Bio-Inspired Lotus-Fiber-like Spiral Hydrogel Bacterial Cellulose Fibers

Shark skin and mussel-inspired polyurethane hydrogel sponge for wounds with infection and exudate

Inspired by the antifouling properties of shark skin and the bioadhesion of mussels, our study presents a three-layer biomimetic wound dressing with hierarchical wettability and rapid exudate drainage capabilities. The shark skin-inspired hydrophobic modified polyurethane (PU) sponge provides antifouling properties and serves as a bacterial barrier. The mussel-inspired dopamine-functionalized carboxymethyl chitosan hydrogel (CMCS-DOP) absorbs exudates and forms an in situ hydrogel, effectively capturing and eliminating bacteria. The porous sponge layer in direct contact with the wound facilitates rapid exudate drainage, preventing excessive wound hydration. This hierarchical structure coordinates exudate transport and bacterial removal. The fabricated PCD hydrogel sponge dressing (PCD dressing) exhibits a wettability transition (contact angle: 3°-35°-101°) and a water vapor transmission rate of 1021-797-691 g/m2. It demonstrates potent bactericidal effects against Staphylococcus aureus and Escherichia coli, with survival rates of only 13 % and 14 %, respectively, and bacterial-blocking efficiencies of 89 % and 94 %. In a chronic bacterial infection wound model, the PCD dressing outperforms conventional clinical dressings, increasing the wound healing rate by 25.8 %, reducing inflammation, and enhancing angiogenesis and collagen deposition. Notably, the PCD mitigates oxidative stress at the wound site by regulating the polarization of anti-inflammatory macrophages. This exudate-draining and responsive dressing offers a promising strategy for promoting the healing of wounds with high exudate levels.

Nanocellulose hydrogels from agricultural wastes: methods, properties, and application prospects

Escalating environmental concerns and the depletion of non-renewable resources have intensified interest in sustainable and eco-friendly materials. Cellulose-based hydrogels, renowned for their biocompatibility, biodegradability, and excellent mechanical properties, have emerged as promising candidates for diverse applications, including biomedicine, agriculture, and water purification. This review focuses on methods for extracting nanocellulose from agricultural wastes and their use in creating cellulose hydrogels. Special emphasis is placed on the mechanical, chemical, thermal, and environmental properties of nanocellulose, as well as its applications in packaging materials, medical devices, biocomposites, and filtration systems. The literature review examines cellulose extraction methods, hydrogel properties, and their industrial applications. The key advantages and disadvantages of these methods are identified, and directions for future research are proposed. This work provides a comprehensive overview of the current state of research on cellulose-based hydrogels and contributes to the development of more efficient and sustainable production methods for these materials.

Processing wheat straw into strong and flexible cellulose fiber bundle: Waste-to-wealth strategy

The excessive reliance on traditional petroleum resources poses significant environmental challenges. Fortunately, agricultural straw, which is often regarded as a waste product, has considerable potential for various applications. However, these materials are frequently crushed into particles, thereby neglecting their inherent structural advantages. In this study, wheat straw is utilized in its complete form and converted to a strong and flexible fiber bundle. We employ a top-down approach on whole wheat straw that involves an alkali pretreatment combined with delignification and freeze-drying to obtain highly directional cellulose aggregates. Subsequent twist densification results in the formation of a strong, flexible wheat straw-derived fiber bundle (WFB). WFB exhibits an excellent strength of 203.9 MPa, representing a 3.4 improvement rate in relation to that of the initial straw. This indicates that agricultural waste can be transformed to a high-performance material, embodying the concept of "Waste to Wealth." In addition, WFB can be further functionalized (e.g., via hydrophobic treatment, dyeing treatment, or incorporation with a conductive material) on the basis of the abundant hydroxyl groups present on its surface. This strategy provides insights into the innovative utilization of straw and promotes its application in wearable textile and smart fiber development.

