A 3D-printed molybdenum-containing scaffold exerts dual pro-osteogenic and anti-osteoclastogenic effects to facilitate alveolar bone repair

Construction of bilayer biomimetic periosteum based on SLA-3D printing for bone regeneration

An ideal biomimetic periosteum should have excellent biocompatibility to promote osteoclast adhesion and improve osseointegration, which is significant in promoting bone regeneration. In this work, a bionic artificial periosteum printed by the SLA-3D printing was prepared, consisting of a poly (ethylene glycol) diacrylate (PEGDA)/chitosan/tricalcium phosphate (TCP) fibrous layer and a gelatin methacryloyl (GelMA)/ammonium molybdate (Mo) cambium layer. Distinct surface characteristics were achieved on both sides of the biomimetic periosteum. Among them, the fibrous layer has high mechanical properties and low porosity, which is conducive to preventing the pulling of muscle tissues and the invasion of soft tissues. The cambium layer has a porous structure and bioactive factors that can effectively promote osteogenic differentiation of preosteoblasts. Combined with mild photothermal therapy triggered by NIR light, the biomimetic periosteum could promote bone regeneration at both the chemical and physical levels. This 3D-printed bilayer hydrogel can provide a promising strategy for preparing advanced tissue-engineered periosteum with excellent physical and bone regeneration properties.

3D-printed biomimetic bone scaffold loaded with lyophilized concentrated growth factors promotes bone defect repair by regulation the VEGFR2/PI3K/AKT signaling pathway

This study investigates the effects of concentrated growth factors (CGF) and bone substitutes on the proliferation and differentiation of bone marrow mesenchymal stem cells (BMSCs), as well as the development of a novel 3D-printed biomimetic bone scaffold. Based on the structure of cancellous bone, 3D-printed bionic bone with sustainable release of growth factors and Ca2+ was prepared. Using BMSCs and EA.hy926 in co-culture with the bionic bone scaffold, experimental results demonstrate that this bionic structural design enhances cell proliferation and adhesion, and that the bionic bone possesses the ability to promote bone and vascular regeneration directly. Transcriptomics, western blot analysis, and flow cytometry are employed to investigate the effects of CGF and Ca2+ on the signaling pathways of BMSCs. The study reports that vascular endothelial growth factor (VEGF) released by CGF activated VEGFR2 on BMSCs, leading to Ca2+ influx and activation of the PI3K/AKT signaling pathway, thereby influencing osteogenesis. Animal experiments confirm the ability of the bionic bone to promote osteogenesis in vivo, and its unique degradation pattern accelerates the in vivo repair of bone defects. In conclusion, this study presents a novel biomimetic strategy and, for the first time, explores the potential mechanism by which VEGF and Ca2+ regulate BMSCs differentiation through the VEGFR2/PI3K/AKT signaling pathway. These insights offer a new perspective for the development of innovative bone substitute materials.

Injectable hydrogel microsphere-bomb for MRSA-infected chronic osteomyelitis

Biofilm and bone tissue defect induced by the bacterial infection severely impede chronic osteomyelitis treatment. It is critical to break though the densely and obstinate biofilm so that the target drugs can deliver to the infected bone more effectively. Herein, an acoustically responsive multifunctional hydrogel microsphere-bomb (EMgel) was designed and prepared by microfluidic technology, which could be injected to the focus of bone infection, and blasted into the nidus deeply to destroy the bacterial biofilm matrix barrier under penetrating ultrasound, so the encapsulated natural polyphenolic EGCG and bioactive MoS2 released to repair the damaged bone. The results proved the hydrogel microsphere-bomb exhibited controlling drug release, favorable antibacterial (as high as 99 %), high biofilm resistance, fascinating antioxidation, good cytocompatibility, and osteogenic differentiation. The acoustically responsive microsphere-bomb further proved their fantastic ability to eradicate biofilm and promote bone regeneration in the Methicillin-resistant Staphylococcus aureus (MRSA) infected chronic osteomyelitis model due to the synergy effects of EGCG and bioactive MoS2. Especially, immunohistochemical staining showed lower inflammatory reaction and higher expression of OCN in EMgel group treated with ultrasound wave. This study presents a new design of hydrogel microsphere-based intelligence drug delivery for osteomyelitis treatment, which exhibit great promising potential for dealing with chronic orthopedic infections, drug delivery system and tissue engineering.

