Bioinspired Strong and Highly Porous Glass Scaffolds

The quest for more efficient energy-related technologies is driving the development of porous and high-performance structural materials with exceptional mechanical strength. Natural materials achieve their strength through complex hierarchical designs and anisotropic structures that are extremely difficult to replicate synthetically. We emulate nature's design by direct-ink-write assembling of glass scaffolds with a periodic pattern, and controlled sintering of the filaments into anisotropic constructs similar to biological materials. The final product is a porous glass scaffold with a compressive strength (136 MPa) comparable to that of cortical bone and a porosity (60%) comparable to that of trabecular bone. The strength of this porous glass scaffold is ~100 times that of polymer scaffolds and 4-5 times that of ceramic and glass scaffolds with comparable porosities reported elsewhere. The ability to create both porous and strong structures opens a new avenue for fabricating scaffolds for a broad array of applications, including tissue engineering, filtration, lightweight composites, and catalyst support.     

Direct 3D Printing of High Strength Biohybrid Gradient Hydrogel Scaffolds for Efficient Repair of Osteochondral Defect

The emerging 3D printing technique allows for tailoring hydrogel‐based soft structure tissue scaffolds for individualized therapy of osteochondral defects. However, the weak mechanical strength and uncontrollable swelling intrinsic to conventional hydrogels restrain their use as bioinks. Here, a high‐strength thermoresponsive supramolecular copolymer hydrogel is synthesized by one‐step copolymerization of dual hydrogen bonding monomers, N‐acryloyl glycinamide, and N‐[tris(hydroxymethyl)methyl] acrylamide. The obtained copolymer hydrogels demonstrate excellent mechanical properties—robust tensile strength (up to 0.41 MPa), large stretchability (up to 860%), and high compressive strength (up to 8.4 MPa). The rapid thermoreversible gel ? sol transition behavior makes this copolymer hydrogel suitable for direct 3D printing. Successful preparation of 3D‐printed biohybrid gradient hydrogel scaffolds is demonstrated with controllable 3D architecture, owing to shear thinning property which allows continuous extrusion through a needle and also immediate gelation of fluid upon deposition on the cooled substrate. Furthermore, this biohybrid gradient hydrogel scaffold printed with transforming growth factor beta 1 and β‐tricalciumphosphate on distinct layers facilitates the attachment, spreading, and chondrogenic and osteogenic differentiation of human bone marrow stem cells (hBMSCs) in vitro. The in vivo experiments reveal that the 3D‐printed biohybrid gradient hydrogel scaffolds significantly accelerate simultaneous regeneration of cartilage and subchondral bone in a rat model.     

Biomimetic Elastomeric Bioactive Siloxane‐Based Hybrid Nanofibrous Scaffolds with miRNA Activation: A Joint Physico‐Chemical‐Biological Strategy for Promoting Bone Regeneration

Rapid and efficient disease‐induced or critical‐size bone regeneration remains a challenge in tissue engineering due to the lack of highly bioactive biomaterial scaffolds. Physical structures such as nanostructures, chemical components such as silicon elements, and biological factors such as genes have shown positive effects on bone regeneration. Herein, a bioactive photoluminescent elastomeric silicate‐based nanofibrous scaffold with sustained miRNA release is reported for promoting bone regeneration based on a joint physico‐chemical‐biological strategy. Bioactive nanofibrous scaffolds are fabricated by cospinning poly (ε‐caprolactone) (PCL), elastomeric poly (citrates‐siloxane) (PCS), and bioactive osteogenic miRNA nanocomplexes (denoted PPM nanofibrous scaffolds). The PPM scaffolds possess uniform nanostructures, significantly enhanced tensile stress (≈15 MPa) and modulus (≈32 MPa), improved hydrophilicity (30–60°), controlled biodegradation, and strong blue fluorescence. Bioactive miRNA complexes are efficiently loaded into the nanofibrous matrix and exhibit long‐term release for up to 70 h. The PPM scaffolds significantly promote the adhesion, proliferation, and osteoblast differentiation of bone marrow stem cells in vitro and enhanced rat cranial defect restoration (12 weeks) in vivo. This work reports an attractive joint physico‐chemical‐biological strategy for the design of novel cell/protein‐free bioactive scaffolds for synergistic tissue regeneration.     