Mechanically robust, flexible, conductive, and anti-freezing hydrogels reinforced by cellulose of wood skeleton

Hydrogels are soft and wet materials, but their applications are always limited by insufficient mechanical strength and toughness, and they are prone to freezing at low temperatures. In this study, we introduced an eco-friendly approach to developing wood-based hydrogels reinforced by the naturally aligned wood skeleton (WS) through the Hofmeister effect. The resulting wood-based composite hydrogels exhibited a high tensile strength of 20 MPa and a strain of 35 % in the longitudinal direction. This impressive mechanical performance was primarily due to densely packed hydrogen bonding, physical entanglements, and van der Waals forces between the cellulose of WS, polyacrylamide (PAM), and poly(vinyl alcohol) (PVA) chains during polymerization. Notably, the polymerization was induced using wood carbon dots as initiators, imparting additional fluorescence features to the hydrogels. Afterward, by incorporating a metal salt (sodium chloride), the developed wood-based hydrogels maintained high conductivity (3.0 S/m) and mechanical properties even under low-temperature conditions (-20 °C). Moreover, the conductive hydrogels exhibited multifunctional sensing capabilities, including strain, temperature, and ultraviolet (UV) irradiation detection, making them highly suitable for applications in human motion monitoring and healthcare, particularly under harsh environmental conditions.

UV-Induced Photochromic Macrofibers Derived from Bacterial Cellulose

The emergence of photochromic fibers has created numerous opportunities in the realm of intelligent textiles and functional materials. However, commercially accessible photochromic fibers are predominantly produced from petroleum-based polymers, which contradicts the current emphasis on sustainability and minimizing carbon emissions. In this work, eco-friendly and fast-reversible photochromic bio-based bacterial cellulose (BC) macrofibers that are combined with 2,2,6,6-Tetramethylpiperidine-1-oxy (TEMPO) -oxidized BC (TOBC) nanofibers and spirooxazine-based photochromic microcapsules (PM) through amide reaction via a simple wet spinning strategy, are developed. The findings suggest that the highest breaking strength of the resulting macrofiber is attained at a PM concentration of 0.2 wt.%, reaching 1.51 cN/dtex, which is 14% greater than that of pure TOBC macrofibers produced. Prepared macrofibers with photochromic properties demonstrate fast response times of just 1 s, durability, and reversible color-changing characteristics when stimulated by ultraviolet (UV) light in the 200-400 nm range. As a proof-of-concept, UV-induced color-changing flowers and patterned textiles are demonstrated by the macrofiber integrated with normal yarns. In conclusion, these innovative bio-based polymer fibers can shine new light into the development of a new generation of anti-counterfeiting and fashion textiles.

Bio-inspired lotus-fiber and mussel-based multifunctional hydrogels for wound healing: super-stretchability, self-healing, adhesion and antibacterial properties

Hydrogel-based wound dressings, which facilitate rapid wound closure and healing, are essential for effective wound management. However, the development of an ideal hydrogel that possesses excellent mechanical properties, effective self-healing capabilities, tissue adherence and antimicrobial characteristics for wound dressing presents a significant challenge in clinical settings. Inspired by lotus-fiber and mussel, we synthesized a novel multifunctional hydrogel composed of bacterial cellulose-reinforced dopamine-grafted oxidized hyaluronic acid/polyacrylamide (OHA-DA/PAM/BC). This was achieved through a one-pot reaction that employed free radical polymerization of acrylamide, dynamic Schiff bonding and intermolecular hydrogen bonding. Compared with the pure PAM hydrogels, which exhibited an elongation at break of 4022% and a maximum tensile strength of 26.42 kPa, the OHA-DA/PAM hydrogel demonstrated significantly enhanced stretchability at 9949% and an increased tensile strength of 34.73 kPa when 0.3% OHA-DA was incorporated during hydrogel formulation. Notably, the addition of 0.8% BC significantly enhanced the tensile strength to 57.04 kPa and super-stretchability to 10679%. The OHA-DA/PAM/BC hydrogel also exhibited remarkable self-healing capabilities, achieving a mechanical recovery of 84.74% within 12 h. Additionally, its adhesive and injectable properties are advantageous for dynamic wound repair. Furthermore, the OHA-DA/PAM/BC hydrogel exhibited minimal hemolytic activity and potent intrinsic antibacterial properties against both Escherichia coli and Staphylococcus aureus. In a mouse model of wound healing, this hydrogel reduced the healing duration to 14 days while enhancing the regeneration of both skin structure and function. Histological analyses further revealed that the hydrogel significantly promoted the development of well-organized granulation tissue, angiogenic tissue and collagen accumulation in the wound region. This study successfully developed an OHA-DA/PAM/BC multifunctional hydrogel characterized by exceptional stretchability, self-healing, adhesiveness, injectability and antibacterial activity, demonstrating a significant impact on wound healing in vivo. These findings indicated that the OHA-DA/PAM/BC hydrogel holds substantial potential as wound dressings for future clinical applications.

