Bone grafts and biomaterials substitutes for bone defect repair: A review

A double network composite hydrogel with enhanced transdermal delivery by ultrasound for endometrial injury repair and fertility recovery

Endometrial injury and resulting female infertility pose significant clinical challenges due to the notable shortcomings of traditional treatments. Herein, we proposed a double network composite hydrogel, CSMA-RC-Zn-PNS, which forms a physical barrier on damaged tissue through photo-crosslinking while enabling sustained release of the active ingredient PNS. Based on this, we developed a combined strategy to enhance transdermal delivery efficiency using ultrasound cavitation. In vitro experiments demonstrated that CSMA-RC-Zn-PNS exhibits excellent biosafety, biodegradability, and promotes cell proliferation, migration, and tube formation, along with antioxidant and antibacterial properties. In a rat endometrial injury model, the ultrasound cavitation effect was demonstrated to enhance transdermal delivery efficiency, and the ability of CSMA-RC-Zn-PNS to promote endometrial regeneration, anti-fibrosis and fertility restoration was verified. Overall, this strategy combining CSMA-RC-Zn-PNS hydrogel and ultrasound treatment shows promising applications in endometrial regeneration and female reproductive health.

Mineralized cellulose nanofibers reinforced bioactive hydrogel remodels the osteogenic and angiogenic microenvironment for enhancing bone regeneration

Slow osteogenesis and insufficient vascularization remain significant challenges in achieving effective bone repair and functional restoration with tissue-engineered scaffolds. Herein, a novel mineralized nanofibers reinforced bioactive hydrogel was designed to enhance bone regeneration inspired from the structural and functional properties of the bone tissue extracellular matrix (ECM). This bioactive hydrogel integrated enzymatically mineralized TEMPO-oxidized bacterial cellulose (m-TOBC) nanofibers and mesoporous silica nanoparticles (MSNs) loaded with the angiogenic drug dimethyloxalylglycine (DMOG) into gelatin methacryloyl (GelMA). The m-TOBC nanofibers achieved one stone, three birds: improving the printability of GelMA ink, mechanical properties, and osteoconduction of the hydrogel. The incorporation of MSNs loaded with DMOG fostered an angiogenic microenvironment through the release of DMOG. Results indicated that the bioactive hydrogel significantly enhanced in vitro mineralized matrix deposition and osteoblastic alkaline phosphatase expression. Additionally, the bioactive hydrogel had good ability to promote angiogenesis in terms of enhanced endothelial cell migration, tube formation, and upregulated angiogenic genes expression levels. In a critical-sized rat cranial defect model, the bioactive hydrogel significantly enhanced bone regeneration. Overall, this research offered a promising strategy to design nanofibers enhanced hydrogel to remodel osteogenic and angiogenic microenvironment for enhancing bone repair.

Multiscale metal-based nanocomposites for bone and joint disease therapies

Bone and joint diseases are debilitating conditions that can result in significant functional impairment or even permanent disability. Multiscale metal-based nanocomposites, which integrate hierarchical structures ranging from the nanoscale to the macroscale, have emerged as a promising solution to this challenge. These materials combine the unique properties of metal-based nanoparticles (MNPs), such as enzyme-like activities, stimuli responsiveness, and photothermal conversion, with advanced manufacturing techniques, such as 3D printing and biohybrid systems. The integration of MNPs within polymer or ceramic matrices offers a degree of control over the mechanical strength, antimicrobial efficacy, and the manner of drug delivery, whilst concomitantly promoting the processes of osteogenesis and chondrogenesis. This review highlights breakthroughs in stimulus-responsive MNPs (e.g., photo-, magnetically-, or pH-activated systems) for on-demand therapy and their integration with biocomposite hybrids containing cells or extracellular vesicles to mimic the native tissue microenvironment. The applications of these composites are extensive, ranging from bone defects, infections, tumors, to degenerative joint diseases. The review emphasizes the enhanced load-bearing capacity, bioactivity, and tissue integration that can be achieved through hierarchical designs. Notwithstanding the potential of these applications, significant barriers to progress persist, including challenges related to long-term biocompatibility, regulatory hurdles, and scalable manufacturing. Finally, we propose future directions, including machine learning-guided design and patient-specific biomanufacturing to accelerate clinical translation. Multiscale metal-based nanocomposites, which bridge nanoscale innovations with macroscale functionality, are a revolutionary force in the field of biomedical engineering, providing personalized regenerative solutions for bone and joint diseases.

"Disguise strategy" to bacteria: A multifunctional hydrogel with bacteria-targeting and photothermal conversion properties for the repair of infectious bone defects

Addressing the challenge of eliminating bacteria and stimulating osteogenesis in infectious bone defects, where cells and bacteria coexist within the microenvironment, presents a significant hurdle. In this study, a strategy of targeting bacteria is proposed to address this challenge. For this purpose, a methacrylated gelatin composite hydrogel containing zinc ion and D-type cysteine-modified polydopamine nanoparticles (PZC) is developed. The D-cysteine, involved in the metabolism of the bacterial peptidoglycan chain, allows PZC to specifically target bacteria, exhibiting a form of "disguise strategy". Through the targeting effect, this composite hydrogel can selectively kill bacteria and promote osteogenesis combing photothermal therapy with Zn2+ release, which showcases spatial controllability. Moreover, the antibacterial ability will be further improved after Near-infrared light irradiation. The multifunctional hydrogel containing Zn2+ modified nanoparticles can also promote osteogenic differentiation of bone marrow stem cells. Animal studies have revealed that the multifunctional hydrogel can inhibit bacteria growth and promote repair of infectious bone defects in rats. Findings from this study imply that endowing the nanoparticles with bacteria-targeting function can precisely control the events in cells and bacteria in the complex microenvironment, which can provide insights for the treatment of complex diseases with antibacterial requirements.

Universal Hydrogel Carrier Enhances Bone Graft Success: Preclinical and Clinical Evaluation

Orthopedic, maxillofacial, and complex dentoalveolar bone grafting procedures that require donor-site bone harvesting can be associated with post-surgical complications. There has been widespread adoption of exogenously sourced particulate bone graft materials (BGM) for bone regenerative procedures; however, the particulate nature of these materials may lead to compromised healing outcomes, mainly attributed to structural collapse of the BGM, prolonged tissue healing. In this study, a fully synthetic thermoresponsive hydrogel-based universal carrier matrix (TX) that forms flowable and shapable putties with different BGMs while spatially preserving the particles in a 3D scaffold at the implantation site is introduced. The potential synergistic effect of the carrier is investigated in combination with particulate demineralized bone matrix (DBM) in a standard muscle pouch nude mice model (n = 24) as well as in a rabbit femoral critical-sized cortico-cancellous bone defect model (n = 9). Finally, the clinical usability, safety, and efficacy of the carrier for the delivery of deproteinized bovine bone mineral (DBBM) are evaluated in a controlled clinical trial for extraction socket alveolar ridge preservation (ARP) (n = 11 participants). Overall, the TX carrier improved the delivery of different types of BGMs, maintaining these spatially at the implantation site with minimal inflammatory responses, resulting in favorable bone regenerative outcomes.

A Quantitative Evaluation of the Efficacy of Endochondral Ossification-Based Grafts in Bone Defect Regeneration: An Analysis of Animal Studies

The regeneration of bone defects through bone grafts primarily depends on two strategies: intramembrane ossification (IO) and endochondral ossification (EO). Traditional bone tissue engineering has focused on mimicking the IO process to stimulate the formation of a bone-like matrix. However, repair strategies based on IO often result in excessive deposition of the matrix on the graft surface, hindering bone tissue regeneration. In recent years, researchers have increasingly focused on investigating the reparative potential of EO-based grafts for bone defects, such as microspheres, pellets, and hydrogel. However, the effectiveness of EO-based grafts on bone defects has not yet been quantitatively evaluated. Therefore, this study conducted a systematic review and meta-analysis of previous studies to quantitatively assess the bone regenerative potential of EO-based grafts. The results revealed that EO-based grafts showed favorable ability for bone regeneration. However, there was no significant difference in bone regeneration between EO-based grafts that utilized chondrogenic differentiation or hypertrophic differentiation. Additionally, the results demonstrated low quality in the experimental methods and the reporting of animal studies as well as a low quality of evidence provided by the included studies. Based on this, we propose three suggestions to enhance the quality of experimental methods and reporting in animal experiments. Furthermore, it is essential to conduct more evidence-based research to establish reliable evidence for the clinical application of EO-based grafts.

