Scaffold Guided Bone Regeneration for the Treatment of Large Segmental Defects in Long Bones

Development of Poly(ether sulfone)/Poly(vinyl alcohol)/Magnesium-Doped Carbon Quantum Dot Scaffolds for Bone Tissue Engineering

Bone tissue engineering plays a critical role in overcoming the limitations of traditional bone grafts and implants by enhancing bone integration and regeneration. In this study, we developed a novel membrane scaffold comprising poly(ether sulfone) (PES), poly(vinyl alcohol) (PVA), and magnesium-doped carbon quantum dots (CQDs.Mg) for potential bone tissue engineering applications. Four distinct scaffold formulations (PE-CM0, PE-CM2, PE-CM3, and PE-CM4) were developed using a film applicator machine. The morphology and porosity of the scaffolds, characterized via scanning electron microscopy (SEM), revealed increased porosity with higher CQDs.Mg content. Fourier transform infrared spectroscopy (FTIR) confirmed the successful integration of functional groups from each component. Water contact angle (WCA) measurements indicated improved hydrophilicity with the addition of CQDs.Mg, which is beneficial for cell attachment and proliferation. Mechanical testing demonstrated that the scaffolds maintained adequate tensile strength and flexibility, with PE-CM3 and PE-CM4 exhibiting superior properties. Swelling assays indicated enhanced water absorption with increased CQDs.Mg content, while 14-day degradation studies showed excellent structural stability. Biocompatibility was also assessed using L929 and NIH3T3 cell lines, with cytotoxicity assays demonstrating nearly 100% cell viability across all samples. These findings suggest that the PES/PVA/CQDs.Mg scaffolds exhibit a promising combination of mechanical robustness, hydrophilicity, and biocompatibility, making them strong candidates for bone tissue engineering applications.

Impact of Cerium Doping on the Osteogenic Properties of a 3D Biomimetic Piezoelectric Scaffold with Sustained Mg2+ Release

Background

In the realm of bone tissue engineering, the role of biomimetic piezoelectric scaffolds made from whitlockite (WH) nanoparticles is increasingly recognized. WH, the second most abundant mineral in human bone, possesses piezoelectric properties and the capacity to release magnesium ions (Mg2+), both of which are vital for osteogenic differentiation. This study investigates the osteogenic effects of cerium (Ce) doping on three-dimensional biomimetic piezoelectric scaffolds composed of whitlockite (WH) nanoparticles.

Methods

WH nanoparticles with varying Ce concentrations were synthesized and scaffolds were prepared using a freeze-drying process with sodium alginate as the matrix. In vitro experiments with human bone marrow mesenchymal stem cells (hBMSCs) assessed cell proliferation and differentiation, while animal studies employed a rat calvarial defect model to evaluate new bone formation and mineralization.

Results

Our findings revealed that Ce doping modifies the crystallinity and electrical properties of WH nanoparticles, thereby affecting their osteogenic potential. In vitro studies indicated that scaffolds with a Ce/Ca ratio of 0.06 significantly boosted osteogenic marker expression. Furthermore, animal studies confirmed that Ce-doped WH scaffolds, especially those with the 0.06 ratio, markedly improved both new bone formation and mineralization.

Conclusion

The study demonstrates that Ce doping can significantly enhance the osteogenic properties of WH-based scaffolds, with the optimal Ce/Ca ratio of 0.06 being particularly effective in promoting bone formation. This research provides a promising approach for the development of advanced materials in bone tissue engineering.

