A Multimaterial Scaffold With Tunable Properties: Toward Bone Tissue Repair

Decoding biomaterial-associated molecular patterns (BAMPs): influential players in bone graft-related foreign body reactions

Bone grafts frequently induce immune-mediated foreign body reactions (FBR), which hinder their clinical performance and result in failure. Understanding biomaterial-associated molecular patterns (BAMPs), including physicochemical properties of biomaterial, adsorbed serum proteins, and danger signals, is crucial for improving bone graft outcomes. Recent studies have investigated the role of BAMPs in the induction and maintenance of FBR, thereby advancing the understanding of FBR kinetics, triggers, stages, and key contributors. This review outlines the stages of FBR, the components of BAMPs, and their roles in immune activation. It also discusses various bone grafting biomaterials, their physicochemical properties influencing protein adsorption and macrophage modulation, and the key mechanisms of protein adsorption on biomaterial surfaces. Recent advancements in surface modifications and immunomodulatory strategies to mitigate FBR are also discussed. Furthermore, the authors look forward to future studies that will focus on a comprehensive proteomic analysis of adsorbed serum proteins, a crucial component of BAMPs, to identify proteins that promote or limit inflammation. This understanding could facilitate the design of biomaterials that selectively adsorb beneficial proteins, thereby reducing the risk of FBR and enhancing bone regeneration.

Organoids in Dynamic Culture: Microfluidics and 3D Printing Technologies

With the rapid advancement of biomaterials and tissue engineering technologies, organoid research and its applications have made significant strides. Organoids are increasingly utilized in pharmacology, regenerative medicine, and precision clinical medicine. Current trends in organoid research are moving toward multifunctional composite three-dimensional cultivation and dynamic cultivation strategies. Key technologies driving this evolution, including 3D printing and microfluidics, continue to impact new areas of discovery and clinical relevance. This review provides a systematic overview of these emerging trends, discussing the strengths and limitations of these critical technologies and offering insight and research directions for professionals working in the organoid field.

Facile one-step antibacterial biomineralized scaffolds through regulation of chitosan by imitating bone ingredient bonding to inspire endogenous repair

In situ mineralization based on chitosan (CS) as an organic template achieves uniform distribution of nano-hydroxyapatite (nHAp), and is expected to enhance interface bonding between materials and tissues, therefore promoting endogenous bone repair. However, chitosan-based materials are difficult to provide certain mechanical and antibacterial properties. In this study, Ca2+ and PO43- were used as the precursor of nHAP, Zn2+ as the precursor of nano-ZnO, and synthesized nHAp/ZnO particles in situ on the surface of chitosan to form CS/HAp/ZnO bone repair scaffold. The results indicated that the incorporated Zn2+ was chemically bonded to the system, with formed particles evenly distributed, which achieved more efficient antibacterial activity and osteogenic induction performance in vivo. The material had interconnected pore structure with a porosity of >70 %, which simulates the microenvironment of natural bone. The formed inorganic particles improved the mechanical properties of the chitosan scaffold to match the rate of new bone formation. ZnO endowed scaffolds with antibacterial activity, with antibacterial rate of >95 %. In addition, the material also showed good cell compatibility and biological activity, and promoted the adhesion, migration, proliferation and differentiation of osteoblast-related cells.

Copper doped bioactive glass promotes matrix vesicles-mediated biomineralization via osteoblast mitophagy and mitochondrial dynamics during bone regeneration

Bone defect repair remains a great challenge in the field of orthopedics. Human body essential trace element such as copper is essential for bone regeneration, but how to use it in bone defects and the underlying its mechanisms of promoting bone formation need to be further explored. In this study, by doping copper into mesoporous bioactive glass nanoparticles (Cu-MBGNs), we unveil a previously unidentified role of copper in facilitating osteoblast mitophagy and mitochondrial dynamics, which enhance amorphous calcium phosphate (ACP) release and subsequent biomineralization, ultimately accelerating the process of bone regeneration. Specifically, by constructing conditional knockout mice lacking the autophagy gene Atg5 in osteogenic lineage cells, we first confirmed the role of Cu-MBGNs-promoted bone formation via mediating osteoblast autophagy pathway. Then, the in vitro studies revealed that Cu-MBGNs strengthened mitophagy by inducing ROS production and recruiting PINK1/Parkin, thereby facilitating the efficient release of ACP from mitochondria into matrix vesicles for biomineralization during bone regeneration. Moreover, we found that Cu-MBGNs promoted mitochondrion fission via activating dynamin related protein 1 (Drp1) to reinforce mitophagy pathway. Together, this study highlights the potential of Cu-MBGNs-mediated mitophagy and biomineralization for augmenting bone regeneration, offering a promising avenue for the development of advanced bioactive materials in orthopedic applications.

Piezoelectricity Promotes 3D-Printed BTO/β-TCP Composite Scaffolds with Excellent Osteogenic Performance

Piezoelectricity is reported to be able to promote bone scaffolds with excellent osteogenic performance. Herein, barium titanate/β-tricalcium phosphate (BTO/β-TCP) piezoelectric composite scaffolds were 3D printed, and their osteogenic performances were investigated in detail. The fabrication of BTO/β-TCP piezoelectric composite scaffolds employed cutting-edge DLP 3D printing technology. The scaffolds, featuring a triply periodic minimal surface (TPMS) design with a porosity of 60%, offered a unique structural framework. A comprehensive assessment of the composition, piezoelectric properties, and mechanical characteristics of the BTO/β-TCP scaffolds was conducted. Notably, an increase in the BTO volume fraction from 50 to 80 vol % within the scaffolds led to a reduction in compressive strength, decreasing from 2.47 to 1.74 MPa. However, this variation was accompanied by a substantial enhancement in the piezoelectric constant d33, soaring from 1.4 pC/N to 21.6 pC/N. Utilizing mouse osteoblasts (MC3T3-E1) in a live/dead cell staining assay, under the influence of external ultrasound, demonstrated the commendable biocompatibility of these piezoelectric composite ceramic bone scaffolds. Furthermore, thorough analyses of alkaline phosphatase (ALP) activity and polymerase chain reaction (PCR) findings provided compelling evidence of the scaffolds' superior osteogenic properties, underpinning their effectiveness at the cellular protein and gene levels. In conclusion, this study offers a groundbreaking strategy for the employment of BTO/β-TCP piezoelectric composite scaffolds in bone implant applications, harnessing their unique blend of biocompatibility, piezoelectricity, and osteogenic potential.

Customized 3D-printed Poly ether ether ketone cranial implant for cranioplasty of skull defects

Cranioplasty become one of the common surgeries in the neurosurgical field. The complex configuration of the cranium makes the bone reconstruction of the skull defects a challenging procedure. While the patient's own bone flap is the best option, other materials such as titanium and Poly ether ether Ketone (PEEK) were used for cranioplasty when the autogenous flap of the patient is unavailable. Recently, customized 3D printing implants were developed for cranioplasty with favorable outcomes. In this study, we evaluated the outcome of customized 3-dimentional (3D)-printed PEEK implant cranioplasty for reconstructing skull defects, especially large ones. We report a series of 27 patients whose skull defects were reconstructed by a customized 3D-printed PEEK implants. Demographic data and postoperative clinical and imaging findings were reviewed. We analyzed the complications, clinical and aesthetic outcomes during mid-term follow-up. During the surgery, all the implants were perfectly fitted in the skull defect without any major modification. Aesthetic results were satisfactory in 74.1% of patients. 4 patients (14.8%) had complications, including 3 deep cranial infections (11.1%) and one extradural hematoma (3,7%). In 2 patients (7.4%), the implants were removed due to infection. Therefore, when autologous bone is unavailable or, in selected cases with large or complex skull defects, customized 3D-printed PEEK implants could be a proper option to reconstruct these defects.

Construction of a 3D Degradable PLLA/β-TCP/CS Scaffold for Establishing an Induced Membrane Inspired by the Modified Single-Stage Masquelet Technique

Although the Masquelet-induced membrane technique (MIMT) is now employed worldwide for bone defects, it often needs to be repeated and autogenous bone graft. This study aims to investigate the theoretical feasibility of replacing PMMA (poly(methyl methacrylate)) bone cement with PLLA (poly-l-lactic acid)/β -TCP (beta-tricalcium phosphate)/CS (calcium sulfate) scaffold for single-stage bone defect reconstruction, which evoke the induced membrane (IM) formation in the early stage and directly acts as the implantation in the second stage to reconstruct the bone defect. We constructed a corn-like PLLA/β -TCP/CS scaffold by the fused deposition 3D printing method. The characterizations of the scaffolds were investigated systematically. The P/T15/S15 scaffolds (the PLLA/β -TCP/CS scaffold with a 15% mass fraction of β-TCP and 15% mass fraction of CS) were filled into the large-segmental radius bone defects of white rabbits to evoke the formation of IMs. HE (hematoxylin-eosin) and VG (van gieson) staining, along with immunofluorescent staining, were performed to analyze the architecture and cellularity, the expression of BMP-2 (bone morphogenetic protein-2), VEGF (vascular endothelial growth factor), and TGF-β1 (transforming growth factor-β1) was evaluated by IHC (immunohistochemistry) and WB (western-blot) respectively, the ALP (alkaline phosphatase) and ARS (alizarin red S) staining was applied to assess the osteogenic potential. The corn-like PLLA/β-TCP/CS scaffolds with excellent physicochemical properties are successfully constructed using the fused deposition 3D printing technique. The HE and VG staining, along with immunofluorescent staining, suggested that the P/T15/S15 scaffold effectively mediated the formation of IM after 6 weeks of placement. A significant presence of M2 macrophages was observed in IM. The results of IHC and WB demonstrated that the IMs derived from the P/T15/S15 scaffolds exhibited elevated levels of VEGF, BMP-2, and TGF-β1, all of which promote the osteogenic differentiation of BMSCs. The results of cellular immunofluorescence, flow cytometry, and WB indicate that P/T15/S15 regulates the phenotypic polarization of M0 macrophages toward the M2 phenotype via the PI3K/AKT/β-Catenin pathway. These findings suggest that the biodegradable PLLA/β-TCP/CS scaffold may serve as a viable alternative to PMMA bone cement for single-stage bone defect reconstruction, owing to its unique ability to stimulate IM formation and promote the polarization of macrophages toward the M2 phenotype. This work presents innovative materials and strategies for the management of bone defects.

