Microwave assisted synthesis of amorphous magnesium phosphate nanospheres

Osseointegration of 3D-Printable Polyetheretherketone-Magnesium Phosphate Bioactive Composites for Craniofacial and Orthopedic Implants

Polyetheretherketone (PEEK) is a high-performance polymer material for developing varying orthopedic, spine, cranial, maxillofacial, and dental implants. Despite their commendable mechanical properties and biocompatibility, the major limitation of PEEK implants is their low affinity to osseointegrate with the neighboring bone. Over the last two decades, several efforts have been made to incorporate bioactive components such as bioceramic particles in PEEK to enhance its osseointegration capacity. However, one major limitation is that the bioceramic particles embedded in the PEEK matrix can degrade over time, compromising the implant's long-term bioactivity and mechanical properties. To address this limitation, in this study, we utilized a unique bioceramic known as amorphous magnesium phosphate (AMP). AMP is a metastable phase of magnesium phosphate that nanocrystallizes in a physiological medium to stable bioactive phases exhibiting low degradation kinetics and high bioactivity. Thus, based on this property of AMP, we hypothesize that AMP-PEEK composites will exhibit sustained biodegradation kinetics, help maintain long-term osseointegration, and inhibit mechanical property degradation. Herein, we reported on a detailed in vitro degradation analysis of the developed AMP-PEEK composite 3D-printable filaments and the osseointegration capacity when implanted in a rat femoral model. The AMP-PEEK composite demonstrates controlled degradation kinetics, with tensile strength progressively decreasing from 120 to 70 MPa over a 28-day period due to hydrolytic degradation, which aligns with its role as a bioresorbable material. Notably, our findings confirm that AMP-PEEK composite osseointegration is on par with clinical gold-standard titanium implants. Thus, this study establishes a unique magnesium phosphate and PEEK-based bioactive composite material with promising potential for developing standalone dental and craniofacial implants.

Magnesium-Doped Hydroxyapatite Nanofibers for Medicine Applications: Characterization, Antimicrobial Activity, and Cytotoxicity Study

Magnesium-doped hydroxyapatite (HAp-Mg) nanofibers show promise for medical applications due to their structural similarity to bone minerals and enhanced biological properties, such as improved biocompatibility and antimicrobial activity. This study synthesized HAp-Mg nanofibers using a microwave-assisted hydrothermal method (MAHM) to evaluate their cytotoxicity, biocompatibility, and antimicrobial efficacy compared to commercial hydroxyapatite (HAp). Characterization through X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR) confirmed the successful incorporation of magnesium, producing high-purity, crystalline nanofibers with hexagonal morphology. Rietveld refinement showed slight lattice parameter shortening, indicating Mg2+ ion integration. Cell viability assays (MTT and AlamarBlue) revealed a significant increase in fibroblast proliferation with 2% and 5% HAp-Mg concentrations compared to controls (p < 0.05), demonstrating non-cytotoxicity and enhanced biocompatibility. Antimicrobial tests (disk diffusion method, 100 µg/mL) showed that HAp-Mg had strong antibacterial effects against Gram-positive and Gram-negative bacteria and moderate antifungal activity against Candida albicans. In contrast, commercial HAp showed no antimicrobial effects. These results suggest HAp-Mg nanofibers have significant advantages as biomaterials for medical applications, particularly in preventing implant-related infections and supporting further clinical development.