From Bone To Blood Flow: Tissue Engineering In Orthopedics - A Narrative Review

Musculoskeletal injuries and degenerative conditions necessitate advanced regenerative solutions. Tissue engineering has emerged as a pivotal field in orthopedic care, particularly in vascularized bone and cartilage regeneration. This narrative review examines the latest advancements in vascular tissue engineering, including scaffold design, cell-based techniques, and growth factor delivery. A comprehensive literature search was conducted using PubMed, ScienceDirect, and Google Scholar, focusing on innovations and challenges in the field. Vascularized bone grafts (VBGs) outperform non-vascularized counterparts in promoting healing and integration. Advances in scaffold materials, such as smart scaffolds and hybrid biomaterials, enhance osteogenesis and angiogenesis. Cellular therapies, utilizing mesenchymal stem cells and induced pluripotent stem cells, synergistically improve vascularization and bone regeneration. Growth factors like VEGF and bone morphogenic protein (BMP-2), integrated with innovative delivery systems, enable sustained angiogenic stimulation and scaffold integration. While significant strides have been made, challenges persist in achieving full vascular integration and replicating native tissue architecture. Innovations in scaffold technology and vascular surgery techniques hold promise for transforming orthopedic tissue engineering and improving patient outcomes.

The Genetic and Biological Basis of Pseudoarthrosis in Fractures: Current Understanding and Future Directions

Pseudoarthrosis-the failure of normal fracture healing-remains a significant orthopedic challenge affecting approximately 10-15% of long bone fractures, and is associated with significant pain, prolonged disability, and repeated surgical interventions. Despite extensive research into the pathophysiological mechanisms of bone healing, diagnostic approaches remain reliant on clinical findings and radiographic evaluations, with little innovation in tools to predict or diagnose non-union. The present review evaluates the current understanding of the genetic and biological basis of pseudoarthrosis and highlights future research directions. Recent studies have highlighted the potential of specific molecules and genetic markers to serve as predictors of unsuccessful fracture healing. Alterations in mesenchymal stromal cell (MSC) function, including diminished osteogenic potential and increased cellular senescence, are central to pseudoarthrosis pathogenesis. Molecular analyses reveal suppressed bone morphogenetic protein (BMP) signaling and elevated levels of its inhibitors, such as Noggin and Gremlin, which impair bone regeneration. Genetic studies have uncovered polymorphisms in BMP, matrix metalloproteinase (MMP), and Wnt signaling pathways, suggesting a genetic predisposition to non-union. Additionally, the biological differences between atrophic and hypertrophic pseudoarthrosis, including variations in vascularity and inflammatory responses, emphasize the need for targeted approaches to management. Emerging biomarkers, such as circulating microRNAs (miRNAs), cytokine profiles, blood-derived MSCs, and other markers (B7-1 and PlGF-1), have the potential to contribute to early detection of at-risk patients and personalized therapeutic approaches. Advancing our understanding of the genetic and biological underpinnings of pseudoarthrosis is essential for the development of innovative diagnostic tools and therapeutic strategies.

Enhanced healing of critical-sized bone defects using degradable scaffolds with tailored composition through immunomodulation and angiogenesis

The impact of orthopedic scaffolds on bone defect healing, particularly the late-stage bone remodeling process, is pivotal for the therapeutic outcome. This study applies fadditively manufactured scaffolds composed of hydroxyapatite-doped poly(lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(lactide-co-glycolide) (HA-PELGA) with varying properties to treat rat calvarial defects, elucidating their significant role in bone remodeling by modulating physiological responses. We engineered two scaffolds with different polylactic acid (PLA) to polyglycolic acid (PGA) ratio (9/1 and 18/1) to vary in hydrophobicity, degradation rate, mechanical properties, and structural stability. These variations influenced physiological responses, including osteogenesis, angiogenesis, and immune reactions, thereby guiding bone remodeling. Our findings show that the HA-PELGA(18/1) scaffold, with a slower degradation rate, supported bulk bone formation due to a stable microenvironment. Conversely, the HA-PELGA(9/1) scaffold, with a faster degradation rate and more active interfaces, facilitated the formation of a thin bone layer and higher bone infiltration. This study demonstrates these degradable scaffolds help to promote bone healing and reveals how scaffold properties influence the bone remodeling process, offering a potential strategy to optimize scaffold design aiming at late-stage bone defect healing.

