrogel showed favorable cellular responses, significantly higher rates of mineralization, upregulation of osteogenic-related genes and bone formation. In sum, these fiber-reinforced membranes in combination with therapeutic agent(s) embedded in the hydrogel offer a robust, highly tunable platform to amplify bone regeneration not only in periodontal defects, but also in other craniomaxillofacial sites.

Bioactive amorphous magnesium phosphate-polyetheretherketone composite filaments for 3D printing

ObjectiveThe aim of this study was to develop bioactive and osseointegrable polyetheretherketone (PEEK)-based composite filaments melt-blended with novel amorphous magnesium phosphate (AMP) particles for 3D printing of dental and orthopedic implants. Materials and methodsA series of materials and biological analyses of AMP-PEEK were performed. Thermal stability, thermogravimetric and differential scanning calorimetry curves of as-synthesized AMP were measured. Complex viscosity, elastic modulus and viscous modulus were determined using a rotational rheometer. In vitro bioactivity was analyzed using SBF immersion method. SEM, EDS and XRD were used to study the apatite-forming ability of the AMP-PEEK filaments. Mouse pre-osteoblasts (MC3T3-E1) were cultured and analyzed for cell viability, proliferation and gene expression. For in vivo analyses, bare PEEK was used as the control and 15AMP-PEEK was chosen based on its in vitro cell-related results. After 4 or 12 weeks, animals were euthanized, and the femurs were collected for micro-computed tomography (μ-CT) and histology. ResultsThe collected findings confirmed the homogeneous dispersion of AMP particles within the PEEK matrix with no phase degradation. Rheological studies demonstrated that AMP-PEEK composites are good candidates for 3D printing by exhibiting high zero-shear and low infinite-shear viscosities. In vitro results revealed enhanced bioactivity and superior pre-osteoblast cell function in the case of AMP-PEEK composites as compared to bare PEEK. In vivo analyses further corroborated the enhanced osseointegration capacity for AMP-PEEK implants. SignificanceCollectively, the present investigation demonstrated that AMP-PEEK composite filaments can serve as feedstock for 3D printing of orthopedic and dental implants due to enhanced bioactivity and osseointegration capacity.

Electron microscopy evaluation of mineralization on peritubular dentin with amorphous calcium magnesium phosphate microspheres

Dentin hypersensitivity can be reduced by the use of a remineralization agent to hinder movement of fluids within the dentin tubules. Penetration of particles into the tubules and a continuous release of Ca2+ and phosphate ions can induce the mineralization of a material mimicking the mineral component of dentin, sealing the tubules. In this work, we have used complementary electron microscopy techniques to investigate the ultrastructure of dentin and crystallization and occlusion effects when using amorphous calcium magnesium phosphate (ACMP) microspheres on extracted human molars. Application of the particles in a gel intended for at-home use resulted in intra-tubular mineralization of a carbonate substituted hydroxyapatite (HA). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that crystallization was initiated on the peritubular dentin (PTD) with undirected crystal growth leading to the formation of a porous material. We additionally investigated the effects from using a fluoride toothpaste to potentially improve the remineralization and anti-cariogenic properties of the ACMP microspheres. Energy dispersive x-ray spectroscopy (EDX) using TEM in scanning mode (STEM) showed that fluoride incorporation resulted in an increase in aspect ratio of the crystals, crystal growth directed towards the center of the tubule lumen and densification of the mineralized material. Thus, ACMP microspheres are promising alternatives as occluding agents and the efficacy of the particles could be further improved with the complementary use of a fluoride toothpaste.

Amorphous Calcium Magnesium Phosphate Particles for Treatment of Dentin Hypersensitivity: A Mode of Action Study.

