Advances in the modification of injectable calcium-phosphate-based bone cements for clinical application

Magnesium-Based Composite Calcium Phosphate Cement Promotes Osteogenesis and Angiogenesis for Minipig Vertebral Defect Regeneration

Calcium phosphate cement (CPC) is an injectable bone cement with excellent biocompatibility, widely used for filling bone defects of various shapes. However, its slow degradation, insufficient mechanical strength, and poor osteoinductivity limit its further clinical applications. In this study, we developed a novel composite magnesium-based calcium phosphate cement by integrating magnesium microspheres into PLGA fibers obtained through wet spinning and incorporating these fibers into CPC. The inclusion of magnesium-based PLGA fibers enhanced the compressive strength and degradation rate of CPC, with the degradation rate of the magnesium microspheres being controllable to allow for the sustained release of magnesium ions. In vitro experiments showed that magnesium-based CPC enhanced the proliferation and migration of MC3T3-E1 and HUVECs. Additionally, the magnesium-based composite CPC not only enhanced osteogenic differentiation of MC3T3-E1 cells but also promoted angiogenesis in HUVECs. In vivo experiments using a vertebral bone defect model in Bama miniature pigs showed that the magnesium-based composite CPC significantly increased new bone formation. Additionally, compared to the CPC group, this composite exhibited significantly higher levels of osteogenic and angiogenic markers, with no inflammation or necrosis observed in the heart, liver, or kidneys, indicating good biocompatibility. These results suggest that magnesium-based composite CPC, with its superior compressive strength, biodegradability, and ability to promote vascularized bone regeneration, holds promise as a minimally invasive injectable material for bone regeneration.

Hybrid Bone Substitute Containing Tricalcium Phosphate and Silver Modified Hydroxyapatite-Methylcellulose Granules

Despite years of extensive research, achieving the optimal properties for calcium phosphate-based biomaterials remains an ongoing challenge. Recently, 'biomicroconcretes' systems consisting of setting-phase-forming bone cement matrix and aggregates (granules/microspheres) have been developed and studied. However, further investigations are necessary to clarify the complex interplay between the synthesis, structure, and properties of these materials. This article focusses on the development and potential applications of hybrid biomaterials based on alpha-tricalcium phosphate (αTCP), hydroxyapatite (HA) and methylcellulose (MC) modified with silver (0.1 wt.% or 1.0 wt.%). The study presents the synthesis and characterization of silver-modified hybrid granules and seeks to determine the possibility and efficiency of incorporating these hybrid granules into αTCP-based biomicroconcretes. The αTCP and hydroxyapatite provide structural integrity and osteoconductivity, the presence of silver imparts antimicrobial properties, and MC allows for the self-assembling of granules. This combination creates an ideal environment for bone regeneration, while it potentially may prevent bacterial colonization and infection. The material's chemical and phase composition, setting times, compressive strength, microstructure, chemical stability, and bioactive potential in simulated body fluid are systematically investigated. The results of the setting time measurements showed that both the size and the composition of granules (especially the hybrid nature) have an impact on the setting process of biomicroconcretes. The addition of silver resulted in prolonged setting times compared to the unmodified materials. Developed biomicroconcretes, despite exhibiting lower compressive strength compared to traditional calcium phosphate cements, fall within the range of human cancellous bone and demonstrate chemical stability and bioactive potential, indicating their suitability for bone substitution and regeneration. Further in vitro studies and in vivo assessments are needed to check the potential of these biomaterials in clinical applications.

A novel anti-washout curing solution of calcium phosphate cement prepared via irradiation polymerization

The anti-washout ability of calcium phosphate cement (CPC) determines its effectiveness in clinical application. In the current research, the common method for improving the anti-washout ability of CPC is to add anti-washout polymer agents. Sodium polyacrylate powder is an excellent anti-washout agent but when bonded with CPC it basically degrades the anti-washout performance of CPC after γ-ray irradiation, and is widely used in the sterilization process of CPC products. Therefore, we propose a method for the preparation of a sodium polyacrylate solution through irradiation polymerization as curing solution for CPC. This method first uses γ-ray irradiation sterilization to improve the anti-washout ability of CPC directly. It not only avoids the adverse effects of γ-rays on anti-washout agents, but also the CPC blended using this sodium polyacrylate solution had good biological properties and injectability. It provides a new method for promoting the anti-washout properties of calcium phosphate cement, which is of great significance for expanding the clinical application of CPC.