Immunomodulation in Bone Tissue Engineering: Recent Advancements in Scaffold Design and Biological Modifications for Enhanced Regeneration

Bone defects, whether caused by trauma, cancer, infectious diseases, or surgery, can significantly impair people's quality of life. Although autografts are the gold standard for treating bone defects, they often fall short in adequately forming bone tissue. The field of bone tissue engineering has made strides in using scaffolds with various biomaterials, stem cells, and growth factors to enhance bone healing. However, some biological structures do not yield satisfactory therapeutic outcomes for new bone formation. Recent studies have shed light on the crucial role of immunomodulation, specifically the interaction between the implanted scaffold and host immune systems, in bone regeneration. Immune cells, particularly macrophages, are pivotal in the inflammatory response, angiogenesis, and osteogenesis. This review delves into the immune system's mechanism toward foreign bodies and the recent advancements in scaffolds' physical and biological properties that foster bone regeneration by modulating macrophage polarization to an anti-inflammatory phenotype and enhancing the osteoimmune microenvironment.

Effects of structural design on the mechanical performances of poly-L-lactic acid cardiovascular scaffolds using FEA and in vitro methods

OBJECTIVE

In this study, we propose distinct and novel types of scaffold geometries to improve the mechanical performance of Poly-L-lactic Acid (PLLA) bioresorbable vascular scaffolds (BVS), investigating how different geometries of PLLA BVS influence their mechanical performances through finite element analysis (FEA) and in vitro experiment methods.

METHODS

Four different types of scaffold geometries were modelled for FEA and manufactured for in vitro experiments. PLLA tubes with 110 μm thickness were used in manufacturing the scaffolds. For FEA measurements, material properties and bilinear material models were obtained from tensile testing using the PLLA tubes employed for manufacturing. Various measurements were conducted including crush resistance, radial strength in both the laser-cut and deployed state, three-point bending, and scaffold crimping/expansion test.

RESULTS

Overall, the FEA results were similar to the experimental results. Design A, which had a conventional open-cell geometry with straight bridges, showed inferior crush resistance and radial strength to those of the other tested geometries. Design B exhibited the most well-balanced scaffold performances in terms of radial strengths, crush resistance, three-point bending, and crimping/expansion behaviors. Notably, it showed minimum plastic strain during crimping and expanding deformations in FEA.

CONCLUSIONS

Findings from such distinct and novel types of scaffold geometries shown by this study may provide a valuable understanding using PLLA scaffolds as cardiovascular devices.

Oriented Cortical-Bone-Like Silk Protein Lamellae Effectively Repair Large Segmental Bone Defects in Pigs

Assembling natural proteins into large, strong, bone-mimetic scaffolds for repairing bone defects in large-animal load-bearing sites remain elusive. Here this challenge is tackled by assembling pure silk fibroin (SF) into 3D scaffolds with cortical-bone-like lamellae, superior strength, and biodegradability through freeze-casting. The unique lamellae promote the attachment, migration, and proliferation of tissue-regenerative cells (e.g., mesenchymal stem cells [MSCs] and human umbilical vein endothelial cells) around them, and are capable of developing in vitro into cortical-bone organoids with a high number of MSC-derived osteoblasts. High-SF-content lamellar scaffolds, regardless of MSC inoculation, regenerated more bone than non-lamellar or low-SF-content lamellar scaffolds. They accelerated neovascularization by transforming macrophages from M1 to M2 phenotype, promoting bone regeneration to repair large segmental bone defects (LSBD) in minipigs within three months, even without growth factor supplements. The bone regeneration can be further enhanced by controlling the orientation of the lamella to be parallel to the long axis of bone during implantation. This work demonstrates the power of oriented lamellar bone-like protein scaffolds in repairing LSBD in large animal models.

3D-printed microstructured alginate scaffolds for neural tissue engineering

Alginate (Alg) is a versatile biopolymer for scaffold engineering and a bioink component widely used for direct cell printing. However, due to a lack of intrinsic cell-binding sites, Alg must be functionalized for cellular adhesion when used as a scaffold. Moreover, direct cell-laden ink 3D printing requires tedious disinfection procedures and cell viability is compromised by shear stress. Here, we demonstrate proof-of-concept, bioactive additive-free, microstructured Alg (M-Alg) scaffolds for neuron culture. The M-Alg scaffold was formed by introducing tetrapod-shaped ZnO (t-ZnO) microparticles into the ink as structural templates for interconnected channels and textured surfaces in the 3D-printed Alg scaffold, which were subsequently removed. Neurons exhibited significantly improved adhesion and growth on these M-Alg scaffolds compared with pristine Alg (P-Alg) scaffolds, with extensive neurite outgrowth and spontaneous neural activity, indicating the maturation of neuronal networks. These transparent, porous, additive-free Alg-based scaffolds with neuron affinity are promising for neuroregenerative and organoid-related research.

TPMS-Gyroid Scaffold-Mediated Up-Regulation of ITGB1 for Enhanced Cell Adhesion and Immune-Modulatory Osteogenesis

The porous structure is crucial in bone tissue engineering for promoting osseointegration. Among various structures, triply periodic minimal surfaces (TPMS) -Gyroid has been extensively studied due to its superior mechanical and biological properties. However, previous studies have given limited attention to the impact of unit cell size on the biological performance of scaffolds. In this research, four TPMS-Gyroid titanium scaffolds with different unit cell sizes (TG15, TG20, TG25, and TG30) are fabricated using Selective Laser Melting (SLM) to explore their effects on osseointegration. Mechanical tests revealed that TG15 and TG20 exhibited superior compressive strength. In vitro experiments demonstrated that TG20 facilitated better cell adhesion through robust integrin protein expression initially, which subsequently enhanced cell proliferation and osteogenic differentiation. Furthermore, macrophages on TG20 showed higher Integrin β1 (ITGB1) expression, promoting their polarization to the M2 phenotype, which suppressed inflammation, fostered bone integration, and angiogenesis. In vivo studies confirmed TG20's effectiveness in promoting bone ingrowth by reducing inflammation. This study highlights TG20's structural advantages, making it a promising bone scaffold with exceptional osteogenic and angiogenic properties through osteoimmune microenvironment modulation. Therefore, TG20 holds significant potential for applications in bone tissue engineering.

A comprehensive review on the State of the Art in the research and development of poly-ether-ether-ketone (PEEK) biomaterial-based implants

Polyetheretherketone (PEEK) is a preferred high-performance polymer in the spine, orthopedic, and craniomaxillofacial implant industry. However, despite its commendable mechanical properties, its bioinert nature limits the implants from integrating with neighboring tissues, impacting the implant's long-term performance. To address this limitation, various kinds of surface functionalization techniques have been developed over the years. Noteworthy efforts have been made to incorporate bioactive fillers in the PEEK matrix to develop standalone bioactive composites. In personalized medicine, significant advances have been made in the 3D Printing of PEEK implants. 3D-printed PEEK implants are now being developed at Point-of-Care, significantly reducing manufacturing and logistic time. Given the recent clinical follow-up updates and advancements in PEEK-based implants, PEEK implants are witnessing an important phase in its history. Recognizing this vital phase, this paper aims to comprehensively review the advancements of PEEK implants over the past decade. The review starts with an overview of the clinical impact of varying PEEK implants, followed by PEEK's surface functionalization techniques and engineering of PEEK-based bioactive composites. Next, this review describes the advancements made in the 3D printing of PEEK implants and points out the essential considerations that should be considered when developing 3D-printed PEEK-based implants. Finally, the review ends with an estimated projection about the future of PEEK-based implants. Readers are expected to gain an all-encompassing and in-depth understanding of PEEK biomedical implants' past, present, and future, enabling researchers to advance the research and development of PEEK-based implants in the required direction. STATEMENT OF SIGNIFICANCE: PEEK is a preferred high-performance polymer in the implant industry, with notable benefits over metallic and ceramic implants, such as bone-matching stiffness and durability. Significant strides have been made in the last decade to make PEEK implants bioactive and utilize 3D Printing to develop patient-specific implants. Given the recent advancements in PEEK-based implants, this review aims to provide an all-encompassing and in-depth understanding of PEEK biomedical implants' past, present, and future. It will comprehensively discuss the know-how gained from the clinical follow-up, the strategies to address the limitations of PEEK implants, and the essential considerations in 3D Printing of PEEK implants. This review will enable researchers to advance the research and development of PEEK implants in the required direction.