VEGF loading heparinized hyaluronic acid macroporous hydrogels for enhanced 3D endothelial cell migration and vascularization

The formation of robust vascular systems within voluminous scaffolds remains a formidable barrier in the realm of tissue engineering. There is a growing interest in the integration of biomaterial scaffolds with multiple physical and chemical stimuli to augment the process of vascularization. This study aims to investigate the combined impact of macroporous structures and vascular endothelial growth factor (VEGF) on cell migration and vascularization. Heparinized hyaluronic acid (HepHA) macroporous hydrogels with differing pore sizes, composed by methacrylated hyaluronic acid (HAMA) and methacrylated heparin (HepMA), were fabricated by a gelatin microspheres (GMS) template leaching method. After characterization of their physical properties, VEGF was immobilized on the HepHA hydrogels. The in vitro release study indicated that the HepHA hydrogels can provide sustained release of VEGF. Subsequently, cells migration of human umbilical vein endothelial (HUVECs) assessment indicated that HUVECs cultured on VEGF-loaded HepHA hydrogels with larger pores (VEGF@HepHA250) migrated the furthest. Finally, the hydrogels were implanted and evaluated using a dorsal subcutaneous model. The histological analyses conducted in vivo were consistent with the in vitro results, VEGF@HepHA250 hydrogels exhibited the most pronounced vascularization four weeks post-implantation, indicating that hydrogels with expanded pores and an enriched VEGF promoted angiogenesis within the hydrogels. This study sheds light on the synergistic effects of VEGF release on 3D cell migration and vascularization within hydrogels of differing pore sizes, thus providing novel insights into the strategic design and fabrication of tissue-engineered scaffolds that are amenable to vascularization.

Alveolar bone regeneration using a 3D-printed patient-specific resorbable scaffold for dental implant placement: A case report

BACKGROUND

This case report demonstrates the effective clinical application of a 3D-printed, patient-specific polycaprolactone (PCL) resorbable scaffold for staged alveolar bone augmentation.

OBJECTIVE

To evaluate the effectiveness of a 3D-printed PCL scaffold in facilitating alveolar bone regeneration and subsequent dental implant placement.

MATERIALS AND METHODS

A 46-year-old man with a missing tooth (11) underwent staged alveolar bone augmentation using a patient-specific PCL scaffold. Volumetric bone gain and implant stability were assessed. Histological analysis was conducted to evaluate new bone formation and graft integration.

RESULTS

The novel approach resulted in a volumetric bone gain of 364.69 ± 2.53 mm3, sufficient to reconstruct the original alveolar bone contour and permit dental implant placement. Histological analysis showed new bone presence and successful graft integration across all defect zones (coronal, medial, and apical), with continuous new bone formation around and between graft particles. The dental implant achieved primary stability at 35 Ncm-1, indicating the scaffold's effectiveness in promoting bone regeneration and supporting implant therapy. The post-grafting planned implant position deviated overall by 2.4° compared with the initial restoratively driven implant plan pre-bone augmentation surgery. The patient reported low average daily pain during the first 48 h and no pain from Day 3.

CONCLUSIONS

This proof-of-concept underscores the potential of 3D-printed scaffolds in personalized dental reconstruction and alveolar bone regeneration. It marks a significant step forward in integrating additive manufacturing technologies into clinical practice through a scaffold-guided bone regeneration (SGBR) approach. The trial was registered with the Australian New Zealand Clinical Trials Registry (ACTRN12622000118707p).