In vitro characterization of 3D printed polycaprolactone/graphene oxide scaffolds impregnated with alginate and gelatin hydrogels for bone tissue engineering

To achieve successful bone tissue engineering (BTE), it is necessary to fabricate a biomedical scaffold with appropriate structure as well as favorable composition. Despite a broad range of studies, this remains a challenge, highlighting the need for a better understanding of how structural features (e.g., pore size) and scaffold composition influence mechanical and physical properties, as well as cellular behavior. Therefore, the objective of this study was to characterize physical properties (swelling, degradation), mechanical properties (compressive modulus), and cellular behavior in relation to varying compositions (referred to composite and hybrid scaffolds) as well as varying pore sizes in three-dimensional (3D) printed scaffolds. Composite scaffolds were fabricated from polycaprolactone (PCL) and two different graphene oxide (GO) (3% and 9% (w/v)) concentrations. Additionally, hybrid scaffolds were fabricated by impregnating 3D printed scaffolds in a hydrogel blend of alginate/gelatin. Pore sizes of 400, 1000, and 1500 μm were investigated in this study to assess their effect on the scaffold properties. Our findings showed that swelling and degradation properties were enhanced by (I) the addition of GO as well as introduction of both hydrogel and highest concentration of GO (9% (w/v) GO) into the polymeric matrix of PCL, and (II) increasing the pore size within the scaffolds. Mechanical testing revealed that compressive elastic modulus increased with decreasing pore size, incorporation of GO, and increasing GO content into the matrix of PCL. Although our investigated scaffolds with various pore sizes did not show comparable elastic moduli to that of cortical bone, they exhibited an elastic modulus range (∼31-48 MPa) matching that of trabecular bone. The highest compressive modulus (∼48 MPa) was observed in scaffolds of PCL/9% (w/v) GO (composite scaffolds) with the pore size of 400 μm. Cell viability assay demonstrated high MG-63 cell survival (greater than 70%) in all composite and hybrid scaffolds (indicating scaffold biocompatibility) except PCL/3% (w/v) GO scaffolds. The findings of this study contribute to the field of BTE by providing scaffold design insights in terms of pore size and composition.

Probiotics and nanoparticle-mediated nutrient delivery in the management of transfusion-supported diseases

Bone marrow is vital for hematopoiesis, producing blood cells essential for oxygen transport, immune defense, and clotting. However, disorders like leukemia, lymphoma, aplastic anemia, and myelodysplastic syndromes can severely disrupt its function, leading to life-threatening complications. Traditional treatments, including chemotherapy and stem cell transplants, have significantly improved patient outcomes but are often associated with severe side effects and limitations, necessitating the exploration of safer, more targeted therapeutic strategies. Nanotechnology has emerged as a promising approach for addressing these challenges, particularly in the delivery of nutraceuticals-bioactive compounds derived from food sources with potential therapeutic benefits. Despite their promise, nutraceuticals often face clinical limitations due to poor bioavailability, instability, and inefficient delivery to target sites. Nanoparticles offer a viable solution by enhancing the stability, absorption, and targeted transport of nutraceuticals to bone marrow while minimizing systemic side effects. This study explores a range of bone marrow disorders, conventional treatment modalities, and the potential of nanoparticles to enhance nutraceutical-based therapies. By improving targeted delivery and therapeutic efficacy, nanoparticles could revolutionize bone marrow disease management, providing patients with more effective and less invasive treatment options. These advancements represent a significant step toward safer and more efficient therapeutic approaches, ultimately improving patient prognosis and overall health.

Sintering 3D-Printed Hydroxyapatite-Wollastonite Lattices Improve Bioactivity and Mechanical Integrity for Bone Composite Scaffolds

The advancement of bone tissue engineering relies on the development of scaffolds that combine structural integrity with bioactivity. This study introduces a novel composite scaffold integrating three-dimensional (3D) printed hydroxyapatite (HA)-wollastonite (WOL) gyroid lattices with chitosan-gelatin cryogels, designed to fulfill these dual requirements. The HA-WOL lattices were fabricated using digital light processing (DLP) 3D-printing and subjected to optimized thermal treatment cycles demonstrating statistically superior compressive modulus and ultimate strength. This thermal process facilitated the phase transformation of HA-WOL to bioactive β-tricalcium phosphate (β-TCP) and silicocarnotite mixed phases, with MG63 (osteoblast-like) cell culture revealing significantly enhanced viability and biocompatibility. The chitosan-gelatin polymer network was successfully incorporated into the lattice, resulting in a composite scaffold with retained relative swelling capacity, improved mechanical stability, and superior bioactivity compared to cryogel-only constructs. Additional MG63 cell culture studies revealed that the composite scaffold supported cell viability and proliferation into the constructs, demonstrating its potential to conduct tissue regeneration across bone defects. This work highlights the synergistic effects of integrating bioactive ceramics with polymer-based cryogels, offering a promising solution to address bone regeneration in orthopaedic reconstruction. Future research will focus on in vivo validation and optimization of scaffold architecture to further enhance clinical relevance. This study paves the way for next-generation composite scaffolds capable of bridging the gap between mechanical integrity and biological performance in bone regeneration.

Exploring the role of strontium-based nanoparticles in modulating bone regeneration and antimicrobial resistance: a public health perspective

Strontium-based nanoparticles (SrNPs) have emerged as a versatile and promising class of nanomaterials with a wide range of potential applications in healthcare, particularly in the fields of bone regeneration and combating antimicrobial resistance (AMR). Recent research has highlighted the unique properties of SrNPs, including their ability to promote osteogenesis, enhance bone healing, and exhibit strong antimicrobial activity against multidrug-resistant pathogens. These attributes position SrNPs as innovative therapeutic agents with the potential to address challenges such as osteoporosis, bone infections, and the growing global AMR crisis. This comprehensive review critically examines the dual functional potential of SrNPs by analyzing their synthesis methods, physicochemical properties, biological interactions, and translational applications in orthopedic and antimicrobial therapies. Specifically, the review emphasizes SrNPs' ability to enhance bone density, accelerate fracture healing, and reduce the economic burden associated with prolonged treatment and rehabilitation for bone-related diseases. Furthermore, their novel application as antimicrobial agents is explored, highlighting their ability to target bacterial metabolic pathways and combat the rise of antibiotic resistance. The review focuses on the synthesis methods used for SrNPs, particularly co-precipitation, hydrothermal synthesis, and sol-gel techniques. Each method is explored for its ability to produce SrNPs with controlled size, shape, and functionality, while addressing their scalability, cost-effectiveness, and environmental impact. Additionally, the toxicological risks associated with SrNPs are also explored, emphasizing the need for comprehensive preclinical and clinical evaluations to ensure safety for humans and ecosystems. The regulatory and ethical landscape of SrNPs highlights the need for global safety protocols, equitable access, and international cooperation to ensure ethical nanotechnology use. Environmental fate studies address bioaccumulation risks and ecological concerns. This review identifies opportunities and challenges in advancing bone regenerative medicine and combating AMR while emphasizing sustainable and ethical SrNP development for researchers, policymakers, and stakeholders.

Mechanical and biological properties of 3D printed bone tissue engineering scaffolds

Bone defects have historically represented a significant challenge in clinical practice, with traditional surgical intervention remaining the gold standard for their management. However, due to the problem of the origin of autologous and allogeneic bone and the complex and diverse bone defects, traditional surgical methods sometimes cannot meet the treatment needs and expectations of patients. The development of bone tissue engineering and 3D printing technology provides new ideas for bone defect repair. Ideal bioscaffold materials must have good mechanical properties, biocompatibility, osteoinduction and bone conduction capabilities. Additionally, factors such as degradation rate, appropriate porosity and a sustained antibacterial effect must be taken into account. The combination of 3D printing technology and synthetic composite biomaterial scaffolds has become a well-established approach in the treatment of complex bone defects, offering innovative solutions for bone defect repair. The combined application of seed cells, signalling factors and biological scaffolds is also beneficial to improve the therapeutic effect of complex bone defects. This article will therefore examine some of the most commonly used 3D printing technologies for biological scaffolds and the most prevalent bioscaffold materials suitable for 3D printing. An analysis will be conducted on the mechanical and biological properties of these materials to elucidate their respective advantages and limitations.

Local antibiotic delivery: Recent basic and translational science insights in orthopedics

BACKGROUND

Infections remain a significant challenge in orthopedic settings despite advancements in preventive measures. Antibiotics are the primary defense against infections, but optimal delivery methods to the infection site are still being investigated. This review aims to examine existing approaches for local drug delivery from a basic science perspective.

RECENT FINDINGS

Achieving adequate antibiotic concentration at the infection site is challenging due to compromised vasculature in ischemic conditions. Local administration methods, including antibiotic-loaded carriers such as impregnated bone grafts and various bone substitutes, are being explored as alternatives to systemic antibiotic use.

SUMMARY

Various materials, including polymethyl methacrylate (PMMA), hydroxyapatite, calcium phosphate/sulfate, bone glass, and hydrogel, are being investigated for local antibiotic delivery. Some of these materials possess inherent antibacterial properties due to their chemical interactions. The selection of appropriate antibiotics, their dosage, release kinetics from the carrier material, physical behavior of the material/graft, and biocompatibility are key areas for further investigation in basic science research.

