The Regenerative Applicability of Bioactive Glass and Beta-Tricalcium Phosphate in Bone Tissue Engineering: A Transformation Perspective

3D printing of bacterial poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/poly(lactide-co-glycolide) blend loaded with β-tricalcium phosphate for the development of scaffolds to support human mesenchymal stromal cell proliferation

Polyhydroxyalkanoates (PHAs) are microbially produced aliphatic polyesters investigated for tissue engineering thanks to their biocompatibility, processability, and suitable mechanical properties. Taking advantage of these properties, the present study investigates the development by 3D printing of bacterial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) scaffolds loaded with β-tricalcium phosphate (β-TCP) for bone tissue regeneration. PHBV blending with poly(lactide-co-glycolide) (PLGA) (30 wt%) was exploited to enhance material processability via an optimized computer-aided wet-spinning approach. In particular, PHBV/PLGA blends were loaded with different β-TCP percentages (up to 15 wt%) by suspending the ceramic particles into the polymeric solution. The composite materials were successfully fabricated into 3D scaffolds with a fully interconnected porous architecture, as demonstrated by scanning electron microscopy. The ceramic phase had a significant effect on PHBV crystallization as shown by differential scanning calorimetry, as well as on scaffold mechanical properties with a significant increase of compressive modulus in the case of 5 wt% β-TCP loading. In addition, in vitro cell culture experiments demonstrated that β-TCP loading led to a significant increase of the viability of human mesenchymal stem/stromal cells grown on the scaffolds. Taken together, our data suggest that microbial PHBV processability, biomechanical performance, and bioactivity can be improved through combined PLGA blending and β-TCP loading.

Triple-Combination Therapy with a Multifunctional Yolk-Shell Nanozyme Au@CeO2 Loaded with Dimethyl Fumarate for Periodontitis

Periodontitis, a chronic inflammatory disease, is the leading cause of tooth loss in adults and is one of the most prevalent and complex oral conditions. Oxidative stress induced by the excessive generation of reactive oxygen species (ROS) leads to periodontitis, which is closely associated with pathological processes, including mitochondrial dysfunction of periodontal cells and local immune dysregulation. However, current treatment modalities that target single pathological processes have limited long-term therapeutic effects. Herein, a multifunctional Yolk-Shell nanozyme, Au@CeO2-dimethyl fumarate (DMF), which comprehensively addresses the oxidative stress-induced pathophysiological processes of periodontitis through antioxidant activity, mitochondrial maintenance, and immune modulation mechanisms, is described. For material design logic, functionally complementary Au and CeO2 formed an excellent photothermally regulated high-efficiency nanozyme, which also provided an ideal drug carrier for DMF. As for the therapeutic logic, Au@CeO2-DMF restores mitochondrial dysfunction and immune dysregulation, which also contributes to endogenous ROS elimination, thereby achieving long-term stable therapeutic effects. In a rat model, local Au@CeO2-DMF photothermal therapy effectively alleviated ROS-induced tissue damage and restored periodontal homeostasis. Altogether, this study presents a novel antioxidant nanozyme for managing alveolar bone loss under prolonged oxidative stress and demonstrates the importance of comprehensive intervention in key pathological processes in periodontitis treatment design.

β-Tricalcium phosphate incorporated natural rubber latex membranes for calvarial bone defects: Physicochemical, in vitro and in vivo assessment

Natural rubber latex membrane (NRL) is a biocompatible macromolecule that stimulates angiogenesis and promotes bone repair. Similarly, β-tricalcium phosphate (β-TCP) is an osteoconductive and osteoinductive bioceramic widely used as a bone substitute. Here, we investigated the combined use of these biomaterials in the guided bone regeneration process for calvarial defects in rats. Physicochemical characterization was performed to evaluate the interaction between β-TCP and NRL. Membrane toxicity was assessed using MC3T3 osteoblasts culture and in vivo assays with Caenorhabditis elegans. Lastly, NRL membranes, NRL incorporated with β-TCP membranes (NRL-β-TCP), and a periosteum-only (control group) were tested on rodents. MC3T3 cells adhered to membranes, preserving their morphology and intercellular connections. NRL-β-TCP membranes demonstrated no toxicity in larvae, which maintained their sinusoidal wave shape. Tests results on rodents revealed statistical difference between the groups at 60 days post-operation. NRL-β-TCP (56.1 ± 14.0 %) had an average 1.48-fold higher than the control group (38.0 ± 9.1 %), with tissue production and bone remodeling. Our qualitative histological analyses revealed that membranes significantly accelerated bone formation without any signs of inflammatory reactions. We conclude that NRL-β-TCP has potential to be used for flat bone regeneration, with osteoconductive properties, being a cheap, biocompatible, and effective occlusive barrier.