Smart Implantable Hydrogel for Large Segmental Bone Regeneration

Large segmental bone defects often lead to nonunion and dysfunction, posing a significant challenge for clinicians. Inspired by the intrinsic bone defect repair logic of "vascularization and then osteogenesis", this study originally reports a smart implantable hydrogel (PDS-DC) with high mechanical properties, controllable scaffold degradation, and timing drug release that can proactively match different bone healing cycles to efficiently promote bone regeneration. The main scaffold of PDS-DC consists of polyacrylamide, polydopamine, and silk fibroin, which endows it with superior interfacial adhesion, structural toughness, and mechanical stiffness. In particular, the adjustment of scaffold cross-linking agent mixing ratio can effectively regulate the in vivo degradation rate of PDS-DC and intelligently satisfy the requirements of different bone defect healing cycles. Ultimately, PDS hydrogel loaded with free desferrioxamine (DFO) and CaCO3 mineralized ZIF-90 loaded bone morphogenetic protein-2 (BMP-2) to stimulate efficient angiogenesis and osteogenesis. Notably, DFO is released rapidly by free diffusion, whereas BMP-2 is released slowly by pH-dependent layer-by-layer disintegration, resulting in a significant difference in release time, thus matching the intrinsic logic of bone defect repair. In vivo and in vitro results confirm that PDS-DC can effectively realize high-quality bone generation and intelligently regulate to adapt to different demands of bone defects.

Dual nanofiber and graphene reinforcement of 3D printed biomimetic supports for bone tissue repair

Replicating the intricate architecture of the extracellular matrix (ECM) is an actual challenge in the field of bone tissue engineering. In the present research study, calcium alginate/cellulose nanofibrils-based 3D printed scaffolds, double-reinforced with chitosan/polyethylene oxide electrospun nanofibers (NFs) and graphene oxide (GO) were prepared using the 3D printing technique. The porous matrix was provided by the calcium alginate, while the anisotropy degree and mechanical properties were ensured by the addition of fillers with different sizes and shapes (CNFs, NFs, GO), similar to the components naturally found in bone ECM. Surface morphology and 3D internal microstructure were analyzed using scanning electron microscopy (SEM) and micro-computed tomography (μ-CT), which evidenced a synergistic effect of the reinforcing and functional fibers addition, as well as of the GO sheets that seem to govern materials structuration. Also, the nanoindentation measurements showed significant differences in the elasticity and viscosity modulus, depending on the measurement point, this supported the anisotropic character of the scaffolds. In vitro assays performed on MG-63 osteoblast cells confirmed the biocompatibility of the calcium alginate-based scaffolds and highlighted the osteostimulatory and mineralization enhancement effect of GO. In virtue of their biocompatibility, structural complexity similar with the one of native bone ECM, and biomimetic mechanical characteristics (e.g. high mechanical strength, durotaxis), these novel materials were considered appropriate for specific functional needs, like guided support for bone tissue formation.

Potential Role of BMP7 in Regenerative Dentistry

In recent years, the field of regenerative dentistry has garnered considerable attention for its focus on restoring and renewing damaged dental tissue. This narrative review explores the potential of bone morphogenetic protein 7 (BMP7) and its diverse applications in the regeneration of dental tissue. Recently, significant efforts have been made to understand BMP7's role in advancing regenerative dentistry. Amongst the various signalling molecules investigated for their regenerative capabilities, BMP7 emerges as a pivotal candidate, demonstrating the ability to stimulate the regeneration of dental pulp, periodontal, craniofacial, and alveolar bone tissues for dental implant placement. Whilst BMP7 exhibits significant promise as a therapeutic agent in regenerative dentistry, further research and clinical trials are necessary to fully unlock its potential and optimise its clinical effectiveness in addressing diverse dental and craniofacial conditions. This review highlights BMP7's substantial potential and emphasises the ongoing need for continued research to effectively harness its clinical utility in diverse dental and craniofacial contexts.

Polysaccharide Hydroxyapatite (Nano)composites and Their Biomedical Applications: An Overview of Recent Years

Hydroxyapatite can combine with polysaccharide originating biomaterials with special applications in the biomedical field. In this review, the synthesis of (nano)composites is discussed, focusing on natural polysaccharides such as alginate, chitosan, and pectin. In this way, advances in recent years in the development of preparing materials are revised and discussed. Therefore, an overview of the recent synthesis and applications of polyssacharides@hydroxyapatites is presented. Several studies based on chitosan@hydroxyapatite combined with other inorganic matrices are highlighted, while pectin@hydroxyapatite is present in a smaller number of reports. Biomedical applications as drug carriers, adsorbents, and bone implants are discussed, combining their dependence with the nature of interactions on the molecular scale and the type of polysaccharides used, which is a relevant aspect to be explored.