Functionalized zeolite regulates bone metabolic microenvironment

The regulation of bone metabolic microenvironment imbalances in diseases such as osteoporosis, bone defects, infections, and tumors remains a significant challenge in orthopedics. Therefore, it has become urgent to develop biomaterials with effective bone metabolic microenvironmental regulatory functions. Zeolites, as advanced biomedical materials, possess distinctive physicochemical properties such as multi-level pore structures, adjustable frameworks, easily modifiable surfaces, and excellent adsorption capabilities. These advantageous characteristics give zeolites broad application prospects in regulating the bone metabolic microenvironment. Therefore, this paper first classifies zeolites used to regulate the bone metabolic microenvironment based on their topological structures and compositional frameworks. Subsequently, it provides a detailed description of modification strategies for zeolite materials aimed at regulating this microenvironment. Next, a comprehensive summary was provided on the preparation strategies for zeolite materials aimed at regulating the bone metabolic microenvironment. Additionally, the paper focuses on the specific applications of zeolite materials in conditions of bone metabolic imbalance, such as osteoporosis, bone defects, orthopedic infections, and bone tumors, highlighting their potential in enhancing osteogenic microenvironments, controlling infections, and treating bone tumors. Finally, it outlines the prospects and challenges associated with the application of zeolites in regulating the bone metabolic microenvironment. This review comprehensively summarizes zeolites used for bone metabolic regulation, aiming to provide guidance for future research and application development.

Enhancing Immunomodulation and Osseointegration of Bone Implants via Thrombin-Activated Platelet-Rich Plasma Self-Assembly

Platelet-rich plasma (PRP) is characterized by elevated concentrations of growth factors that facilitate bone repair. Nonetheless, the effective integration of PRP with bone implants and the sustained release of its active constituents pose significant challenges. In this study, thrombin is grafted onto the surface of polyetheretherketone (PEEK) via an N,N'-Disuccinimidyl Carbonate (DSC) linker and the retained enzymatic activity of thrombin enables the controlled activation of PRP self-assembly, resulting in the formation of a functional bio-gel layer. The optimal thrombin concentration to be 100 U/ mL-1 is determined, at which point both the grafting amount and enzymatic activity of thrombin reaches their peak, with no further increases observed at higher concentrations. PRP solutions with varying platelet enrichment ratios are subsequently activated on the thrombin-grafted PEEK surface, yielding self-assembled bio-gels capable of sustained growth factor release for up to 16 days. The thrombin-activated PRP bio-gel on PEEK surface not only enhances in vitro cell adhesion, proliferation, osteogenic differentiation, vascularization and specific polarization of macrophages, but also effectively facilitates in vivo angiogenesis, immunomodulation and bone formation in a platelet dose-dependent manner. Consequently, the thrombin-activated PRP gel presents a promising strategy for the biological functionalization of PEEK implants in orthopedic applications.

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.

Addressing the challenges of infectious bone defects: a review of recent advances in bifunctional biomaterials

Infectious bone defects present a substantial clinical challenge due to the complex interplay between infection control and bone regeneration. These defects often result from trauma, autoimmune diseases, infections, or tumors, requiring a nuanced approach that simultaneously addresses infection and promotes tissue repair. Recent advances in tissue engineering and materials science, particularly in nanomaterials and nano-drug formulations, have led to the development of bifunctional biomaterials with combined osteogenic and antibacterial properties. These materials offer an alternative to traditional bone grafts, minimizing complications such as multiple surgeries, high antibiotic dosages, and lengthy recovery periods. This review examines the repair mechanisms in the infectious microenvironment and highlights various bifunctional biomaterials that foster both anti-infective and osteogenic processes. Emerging design strategies are also discussed to provide a forward-looking perspective on treating infectious bone defects with clinically significant outcomes.

Functional polysaccharide-based hydrogel in bone regeneration: From fundamentals to advanced applications

Bone regeneration is limited and generally requires external intervention to promote effective repair. Autografts, allografts, and xenografts as traditional methods for addressing bone defects have been widely utilized, their clinical applicability is limited due to their respective disadvantages. Fortunately, functional polysaccharide hydrogels have gained significant attention in bone regeneration due to their exceptional drug-loading capacity, biocompatibility, and ease of chemical modification. They also provide an optimal microenvironment for bone repair and regeneration. This review provides an overview of various functional polysaccharide hydrogels derived from biocompatible materials, focusing on their applications in intelligent delivery systems, bone tissue regeneration, and cartilage defect repair. Particularly, the incorporation of bioactive molecules into the design of functional polysaccharide hydrogels has been shown to significantly enhance bone regeneration. Additionally, this review emphasizes the preparation methods for functional polysaccharide hydrogels and associated the bone healing mechanisms. Finally, the limitations and future prospects of functional polysaccharide hydrogels are thoroughly evaluated.

Progress of porous tantalum surface-modified biomaterial coatings in bone tissue engineering

Tantalum (Ta) metal has emerged as a prominent material within the realm of bone tissue engineering, owing to its favorable biocompatibility, commendable mechanical attributes, and notable biological properties such as osteoconductivity, osteoinductivity, and angiogenic potential. However, as clinical applications have expanded, Ta implants have unveiled a spectrum of limitations. Consequently, porous tantalum (PTa) has garnered escalating interest, attributable to its unique microstructural attributes, tunable mechanical characteristics, and inherent biocompatibility. Various methodologies have been proposed to modify the surface of PTa, with the aim of accelerating and enhancing osseous integration while fostering more robust osseointegration. Strategic surface modifications have the potential to augment the inherent advantages of PTa, thereby offering diverse avenues for exploration within the realm of surface effects on PTa. This review elucidates the ongoing research endeavors concerning diverse biomaterial coatings applied to PTa surfaces in the context of bone tissue engineering.

An insightful overview on osteogenic potential of nano hydroxyapatite for bone regeneration

The orthopaedic surgeries were greatly aided by bone grafting with the use of nanomaterials which provide new strategies for bone regeneration, despite the significant drawbacks of traditional treatments. Hydroxyapatite is one of the bioactive ceramics that has gained substantial research attention due to its biocompatibility, bioactivity and osteointegration ability for the manufacturing of nano bone grafts. The organized complex and porous structures of the human bone tissue is a nanocomposite which consists of both organic and inorganic matrix including hydroxyapatite naturally. Conventional hydroxyapatite was known to provide good adhesion and proliferation of host cells but very low mechanical strength. Hence biomaterial made of hydroxyapatite with various polymers and cross linking agents were used to enhance the mechanical strength of the material. Out of 293 articles obtained from the literature search, only 90 articles met the inclusion criteria about bone regeneration using nano hydroxyapatite materials. The present review addresses the potential capping agents with plant extracts for the synthesis of hydroxyapatite nanomaterials with multi-functional applications include drug delivery for targeting the desired therapeutic effect for bone regeneration with osteoprotective ability and tumour therapy.

Stabilization of Osteoporotic Pelvis and Acetabular Fractures

Background

The surgical management of osteoporotic pelviacetabular fractures poses distinct challenges due to poor screw purchase, severe comminution of fractures, and the inability to perform prolonged surgeries in patients with significant comorbidities. These fractures necessitate tailored modifications in surgical approaches, implant selection, and techniques based on the patient's overall health, fracture complexity, and bone quality.

Methods

A comprehensive literature search was conducted using PubMed and Google Scholar databases to identify relevant articles on the management of osteoporotic pelvi-acetabular fractures.

Results

Implant selection plays a pivotal role in addressing the fragility of osteoporotic fractures. Specialized implants, such as locking plates with multidirectional screw holes, along with augmentation using polymethylmethacrylate (PMMA) or bone substitutes, enhance screw fixation in compromised bone. Sacral fractures, which are commonly involved, are often managed with percutaneous fixation using long cancellous screws. Minimally invasive long-screw fixation techniques are particularly effective for less displaced acetabular fractures. For displaced acetabular fractures with articular impaction, fracture elevation and stabilization using bone grafts or bone graft substitutes are crucial. When feasible, less invasive surgical techniques are preferred to minimize operative trauma. In some cases, the fixation of acetabular fractures in osteoporotic bone may fail over time, necessitating conversion to total hip arthroplasty (THA). For fractures with severe comminution, primary THA combined with column reduction and fixation is frequently a safer and more effective approach. Early postoperative mobilization is critical to reduce the risk of complications such as deep vein thrombosis and pressure ulcers.

Conclusion

The stabilization of osteoporotic pelvic and acetabular fractures requires a multifaceted approach incorporating advanced surgical techniques, specialized implants, and augmentation methods. Early mobilization and individualized postoperative management are essential for optimizing patient outcomes and minimizing complications.

Faster Bone Gap Union in Medial Opening Wedge High Tibial Osteotomy With 3D-Printed Synthetic Bioresorbable Polycaprolactone and Tricalcium Phosphate Osteotomy Gap Fillers Compared to Allogeneic Osteotomy Gap Fillers: A Retrospective Matched-Pair Cohort Study

OBJECTIVE

The use of synthetic bone substitute material (BSM) as osteotomy gap fillers have been reported to improve outcomes in medial opening wedge high tibial osteotomy (MOWHTO). This study aims to evaluate the early radiological outcomes (bone union) and complication rates of the novel patient-specific 3D-printed honeycomb-structured polycaprolactone and tricalcium phosphate (PCL-TCP) synthetic graft compared to allogeneic bone grafts as an osteotomy gap filler in MOWHTO.