Developing functional hydrogels for treatment of oral diseases

Oral disease is a severe healthcare challenge that diminishes people's quality of life. Functional hydrogels with suitable biodegradability, biocompatibility, and tunable mechanical properties have attracted remarkable interest and have been developed for treating oral diseases. In this review, we present up-to-date research on hydrogels for the management of dental caries, endodontics, periapical periodontitis, and periodontitis, depending on the progression of dental diseases. The strategies of hydrogels for treating oral mucosal diseases and salivary gland diseases are then classified. After that, we focus on the application of hydrogels related to tumor therapy and tissue defects. Finally, the review prospects the restrictions and the perspectives on the utilization of hydrogels in oral disease treatment. We believe this review will promote the advancement of more amicable, functional and personalized approaches for oral diseases.

Unlocking the potential of stimuli-responsive biomaterials for bone regeneration

Bone defects caused by tumors, osteoarthritis, and osteoporosis attract great attention. Because of outstanding biocompatibility, osteogenesis promotion, and less secondary infection incidence ratio, stimuli-responsive biomaterials are increasingly used to manage this issue. These biomaterials respond to certain stimuli, changing their mechanical properties, shape, or drug release rate accordingly. Thereafter, the activated materials exert instructive or triggering effects on cells and tissues, match the properties of the original bone tissues, establish tight connection with ambient hard tissue, and provide suitable mechanical strength. In this review, basic definitions of different categories of stimuli-responsive biomaterials are presented. Moreover, possible mechanisms, advanced studies, and pros and cons of each classification are discussed and analyzed. This review aims to provide an outlook on the future developments in stimuli-responsive biomaterials.

Boric acid and Molybdenum trioxide synergistically stimulate osteogenic differentiation of human bone marrow-derived mesenchymal stromal cells

INTRODUCTION

Metals and their metal ions have been shown to exhibit certain biological functions that make them attractive for use in biomaterials, for example in bone tissue engineering (BTE) applications. Recent data shows that Molybdenum (Mo) is a potent inducer of osteogenic differentiation in human bone marrow-derived mesenchymal stromal cells (BMSCs). On the other hand, while boron (B) has been shown to enhance vascularization in BTE applications, its impact on osteogenic differentiation is volatile: while improved osteogenic differentiation has been described, other data show that B might slow down osteogenic differentiation or reduce the calcification of the extracellular matrix (ECM) when applied in higher doses. Still, the combination of pro-osteogenic Mo and pro-angiogenic B is certainly attractive in the context of biomaterials intended for the use in BTE.

METHODS

Therefore, the combined effect of molybdenum trioxide and boric acid at different ratios was investigated in this study to evaluate the effects on the viability, proliferation, osteogenic differentiation, ECM production and maturation of BMSCs.

RESULTS

Mo ions proved to be stronger osteoinductive compared to B, in fact, while some osteogenic differentiation markers were downregulated in the presence of B, the presence of Mo provided compensation. The combined application of B and Mo indicated a combination of individual effects, partially even enhancing the expected combined performance of the single stimulations.

CONCLUSIONS

The combination of B and Mo might be beneficial for BTE applications since the limited osteogenic properties of B can be compensated by Mo. Furthermore, since B is known to be pro-angiogenic, the combination of both substances may synergistically lead to improved vascularization and bone regeneration. Future studies should assess the angiogenic performance of this combination in greater detail.