Initiatorless polymerization of mechanically robust hydrogels reinforced by cellulose of wood skeleton as multifunctional sensors

Wood-based hydrogel with a unique anisotropic structure is an attractive soft-and-wet material. However, it remains a challenge to simultaneously achieve robust, multi-functional, and multi-response integrations through a sustainable and green approach. Herein, a bioinspired, additive-free method is reported to fabricate composite hydrogels reinforced by naturally high-strength wood skeleton without using any chemical initiators and crosslinking agents. Specifically, polymers (Polyacrylamide/Polyacrylic acid) are grafted from the surfaces of the aligned cellulose of wood skeleton, forming wood-based hydrogels under UV irradiation. Afterward, Fe3+-mediated physical crosslinking is employed further to construct chemically crosslinked poly(acrylamide-co-acrylic acid) networks. Therefore, the resulting initiatorless wood-based hydrogel with a dual-crosslinked network structure exhibits an ultra-high tensile strength of 42 MPa along the longitudinal direction, representing one of the strongest hydrogels ever reported. Furthermore, the wood-based hydrogels with inherent conductive properties appealing versatile sensations on strain, temperature, and light, which could serve as human-motion monitors (detection), thermo-electrochemical sensors, underwater wearable sensors, and smart-home systems. This work offers a green and promising strategy to fabricate robust, anisotropic, flexible, and ionically conductive wood-based hydrogels for multifunctional sensors with excellent performance in complex environments.

Muscle-Inspired Self-Growing Anisotropic Hydrogels with Mechanical Training-Promoting Mechanical Properties

Muscles are highly anisotropic, force-bearing issues. They form via a process involving nutrient absorption for matrix growth and mechanical training for matrix toughening, in which cyclic disassembly-reconstruction of muscle fibers plays a critical role in generating strong anisotropic structures. Inspired by this process, a mechanical training-associated growing strategy is developed for preparing tough anisotropic hydrogels. Using anisotropic hydrogels made from polyvinyl alcohol (PVA)/tannic acid (TA) as an example, it is demonstrated that the hydrogels can absorb poly(ethylene glycol) diacrylate (PEGDA) via disassembling their aligned nanofibrillar structures. Incorporation of PEGDA within the hydrogels induces PVA to form crystal domains while subsequent mechanical training can restore the aligned fibrillar structures. Such a combining process results in expansion in materials' size (≈2 times) and significant enhancement in their mechanical properties (Young's modulus: from 2.4 to 2.85 MPa; ultimate tensile strength: from 8.2 to 14.1 MPa; toughness: from 335 to 465 MJ m-3). With a high energy dissipation efficiency (≈90%), potential applications for these tough and adaptable hydrogels are envisioned in impact-protective materials, surgical sutures, etc.

Facile Integration of Bacterial Cellulose with Liquid Crystal Elastomers Enables Robust Biomimetic Helical Yarn Actuators

Inspired from helical structures in nature, liquid crystal elastomer (LCE) fiber actuators are developed for soft robotics and smart wearables. However, the facile development of robust LCE yarn actuators remains challenging due to the lightly cross-linked networks of LCE with the inherently poor mechanical properties. Here, the bionic helical yarn actuator is constructed through integrating the shape-morphing LCE fiber as the actuation phase and the highly ordered orientation biomass bacterial cellulose (BC) macrofibers as the reinforcement phase by a facile twisting and two-step cross-linking strategy. Thanks to the 3D nanofiber network inside BC macrofibers and biomimetic helical structure, the mechanical strength (43.9 MPa) and the creep phenomenon of the resulted yarn have been significantly improved, which are obviously better than the reported LCE fiber actuators (1.4-30.8 MPa). The designed LCE/BC helical yarn actuators demonstrate high work capacity (304.1 J kg-1) and reliable reusability. As a proof-of-concept, this work constructs micro rolling device with customizable speed, soft gripper for grasping and moving heavy objects and passive micro motor with a speed of 7.7 rad s-1. The findings of this work are expected to provide insights into the development of high-performance and durable smart yarn actuators through biomimetic engineering strategies.

Bioinspired Programmable and Ultrastretchable Janus Helical Hydrogel Fibers for Strain-Invariant Thermoelectric Body Heat Harvesting and Sensation

Current fiber-based electronics often suffer from low stretchability and struggle to conform to complex and dynamic skin surfaces, resulting in significantly reduced performance in wearable devices. However, hydrogels with processability and adaptability permit conformity to diverse curved and uneven surfaces. Inspired by natural tendrils, we present Janus helical hydrogel fibers capable of completely maintaining the original thermoelectric performance under ultrahigh elastic strains. Janus helical fibers, composed of sodium polyacrylate (PANa) and PANa/single-walled carbon nanotube (PANa-SWCNT) hydrogels, are fabricated at scale and programmed with controllable diameters by utilizing the biological strain mismatch mechanism. The optimized fiber is ultrastretchable and has a master strain-invariant built-in temperature gradient as well as resistance, thus ensuring stable energy output even at 650% strain. The hydrogel fiber integrated with 90 pairs of p/n coils adaptively harvest heat, exhibiting a notable voltage density of 6.51 mV cm-2, and accurately perceive environmental temperatures (-176 μV/°C) undisturbed by body movements.

