Enhancing the mechanical properties and cytocompatibility of magnesium potassium phosphate cement by incorporating oxygen-carboxymethyl chitosan

Nanofiber-induced hierarchically-porous magnesium phosphate bone cements accelerate bone regeneration by inhibiting Notch signaling

Magnesium phosphate bone cements (MPC) have been recognized as a viable alternative for bone defect repair due to their high mechanical strength and biodegradability. However, their poor porosity and permeability limit osteogenic cell ingrowth and vascularization, which is critical for bone regeneration. In the current study, we constructed a novel hierarchically-porous magnesium phosphate bone cement by incorporating extracellular matrix (ECM)-mimicking electrospun silk fibroin (SF) nanofibers. The SF-embedded MPC (SM) exhibited a heterogeneous and hierarchical structure, which effectively facilitated the rapid infiltration of oxygen and nutrients as well as cell ingrowth. Besides, the SF fibers improved the mechanical properties of MPC and neutralized the highly alkaline environment caused by excess magnesium oxide. Bone marrow stem cells (BMSCs) adhered excellently on SM, as illustrated by formation of more pseudopodia. CCK8 assay showed that SM promoted early proliferation of BMSCs. Our study also verified that SM increased the expression of OPN, RUNX2 and BMP2, suggesting enhanced osteogenic differentiation of BMSCs. We screened for osteogenesis-related pathways, including FAK signaing, Wnt signaling and Notch signaling, and found that SM aided in the process of bone regeneration by suppressing the Notch signaling pathway, proved by the downregulation of NICD1, Hes1 and Hey2. In addition, using a bone defect model of rat calvaria, the study revealed that SM exhibited enhanced osteogenesis, bone ingrowth and vascularization compared with MPC alone. No adverse effect was found after implantation of SM in vivo. Overall, our novel SM exhibited promising prospects for the treatment of critical-sized bone defects.

Surface functionalization of calcium magnesium phosphate cements with alginate sodium for enhanced bone regeneration via TRPM7/PI3K/Akt signaling pathway

Although calcium‑magnesium phosphate cements (CMPCs) have been widely applied to treating critical-size bone defects, their repair efficiency is unsatisfactory owing to their weak surface bioactivity and uncontrolled ion release. In this study, we lyophilized alginate sodium (AS) as a coating onto HAp/K-struvite (H@KSv) to develop AS/HAp/K-struvite (AH@KSv), which promotes bone regeneration. The compressive strength and hydrophilicity of AH@KSv significantly improved, leading to enhanced cell adhesion in vitro. Importantly, the SA coating enables continuous ions release of Mg2+ and Ca2+, finally leading to enhanced osteogenesis in vitro/vivo and different patterns of new bone ingrowth in vivo. Furthermore, these composites increased the expression levels of biomarkers of the TRPM7/PI3K/Akt signaling pathway via an equilibrium effect of Mg2+ to Ca2+. In conclusion, our study provides novel insights into the mechanisms of Mg-based biomaterials for bone regeneration.

Research progress on the application of magnesium phosphate bone cement in bone defect repair: A review

BACKGROUND

Bone defects arising from diverse causes, such as traffic accidents, contemporary weapon usage, and bone-related disorders, present significant challenges in clinical treatment. Prolonged treatment cycles for bone defects can result in complications, impacting patients' overall quality of life. Efficient and timely repair of bone defects is thus a critical concern in clinical practice.

OBJECTIVE

This study aims to assess the scientific progress and achievements of magnesium phosphate bone cement (MPC) as an artificial bone substitute material. Additionally, the research seeks to explore the future development path and clinical potential of MPC bone cement in addressing challenges associated with bone defects.

METHODS

The study comprehensively reviews MPC's performance, encompassing e.g. mechanical properties, biocompatibility, porosity, adhesion and injectability. Various modifiers are also considered to broaden MPC's applications in bone tissue engineering, emphasizing drug-loading performance and antibacterial capabilities, which meet clinical diversification requirements.

RESULTS

In comparison to alternatives such as autogenous bone transplantation, allograft, polymethyl methacrylate (PMMA), and calcium phosphate cement (CPC), MPC emerges as a promising solution for bone defects. It addresses limitations associated with these alternatives, such as immunological rejection and long-term harm to patients. MPC can control heat release during the curing process, exhibits superior mechanical strength, and has the capacity to stimulate new bone growth.

