Regulation of Osteoimmune Microenvironment and Osteogenesis by 3D-Printed PLAG/black Phosphorus Scaffolds for Bone Regeneration

A five-in-one novel MOF-modified injectable hydrogel with thermo-sensitive and adhesive properties for promoting alveolar bone repair in periodontitis: Antibacterial, hemostasis, immune reprogramming, pro-osteo-/angiogenesis and recruitment

Periodontitis is a chronic inflammatory disease caused by plaque that destroys the alveolar bone tissues, resulting in tooth loss. Poor eradication of pathogenic microorganisms, persistent malignant inflammation and impaired osteo-/angiogenesis are currently the primary challenges to control disease progression and rebuild damaged alveolar bone. However, existing treatments for periodontitis fail to comprehensively address these issues. Herein, an injectable composite hydrogel (SFD/CS/ZIF-8@QCT) encapsulating quercetin-modified zeolitic imidazolate framework-8 (ZIF-8@QCT) is developed. This hydrogel possesses thermo-sensitive and adhesive properties, which can provide excellent flowability and post-injection stability, resist oral fluid washout as well as achieve effective tissue adhesion. Inspirationally, it is observed that SFD/CS/ZIF-8@QCT exhibits a rapid localized hemostatic effect following implantation, and then by virtue of the sustained release of zinc ions and quercetin exerts excellent collective functions including antibacterial, immunomodulation, pro-osteo-/angiogenesis and pro-recruitment, ultimately facilitating excellent alveolar bone regeneration. Notably, our study also demonstrates that the inhibition of osteo-/angiogenesis of PDLSCs under the periodontitis is due to the strong inhibition of energy metabolism as well as the powerful activation of oxidative stress and autophagy, whereas the synergistic effects of quercetin and zinc ions released by SFD/CS/ZIF-8@QCT are effective in reversing these biological processes. Overall, our study presents innovative insights into the advancement of biomaterials to regenerate alveolar bone in periodontitis.

3D printed biopolymer/black phosphorus nanoscaffolds for bone implants: A review

Bone implantation is one of the recognized and effective means of treating bone defects, but osteoporosis and bone tumor-related bone abnormalities have a series of problems such as susceptibility to infection, difficulty in healing, and poor therapeutic effect, which poses a great challenge to clinical medicine. Three-dimensional things may be printed using 3D printing. Researchers can feed materials through the printer layer by layer to create the desired shape for a 3D structure. It is widely employed in the healing of bone defects, and it is an improved form of additive manufacturing technology with prospective future applications. This review's objective is to provide an overview of the findings reports pertaining to 3D printing biopolymers in recent years, provide an overview of biopolymer materials and their composites with black phosphorus for 3D printing bone implants, and the characterization methods of composite materials are also summarized. In addition, summarizes 3D printing methods based on ink printing and laser printing, pointing out their special features and advantages, and provide a combination strategy of photothermal therapy and bone regeneration materials for black phosphorus-based materials. Finally, the associations between bone implant materials and immune cells, the bio-environment, as well as the 3D printing bone implants prospects are outlined.

Functional antimicrobial peptide-loaded 3D scaffolds for infected bone defect treatment with AI and multidimensional printing