Occlusion of exposed dentin tubules may eliminate or reduce dentin hypersensitivity by hindering fluid movements within the tubules. In this study, the mode of action of spherical particles of amorphous calcium magnesium phosphate (180-440 nm in diameter) was studied. A degradation study of the particles in Tris-HCl buffer showed that the particles continuously released Ca2+, Mg2+, and phosphate, and XRD analysis revealed the formation of hydroxyapatite (HA) after 1 week. The occluding effect and efficacy of the spherical particles as an occluding agent were evaluated in an in vitro study. The ACMP particles were incorporated in a gel intended for at-home use and tested on extracted human molars. Application of the particles followed by incubation in artificial saliva resulted in occlusion of exposed tubules, and examination with SEM showed that the particles could penetrate the tubules down to 100 μm from the dentin surface. Transformation of the particles into nanocrystalline HA-structures (nanoHA) was initiated at the dentin surface within 12 h of application, and tubule penetration of the particles, accompanied by further ion release and diffusion of ions, resulted in deep intratubular occlusion in the majority of the tubules within 3 days from application. NanoHA was tightly adhered to the tubule walls, filling the entire tubule volume after 7 days. The results of this study demonstrate the mode of action of the amorphous calcium magnesium phosphate particles in occluding exposed dentin tubules. Interaction with saliva and transformation of the particles within the tubules inducing further mineralization indicate that the particles may be used as an effective treatment to reduce dentin hypersensitivity.

Preparation of Laser-Modified Ti-15Mo Surfaces With Multiphase Calcium Phosphate Coatings

Multiphasic bioceramic scaffolds has been enhanced for dental and orthopedic applications. In this perspective, the laser surface texturing of metallic surfaces combined to bioactive calcium phosphate coatings have shown to be promising and economically feasible for biomaterial clinical applications. Ti-15Mo alloy samples were irradiated by pulsed Yb: YAG laser beam. The formation of HA and other calcium phosphates phases by biomimetic method should occur in the presence of Ca2+, PO43-, Mg2+, HCO3-, K+ and Na+. The modified surfaces were submitted to thermal treatment at 380 and 580°C. The results showed the processes of fusion and fast solidification from the laser beam irradiation, inducing the formation of stoichiometric α-Ti, TiO2 and non-stoichiometric titanium oxides, Ti3O and Ti6O with different oxide percentages depending on applied fluency (fluency of 0.023, 0.033, 0.040 and 0.048 J/mm2). The morphological and physicochemical properties have indicated the formation of a multiphase bioceramic coatings. It was observed the formation of amorphous calcium phosphate (ACP), octacalcium phosphate (OCP), and magnesium phosphate (Mg3(PO4)2) phases at 380°C, whereas β-TCP (tricalcium phosphate), OCP, and substituted β-TCP with Ca2,589Mg0,41(PO4)2 were obtained at 580°C. Therefore, the multiphasic bioceramic modified Ti-15Mo surface could enhance osteointegration for bone regeneration.

Improvement of early-age properties of silico-aluminophosphate geopolymer using dead burnt magnesia

This paper proposes the induction of an acid-base reaction during the formation of silico-aluminophosphate (SAP) geopolymer. Such reaction is promoted by dead burnt magnesia (DBM) and phosphate activating solution to synthesize a DBM-doped silico-aluminophosphate (DBM-SAP) geopolymer with enhanced early-age properties. The reaction mechanisms and chemistries between DBM and mono-aluminum phosphate (MAP) in aqueous solution were firstly investigated at four Mg/Al ratios. Conductivity and pH evolutions of the solution systems, in addition to X-ray diffraction (XRD) and scanning electron microscopy (SEM) results of the final precipitations indicated that the crystalline phase (i.e., Newberyite) started to precipitate at a pH of 3 approximately. Besides, the reaction between DBM and MAP produced an amorphous aluminum magnesium phosphate (Al2O3·3MgO·2P2O5) phase. The rate of such reaction was governed by the DBM/MAP ratio in the solution system. Setting time and early strength of the DBM-SAP geopolymer pastes with an optimal Mg/Al ratio (i.e., 4) in solution system were evaluated to confirm the acceleration effect of DBM-induced acid-base reaction. Experimental results showed that 20% incorporation of DBM enabled the preparation of an SAP geopolymer with an initial setting time of 8 min and 1 day compressive strength of 8.3 MPa. Phosphorrösslerite was detected in the 1d-cured geopolymer paste but disappeared after 3 days curing. Such reaction intermediate might contribute to the fast setting and achieving early strength.

