The Development of a Magnesium-Releasing and Long-Term Mechanically Stable Calcium Phosphate Bone Cement Possessing Osteogenic and Immunomodulation Effects for Promoting Bone Fracture Regeneration

Magnesium malate-modified calcium phosphate bone cement promotes the repair of vertebral bone defects in minipigs via regulating CGRP

Active artificial bone substitutes are crucial in bone repair and reconstruction. Calcium phosphate bone cement (CPC) is known for its biocompatibility, degradability, and ability to fill various shaped bone defects. However, its low osteoinductive capacity limits bone regeneration applications. Effectively integrating osteoinductive magnesium ions with CPC remains a challenge. Herein, we developed magnesium malate-modified CPC (MCPC). Incorporating 5% magnesium malate significantly enhances the compressive strength of CPC to (6.18 ± 0.49) MPa, reduces setting time and improves disintegration resistance. In vitro, MCPC steadily releases magnesium ions, promoting the proliferation of MC3T3-E1 cells without causing significant apoptosis, proving its biocompatibility. Molecularly, magnesium malate prompts macrophages to release prostaglandin E2 (PGE2) and synergistically stimulates dorsal root ganglion (DRG) neurons to synthesize and release calcitonin gene-related peptide (CGRP). The CGRP released by DRG neurons enhances the expression of the key osteogenic transcription factor Runt-related transcription factor-2 (RUNX2) in MC3T3-E1 cells, promoting osteogenesis. In vivo experiments using minipig vertebral bone defect model showed MCPC significantly increases the bone volume fraction, bone density, new bone formation, and proportion of mature bone in the defect area compared to CPC. Additionally, MCPC group exhibited significantly higher levels of osteogenesis and angiogenesis markers compared to CPC group, with no inflammation or necrosis observed in the hearts, livers, or kidneys, indicating its good biocompatibility. In conclusion, MCPC participates in the repair of bone defects in the complex post-fracture microenvironment through interactions among macrophages, DRG neurons, and osteoblasts. This demonstrates its significant potential for clinical application in bone defect repair.

Magnesium-Organic Framework-Loaded Bisphosphonate-Functionalized Gel Scaffolds for Enhanced Bone Regeneration

The development of magnesium-derived biomaterials is one of the most promising research in bone tissue engineering, and related strategies have been extensively used for tendon, skull, cartilage, and bone regeneration. Also, alendronate, a well-recognized drug for osteoporosis treatment, has recently attracted a great deal of attention for bone repair. However, rapid corrosion in vivo of Mg2+ and low systemic bioavailability of alendronate are the main limitations hampering their full exploitation. In this work, by means of physical and chemical cross-linking conjugating magnesium-metal-organic frameworks (Mg-MOFs) and bone-targeting alendronate to biocompatible gelatin scaffolds, a facile method is developed for the preparation of organic/inorganic nanocomposite gel scaffolds. The results affirmed that the nanocomposite gel scaffolds possessed excellent biocompatibility, continuous slow release of Mg2+ and alendronate, strong bone affinity, and bone regeneration. It is noteworthy that the continuous slow release of Mg2+ and alendronate could induce the macrophage switch to the M2 phenotype and promote osteogenic differentiation in the early stage, resulting in improved bone regeneration during implanting the scaffolds into the distal femoral. In summary, Mg-MOFs-loaded alendronate-modified gelatin gel scaffolds have been developed, exhibiting great potential for bone regenerative.

Zn-Doped Calcium Magnesium Phosphate Bone Cement Based on Struvite and Its Antibacterial Properties

The development of magnesium calcium phosphate bone cements (MCPCs) has garnered substantial attention. MCPCs are bioactive and biodegradable and have appropriate mechanical and antimicrobial properties for use in reconstructive surgery. In this study, the cement powders based on a (Ca + Mg)/P = 2 system doped with Zn²⁺ at 0.5 and 1.0 wt.% were obtained and investigated. After mixing with a cement liquid, the structural and phase composition, morphology, chemical structure, setting time, compressive strength, degradation behavior, solubility, antibacterial activities, and in vitro behavior of the cement materials were examined. A high compressive strength of 48 ± 5 MPa (mean ± SD) was achieved for the cement made from Zn²⁺ 1.0 wt.%-substituted powders. Zn²⁺ introduction led to antibacterial activity against Staphylococcus aureus and Escherichia coli strains, with an inhibition zone diameter of up to 8 mm. Biological assays confirmed that the developed cement is cytocompatible and promising as a potential bone substitute in reconstructive surgery.

Magnesium for Implants: A Review on the Effect of Alloying Elements on Biocompatibility and Properties

An attempt is made to cover the whole of the topic of biodegradable magnesium (Mg) alloys with a focus on the biocompatibility of the individual alloying elements, as well as shed light on the degradation characteristics, microstructure, and mechanical properties of most binary alloys. Some of the various work processes carried out by researchers to achieve the alloys and their surface modifications have been highlighted. Additionally, a brief look into the literature on magnesium composites as also been included towards the end, to provide a more complete picture of the topic. In most cases, the chronological order of events has not been particularly followed, and instead, this work is concentrated on compiling and presenting an update of the work carried out on the topic of biodegradable magnesium alloys from the recent literature available to us.

Calcium Phosphate Cement Promotes Odontoblastic Differentiation of Dental Pulp Cells In Vitro and In Vivo

In the case of pulp injury, odontoblastic differentiation of dental pulp cells (DPCs) at the site of the exposed pulp is necessary for a successful direct pulp capping treatment. Calcium phosphate cement (CPC), a kind of hydroxyapatite-like bone cement, exhibits therapeutic potential in osteogenesis by regulating cell cycle progression and promoting osteoblastic differentiation. Based on the similar biological process of osteo/odontoblastic differentiation, the present study evaluated the effects of CPC on odontoblastic differentiation of DPCs in vitro and in vivo, respectively. The morphology of CPC was observed by scanning electron microscopy. Colony-forming units were used to assess the antibacterial activity. The effects of CPC on cell proliferation and odontoblastic differentiation of human dental pulp cells (hDPCs) were also measured. Histological staining was performed to observe the reparative dentin formation in rat molars. In vitro, results of antibacterial studies showed that CPC significantly inhibited the growth of Streptococcus mutans. The appropriate concentration of CPC extract showed low cytotoxicity on hDPCs. Furthermore, CPC extract also promoted odontoblastic differentiation and mineralization compared with the control group, as shown by a dynamic increase in the expression of odontogenic marker genes and the increased number of mineralized nodules at 21 days. The pulpotomy models with CPC facilitated the formation of dentin bridge with the highly expressed dentin matrix protein 1 (DMP1) in odontoblast-like cells. In conclusion, the favorable biocompatibility, antibacterial property and bio-inductivity of CPC suggest that CPC can be used as a promising direct pulp capping material.