Evaluation of Magnesium-Phosphate Particle Incorporation into Co-Electrospun Chitosan-Elastin Membranes for Skin Wound Healing

Major challenges facing clinicians treating burn wounds are the lack of integration of treatment to wound, inadequate mechanical properties of treatments, and high infection rates which ultimately lead to poor wound resolution. Electrospun chitosan membranes (ESCM) are gaining popularity for use in tissue engineering applications due to their drug loading ability, biocompatibility, biomimetic fibrous structure, and antimicrobial characteristics. This work aims to modify ESCMs for improved performance in burn wound applications by incorporating elastin and magnesium-phosphate particles (MgP) to improve mechanical and bioactive properties. The following ESCMs were made to evaluate the individual components’ effects; (C: chitosan, CE: chitosan-elastin, CMg: chitosan-MgP, and CEMg: chitosan-elastin-MgP). Membrane properties analyzed were fiber size and structure, hydrophilic properties, elastin incorporation, MgP incorporation and in vitro release, mechanical properties, degradation profiles, and in vitro cytocompatibility with NIH3T3 fibroblasts. The addition of both elastin and MgP increased the average fiber diameter of CE (~400 nm), CMg (~360 nm), and CEMg (565 nm) compared to C (255 nm). Water contact angle analysis showed elastin incorporated membranes (CE and CEMg) had increased hydrophilicity (~50°) compared to the other groups (C and CMg, ~110°). The results from the degradation study showed mass retention of ~50% for C and CMg groups, compared to ~ 30% seen in CE and CEMg after 4 weeks in a lysozyme/PBS solution. CMg and CEMg exhibited burst-release behavior of ~6 µg/ml or 0.25 mM magnesium within 72 h. In vitro analysis with NIH3T3 fibroblasts showed CE and CEMg groups had superior cytocompatibility compared to C and CMg. This work has demonstrated the successful incorporation of elastin and MgP into ESCMs and allows for future studies on burn wound applications.

Magnesium Phosphate Bioceramics for Bone Tissue Engineering

Magnesium phosphate (MgP) is a family of newly developed resorbable bioceramics for bone tissue engineering. Although calcium phosphates (CaP) are the most commonly used bioceramics, low solubility, and slow degradation, when implanted in vivo, are their main drawbacks. Magnesium (Mg) is an essential element in the human body as it plays important role in bone metabolism, DNA stabilization, and skeletal development. Recent research on magnesium phosphates has established their higher degradability, in vitro, and in vivo biocompatibility. Compared to CaP, very limited research work has been found in the area of MgP. The prime goal of this review is to bring out the importance of magnesium phosphate ceramics for biomedical applications. In this review, we have discussed the synthesis methods, mechanical properties, in vitro and in vivo biocompatibility of MgP bioceramics. Moreover, we have highlighted the recent developments in metal ion-doped MgPs and MgP scaffolds for bone tissue engineering.

Mesoporous Biodegradable Magnesium Phosphate-Citrate Nanocarriers Amplify Methotrexate Anticancer Activity in HeLa Cells

We present the synthesis of amorphous, mesoporous, colloidal magnesium phosphate-citrate nanoparticles (MPCs) from biogenic precursors, resulting in a biocompatible and biodegradable nanocarrier that amplifies the action of the anticancer drug methotrexate (MTX). Synthesis conditions were gradually tuned to investigate the influence of the chelating agent citric acid on the colloidal stability and the mesoporosity of the obtained nanoparticles. With optimized synthesis conditions, a large BET surface area of 560 m²/g was achieved. We demonstrate the potential of these biocompatible and biodegradable mesoporous MPCs as a drug delivery system. Lipid-coated MPCs were used to load the fluorescent dye calcein and the chemotherapeutic agent MTX into the mesopores. In vitro experiments show very low premature release of the cargo but efficient stimuli-responsive release in an environment of pH 5.5, in which MPCs degrade. Lipid-coated MPCs are taken up by cancer cells and are nontoxic up to concentrations of 100 μg/mL. When loaded with MTX serving as a representative model drug for in vitro studies, MPCs induced efficient cell death with an IC₅₀ value of 1.1 μg/mL. Compared to free MTX, its delivery with MPCs enhances its efficiency by an order of magnitude. In summary, we have developed a biodegradable nanomaterial synthesized from biocompatible precursors that are neither toxic by themselves nor in the form of nanoparticles. With these features, MPCs may be applied as drug delivery systems and have the potential to reduce the side effects of current chemotherapies.

