Injectable bone cements: What benefits the combination of calcium phosphates and bioactive glasses could bring?

Injectable double-crosslinked bone cement with enhanced bone adhesion and improved osteoporotic pathophysiological microenvironment for osteoregeneration in osteoporosis

The osteoporotic bone defect caused by excessive activity of osteoclasts has posed a challenge for public healthcare. However, most existing bioinert bone cement fails to effectively regulate the pathological bone microenvironment and reconstruct bone homeostasis in the presence of osteoclast overactivity and osteoblast suppression. Herein, inspired by natural bone tissue, an in-situ modulation system for osteoporotic bone regeneration is developed by fabricating an injectable double-crosslinked PEGylated poly(glycerol sebacate) (PEGS)/calcium phosphate cement (CPC) loaded with sodium alendronate (ALN) (PEGS/CPC@ALN) adhesive bone cement. By incorporating ALN, the organic-inorganic interconnection within PEGS/CPC@ALN results in a 100 % increase in compression modulus and energy dissipation efficiency. Additionally, PEGS/CPC@ALN effectively adheres to the bone by bonding with amine and calcium ions present on the bone surface. Moreover, this in-situ regulation system comprehensively mitigates excessive bone resorption through the buffering effect of CPC to improve the acidic microenvironment of osteoporotic bone and the release of ALN to inhibit hyperactive osteoclasts, and facilitates stem cell proliferation and differentiation into osteoblasts through calcium ion release. Overall, the PEGS/CPC@ALN effectively regulates the pathological microenvironment of osteoporosis while promoting bone regeneration through synergistic effects of drugs and materials, thereby improving bone homeostasis and enabling minimally invasive treatment for osteoporotic defects.

Injectable biocomposite cement: A dual-setting formula with magnesium potassium phosphate and κ-carrageenan hydrogel for orthopedic advancements

Magnesium phosphate-based cements are highly regarded for their bioactive properties, making them excellent candidates as bone substitutes. Despite their promising attributes, challenges such as high reaction temperature, limited injectability, and brittleness limit their application. This study introduces a dual-setting biocomposite cement, which encompasses both cement hydration and hydrogel's cross-linking. The composition features magnesium potassium phosphate (MKP) combined with ionically cross-linked kappa-carrageenan (kC) plasticized with sorbitol (Sor). The investigation delves into the properties of the resultant biocomposite, with a particular focus on evaluating kC incorporation's influence on the main MKP properties. Our findings reveal that those biocomposites offer multiple benefits over traditional ceramic cements. The main advantages include: a longer setting time (up to ~15 min), lower setting temperature (~45 °C), different crystalline phase (bobierrite), better wettability (~22°), and improved injectability of the paste characterized by more stable cohesion. Specifically, the MKP (4:1 Mg/P ratio) with 1.5 % kC and Sor hydrogel obtained with 3.0 g/mL powder-to-liquid ratio demonstrated the most promising properties with no adverse effects on the microstructure diversity, the mechanical strength, the porosity, the biodegradation rate, and the osteoblasts cytocompatibility. Overall, our research indicates that these innovative cements hold significant potential for biomedical applications, especially minimally invasive orthopedic procedures.

3D-Printed-Cryogel-Impregnated Functionalized Scaffold Augments Bone Regeneration in Critical Tibia Fracture in Goat

Critical-size bone trauma injuries present a significant clinical challenge because of the limited availability of autografts. In this study, a photocurable composite comprising of polycaprolactone, polypropylene fumarate, and nano-hydroxyapatite (nHAP) (P─P─H) is printed, which shows good osteoconduction in a rat model. A cryogel composed of gelatin-nHAP (GH) is developed to incorporate osteogenic components, specifically bone morphogenetic protein-2 (BMP-2) and zoledronic acid (ZA), termed as GH+B+Z, which is investigated for osteoinductive property in a rat model. Further, a 3D-printed P─P─H scaffold impregnated with GH+B+Z is designed and implanted in a critical-size defect (25 × 10 × 5 mm) in goat tibia. After 4 months, the scaffold is well-integrated with adjacent native bone, with osteoinduction observed in the cryogel-filled region and osteoconduction over the printed scaffold. X-ray radiography and micro-CT analysis showed bone in-growth in the treatment group with 45 ± 1.4% bone volume/tissue volume (BV/TV), while the defect remained unhealed in the control group with BV/TV of 10.5 ± 0.5%. Histology showed significant cell infiltration and matrix deposition over the printed P─P─H scaffold and within the GH cryogel site in the treatment group. Immunohistochemical staining depicted significantly higher normalized collagen I intensity in the treatment group (34.45 ± 2.61%) compared to the control group (4.22 ± 0.78).

A biodegradable magnesium phosphate cement incorporating chitosan and rhBMP-2 designed for bone defect repair

Background

The repair of bone defects has always been a significant challenge in clinical medicine. To address this challenge, doctors often utilize autologous bone grafts, allogeneic bone grafts and artificial bone substitutes. However, the former two methods may result in additional trauma and complications, while allogeneic bone grafts carry the risks of immune rejection and disease transmission. Magnesium phosphate cement (MPC), as a artificial bone substitutes, has been a potential biomaterial for repairing bone defects, but its clinical application is limited by insufficient mechanical strength and poor osteoinductive activity.

Methods

In this study, the cement liquid phase base on rhBMP-2 and chitosan solution into MPC 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, and cellular responses and bone regeneration in response to CHI-rhBMP2 MPC were investigated in vitro and in vivo.

Results

After the chemical component modification, CHI-rhBMP2 MPC possessed controllable degradation rate, moderate setting time, appropriate cuing temperature, good injectability, and improved initial strength. In vitro tests showed that the CHIrhBMP2 MPC could promote cell proliferation and adhesion, as well as that contribute to osteoblast differentiation and mineralization. In addition, cement materials were implanted into the rabbit femoral condyles for in vivo osseointegration evaluation. The results displayed that more new bone grew around CHI-rhBMP2 MPC, verifying improved osseointegration capacity. Transcriptome analysis revealed that focal adhesion, Forkhead box O（FoxO） signaling pathway and P13K/AKT signaling pathway were may involved in CHI-rhBMP2 MPC induced new bone formation.