Composite superplastic aerogel scaffolds containing dopamine and bioactive glass-based fibers for skin and bone tissue regeneration

Multifunctional bioactive biomaterials with integrated bone and soft tissue regenerability hold great promise for the regeneration of trauma-affected skin and bone defects. The aim of this research was to fabricate aerogel scaffolds (GD-BF) by blending the appropriate proportions of short bioactive glass fiber (BGF), gelatin (Gel), and dopamine (DA). Electrospun polyvinyl pyrrolidone (PVP)-BGF fibers were converted into short BGF through calcination and homogenization. Microporous GD-BF scaffolds displayed good elastic deformation recovery and promoted neo-tissue formation. The DA could enable thermal crosslinking and enhance the mechanical properties and structural stability of the GD-BF scaffolds. The BGF-mediated release of therapeutic ions shorten hemostatic time (<30 s) in a rat tail amputation model and a rabbit artery injury model alongside inducing the regeneration of skin appendages (e.g., blood vessels, glands, etc.) in a full-thickness excisional defect model in rats (percentage wound closure: GD-BF2, 98 % vs. control group, 83 %) at day 14 in vitro. Taken together, these aerogel scaffolds may have significant promise for soft and hard tissue repair, which may also be worthy for the other related disciplines.

Tensile properties and deformation by different compatibilizers in bio-based polylactide/poly(4-hydroxybutyrate) blends

Blending chemically synthesized poly(4-hydroxybutyrate) (P4HB) with polylactide (PLLA) can overcome PLLA's brittleness, offering fully biobased blends. However, due to low compatibility between PLLA and P4HB, the influence of compatibilizers on the morphology, structure and tensile deformation of PLLA/P4HB blends remains to be unresolved. This article introduces reactive poly(methyl methacrylate-co-styrene-glycidyl methacrylate) (MSG) and non-reactive polyformaldehyde (POM) compatibilizers to improve the compatibility between P4HB and PLLA, achieving the maximal elongation at break exceeding 300 % at 2 wt% MSG or 3 wt% POM. MSG inhibits PLLA crystallization, extending stress stability in the silver streak stage, while POM enhances crystallization, prolonging the strain-hardening stage. Small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) analysis show that pristine PLLA forms voids before fracture, and PLLA/P4HB blends cavitate at the yield point and develop crazes in the silver streak stage. MSG effectively transmits stress and delays cavitation, extending the silver streak stage, whereas POM forms a microcrystalline network, lowering the energy barrier for stretching-induced recrystallization. These findings could provide theoretical guidelines on selecting compatibilizers for different PLLA based blends.

Laser powder bed fusion printed poly-ether-ether-ketone/bioactive glass composite scaffolds with dual-scale pores for enhanced osseointegration and bone ingrowth

Although poly-ether-ether-ketone (PEEK) implants hold significant medical promise, their bioinert nature presents challenges in osseointegration and bone ingrowth within clinical contexts. To mitigate these challenges, the present study introduces Diamond PEEK/bioactive glass (BG) composite scaffolds, characterized by macro/micro dual-porous structures, precisely fabricated via laser powder bed fusion (LPBF) technology. The findings indicate that an increase in BG content within these scaffolds significantly augments their hydrophilicity and hydroxyapatite formation capacities. Stress-strain curve analysis demonstrates reliable load-bearing stability across all scaffold types. In vitro assessments confirmed the non-cytotoxicity of PEEK/BG samples and demonstrated improved osteogenic differentiation and mineralization with increased BG incorporation. Further, in vivo experiments illustrated that the Diamond porous structure of these scaffolds facilitated bone growth, an effect notably amplified with higher BG content. Particularly in groups with 15 wt.% and 25 wt.% BG scaffolds, new bone formation was observed not only within the macropores of the Diamond structure but also within the micropores inside the scaffold rod, suggesting an almost seamless fusion with the new bone. This demonstrates the scaffolds' effective osteointegration and bone ingrowth properties. This study conclusively established the effectiveness of Diamond-structured PEEK/BG composite scaffolds, fabricated via LPBF, in bone repair. It highlights the crucial role of BG in enhancing osteogenic potential through interaction with the macro/micro pores of the scaffold. STATEMENT OF SIGNIFICANCE: This study addresses the bioinert nature of PEEK implants by developing Diamond-structured PEEK/bioactive glass (BG) composite scaffolds by laser powder bed fusion. The dual-porous macro/microstructure enhances hydrophilicity and hydroxyapatite formation, vital for bone regeneration. By adjusting the BG content, we controlled the melt viscosity and sintering rate, leading to the formation of beneficial microscale pores. These pores resolve the issue of ineffective bioactive fillers in previous LPBF-fabricated scaffolds, enhancing the osteogenic potential of BG and inducing superior bone ingrowth and osseointegration. In vitro and in vivo analyses show enhanced osteogenic differentiation, mineralization, and bone growth, underscoring the clinical potential of these scaffolds for bone repair.

Augmenting dermal collagen synthesis through hyaluronic acid-based microneedle-mediated delivery of poly(l-lactic acid) microspheres

Poly(L-lactic acid) (PLLA) can stimulate collagen synthesis through a foreign body response. However, inappropriate injection techniques and localized PLLA clustering can lead to complications and adverse events. This study developed a composite microneedle (MN) device comprising an array of PLLA microsphere (PLLA MP)-loaded hyaluronic acid needle tips with a supporting patch (PLLA MP-MN). This device was designed to deliver PLLA MPs precisely and uniformly to the dermis and to provide dual stimulation through MN puncture and MP implantation, thereby enabling the rapid and long-lasting regeneration of dermal collagen. When applied to rat skin, the MN array evenly distributed the PLLA MPs throughout the penetrated regions, which prevented local PLLA overdosing and elicited a milder inflammatory response compared with that induced by intradermal PLLA MP injections. An in vivo efficacy study revealed that MN-mediated delivery of PLLA MPs not only promptly initiated collagen production through microwound-triggered wound-healing cascades in the early treatment stage but also enabled the long-term stimulation of collagen deposition through MP-induced foreign body reactions, thereby significantly enhancing neocollagenesis. This innovative PLLA MP-MN system can augment the benefits and minimize the adverse effects associated with traditional PLLA fillers, providing a safe and reliable anti-aging therapeutic option.

Advanced Hybrid Strategies of GelMA Composite Hydrogels in Bone Defect Repair

To date, severe bone defects remain a significant challenge to the quality of life. All clinically used bone grafts have their limitations. Bone tissue engineering offers the promise of novel bone graft substitutes. Various biomaterial scaffolds are fabricated by mimicking the natural bone structure, mechanical properties, and biological properties. Among them, gelatin methacryloyl (GelMA), as a modified natural biomaterial, possesses a controllable chemical network, high cellular stability and viability, good biocompatibility and degradability, and holds the prospect of a wide range of applications. However, because they are hindered by their mechanical properties, degradation rate, and lack of osteogenic activity, GelMA hydrogels need to be combined with other materials to improve the properties of the composites and endow them with the ability for osteogenesis, vascularization, and neurogenesis. In this paper, we systematically review and summarize the research progress of GelMA composite hydrogel scaffolds in the field of bone defect repair, and discuss ways to improve the properties, which will provide ideas for the design and application of bionic bone substitutes.

Tuning interfacial molecular asymmetry to engineer protective coatings with superior surface anchoring, antifouling and antibacterial properties

Multifunctional robust protective coatings that combine biocompatibility, antifouling and antimicrobial properties play an essential role in reducing host reactions and infection on invasive medical devices. However, developing these protective coatings generally faces a paradox: coating materials capable of achieving robust adhesion to substrates via spontaneous deposition inevitably initiate continuous biofoulant adsorption, while those employing strong hydration capability to resist biofoulant attachment have limited substrate binding ability and durability under wear. Herein, we designed a multifunctional terpolymer of poly(dopamine methyacrylamide-co-2-methacryloyloxyethyl phoasphorylcholine-co-2-(dimethylamino)-ethyl methacrylate) (P(DMA-co-MPC-co-DMAEMA)), which integrates desired yet traditionally incompatible functions (i.e., robust adhesion, antifouling, lubrication, and antimicrobial properties). Direct normal and lateral force measurements, dynamic adsorption tests, surface ion conductance mapping were applied to comprehensively investigate the nanomechanics of coating-biofloulant interactions. Catechol groups of DMA act as basal anchors for robust substrate deposition, while the highly hydrated zwitterion of MPC provides apical protection to resist biofouling and wear. Moreover, the antimicrobial property is conferred through the protonation of tertiary amine groups on DMAEMA, inhibiting infection under physiological conditions. This work provides an effective strategy for harmonizing demanded yet incompatible properties in one coating material, with significant implications for the development of multifunctional surfaces towards the advancement of invasive biomedical devices. STATEMENT OF SIGNIFICANCE: Multifunctional robust protective coatings have been widely utilized in invasive medical devices to mitigate host responses and infection. However, modified surface coatings often encounter a trade-off between robust adhesion to substrates and strong hydration capability for antifouling and antimicrobial properties. We propose a universal strategy for surface modification by dopamine-assisted co-deposition with a multifunctional terpolymer of P(DMA-co-MPC-co-DMAEMA) that simultaneously achieves robust adhesion, antifouling, and antimicrobial properties. Through elucidating the nanomechanics with fundamentally understanding the interactions between the coating and biomacromolecules, we highlight the role of DMA for substrate adhesion, MPC for biofouling resistance, and DMAEMA for antimicrobial activity. This approach presents a promising strategy for constructing multifunctional coatings on minimally invasive medical devices by tuning interfacial molecular asymmetricity to reconcile incompatible properties within one coating.