METHODS

A retrospective matched-pair analysis of patients who underwent MOWHTO with either PCL-TCP synthetic graft or allogenic femoral head allograft as osteotomy gap filler was performed. The osteotomy gap was split into equal zones (Zone 1-5), and bone union was evaluated on anteroposterior radiographs based on the van Hemert classification at 1, 3, 6, and 12 months postoperatively. Postoperative complications including infection, lateral hinge fractures, and persistent pain was measured. The study and control group were matched for age, smoking status, diabetes mellitus, and osteotomy gap size.

RESULTS

Significantly greater bone union progression was observed in the PCL-TCP group than in the allograft group at 1 month (Zones 1-3), 3 months (Zones 1-4), 6 months (Zones 1-2, 4), and 12 months (Zones 2-3, 5) postoperatively (P < 0.05). No significant difference in complications rates was noted between the two groups at 1 year.

CONCLUSIONS

Bone union rates observed in patients who underwent MOWHTO with the PCL-TCP synthetic graft osteotomy gap filler were superior to those in the allograft group at 1 year postoperatively, with no significant difference in complication rates (postoperative infection, lateral hinge fractures, and persistent pain).

Evaluation of low-crystallinity apatite as a novel synthetic bone graft material: In vivo and in vitro analysis

OBJECTIVES

To overcome the shortcomings of sintered bone graft materials, low-crystallinity apatite (LCA) was developed using a non-heated approach to enhance resorption and integration during bone regeneration. This study aimed to evaluate the efficacy of LCA as a synthetic bone graft material for bone reconstruction.

METHODS

LCA was compared to three conventional synthetic bone graft materials: biphasic calcium phosphate (BCP) 37, BCP 64, and octacalcium phosphate (OCP). Crystalline structure and surface morphology were examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). In vivo testing was conducted using a rabbit calvarial augmentation model, in which the grafts were placed into standardized defects. Bone formation and graft resorption were analyzed using micro-computed tomography (micro-CT) and histomorphometric analyses at three and six weeks post-implantation.

RESULTS

LCA exhibited structural similarities to the allograft material and enhanced surface properties. Micro-CT and histomorphometric evaluations at three and six weeks post-implantation demonstrated higher rates of bone formation and substantial volumetric changes with LCA, indicating efficient graft resorption and bone regeneration.

CONCLUSIONS

LCA exhibited superior integration, osteoconductivity, and biodegradability compared to other synthetic grafts, suggesting the potential for improved clinical outcomes with its use. Although the efficacy of LCA has been validated, further studies in diverse biological environments are necessary to confirm its safety and effectiveness for broader clinical use.

CLINICAL SIGNIFICANCE

LCA, which mimics natural bone structure and has superior integration and osteoconductivity, has the potential for clinical applications requiring rapid and effective bone healing.

In Situ Preparation of Composite Scaffolds Based on Polyurethane and Hydroxyapatite Particles for Bone Tissue Engineering

This article details the in situ preparation of composite scaffolds using polyurethane (PU) and HAp (hydroxyapatite), focusing on the unique properties of buriti oil (Mauritia flexuosa L.) applicable to tissue engineering. PU derived from vegetable oils, particularly buriti oil, has shown promise in bone tissue repair due to its rich bioactive compounds. Buriti oil is an excellent candidate for manufacturing these materials as it is an oil rich in bioactive compounds such as carotenoids, tocopherols, and fatty acids, which have antioxidant and anti-inflammatory properties. Furthermore, buriti oil has oleic acid as its principal fatty acid, which has been investigated as an excellent HAp dispersant. This research aimed to synthesize PU scaffolds from a polyol derived from buriti oil and incorporate HAp in different concentrations into the polymeric matrix through in situ polymerization. The chemical composition of the materials obtained, the distribution of hydroxyapatite particles in the polyurethane matrix, and the thermal stability were evaluated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), and thermogravimetry (TGA). In addition, to investigate biocompatibility, MTT tests (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium) were conducted using rat bone-marrow-derived mesenchymal stem cells (BMMSC). Characterizations confirm the formation of PU and the presence of HAp in the polymeric matrix, and the materials did not show cytotoxicity.

2023 International Academy of Toxicologic Pathology (IATP) Satellite Symposium: "Medical Device Safety Assessment: Pathology and Toxicology Perspective"

Medical devices represent a complex category of medicinal products with varying definitions depending on the regional jurisdiction of regulatory agencies. A common aspect of these definitions is that a medical device is intended to be used for specific medicinal purpose where the primary intended action of the device is not achieved through pharmacologic (or other chemical) means. While regional regulatory frameworks for medical devices are different than for pharmaceutical or biological products, medical device manufacturers are required to evaluate the safety and performance of these products in the context of their intended use. In biological safety evaluation, histopathology plays a relevant role in assessing medical device biocompatibility. This manuscript provides a broad overview of biocompatibility assessment with a deeper look at the role of the toxicologic pathologist in assessing innovative and emerging bone therapies. The content of this manuscript is based on individual presentations delivered at the 2023 International Academy of Toxicologic Pathology (IATP) Satellite Symposium held in conjunction with the Annual Congress of the European Society of Toxicologic Pathology (ESTP) on 26 September, in Basel, Switzerland.

Evaluation and optimization of physical, mechanical, and biological characteristics of 3D printed Whitlockite/calcium silicate composite scaffold for bone tissue regeneration using response surface methodology

Calcium phosphate-based bioscaffolds are used for bone tissue regeneration because of their physical and chemical resemblance to human bone. Calcium, phosphate, sodium, potassium, magnesium, and silicon are important components of human bone. The successful biomimicking of human bone characteristics involves incorporating all the human bone elements into the scaffold material. In this work, Mg-Whitlockite (WH) and Calcium Silicate (CS) were selected as matrix and reinforcement respectively, because of their desirable elemental composition and regenerative properties. The magnesium in WH increases mineralization in bone, and the silicon ions in CS support vascularization. The Mg-WH was synthesized using the wet chemical method, and powder characterization tests were performed. Response surface methodology (RSM) is used to design the experiments with a combination of material compositions, infill ratios (IFs), and sintering temperatures (STs). The WH/CS bioceramic composite is 3D printed in three different compositions: 100/0, 75/25, and 50/50 wt%, with IFs of 50%, 75%, and 100%. The physical and mechanical characterization study of printed samples is conducted and the result is optimized using RSM. ANOVA (Analysis of Variance) is used to establish the relationship between input parameters and responses. The optimized input parameters were the WH/CS composition of 50/50 wt%, IF of 50%, and ST of 1150 °C, which bring out the best possible combination of physical and mechanical characteristics. The RSM optimized response was a density of 2.27 g cm-3, porosity of 36.74%, wettability of 45.79%, shrinkage of 25.13%, compressive strength of 12 MPa, and compressive modulus of 208.49 MPa with 92% desirability. The biological characterization studies were conducted for the scaffold samples prepared with optimized input parameters. The biological studies confirmed the capabilities of the WH/CS composite scaffolds in bone regenerative applications.

Biological, Biomechanical, and Histopathological Evaluation of Polyetherketoneketone Bioactive Composite as Implant Material

While polyetherketoneketone is a high-performance thermoplastic polymer, its hydrophobicity and inertness limit bone adhesion. This study aimed to evaluate a novel PEKK/CaSiO3/TeO2 nanocomposite, comparing it to PEKK/15 wt.% CaSiO3 and PEKK groups. The in vitro study, involving 90 discs (n = 30), assessed the cytotoxicity of all groups after 24, 72, and 168 h. The in vivo animal study, using cylinder-type implants (n = 30), evaluated osseointegration through biomechanical push-out tests, descriptive histopathological examinations of decalcified sections stained with hematoxylin and eosin, and histomorphometric analysis of new bone formation area after 2- and 6-week healing intervals. The cytocompatibility of PEKK/15 wt.% CaSiO3/1 wt.% TeO2 composite confirmed its acceptance as a biomedical material. Additionally, in vivo study results showed that the PEKK/15 wt.% CaSiO3/1 wt.% TeO2 had the highest shear strength value and the highest new bone formation area compared to other experimental groups. The multimodal concept of adding CaSiO3 micro fillers and TeO2 nanofillers to PEKK produces a cytocompatible composite that enhances osseointegration and new bone formation in a rabbit's femur after 2- and 6-week healing intervals.