Transparent Nacre‐like Composites Toughened through Mineral Bridges

Bulk materials with remarkable mechanical properties have been developed by incorporating design principles of biological nacre into synthetic composites. However, this potential has not yet been fully leveraged for the fabrication of tough and strong materials that are also optically transparent. In this work, a manufacturing route that enables the formation of nacre‐like mineral bridges in a bioinspired composite consisting of glass platelets infiltrated with an index‐matching polymer matrix is developed. By varying the pressure applied during compaction of the glass platelets, composites with tunable levels of mineral bridges and platelet interconnectivity can be easily fabricated. The effect of platelet interconnectivity on the mechanical strength and fracture behavior of the bioinspired composites is investigated by performing state‐of‐the‐art fracture experiments combined with in situ electron microscopy. The results show that the formation of interconnections between platelets leads to bulk transparent materials with an unprecedented combination of strength and fracture toughness. This unusual set of properties can potentially fulfill currently unmet demands in electronic displays and related technologies.     

Bioinspired Highly Anisotropic,Ultrastrong and Stiff,and Osteoconductive Mineralized Wood Hydrogel Composites for Bone Repair

Anisotropic hydrogels mimicking the biological tissues with directional functions play essential roles in damage-tolerance, cell guidance and mass transport. However, conventional synthetic hydrogels often have an isotropic network structure, insufficient mechanical properties and lack of osteoconductivity, which greatly limit their applications for bone repair. Herein, inspired by natural bone and wood, a biomimetic strategy is presented to fabricate highly anisotropic, ultrastrong and stiff, and osteoconductive hydrogel composites via impregnation of biocompatible hydrogels into the delignified wood followed by in situ mineralization of hydroxyapatite (HAp) nanocrystals. The well-aligned cellulose nanofibrils endow the composites with highly anisotropic structural and mechanical properties. The strong intermolecular bonds of the aligned cellulose fibrils and hydrogel/wood interaction, and the reinforcing nanofillers of HAp enable the composites remarkable tensile strength of 67.8 MPa and elastic modulus of 670 MPa, three orders of magnitude higher than those of conventional alginate hydrogels. More importantly, the biocompatible hydrogel together with aligned HAp nanocrystals could effectively promote osteogenic differentiation in vitro and induce bone formation in vivo. The bone ingrowth into the hydrogel composite scaffold also yields good osteointegration. This study provides a low-cost, eco-friendly, feasible, and scalable approach for fabricating anisotropic, strong, stiff, hydrophilic, and osteoconductive hydrogel composites for bone repair.     

Polymer Fiber Scaffolds for Bone and Cartilage Tissue Engineering

Successful regeneration of weight‐bearing bone defects and critical‐sized cartilage defects remains a major challenge in clinical orthopedics. In the past decades, biodegradable polymer materials with biomimetic chemical and physical properties have been rapidly developed as ideal candidates for bone and cartilage tissue engineering scaffolds. Due to their unique advantages over other materials of high specific‐surface areas, suitable mechanical strength, and tailorable characteristics, scaffolds made of polymer fibers have been increasingly used for the repair of bone and cartilage defects. This Review summarizes the preparation and compositions of polymer fibers, as well as their characteristics. More importantly, the applications of polymer fiber scaffolds with well‐designed structures or unique properties in bone, cartilage, and osteochondral tissue engineering have been comprehensively highlighted. On the whole, such a comprehensive summary affords constructive suggestions for the development of polymer fiber scaffolds in bone and cartilage tissue engineering.     