Europium-Containing Nanospheres for Treating Ovariectomy-Induced Osteoporosis: Targeted Bone Remodeling and Macrophage Polarization Modulation

Purpose

Osteoporosis, characterized by reduced bone mass and structural deterioration, poses a significant healthcare challenge. Traditional treatments, while effective in reducing fracture risks, are often limited by side effects. This study introduces a novel nanocomplex, europium (Eu) ions-doped superparamagnetic iron oxide (SPIO) nanocrystals encapsulated in poly(lactic-co-glycolic acid) (PLGA) nanospheres, abbreviated as SPIO:Eu@PLGA nanospheres, as a potential therapeutic agent for osteoporosis by modulating macrophage polarization, enhancing osteoblast differentiation and inhibiting osteoclastogenesis.

Methods

SPIO and SPIO:Eu nanocrystals were synthesized through pyrolysis and encapsulated in PLGA using an emulsification method. To evaluate the impact of SPIO:Eu@PLGA nanospheres on macrophage reprogramming and reactive oxygen species (ROS) production, flow cytometry analysis was conducted. Furthermore, an ovariectomized (OVX) rat model was employed to assess the therapeutic efficacy of SPIO:Eu@PLGA nanospheres in preventing the deterioration of osteoporosis.

Results

In vitro, SPIO:Eu@PLGA nanospheres significantly attenuated M1 macrophage activation induced by lipopolysaccharides, promoting a shift towards the M2 phenotype. This action is linked to the modulation of ROS and the NF-κB pathway. Unlike free Eu ions, which do not achieve similar results when not incorporated into the SPIO nanocrystals. SPIO:Eu@PLGA nanospheres enhanced osteoblast differentiation and matrix mineralization while inhibiting RANKL-induced osteoclastogenesis. In vivo studies demonstrated that SPIO:Eu@PLGA nanospheres effectively targeted trabecular bone surfaces in OVX rats under magnetic guidance, preserving their structure and repairing trabecular bone loss by modulating macrophage polarization, thus restoring bone remodeling homeostasis. The study underscores the critical role of Eu doping in boosting the anti-osteoporotic effects of SPIO:Eu@PLGA nanospheres, evident at both cellular and tissue levels in vitro and in vivo.

Conclusion

The inclusion of Eu into SPIO matrix suggests a novel approach for developing more effective osteoporosis treatments, particularly for conditions induced by OVX. This research provides essential insights into SPIO:Eu@PLGA nanospheres as an innovative osteoporosis treatment, addressing the limitations of conventional therapies through targeted delivery and macrophage polarization modulation.

Ionic-physical-chemical triple cross-linked all-biomass-based aerogel for thermal insulation applications

Aerogels, as a unique porous material, are expected to be used as insulation materials to solve the global environmental and energy crisis. Using chitosan, citric acid, pectin and phytic acid as raw materials, an all-biomass-based aerogel with high modulus was prepared by the triple strategy of ionic, physical and chemical cross-linking through directional freezing technique. Based on this three-dimensional network, the aerogel exhibited excellent compressive modulus (24.89 ± 1.76 MPa) over a wide temperature range and thermal insulation properties. In the presence of chitosan, citric acid and phytic acid, the aerogel obtained excellent fire safety (LOI value up to 31.2%) and antibacterial properties (antibacterial activity against Staphylococcus aureus and Escherichia coli reached 81.98% and 67.43%). In addition, the modified aerogel exhibited excellent hydrophobicity (hydrophobic angle of 146°) and oil-water separation properties. More importantly, the aerogel exhibited a biodegradation rate of up to 40.31% for 35 days due to its all-biomass nature. This work provides a green and sustainable strategy for the production of highly environmentally friendly thermal insulation materials with high strength, flame retardant, antibacterial and hydrophobic properties.

Preparation and properties of silver-carrying nano-titanium dioxide antimicrobial agents and silicone composite

The characteristics of dopamine self-polymerization were used to cover the nano-titanium dioxide (TiO2) surface and produce nano-titanium dioxide-polydopamine (TiO2-PDA). The reducing nature of dopamine was then used to reduce silver nitrate to silver elemental particles on the modified nano-titanium dioxide: The resulting TiO2-PDA-Ag nanoparticles were used as antimicrobial agents. Finally, the antibacterial agent was mixed with silicone to obtain an antibacterial silicone composite material. The composition and structure of antibacterial agents were analyzed by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron energy spectroscopy, and X-ray diffraction. Microscopy and the antibacterial properties of the silicone antibacterial composites were studied as well. The TiO2-PDA-Ag antimicrobial agent had good dispersion versus nano-TiO2. The three were strongly combined with obvious characteristic peaks. The antibacterial agents were evenly dispersed in silicone, and the silicone composite has excellent antibacterial properties. Bacillus subtilis (B. subtilis) adhesion was reduced from 246 × 104 cfu/cm2 to 2 × 104 cfu/cm2, and colibacillus (E. coli) reduced from 228 × 104 cfu/cm2 leading to bacteria-free adhesion.

Methacrylated Carboxymethyl Chitosan Scaffold Containing Icariin-Loaded Short Fibers for Antibacterial, Hemostasis, and Bone Regeneration

Bone defects typically result in bone nonunion, delayed or nonhealing, and localized dysfunction, and commonly used clinical treatments (i.e., autologous and allogeneic grafts) have limited results. The multifunctional bone tissue engineering scaffold provides a new treatment for the repair of bone defects. Herein, a three-dimensional porous composite scaffold with stable mechanical support, effective antibacterial and hemostasis properties, and the ability to promote the rapid repair of bone defects was synthesized using methacrylated carboxymethyl chitosan and icariin-loaded poly-l-lactide/gelatin short fibers (M-CMCS-SFs). Icariin-loaded SFs in the M-CMCS scaffold resulted in the sustained release of osteogenic agents, which was beneficial for mechanical reinforcement. Both the porous structure and the use of chitosan facilitate the effective absorption of blood and fluid exudates. Moreover, its superior antibacterial properties could prevent the occurrence of inflammation and infection. When cultured with bone mesenchymal stem cells, the composite scaffold showed a promotion in osteogenic differentiation. Taken together, such a multifunctional composite scaffold showed comprehensive performance in antibacterial, hemostasis, and bone regeneration, thus holding promising potential in the repair of bone defects and related medical treatments.

Therapeutic impacts of GNE‑477‑loaded H2O2 stimulus‑responsive dodecanoic acid‑phenylborate ester‑dextran polymeric micelles on osteosarcoma

Osteosarcoma (OS) is a highly malignant primary bone neoplasm that is the leading cause of cancer‑associated death in young people. GNE‑477 belongs to the second generation of mTOR inhibitors and possesses promising potential in the treatment of OS but dose tolerance and drug toxicity limit its development and utilization. The present study aimed to prepare a novel H2O2 stimulus‑responsive dodecanoic acid (DA)‑phenylborate ester‑dextran (DA‑B‑DEX) polymeric micelle delivery system for GNE‑477 and evaluate its efficacy. The polymer micelles were characterized by morphology, size and critical micelle concentration. The GNE‑477 loaded DA‑B‑DEX (GNE‑477@DBD) tumor‑targeting drug delivery system was established and the release of GNE‑477 was measured. The cellular uptake of GNE‑477@DBD by three OS cell lines (MG‑63, U2OS and 143B cells) was analyzed utilizing a fluorescent tracer technique. The hydroxylated DA‑B was successfully grafted onto dextran at a grafting rate of 3%, suitable for forming amphiphilic micelles. Following exposure to H2O2, the DA‑B‑DEX micelles ruptured and released the drug rapidly, leading to increased uptake of GNE‑477@DBD by cells with sustained release of GNE‑477. The in vitro experiments, including MTT assay, flow cytometry, western blotting and RT‑qPCR, demonstrated that GNE‑477@DBD inhibited tumor cell viability, arrested cell cycle in G1 phase, induced apoptosis and blocked the PI3K/Akt/mTOR cascade response. In vivo, through the observation of mice tumor growth and the results of H&E staining, the GNE‑477@DBD group exhibited more positive therapeutic outcomes than the free drug group with almost no adverse effects on other organs. In conclusion, H2O2‑responsive DA‑B‑DEX presents a promising delivery system for hydrophobic anti‑tumor drugs for OS therapy.