CONCLUSION

MPC stands out as an artificial bone substitute with appropriate mechanical strength, rapid degradation, non-toxicity, and good biocompatibility, facilitating bone repair and regeneration. Modification agents can enhance its clinical versatility. Future research should delve into its mechanical properties and formulations, expanding clinical applications to create higher-performing and more medically valuable alternatives in bone defect repair.

Dual-Setting Bone Cement Based On Magnesium Phosphate Modified with Glycol Methacrylate Designed for Biomedical Applications

Magnesium phosphate cement (MPC) is a suitable alternative for the currently used calcium phosphates, owing to beneficial properties like favorable resorption rate, fast hardening, and higher compressive strength. However, due to insufficient mechanical properties and high brittleness, further improvement is still expected. In this paper, we reported the preparation of a novel type of dual-setting cement based on MPC with poly(2-hydroxyethyl methacrylate) (pHEMA). The aim of our study was to evaluate the effect of HEMA addition, especially its concentration and premix time, on the selected properties of the composite. Several beneficial effects were found: better formability, shortened setting time, and improvement of mechanical strengths. The developed cements were hardening in ∼16-21 min, consisted of well-crystallized phases and polymerized HEMA, had porosity between ∼2-11%, degraded slowly by ∼0.1-4%/18 days, their wettability was ∼20-30°, they showed compressive and bending strength between ∼45-73 and 13-20 MPa, respectively, and, finally, their Young's Modulus was close to ∼2.5-3.0 GPa. The results showed that the optimal cement composition is MPC+15%HEMA and 4 min of polymer premixing time. Overall, our research suggested that this developed cement may be used in various biomedical applications.

Is it possible to 3D bioprint load-bearing bone implants? A critical review

Rehabilitative capabilities of any tissue engineered scaffold rely primarily on the triad of (i) biomechanical properties such as mechanical properties and architecture, (ii) chemical behavior such as regulation of cytokine expression, and (iii) cellular response modulation (including their recruitment and differentiation). The closer the implant can mimic the native tissue, the better it can rehabilitate the damage therein. Among the available fabrication techniques, only 3D bioprinting (3DBP) can satisfactorily replicate the inherent heterogeneity of the host tissue. However, 3DBP scaffolds typically suffer from poor mechanical properties, thereby, driving the increased research interest in development of load-bearing 3DBP orthopedic scaffolds in recent years. Typically, these scaffolds involve multi-material 3D printing, comprising of at-least one bioink and a load-bearing ink; such that mechanical and biological requirements of the biomaterials are decoupled. Ensuring high cellular survivability and good mechanical properties are of key concerns in all these studies. 3DBP of such scaffolds is in early developmental stages, and research data from only a handful of preliminary animal studies are available, owing to limitations in print-capabilities and restrictive materials library. This article presents a topically focused review of the state-of-the-art, while highlighting aspects like available 3DBP techniques; biomaterials' printability; mechanical and degradation behavior; and their overall bone-tissue rehabilitative efficacy. This collection amalgamates and critically analyses the research aimed at 3DBP of load-bearing scaffolds for fulfilling demands of personalized-medicine. We highlight the recent-advances in 3DBP techniques employing thermoplastics and phosphate-cements for load-bearing applications. Finally, we provide an outlook for possible future perspectives of 3DBP for load-bearing orthopedic applications. Overall, the article creates ample foundation for future research, as it gathers the latest and ongoing research that scientists could utilize.

An Overview of Magnesium-Phosphate-Based Cements as Bone Repair Materials

In the search for effective biomaterials for bone repair, magnesium phosphate cements (MPCs) are nowadays gaining importance as bone void fillers thanks to their many attractive features that overcome some of the limitations of the well-investigated calcium-phosphate-based cements. The goal of this review was to highlight the main properties and applications of MPCs in the orthopedic field, focusing on the different types of formulations that have been described in the literature, their main features, and the in vivo and in vitro response towards them. The presented results will be useful to showcase the potential of MPCs in the orthopedic field and will suggest novel strategies to further boost their clinical application.