Matrix vesicle-inspired delivery system based on nanofibrous chitosan microspheres for enhanced bone regeneration

Inspired by the initial mineralization process with bone matrix vesicles (MVs), this study innovatively developed a delivery system to mediate mineralization during bone regeneration. The system comprises nanofibrous chitosan microspheres (NCM) and poly (allylamine hydrochloride)-stabilized amorphous calcium phosphate (PAH-ACP), which is thereafter referred to as NCMP. NCM is synthesized through the thermal induction of chitosan molecular chains, serving as the carrier, while PAH-ACP functions as the mineralization precursor. Additionally, the nanofibrous network of NCMP mimics the architecture of natural extracellular matrix (ECM), creating an optimal niche for the active adhesion of stem cells to its surface, exhibiting good biocompatibility, immunoregulation, and osteogenic performance. In vivo, NCMP effectively recruits cells and mineralizes collagen, modulates cell behavior and differentiation, and promotes in situ biomineralization in rat calvarial defects. These results underscore the dual efficacy of NCMP not only as an effective delivery system for mineralization precursors but also as ECM-mimicking bio-blocks, offering a promising avenue for enhancing the repair and regeneration of bone defects.

Enhancement of Bone Tissue Regeneration with Multi-Functional Nanoparticles by Coordination of Immune, Osteogenic, and Angiogenic Responses

Inorganic nanoparticles are promising materials for bone tissue engineering due to their chemical resemblance to the native bone structure. However, most studies are unable to capture the entirety of the defective environment, providing limited bone regenerative abilities. Hence, this study aims to develop a multifunctional nanoparticle to collectively control the defective bone niche, including immune, angiogenic, and osteogenic systems. The nanoparticles, self-assembled by biomimetic mineralization and tannic acid (TA)-mediated metal-polyphenol network (MPN), are released sustainably after the incorporation within a gelatin cryogel. The released nanoparticles display a reduction in M1 macrophages by means of reactive oxygen species (ROS) elimination. Consequently, osteoclast maturation is also reduced, which is observed by the minimal formation of multinucleated cells (0.4%). Furthermore, the proportion of M2 macrophages, osteogenic differentiation, and angiogenic potential are consistently increased by the effects of magnesium from the nanoparticles. This orchestrated control of multiple systems influences the in vivo vascularized bone regeneration in which 80% of the critical-sized bone defect is regenerated with new bones with mature lamellar structure and arteriole-scale micro-vessels. Altogether, this study emphasizes the importance of the coordinated modulation of immune, osteogenic, and angiogenic systems at the bone defect site for robust bone regeneration.

Masquelet technique combined with concentrated growth factors for the reconstruction of rabbit mandibular marginal bone defect

OBJECTIVE

Both the Masquelet technique (MT) and concentrated growth factors (CGF) reduce early graft loss and improve bone regeneration. This study aims to explore the efficacy of combining MT with CGF for mandibular defect repair by characterizing the induced membrane and assessing in vivo osteogenesis.

MATERIALS AND METHODS

Three experimental groups were compared: negative control (NC), MT, and Masquelet combined with CGF (MTC). Four weeks after the first surgery, histopathology is used to identify the morphological structure of the induced membrane, evaluate the degree of vascularization, and the secretion levels of osteogenesis and angiogenesis-related growth factors. In vivo osteogenesis was assessed with a second autologous bone graft surgery 4 weeks later, and bone reconstruction was evaluated by micro-CT and histopathology.

RESULTS

CGF significantly increased the induced membrane thickness, vascularization, and growth factor secretion levels. Quantitative micro-CT analysis showed that the bone volume fraction (BV/TV) at 4 weeks post-surgery was higher in the MTC group (23.30 ± 1.15%) compared to the MT group (16.50 ± 1.29%) and NC group (12.62 ± 1.23%) (P < 0.05). By 12 weeks, the difference in BV/TV between MTC (32.59 ± 0.11%) and MT (29.89 ± 0.49%) reduced, indicating consistent bone regeneration. Trabecular parameters were consistently higher in the MTC group, highlighting enhanced osteogenesis.

CONCLUSION

Combining the Masquelet technique with CGF effectively reduces early bone graft absorption and promotes bone repair. These findings suggest potential benefits for oral and maxillofacial bone defect treatment, though further studies are needed to confirm long-term efficacy.

CLINICAL RELEVANCE

Integrating Masquelet technique and CGF in mandibular reconstruction may improve clinical outcomes by enhancing bone regeneration and reducing graft failure.

Hierarchy Reproduction: Multiphasic Strategies for Tendon/Ligament-Bone Junction Repair

Tendon/ligament-bone junctions (T/LBJs) are susceptible to damage during exercise, resulting in anterior cruciate ligament rupture or rotator cuff tear; however, their intricate hierarchical structure hinders self-regeneration. Multiphasic strategies have been explored to fuel heterogeneous tissue regeneration and integration. This review summarizes current multiphasic approaches for rejuvenating functional gradients in T/LBJ healing. Synthetic, natural, and organism-derived materials are available for in vivo validation. Both discrete and gradient layouts serve as sources of inspiration for organizing specific cues, based on the theories of biomaterial topology, biochemistry, mechanobiology, and in situ delivery therapy, which form interconnected network within the design. Novel engineering can be constructed by electrospinning, 3-dimensional printing, bioprinting, textiling, and other techniques. Despite these efforts being limited at present stage, multiphasic scaffolds show great potential for precise reproduction of native T/LBJs and offer promising solutions for clinical dilemmas.

Bioinspired artificial antioxidases for efficient redox homeostasis and maxillofacial bone regeneration

Reconstructing large, inflammatory maxillofacial defects using stem cell-based therapy faces challenges from adverse microenvironments, including high levels of reactive oxygen species (ROS), inadequate oxygen, and intensive inflammation. Here, inspired by the reaction mechanisms of intracellular antioxidant defense systems, we propose the de novo design of an artificial antioxidase using Ru-doped layered double hydroxide (Ru-hydroxide) for efficient redox homeostasis and maxillofacial bone regeneration. Our studies demonstrate that Ru-hydroxide consists hydroxyls-synergistic monoatomic Ru centers, which efficiently react with oxygen species and collaborate with hydroxyls for rapid proton and electron transfer, thus exhibiting efficient, broad-spectrum, and robust ROS scavenging performance. Moreover, Ru-hydroxide can effectively sustain stem cell viability and osteogenic differentiation in elevated ROS environments, modulating the inflammatory microenvironment during bone tissue regeneration in male mice. We believe this Ru-hydroxide development offers a promising avenue for designing antioxidase-like materials to treat various inflammation-associated disorders, including arthritis, diabetic wounds, enteritis, and bone fractures.

Incorporation of metal-doped silicate microparticles into collagen scaffolds combines chemical and architectural cues for endochondral bone healing

Regeneration of large bone defects remains a clinical challenge until today. While existing biomaterials are predominantly addressing bone healing via direct, intramembranous ossification (IO), bone tissue formation via a cartilage phase, so-called endochondral ossification (EO) has been shown to be a promising alternative strategy. However, pure biomaterial approaches for EO induction are sparse and the knowledge how material components can have bioactive contribution to the required cartilage formation is limited. Here, we combined a previously developed purely architecture-driven biomaterial approach with the release of therapeutic metal ions from tailored silicate microparticles. The delivery platform was free of calcium phosphates (CaP) that are known to support IO but not EO and was employed for the release of lithium (Li), magnesium (Mg), strontium (Sr) or zinc (Zn) ions. We identified an ion-specific cellular response in which certain metal ions strongly enhanced cell recruitment into the material and showed superior chondrogenesis and deposition collagen II by human mesenchymal stromal cells (MSCs). At the same time, in some cases microparticle incorporation altered the mechanical properties of the biomaterial with consequences for cell-induced biomaterial contraction and scaffold wall deformation. Collectively, the results suggest that the incorporation of metal-doped silicate microparticles has the potential to further improve the bioactivity of architectured biomaterials for bone defect healing via EO. STATEMENT OF SIGNIFICANCE: Endochondral bone healing, a process that resembles embryonic skeletal development, has gained prominence in regenerative medicine. However, most therapeutic biomaterial strategies are not optimized for endochondral bone healing but instead target direct bone formation through IO. Here, we report on a novel approach to accelerate biomaterial-guided endochondral bone healing by combining cell-guiding collagen scaffolds with therapeutic metal-doped silicate microparticles. While other strategies, such as hypoxia-mimic drugs and iron-chelating biomaterials, have been documented in the literature before to enhance EO, our approach uniquely implements enhanced bioactivity into a previously developed biomaterial strategy for bone defect regeneration. Enhanced cell recruitment into the material and more pronounced chondrogenesis were observed for specific hybrid scaffold formulations, suggesting a high relevance of this new biomaterial for improved endochondral bone healing.

Efficacy of a gelatin-based hemostatic sponge and hydroxyapatite-chitosan nanocomposites (nHAp/CS) on regeneration of radial bone defects in rabbits

Background

Bone-graft substitutes are a frequently employed method for the clinical reconstruction of osseous bone defects, and research on synthetic biomaterials is currently ongoing. Absorbable hemostatic gelatin sponge and hydroxyapatite-chitosan nanocomposites (nHAp/CS) have gained popularity in recent years because of their inherent characteristics: osteogenesis, osteoconductivity, osteoinductivity, biodegradability, and biocompatibility.