Conductive and Enhanced Mechanical Strength of Mo2Ti2C3 MXene-Based Hydrogel Promotes Neurogenesis and Bone Regeneration in Bone Defect Repair

Bone defects are common with increasing high-energy fractures, tumor bone invasion, and implantation revision surgery. Bone is an electroactive tissue that has electromechanical interaction with collogen, osteoblasts, and osteoclasts. Hydrogel provides morphological plasticity and extracellular matrix (ECM) 3D structures for cell survival, and is widely used as a bone engineering material. However, the hydrogels have poor mechanical intensity and lack of cell adhesion, slow gelation time, and limited conductivity. MXenes are novel nanomaterials with hydrophilic groups that sense cell electrophysiology and improve hydrogel electric conductivity. Herein, gelatin had multiple active groups (NH2, OH, and COOH) and an accelerated gelation time. Acrylamide has Schiff base bonds to cross-link with gelatin and absorb metal ions. Deacetylated chitosan improved cell adhesion and active groups to connect MXene and acrylamide. We constructed Mo2Ti2C3 MXene hydrogel with improved elastic modulus and viscosity, chemical cross-linking structure, electric conductivity, and good compatibility. Mo2Ti2C3 MXene hydrogel exhibits outstanding osteogenesis in vitro. Mo2Ti2C3 MXene hydrogel promotes osteogenesis via alkaline phosphatase (ALP) and alizarin red S (ARS) staining, improving osteogenic marker genes and protein expressions in vitro. Mo2Ti2C3 MXene hydrogel aids new bone formation in the in vivo calvarial bone defect model via micro-CT and histology. Mo2Ti2C3 MXene hydrogel facilitates neurogenesis factors nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) expression, and aids newly born neuron marker Tuj-1 and sensory neuron marker serotonin (5-HT) and osteogenesis pathway proteins, runt-related transcription factor 2 (Runx2), osteocalcin (OCN), SMAD family member 4 (SMAD4), and bone morphogenetic protein-2 (BMP2) in the bone defect repair process. Mo2Ti2C3 MXene hydrogel promotes osteogenesis and neurogenesis, which extends its biomedical application in bone defect reconstruction.

Vitamin D3 Release from MgO Doped 3D Printed TCP Scaffolds for Bone Regeneration

Regenerating bone tissue in critical-sized craniofacial bone defects remains challenging and requires the implementation of innovative bone implants with early stage osteogenesis and blood vessel formation. Vitamin D3 is incorporated into MgO-doped 3D-printed scaffolds for defect-specific and patient-specific implants in low load-bearing areas. This novel bone implant also promotes early stage osteogenesis and blood vessel development. Our results show that vitamin D3-loaded MgO-doped 3D-printed scaffolds enhance osteoblast cell proliferation 1.3-fold after being cultured for 7 days. Coculture studies on osteoblasts derived from human mesenchymal stem cells (hMSCs) and osteoclasts derived from monocytes show the upregulation of genes related to osteoblastogenesis and the downregulation of RANK-L, which is essential for osteoclastogenesis. Release of vitamin D3 also inhibits osteoclast differentiation by 1.9-fold after a 21-day culture. After 6 weeks, vitamin D3 release from MgO-doped 3D-printed scaffolds enhances the new bone formation, mineralization, and angiogenic potential. The multifunctional 3D-printed scaffolds can improve early stage osteogenesis and blood vessel formation in craniofacial bone defects.

Bionic Bilayer Scaffold for Synchronous Hyperthermia Therapy of Orthotopic Osteosarcoma and Osteochondral Regeneration

Large osseous void, postsurgical neoplastic recurrence, and slow bone-cartilage repair rate raise an imperative need to develop functional scaffold in clinical osteosarcoma treatment. Herein, a bionic bilayer scaffold constituting croconaine dye-polyethylene glycol@sodium alginate hydrogel and poly(l-lactide)/hydroxyapatite polymer matrix is fabricated to simultaneously achieve a highly efficient killing of osteosarcoma and an accelerated osteochondral regeneration. First, biomimetic osteochondral structure along with adequate interfacial interaction of the bilayer scaffold provide a structural reinforcement for transverse osseointegration and osteochondral regeneration, as evidenced by upregulated specific expressions of collagen type-I, osteopontin, and runt-related transcription factor 2. Meanwhile, thermal ablation of the synthesized nanoparticles and mitochondrial dysfunction caused by continuously released hydroxyapatite induce residual tumor necrosis synergistically. To validate the capabilities of inhibiting tumor growth and promoting osteochondral regeneration of our proposed scaffold, a novel orthotopic osteosarcoma model simulating clinical treatment scenarios of bone tumors is established on rats. Based on amounts of in vitro and in vivo results, an effective killing of osteosarcoma and a suitable osteal-microenvironment modulation of such bionic bilayer composite scaffold are achieved, which provides insightful implications for photonic hyperthermia therapy against osteosarcoma and following osseous tissue regeneration.