Scaling the Stiffness,Strength, and Toughness of Ceramic‐Coated Nanotube Foams into the Structural Regime

Natural materials such as bone and tooth achieve precisely tuned mechanical and interfacial properties by varying the concentration and orientation of their nanoscale constituents. However, the realization of such control in engineered foams is limited by manufacturing‐driven tradeoffs among the size, order, and dispersion uniformity of the building blocks. It is demonstrated how to manufacture nanocomposite foams with precisely controllable mechanical properties via aligned carbon nanotube (CNT) growth followed by atomic layer deposition (ALD). By starting with a low density CNT forest and varying the ALD coating thickness, we realize predictable ≈1000‐fold control of Young's modulus (14 MPa to 20 GPa, where E ～ ρ ^2.8), ultimate compressive strength (0.8 MPa to 0.16 GPa), and energy absorption (0.4 to 400 J cm^–3). Owing to the continuous, long CNTs within the ceramic nanocomposite, the compressive strength and toughness of the new material are 10‐fold greater than commercially available aluminum foam over the same density range. Moreover, the compressive stiffness and strength equal that of compact bone at 10% lower density. Along with emerging technologies for scalable patterning and roll‐to‐roll manufacturing and lamination of CNT films, coated CNT foams may be especially suited to multifunctional applications such as catalysis, filtration, and thermal protection.     

Light and Strong SiC Networks

The directional freezing of microfiber suspensions is used to assemble highly porous (porosities ranging between 92% and 98%) SiC networks. These networks exhibit a unique hierarchical architecture in which thin layers with honeycomb‐like structure and internal strut length in the order of 1–10 μm in size are aligned with an interlayer spacing ranging between 15 and 50 μm. The resulting structures exhibit strengths (up to 3 MPa) and stiffness (up to 0.3 GPa) that are higher than aerogels of similar density and comparable to other ceramic microlattices fabricated by vapor deposition. Furthermore, this wet processing technique allows the fabrication of large‐size samples that are stable at high temperature, with acoustic impedance that can be manipulated over one order of magnitude (0.03–0.3 MRayl), electrically conductive and with very low thermal conductivity. The approach can be extended to other ceramic materials and opens new opportunities for the fabrication of ultralight structures with unique mechanical and functional properties in practical dimensions.     

Recent Advances in Design of Functional Biocompatible Hydrogels for Bone Tissue Engineering

Bone related diseases have caused serious threats to human health owing to their complexity and specificity. Fortunately, owing to the unique 3D network structure with high aqueous content and functional properties, emerging hydrogels are regarded as one of the most promising candidates for bone tissue engineering, such as repairing cartilage injury, skull defect, and arthritis. Herein, various design strategies and synthesis methods (e.g., 3D-printing technology and nanoparticle composite strategy) are introduced to prepare implanted hydrogel scaffolds with tunable mechanical strength, favorable biocompatibility, and excellent bioactivity for applying in bone regeneration. Injectable hydrogels based on biocompatible materials (e.g., collagen, hyaluronic acid, chitosan, polyethylene glycol, etc.) possess many advantages in minimally invasive surgery, including adjustable physicochemical properties, filling irregular shapes of defect sites, and on-demand release drugs or growth factors in response to different stimuli (e.g., pH, temperature, redox, enzyme, light, magnetic, etc.). In addition, drug delivery systems based on micro/nanogels are discussed, and its numerous promising designs used in the application of bone diseases (e.g., rheumatoid arthritis, osteoarthritis, cartilage defect) are also briefed in this review. Particularly, several key factors of hydrogel scaffolds (e.g., mechanical property, pore size, and release behavior of active factors) that can induce bone tissue regeneration are also summarized in this review. It is anticipated that advanced approaches and innovative ideas of bioactive hydrogels will be exploited in the clinical field and increase the life quality of patients with the bone injury.     