Acemannan coated, cobalt-doped biphasic calcium phosphate nanoparticles for immunomodulation regulated bone regeneration

Biomaterials are used as scaffolds in bone regeneration to facilitate the restoration of bone tissues. The local immune microenvironment affects bone repair but the role of immune response in biomaterial-facilitated osteogenesis has been largely overlooked and it presents a major knowledge gap in the field. Nanomaterials that can modulate M1 to M2 macrophage polarization and, thus, promote bone repair are known. This study investigates a novel approach to accelerate bone healing by using acemannan coated, cobalt-doped biphasic calcium phosphate nanoparticles to promote osteogenesis and modulate macrophage polarization to provide a prohealing microenvironment for bone regeneration. Different concentrations of cobalt were doped in biphasic calcium phosphate nanoparticles, which were further coated with acemannan polymer and characterized. The nanoparticles showed >90% cell viability and enhanced cell proliferation along with osteogenic differentiation as demonstrated by the enhanced alkaline phosphatase activity and osteogenic calcium deposition. The morphology of MC3T3-E1 cells remained unchanged even after treatment with nanoparticles. Acemannan coated nanoparticles were also able to decrease the expression of M1 markers, iNOS, and CD68 and enhance the expression of M2 markers, CD206, CD163, and Arg-1 as indicated by RT-qPCR, flow cytometry, and ICC studies. The findings show that acemannan coated nanoparticles can create a supportive immune milieu by inducing and promoting the release of osteogenic markers, and by causing a reduction in inflammatory markers, thus helping in efficient bone regeneration. As per our knowledge, this is the first study showing the combined effect of acemannan and cobalt for bone regeneration using immunomodulation. The work presents a novel approach for enhancing osteogenesis and macrophage polarization, thus, offering a potent strategy for effective bone regeneration.

ETV2 regulating PHD2-HIF-1α axis controls metabolism reprogramming promotes vascularized bone regeneration

The synchronized development of mineralized bone and blood vessels is a fundamental requirement for successful bone tissue regeneration. Adequate energy production forms the cornerstone supporting new bone formation. ETS variant 2 (ETV2) has been identified as a transcription factor that promotes energy metabolism reprogramming and facilitates the coordination between osteogenesis and angiogenesis. In vitro molecular experiments have demonstrated that ETV2 enhances osteogenic differentiation of dental pulp stem cells (DPSCs) by regulating the ETV2- prolyl hydroxylase 2 (PHD2)- hypoxia-inducible factor-1α (HIF-1α)- vascular endothelial growth factor A (VEGFA) axis. Notably, ETV2 achieves the rapid reprogramming of energy metabolism by simultaneously accelerating mitochondrial aerobic respiration and glycolysis, thus fulfilling the energy requirements essential to expedite osteogenic differentiation. Furthermore, decreased α-ketoglutarate release from ETV2-modified DPSCs contributes to microcirculation reconstruction. Additionally, we engineered hydroxyapatite/chitosan microspheres (HA/CS MS) with biomimetic nanostructures to facilitate multiple ETV2-DPSC functions and further enhanced the osteogenic differentiation. Animal experiments have validated the synergistic effect of ETV2-modified DPSCs and HA/CS MS in promoting the critical-size bone defect regeneration. In summary, this study offers a novel treatment approach for vascularized bone tissue regeneration that relies on energy metabolism activation and the maintenance of a stable local hypoxia signaling state.

Melt electrowritten poly-lactic acid /nanodiamond scaffolds towards wound-healing patches

Multifunctional wound dressings, enriched with biologically active agents for preventing or treating infections and promoting wound healing, along with cell delivery capability, are highly needed. To address this issue, composite scaffolds with potential in wound dressing applications were fabricated in this study. The poly-lactic acid/nanodiamonds (PLA/ND) scaffolds were first printed using melt electrowriting (MEW) and then coated with quaternized β-chitin (QβC). The NDs were well-dispersed in the printed filaments and worked as fillers and bioactive additions to PLA material. Additionally, they improved coating effectiveness due to the interaction between their negative charges (from NDs) and positive charges (from QβC). NDs not only increased the thermal stability of PLA but also benefitted cellular behavior and inhibited the growth of bacteria. Scaffolds coated with QβC increased the effect of bacteria growth inhibition and facilitated the proliferation of human dermal fibroblasts. Additionally, we have observed rapid extracellular matrix (ECM) remodeling on QβC-coated PLA/NDs scaffolds. The scaffolds provided support for cell adhesion and could serve as a valuable tool for delivering cells to chronic wound sites. The proposed PLA/ND scaffold coated with QβC holds great potential for achieving fast healing in various types of wounds.

Preparation and Characterization of Carboxymethyl Chitosan/Sodium Alginate Composite Hydrogel Scaffolds Carrying Chlorhexidine and Strontium-Doped Hydroxyapatite

Herein, we introduce a novel composite hydrogel scaffold designed for addressing infectious jaw defects, a significant challenge in clinical settings caused by the inherent limited self-regenerative capacity of bone tissues. The scaffold was engineered from a blend of carboxymethyl chitosan (CMCS)/sodium alginate (SA) hydrogel (CSH), β-cyclodextrin/chlorhexidine clathrate (β-CD-CHX), and strontium-nanohydroxyapatite nanoparticles (Sr-nHA). The β-CD-CHX and Sr-nHA components were synthesized using a saturated aqueous solution and a coprecipitation method, respectively. Subsequently, these elements were encapsulated within the CSH matrix. Comprehensive characterization of the CMCS/SA/β-CD-CHX/Sr-nHA composite hydrogel scaffold via scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy validated the successful synthesis. The swelling and in vitro degradation behaviors proved that the composite hydrogel had good physical properties, while in vitro evaluations demonstrated favorable biocompatibility and osteoinductive properties. Additionally, antibacterial assessments revealed its effectiveness against common pathogens, Staphylococcus aureus and Escherichia coli. Overall, our results indicate that the CMCS/SA/β-CD-CHX/Sr-nHA composite hydrogel scaffolds exhibit significant potential for effectively treating infection-prone jaw defects.

A comprehensive review on the biomedical frontiers of nanowire applications

This comprehensive review examines the immense capacity of nanowires, nanostructures characterized by unbounded dimensions, to profoundly transform the field of biomedicine. Nanowires, which are created by combining several materials using techniques such as electrospinning and vapor deposition, possess distinct mechanical, optical, and electrical properties. As a result, they are well-suited for use in nanoscale electronic devices, drug delivery systems, chemical sensors, and other applications. The utilization of techniques such as the vapor-liquid-solid (VLS) approach and template-assisted approaches enables the achievement of precision in synthesis. This precision allows for the customization of characteristics, which in turn enables the capability of intracellular sensing and accurate drug administration. Nanowires exhibit potential in biomedical imaging, neural interfacing, and tissue engineering, despite obstacles related to biocompatibility and scalable manufacturing. They possess multifunctional capabilities that have the potential to greatly influence the intersection of nanotechnology and healthcare. Surmounting present obstacles has the potential to unleash the complete capabilities of nanowires, leading to significant improvements in diagnostics, biosensing, regenerative medicine, and next-generation point-of-care medicines.

Temporal control in shell-core structured nanofilm for tracheal cartilage regeneration: synergistic optimization of anti-inflammation and chondrogenesis

Cartilage tissue engineering offers hope for tracheal cartilage defect repair. Establishing an anti-inflammatory microenvironment stands as a prerequisite for successful tracheal cartilage restoration, especially in immunocompetent animals. Hence, scaffolds inducing an anti-inflammatory response before chondrogenesis are crucial for effectively addressing tracheal cartilage defects. Herein, we develop a shell-core structured PLGA@ICA-GT@KGN nanofilm using poly(lactic-co-glycolic acid) (PLGA) and icariin (ICA, an anti-inflammatory drug) as the shell layer and gelatin (GT) and kartogenin (KGN, a chondrogenic factor) as the core via coaxial electrospinning technology. The resultant PLGA@ICA-GT@KGN nanofilm exhibited a characteristic fibrous structure and demonstrated high biocompatibility. Notably, it showcased sustained release characteristics, releasing ICA within the initial 0 to 15 days and gradually releasing KGN between 11 and 29 days. Subsequent in vitro analysis revealed the potent anti-inflammatory capabilities of the released ICA from the shell layer, while the KGN released from the core layer effectively induced chondrogenic differentiation of bone marrow stem cells (BMSCs). Following this, the synthesized PLGA@ICA-GT@KGN nanofilms were loaded with BMSCs and stacked layer by layer, adhering to a 'sandwich model' to form a composite sandwich construct. This construct was then utilized to repair circular tracheal defects in a rabbit model. The sequential release of ICA and KGN facilitated by the PLGA@ICA-GT@KGN nanofilm established an anti-inflammatory microenvironment before initiating chondrogenic induction, leading to effective tracheal cartilage restoration. This study underscores the significance of shell-core structured nanofilms in temporally regulating anti-inflammation and chondrogenesis. This approach offers a novel perspective for addressing tracheal cartilage defects, potentially revolutionizing their treatment methodologies.