Nanostructured amorphous magnesium phosphate/poly (lactic acid) composite coating for enhanced corrosion resistance and bioactivity of biodegradable AZ31 magnesium alloy

Due to the combination many interesting properties, magnesium alloys have attracted considerable interest as suitable metallic biomaterials for bioresorbable orthopedic implants. Nevertheless, their fast degradation in physiological environments pose challenge for their practical applications. Here, we report that spin coating of composites of nano amorphous magnesium phosphate (nAMP) and poly (lactic acid) (PLA) on AZ31 magnesium alloy. The idea is to use the nAMP/PLA composite film while tailoring the degradation and enhancing the bioactivity of magnesium alloys. SEM examinations show that as-deposited nAMP/PLA film is smooth, crack-free and the nAMP particles are well distributed in PLA matrix. The electrochemical test including potentiodynamic polarization and EIS associated with immersion test results reveal that the corrosion activities of nAMP/PLA coated AZ31 magnesium alloy in SBF are markedly suppressed. Furthermore, it is seen that massive bone-like apatite precipitates formed on surface of nAMP/PLA coated sample, which is indicative for the superior biomineralization capability achieved by nAMP/PLA nanocomposite coating. Thus, the nAMP/PLA composite coating has great potential to be employed as the protective and bioactive coating on biodegradable magnesium alloys for orthopedic applications.

Microwave assisted coating of bioactive amorphous magnesium phosphate (AMP) on polyetheretherketone (PEEK)

Polyetheretherketone (PEEK) with great thermal and chemical stability, desirable mechanical properties and promising biocompatibility is being widely used as orthopedic and dental implant materials. However, the bioinert surface of PEEK can hinder direct osseointegration between the host tissue and PEEK based implants. The important signatures of this paper are as follows. First, we report for the formation of osseointegrable amorphous magnesium phosphate (AMP) coating on PEEK surface using microwave energy. Second, coatings consist of nano-sized AMP particles with a stacked thickness of 800nm. Third, coatings enhance bioactivity in-vitro and induce significantly high amount of bone-like apatite coating, when soaked in simulated body fluid (SBF). Fourth, the as-deposited AMP coatings present no cytotoxicity effects and are beneficial for cell adhesion at early stage. Finally, the high levels of expression of osteocalcin (OCN) in cells cultured on AMP coated PEEK samples indicate that AMP coatings can promote new bone formation and hence osseointegration.

Evaluation of amorphous magnesium phosphate (AMP) based non-exothermic orthopedic cements

This paper reports for the first time the development of a biodegradable, non-exothermic, self-setting orthopedic cement composition based on amorphous magnesium phosphate (AMP). The occurrence of undesirable exothermic reactions was avoided through using AMP as the solid precursor. The phenomenon of self-setting with optimum rheology is achieved by incorporating a water soluble biocompatible/biodegradable polymer, polyvinyl alcohol (PVA). Additionally, PVA enables a controlled growth of the final phase via a biomimetic process. The AMP powder was synthesized using a precipitation method. The powder, when in contact with the aqueous PVA solution, forms a putty resulting in a nanocrystalline magnesium phosphate phase of cattiite. The as-prepared cement compositions were evaluated for setting times, exothermicity, compressive strength, biodegradation, and microstructural features before and after soaking in SBF, and in vitro cytocompatibility. Since cattiite is relatively unexplored in the literature, a first time evaluation reveals that it is cytocompatible, just like the other phases in the MgO–P2O5 (Mg–P) system. The cement composition prepared with 15% PVA in an aqueous medium achieved clinically relevant setting times, mechanical properties, and biodegradation. Simulated body fluid (SBF) soaking resulted in coating of bobierrite onto the cement particle surfaces.