Rapid Fabrication of MgNH4PO4·H2O/SrHPO4 Porous Composite Scaffolds with Improved Radiopacity via 3D Printing Process

Although bone repair scaffolds are required to possess high radiopacity to be distinguished from natural bone tissues in clinical applications, the intrinsic radiopacity of them is usually insufficient. For improving the radiopacity, combining X-ray contrast agents with bone repair scaffolds is an effective method. In the present research, MgNH₄PO₄·H₂O/SrHPO₄ 3D porous composite scaffolds with improved radiopacity were fabricated via the 3D printing technique. Here, SrHPO₄ was firstly used as a radiopaque agent to improve the radiopacity of magnesium phosphate scaffolds. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) were used to characterize the phases, morphologies, and element compositions of the 3D porous composite scaffolds. The radiography image showed that greater SrHPO₄ contents corresponded to higher radiopacity. When the SrHPO₄ content reached 9.34%, the radiopacity of the composite scaffolds was equal to that of a 6.8 mm Al ladder. The porosity and in vitro degradation of the porous composite scaffolds were studied in detail. The results show that magnesium phosphate scaffolds with various Sr contents could sustainably degrade and release the Mg, Sr, and P elements during the experiment period of 28 days. In addition, the cytotoxicity on MC3T3-E1 osteoblast precursor cells was evaluated, and the results show that the porous composite scaffolds with a SrHPO₄ content of 9.34% possessed superior cytocompatibility compared to that of the pure MgNH₄PO₄·H₂O scaffolds when the extract concentration was 0.1 g/mL. Cell adhesion experiments showed that all of the scaffolds could support MC3T3-E1 cellular attachment well. This research indicates that MgNH₄PO₄·H₂O/SrHPO₄ porous composite scaffolds have potential applications in the bone repair fields.

Resorbable Mg2+-Containing Phosphates for Bone Tissue Repair

Materials based on Mg2+-containing phosphates are gaining great relevance in the field of bone tissue repair via regenerative medicine methods. Magnesium ions, together with condensed phosphate ions, play substantial roles in the process of bone remodeling, affecting the early stage of bone regeneration through active participation in the process of osteosynthesis. In this paper we provide a comprehensive overview of the usage of biomaterials based on magnesium phosphate and magnesium calcium phosphate in bone reconstruction. We consider the role of magnesium ions in angiogenesis, which is an important process associated with osteogenesis. Finally, we summarize the biological properties of calcium magnesium phosphates for regeneration of bone.

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.

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

OBJECTIVE

The 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 METHODS

A 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.

RESULTS

The 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.

SIGNIFICANCE

Collectively, 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.

The combined antibacterial and anticancer properties of nano Ce-containing Mg-phosphate ceramic

AIM

This paper was mainly aimed at synthesis of Ce-containing nano-Mg-phosphate ceramic as a multifunctional material.

MATERIALS AND METHODS

Two ceramics based on Mg₃(PO₄)₂ and Ce_0.2Mg_2.8(PO₄)₂ formulas (MP and MP-C, respectively) were synthesized. The synthesized powders were characterized by XRD, TEM, Zeta potential, and FTIR. Also, their dissolution behavior was tested in Tris-HCl buffer solution. Moreover, the antimicrobial efficacy was evaluated against gram-positive bacteria (Bacillus sphaericus MTCC 511 &Staphylococcus aureus MTCC 87) and gram-negative bacteria (Enterobacter aerogenes MTCC 111 &Pseudomonas aeruginosa MTCC 1034) using dick diffusion assay and microdilution method. Furthermore, the cell viability test was performed for the ceramics on Vero cells (African green monkey kidney cells), and their antitumor activity was determined by PC3 cell line (prostatic cancer). Also, the cellular uptake was determined by the flow cytometry.