Chitosan Scaffolds from Crustacean and Fungal Sources: A Comparative Study for Bone-Tissue-Engineering Applications

Chitosan (CS), a biopolymer, holds significant potential in bone regeneration due to its biocompatibility and biodegradability attributes. While crustacean-derived CS is conventionally used in research, there is growing interest in fungal-derived CS for its equally potent properties in bone regenerative applications. Here, we investigated the physicochemical and biological characteristics of fungal (MDC) and crustacean (ADC)-derived CS scaffolds embedded with different concentrations of tricalcium phosphate minerals (TCP), i.e., 0(wt)%: ADC/MDC-1, 10(wt)%: ADC/MDC-2, 20(wt)%: ADC/MDC-3 and 30(wt)%: ADC/MDC-4. ADC-1 and MDC-1 lyophilised scaffolds lacking TCP minerals presented the highest zeta potentials of 47.3 ± 1.2 mV and 55.1 ± 1.6 mV, respectively. Scanning electron microscopy revealed prominent distinctions whereby MDC scaffolds exhibited striation-like structural microarchitecture in contrast to the porous morphology exhibited by ADC scaffold types. With regard to the 4-week scaffold mass reductions, MDC-1, MDC-2, MDC-3, and MDC-4 indicated declines of 55.98 ± 4.2%, 40.16 ± 3.6%, 27.05 ± 4.7%, and 19.16 ± 5.3%, respectively. Conversely, ADC-1, ADC-2, ADC-3, and ADC-4 presented mass reductions of 35.78 ± 5.1%, 25.19 ± 4.2%, 20.23 ± 6.3%, and 13.68 ± 5.4%, respectively. The biological performance of the scaffolds was assessed through in vitro bone marrow mesenchymal stromal cell (BMMSCs) attachment via indirect and direct cytotoxicity studies, where all scaffold types presented no cytotoxic behaviours. MDC scaffolds indicated results comparable to ADC, where both CS types exhibited similar physiochemical properties. Our data suggest that MDC scaffolds could be a potent alternative to ADC-derived scaffolds for bone regeneration applications, particularly for 10(wt)% TCP concentrations.

Use of Biomaterials in 3D Printing as a Solution to Microbial Infections in Arthroplasty and Osseous Reconstruction

The incidence of microbial infections in orthopedic prosthetic surgeries is a perennial problem that increases morbidity and mortality, representing one of the major complications of such medical interventions. The emergence of novel technologies, especially 3D printing, represents a promising avenue of development for reducing the risk of such eventualities. There are already a host of biomaterials, suitable for 3D printing, that are being tested for antimicrobial properties when they are coated with bioactive compounds, such as antibiotics, or combined with hydrogels with antimicrobial and antioxidant properties, such as chitosan and metal nanoparticles, among others. The materials discussed in the context of this paper comprise beta-tricalcium phosphate (β-TCP), biphasic calcium phosphate (BCP), hydroxyapatite, lithium disilicate glass, polyetheretherketone (PEEK), poly(propylene fumarate) (PPF), poly(trimethylene carbonate) (PTMC), and zirconia. While the recent research results are promising, further development is required to address the increasing antibiotic resistance exhibited by several common pathogens, the potential for fungal infections, and the potential toxicity of some metal nanoparticles. Other solutions, like the incorporation of phytochemicals, should also be explored. Incorporating artificial intelligence (AI) in the development of certain orthopedic implants and the potential use of AI against bacterial infections might represent viable solutions to these problems. Finally, there are some legal considerations associated with the use of biomaterials and the widespread use of 3D printing, which must be taken into account.

Recent Developments in Nanoparticle Formulations for Resveratrol Encapsulation as an Anticancer Agent

Resveratrol is a polyphenolic compound that has gained considerable attention in the past decade due to its multifaceted therapeutic potential, including anti-inflammatory and anticancer properties. However, its anticancer efficacy is impeded by low water solubility, dose-limiting toxicity, low bioavailability, and rapid hepatic metabolism. To overcome these hurdles, various nanoparticles such as organic and inorganic nanoparticles, liposomes, polymeric nanoparticles, dendrimers, solid lipid nanoparticles, gold nanoparticles, zinc oxide nanoparticles, zeolitic imidazolate frameworks, carbon nanotubes, bioactive glass nanoparticles, and mesoporous nanoparticles were employed to deliver resveratrol, enhancing its water solubility, bioavailability, and efficacy against various types of cancer. Resveratrol-loaded nanoparticle or resveratrol-conjugated nanoparticle administration exhibits excellent anticancer potency compared to free resveratrol. This review highlights the latest developments in nanoparticle-based delivery systems for resveratrol, focusing on the potential to overcome limitations associated with the compound's bioavailability and therapeutic effectiveness.