Infection is the most prevalent complication of fractures, particularly in open fractures, and often leads to severe consequences. The emergence of bacterial resistance has significantly exacerbated the burden of infection in clinical practice, making infection control a significant treatment challenge for infectious bone defects. The implantation of a structural stent is necessary to treat large bone defects despite the increased risk of infection. Therefore, there is a need for the development of novel antibacterial therapies. The advancement in antibacterial biomaterials and new antimicrobial drugs offers fresh perspectives on antibacterial treatment. Although antimicrobial 3D scaffolds are currently under intense research focus, relying solely on material properties or antibiotic action remains insufficient. Antimicrobial peptides (AMPs) are one of the most promising new antibacterial therapy approaches. This review discusses the underlying mechanisms behind infectious bone defects and presents research findings on antimicrobial peptides, specifically emphasizing their mechanisms and optimization strategies. We also explore the potential prospects of utilizing antimicrobial peptides in treating infectious bone defects. Furthermore, we propose that artificial intelligence (AI) algorithms can be utilized for predicting the pharmacokinetic properties of AMPs, including absorption, distribution, metabolism, and excretion, and by combining information from genomics, proteomics, metabolomics, and clinical studies with computational models driven by machine learning algorithms, scientists can gain a comprehensive understanding of AMPs' mechanisms of action, therapeutic potential, and optimizing treatment strategies tailored to individual patients, and through interdisciplinary collaborations between computer scientists, biologists, and clinicians, the full potential of AI in accelerating the discovery and development of novel AMPs will be realized. Besides, with the continuous advancements in 3D/4D/5D/6D technology and its integration into bone scaffold materials, we anticipate remarkable progress in the field of regenerative medicine. This review summarizes relevant research on the optimal future for the treatment of infectious bone defects, provides guidance for future novel treatment strategies combining multi-dimensional printing with new antimicrobial agents, and provides a novel and effective solution to the current challenges in the field of bone regeneration.

Recent Advances in Degradable Biomedical Polymers for Prevention, Diagnosis and Treatment of Diseases

Biomedical polymers play a key role in preventing, diagnosing, and treating diseases, showcasing a wide range of applications. Their unique advantages, such as rich source, good biocompatibility, and excellent modifiability, make them ideal biomaterials for drug delivery, biomedical imaging, and tissue engineering. However, conventional biomedical polymers suffer from poor degradation in vivo, increasing the risks of bioaccumulation and potential toxicity. To address these issues, degradable biomedical polymers can serve as an alternative strategy in biomedicine. Degradable biomedical polymers can efficiently relieve bioaccumulation in vivo and effectively reduce patient burden in disease management. This review comprehensively introduces the classification and properties of biomedical polymers and the recent research progress of degradable biomedical polymers in various diseases. Through an in-depth analysis of their classification, properties, and applications, we aim to provide strong guidance for promoting basic research and clinical translation of degradable biomedical polymers.

Photoactivated Hydrogel Therapeutic System with MXene-Based Nanoarchitectonics Potentiates Endogenous Bone Repair Through Reshaping the Osteo-Vascularization Network

The repair and reconstruction of large-scale bone defects face enormous challenges because of the failure to reconstruct the osteo-vascularization network. Herein, a near-infrared (NIR) light-responsive hydrogel system is reported to achieve programmed tissue repair and regeneration through the synergetic effects of on-demand drug delivery and mild heat stimulation. The spatiotemporal hydrogel system (HG/MPa) composed of polydopamine-coated Ti3C2Tx MXene (MP) nanosheets decorated with acidic fibroblast growth factor (aFGF, a potent angiogenic drug) and hydroxypropyl chitosan/gelatin (HG) hydrogel is developed to orchestrate the reconstruction of the osteo-vascularization network and boost bone regeneration. Upon exposure to NIR light irradiation, the engineered HG/MPa hydrogel can achieve the initial complete release of aFGF to induce rapid angiogenesis and provide sufficient blood supply, maximizing its biofunction in the defect area. This integrated hydrogel system demonstrated good therapeutic efficacy in promoting cell adhesion, proliferation, migration, angiogenesis, and osteogenic differentiation through periodic NIR irradiation. In vivo, animal experiments further revealed that the spatiotemporalized hydrogel platform synergized with mild photothermal treatment significantly accelerated critical-sized bone defect healing by increasing the osteo-vascularization network density, recruiting endogenous stem cells, and facilitating the production of osteogenesis/angiogenesis-related factors. Overall, smart-responsive hydrogel could enhance the reconstruction of the osteo-vascularization network in bone regeneration.