Conclusion

This work provides a new strategy for the rational design of potential bone repair candidate materials.

Two decades of continuous progresses and breakthroughs in the field of bioactive ceramics and glasses driven by CICECO-hub scientists

Over the past two decades, the CICECO-hub scientists have devoted substantial efforts to advancing bioactive inorganic materials based on calcium phosphates and alkali-free bioactive glasses. A key focus has been the deliberate incorporation of therapeutic ions like Mg, Sr, Zn, Mn, or Ga to enhance osteointegration and vascularization, confer antioxidant properties, and impart antimicrobial effects, marking significant contributions to the field of biomaterials and bone tissue engineering. Such an approach is expected to circumvent the uncertainties posed by methods relying on growth factors, such as bone morphogenetic proteins, parathyroid hormone, and platelet-rich plasma, along with their associated high costs and potential adverse side effects. This comprehensive overview of CICECO-hub's significant contributions to the forefront inorganic biomaterials across all research aspects and dimensionalities (powders, granules, thin films, bulk materials, and porous structures), follows a unified approach rooted in a cohesive conceptual framework, including synthesis, characterization, and testing protocols. Tangible outcomes [injectable cements, durable implant coatings, and bone graft substitutes (scaffolds) featuring customized porous architectures for implant fixation, osteointegration, accelerated bone regeneration in critical-sized bone defects] were achieved. The manuscript showcases specific biofunctional examples of successful biomedical applications and effective translations to the market of bone grafts for advanced therapies.

Bone graft substitutes used in anterior lumbar interbody fusion: a contemporary systematic review of fusion rates and complications

Background

Anterior lumbar interbody fusion (ALIF) uses a broad-footprint interbody cage designed to maximize fusion rates for treating degenerative disc disease. Bone graft substitutes are being increasingly utilized during ALIF to replace or supplement autologous iliac crest bone grafts. This approach aims to optimize fusion efficacy while minimizing associated postoperative complications. The objective of this systematic review was to examine recent studies on fusion rates and postoperative complications associated with bone graft substitutes used in ALIF.

Methods

We conducted a systematic review of the Cumulative Index to Nursing and Allied Health Literature (CINAHL), Embase, MEDLINE, and PubMed databases, to critically examine a decade of research (January 1, 2012, to July 6, 2023) on the effectiveness and safety of various bone graft substitutes in ALIF. This timeframe was chosen to build on a previous systematic review published in 2013. The PRISMA guidelines were used.

Results

In total, 27 articles met our stringent inclusion and exclusion criteria. A substantial portion of these studies (67%) focused on recombinant human bone morphogenetic protein-2 (rhBMP-2) and highlighted its efficacy for achieving high fusion rates. However, the literature presents a dichotomy regarding the association of rhBMP-2 with increased postoperative complications. Notably, the methodologies for evaluating spinal fusion varied across studies. Only one-third of studies employed computed tomography to assess interbody fusion at 12 months postoperatively, highlighting the urgent need to establish uniform fusion criteria to facilitate more accurate comparative analyses. Moreover, there was considerable variability in the criteria used for diagnosing and detecting postoperative complications, significantly influencing the reported incidence rates.

Conclusions

This review underscores the need for continued research into bone graft substitutes, particularly focusing on assessment of long-term complications. Future research endeavors should concentrate on developing comprehensive clinical guidelines to aid in the selection of the most suitable bone graft substitutes for use in ALIF, thereby enhancing patient outcomes and surgical efficacy.

Polydopamine-coated bioactive glass for immunomodulation and odontogenesis in pulpitis

Preserving vital pulp in cases of dental pulpitis is desired but remains challenging. Previous research has shown that bioactive glass (BG) possesses notable capabilities for odontogenic differentiation. However, the immunoregulatory potential of BG for inflamed pulp is still controversial, which is essential for preserving vital pulp in the context of pulpitis. This study introduces a novel approach utilizing polydopamine-coated BG (BG-PDA) which demonstrates the ability to alleviate inflammation and promote odontogenesis for vital pulp therapy. In vitro, BG-PDA has the potential to induce M2 polarization of macrophages, resulting in decreased intracellular reactive oxygen species levels, inhibition of pro-inflammatory factor, and enhancement of anti-inflammatory factor expression. Furthermore, BG-PDA can strengthen the mitochondrial function in macrophages and facilitate odontogenic differentiation of human dental pulp cells. In a rat model of pulpitis, BG-PDA exhibits the capacity to promote M2 polarization of macrophages, alleviate inflammation, and facilitate dentin bridge formation. This study highlights the notable immunomodulatory and odontogenesis-inducing properties of BG-PDA for treating dental pulpitis, as evidenced by both in vitro and in vivo experiments. These results imply that BG-PDA could serve as a promising biomaterial for vital pulp therapy.

Enhancing bioactivity and mechanical performances of hydroxyapatite-calcium sulfate bone cements for bone repair: in vivo histological evaluation in rabbit femurs

This study deals with synthesizing hydroxyapatite-calcium sulfate bone cements or HAP-xCaS for bone repair. The effect of CaS on the setting time, injectability, washout resistance, phase evolution, water absorption, and physical, microstructural, and mechanical properties, as well as in vitro apatite-forming ability test and pH behavior of the HAP were investigated. Implantation of bone cement in rabbit femur and in vivo histological analysis were also analyzed. Initial and final setting times decrease with increasing CaS, which would be helpful for clinical procedures. All compositions have mixed phases of HAP, CaS, brushite, and gypsum. The prepared bone cement exhibited a dense structure and increased linear shrinkage with increasing CaS content. Adding more CaS inhibited grain growth and improved the mechanical properties, including compressive strength (σ c), bending strength (σ f), and Young's modulus (E). SEM micrographs displayed that the x = 0.7 or HAP-0.7CaS bone cement produced the highest ability to induce in vitro apatite formation, indicating its biocompatibility. In vivo histological analysis for the HAP-0.7CaS bone cement demonstrated that more new bone formed around defects and bone cement particles. Osteoblasts were found peripherally at the bone trabeculae, and occasional osteoblast-like cells were observed at the granules after 4-8 weeks of implantation. The obtained results indicated that the HAP-0.7CaS bone cement has the potential to exhibit good bioactivity, injectability, and good mechanical properties for bone repair applications.