A Human Whole Blood Culture System Reveals Detailed Cytokine Release Profiles of Implant Materials

Introduction

Common in vitro cell culture systems for testing implant material immune compatibility either rely on immortal human leukocyte cell lines or isolated primary cells. Compared to in vivo conditions, this generates an environment of substantially reduced complexity, often lacking important immune cell types, such as neutrophil granulocytes and others. The aim of this study was to establish a reliable test system for in vitro testing of implant materials under in vivo-like conditions.

Methods

Test materials were incubated in closed, CO2-independent, tube-based culture vessels containing a proprietary cell culture medium and human whole blood in either a static or occasionally rotating system. Multiplex cytokine analysis was used to analyze immune cell reactions.

Results

To demonstrate the applicability of the test system to implant materials, three commercially available barrier membranes (polytetrafluoroethylene (PTFE), polycaprolactone (PCL) and collagen) used for dental, trauma and maxillofacial surgery, were investigated for their potential interactions with immune cells. The results showed characteristic differences between the static and rotated incubation methods and in the overall activity profiles with very low immune cell responses to PTFE, intermediate ones to collagen and strong reactions to PCL.

Conclusion

This in vitro human whole blood model, using a complex organotypic matrix, is an excellent, easily standardized tool for categorizing immune cell responses to implant materials. Compared to in vitro cell culture systems used for materials research, this new assay system provides a far more detailed picture of response patterns the immune system can develop when interacting with different types of materials and surfaces.

Developing Porous Ortho- and Pyrophosphate-Containing Glass Microspheres; Structural and Cytocompatibility Characterisation

Phosphate-based glasses (PBGs) are promising materials for bone repair and regeneration as they can be formulated to be compositionally similar to the inorganic components of bone. Alterations to the PBG formulation can be used to tailor their degradation rates and subsequent release of biotherapeutic ions to induce cellular responses, such as osteogenesis. In this work, novel invert-PBGs in the series xP2O5·(56 - x)CaO·24MgO·20Na2O (mol%), where x is 40, 35, 32.5 and 30 were formulated to contain pyro (Q1) and orthophosphate (Q0) species. These PBGs were processed into highly porous microspheres (PMS) via flame spheroidisation, with ~68% to 75% porosity levels. Compositional and structural analysis using EDX and 31P-MAS NMR revealed that significant depolymerisation occurred with reducing phosphate content which increased further when PBGs were processed into PMS. A decrease from 50% to 0% in Q2 species and an increase from 6% to 35% in Q0 species was observed for the PMS when the phosphate content decreased from 40 to 30 mol%. Ion release studies also revealed up to a four-fold decrease in cations and an eight-fold decrease in phosphate anions released with decreasing phosphate content. In vitro bioactivity studies revealed that the orthophosphate-rich PMS had favourable bioactivity responses after 28 days of immersion in simulated body fluid (SBF). Indirect and direct cell culture studies confirmed that the PMS were cytocompatible and supported cell growth and proliferation over 7 days of culture. The P30 PMS with ~65% pyro and ~35% ortho phosphate content revealed the most favourable properties and is suggested to be highly suitable for bone repair and regeneration, especially for orthobiologic applications owing to their highly porous morphology.