KEY FINDINGS

The results showed that the substitution of Mg by Ce decreased the particle size from 40 to 90 nm for MP sample to 2-10 nm for MP-C sample and increased the degradation rate. Both samples showed excellent antimicrobial activities. Moreover, MP demonstrated more cell viability than MP-C on Vero cells at high concentrations, whereas, MP-C showed more antitumor activity on PC3 cells than MP sample. Moreover, MP-C showed a higher cell uptake than MP due to its smaller size and more negative charge.

SIGNIFICANCE

Mg-phosphate ceramic can be used in this study successfully as a delivery system for cerium ions and showed a high antitumor activity, which makes it highly recommended as safe and effective cancer treatment materials.

Magnesium-based bioceramics in orthopedic applications

Magnesium ions are directly involved in numerous biological mechanisms; for example, they play an important part in the regulation of ion channels, DNA stabilization, enzyme activation and stimulation of cell growth and proliferation. This alkaline earth metal has gained great popularity in orthopedic applications in recent years. Magnesium-based bioceramics include a large group of magnesium containing compounds such as oxides, phosphates and silicates, that are involved in orthopedic applications like bone cements, bone scaffolds or implant coatings. This article aims to give a comprehensive review on different magnesium-based bioceramics, e.g. magnesium phosphates (MgO-P₂O₅), calcium magnesium phosphates (CaO-MgO-P₂O₅), and magnesium glasses (SiO₂-MgO) with a strong focus on the chemistry and properties of magnesium phosphate containing cements as the main application form. In addition, the processing of magnesium phosphate minerals into macroporous scaffolds for tissue engineering applications by either using traditional porogens or by additive manufacturing approaches are reflected. Finally, the biological in vitro and in vivo properties of magnesium phosphates for bone regeneration are summarized, which show promising results regarding the application as bone replacement material, but still lack in terms of testing in large animal models, load-bearing application sites and clinical data.

STATEMENT OF SIGNIFICANCE

Though bone substitutes from calcium phosphates have been investigated for a long time, a new trend is visible in the biomaterials sector: magnesium based bioceramics from magnesium phosphates and silicates due to the special biological significance of magnesium ions in enzymatic activation, cell growth and proliferation, etc. In contrast to pure magnesium implants, such formulations do not release hydrogen during degradation. As with calcium based bioceramics, magnesium based bioceramics are used for the development of diverse applications such as cements, macroporous scaffolds and coatings. From this perspective, we present a systematic overview on diverse kinds of magnesium based bioceramics, their processing regimes for different clinical purposes and their behavior both in vitro and in vivo.

Effects of sintering temperature on surface morphology/microstructure, in vitro degradability, mineralization and osteoblast response to magnesium phosphate as biomedical material

Magnesium phosphate (MP) was fabricated using a chemical precipitation method, and the biological performances of MP sintered at different temperatures as a biomedical material was investigated. The results indicated that the densification and crystallinity of MP increased as the sintering temperature increased. As the sintering temperature increased, the degradability of MP in PBS decreased, and the mineralization ability in SBF significantly increased. In addition, the MP sintered at 800 °C (MP8) possessed the lowest degradability and highest mineralization ability. Moreover, the positive response of MG63 cells to MP significantly increased as the sintering temperature increased, and MP8 significantly promoted the cell spreading, proliferation, differentiation and expressions of osteogenic differentiation-related genes. Faster degradation of MP0 resulted in higher pH environments and ion concentrations, which led to negative responses to osteoblasts. However, the appropriate degradation of MP8 resulted in suitable pH environments and ion concentrations, which led to positive responses to osteoblasts. This study demonstrated that the sintering temperature substantially affected the surface morphology/microstructure, degradability and mineralization, and osteoblasts response to magnesium phosphate.