Rheological Analysis and Evaluation of Measurement Techniques for Curing Poly(Methyl Methacrylate) Bone Cement in Vertebroplasty

Vertebroplasty is a minimally invasive surgical procedure used to treat vertebral fractures, which conventionally involves injecting poly(methyl methacrylate) (PMMA) bone cement into the fractured vertebra. A common risk associated with vertebroplasty is cement leaking out of the vertebra during the injection, which may occur due to a lack of understanding of the complex flow behavior. Therefore, experiments to quantify the cement's flow properties are necessary for understanding and proper handling of the bone cement. In this study, we aimed to characterize the behavior of PMMA bone cement in its curing stages to obtain parameters that govern the flow behavior during injection. We used rotational and oscillatory rheometry for our measurements, as well as a custom-made injector setup that replicated a typical vertebroplasty setting. Our results showed that the complex viscoelastic behavior of bone cement is significantly affected by deformations and temperature. We found that the results from rotational tests, often used for characterizing the bone cement, are susceptible to measurement artifacts caused by wall slip and "ridge"-like formations in the test sample. We also found the Cox-Merz rule to be conditionally valid, which affects the use of oscillatory tests to obtain the shear-thinning characteristics of bone cement. Our findings identify important differences in the measured flow behavior of PMMA bone cement when assessed by different rheological methods, an understanding that is crucial for its risk-free usage in downstream medical applications.

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.

Effects of liquid-to-solid ratio and gamma irradiation on the rheology and cytocompatibility of a beta-tricalcium phosphate-based injectable bone substitute

Injectable bone substitute (IBS) materials are commonly used to fill irregular-shaped bone voids in non-load-bearing areas and can offer greater utility over those which are in prefabricated powder, granule, or block forms. This work investigates the impact of liquid-to-solid ratio (LSR) on the rheology and cytocompatibility of IBSs formulated from bioactive glass particles and β-tricalcium phosphate (β-TCP) in glycerol and poly(ethylene glycol) (PEG). IBS formulations of varying LSR were prepared and packed in 3 cc open-bore syringes and sterilized via gamma irradiation (10 kGy, 25 kGy). Gamma-irradiated formulations with high PEG content required the highest (73 N) mechanical force for injection from syringes. Oscillatory viscosity measurements revealed that the viscosity of samples was directly proportional to glycerol content. PEG and glycerol displayed competing effects on the washout resistance and cohesiveness of samples, which were based on total weight loss in media and Ca2+ ion release, respectively. Cell viability in 24-h extracts of 10 kGy gamma-sterilized and 25 kGy gamma-irradiated samples were 22.94% and 56.53%, respectively. The research highlights the complex interplay of IBS components on IBS rheology and, moreover, the cytotoxicity behaviors of beta-tricalcium phosphate-based injectable bone substitutes by in vitro experiments.

Bioactive Moldable Click Chemistry Polymer Cement with Nano-Hydroxyapatite and Growth Factor-Enhanced Posterolateral Spinal Fusion in a Rabbit Model

Spinal injuries or diseases necessitate effective fusion solutions, and common clinical approaches involve autografts, allografts, and various bone matrix products, each with limitations. To address these challenges, we developed an innovative moldable click chemistry polymer cement that can be shaped by hand and self-cross-linked in situ for spinal fusion. This self-cross-linking cement, enabled by the bioorthogonal click reaction, excludes the need for toxic initiators or external energy sources. The bioactivity of the cement was promoted by incorporating nanohydroxyapatite and microspheres loaded with recombinant human bone morphogenetic protein-2 and vascular endothelial growth factor, fostering vascular induction and osteointegration. The release kinetics of growth factors, mechanical properties of the cement, and the ability of the scaffold to support in vitro cell proliferation and differentiation were evaluated. In a rabbit posterolateral spinal fusion model, the moldable cement exhibited remarkable induction of bone regeneration and effective bridging of spine vertebral bodies. This bioactive moldable click polymer cement therefore presents a promising biomaterial for spinal fusion augmentation, offering advantages in safety, ease of application, and enhanced bone regrowth.

Bone Cements Used in Vertebral Augmentation: A State-of-the-art Narrative Review

Vertebral compression fractures (VCFs) are common in osteoporotic patients, with a frequency projected to increase alongside a growing geriatric population. VCFs often result in debilitating back pain and decreased mobility. Cement augmentation, a minimally invasive surgical technique, is widely used to stabilize fractures and restore vertebral height. Acrylic-based cements and calcium phosphate cements are currently the two primary fill materials utilized for these procedures. Despite their effectiveness, acrylic bone cements and calcium phosphate cements have been associated with various intraoperative and postoperative incidents impacting VCF treatment. Over the past decade, discoveries in the field of biomedical engineering and material science have shown advancements toward addressing these limitations. This narrative review aims to assess the potential pitfalls and barriers of the various types of bone cements.

Limitations and modifications in the clinical application of calcium sulfate

Calcium sulfate and calcium sulfate-based biomaterials have been widely used in non-load-bearing bone defects for hundreds of years due to their superior biocompatibility, biodegradability, and non-toxicity. However, lower compressive strength and rapid degradation rate are the main limitations in clinical applications. Excessive absorption causes a sharp increase in sulfate ion and calcium ion concentrations around the bone defect site, resulting in delayed wound healing and hypercalcemia. In addition, the space between calcium sulfate and the host bone, resulting from excessively rapid absorption, has adverse effects on bone healing or fusion techniques. This issue has been recognized and addressed. The lack of sufficient mechanical strength makes it challenging to use calcium sulfate and calcium sulfate-based biomaterials in load-bearing areas. To overcome these defects, the introduction of various inorganic additives, such as calcium carbonate, calcium phosphate, and calcium silicate, into calcium sulfate is an effective measure. Inorganic materials with different physical and chemical properties can greatly improve the properties of calcium sulfate composites. For example, the hydrolysis products of calcium carbonate are alkaline substances that can buffer the acidic environment caused by the degradation of calcium sulfate; calcium phosphate has poor degradation, which can effectively avoid the excessive absorption of calcium sulfate; and calcium silicate can promote the compressive strength and stimulate new bone formation. The purpose of this review is to review the poor properties of calcium sulfate and its complications in clinical application and to explore the effect of various inorganic additives on the physicochemical properties and biological properties of calcium sulfate.