Application of bioactive glasses in various dental fields

Bioactive glasses are a group of bioceramic materials that have extensive clinical applications. Their properties such as high biocompatibility, antimicrobial features, and bioactivity in the internal environment of the body have made them useful biomaterials in various fields of medicine and dentistry. There is a great variation in the main composition of these glasses and some of them whose medical usage has been approved by the US Food and Drug Administration (FDA) are called Bioglass. Bioactive glasses have appropriate biocompatibility with the body and they are similar to bone hydroxyapatite in terms of calcium and phosphate contents. Bioactive glasses are applied in different branches of dentistry like periodontics, orthodontics, endodontics, oral and maxillofacial surgery, esthetic and restorative dentistry. Also, some dental and oral care products have bioactive glasses in their compositions. Bioactive glasses have been used as dental implants in the human body in order to repair and replace damaged bones. Other applications of bioactive glasses in dentistry include their usage in periodontal disease, root canal treatments, maxillofacial surgeries, dental restorations, air abrasions, dental adhesives, enamel remineralization, and dentin hypersensitivity. Since the use of bioactive glasses in dentistry is widespread, there is a need to find methods and extensive resources to supply the required bioactive glasses. Various techniques have been identified for the production of bioactive glasses, and marine sponges have recently been considered as a rich source of it. Marine sponges are widely available and many species have been identified around the world, including the Persian Gulf. Marine sponges, as the simplest group of animals, produce different bioactive compounds that are used in a wide range of medical sciences. Numerous studies have shown the anti-tumor, anti-viral, anti-inflammatory, and antibiotic effects of these compounds. Furthermore, some species of marine sponges due to the mineral contents of their structural skeletons, which are made of biosilica, have been used for extracting bioactive glasses.

Mesoporous Bioglasses Enriched with Bioactive Agents for Bone Repair, with a Special Highlight of María Vallet-Regí’s Contribution

Throughout her impressive scientific career, Prof. María Vallet-Regí opened various research lines aimed at designing new bioceramics, including mesoporous bioactive glasses for bone tissue engineering applications. These bioactive glasses can be considered a spin-off of silica mesoporous materials because they are designed with a similar technical approach. Mesoporous glasses in addition to SiO₂ contain significant amounts of other oxides, particularly CaO and P₂O₅ and therefore, they exhibit quite different properties and clinical applications than mesoporous silica compounds. Both materials exhibit ordered mesoporous structures with a very narrow pore size distribution that are achieved by using surfactants during their synthesis. The characteristics of mesoporous glasses made them suitable to be enriched with various osteogenic agents, namely inorganic ions and biopeptides as well as mesenchymal cells. In the present review, we summarize the evolution of mesoporous bioactive glasses research for bone repair, with a special highlight on the impact of Prof. María Vallet-Regí´s contribution to the field.

Optimal regenerative repair of large segmental bone defect in a goat model with osteoinductive calcium phosphate bioceramic implants

So far, how to achieve the optimal regenerative repair of large load-bearing bone defects using artificial bone grafts is a huge challenge in clinic. In this study, a strategy of combining osteoinductive biphasic calcium phosphate (BCP) bioceramic scaffolds with intramedullary nail fixation for creating stable osteogenic microenvironment was applied to repair large segmental bone defects (3.0 cm in length) in goat femur model. The material characterization results showed that the BCP scaffold had the initial compressive strength of over 2.0 MPa, and total porosity of 84%. The cell culture experiments demonstrated that the scaffold had the excellent ability to promote the proliferation and osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (BMSCs). The in vivo results showed that the intramedullary nail fixation maintained the initial stability and structural integrity of the implants at early stage, promoting the osteogenic process both guided and induced by the BCP scaffolds. At 9 months postoperatively, good integration between the implants and host bone was observed, and a large amount of newborn bones formed, accompanying with the degradation of the material. At 18 months postoperatively, almost the complete new bone substitution in the defect area was achieved. The maximum bending strength of the repaired bone defects reached to the 100% of normal femur at 18 months post-surgery. Our results demonstrated the good potential of osteoinductive BCP bioceramics in the regenerative repair of large load-bearing bone defects. The current study could provide an effective method to treat the clinical large segmental bone defects.

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A novel strategy of achieving regenerative repair for large segmental bone defects with osteoinductive calcium phosphate bioceramics was developed successfully.

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The critical-sized goat femur defects (3.0 cm in length) were completely repaired by osteoinductive calcium phosphate bioceramics without using exogenous active factors or cells.

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The current study could provide an effective method to solve the clinical problem about large load-bearing bone defect repair.

Transforming the Degradation Rate of β-tricalcium Phosphate Bone Replacement Using 3-Dimensional Printing

BACKGROUND

β-Tricalcium phosphate (β-TCP) is one of the most common synthetic bone grafting materials utilized in craniofacial reconstruction; however, it is limited by a slow degradation rate. The aim of this study was to leverage 3-dimensional (3D) printing in an effort to accelerate the degradation kinetics of β-TCP.

METHODS

Twenty-two 1-month-old New Zealand white rabbits underwent creation of calvarial and alveolar defects, repaired with 3D-printed β-TCP scaffolds coated with 1000 μM of osteogenic agent dipyridamole. Rabbits were euthanized after 2, 6, and 18 months after surgical intervention. Bone regeneration, scaffold degradation, and bone mechanical properties were quantified.