Customized bioceramic scaffolds and metal meshes for challenging large-size mandibular bone defect regeneration and repair

Large-size mandible graft has huge needs in clinic caused by infection, tumor, congenital deformity, bone trauma and so on. However, the reconstruction of large-size mandible defect is challenged due to its complex anatomical structure and large-range bone injury. The design and fabrication of porous implants with large segments and specific shapes matching the native mandible remain a considerable challenge. Herein, the 6% Mg-doped calcium silicate (CSi-Mg6) and β- and α-tricalcium phosphate (β-TCP, α-TCP) bioceramics were fabricated by digital light processing as the porous scaffolds of over 50% in porosity, while the titanium mesh was fabricated by selective laser melting. The mechanical tests showed that the initial flexible/compressive resistance of CSi-Mg6 scaffolds was markedly higher than that of β-TCP and α-TCP scaffolds. Cell experiments showed that these materials all had good biocompatibility, while CSi-Mg6 significantly promoted cell proliferation. In the rabbit critically sized mandible bone defects (∼13 mm in length) filled with porous bioceramic scaffolds, the titanium meshes and titanium nails were acted as fixation and load bearing. The results showed that the defects were kept during the observation period in the blank (control) group; in contrast, the osteogenic capability was significantly enhanced in the CSi-Mg6 and α-TCP groups in comparison with the β-TCP group, and these two groups not only had significantly increased new bone formation but also had thicker trabecular and smaller trabecular spacing. Besides, the CSi-Mg6 and α-TCP groups showed appreciable material biodegradation in the later stage (from 8 to 12 weeks) in comparison with the β-TCP scaffolds while the CSi-Mg6 group showed much outstanding mechanical capacity in vivo in the early stage compared to the β-TCP and α-TCP groups. Totally, these findings suggest that the combination of customized strength-strong bioactive CSi-Mg6 scaffolds together with titanium meshes is a promising way for repairing the large-size load-bearing mandible defects.

Carboxymethyl chitosan-alginate enhances bone repair effects of magnesium phosphate bone cement by activating the FAK-Wnt pathway

There is a continuing need for artificial bone substitutes for bone repair and reconstruction, Magnesium phosphate bone cement (MPC) has exceptional degradable properties and exhibits promising biocompatibility. However, its mechanical strength needs improved and its low osteo-inductive potential limits its therapeutic application in bone regeneration. We functionally modified MPC by using a polymeric carboxymethyl chitosan-sodium alginate (CMCS/SA) gel network. This had the advantages of: improved compressive strength, ease of handling, and an optimized interface for bioactive bone in-growth. The new composites with 2% CMCS/SA showed the most favorable physicochemical properties, including mechanical strength, wash-out resistance, setting time, injectable time and heat release. Biologically, the composite promoted the attachment and proliferation of osteoblast cells. It was also found to induce osteogenic differentiation in vitro, as verified by expression of osteogenic markers. In terms of molecular mechanisms, data showed that new bone cement activated the Wnt pathway through inhibition of the phosphorylation of β-catenin, which is dependent on focal adhesion kinase. Through micro-computed tomography and histological analysis, we found that the MPC-CMCS/SA scaffolds, compared with MPC alone, showed increased bone regeneration in a rat calvarial defect model. Overall, our study suggested that the novel composite had potential to help repair critical bone defects in clinical practice.

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CMCS/SA improves the mechanical strength of MPC while minimizing tissue damage.

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The MPC-CMCS/SA composite is easily manipulable for clinical application.

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MPC-CMCS/SA has good biocompatibility, and is easier for cell adhesion and proliferation.

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The MPC-CMCS/SA composite enhances osteogenic differentiation in vitro through the integrin-FAK-Wnt axis.

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The MPC-CMCS/SA composite enhances critical bone defect repair in vivo.

A hydrophobic layer prepared by cyclic grafting of polydimethylsiloxane on magnesium: improved corrosion resistance and biocompatibility

Magnesium and its alloys have been widely studied as absorbable coronary stent materials. However, the rapid corrosion rate in the intravascular environment inhibits the application of magnesium-based stents. In order to endow magnesium-based stent with appropriate degradation rate and biocompatibility, a hydrophobic layer was constructed by in situ cyclic grafting 4,4'-diphenylmethane diisocyanate and aminopropyl-terminated polydimethylsiloxane on pure magnesium. SEM-EDS, X-ray photoelectron spectroscopy and water contact angle were detected to analyze the chemical composition of the layer. The amino groups were confirmed to be introduced on the surface which provide a platform for subsequent modification. The contact angle value of the modified surface is 132.1°, indicating a hydrophilic surface. The electrochemical measurements and immersion tests demonstrated that the hydrophobic layer significantly improved the anti-corrosion ability of the substrate. Besides, the biocompatibility of the hydrophobic surface was examined by platelet adhesion, cytocompatibility in vitro and subcutaneous implantation in vivo. Immunological and histological results indicated that the hydrophobic layer had excellent biocompatibility. Therefore, the presented study might be a promising method for the surface modification of biomedical magnesium-based stent.