3D bioprinting technology to construct bone reconstruction research model and its feasibility evaluation

Objective: To explore and construct a 3D bone remodeling research model displaying stability, repeatability, and precise simulation of the physiological and biochemical environment in vivo. Methods: In this study, 3D bioprinting was used to construct a bone reconstruction model. Sodium alginate (SA), hydroxyapatite (HA) and gelatin (Gel) were mixed into hydrogel as scaffold material. The osteoblast precursor cells MC3T3-E1 and osteoclast precursor cells RAW264.7 were used as seed cells, which may or may not be separated by polycarbonate membrane. The cytokines osteoprotegerin (OPG) and receptor activator of NF-κB ligand (RANKL) were used to induce cell differentiation. The function of scaffolds in the process of bone remodeling was analyzed by detecting the related markers of osteoblasts (alkaline phosphatase, ALP) and osteoclasts (tartrate resistant acid phosphatase, TRAP). Results: The scaffold showed good biocompatibility and low toxicity. The surface morphology aided cell adhesion and growth. The scaffold had optimum degradability, water absorption capacity and porosity, which are in line with the conditions of biological experiments. The effect of induced differentiation of cells was the best when cultured alone. After direct contact between the two types of cells at 2D or 3D level, the induced differentiation of cells was inhibited to varying degrees, although they still showed osteogenesis and osteoclast. After the cells were induced by indirect contact culture, the effect of induced differentiation improved when compared with direct contact culture, although it was still not as good as that of single culture. On the whole, the effect of inducing differentiation at 3D level was the same as that at 2D level, and its relative gene expression and enzyme activity were higher than that in the control group. Hence the scaffold used in this study could induce osteogenesis as well as osteoclast, thereby rendering it more effective in inducing new bone formation. Conclusion: This method can be used to construct the model of 3D bone remodeling mechanism.

Engineering metabolism to modulate immunity

Metabolic programming and reprogramming have emerged as pivotal mechanisms for altering immune cell function. Thus, immunometabolism has become an attractive target area for treatment of immune-mediated disorders. Nonetheless, many hurdles to delivering metabolic cues persist. In this review, we consider how biomaterials are poised to transform manipulation of immune cell metabolism through integrated control of metabolic configurations to affect outcomes in autoimmunity, regeneration, transplant, and cancer. We emphasize the features of nanoparticles and other biomaterials that permit delivery of metabolic cues to the intracellular compartment of immune cells, or strategies for altering signals in the extracellular space. We then provide perspectives on the potential for reciprocal regulation of immunometabolism by the physical properties of materials themselves. Lastly, opportunities for clinical translation are highlighted. This discussion contributes to our understanding of immunometabolism, biomaterials-based strategies for altering metabolic configurations in immune cells, and emerging concepts in this evolving field.

Dual Photo-Enhanced Interpenetrating Network Hydrogel with Biophysical and Biochemical Signals for Infected Bone Defect Healing

The healing of infected bone defects (IBD) is a complex physiological process involving a series of spatially and temporally overlapping events, including pathogen clearance, immunological modulation, vascularization, and osteogenesis. Based on the theory that bone healing is regulated by both biochemical and biophysical signals, in this study, a copper doped bioglass (CuBGs)/methacryloyl-modified gelatin nanoparticle (MA-GNPs)/methacrylated silk fibroin (SilMA) hybrid hydrogel is developed to promote IBD healing. This hybrid hydrogel demonstrates a dual-photocrosslinked interpenetrating network mechanism, wherein the photocrosslinked SilMA as the main network ensures structural integrity, and the photocrosslinked MA-GNPs colloidal network increases strength and dissipates loading forces. In an IBD model, the hydrogel exhibits excellent biophysical characteristics, such as adhesion, adaptation to irregular defect shapes, and in situ physical reinforcement. At the same time, by sequentially releasing bioactive ions such as Cu2+ , Ca2+ , and Si2+ ions from CuBGs on demand, the hydrogel spatiotemporally coordinates antibacterial, immunomodulatory and bone remodeling events, efficiently removing infection and accelerating bone repair without the use of antibiotics or exogenous recombinant proteins. Therefore, the hybrid hydrogel can be used as a simple and effective method for the treatment of IBD.