Hierarchical porous PLLA/ACP fibrous membrane towards bone tissue scaffold

Electrospun fibres have emerged as vital components in developing tissue engineering scaffolds. Calcium phosphate-based materials, renowned for their bioactivity and biocompatibility, have garnered considerable attention in biomedical applications. This study focuses on the incorporation of amorphous calcium phosphate (ACP) nanoparticles into poly(L-lactic acid) (PLLA) to produce electrospun PLLA/ACP fibrous membranes. Subsequent treatment with acetone yielded a hierarchical porous structure, boasting an ultra-high surface area of 94.7753 ± 0.3884 m2/g. The ACP nanoparticles, initially encapsulated by PLLA, were exposed on the fibre surface after acetone treatment. Furthermore, the porous PLLA/ACP fibrous membrane exhibited superior mechanical properties (Young's modulus = 0.148 GPa, tensile strength = 3.05 MPa) and enhanced wettability. In a 7-day in vitro cell culture with human osteoblast-like cells, the porous PLLA/ACP fibrous membrane demonstrated a significant improvement in osteoblast adhesion and proliferation, with a proliferation rate increase of 252.0% and 298.7% at day 4 and day 7, respectively. These findings underscore the potential of the porous PLLA/ACP fibrous membrane as a promising candidate for bone tissue scaffolds.

Optimization by mixture design of chitosan/multi-phase calcium phosphate/BMP-2 biomimetic scaffolds for bone tissue engineering

The modulation of cell behavior during culture is one of the most important aspects of bone tissue engineering because of the necessity for a complex mechanical and biochemical environment. This study aimed to improve the physicochemical properties of chitosan/multi-phase calcium phosphate (MCaP) scaffolds using an optimized mixture design experiment and evaluate the effect of biofunctionalization of the obtained scaffolds with the bone morphogenetic protein BMP-2 on stem cell behavior. The present study evaluated the compressive strength, elastic modulus, porosity, pore diameter, and degradation in simulated body fluids and integrated these responses using desirability. The properties of the scaffolds with the best desirability (18.4% of MCaP) were: compressive strength of 23 kPa, elastic modulus of 430 kPa, pore diameter of 163 μm, porosity of 92%, and degradation of 20% after 21 days. Proliferation and differentiation experiments were conducted using dental pulp stem cells after grafting BMP-2 onto scaffolds via the carbodiimide route. These experiments showed that MCaP promoted cell proliferation and increased alkaline phosphatase activity, whereas BMP-2 enhanced cell differentiation. This study demonstrates that optimizing the composition of a mixture of chitosan and MCaP improves the physicochemical and biological properties of scaffolds, indicating that this solution is viable for application in bone tissue engineering.

An oxidized dextran-composite self-healing coated magnesium scaffold reduces apoptosis to induce bone regeneration

Self-healing coatings have shown promise in controlling the degradation of scaffolds and addressing coating detachment issues. However, developing a self-healing coating for magnesium (Mg) possessing multiple biological functions in infectious environments remains a significant challenge. In this study, a self-healing coating was developed for magnesium scaffolds using oxidized dextran (OD), 3-aminopropyltriethoxysilane (APTES), and nano-hydroxyapatite (nHA) doped micro-arc oxidation (MHA), named OD-MHA/Mg. The results demonstrated that the OD-MHA coating effectively addresses coating detachment issues and controls the degradation of Mg in an infectious environment through self-healing mechanisms. Furthermore, the OD-MHA/Mg scaffold exhibits antibacterial, antioxidant, and anti-apoptotic properties, it also promotes bone repair by upregulating the expression of osteogenesis genes and proteins. The findings of this study indicate that the OD-MHA coated Mg scaffold possessing multiple biological functions presents a promising approach for addressing infectious bone defects. Additionally, the study showcases the potential of polysaccharides with multiple biological functions in facilitating tissue healing even in challenging environments.

Neoteric Semiembedded β-Tricalcium Phosphate Promotes Osteogenic Differentiation of Mesenchymal Stem Cells under Cyclic Stretch

β-Tricalcium phosphate (β-TCP) is a bioactive material for bone regeneration, but its brittleness limits its use as a standalone scaffold. Therefore, continuous efforts are necessary to effectively integrate β-TCP into polymers, facilitating a sturdy ion exchange for cell regulation. Herein, a novel semiembedded technique was utilized to anchor β-TCP nanoparticles onto the surface of the elastic polymer, followed by hydrophilic modification with the polymerization of dopamine. Cell adhesion and osteogenic differentiation of mesenchymal stem cells (MSCs) under static and dynamic uniaxial cyclic stretching conditions were investigated. The results showed that the new strategy was effective in promoting cell adhesion, proliferation, and osteogenic induction by the sustained release of Ca2+ in the vicinity and creating a reasonable roughness. Specifically, released Ca2+ from β-TCP could activate the calcium signaling pathway, which further upregulated calmodulin and calcium/calmodulin-dependent protein kinase II genes in MSCs. Meanwhile, the roughness of the membrane and the uniaxial cyclic stretching activated the PIEZO1 signaling pathway. Chemical and mechanical stimulation promotes osteogenic differentiation and increases the expression of related genes 2-8-fold. These findings demonstrated that the neoteric semiembedded structure was a promising strategy in controlling both chemical and mechanical factors of biomaterials for cell regulation.

Degradation behaviour of porous poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) scaffolds in cell culture

Exploring the degradation behaviour of biomaterials in a complex in vitro physiological environment can assist in predicting their performance in vivo, yet this aspect remains largely unexplored. In this study, the in vitro degradation over 12 weeks of porous poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) bone scaffolds in human osteoblast (hOB) culture was investigated. The objective was to evaluate how the presence of cells influenced both the degradation behaviour and mechanical stability of these scaffolds. The molecular weight (Mw) of the scaffolds decreased with increasing incubation time and the Mw reduction rate (6.2 ± 0.4 kg mol-1 week-1) was similar to that observed when incubated in phosphate buffered saline (PBS) solution, implying that the scaffolds underwent hydrolytic degradation in hOB culture. The mass of the scaffolds increased by 0.8 ± 0.2 % in the first 4 weeks, attributed to cells attachment and extracellular matrix (ECM) deposition including biomineralisation. During the first 8 weeks, the nominal compressive modulus, E⁎, of the scaffolds remained constant. However, it increased significantly from Week 8 to 12, with increments of 55 % and 42 % in normal and lateral directions, respectively, attributed to the reinforcement effect of cells, ECM and minerals attached on the surface of the scaffold. This study has highlighted, that while the use of PBS in degradation studies is suitable for evaluating Mw changes it cannot predict changes in mechanical properties to PHBV scaffolds in the presence of cells and culture media. Furthermore, the PHBV scaffolds had mechanical stability in cell culture for 12 weeks validating their suitability for tissue engineering applications.

Polydopamine-Functionalized Strontium Alginate/Hydroxyapatite Composite Microhydrogel Loaded with Vascular Endothelial Growth Factor Promotes Bone Formation and Angiogenesis

Critical-size bone defects are a common and intractable clinical problem that typically requires filling in with surgical implants to facilitate bone regeneration. Considering the limitations of autologous bone and allogeneic bone in clinical applications, such as secondary damage or immunogenicity, injectable microhydrogels with osteogenic and angiogenic effects have received considerable attention. Herein, polydopamine (PDA)-functionalized strontium alginate/nanohydroxyapatite (Sr-Alg/nHA) composite microhydrogels loaded with vascular endothelial growth factor (VEGF) were prepared using microfluidic technology. This composite microhydrogel released strontium ions stably for at least 42 days to promote bone formation. The PDA coating can release VEGF in a controlled manner, effectively promote angiogenesis around bone defects, and provide nutritional support for new bone formation. In in vitro experiments, the composite microhydrogels had good biocompatibility. The PDA coating greatly improves cell adhesion on the composite microhydrogel and provides good controlled release of VEGF. Therefore, this composite microhydrogel effectively promotes osteogenic differentiation and vascularization. In in vivo experiments, composite microhydrogels were injected into critical-size bone defects in the skull of rats, and they were shown by microcomputed tomography and tissue sections to be effective in promoting bone regeneration. These findings demonstrated that this novel microhydrogel effectively promotes bone formation and angiogenesis at the site of bone defects.