Regulation of the antibiotic elution profile from tricalcium phosphate bone cement by addition of bioactive glass

This work aimed at tailoring of different properties of antibacterial drug delivery Ca-phosphate cements by incorporation of bioactive glass (BG). The cements were prepared from beta-tricalcium phosphate cement (β-TCP) and BG based on 50 SiO2-20 CaO-15 Na2O-7 B2O3-4 P2O5-4 Al2O3 wt% with different percentages of BG [5, 10, 15, and 20% (w/w)]. The composite cements were characterized by XRD, FTIR, and TEM. Moreover, in vitro bioactivity and biodegradation were evaluated in the simulated body fluid (SBF) at 37 °C. In addition, physical properties and mechanical strength were determined. Also, the effect of glass addition on the drug release profile was examined using gentamicin. Finally, the antimicrobial activity was studied against Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumonia bacteria, one unicellular fungal strain (Candida albicans), and one multicellular fungal strain (Mucor racemosus). The results showed that after soaking in SBF, the compression strength values ranged from 14 to 36 MPa, the bulk densities and porosities were within 1.35 to 1.49 g/cm3 and 51.3 to 44.71%, respectively. Furthermore, gentamicin was released in a sustained manner, and BG decreased the released drug amount from ~ 80% (in pure β-TCP) to 47-53% in the composite cements. A drug release profile that is sustained by all samples was achieved. The antimicrobial test showed good activity of gentamicin-conjugated cements against bacteria and fungi used in this study. Additionally, cytotoxicity results proved that all samples were safe on MG-63 cells up to 50 µg/mL with no more than 7-12% dead cells. From the view of the physico-mechanical properties, bioactivity, biodegradation, and drug release rate, 20BG/β-TCP sample was nominated for practical bone grafting material, where it showed appropriate setting time and a relatively high mechanical strength suitable for cancellous bone.

Antioxidant flavonoid-loaded nano-bioactive glass bone paste: in vitro apatite formation and flow behavior

Non-cement pastes in the form of injectable materials have gained considerable attention in non-invasive regenerative medicine. Different osteoconductive bioceramics have been used as the solid phase of these bone pastes. Mesoporous bioactive glass can be used as an alternative bioceramic for paste preparation because of its osteogenic qualities. Plant-derived osteogenic agents can also be used in paste formulation to improve osteogenesis; however, their side effects on physical and physicochemical properties should be investigated. In this study, nano-bioactive glass powder was synthesized by a sol-gel method, loaded with different amounts of quercetin (0, 100, 150, and 200 μM), an antioxidant flavonoid with osteogenesis capacity. The loaded powder was then homogenized with a mixture of hyaluronic acid and sodium alginate solution to form a paste. We subsequently evaluated the rheological behavior, injectability, washout resistance, and in vitro bioactivity of the quercetin-loaded pastes. The washout resistance was found to be more than 96% after 14 days of immersion in simulated body fluid (SBF) as well as tris-buffered and citric acid-buffered solutions at 25 °C and 37 °C. All pastes exhibited viscoelastic behavior, in which the elastic modulus exceeded the viscous modulus. The pastes displayed shear-thinning behavior, in which viscosity was more influenced by angular frequency when the quercetin content increased. Results indicated that injectability was much improved using quercetin and the injection force was in the range 20-150 N. Following 14 days of SBF soaking, the formation of a nano-structured apatite phase on the surfaces of quercetin-loaded pastes was confirmed through scanning electron microscopy, X-ray diffractometry, and Fourier-transform infrared spectroscopy. Overall, quercetin, an antioxidant flavonoid osteogenic agent, can be loaded onto the nano-bioactive glass/hyaluronic acid/sodium alginate paste system to enhance injectability, rheological properties, and bioactivity.

Study on the poly(methyl methacrylate-acrylic acid)/calcium phosphate cement composite bound by chelation with enhanced water absorption and biomechanical properties

Polymethylmethacrylate (PMMA) bone cement has been widely used as a critical material for fixing prostheses and filling bone defects. The shrinkage of PMMA bone cement was addressed by the additives, however, the uneven integral water absorption and expansion performance as well as the deteriorated mechanical properties of the modified bone cement after immersion in phosphate buffered saline (PBS) and simulation body fluid (SBF) affected the long-term stability after implantation. Calcium phosphate cement (CPC) is a biomaterial with promising applications in orthopedics, whose hydration reaction provides an important driving force for the transfer of water. Besides, the mechanical properties of CPC can be enhanced with the curing process. In this study, CPC was utilized to modify the poly(methyl methacrylate-acrylic acid) [P(MMA-AA)] bone cement. The results demonstrated the successful construction of interconnected CPC water delivery networks in the P(MMA-AA)/CPC composite, the water absorption ratio and expansion ratio of the composite were up to 131.18 ± 9.14% and 168.19 ± 5.44%, respectively. Meanwhile, the transformation of CPC water delivery networks into rigid mechanical support networks as well as the chelation interaction between organic-inorganic enhanced the mechanical properties of the composite after immersion, the compressive strength after immersion reached 62.97 ± 0.97 MPa, which was 27.65% higher than that before immersion. The degradation ratio of the composite was up to 13.76 ± 0.23% after 9 days of immersion, which was 16.4% higher than that of CPC. Furthermore, composites exhibited superior biocompatibility as the release of Ca2+. Therefore, P(MMA-AA)/CPC composite serves as a promising medical filling material for clinical use.