Design and manufacturing of biomimetic scaffolds for bone repair inspired by bone trabeculae

Porous scaffold (PorS) implants, particularly those that mimic the structural features of natural cancellous bone (NCanB), are increasingly essential for the treatment of large-area bone defects. However, the mechanical properties of NCanB-based bionic bone scaffold (BioS) and its performance as a bone repair material have not been fully explored. This study investigates the effect of bionic structure parameters on the mechanical properties and bone reconstruction performance of BioS. Using laser powder bed fusion (L-PBF) technology, different BioS with various structural parameters were created and evaluated using Micro-CT, compression testing, Finite Element (FE) Simulation, and computational fluid dynamics (CFD), and compared to commonly used clinical PorS. Assess the capacity of the BioS scaffold to support and enhance bone reconstruction following implantation through the evaluation of its mechanical properties, permeability, and fluid shear stress (FSS). BioS-85-90 and BioS-80-50 showed suitable mechanical properties, performed well in FE simulation of implantation, demonstrated outstanding abilities for osteoinductive ingrowth and bone tissue differentiation, and proved to be reliable materials for the reconstruction of bone defects. Therefore, BioS shows significant potential for clinical application as a bone reconstruction material, providing a solid foundation for the integration of tissue engineering and bionic design.

Biodegradable Implants for Internal Fixation of Fractures and Accelerated Bone Regeneration

Bone fractures have always been a burden to patients due to their common occurrence and severe complications. Traditionally, operative treatments have been widely used in the clinic for implanting, despite the fact that they can only achieve bone fixation with limited stability and pose no effect on promoting tissue growth. In addition, the nondegradable implants usually need a secondary surgery for implant removal, otherwise they may block the regeneration of bones resulting in bone nonunion. To overcome the low degradability of implants and avoid multiple surgeries, tissue engineers have investigated various biodegradable materials for bone regeneration, whereas the significance of stability of long-term bone fixation tends to be neglected during this process. Combining the traditional orthopedic implantation surgeries and emerging tissue engineering, we believe that both bone fixation and bone regeneration are indispensable factors for a successful bone repair. Herein, we define such a novel idea as bone regenerative fixation (BRF), which should be the main future development trend of biodegradable materials.

Biofabrication of engineered dento-alveolar tissue

Oral health is essential for a good overall health. Dento-alveolar conditions have a high prevalence, ranging from tooth decay periodontitis to alveolar bone resorption. However, oral tissues exhibit a limited regenerative capacity, and full recovery is challenging. Therefore, regenerative therapies for dento-alveolar tissue (e.g., alveolar bone, periodontal membrane, dentin-pulp complex) have gained much attention, and novel approaches have been proposed in recent decades. This review focuses on the cells, biomaterials and the biofabrication methods used to develop therapies for tooth root bioengineering. Examples of the techniques covered are the multitude of additive manufacturing techniques and bioprinting approaches used to create scaffolds or tissue constructs. Furthermore, biomaterials and stem cells utilized during biofabrication will also be described for different target tissues. As these new therapies gradually become a reality in the lab, the translation to the clinic is still minute, with a further need to overcome multiple challenges and broaden the clinical application of these alternatives.