Strength of fusion splices for fibre lightguides

Fusion splices with median strengths in the range 2.1?2.8 GPa and coefficients of variation of about 40% have been obtained for synthetic fused silica fibre as well as for single mode and multimode lightguides using either flame, arc or laser heating. Although the strength distributions are broad, 90% of the splices have strengths above 1.4 GPa. These strengths, which are significantly higher than those previously reported, have been achieved by avoiding mechanical damage to the glass surface.     

Laser Spinning of Bioactive Glass Nanofibers

The production of nanofibers of bioactive glass by laser spinning is reported. The technique yields a great quantity of free‐standing fibers in the form of a mesh of disordered intertwined fibers. The method does not rely on chemical processing and does not need any chemical additive. It involves melting of a precursor material with tailored composition, which makes it possible to produce nanofibers from materials with which conventional melt drawing techniques cannot be used. Herein, the production of 45S5 Bioglass nanofibers is reported for the first time. The process is very fast (nanofibers of several centimeters are grown in a fraction of a second), without the necessity of post heat treatments, and no devitrification is observed as a result of the laser‐spinning process. The morphology, composition, and structure of the nanofibers are characterized and an assessment of their bioactivity is carried out by immersion in simulated body fluid. This technique provides a method for the rapid production of dense glass nanofibers that can be employed as bioactive nanocomposite reinforcement, as a synthetic bone graft to replace missing bone, or to produce 3D structures for use as scaffolds for bone‐tissue engineering.     

高抗弯强度微波介电LTCC基板材料的研究

为了适应基板高载荷、高可靠的要求,制备了一种适用于LTCC应用的高抗弯强度微波介电陶瓷材料。该陶瓷材料由Ca-Mg-Zr-Zn-B-Si微晶玻璃和氧化铝构成。采用差热热重同步分析仪、扫描电镜、X射线衍射分析仪、带谐振腔夹具的矢量网络分析仪和三点抗弯测试仪研究了陶瓷材料的烧结性能、微观结构、抗弯强度和介电性能。860℃烧结15 min获得陶瓷具有最佳致密度,其抗弯强度大于400 MPa,1. 9 GHz频率时εr=8. 12,tanδ=0. 0028;15 GHz频率时εr=7. 96,tanδ=0. 0031。该陶瓷与金、银电极共烧匹配良好,适用于制备LTCC基板。     

Ultra-High Toughness Fibers Using Controlled Disorder of Assembled Aramid Nanofibers

Assembling nanoscale building blocks with reduced defects has emerged as a promising approach to exploit nanomaterials in the fabrication of simultaneously strong and tough architectures at larger scales. Aramid nanofibers (ANFs), a type of organic nanobuilding block, have been spotlighted due to their superior mechanical properties and thermal stability. However, no breakthrough research has been conducted on the high mechanical properties of a structure composed of ANFs. Here, assembling ANFs into macroscale fiber using a simultaneous protonation and wet-spinning process is studied to reduce defects and control disorder. The ANF-assembled fibers consist of hierarchically aligned nanofibers that behave as a defective law structure, making it possible to reach a Young's modulus of 53.15 ± 8.98 GPa, a tensile strength of 1,353.64 ± 92.98 MPa, and toughness of 128.66 ± 14.13 MJ m⁻³. Compared to commercial aramid fibers, the fibers exhibit ≈1.6 times greater toughness while also providing specific energy to break as 93 J g⁻¹. Furthermore, this shows recyclability of the ANF assembly by retaining ≈94% of the initial mechanical properties. This study demonstrates a facile process to produce high stiffness and strength fibers composed of ANFs that possess significantly greater toughness than commercial synthetic fibers.     