Site-specific bioorthogonal regulation of bone morphogenetic protein 2 expression for effective bone regeneration

Growth factor holds great promise for bone regeneration, and spatiotemporal control of their expressing through site-specific reactions is crucial but challenging for on-demand therapy. In this study, we present the development of a novel unnatural amino acids (UAAs)-triggered therapeutic switch (UATS) system, composed of an orthogonal aminoacyl-tRNA-synthase (aaRS)-tRNA pair and a bone morphogenetic protein 2 (BMP2) gene harboring premature stop codon, which enable in situ and on-demand initiation of the expression of BMP2. The resulting UATS system allowed specifically control of base expressing on the BMP2 mRNA that switched to the BMP2 protein with complete structure and function to facilitate bone regeneration. Our investigations showed that the UATS system exhibits remarkable attributes of rapid, sensitive, reversible, and sustained BMP2 expression both in vitro and in vivo settings. Moreover, the implantation of microencapsulated cells with UATS system is applied to a mouse femur defect model, demonstrating high effciency in controlled expressing of BMP2 protein and substantial repair of bone defect following oral administration of UAAs. Therefore, our findings underscore the great potential of UATS system for on-demand awakening of functional growth factor, thus offering promising prospects in the realm of regenerative medicine.

Black phosphorus for bone regeneration: Mechanisms involved and influencing factors

BP has shown good potential for promoting bone regeneration. However, the understanding of the mechanisms of BP-enhanced bone regeneration is still limited. This review first summarizes the recent advances in applications of BP in bone regeneration. We further highlight the possibility that BP enhances bone regeneration by regulating the behavior of mesenchymal stem cells (MSCs), osteoblasts, vascular endothelial cells (VECs), and macrophages, mainly through the regulation of cytoskeletal remodeling, energy metabolism, oxidation resistance and surface adsorption properties, etc. In addition, moderating the physicochemical properties of BP (i.e., shape, size, and surface charge) can alter the effects of BP on bone regeneration. This review reveals the underlying mechanisms of BP-enhanced bone regeneration and provides strategies for further material design of BP-based materials for bone regeneration.

Graphene Oxide/Black Phosphorus Functionalized Collagen Scaffolds with Enhanced Near-Infrared Controlled In Situ Biomineralization for Promoting Infectious Bone Defect Repair through PI3K/Akt Pathway

Infectious bone defects resulting from surgery, infection, or trauma are a prevalent clinical issue. Current treatments commonly used include systemic antibiotics and autografts or allografts. Nevertheless, therapies come with various disadvantages, including multidrug-resistant bacteria, complications arising from the donor site, and immune rejection, which makes artificial implants desirable. However, artificial implants can fail due to bacterial infections and inadequate bone fusion after implantation. Thus, the development of multifunctional bone substitutes that are biocompatible, antibacterial, osteoconductive, and osteoinductive would be of great clinical importance. This study designs and prepares 2D graphene oxide (GO) and black phosphorus (BP) reinforced porous collagen (Col) scaffolds as a viable strategy for treating infectious bone defects. The fabricated Col-GO@BP scaffold exhibited an efficient photothermal antibacterial effect under near-infrared (NIR) irradiation. A further benefit of the NIR-controlled degradation of BP was to promote biomineralization by phosphorus-driven and calcium-extracted phosphorus in situ. The abundant functional groups in GO could synergistically capture the ions and enhance the in situ biomineralization. The Col-GO@BP scaffold facilitated osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSC) by leveraging its mild photothermal effect and biomineralization process, which upregulated heat shock proteins (HSPs) and activated PI3K/Akt pathways. Additionally, systematic in vivo experiments demonstrated that the Col-GO@BP scaffold obviously promotes infectious bone repair through admirable photothermal antibacterial performance and enhanced vascularization. As a result of this study, we provide new insights into the photothermal activity of GO@BP nanosheets, their degradation, and a new biological application for them.