Enhancing Guided Bone Regeneration with a Novel Carp Collagen Scaffold: Principles and Applications

Bone defects resulting from trauma, surgery, and congenital, infectious, or oncological diseases are a functional and aesthetic burden for patients. Bone regeneration is a demanding procedure, involving a spectrum of molecular processes and requiring the use of various scaffolds and substances, often yielding an unsatisfactory result. Recently, the new collagen sponge and its structural derivatives manufactured from European carp (Cyprinus carpio) were introduced and patented. Due to its fish origin, the novel scaffold poses no risk of allergic reactions or transfer of zoonoses and additionally shows superior biocompatibility, mechanical stability, adjustable degradation rate, and porosity. In this review, we focus on the basic principles of bone regeneration and describe the characteristics of an "ideal" bone scaffold focusing on guided bone regeneration. Moreover, we suggest several possible applications of this novel material in bone regeneration processes, thus opening new horizons for further research.

Recent trends in bone tissue engineering: a review of materials, methods, and structures

Bone tissue engineering (BTE) provides the treatment possibility for segmental long bone defects that are currently an orthopedic dilemma. This review explains different strategies, from biological, material, and preparation points of view, such as using different stem cells, ceramics, and metals, and their corresponding properties for BTE applications. In addition, factors such as porosity, surface chemistry, hydrophilicity and degradation behavior that affect scaffold success are introduced. Besides, the most widely used production methods that result in porous materials are discussed. Gene delivery and secretome-based therapies are also introduced as a new generation of therapies. This review outlines the positive results and important limitations remaining in the clinical application of novel BTE materials and methods for segmental defects.

Recent Advances in Scaffolds for Guided Bone Regeneration

The rehabilitation of alveolar bone defects of moderate to severe size is often challenging. Currently, the therapeutic approaches used include, among others, the guided bone regeneration technique combined with various bone grafts. Although these techniques are widely applied, several limitations and complications have been reported such as morbidity, suboptimal graft/membrane resorption rate, low structural integrity, and dimensional stability. Thus, the development of biomimetic scaffolds with tailor-made characteristics that can modulate cell and tissue interaction may be a promising tool. This article presents a critical consideration in scaffold's design and development while also providing information on various fabrication methods of these nanosystems. Their utilization as delivery systems will also be mentioned.

Cold physical plasma treatment optimization for improved bone allograft processing

In musculoskeletal surgery, the treatment of large bone defects is challenging and can require the use of bone graft substitutes to restore mechanical stability and promote host-mediated regeneration. The use of bone allografts is well-established in many bone regenerative procedures, but is associated with low rates of ingrowth due to pre-therapeutic graft processing. Cold physical plasma (CPP), a partially ionized gas that simultaneously generates reactive oxygen (O2) and nitrogen (N2) species, is suggested to be advantageous in biomedical implant processing. CPP is a promising tool in allograft processing for improving surface characteristics of bone allografts towards enhanced cellularization and osteoconduction. However, a preclinical assessment regarding the feasibility of pre-therapeutic processing of allogeneic bone grafts with CPP has not yet been performed. Thus, this pilot study aimed to analyze the bone morphology of CPP processed allografts using synchrotron radiation-based microcomputed tomography (SR-µCT) and to analyze the effects of CPP processing on human bone cell viability and function. The analyzes, including co-registration of pre- and post-treatment SR-µCT scans, revealed that the main bone morphological properties (total volume, mineralized volume, surface area, and porosity) remained unaffected by CPP treatment if compared to allografts not treated with CPP. Varying effects on cellular metabolic activity and alkaline phosphatase activity were found in response to different gas mixtures and treatment durations employed for CPP application. It was found that 3 min CPP treatment using a He + 0.1% N2 gas mixture led to the most favourable outcome regarding a significant increase in bone cell viability and alkaline phosphatase activity. This study highlights the promising potential of pre-therapeuthic bone allograft processing by CPP prior to intraoperative application and emphasizes the need for gas source and treatment time optimization for specific applications.