Improvement of the mechanical properties and osteogenic activity of 3D-printed polylactic acid porous scaffolds by nano-hydroxyapatite and nano-magnesium oxide

Porous bone scaffolds based on high-precision 3D printing technology gave recently been developed for use in bone defect repair. However, conventional scaffold materials have poor mechanical properties and low osteogenic activity, limiting their clinical use. In this study, a porous composite tissue-engineered bone scaffold was prepared using polylactic acid, nano-hydroxyapatite, and nano-magnesium oxide as raw materials for high-precision 3D printing. The composite scaffold takes full advantage of the personalized manufacturing features of 3D printers and can be used to repair complex bone defects in clinical settings. The composite scaffold combines the advantages of nano-hydroxyapatite, which improves the formability of scaffold printing, and of nano-magnesium oxide, which regulates pH during degradation and provide a good environment for cell growth. Additionally, nano-magnesium oxide and nano-hydroxyapatite have a bidirectional effect on promoting the compressive strength and osteogenic activity of the scaffolds. The prepared composite porous scaffolds based on 3D printing technology show promise for bone defect repair.

Influence of Monocalcium Phosphate on the Properties of Bioactive Magnesium Phosphate Bone Cement for Bone Regeneration

Bone defects occurring for various reasons can lead to deformities and dysfunctions of the human body. Considering the need for clinical applications, it is essential for bone regeneration to exploit a scaffold with bioactive bone cement. In this study, we fabricated bioactive magnesium phosphate bone cement (BMPC) at room temperature; then, it was set at to °Cand 100% humidity for 2 h. The process was as follows: Simulating a clinical environment, magnesium oxide (MgO) was formed by calcining basic magnesium carbonate (Mg2(OH)2CO3). MgO, potassium dihydrogen phosphate (KH2PO4) and carboxymethyl chitosan (C20H37N3O14, CMC) were mixed to form magnesium phosphate bone cement (MPC); then, monocalcium phosphate (Ca(H2PO4)2) was added to neutralize the alkaline product after MPC hydration to fabricate bioactive magnesium phosphate bone cement (BMPC). The influence of the doped content of Ca(H2PO4)2 on the properties of bone cement was discussed. The results showed that Ca(H2PO4)2 and CMC can adjust the setting time of bone cement to between 8 and 25 min. The compressive strength increased first and then decreased. After 48 h without additional pressure, the compressive strength reached the maximum value, which was about 38.6 MPa. Ca(H2PO4)2 and CMC can play a synergistic role in regulating the properties of BMPC. The BMPC was degradable in the simulated body fluid (SBF). The results of the cytotoxicity experiment and laser confocal microscopy experiment indicated that BMPC fabricated at room temperature had better biocompatibility and degradability, which was more consistent with clinical operation requirements. BMPC is a promising orthopedic material and is suitable for repairing bone defects.

Biodegradable magnesium phosphates in biomedical applications

As an essential element, magnesium is involved in a variety of physiological processes. Magnesium is the second most abundant cation in cells and the fourth most abundant cation in living...

Double-edged effects caused by magnesium ions and alkaline environment regulate bioactivities of magnesium-incorporated silicocarnotite in vitro

Magnesium (Mg) is an important element for its enhanced osteogenic and angiogenic properties in vitro and in vivo, however, the inherent alkalinity is the adverse factor that needs further attention. In order to study the role of alkalinity in regulating osteogenesis and angiogenesis in vitro, magnesium-silicocarnotite [Mg-Ca₅(PO₄)₂SiO₄, Mg-CPS] was designed and fabricated. In this study, Mg-CPS showed better osteogenic and angiogenic properties than CPS within 10 wt.% magnesium oxide (MgO), since the adversity of alkaline condition was covered by the benefits of improved Mg ion concentrations through activating Smad2/3-Runx2 signaling pathway in MC3T3-E1 cells and PI3K-AKT signaling pathway in human umbilical vein endothelial cells in vitro. Besides, provided that MgO was incorporated with 15 wt.% in CPS, the bioactivities had declined due to the environment consisting of higher-concentrated Mg ions, stronger alkalinity and lower Ca/P/Si ions caused. According to the results, it indicated that bioactivities of Mg-CPS in vitro were regulated by the double-edged effects, which were the consequence of Mg ions and alkaline environment combined. Therefore, if MgO is properly incorporated in CPS, the improved bioactivities could cover alkaline adversity, making Mg-CPS bioceramics promising in orthopedic clinical application for its enhancement of osteogenesis and angiogenesis in vitro.

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.