Structural Functions of 3D-Printed Polymer Scaffolds in Regulating Cell Fates and Behaviors for Repairing Bone and Nerve Injuries

Tissue repair and regeneration, such as bone and nerve restoration, face significant challenges due to strict regulations within the immune microenvironment, stem cell differentiation, and key cell behaviors. The development of 3D scaffolds is identified as a promising approach to address these issues via the efficiently structural regulations on cell fates and behaviors. In particular, 3D-printed polymer scaffolds with diverse micro-/nanostructures offer a great potential for mimicking the structures of tissue. Consequently, they are foreseen as promissing pathways for regulating cell fates, including cell phenotype, differentiation of stem cells, as well as the migration and the proliferation of key cells, thereby facilitating tissue repairs and regenerations. Herein, the roles of structural functions of 3D-printed polymer scaffolds in regulating the fates and behaviors of numerous cells related to tissue repair and regeneration, along with their specific influences are highlighted. Additionally, the challenges and outlooks associated with 3D-printed polymer scaffolds with various structures for modulating cell fates are also discussed.

Beyond hype: unveiling the Real challenges in clinical translation of 3D printed bone scaffolds and the fresh prospects of bioprinted organoids

Bone defects pose significant challenges in healthcare, with over 2 million bone repair surgeries performed globally each year. As a burgeoning force in the field of bone tissue engineering, 3D printing offers novel solutions to traditional bone transplantation procedures. However, current 3D-printed bone scaffolds still face three critical challenges in material selection, printing methods, cellular self-organization and co-culture, significantly impeding their clinical application. In this comprehensive review, we delve into the performance criteria that ideal bone scaffolds should possess, with a particular focus on the three core challenges faced by 3D printing technology during clinical translation. We summarize the latest advancements in non-traditional materials and advanced printing techniques, emphasizing the importance of integrating organ-like technologies with bioprinting. This combined approach enables more precise simulation of natural tissue structure and function. Our aim in writing this review is to propose effective strategies to address these challenges and promote the clinical translation of 3D-printed scaffolds for bone defect treatment.

Metal-Organic Framework-Based Nanomaterials for Regulation of the Osteogenic Microenvironment

As the global population ages, bone diseases have become increasingly prevalent in clinical settings. These conditions often involve detrimental factors such as infection, inflammation, and oxidative stress that disrupt bone homeostasis. Addressing these disorders requires exogenous strategies to regulate the osteogenic microenvironment (OME). The exogenous regulation of OME can be divided into four processes: induction, modulation, protection, and support, each serving a specific purpose. To this end, metal-organic frameworks (MOFs) are an emerging focus in nanomedicine, which show tremendous potential due to their superior delivery capability. MOFs play numerous roles in OME regulation such as metal ion donors, drug carriers, nanozymes, and photosensitizers, which have been extensively explored in recent studies. This review presents a comprehensive introduction to the exogenous regulation of OME by MOF-based nanomaterials. By discussing various functional MOF composites, this work aims to inspire and guide the creation of sophisticated and efficient nanomaterials for bone disease management.

Shear Flow-Assembled Janus Membrane with Bifunctional Osteogenic and Antibacterial Effects for Guided Bone Regeneration

Guided bone regeneration (GBR) membranes that reside at the interface between the bone and soft tissues for bone repair attract increasing attention, but currently developed GBR membranes suffer from relatively poor osteogenic and antibacterial effects as well as limited mechanical property and biodegradability. We present here the design and fabrication of a bifunctional Janus GBR membrane based on a shear flow-driven layer by a layer self-assembly approach. The Janus GBR membrane comprises a calcium phosphate-collagen/polyethylene glycol (CaP@COL/PEG) layer and a chitosan/poly(acrylic acid) (CHI/PAA) layer on different sides of a collagen membrane to form a sandwich structure. The membrane exhibits good mechanical stability and tailored biodegradability. It is found that the CaP@COL/PEG layer and CHI/PAA layer contribute to the osteogenic differentiation and antibacterial function, respectively. In comparison with the control group, the Janus GBR membrane displays a 2.52-time and 1.84-time enhancement in respective volume and density of newly generated bone. The greatly improved bone repair ability of the Janus GBR membrane is further confirmed through histological analysis, and it has great potential for practical applications in bone tissue engineering.