Resorbable GBR Scaffolds in Oral and Maxillofacial Tissue Engineering: Design, Fabrication, and Applications

Guided bone regeneration (GBR) is a promising technique in bone tissue engineering that aims to replace lost or injured bone using resorbable scaffolds. The promotion of osteoblast adhesion, migration, and proliferation is greatly aided by GBR materials, and surface changes are critical in imitating the natural bone structure to improve cellular responses. Moreover, the interactions between bioresponsive scaffolds, growth factors (GFs), immune cells, and stromal progenitor cells are essential in promoting bone regeneration. This literature review comprehensively discusses various aspects of resorbable scaffolds in bone tissue engineering, encompassing scaffold design, materials, fabrication techniques, and advanced manufacturing methods, including three-dimensional printing. In addition, this review explores surface modifications to replicate native bone structures and their impact on cellular responses. Moreover, the mechanisms of bone regeneration are described, providing information on how immune cells, GFs, and bioresponsive scaffolds orchestrate tissue healing. Practical applications in clinical settings are presented to underscore the importance of these principles in promoting tissue integration, healing, and regeneration. Furthermore, this literature review delves into emerging areas of metamaterials and artificial intelligence applications in tissue engineering and regenerative medicine. These interdisciplinary approaches hold immense promise for furthering bone tissue engineering and improving therapeutic outcomes, leading to enhanced patient well-being. The potential of combining material science, advanced manufacturing, and cellular biology is showcased as a pathway to advance bone tissue engineering, addressing a variety of clinical needs and challenges. By providing this comprehensive narrative, a detailed, up-to-date account of resorbable scaffolds' role in bone tissue engineering and their transformative potential is offered.

The Concept of Scaffold-Guided Bone Regeneration for the Treatment of Long Bone Defects: Current Clinical Application and Future Perspective

The treatment of bone defects remains a challenging clinical problem with high reintervention rates, morbidity, and resulting significant healthcare costs. Surgical techniques are constantly evolving, but outcomes can be influenced by several parameters, including the patient's age, comorbidities, systemic disorders, the anatomical location of the defect, and the surgeon's preference and experience. The most used therapeutic modalities for the regeneration of long bone defects include distraction osteogenesis (bone transport), free vascularized fibular grafts, the Masquelet technique, allograft, and (arthroplasty with) mega-prostheses. Over the past 25 years, three-dimensional (3D) printing, a breakthrough layer-by-layer manufacturing technology that produces final parts directly from 3D model data, has taken off and transformed the treatment of bone defects by enabling personalized therapies with highly porous 3D-printed implants tailored to the patient. Therefore, to reduce the morbidities and complications associated with current treatment regimens, efforts have been made in translational research toward 3D-printed scaffolds to facilitate bone regeneration. Three-dimensional printed scaffolds should not only provide osteoconductive surfaces for cell attachment and subsequent bone formation but also provide physical support and containment of bone graft material during the regeneration process, enhancing bone ingrowth, while simultaneously, orthopaedic implants supply mechanical strength with rigid, stable external and/or internal fixation. In this perspective review, we focus on elaborating on the history of bone defect treatment methods and assessing current treatment approaches as well as recent developments, including existing evidence on the advantages and disadvantages of 3D-printed scaffolds for bone defect regeneration. Furthermore, it is evident that the regulatory framework and organization and financing of evidence-based clinical trials remains very complex, and new challenges for non-biodegradable and biodegradable 3D-printed scaffolds for bone regeneration are emerging that have not yet been sufficiently addressed, such as guideline development for specific surgical indications, clinically feasible design concepts for needed multicentre international preclinical and clinical trials, the current medico-legal status, and reimbursement. These challenges underscore the need for intensive exchange and open and honest debate among leaders in the field. This goal can be addressed in a well-planned and focused stakeholder workshop on the topic of patient-specific 3D-printed scaffolds for long bone defect regeneration, as proposed in this perspective review.