Mechanism and application of 3D-printed degradable bioceramic scaffolds for bone repair

Bioceramics have attracted considerable attention in the field of bone repair because of their excellent osteogenic properties, degradability, and biocompatibility. To resolve issues regarding limited formability, recent studies have introduced 3D printing technology for the fabrication of bioceramic bone repair scaffolds. Nevertheless, the mechanisms by which bioceramics promote bone repair and clinical applications of 3D-printed bioceramic scaffolds remain elusive. This review provides an account of the fabrication methods of 3D-printed degradable bioceramic scaffolds. In addition, the types and characteristics of degradable bioceramics used in clinical and preclinical applications are summarized. We have also highlighted the osteogenic molecular mechanisms in biomaterials with the aim of providing a basis and support for future research on the clinical applications of degradable bioceramic scaffolds. Finally, new developments and potential applications of 3D-printed degradable bioceramic scaffolds are discussed with reference to experimental and theoretical studies.

Design and Manufacture of Bone Cements Based on Calcium Sulfate Hemihydrate and Mg, Sr-Doped Bioactive Glass

In the present study, a novel composite bone cement based on calcium sulfate hemihydrate (CSH) and Mg, Sr-containing bioactive glass (BG) as solid phase, and solution of chitosan as liquid phase were developed. The phase composition, morphology, setting time, injectability, viscosity, and cellular responses of the composites with various contents of BG (0, 10, 20, and 30 wt.%) were investigated. The pure calcium sulfate cement was set at approximately 180 min, whereas the setting time was drastically decreased to 6 min by replacing 30 wt.% glass powder for CSH in the cement solid phase. BG changed the microscopic morphology of the set cement and decreased the size and compaction of the precipitated gypsum phase. Replacing the CSH phase with BG increased injection force of the produced cement; however, all the cements were injected at a nearly constant force, lower than 20 N. The viscosity measurements in oscillatory mode determined the shear-thinning behavior of the pastes. Although the viscosity of the pastes increased with increasing BG content, it was influenced by the frequency extent. Pure calcium sulfate cement exhibited some transient cytotoxicity on human-derived bone mesenchymal stem cells and it was compensated by introducing BG phase. Moreover, BG improved the cell proliferation and mineralization of extracellular matrix as shown by calcein measurements. The results indicate the injectable composite cement comprising 70 wt.% CSH and 30 wt.% Mg, Sr-doped BG has better setting, mechanical and cellular behaviors and hence, is a potential candidate for bone repair, however more animal and human clinical evaluations are essential.

Comprehensive evaluation and advanced modification of polymethylmethacrylate cement in bone tumor treatment

Bone tumors are invasive diseases with a tendency toward recurrence, disability, and high mortality rates due to their grievous complications. As a commercial polymeric biomaterial, polymethylmethacrylate (PMMA) cement possesses remarkable mechanical properties, injectability, and plasticity and is, therefore, frequently applied in bone tissue engineering. Numerous positive effects in bone tumor treatment have been demonstrated, including biomechanical stabilization, analgesic effects, and tumor recurrence prevention. However, to our knowledge, a comprehensive evaluation of the application of the PMMA cement in bone tumor treatment has not yet been reported. This review comprehensively evaluates the efficiency and complications of the PMMA cement in bone tumor treatment, for the first time, and introduces advanced modification strategies, providing an objective and reliable reference for the application of the PMMA cement in treating bone tumors. We have also summarized the current research on modifications to enhance the anti-tumor efficacy of the PMMA cement, such as drug carriers and magnetic hyperthermia.

Functionally Tailored Metal-Organic Framework Coatings for Mediating Ti Implant Osseointegration

Owing to their mechanical resilience and non-toxicity, titanium implants are widely applied as the major treatment modality for the clinical intervention against bone fractures. However, the intrinsic bioinertness of Ti and its alloys often impedes the effective osseointegration of the implants, leading to severe adverse complications including implant loosening, detachment, and secondary bone damage. Consequently, new Ti implant engineering strategies are urgently needed to improve their osseointegration after implantation. Remarkably, metalorganic frameworks (MOFs) are a class of novel synthetic material consisting of coordinated metal species and organic ligands, which have demonstrated a plethora of favorable properties for modulating the interfacial properties of Ti implants. This review comprehensively summarizes the recent progress in the development of MOF-coated Ti implants and highlights their potential utility for modulating the bio-implant interface to improve implant osseointegration, of which the discussions are outlined according to their physical traits, chemical composition, and drug delivery capacity. A perspective is also provided in this review regarding the current limitations and future opportunities of MOF-coated Ti implants for orthopedic applications. The insights in this review may facilitate the rational design of more advanced Ti implants with enhanced therapeutic performance and safety.

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.

Advances and Prospects in Materials for Craniofacial Bone Reconstruction

The craniofacial region is composed of 23 bones, which provide crucial function in keeping the normal position of brain and eyeballs, aesthetics of the craniofacial complex, facial movements, and visual function. Given the complex geometry and architecture, craniofacial bone defects not only affect the normal craniofacial structure but also may result in severe craniofacial dysfunction. Therefore, the exploration of rapid, precise, and effective reconstruction of craniofacial bone defects is urgent. Recently, developments in advanced bone tissue engineering bring new hope for the ideal reconstruction of the craniofacial bone defects. This report, presenting a first-time comprehensive review of recent advances of biomaterials in craniofacial bone tissue engineering, overviews the modification of traditional biomaterials and development of advanced biomaterials applying to craniofacial reconstruction. Challenges and perspectives of biomaterial development in craniofacial fields are discussed in the end.

Advanced Bioactive Glasses: The Newest Achievements and Breakthroughs in the Area

Bioactive glasses (BGs) are especially useful materials in soft and bone tissue engineering and even in dentistry. They can be the solution to many medical problems, and they have a huge role in the healing processes of bone fractures. Interestingly, they can also promote skin regeneration and wound healing. Bioactive glasses are able to attach to the bone tissues and form an apatite layer which further initiates the biomineralization process. The formed intermediate apatite layer makes a connection between the hard tissue and the bioactive glass material which results in faster healing without any complications or side effects. This review paper summarizes the most recent advancement in the preparation of diverse types of BGs, such as silicate-, borate- and phosphate-based bioactive glasses. We discuss their physical, chemical, and mechanical properties detailing how they affect their biological performances. In order to get a deeper insight into the state-of-the-art in this area, we also consider their medical applications, such as bone regeneration, wound care, and dental/bone implant coatings.