Inflammatory microenvironment regulation and osteogenesis promotion by bone-targeting calcium and magnesium repletion nanoplatform for osteoporosis therapy

Osteoporosis is the most common bone metabolic disease that affects the health of middle-aged and elderly people, which is hallmarked by imbalanced bone remodeling and a deteriorating immune microenvironment. Magnesium and calcium are pivotal matrix components that participate in the bone formation process, especially in the immune microenvironment regulation and bone remodeling stages. Nevertheless, how to potently deliver magnesium and calcium to bone tissue remains a challenge. Here, we have constructed a multifunctional nanoplatform composed of calcium-based upconversion nanoparticles and magnesium organic frameworks (CM-NH2-PAA-Ald, denoted as CMPA), which features bone-targeting and pH-responsive properties, effectively regulating the inflammatory microenvironment and promoting the coordination of osteogenic functions for treating osteoporosis. The nanoplatform can efficaciously target bone tissue and gradually degrade in response to the acidic microenvironment of osteoporosis to release magnesium and calcium ions. This study validates that CMPA possessing favorable biocompatibility can suppress inflammation and facilitate osteogenesis to treat osteoporosis. Importantly, high-throughput sequencing results demonstrate that the nanoplatform exerts a good inflammatory regulation effect through inhibition of the nuclear factor kappa-B signaling pathway, thereby normalizing the osteoporotic microenvironment. This collaborative therapeutic strategy that focuses on improving bone microenvironment and promoting osteogenesis provides new insight for the treatment of metabolic diseases such as osteoporosis.

Innovative Biomaterials for Bone Tumor Treatment and Regeneration: Tackling Postoperative Challenges and Charting the Path Forward

Surgical resection of bone tumors is the primary approach employed in the treatment of bone cancer. Simultaneously, perioperative interventions, particularly postoperative adjuvant anticancer strategies, play a crucial role in achieving satisfactory therapeutic outcomes. However, the occurrence of postoperative bone tumor recurrence, metastasis, extensive bone defects, and infection are significant risks that can result in unfavorable prognoses or even treatment failure. In recent years, there has been significant progress in the development of biomaterials, leading to the emergence of new treatment options for bone tumor therapy and bone regeneration. This progress report aims to comprehensively analyze the strategic development of unique therapeutic biomaterials with inherent healing properties and bioactive capabilities for bone tissue regeneration. These composite biomaterials, classified into metallic, inorganic non-metallic, and organic types, are thoroughly investigated for their responses to external stimuli such as light or magnetic fields, internal interventions including chemotherapy or catalytic therapy, and combination therapy, as well as their role in bone regeneration. Additionally, an overview of self-healing materials for osteogenesis is provided and their potential applications in combating osteosarcoma and promoting bone formation are explored. Furthermore, the safety concerns of integrated materials and current limitations are addressed, while also discussing the challenges and future prospects.

Mgp High-Expressing MSCs Orchestrate the Osteoimmune Microenvironment of Collagen/Nanohydroxyapatite-Mediated Bone Regeneration