Multicellular Bioprinting of Biomimetic Inks for Tendon-to-Bone Regeneration

Tendon-to-bone interface has a hierarchical structure and gradient component that are conducive to distributing the stresses to achieve movement. Conventional biomaterials lack the capacity to induce synchronous repair of multiple tissues, resulting in the failure of the interface repair. Biomimetic strategies have attracted enormous attention in the field of complex structure regeneration because they can meet the different physiological requirements of multiple tissues. Herein, a biomimetic ink mimicking tendon/bone tissues is developed by combining tendon/bone-related cells and Mo-containing silicate (MS) bioceramics. Subsequently, biomimetic multicellular scaffolds are fabricated to achieve the simulation of the hierarchical structure and cellular composition of tendon-to-bone interfaces by the spatial distribution of the biomimetic inks via 3D bioprinting, which is of great significance for inducing the regeneration of complex structures in the interface region. In addition, attributed to the desirable ionic microenvironment created by MS bioceramics, the biomimetic scaffolds possess the dual function of inducing tendon/bone-related cells tenogenic and osteogenic differentiation in vitro, and promote the integrated regeneration of tendon-to-bone interfaces in vivo. The study offers a feasible strategy to construct biomimetic multicellular scaffolds with bifunction for inducing multi-lineage tissue regeneration, especially for regenerating soft-to-hard tissue interfaces.

Impact exerted by scaffolds and biomaterials in periodontal bone and tissue regeneration engineering: new challenges and perspectives for disease treatment

The periodontium is an appropriate target for regeneration, as it cannot restore its function following disease. Significantly, the periodontium's limited regenerative capacity could be enhanced through the development of novel biomaterials and therapeutic approaches. Notably, the regenerative potential of the periodontium depends not only on its tissue-specific architecture and function but also on its ability to reconstruct distinct tissues and tissue interfaces, implying that the development of tissue engineering techniques can offer new perspectives for the organized reconstruction of soft and hard periodontal tissues. With their biocompatible structure and one-of-a-kind stimulus-responsive property, hydrogels have been utilized as an excellent drug delivery system for the treatment of several oral diseases. Furthermore, bioceramics and three-dimensional (3D) printed scaffolds are also appropriate scaffolding materials for the regeneration of periodontal tissue, bone, and cartilage. This work aims to examine and update material-based, biologically active cues and the deployment of breakthrough bio-fabrication technologies to regenerate the numerous tissues that comprise the periodontium for clinical and scientific applications.

Chitosan-coated and thymol-loaded polymeric semi-interpenetrating hydrogels: An effective platform for bioactive molecule delivery and bone regeneration in vivo

Thymol (2-isopropyl-5-methylphenol; Thy) is a monoterpene phenolic phytocompound with medicinal properties; however, its impact on osteogenesis is yet to be thoroughly investigated. Its distribution is often hampered because of its intricate hydrophobic structure, which reduces its bioavailability. In this study, we synthesized a drug delivery vehicle using semi-interpenetrating polymer network (SIPN) hydrogels containing sodium alginate and poly(2-ethyl-2-oxazoline) (SA/Pox) loaded with Thy at varying concentrations (100, 150, and 200 μM). Subsequently, they were coated with chitosan (CS) to increase bioactivity and for sustained and prolonged release of Thy. Thy-loaded CS-coated SIPN hydrogels (SA/Pox/CS-Thy) were developed using ionic gelation and polyelectrolyte-complexation techniques. The addition of CS to hydrogels enhanced their physicochemical and material properties. These hydrogels were cytofriendly toward mouse mesenchymal stem cells (mMSCs). When mMSCs were cultured on hydrogels, Thy stimulated osteoblastic differentiation, as evidenced by calcium deposits at the cellular level. The expression of RUNX2, a key bone transcriptional factor, and other differentiation biomarkers was significantly enhanced in mMSCs cultured on SA/Pox/CS-Thy hydrogels. Notably, Thy in the SA/Pox/CS hydrogels significantly activated the TGF-β/BMP signaling pathway, which is involved in osteogenesis. A rat tibial bone defect model system revealed that the incorporation of Thy into SA/Pox/CS hydrogels augmented bone regeneration. Thus, sustained and prolonged release of Thy from the SA/Pox/CS hydrogels promoted osteoblast differentiation in vitro and bone formation in vivo. These findings shed light on the effect of Thy bioavailability in fostering osteoblast differentiation and its prospective application in bone rejuvenation.