Recent Advances in Electrospun Nanofibrous Scaffolds for Cardiac Tissue Engineering

Cardiovascular diseases remain the leading cause of human mortality worldwide. Some severe symptoms, including myocardial infarction and heart failure, are difficult to heal spontaneously or under systematic treatment due to the limited regenerative capacity of the native myocardium. Cardiac tissue engineering has emerged as a practical strategy to culture functional cardiac tissues and relieve the disorder in myocardium when implanted. In cardiac tissue engineering, the design of a scaffold is closely relevant to the function of the regenerated cardiac tissues. Nanofibrous materials fabricated by electrospinning have been developed as desirable scaffolds for tissue engineering applications because of the biomimicking structure of protein fibers in native extra cellular matrix. The versatilities of electrospinning on the polymer component, the fiber structure, and the functionalization with bioactive molecules have made the fabrication of nanofibrous scaffolds with suitable mechanical strength and biological properties for cardiac tissue engineering feasible. Here, an overview of recent advances in various electrospun scaffolds for engineering cardiac tissues, including the design of advanced electrospun scaffolds and the performance of the scaffolds in functional cardiac tissue regeneration, is provided with the aim to offer guidance in the innovation of novel electrospun scaffolds and methods for improving their potential for cardiac tissue engineering applications.     

Toughness and Fracture Properties in Nacre‐Mimetic Clay/Polymer Nanocomposites

Nacre inspires researchers by combining stiffness with toughness by its unique microstructure of aligned aragonite platelets. This brick‐and‐mortar structure of reinforcing platelets separated with thin organic matrix has been replicated in numerous mimics that can be divided into two categories: microcomposites with aligned metal oxide microplatelets in polymer matrix, and nanocomposites with self‐assembled nanoplatelets—usually clay or graphene oxide—and polymer. While microcomposites have shown exceptional fracture toughness, current fabrication methods have limited nacre‐mimetic nanocomposites to thin films where fracture properties remained unexplored. Yet, fracture resistance is the defining property of nacre, therefore centrally important in any mimic. Furthermore, to make use of these properties in applications, bulk materials are required. Here, up to centimeter‐thick nacre‐mimetic clay/polymer nanocomposites are produced by the lamination of self‐assembled films. The aligned clay nanoplatelets are separated by poly(vinyl alcohol) matrix, with 10⁶–10⁷ nanoplatelets on top of each other in the bulk plates. Fracture testing shows crack deflection and a fracture toughness of 3.4 MPa m^1/2, not far from nacre. Flexural tests show high stiffness (25 GPa) and strength (220 MPa) that, despite the hydrophilic constituents, are not substantially affected by exposure to humidity.     

ZTA陶瓷基板力学和光学性能的研究

以α-Al2O3粉体为主相材料,添加不同含量的ZrO2(体积分数0%~28%),采用流延成型工艺和常压烧结方法制备ZTA陶瓷样品,研究ZrO2的含量、气孔率、基板厚度以及白度对ZTA陶瓷基板力学和光学性能的影响。结果表明:随ZrO2含量增加,断裂韧性和抗弯强度呈现先增大后减小的趋势,ZrO2含量为体积分数20%时达到最大值,分别为5.7 MPa·m1/2和865 MPa;当ZrO2含量低于体积分数12%时,随气孔率增加,反射率升高;此外,ZTA陶瓷基板的厚度增加,反射率升高;白度下降,反射率也随之降低。最终制备出一种反射率达到100.7%,满足LED高光效需求的ZTA陶瓷基板。     

Cocrystal Strategy toward Multifunctional 3D‐Printing Scaffolds Enables NIR‐Activated Photonic Osteosarcoma Hyperthermia and Enhanced Bone Defect Regeneration