A bioinspired synthetic fused protein adhesive from barnacle cement and spider dragline for potential biomedical materials

Biomaterials with excellent biocompatibility, mechanical performance, and self-recovery properties are urgently needed for tissue regeneration. Inspired by barnacle cement and spider silk, we genetically designed and overexpressed a fused protein (cp19k-MaSp1) composed of Megabalanus rosa (cp19k) and Nephila clavata dragline silk protein (MaSp1) in Pichia pastoris. The recombinant cp19k-MaSp1 exhibited enhanced adhesion capability beyond those of the individual proteins in both aqueous and non-aqueous conditions. cp19k-MaSp1 protein fiber scaffolds prepared through electrospinning have adequate hydrophilicity compared to cp19k and MaSp1 protein fiber scaffolds, and offer improved overall porosity compared to MaSp1 protein fiber scaffolds. The cp19k-MaSp1 protein fiber scaffolds showed excellent proteolytically stable properties because of only 9.6 % depletion after incubation in a biodegradation solution for 56 d. The cp19k-MaSp1 protein fiber scaffolds present remarkably high extreme tensile strength (112.7 ± 11.6 MPa) and superior ductility (438.4 ± 43.9 %) compared with cp19k (34.4 ± 8.1 MPa, 115.4 ± 32.7 %) and MaSp1 protein fiber scaffolds (65.8 ± 9.3 MPa, 409.6 ± 23.1 %), also 68.4 % of tensile strength was recovered by incubation in K+ buffer after multiple stretches, which create a favorable cell adhesion, growth, and proliferation environment for human umbilical vein endothelial cells (HUVECs). The improved biocompatibility, extensive adhesion, mechanical strength, and self-recovery properties make the bioinspired synthetic cp19k-MaSp1 a potential candidate for biomedical tissue reconstruction.

Intelligent Vascularized 3D/4D/5D/6D-Printed Tissue Scaffolds

Blood vessels are essential for nutrient and oxygen delivery and waste removal. Scaffold-repairing materials with functional vascular networks are widely used in bone tissue engineering. Additive manufacturing is a manufacturing technology that creates three-dimensional solids by stacking substances layer by layer, mainly including but not limited to 3D printing, but also 4D printing, 5D printing and 6D printing. It can be effectively combined with vascularization to meet the needs of vascularized tissue scaffolds by precisely tuning the mechanical structure and biological properties of smart vascular scaffolds. Herein, the development of neovascularization to vascularization to bone tissue engineering is systematically discussed in terms of the importance of vascularization to the tissue. Additionally, the research progress and future prospects of vascularized 3D printed scaffold materials are highlighted and presented in four categories: functional vascularized 3D printed scaffolds, cell-based vascularized 3D printed scaffolds, vascularized 3D printed scaffolds loaded with specific carriers and bionic vascularized 3D printed scaffolds. Finally, a brief review of vascularized additive manufacturing-tissue scaffolds in related tissues such as the vascular tissue engineering, cardiovascular system, skeletal muscle, soft tissue and a discussion of the challenges and development efforts leading to significant advances in intelligent vascularized tissue regeneration is presented.

Mechanism and application of 3D-printed degradable bioceramic scaffolds for bone repair

Bioceramics have attracted considerable attention in the field of bone repair because of their excellent osteogenic properties, degradability, and biocompatibility. To resolve issues regarding limited formability, recent studies have introduced 3D printing technology for the fabrication of bioceramic bone repair scaffolds. Nevertheless, the mechanisms by which bioceramics promote bone repair and clinical applications of 3D-printed bioceramic scaffolds remain elusive. This review provides an account of the fabrication methods of 3D-printed degradable bioceramic scaffolds. In addition, the types and characteristics of degradable bioceramics used in clinical and preclinical applications are summarized. We have also highlighted the osteogenic molecular mechanisms in biomaterials with the aim of providing a basis and support for future research on the clinical applications of degradable bioceramic scaffolds. Finally, new developments and potential applications of 3D-printed degradable bioceramic scaffolds are discussed with reference to experimental and theoretical studies.

Latest advances: Improving the anti-inflammatory and immunomodulatory properties of PEEK materials

Excellent biocompatibility, mechanical properties, chemical stability, and elastic modulus close to bone tissue make polyetheretherketone (PEEK) a promising orthopedic implant material. However, biological inertness has hindered the clinical applications of PEEK. The immune responses and inflammatory reactions after implantation would interfere with the osteogenic process. Eventually, the proliferation of fibrous tissue and the formation of fibrous capsules would result in a loose connection between PEEK and bone, leading to implantation failure. Previous studies focused on improving the osteogenic properties and antibacterial ability of PEEK with various modification techniques. However, few studies have been conducted on the immunomodulatory capacity of PEEK. New clinical applications and advances in processing technology, research, and reports on the immunomodulatory capacity of PEEK have received increasing attention in recent years. Researchers have designed numerous modification techniques, including drug delivery systems, surface chemical modifications, and surface porous treatments, to modulate the post-implantation immune response to address the regulatory factors of the mechanism. These studies provide essential ideas and technical preconditions for the development and research of the next generation of PEEK biological implant materials. This paper summarizes the mechanism by which the immune response after PEEK implantation leads to fibrous capsule formation; it also focuses on modification techniques to improve the anti-inflammatory and immunomodulatory abilities of PEEK. We also discuss the limitations of the existing modification techniques and present the corresponding future perspectives.

Influence of mechanochemically fabricated nano-hardystonite reinforcement in polycaprolactone scaffold for potential use in bone tissue engineering: Synthesis and characterization

Bone tissue engineering (BTE) has gained significant attention for the regeneration of bone tissue, particularly for critical-size bone defects. The aim of this research was first to synthesize nanopowders of hardystonite (HT) through ball milling and then to manufacture composite scaffolds for BTE use out of polycaprolactone (PCL) containing 0, 3, 5, and 10 wt% HT by electrospinning method. The crystallite size of the synthesized HT nanopowders was 42.8 nm. including up to 5 wt% HT into PCL scaffolds resulted in significant improvements, such as a reduction in the fiber diameter from 186.457±15.74 to 150.021±21.99 nm, a decrease in porosity volume from 85.2±2.5 to 80.3±3.3 %, an improvement in the mechanical properties (ultimate tensile strength: 5.7±0.2 MPa, elongation: 47.5±3.5 %, tensile modulus: 32.7±0.9 MPa), an improvement in the hydrophilicity, and biodegradability. Notably, PCL/5%HT exhibited the maximum cell viability (194±14 %). Additionally, following a 4-week of submersion in simulated body fluid (SBF), the constructed PCL/HT composite scaffolds showed a remarkable capacity to stimulate the development of hydroxyapatite (HA), which increased significantly for the 5 wt% HT scaffolds. However, at 10 wt% HT, nanopowder agglomeration led to an increase in the fiber diameter and a decrease in the mechanical characteristics. Collectively, the PCL/5%HT composite scaffolds can therefore help with the regeneration of the critical-size bone defects and offer tremendous potential for BTE applications.

A tough injectable self‐setting cement‐based hydrogel for noninvasive bone augmentation

Composite hydrogels with excellent properties can open new opportunities to terminate the need for auto/allografts in bone augmentations. However, their clinical application has been limited by their insufficient mechanical strength and lack of osteoinductivity. Here we report a new strategy to design an injectable bioactive double network hydrogel reinforced by inorganic calcium/magnesium phosphate cement (CMPC) hydrates to meet the mechanical performance requirements for bone regeneration. The engineered CMPC hydration endows the composite hydrogel with an appropriate gelation time and temperature for injection, which shows no harm in the defect site. CMPC hydrates could also provide a lower swelling ratio and higher biodegradation rate fitting the in vivo bone regeneration needs. In vitro and in vivo experiments prove that the ions released from inorganic particles endow biocompatibility, cell migration, adhesion, differentiation, and significantly higher bone regeneration capacity. Taken together, the simple addition of CMPC particles imparts in‐demand features that bring us closer to the clinical utilization of hydrogel‐based materials for bone regeneration.

Research progress of 3D printed poly (ether ether ketone) in the reconstruction of craniomaxillofacial bone defects

The clinical challenge of bone defects in the craniomaxillofacial region, which can lead to significant physiological dysfunction and psychological distress, persists due to the complex and unique anatomy of craniomaxillofacial bones. These critical-sized defects require the use of bone grafts or substitutes for effective reconstruction. However, current biomaterials and methods have specific limitations in meeting the clinical demands for structural reinforcement, mechanical support, exceptional biological performance, and aesthetically pleasing reconstruction of the facial structure. These drawbacks have led to a growing need for novel materials and technologies. The growing development of 3D printing can offer significant advantages to address these issues, as demonstrated by the fabrication of patient-specific bioactive constructs with controlled structural design for complex bone defects in medical applications using this technology. Poly (ether ether ketone) (PEEK), among a number of materials used, is gaining recognition as a feasible substitute for a customized structure that closely resembles natural bone. It has proven to be an excellent, conformable, and 3D-printable material with the potential to replace traditional autografts and titanium implants. However, its biological inertness poses certain limitations. Therefore, this review summarizes the distinctive features of craniomaxillofacial bones and current methods for bone reconstruction, and then focuses on the increasingly applied 3D printed PEEK constructs in this field and an update on the advanced modifications for improved mechanical properties, biological performance, and antibacterial capacity. Exploring the potential of 3D printed PEEK is expected to lead to more cost-effective, biocompatible, and personalized treatment of craniomaxillofacial bone defects in clinical applications.