RESULTS

Histological analysis confirmed the generation of vascularized and organized bone. Microcomputed tomography analysis from 2 to 18 months demonstrated decreased scaffold volume within calvarial (23.6% ± 2.5%, 5.1% ± 2.2%; P < 0.001) and alveolar (21.5% ± 2.2%, 0.2% ± 1.9%; P < 0.001) defects, with degradation rates of 54.6%/year and 90.5%/year, respectively. Scaffold-inducted bone generation within the defect was volumetrically similar to native bone in the calvarium (55.7% ± 6.9% vs 46.7% ± 6.8%; P = 0.064) and alveolus (31.4% ± 7.1% vs 33.8% ± 3.7%; P = 0.337). Mechanical properties between regenerated and native bone were similar.

CONCLUSIONS

Our study demonstrates an improved degradation profile and replacement of absorbed β-TCP with vascularized, organized bone through 3D printing and addition of an osteogenic agent. This novel additive manufacturing and tissue engineering protocol has implications to the future of craniofacial skeletal reconstruction as a safe and efficacious bone tissue engineering method.

In vitro and in vivo evaluation of the pH-neutral bioactive glass as high performance bone grafts

Osteogenic and angiogenic properties are two most valued factors for bone grafting materials. Biomedical materials with synergistic promotion effects on these two properties would be highly desirable. In this study, we showed that a recently developed pH-neutral bioactive glass (PSC) possessed such characteristics. Compared to two classical biomaterials, 45S5 bioactive glass and beta-tricalcium phosphate (β-TCP), PSC markedly improved BMSCs' proliferation, migration and mineralization as well as their osteogenic and angiogenic differentiation. In vivo, PSC showed better performance on inducing bone regeneration than both 45S5 and β-TCP, as featured by elevated bone mineral density (BMD) and new bone areas. PSC also significantly promoted new blood vessels formation compared with those in control groups. Furthermore, we revealed that PSC induced osteogenic and angiogenic differentiation of BMSCs through the PI3K/Akt/HIF-1α pathway, which had not been reported before. This synergistic effect of the PI3K/Akt/HIF-1α pathway on osteogenesis and angiogenic differentiation of BMSCs suggested that biomedical materials may promote new bone formation through multiple signal pathways, thus shedding light on the future development of materials with better performance.

Novel antimicrobial phosphate-free glass-ceramic scaffolds for bone tissue regeneration

In this study a phosphate-free glass-ceramic porous scaffold was synthesized by a three-step methodology involving slurry preparation, induction of porosity by surfactant-assisted foaming following by freeze-drying and sintering. This inorganic scaffold was characterized by X-ray diffraction, scanning electron microscope (SEM), degradation and bioactivity. Thermal treatment at 750 °C showed two new crystalline phases, combeite and nepheline, into the glassy matrix responsible for its properties. The cell response of the scaffold was also evaluated for using as a bone graft substitute. A commercial Biphasic Calcium Phosphate, BCP, scaffold was assessed in parallel as reference material. Microstructures obtained by SEM showed the presence of macro, meso and microporosity. The glass-ceramic scaffold possesses an interconnected porosity around 31% with a crack-pore system that promote the protein adsorption and cell attachment. Glass-ceramic scaffold with high concentration of calcium ions shows an antimicrobial behavior against Escherichia coli after 24 h of contact. Nepheline phase present in the glass-ceramic structure is responsible for its high mechanical properties being around 87 MPa. Glass-ceramic scaffold promotes greater protein adsorption and therefore the attachment, spreading and osteodifferentiation of Adipose Derived Stem Cells than BCP scaffold. A higher calcification was induced by glass-ceramic scaffold compared to reference BCP material.

Bioactive Glass Applications in Dentistry

At present, researchers in the field of biomaterials are focusing on the oral hard and soft tissue engineering with bioactive ingredients by activating body immune cells or different proteins of the body. By doing this natural ground substance, tissue component and long-lasting tissues grow. One of the current biomaterials is known as bioactive glass (BAG). The bioactive properties make BAG applicable to several clinical applications involving the regeneration of hard tissues in medicine and dentistry. In dentistry, its uses include dental restorative materials, mineralizing agents, as a coating material for dental implants, pulp capping, root canal treatment, and air-abrasion, and in medicine it has its applications from orthopedics to soft-tissue restoration. This review aims to provide an overview of promising and current uses of bioactive glasses in dentistry.