Malignant bone tumors are one of the major serious diseases in clinic. Inferior reconstruction of new bone and rapid propagation of residual tumor cells are the main challenges to surgical intervention. Herein, a bifunctional DTC@BG scaffold for near‐infrared (NIR)‐activated photonic thermal ablation of osteosarcoma and accelerated bone defect regeneration is engineered by in situ growth of NIR‐absorbing cocrystal (DTC) on the surface of a 3D‐printing bioactive glass (BG) scaffold. The prominent photothermal conversion performance and outstanding bone regeneration capability of DTC@BG scaffolds originate from the precise tailoring of the bandgap between the electron donors and acceptors of DTC and promote new bone growth performance of BG scaffolds. DTC@BG scaffolds not only significantly promote tumor cell ablation in vitro, but also effectively facilitate bone tumor suppression in vivo. In particular, DTC@BG scaffolds exhibit excellent capability in stimulating osteogenic differentiation and angiogenesis, and finally promote newborn bone formation in the bone defects. This research represents the first paradigm for ablating osteosarcoma and facilitating new bone formation through precise modulation of electron donors and acceptors in the cocrystal, which offers a new avenue to construct high‐efficiency therapeutic platforms based on cocrystal strategy for ablation of malignant bone tumor.     

Bio‐Inspired Synthesis of Minerals for Energy,Environment, and Medicinal Applications

Biomineralization, the natural pathway of assembling biogenic inorganic compounds, inspires us to exploit unique, effective strategies to fabricate functional materials with intricate structures. In this article, the recent advances in bio‐inspired synthesis of minerals—with a focus on those of calcium‐based minerals—and their applications to the design of functional materials for energy, environment, and biomedical fields are reviewed. Biomimetic mineralization is extending its application range to unconventional area such as the design of component materials for lithium‐ion batteries and elaborately structured composite materials utilizing carbon dioxide gas. Materials with highly enhanced mechanical properties are synthesized through emulating the nacre structure. Studies of bioactive minerals‐carbon hybrid materials show an expansion of potential applications to fields ranging from interdisciplinary science to practical engineering such as the fabrication of reinforced bone‐implantable materials.     

Simulation of Cortical and Cancellous Bone to Accelerate Tissue Regeneration

Different tissues have complex anisotropic structures to support biological functions. Mimicking these complex structures in vitro remains a challenge in biomaterials designs. Here, inspired by different types of silk nanofibers, a composite materials strategy is pursued toward this challenge. A combination of fabrication methods is utilized to achieve separate control of amorphous and beta-sheet rich silk nanofibers in the same solution. Aqueous solutions containing two types of silk nanofibers are simultaneously treated with an electric field and with ethylene glycol diglycidyl ether (EGDE). Under these conditions, the beta-sheet rich silk nanofibers in the mixture responded to the electric field while the amorphous nanofibers are active in the crosslinking process with the EGDE. As a result, cryogels with anisotropic structures are prepared, including mimics for cortical- and cancellous-like bone biomaterials as a complex osteoinductive niche. In vitro studies revealed that mechanical cues of the cryogels induced osteodifferentiation of stem cells while the anisotropy inside the cryogels influenced immune reactions of macrophages. These bioactive cryogels also stimulated improved bone regeneration in vivo through modulation of inflammation, angiogenesis and osteogenesis responses, suggesting an effective strategy to develop bioactive matrices with complex anisotropic structures beneficial to tissue regeneration.     

Strong,Tough, Electrospun Polymer–Nanotube Composite Membranes with Extremely Low Density

Electrospinning has been used to produce porous, low density, polymer–nanotube composite membranes. The membrane mechanical properties can be enhanced by tuning the nanotube content, aligning the fibers during spinning, and by post production drawing. The mechanical properties are maximized for membranes with a nanotube content of 0.43 vol %. Aligned composites at this volume fraction have been prepared by spinning onto a rotating drum collector electrode. This method results in significant increases in modulus, strength, and toughness. The best composites, produced at the maximum drum rotation rate, were post treated by a drawing step to result in further increases in modulus and strength. These methods allows the production of membranes with densities as low as ～340 kg m^?3 but with values of stiffness, strengths and toughness's more typically found in bulk thermoplastics; 1.2 GPa, 40 MPa, and 13 J g^?1.