Advances and Prospects in Materials for Craniofacial Bone Reconstruction

The craniofacial region is composed of 23 bones, which provide crucial function in keeping the normal position of brain and eyeballs, aesthetics of the craniofacial complex, facial movements, and visual function. Given the complex geometry and architecture, craniofacial bone defects not only affect the normal craniofacial structure but also may result in severe craniofacial dysfunction. Therefore, the exploration of rapid, precise, and effective reconstruction of craniofacial bone defects is urgent. Recently, developments in advanced bone tissue engineering bring new hope for the ideal reconstruction of the craniofacial bone defects. This report, presenting a first-time comprehensive review of recent advances of biomaterials in craniofacial bone tissue engineering, overviews the modification of traditional biomaterials and development of advanced biomaterials applying to craniofacial reconstruction. Challenges and perspectives of biomaterial development in craniofacial fields are discussed in the end.

Lnc-PPP2R1B Mediates the Alternative Splicing of PPP2R1B by Interacting and Stabilizing HNRNPLL and Promotes Osteogenesis of MSCs

Osteogeinc differentiation from mesenchymal stem cells (MSCs) into osteoblasts is a key step for bone tissue engineering in regenerative medicine. The insight into regulatory mechanism of osteogenesis of MSCs facilitates achieving better recovery effect. Long non-coding RNAs are regarded as a family of important moderators in osteogenesis. In this study, we found a novel lncRNA, lnc-PPP2R1B was up-regulated during osteogenesis of MSCs by Illumina HiSeq transcritome sequencing. We demonstrated lnc-PPP2R1B overexpression promoted osteogenesis and knockdown of lnc-PPP2R1B inhibited osteogenesis of MSCs. Mechanically, it physically interacted with and up-regulated heterogeneous nuclear ribonucleoprotein L Like (HNRNPLL), which is a master regulator of activation-induced alternative splicing in T cells. We found lnc-PPP2R1B knockdown or HNRNPLL knockdown decreased transcript-201 of Protein Phosphatase 2A, Regulatory Subunit A, Beta Isoform (PPP2R1B) while increased transcript-203 of PPP2R1B, and did not affect transcript-202/204/206. PPP2R1B is a constant regulatory subunit of protein phosphatase 2 (PP2A), which activates Wnt/β-catenin pathway by removing phosphorylation and stabilization of β-catenin and translocation into nucleus. The transcript-201 retained exon 2 and 3, compared to transcript-203. And it was reported the exon 2 and 3 of PPP2R1B were one part of B subunit binding domain on A subunit in PP2A trimer, and therefore retaining exon 2 and 3 promised formation and enzyme function of PP2A. Finally, lnc-PPP2R1B promoted ectopic osteogenesis in vivo. Conclusively, lnc-PPP2R1B mediated alternative splicing of PPP2R1B through retaining exon 2 and 3 by interacting with HNRNPLL and then promoted osteogenesis, which may facilitate an in-depth understanding of function and mechanism of lncRNAs in osteogenesis. Lnc-PPP2R1B interacted with HNRNPLL, and regulated alternative splicing of PPP2R1B through retaining exon 2 and 3, which preserved enzyme function of PP2A and enhanced dephosphorylation and nuclear translocation of β-catenin, thereby promoting Runx2 and OSX expression and then osteogenesis. And it provided experimental data and potential target for promoting bone formation and bone regeneration.

Optimization and manufacture of polyetheretherketone patient specific cranial implants by material extrusion - A clinical perspective

Polyetheretherketone (PEEK) is a high performing thermoplastic that has established itself as a 'gold-standard' material for cranial reconstruction. Traditionally, milled PEEK patient specific cranial implants (PSCIs) exhibit uniform levels of smoothness (excusing suture/drainage holes) to the touch (<1 μm) and homogenous coloration throughout. They also demonstrate predictable and repeatable levels of mechanical performance, as they are machined from isotropic material blocks. The combination of such factors inspires confidence from the surgeon and in turn, approval for implantation. However, manufacturing lead-times and affiliated costs to fabricate a PSCI are high. To simplify their production and reduce expenditure, hospitals are exploring the production of in-house PEEK PSCIs by material extrusion-based additive manufacturing. From a geometrical and morphological perspective, such implants have been produced with good-to-satisfactory clinical results. However, lack of clinical adoption persists. To determine the reasoning behind this, it was necessary to assess the benefits and limitations of current printed PEEK PSCIs in order to establish the status quo. Afterwards, a review on individual PEEK printing variables was performed in order to identify a combination of parameters that could enhance the aesthetics and performance of the PSCIs to that of milled implants/cranial bone. The findings from this review could be used as a baseline to help standardize the production of PEEK PSCIs by material extrusion in the hospital.

Polyetheretherketone (PEEK) as a Potential Material for the Repair of Maxillofacial Defect Compared with E-poly(tetrafluoroethylene) (e-PTFE) and Silicone

Silicone and e-poly(tetrafluoroethylene) (e-PTFE) are the most commonly used artificial materials for repairing maxillofacial bone defects caused by facial trauma and tumors. However, their use is limited by poor histocompatibility, unsatisfactory support, and high infection rates. Polyetheretherketone (PEEK) has excellent mechanical strength and biocompatibility, but its application to the repair of maxillofacial bone defects lacks a theoretical basis. The microstructure and mechanical properties of e-PTFE, silicone, and PEEK were evaluated by electron microscopy, BOSE machine, and Fourier transformed infrared spectroscopy. Mouse fibroblast L929 cells were incubated on the surface of the three materials to assess cytotoxicity and adhesion. The three materials were implanted onto the left femoral surface of 90 male mice, and samples of the implants and surrounding soft tissues were evaluated histologically at 1, 2, 4, 8, and 12 weeks post-surgery. PEEK had a much higher Young's modulus than either e-PTFE or silicone (p < 0.05 each), and maintained high stiffness without degradation long after implantation. Both PEEK and e-PTFE facilitated L929 cell adhesion, with PEEK having lower cytotoxicity than e-PTFE and silicone (p < 0.05 each). All three materials similarly hindered the motor function of mice 12 weeks after implantation (p > 0.05 each). Connective tissue ingrowth was observed in PEEK and e-PTFE, whereas a fibrotic peri-prosthetic capsule was observed on the surface of silicone. The postoperative infection rate was significantly lower for both PEEK and silicone than for e-PTFE (p < 0.05 each). PEEK shows excellent biocompatibility and mechanical stability, suggesting that it can be effective as a novel implant to repair maxillofacial bone defects.

Self‐Tandem Bio‐Heterojunctions Empower Orthopedic Implants with Amplified Chemo‐Photodynamic Anti‐Pathogenic Therapy and Boosted Diabetic Osseointegration

Hyperglycemic microenvironment in diabetes mellitus inevitably stalls the normal orchestrated course of bone regeneration and encourages pathogenic multiplication. Photodynamic therapy (PDT) and chemo‐dynamic therapy (CDT) are extensively harnessed to combat pathogens, yet deep‐seated diabetic bone defect has difficulty in supplying sufficient oxygen (O2) and hydrogen peroxide (H2O2) stocks, resulting in inferior therapeutic efficiency. To address the tough plaguing, the self‐tandem bio‐heterojunctions (bio‐HJs) consisting of molybdenum disulfide (MoS2), graphene oxide (GO), and glucose oxidase (GOx) are constructed on orthopedic polyetheretherketone (PEEK) implants (SP‐Mo/G@GOx) for amplified chemo‐photodynamic anti‐pathogenic therapy and boosted osseointegration in the deep‐seated diabetic micromilieu. In this system, GOx exhausts glucose to generate H2O2, which provides an abundant stock for CDT. Besides, the bio‐HJs produce hyperthermia upon near‐infrared light (NIR) to accelerate the dynamic process, which amplifies the antibacterial potency of PDT by promoting the vast yield of singlet oxygen (1O2) in a self‐tandem manner. More importantly, in vivo and in vitro assays demonstrate that the engineered implants exert a captivated bactericidal ability and significantly boost osseointegration in an infectious diabetic bone defect model. As envisaged, this study furnishes a novel tactic to arm orthopedic implants with self‐tandem capability for the remedy of infectious diabetic bone defects.

Advancement in biological and mechanical behavior of 3D printed poly lactic acid bone plates using polydopamine coating: Innovation for healthcare

The metallic biomaterials have been proclaimed to exhibit stress shielding with discharge of toxic ions, leading to polymeric implants attracting interest in 3D Printing domain. In this study, Poly Lactic Acid based 336 bone plates are fabricated using Fused Filament Fabrication with printing parameters being varied. Polydopamine, being biocompatible, is deposited on fabricated bone plates at varying submersion time, shaker speed and coating solutions concentration. The study involves witnessing the effect of printing and coating parameters on biological behavior of bone plates upon preservation in Simulated Body Fluid and Hank's Balanced Salt Solution. The findings propose the close relation of degradation with apatite growth. The highest degradation rate with significant reduction in mechanical characteristics are shown by uncoated bone plates. These bone plates have porous structure at 20% infill density, 0.5 mm layer height, 0.4 mm wall thickness and 100 mm/s print speed which could result in complete degradation with partial healing of bone fracture. The study suggests the preservation of bone plates coated at 120 h' submersion time and 120 RPM shaker speed in 3 mg/ml concentrated solution which showed lower apatite formation. Thus, the coating would slow down degradation of PLA bone plates, resulting in complete healing of bone fracture.