Aim

The aim of the study was to evaluate the effectiveness of 1) a gelatin-based hemostatic sponge (Surgispon) and 2) a combination of a weight ratio of 75/25 nHAp/CS composite with a Surgispon for osteogenic potential in the treatment of full-thickness segmental osseous defects in the radius of rabbits.

Methods

The 18 New Zealand rabbits had 10-mm-induced segmental diaphyseal defects of the left limb radius and were randomly allocated into three groups: group I left the defects untreated (control group), group II used a Surgispon, and group III had a weight ratio of 75/25 nHAp/CS composite wrapped with a Surgispon. Quantitative evaluation of the bone repair at the defect site in each group (n = 6), radiographic, gross, computed tomography (CT), and histopathological examinations were performed at 6 weeks (n = 3) and 12 weeks (n = 3) postoperatively.

Results

The quantitative statistical analysis of various evaluation methods at 6 weeks post-implantation demonstrated that there was no statistically significant difference between the groups (p > 0.05). The statistically significant differences (p < 0.05) between groups I and II, while groups I and III, were evident 12 weeks postoperatively.

Conclusion

The findings of the radiographic, macroscopic, CT, and histopathological analyses firmly demonstrate that the combination of a 75/25 weight ratio composite of nHAp/CS with Surgispon is more effective than Surgispon alone in its ability to significantly increase bone formation. This could provide a prospective option for treating segmental bone defects.

Bioabsorbable magnesium-based bulk metallic glass composite (BMGC) for improved medial opening wedge high tibial osteotomy in knee osteoarthritis

Background and objective

Osteoarthritis is a widespread and debilitating condition, particularly affecting the medial compartment of knee joint due to varus knee deformities. Medial opening wedge high tibial osteotomy (MOWHTO) has emerged as an effective treatment, but it comes with challenges like fractures, correction loss, and nonunion, leading to unsatisfactory results in up to 26 % of patients. In response, our study explores the potential of a bioabsorbable magnesium-based bulk metallic glass composite (Mg67Zn28Ca5 BMGC) enriched with molybdenum particles as an innovative solution for MOWHTO.

Methods

Our comprehensive study includes composite fabrication, mechanical property evaluations, in vitro degradation tests, cell viability assessments, cell migration assays, calcium deposition analyses, and osteoblast differentiation investigations. In vivo experiments were commenced for assessing biological effects and bone growth of the Mg67Zn28Ca5 BMGC in an animal model. Finite element analysis was utilized for assessing the mechanical impact of the composite wedge in human MOWHTO.

Results

The findings indicate that the Mg67Zn28Ca5 BMGC closely matches human cortical bone's mechanical properties, with controlled degradation and superior cellular responses. In vivo experiments reveal progressive degradation and bone integration. Finite element analysis confirms the composite's mechanical effectiveness in MOWHTO.

Conclusion

In conclusion, our research introduces an innovative Mg67Zn28Ca5 BMGC enriched with molybdenum particles, showing promising mechanical and degradation characteristics. It has the potential to improve MOWHTO surgeries by matching cortical bone properties, controlled degradation, and promoting beneficial ion release for bone health. Successful tissue integration suggests suitability for high tibial osteotomy surgeries, offering hope for better outcomes in knee osteoarthritis patients.

The translational potential of this article

This article focuses on meeting the advantages of a novel magnesium-based BMGC with the clinical unmet need of MOWHTO surgeries. If properly developed, the results of this article have significant potential of translation to other temporary orthopedic implants under load-bearing conditions.

Osteochondral Tissue Engineering: Scaffold Materials, Fabrication Techniques and Applications

Osteochondral damage, caused by trauma, tumors, or degenerative diseases, presents a major challenge due to the limited self-repair capacity of the tissue. Traditional treatments often result in significant trauma and unpredictable outcomes. Recent advances in bone/cartilage tissue engineering, particularly in scaffold materials and fabrication technologies, offer promising solutions for osteochondral regeneration. This review highlights the selection and design of scaffolds using natural and synthetic materials such as collagen, chitosan (Cs), and polylactic acid (PLA), alongside inorganic components like bioactive glass and nano-hydroxyapatite (nHAp). Key fabrication techniques-freeze-drying, electrospinning, and 3D printing-have improved scaffold porosity and mechanical properties. Special focus is placed on the design of multiphasic scaffolds that mimic natural tissue structures, promoting cell adhesion and differentiation and supporting the regeneration of cartilage and subchondral bone. In addition, the current obstacles and future directions for regenerating damaged osteochondral tissues will be discussed.

Compositional Variations in Calcium Phosphate Cement and Poly(Lactic-Co-Glycolic-Acid) Porogens Do Not Affect the Orthotopic Performance of Calcium Phosphate Cement/Poly(Lactic-Co-Glycolic-Acid) Cements

Calcium phosphate cement (CPC) has evolved as an appealing bone substitute material, especially since CPCs were combined with poly(lactic-co-glycolic acid) (PLGA) porogens to render the resulting CPC/PLGA composite degradable. In view of the multiple variables of CPC and PLGA used previously, the effect of CPC composition and PLGA porogen morphology (i.e., microspheres versus microparticles) on the biological performance of CPC/PLGA has not yet been investigated. Consequently, we here aimed to evaluate comparatively various CPC/PLGA formulations varying in CPC composition and PLGA porogen morphology on their performance in a rabbit femoral condyle bone defect model. CPCs with a composition of 85 wt% α-TCP, 15 wt% dicalcium phosphate anhydrate (DCPA) and 5 wt% precipitated hydroxyapatite (pHA), or 100 wt% α-TCP were combined with spherical or irregularly shaped PLGA porogens (CPC/PLGA ratio of 60:40 wt% for all formulations). All CPC/PLGA formulations were applied via injection in bone defects, as created in the femoral condyle of rabbits, and retrieved for histological evaluation after 6 and 12 weeks of implantation. Descriptive histology and quantitative histomorphometry (i.e., material degradation and new bone formation) were used for analyses. Descriptively, all CPC/PLGA formulations showed material degradation at the periphery of the cement within 6 weeks of implantation. After 12 weeks, bone formation was observed extending into the defect core, replacing the degraded CPC/PLGA material. Quantitatively, similar material degradation (up to 87%) and new bone formation (up to 28%) values were observed, irrespective of compositional variations of CPC/PLGA formulations. These data prove that neither the CPC compositions nor the PLGA porogen morphologies as used in this work affect the biological performance of CPC/PLGA formulations in a rabbit femoral condyle bone defect model.

Bone Tissue Engineering With Chitosan, Carbon Nanotubes, and Hydroxyapatite Biomaterials Enriched With Mesenchymal Stem Cells: A Radiographic and Histological Evaluation in a Sheep Model Undergoing Ostectomy (Bone Tissue Engineering in a Sheep Model)

Comminuted fractures associated with tissue loss can adversely affect bone regeneration. Biomaterials enriched with mesenchymal stem cells (MSCs) employed for supporting osteosynthesis and potentiating osteoconduction are necessary to fill these bone defects. Natural compound biomaterials, similar to bone tissue, have been extensively tested in animal models for clinical use. Bone tissue engineering studies have used critical-size defects in ovine tibia monitored by imaging and histological examinations to evaluate the regenerative process. This study aimed to monitor the regenerative process in ovine tibial defects with or without chitosan, carbon nanotubes, or hydroxyapatite biomaterials, enriched or not enriched with MSCs. A 3-cm ostectomy was performed in 18 female Suffolk sheep. A 10-hole 4.5 mm narrow locking compression plate was used for osteosynthesis. The animals were randomly divided into three groups (n = 6): control (CON); defects filled with chitosan, carbon nanotubes, and hydroxyapatite biomaterial (BIO); and the same biomaterial enriched with bone marrow MSCs (BIO + CELL). The animals were evaluated monthly using radiographic examinations until 90 postoperative days, when they were euthanized. The limbs were subjected to micro-computed tomography (micro-CT), and bone specimens were subjected to histological evaluations. The radiographic examinations revealed construction stability without plate deviation, fracture, or bone lysis. Micro-CT evaluation demonstrated a difference in bone microarchitecture between the CON and biomaterial treatment groups (BIO and BIO + CELL). In the histological evaluations, the CON group did not demonstrate bone formation, and in the treatment groups (BIO and BIO + CELL), biocompatibility with sheep tissue was noted, and bone formation with trabeculae interspersed with remnants of the biomaterial was observed, with no differences between the groups. In conclusion, biomaterials present osteoconduction with beneficial characteristics for filling bone-lost fractures, and MSCs did not interfere with bone formation.

Efficacy of a gelatin-based hemostatic sponge and hydroxyapatite-chitosan nanocomposites (nHAp/CS) on regeneration of radial bone defects in rabbits

Background

Bone-graft substitutes are a frequently employed method for the clinical reconstruction of osseous bone defects, and research on synthetic biomaterials is currently ongoing. Absorbable hemostatic gelatin sponge and hydroxyapatite-chitosan nanocomposites (nHAp/CS) have gained popularity in recent years because of their inherent characteristics: osteogenesis, osteoconductivity, osteoinductivity, biodegradability, and biocompatibility.