Degradation and Bone-Contact Biocompatibility of Two Drillable Magnesium Phosphate Bone Cements in an In Vivo Rabbit Bone Defect Model

The use of bone-cement-enforced osteosynthesis is a growing topic in trauma surgery. In this context, drillability is a desirable feature for cements that can improve fracture stability, which most of the available cement systems lack. Therefore, in this study, we evaluated a resorbable and drillable magnesium-phosphate (MgP)-based cement paste considering degradation behavior and biocompatibility in vivo. Two different magnesium-phosphate-based cement (MPC) pastes with different amounts of phytic acid (IP 6) as setting retarder (MPC 22.5 and MPC 25) were implanted in an orthotopic defect model of the lateral femoral condyle of New Zealand white rabbits for 6 weeks. After explantation, their resorption behavior and material characteristics were evaluated by means of X-ray diffraction (XRD), porosimetry measurement, histological staining, peripheral quantitative computed tomography (pQCT), cone-beam computed tomography (CBCT) and biomechanical load-to-failure tests. Both cement pastes displayed comparable results in mechanical strength and resorption kinetics. Bone-contact biocompatibility was excellent without any signs of inflammation. Initial resorption and bone remodeling could be observed. MPC pastes with IP 6 as setting retardant have the potential to be a valuable alternative in distinct fracture patterns. Drillability, promising resorption potential and high mechanical strength confirm their suitability for use in clinical routine.

Synthesis and Characterization of Nano-Hydroxyapatite Obtained from Eggshell via the Hydrothermal Process and the Precipitation Method

Hydroxyapatite (HA) is a major component of the inorganic minerals in the hard tissues of humans and has been widely used as a biomedical ceramic material in orthopedic and dentistry applications. Because human bone contains several impurities, including carbonates, chlorides, fluorides, magnesium, and strontium, human bone minerals differ from stoichiometric HA. Additionally, natural bone is composed of nano-sized HA, and the nanoscale particles exhibit a high level of biological activity. In this paper, HA is prepared via the hydrothermal process because its reaction conditions are easy to control and it has been shown to be quite feasible for large-scale production. Therefore, the hydrothermal process is an effective and convenient method for the preparation of HA. Furthermore, eggshell is adopted as a source of calcium, and mulberry leaf extract is selectively added to synthesize HA. The eggshell accounts for 11% of the total weight of a whole egg, and it consists of calcium carbonate, calcium phosphate, magnesium carbonate, and organic matter. Eggshell contains a variety of trace elements, such as magnesium and strontium, making the composition of the synthesized HA similar to that of the human skeleton. These trace elements exert considerable benefits for bone growth. Moreover, the use of eggshell as a raw material can permit the recycling of biowaste and a reduction in process costs. The purpose of this study is to prepare HA powder via the hydrothermal method and to explore the effects of hydrothermal conditions on the structure and properties of the synthesized HA. The room-temperature precipitation method is used for the control group. Furthermore, the results of an immersion test in simulated body fluid confirm that the as-prepared HA exhibits good apatite-forming bioactivity, which is an essential requirement for artificial materials to bond to living bones in the living body and promote bone regeneration. In particular, it is confirmed that the HA synthesized with the addition of the mulberry leaf extract exhibits good in vitro biocompatibility. The morphology, crystallite size, and composition of the carbonated nano-HA obtained herein are similar to those of natural bones. The carbonated nano-HA appears to be an excellent material for bioresorbable bone substitutes or drug delivery. Therefore, the nano-HA powder prepared in this study has great potential in biomedical applications.

Synergistic effect of drug/antibiotic-impregnated micro/nanohybrid mesoporous bioactive glass/calcium phosphate composite bone cement on antibacterial and osteoconductive activities

Calcium phosphate bone cements (CPC) can be used in minimally invasive surgery because of their injectability, and they can also be used to repair small and irregular bone defects. This study aimed to release the antibiotic gentamicin sulfate (Genta) to reduce tissue inflammation and prevent infection in the early stages of bone recovery. Subsequently, the sustained release of the bone-promoting drug ferulic acid (FA) mimicked the response of osteoprogenitor D1 cells interaction, thereby accelerating the healing process of the overall bone repair. Accordingly, the different particle properties of micro-nano hybrid mesoporous bioactive glass (MBG), namely, micro-sized MBG (mMBG) and nano-sized MBG (nMBG), were explored separately to generate different dose releases in MBG/CPC composite bone cement. Results show that nMBG had better sustained-release ability than mMBG when impregnated with the same dose. When 10 wt% of mMBG hybrid nMBG and composite CPC were used, the amount of MBG slightly shortened the working/setting time and lowered the strength but did not hinder the biocompatibility, injectability, anti-disintegration, and phase transformation of the composite bone cement. Furthermore, compared with 2.5wt%Genta@mMBG/7.5 wt% FA@nMBG/CPC, 5wt.%Genta@mMBG/5wt.%FA@nMBG/CPC exhibited better antibacterial activity, better compressive strength, stronger mineralization of osteoprogenitor cell, and similar 14-day slow-release trend of FA. The MBG/CPC composite bone cement developed can be used in clinical surgery to achieve the synergistic sustained release of antibacterial and osteoconductive activities.

Advanced applications of strontium-containing biomaterials in bone tissue engineering

Strontium (Sr) and strontium ranelate (SR) are commonly used therapeutic drugs for patients suffering from osteoporosis. Researches have showed that Sr can significantly improve the biological activity and physicochemical properties of materials in vitro and in vivo. Therefore, a large number of strontium containing biomaterials have been developed for repairing bone defects and promoting osseointegration. In this review, we provide a comprehensive overview of Sr-containing biomaterials along with the current state of their clinical use. For this purpose, the different types of biomaterials including calcium phosphate, bioactive glass, and polymers are discussed and provided future outlook on the fabrication of the next-generation multifunctional and smart biomaterials.