Activating autologous stem cells after the implantation of biomaterials is an important process to initiate bone regeneration. Although several studies have demonstrated the mechanism of biomaterial-mediated bone regeneration, a comprehensive single-cell level transcriptomic map revealing the influence of biomaterials on regulating the temporal and spatial expression patterns of mesenchymal stem cells (MSCs) is still lacking. Herein, the osteoimmune microenvironment is depicted around the classical collagen/nanohydroxyapatite-based bone repair materials via combining analysis of single-cell RNA sequencing and spatial transcriptomics. A group of functional MSCs with high expression of matrix Gla protein (Mgp) is identified, which may serve as a pioneer subpopulation involved in bone repair. Remarkably, these Mgp high-expressing MSCs (MgphiMSCs) exhibit efficient osteogenic differentiation potential and orchestrate the osteoimmune microenvironment around implanted biomaterials, rewiring the polarization and osteoclastic differentiation of macrophages through the Mdk/Lrp1 ligand-receptor pair. The inhibition of Mdk/Lrp1 activates the pro-inflammatory programs of macrophages and osteoclastogenesis. Meanwhile, multiple immune-cell subsets also exhibit close crosstalk between MgphiMSCs via the secreted phosphoprotein 1 (SPP1) signaling pathway. These cellular profiles and interactions characterized in this study can broaden the understanding of the functional MSC subpopulations at the early stage of biomaterial-mediated bone regeneration and provide the basis for materials-designed strategies that target osteoimmune modulation.

An Injectable Black Phosphorus Hydrogel for Rapid Tooth Extraction Socket Healing

The excess production of reactive oxygen species (ROS) will delay tooth extraction socket (TES) healing. In this study, we developed an injectable thermosensitive hydrogel (NBP@BP@CS) used to treat TES healing. The hydrogel formulation incorporated black phosphorus (BP) nanoflakes, recognized for their accelerated alveolar bone regeneration and ROS-scavenging properties, and dl-3-n-butylphthalide (NBP), a vasodilator aimed at enhancing angiogenesis. In vivo investigations strongly demonstrated that NBP@BP@CS improved TES healing due to antioxidation and promotion of alveolar bone regeneration by BP nanoflakes. The sustained release of NBP from the hydrogel promoted neovascularization and vascular remodeling. Our results demonstrated that the designed thermosensitive hydrogel provided great opportunity not only for ROS elimination but also for the promotion of osteogenesis and angiogenesis, reflecting the "three birds with one stone" concept, and has tremendous potential for rapid TES healing.

The Impact of NLRP3 Inflammasome on Osteoblasts and Osteogenic Differentiation: A Literature Review

Osteoblasts (OBs), which are a crucial type of bone cells, derive from bone marrow mesenchymal stem cells (MSCs). Accumulating evidence suggests inflammatory cytokines can inhibit the differentiation and proliferation of OBs, as well as interfere with their ability to synthesize bone matrix, under inflammatory conditions. NLRP3 inflammasome is closely associated with cellular pyroptosis, which can lead to excessive release of pro-inflammatory cytokines, causing tissue damage and inflammatory responses, however, the comprehensive roles of NLRP3 inflammasome in OBs and their differentiation have not been fully elucidated, making targeting NLRP3 inflammasome approaches to treat diseases related to OBs uncertain. In this review, we provide a summary of NLRP3 inflammasome activation and its impact on OBs. We highlight the significant roles of NLRP3 inflammasome in regulating OBs differentiation and function. Furthermore, current available strategies to affect OBs function and osteogenic differentiation targeting NLRP3 inflammasome are listed and analyzed. Finally, through the prospective discussion, we seek to provide novel insights into the crucial role of NLRP3 inflammasome in diseases related to OBs and offer valuable information for devising treatment strategies.

Black phosphorus, an advanced versatile nanoparticles of antitumor, antibacterial and bone regeneration for OS therapy

Osteosarcoma (OS) is the most common primary malignant bone tumor. In the clinic, usual strategies for OS treatment include surgery, chemotherapy, and radiation. However, all of these therapies have complications that cannot be ignored. Therefore, the search for better OS treatments is urgent. Black phosphorus (BP), a rising star of 2D inorganic nanoparticles, has shown excellent results in OS therapy due to its outstanding photothermal, photodynamic, biodegradable and biocompatible properties. This review aims to present current advances in the use of BP nanoparticles in OS therapy, including the synthesis of BP nanoparticles, properties of BP nanoparticles, types of BP nanoparticles, and modification strategies for BP nanoparticles. In addition, we have discussed comprehensively the application of BP in OS therapy, including single, dual, and multimodal synergistic OS therapies, as well as studies about bone regeneration and antibacterial properties. Finally, we have summarized the conclusions, limitations and perspectives of BP nanoparticles for OS therapy.