Aim

The aim of the study was to evaluate the effectiveness of 1) a gelatin-based hemostatic sponge (Surgispon) and 2) a combination of a weight ratio of 75/25 nHAp/CS composite with a Surgispon for osteogenic potential in the treatment of full-thickness segmental osseous defects in the radius of rabbits.

Methods

The 18 New Zealand rabbits had 10-mm-induced segmental diaphyseal defects of the left limb radius and were randomly allocated into three groups: group I left the defects untreated (control group), group II used a Surgispon, and group III had a weight ratio of 75/25 nHAp/CS composite wrapped with a Surgispon. Quantitative evaluation of the bone repair at the defect site in each group (n = 6), radiographic, gross, computed tomography (CT), and histopathological examinations were performed at 6 weeks (n = 3) and 12 weeks (n = 3) postoperatively.

Results

The quantitative statistical analysis of various evaluation methods at 6 weeks post-implantation demonstrated that there was no statistically significant difference between the groups (p > 0.05). The statistically significant differences (p < 0.05) between groups I and II, while groups I and III, were evident 12 weeks postoperatively.

Conclusion

The findings of the radiographic, macroscopic, CT, and histopathological analyses firmly demonstrate that the combination of a 75/25 weight ratio composite of nHAp/CS with Surgispon is more effective than Surgispon alone in its ability to significantly increase bone formation. This could provide a prospective option for treating segmental bone defects.

Polydatin accelerates osteoporotic bone repair by inducing the osteogenesis-angiogenesis coupling of bone marrow mesenchymal stem cells via the PI3K/AKT/GSK-3β/β-catenin pathway

BACKGROUND

Polydatin (POL), a natural stilbenoid, has multiple pharmacological activities. However, its effect on osteoporotic bone defects has not yet been examined. This study was designed to explore the unknown role of POL on osteoporotic bone repair.

METHODS

The effect of POL on osteogenesis and angiogenesis were investigated firstly. Then a series of angiogenesis-related assays were carried out to explore the relationship between osteogenesis and angiogenesis of POL, and the underlying mechanism was further explored. Whereafter, ovariectomy-induced osteoporosis rats with bone defect were treated with POL or placebo, the imageological and histological examinations were conducted to assess the effect of POL on osteoporotic bone repair.

RESULTS

The moderate concentrations (1 μM and 10 μM) of POL enhanced the osteogenesis of bone marrow mesenchymal stem cells (BMSCs) and elevated the expression of angiogenic-specific markers. Further research found that POL-induced human umbilical vein endothelial cells migration and tube formation through the osteogenesis-angiogenesis coupling of BMSCs, and the POL-induced osteogenesis-angiogenesis coupling was reversed after co-cultured with LY294002. Mechanistically, this was conducted via activating PI3K/AKT/GSK-3β/β-catenin pathway. After that, using the osteoporotic bone defect rat model, the authors, observed that POL facilitated osteoporotic bone repair through enhancing osteogenesis and CD31 hi EMCN hi type H-positive vessels formation via the PI3K/AKT/GSK-3β/β-catenin pathway.

CONCLUSION

The data above indicated that POL could accelerate osteoporotic bone repair by inducing the osteogenesis-angiogenesis coupling of BMSCs via the PI3K/AKT/GSK-3β/β-catenin pathway, which provided new insight and strategy for osteoporotic bone repair.

Moldable self-setting and bioactive bone wax for bone hemostasis and defect repair

Objective

Bone injury complicated with bleeding and irregular shaped defect are challenging in orthopedic surgery and practices due to the lack of reliable hemostasis and simultaneous defect repair strategy. Bone wax is a century-old biomaterial for bleeding management in orthopedic surgery, characterized with ready-to-use advantage but the risk of failed bone reunion due to the biological inertness and non-degradability. In current work, integration of bioceramic cement and premixed concept was motivated to prepare a in situ self-setting bioactive calcium phosphate based bone wax (CaPBW) for bone hemostasis and defect repair.

Methods

A moldable, in situ self-setting bioactive CaPBW with a novel formulation of calcium phosphate cement (CPC), monetite (DPCA) granules, modified starch and polyethylene glycol (PEG) was developed for bone hemostasis and defect repair. The CaPBW material was evaluated by characterization, physical and chemical properties, biocompatibility, osteogenic ability and hemostatic ability.

Results

CaPBW adopted the ready-to-use feature of traditional bone wax, showing feasibility in shape molding and defect sealing. When interacted with physiological fluid like blood, CaPBW could transformed from putty to solid state within tens of minutes due to the gradual PEG-water exchange and CPC hydration, providing mechanical stability for bleeding clotting and bone defect filling. In vitro studies revealed the superiority of CaPBW over bone wax in blood coagulation and osteoblast differentiation, along with hemocompatibility and osteogenesis confirmation. In vivo studies demonstrated the reliability of CaPBW in hemostasis and bone regeneration compared to traditional bone wax, promoting the efficacy of bone bleeding and new bone formation.

Conclusion

As compared to traditional bone hemostatic agent bone wax, CaPBW not only preserved its advantages in handling and defect sealing, but also provided platform for temporary physical support and bone regeneration acceleration.

The translational potential of this article

The integrated design of osteogenesis and hemostasis makes CaPBW have the dual functions as bone hemostasis material and artificial bone substitute. CaPBW therefore demonstrates a strategy of next-generation bone wax with high translational potential for orthopedic surgery.

Advancements in reliability of mechanical performance of 3D PRINTED Ag-doped bioceramic antibacterial scaffolds for bone tissue engineering

The current gold-standard approach for addressing bone defects in load-bearing applications sees the use of either autographs or allographs. These solutions, however, have limitations as autographs and allographs carry the risk of additional trauma, the threat of disease transmission, and potential donor rejection. An attractive candidate for overcoming the challenges associated with the use of autographs and allographs is a 3D porous scaffold displaying the needed mechanical competency for use in load-bearing applications that can stimulate bone tissue regeneration and provide antibacterial capabilities. To date, no reports document a 3D porous scaffold that fully meets the criteria specified above. In this work, we show how the use of fused filament fabrication (FFF) 3D printing technology in combination with a bimodal distribution of Ag-doped bioactive glass-ceramic (Ag-BG) micro-sized particles can successfully deliver porous 3D scaffolds with attractive and reliable mechanical performance characteristics capable of stimulating bone tissue regeneration and the ability to provide inherent antibacterial properties. To characterize the reliability of the mechanical performance of the FFF-printed Ag-BG scaffolds, Weibull statistics were evaluated for both the compressive (N = 25; m = 13.6 ± 0.9) and flexural (N = 25; m = 7.3 ± 0.7) strengths. Methicillin-resistant Staphylococcus aureus (MRSA) was used both in planktonic and biofilm forms to highlight the advanced antibacterial characteristics of the FFF-printed Ag-BG scaffolds. Biological performance was evaluated in vitro through indirect exposure to human marrow stromal cells (hMSCs), where the FFF-printed Ag-BG scaffolds were found to provide an attractive environment for cell infiltration and mineralization. Our work demonstrates how fused filament fabrication technology can be used with bioactive and antibacterial materials such as Ag-BG to deliver mechanically competent porous 3D scaffolds capable of stimulating bone tissue regeneration while simultaneously providing antibacterial performance capabilities.

Citrate-modified bacterial cellulose as a potential scaffolding material for bone tissue regeneration

Bacterial cellulose (BC) is a novel biocompatible polymeric biomaterial with a wide range of biomedical uses, like tissue engineering (TE) scaffolds, wound dressings, and drug delivery. Although BC lacks good cell adhesion due to limited functionality, its tunable surface chemistry still holds promise. Here, hydroxyapatite (HA) was incorporated into a citrate-modified BC (MBC) using the biomimetic synthesis in simulated body fluid (SBF). Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermal gravimetric analysis (TGA), and compressive modulus were used to characterize the biomineralized MBC (BMBC) samples. Using 3-(4,5 dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl) -2H-tetrazolium (MTS), trypan blue dye exclusion (TBDE), and cell attachment assays on osteoblast cells, the developed BMBC have shown good cell viability, proliferation, and attachment after 3, 5, and 7 days of culture and therefore suggested as potential bone tissue regeneration scaffolding material.

Biomechanical study of two different fixation methods for the treatment of Neer III proximal humerus fractures

BACKGROUND

The lateral locking plate for the proximal humerus is currently the most commonly used surgical procedure for the treatment of elderly proximal humeral comminuted fractures. Previous studies have found that the rate of postoperative complications in patients of proximal humerus fractures with medial column involvement is relatively high. Through biomechanical methods, this study aims to investigate the effectiveness of the conventional lateral locking plate fixation along with the addition of the metacarpal supporting plate on the medial column in the treatment for proximal humeral fractures involving the medial column. The goal is to reduce the rate of postoperative internal fixation failure in patients with medial column injury.