Calcium Phosphate Cements as Carriers of Functional Substances for the Treatment of Bone Tissue

Interest in calcium phosphate cements as materials for the restoration and treatment of bone tissue defects is still high. Despite commercialization and use in the clinic, the calcium phosphate cements have great potential for development. Existing approaches to the production of calcium phosphate cements as drugs are analyzed. A description of the pathogenesis of the main diseases of bone tissue (trauma, osteomyelitis, osteoporosis and tumor) and effective common treatment strategies are presented in the review. An analysis of the modern understanding of the complex action of the cement matrix and the additives and drugs distributed in it in relation to the successful treatment of bone defects is given. The mechanisms of biological action of functional substances determine the effectiveness of use in certain clinical cases. An important direction of using calcium phosphate cements as a carrier of functional substances is the volumetric incorporation of anti-inflammatory, antitumor, antiresorptive and osteogenic functional substances. The main functionalization requirement for carrier materials is prolonged elution. Various release factors related to the matrix, functional substances and elution conditions are considered in the work. It is shown that cements are a complex system. Changing one of the many initial parameters in a wide range changes the final characteristics of the matrix and, accordingly, the kinetics. The main approaches to the effective functionalization of calcium phosphate cements are considered in the review.

Sudoku of porous, injectable calcium phosphate cements - Path to osteoinductivity

With the increase of global population, people's life expectancy is growing as well. Humans tend to live more active lifestyles and, therefore, trauma generated large defects become more common. Instances of tumour resection or pathological conditions and complex orthopaedic issues occur more frequently increasing necessity for bone substitutes. Composition of calcium phosphate cements (CPCs) is comparable to the chemical structure of bone minerals. Their ability to self-set and resorb in vivo secures a variety of potential applications in bone regeneration. Despite the years-long research and several products already reaching the market, finding the right properties for calcium phosphate cement to be osteoinductive and both injectable and suitable for clinical use is still a sudoku. This article is focused on injectable, porous CPCs, reviewing the latest developments on the path toward finding osteoinductive material, which is suitable for injection.

The Effect of the Repair of Induced Articular Cartilage Defects in Pigs Using Calcium Phosphate Cement with Aminoacids on the Concentrations of Selected Inflammatory Markers and Serum Enzyme Activities

The repair of articular cartilage defects is an intensively developing area of research. Severe inflammatory reactions after surgical interventions on bones or their structures may lead to changes of bone or joint asymmetry. In laboratory diagnostics, some inflammatory biomarkers and serum enzymes are available for the evaluation of these inflammatory processes. A general understanding of inflammatory responses following the repair of cartilage defects is still lacking. The aim of this study was to describe the alterations in the values of five inflammatory markers and the activities of several enzymes in seven 5-month-old pigs within the first 30 days following the restoration of induced articular cartilage defects using the tetracalcium phosphate/nanomoneite cement powder enriched with amino acids (CAL). The reconstruction of surgically induced defects was accompanied by a significant increase of serum amyloid A (SAA, p < 0.05), haptoglobin (Hp, p < 0.001), C-reactive protein (CRP, p < 0.01), and pig major acute phase protein (pig-MAP, p < 0.001). Their concentrations decreased gradually within one-month post-surgery, the values recorded at the end of this period were higher than those obtained prior to surgery. The concentrations of α1-acid glycoprotein (AGP) showed no significant changes during the evaluated period. Alterations were also found in the enzyme activities of creatine kinase (p < 0.05), lactate-dehydrogenase and alkaline phosphatase (p < 0.01). These findings suggest that SAA, Hp, CRP and pig-MAP might be applicable biomarkers of acute phase response for the monitoring of postoperative period.