A large-scale production of mesenchymal stem cells and their exosomes for an efficient treatment against lung inflammation

Mesenchymal stem cells (MSCs) and their produced exosomes have demonstrated inherent capabilities of inflammation-guided targeting and inflammatory modulation, inspiring their potential applications as biologic agents for inflammatory treatments. However, the clinical applications of stem cell therapies are currently restricted by several challenges, and one of them is the mass production of stem cells to satisfy the therapeutic demands in the clinical bench. Herein, a production of human amnion-derived MSCs (hMSCs) at a scale of over 1 × 109 cells per batch was reported using a three-dimensional (3D) culture technology based on microcarriers coupled with a spinner bioreactor system. The present study revealed that this large-scale production technology improved the inflammation-guided migration and the inflammatory suppression of hMSCs, without altering their major properties as stem cells. Moreover, these large-scale produced hMSCs showed an efficient treatment against the lipopolysaccharide (LPS)-induced lung inflammation in mice models. Notably, exosomes collected from these large-scale produced hMSCs were observed to inherit the efficient inflammatory suppression capability of hMSCs. The present study showed that 3D culture technology using microcarriers coupled with a spinner bioreactor system can be a promising strategy for the large-scale expansion of hMSCs with improved anti-inflammation capability, as well as their secreted exosomes.

Incorporation of black phosphorus nanosheets into poly(propylene fumarate) biodegradable bone cement to enhance bioactivity and osteogenesis

BACKGROUND

Injectable bone cement is commonly used in clinical orthopaedics to fill bone defects, treat vertebral compression fractures, and fix joint prostheses during joint replacement surgery. Poly(propylene fumarate) (PPF) has been proposed as a biodegradable and injectable alternative to polymethylmethacrylate (PMMA) bone cement. Recently, there has been considerable interest in two-dimensional (2D) black phosphorus nanomaterials (BPNSs) in the biomedical field due to their excellent photothermal and osteogenic properties. In this study, we investigated the biological and physicochemical qualities of BPNSs mixed with PPF bone cement created through thermal cross-linking.

METHODS

PPF was prepared through a two-step process, and BPNSs were prepared via a liquid phase stripping method. BP/PPF was subsequently prepared through thermal cross-linking, and its characteristics were thoroughly analysed. The mechanical properties, cytocompatibility, osteogenic performance, degradation performance, photothermal performance, and in vivo toxicity of BP/PPF were evaluated.

RESULTS

BP/PPF exhibited low cytotoxicity levels and mechanical properties similar to that of bone, whereas the inclusion of BPNSs promoted preosteoblast adherence, proliferation, and differentiation on the surface of the bone cement. Furthermore, 200 BP/PPF demonstrated superior cytocompatibility and osteogenic effects, leading to the degradation of PPF bone cement and enabling it to possess photothermal properties. When exposed to an 808-nm laser, the temperature of the bone cement increased to 45-55 °C. Furthermore, haematoxylin and eosin-stained sections from the in vivo toxicity test did not display any anomalous tissue changes.

CONCLUSION

BP/PPF exhibited mechanical properties similar to that of bone: outstanding photothermal properties, cytocompatibility, and osteoinductivity. BP/PPF serves as an effective degradable bone cement and holds great potential in the field of bone regeneration.