METHODS

Thirty artificial synthetic humerus models are used as experimental samples. A proximal humerus fracture model with medial column injury was created, and then divided into two groups. Group A was fixed with a proximal humerus lateral locking plate (single-plate group). Group B was fixed with a proximal humerus lateral locking plate and a metacarpal supporting plate on the medial column (double-plate group). The failure displacement, stiffness, and strength of the repaired proximal humerus fractures with two different methods were tested under compression at posterior extension of 15°, forward flexion of 15°, and vertical direction.

RESULTS

There was no statistical significance in the comparison of the failure displacement of repaired proximal humeral fractures between the two groups under compression at posterior extension of 15° and forward flexion of 15° (P > 0.05). However, the failure displacement of the fracture was longer in single-plate group than in double-plate group under compression at vertical direction (P < 0.05). The double-plate group was better in terms of biomechanical stiffness and strength compared to the single-plate group at all three testing angles (P < 0.05).

CONCLUSIONS

For patients whose proximal humeral fractures involve the medial column, the addition of a support plate on the medial side of the humerus is recommended along with the lateral locking plate. The double-plate strategy can increase the stability of the medial column of the proximal humerus, and enhance the overall biomechanical property of the repaired proximal humerus.

Surgical treatment of spinal tuberculosis: an updated review

Tuberculosis (TB) is a worldwide disease which seriously affects the global public health. Spinal TB is the most common extra-pulmonary TB and may cause vertebral bone destruction, collapse, kyphosis and even paralysis. Anti-TB chemotherapy is considered the cornerstone treatment of spinal TB and surgery is often required for patients with severe kyphosis, impaired neurological function or spinal instability. Debridement of TB lesions, bone grafting and internal fixation are the key procedures of spinal TB surgery. However, the selection of surgical approach, the extent of TB lesion debridement, the choice of bone graft materials, and the method and extent of internal fixation are all remain controversy. The aim of this updated review is to evaluate current literature for advances in management of spinal TB, with particular focus on surgical techniques.

Biomimetic Natural Biomaterial Nanocomposite Scaffolds: A Rising Prospect for Bone Replacement

Biomimetic natural biomaterial (BNBM) nanocomposite scaffolds for bone replacement can reduce the rate of implant failure and the associated risks of post-surgical complications for patients. Traditional bone implants, like allografts, and autografts, have limitations, such as donor site morbidity and potential patient inflammation. Over two million bone transplant procedures are performed yearly, and success varies depending on the material used. This emphasizes the importance of developing new biomaterials for bone replacement. Innovative BNBM nanocomposites for modern bone fabrication can promote the colonization of the desired cellular components and provide the necessary mechanical properties. Recent studies have highlighted the advantages of BNBM nanocomposites for bone replacement; therefore, this review focuses on the application of cellulose, chitosan, alginates, collagen, hyaluronic acid, and synthetic polymers enhanced with nanoparticles for the fabrication of nanocomposite scaffolds used in bone regeneration and replacement. This work outlines the most up-to-date overview and perspectives of selected promising BNBM nanocomposites for bone replacement that could be used for scaffold fabrication and replace other biomorphic materials such as metallics, ceramics, and synthetic polymers in the future. In summary, the concluding remarks highlight the advantages and disadvantages of BNBM nanocomposites, prospects, and future directions for bone tissue regeneration and replacement.

Progress in the Application of Multifunctional Composite Hydrogels in Promoting Tissue Repair

Tissue repair is an extremely complex process, and effectively promoting tissue regeneration remains a significant clinical challenge. Hydrogel materials, which exhibit physical properties closely resembling those of living tissues, including high water content, oxygen permeability, and softness, have the potential to revolutionize the field of tissue repair. However, the presence of various complex conditions, such as infection, ischemia, and hypoxia in tissue defects, means that hydrogels with simple structures and functions are often insufficient to meet the diverse needs of tissue repair. Researchers have focused on integrating multiple drugs, nanomaterials, bioactive substances, and stem cells into hydrogel matrices to develop novel multifunctional composite hydrogels for addressing these challenges, which have superior antibacterial properties, hemostatic abilities, self-healing capacities, and excellent mechanical properties. These composite hydrogels are designed to enhance tissue repair and have become an important direction in the current research. This review provides a comprehensive review of the recent advances in the application of multifunctional composite hydrogels in promoting tissue repair, including drug-loaded hydrogels, nanomaterial composite hydrogels, bioactive substance composite hydrogels, and stem cell composite hydrogels.

Biological interaction of bioactive polymeric membranes in induced bone defects in rabbit tibias

The study aimed to evaluate bone repair using three osteoinductive polymers in bone defects created in rabbit tibias. Forty-eight adult rabbits were assessed at various time points: three, seven, fourteen, and thirty days. The groups included a control group (without biomaterial), M1 (Poly L Lactide co Polycaprolactone/Polyethylene Glycol), M2 (Poly L Lactide co Polycaprolactone/Polyethylene Glycol/β-Tricalcium Phosphate), and M3 (Poly L Lactide co Polycaprolactone/Polyethylene Glycol/nano hydroxyapatite). Histomorphometric analysis was conducted to evaluate new bone formation within and around the bone defect. At 14 (p<0.05) and 30 days (p<0.05), the callus area in the membrane groups, particularly in M3, was also significantly larger than in the control group, indicating the osteoinductive potential of these biomaterials. The callus consisted of both bone and cartilaginous matrix, suggesting a robust activation of endochondral ossification. The number of osteoclast was higher in the membrane groups, especially at 14 days in the M3 group, indicating increased bone remodeling activity. The membranes were not fully absorbed by 30 days, creating a space between the defect and the periosteum. In conclusion, all three membranes showed significant chondro and osteoinductive potential, with the membrane containing nano-hydroxyapatite demonstrating the most pronounced potential.

ECM-mimicking composite hydrogel for accelerated vascularized bone regeneration

Bioactive hydrogel materials have great potential for applications in bone tissue engineering. However, fabrication of functional hydrogels that mimic the natural bone extracellular matrix (ECM) remains a challenge, because they need to provide mechanical support and embody physiological cues for angiogenesis and osteogenesis. Inspired by the features of ECM, we constructed a dual-component composite hydrogel comprising interpenetrating polymer networks of gelatin methacryloyl (GelMA) and deoxyribonucleic acid (DNA). Within the composite hydrogel, the GelMA network serves as the backbone for mechanical and biological stability, whereas the DNA network realizes dynamic capabilities (e.g., stress relaxation), thereby promoting cell proliferation and osteogenic differentiation. Furthermore, functional aptamers (Apt19S and AptV) are readily attached to the DNA network to recruit bone marrow mesenchymal stem cells (BMSCs) and achieve sustained release of loaded vascular endothelial growth factor towards angiogenesis. Our results showed that the composite hydrogel could facilitate the adhesion of BMSCs, promote osteogenic differentiation by activating focal adhesion kinase (FAK)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/β-Catenin signaling pathway, and eventually enhance vascularized bone regeneration. This study shows that the multifunctional composite hydrogel of GelMA and DNA can successfully simulate the biological functions of natural bone ECM and has great potential for repairing bone defects.

An In Vivo Assessment of Different Mesenchymal Stromal Cell Tissue Types and Their Differentiation State on a Shape Memory Polymer Scaffold for Bone Regeneration

A combined biomaterial and cell-based solution to heal critical size bone defects in the craniomaxillofacial area is a promising alternative therapeutic option to improve upon autografting, the current gold standard. A shape memory polymer (SMP) scaffold, composed of biodegradable poly(ε-caprolactone) and coated with bioactive polydopamine, was evaluated with mesenchymal stromal cells (MSCs) derived from adipose (ADSC), bone marrow (BMSC), or umbilical cord (UCSC) tissue in their undifferentiated state or pre-differentiated toward osteoblasts for bone healing in a rat calvarial defect model. Pre-differentiating ADSCs and UCSCs resulted in higher new bone volume fraction (15.69% ± 1.64%) compared to empty (i.e., untreated) defects and scaffold-only (i.e., unseeded) groups (4.41% ± 1.11%). Notably, only differentiated UCSCs exhibited a significant increase in new bone volume, surpassing both undifferentiated UCSCs and unseeded scaffolds. Further, differentiated ADSCs and UCSCs had significantly higher trabecular numbers than their undifferentiated counterparts, unseeded scaffolds, and untreated defects. Although the mineral density regenerated within the unseeded scaffold surpassed that achieved with cell seeding, the connectivity of this bone was diminished, as the regenerated tissue confined itself to the spherical morphology of the scaffold pores. The SMP scaffold alone, with undifferentiated BMSCs, with undifferentiated and differentiated ADSCs, and differentiated UCSCs (29.72 ± 1.49 N) demonstrated significant osseointegration compared to empty defects (14.34 ± 2.21 N) after 12 weeks of healing when assessed by mechanical push-out testing. Based on these results and tissue availability to obtain the cells, pre-differentiated ADSCs and UCSCs emerge as particularly promising candidates when paired with the SMP scaffold for repairing critical size bone defects in the craniofacial skeleton.