Enhanced Cell Osteogenic Differentiation in Alendronate Acid and Flufenamic Acid Drug-Impregnated Nanoparticles of Mesoporous Bioactive Glass Composite Calcium Phosphate Bone Cement In Vitro

This study aims to compare the anti-osteoporotic drugs alendronic acid (ALN) and flufenamic acid (FA) alone impregnate into nanoparticles of mesoporous bioactive glass (nMBG), which further composites calcium phosphate cement (CPC) and investigates their in vitro performance. The drug release, physicochemical properties, and biocompatibility of nMBG@CPC composite bone cement are tested, and the effect of the composites on improving the proliferation and differentiation efficiency of mouse precursor osteoblasts (D1 cells) is also investigated. Drug release shows that FA impregnates nMBG@CPC composite, a large amount of FA is released rapidly within 8 h, gradually reaching a stable release within 12 h, followed by a slow and sustained release within 14 days, and then reaches a plateau within 21 days. The release phenomenon confirms that the drug-impregnated nBMG@CPC composite bone cement effectively achieves slow drug delivery. The working time and setting time of each composite are within 4-10 min and 10-20 min, respectively, meeting the operational requirements of clinical applications. The addition of nMBG nanoparticles in the CPC matrix did not prevent the aggregation phenomenon under microstructural observation, thus resulting in a decrease in the strength of the nMBG@CPC composite. However, after 24 h of immersed reaction, the strength of each 5 wt.% nMBG impregnated with different concentrations of FA and ALN is still greater than 30 MPa, which is higher than the general trabecular bone strength. The drug-impregnated nMBG@CPC composites did not hinder the product formation and exhibit biocompatibility. Based on the proliferation and mineralization of D1 cells, the combination of nMBG with abundant FA and ALN in CPC is not conducive to the proliferation of D1 cells. However, when D1 cells are contact cultured for 21 days, alkaline phosphatase (ALP) enzyme activity shows higher ALP secretion from drug-impregnated nMBG@CPC composites than drug-free composites. Accordingly, this study confirms that nMBG can effectively impregnate the anti-osteoporosis drugs FA and ALN, and enhance the mineralization ability of osteoblasts. Furthermore, drug-impregnated nMBG applications can be used alone or in combination with CPC as a new option for osteoporotic bone-filling surgery.

Injectable Bone Cement Reinforced with Gold Nanodots Decorated rGO-Hydroxyapatite Nanocomposites, Augment Bone Regeneration

Interest in the development of new generation injectable bone cements having appropriate mechanical properties, biodegradability, and bioactivity has been rekindled with the advent of nanoscience. Injectable bone cements made with calcium sulfate (CS) are of significant interest, owing to its compatibility and optimal self-setting property. Its rapid resorption rate, lack of bioactivity, and poor mechanical strength serve as a deterrent for its wide application. Herein, a significantly improved CS-based injectable bone cement (modified calcium sulfate termed as CS_mod ), reinforced with various concentrations (0-15%) of a conductive nanocomposite containing gold nanodots and nanohydroxyapatite decorated reduced graphene oxide (rGO) sheets (AuHp@rGO), and functionalized with vancomycin, is presented. The piezo-responsive cement exhibits favorable injectability and setting times, along with improved mechanical properties. The antimicrobial, osteoinductive, and osteoconductive properties of the CS_mod cement are confirmed using appropriate in vitro studies. There is an upregulation of the paracrine signaling mediated crosstalk between mesenchymal stem cells and human umbilical vein endothelial cells seeded on these cements. The ability of CS_mod to induce endothelial cell recruitment and augment bone regeneration is evidenced in relevant rat models. The results imply that the multipronged activity exhibited by the novel-CS_mod cement would be beneficial for bone repair.

A Brief Review on Selected Applications of Hybrid Materials Based on Functionalized Cage-like Silsesquioxanes

Rapid developments in materials engineering are accompanied by the equally rapid development of new technologies, which are now increasingly used in various branches of our life. The current research trend concerns the development of methods for obtaining new materials engineering systems and searching for relationships between the structure and physicochemical properties. A recent increase in the demand for well-defined and thermally stable systems has highlighted the importance of polyhedral oligomeric silsesquioxane (POSS) and double-decker silsesquioxane (DDSQ) architectures. This short review focuses on these two groups of silsesquioxane-based materials and their selected applications. This fascinating field of hybrid species has attracted considerable attention due to their daily applications with unique capabilities and their great potential, among others, in biomaterials as components of hydrogel networks, components in biofabrication techniques, and promising building blocks of DDSQ-based biohybrids. Moreover, they constitute attractive systems applied in materials engineering, including flame retardant nanocomposites and components of the heterogeneous Ziegler-Natta-type catalytic system.

Porous phosphate-based bioactive glass /β-TCP scaffold for tooth remineralization

The total or partial loss of teeth in the Mexican population due to periodontal diseases and trauma causes the development of other conditions, such as limitations in chewing and grinding food, pronunciation difficulties, and oral aesthetic alterations. In Mexico, oral diseases have been described to affect 87% of the population, according to reports by the health services, emphasizing that pregnant women and patients with diabetes mellitus have the highest risk of presenting with severe periodontal diseases or tooth loss, according to findings by the Mexican Health Department's Specific Action Program for the prevention, detection, and control of oral health problems (2013-2018). There was a 92.6% prevalence of dental caries in the population examined, and the prevalence of periodontal problems, mainly in 40-year-olds, was above 95%. The objective of this investigation was to manufacture and characterize porous 3D scaffolds with innovative chemical compositions, using phosphate-based bioactive glass, beta-phase tricalcium phosphate, and zirconium oxide, in variable quantities. The scaffold manufacturing method combined two techniques: powder metallurgy and polymer foaming. The results obtained in this research were promising since the mechanically tested scaffolds showed values of compressive strength and modulus of elasticity in the range of human trabecular bone. On the other hand, the in vitro evaluation of the samples immersed in artificial saliva at days 7 and 14 presented the calcium/phosphorus ratio = 1.6; this value is identical to the reported state-of-the-art figure, corresponding to the mineral phase of the bones and teeth. Likewise, the precipitation of the flower-like morphology was observed on the entire surface of the scaffold without zirconia; this morphology is characteristic of hydroxyapatite. On the other hand, the samples with 0.5 and 1.0 mol% zirconia showed less hydroxyapatite formation, with a direct correlation between scaffold dissolution and the amount of zirconia added.