Highlights on the Effects of Non-Coding RNAs in the Osteonecrosis of the Jaw

Osteonecrosis of the jaw is the progressive loss and destruction of bone affecting the maxilla or mandible in patients treated with antiresorptive and antiangiogenic agents without receiving prior radiation therapy. The pathogenesis involves the inflammatory pathway of receptor activator of nuclear factor NF-kB ligand and the macrophage colony-stimulating factor, essential for osteoclast precursors survival and proliferation and acting through its receptor c-Fms. Evidence has shown the role of non-coding RNAs in the pathogenesis of osteonecrosis of the jaw and this finding might be useful in diagnosis since these small RNAs could be considered as biomarkers of apoptotic activity in bone. Interestingly, it has been proved that miR-29 and miR-31-5p, acting on specific targets such as CALCR and RhoA, promote programmed-cell death and consequently the necrosis of bone tissue. Specific long non-coding RNAs, instead, have been detected both at reduced levels in patients with multiple myeloma and osteonecrosis, and associated with suppression of osteoblast differentiation, with consequences in the progression of mandible lesions. Among non-coding genic material, circular RNAs have the capability to modify the expression of specific mRNAs responsible for the inhibition of bisphosphonates activity on osteoclastogenesis.

Black Phosphorus Accelerates Bone Regeneration Based on Immunoregulation

A fundamental understanding of inflammation and tissue healing suggests that the precise regulation of the inflammatory phase, both in terms of location and timing, is crucial for bone regeneration. However, achieving the activation of early inflammation without causing chronic inflammation while facilitating quick inflammation regression to promote bone regeneration continues to pose challenges. This study reveals that black phosphorus (BP) accelerates bone regeneration by building an osteogenic immunological microenvironment. BP amplifies the acute pro-inflammatory response and promotes the secretion of anti-inflammatory factors to accelerate inflammation regression and tissue regeneration. Mechanistically, BP creates an osteoimmune-friendly microenvironment by stimulating macrophages to express interleukin 33 (IL-33), amplifying the inflammatory response at an early stage, and promoting the regression of inflammation. In addition, BP-mediated IL-33 expression directly promotes osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), which further facilitates bone repair. To the knowledge, this is the first study to reveal the immunomodulatory potential of BP in bone regeneration through the regulation of both early-stage inflammatory responses and later-stage inflammation resolution, along with the associated molecular mechanisms. This discovery serves as a foundation for the clinical use of BP and is an efficient approach for managing the immune microenvironment during bone regeneration.

Sustained Release of Dexamethasone from 3D-Printed Scaffolds Modulates Macrophage Activation and Enhances Osteogenic Differentiation

Enhancing osteogenesis via modulating immune cells is emerging as a new approach to address the current challenges in repairing bone defects and fractures. However, much remains unknown about the crosstalk between immune cells and osteolineage cells during bone formation. Moreover, biomaterial scaffold-based approaches to effectively modulate this crosstalk to favor bone healing are also lacking. This study is the first to investigate the interactions between macrophages and mesenchymal stem cells (MSCs) in co-cultures with the sustained release of an anti-inflammatory and pro-osteogenesis drug (dexamethasone) from three-dimensional (3D)-printed scaffolds. We successfully achieved the sustained release of dexamethasone from polycaprolactone (PCL) by adding the excipient-sucrose acetate isobutyrate (SAIB). Dexamethasone was released over 35 days in the 17-163 nM range. The osteogenic differentiation of MSCs was enhanced by M1 macrophages at early time points. The late-stage mineralization was dominated by dexamethasone, with little contribution from the macrophages. Besides confirming BMP-2 whose secretion was promoted by both dexamethasone and M1 macrophages as a soluble mediator for enhanced osteogenesis, IL-6 was found to be a possible new soluble factor that mediated osteogenesis in macrophage-MSC co-cultures. The phenotype switching from M1 to M2 was drastically enhanced by the scaffold-released dexamethasone but only marginally by the co-cultured MSCs. Our results offer new insight into macrophage-MSC crosstalk and demonstrate the potential of using drug-release scaffolds to both modulate inflammation and enhance bone regeneration.