Magnesium Phosphate Cement Systems for Hard Tissue Applications: A Review

In the search for more ideal bone graft materials for clinical application, the investigation into ceramic bone cements or bone void filler is ongoing. Calcium phosphate-based materials have been widely explored and implemented for medical use in bone defect repair. Such materials are an excellent choice because the implant mimics the natural chemistry of mineralized bone matrix and in injectable cement form, can be implemented with relative ease. However, of the available calcium phosphate cements, none fully meet the ideal standard, displaying low strengths and acidic setting reactions or slow setting times, and are often very slow to resorb in vivo. The study of magnesium phosphates for bone cements is a relatively new field compared to traditional calcium phosphate bone cements. Although reports are more limited, preliminary studies have shown that magnesium phosphate cements (MPC) may be a strong alternative to calcium phosphates for certain applications. The goal of the present publication is to review the history and achievements of magnesium phosphate-based cements or bone void fillers to date, assess how these cements compare with calcium phosphate competitors and to analyze the future directions and outlook for the research, development, and clinical implementation of these cements.

Magnesium substitution in the structure of orthopedic nanoparticles: A comparison between amorphous magnesium phosphates, calcium magnesium phosphates, and hydroxyapatites

As biocompatible materials, magnesium phosphates have received a lot of attention for orthopedic applications. During the last decade multiple studies have shown advantages for magnesium phosphate such as lack of cytotoxicity, biocompatibility, strong mechanical properties, and high biodegradability. The present study investigates the role of Mg(+2) and Ca(+2) ions in the structure of magnesium phosphate and calcium phosphate nanoparticles. To directly compare the effect of Mg(+2) and Ca(+2) ions on structure of nanoparticles and their biological behavior, three groups of nanoparticles including amorphous magnesium phosphates (AMPs) which release Mg(+2), calcium magnesium phosphates (CMPs) which release Mg(+2) and Ca(+2), and hydroxyapatites (HAs) which release Ca(+2) were studied. SEM, TEM, XRD, and FTIR were used to evaluate the morphology, crystallinity, and chemical properties of the particles. AMP particles were homogeneous nanospheres, whereas CMPs were combinations of heterogeneous nanorods and nanospheres, and HAs which contained heterogeneous nanosphere particles. Cell compatibility was monitored in all groups to determine the cytotoxicity effect of particles on studied MC3T3-E1 preosteoblasts. AMPs showed significantly higher attachment rate than the HAs after 1 day and both AMPs and CMPs showed significantly higher proliferation rate when compared to HAs after 7days. Gene expression level of osteoblastic markers ALP, COL I, OCN, OPN, RUNX2 were monitored and they were normalized to GAPDH housekeeping gene. Beta actin expression level was monitored as the second housekeeping gene to confirm the accuracy of results. In general, AMPs and CMPs showed higher expression level of osteoblastic genes after 7 days which can further confirm the stimulating role of Mg(+2) and Ca(+2) ions in increasing the proliferation rate, differentiation, and mineralization of MC3T3-E1 preosteoblasts.

Development of monetite-nanosilica bone cement: a preliminary study

In this paper, we reported the results of our efforts in developing DCPA/nanosilica composite orthopedic cement. It is motivated by the significances of DCPA and silicon in bone physiological activities. More specifically, this paper examined the effects of various experimental parameters on the properties of such composite cements. In this work, DCPA cement powders were synthesized using a microwave synthesis technique. Mixing colloidal nanosilica directly with synthesized DCPA cement powders can significantly reduce the washout resistance of DCPA cement. In contrast, a DCPA-nanosilica cement powder prepared by reacting Ca(OH)2 , H3 PO4 and nanosilica together showed good washout resistance. The incorporation of nanosilica in DCPA can improve compressive strength, accelerate cement solidification, and intensify surface bioactivity. In addition, it was observed that by controlling the content of NaHCO3 during cement preparation, the resulting composite cement properties could be modified. Allowing for the development of different setting times, mechanical performance and crystal features. It is suggested that DCPA-nanosilica composite cement can be a potential candidate for bone healing applications.