Injectability, Processability, Drug Loading, and Antibacterial Activity of Gentamicin-Impregnated Mesoporous Bioactive Glass Composite Calcium Phosphate Bone Cement In Vitro

Calcium phosphate cement (CPC) is similar to bone in composition and has plasticity, while mesoporous bioactive glass (MBG) has the advantage of releasing Si, which can promote osteogenic properties and drug loading capacity. A sol–gel-prepared MBG micro-powder (mMBG) and further impregnated antibiotic gentamicin sulfate (Genta@mMBG: 2, 3, and 4 mg/mL) antibiotic were added to CPC at different weight ratios (5, 10, and 15 wt.%) to study CPC’s potential clinical applications. Different ratios of mMBG/CPC composite bone cement showed good injectability and disintegration resistance, but with increasing mMBG addition, the working/setting time and compressive strength decreased. The maximum additive amount was 10 wt.% mMBG due to the working time of ~5 min, the setting time of ~10 min, and the compressive strength of ~51 MPa, indicating that it was more suitable for clinical surgical applications than the other groups. The 2Genta@mMBG group loaded with 2 mg/mL gentamicin had good antibacterial activity, and the 10 wt.% 2Genta@mMBG/CPC composite bone cement still had good antibacterial activity but reduced the initial release of Genta. 2Genta@mMBG was found to have slight cytotoxicity, so 2Genta@mMBG was composited into CPC to improve the biocompatibility and to endow CPC with more advantages for clinical application.

Magnetic bioactive glass nano-heterostructures: a deeper insight into magnetic hyperthermia properties in the scope of bone cancer treatment

Primary bone cancers commonly involve surgery to remove the malignant tumor, complemented with a postoperative treatment to prevent cancer resurgence. Studies on magnetic hyperthermia, used as a single treatment or in synergy with chemo- or radiotherapy, have shown remarkable success in the past few decades. Multifunctional biomaterials with bone healing ability coupled with hyperthermia property could thus be of great interest to repair critical bone defects resulting from tumor resection. For this purpose, we designed superparamagnetic and bioactive nanoparticles (NPs) based on iron oxide cores (γ-Fe₂O₃) encapsulated in a bioactive glass (SiO₂-CaO) shell. Nanometric heterostructures (122 ± 12 nm) were obtained through a two-step process: co-precipitation of 16 nm sized iron oxide NPs, followed by the growth of a bioactive glass shell via a modified Stöber method. Their bioactivity was confirmed by hydroxyapatite growth in simulated body fluid, and cytotoxicity assays showed they induced no significant death of human mesenchymal stem cells after 7 days. Calorimetric measurements were carried out under a wide range of alternating magnetic field amplitudes and frequencies, considering clinically relevant parameters, and some were made in viscous medium (agar) to mimic the implantation conditions. The experimental specific loss power was predictable with respect to the Linear Response Theory, and showed a maximal value of 767 ± 77 W g_Fe^-1 (769 kHz, 23.9 kA m^-1 in water). An interesting value of 166 ± 24 W g_Fe^-1 was obtained under clinically relevant conditions (157 kHz, 23.9 kA m^-1) for the heterostructures immobilized in agar. The good biocompatibility, bioactivity and heating ability suggest that these γ-Fe₂O₃@SiO₂-CaO NPs are a promising biomaterial to be used as it is or included in a scaffold to heal bone defects resulting from bone tumor resection.

Highly bioactive bone cement microspheres based on α-tricalcium phosphate microparticles/mesoporous bioactive glass nanoparticles: Formulation, physico-chemical characterization and in vivo bone regeneration

Calcium phosphate cement (CPC) is a self-setting, biocompatible and osteoconductive bone cement, however its use as a bone substitute is still limited owing to its low bioactivity (i.e. its slow in vivo resorption and slow new bone formation rate) which is a challenging issue to be addressed. Herein, we report for the first time highly bioactive bone cement microspheres formulated from a cement paste containing α-tricalcium phosphate microparticles (α-TCP) and mesoporous calcium silicate bioactive glass nanoparticles (mesoporous BGn) using a water-in-oil emulsion method. Indeed, bioactive microspheres possess high potential as bone defect fillers for bone regeneration. The α-TCP microparticles were prepared by a solid state synthesis at 1400 ºC while mesoporous BGn were synthesized by template-assissted ultrasound-mediated sol-gel method. The particle size distribution of as-prepared cement microspheres was in the range of 200 - 450 µm with a sphericity index in the range of 0.92 - 0.94. The surface morphology of α-TCP microspheres revealed α-TCP micoparticles with smooth surfaces whereas α-TCP/BGn microspheres unveiled nano-roughened α-TCP microparticles. The as-prepared α-TCP/BGn cement microspheres exhibited larger specific surface area ca 18.6 m²/g, sustained release of soluble silicate (SiO₄^4-) ions (118 ppm within a week) and high protein adsorption capacity (252 mg/g). Notably, the α-TCP/BGn cement microspheres showed excellent in vitro surface bioactivity via formation of massive amounts of bone-like hydroxyapatite spherules and aggregates on their surfaces after soaking in simulated body fluid. Importantly, the in vivo implantation of as-prepared α-TCP/BGn cement microspheres in rat calvarial critical size bone defects for 6 weeks unveiled high in vivo bioactivity in terms of substantial new bone ingrowth and significant new bone formation within the bone defect as evidenced by histological analyses, X-ray radiography and micro-computed tomography evaluations.