Compressible, anti-fatigue, extreme environment adaptable, and biocompatible supramolecular organohydrogel enabled by lignosulfonate triggered noncovalent network

Achieving a synergy of biocompatibility and extreme environmental adaptability with excellent mechanical property remains challenging in the development of synthetic materials. Herein, a "bottom-up" solution-interface-induced self-assembly strategy is adopted to develop a compressible, anti-fatigue, extreme environment adaptable, biocompatible, and recyclable organohydrogel composed of chitosan-lignosulfonate-gelatin by constructing noncovalent bonded conjoined network. The ethylene glycol/water solvent induced lignosulfonate nanoparticles function as bridge in chitosan/gelation network, forming multiple interfacial interactions that can effectively dissipate energy. The organohydrogel exhibits high compressive strength (54 MPa) and toughness (3.54 MJ/m3), 100 and 70 times higher than those of pure chitosan/gelatin hydrogel, meanwhile, excellent self-recovery and fatigue resistance properties. Even when subjected to severe compression up to a strain of 0.5 for 500,000 cycles, the organohydrogel still remains intact. This organohydrogel also demonstrates notable biocompatibility both in vivo and vitro, environment adaptability at low temperature, as well as recyclability. Such all natural organohydrogel provides a promising route towards the development of high-performance load-bearing materials.

Fluorescent alginate fiber with super-strong and super-tough mechanical performances for biomedical applications

Emerging research attentions are focused on the development of fluorescent biomaterials for various biomedical applications, including fluorescence-guided surgery. However, it is still challenging to prepare biomolecules-based fluorescent fibers with both satisfactory biocompatibility and optimal mechanical properties. Here, we develop a fluorescent robust biofiber through using a tetraphenylethene-containing surfactant as the contact points between polysaccharide chains of alginate. This newly developed contact points not only strengthen the cross-linking network of polysaccharide chains, but also afford enough energy-dissipating slippage for polysaccharide chains. Consequently, the generated fluorescent fiber is endowed with highly improved mechanical performances from plastic strain stage. The experimental results indicate that the fluorescent fiber shows good mechanical properties of breaking strength of 1.10 GPa (12.09 cN/dtex), Young's modulus of 39.81 GPa and toughness of 137.26 MJ/m3, which are comparable to those of dragline silk and outperforming spider silk proteins and other artificial materials. More importantly, its satisfactory biosafety and wound healing-promoting ability as a fluorescent suture are solidly proved by both in vitro and in vivo assays, which opens an opportunity for its biological and biomedical applications. This study provides a novel strategy for the development of robust fluorescent biomaterials.

Emerging Sustainable Structural Materials by Assembling Cellulose Nanofibers

Under the guidance of the carbon peaking and carbon neutrality goals, the urgency for green ecological construction and the depletion of nonrenewable resources highlight the importance of the research and development of sustainable new materials. Cellulose nanofiber (CNF) is the most abundant natural nanoscale building block widely existing on Earth. CNF has unique intrinsic physical properties, such as low density, low coefficient of thermal expansion, high strength, and high modulus, which is an ideal candidate with outstanding potential for constructing sustainable materials. In recent years, CNF-based structural material has emerged as a sustainable lightweight material with properties very different from traditional structural materials. Here, to comprehensively introduce the assembly of structural materials based on CNF, it starts with an overview of different forms of CNF-based materials, including fibers, films, hydrogels, aerogels, and structural materials. Next, the challenges that need to be overcome in preparing CNF-based structural materials are discussed, their assembly methods are introduced, and an in-depth analysis of the advantages of the CNF-based hydrogel assembly strategy to fabricate structural materials is conducted. Finally, the unique properties of emerging CNF-based structural materials are summarized and concluded with an outlook on their design and functionalization, potentially paving the way toward new opportunities.

Super-Strong, Super-Stiff, and Super-Tough Fluorescent Alginate Fibers with Outstanding Tolerance to Extreme Conditions

The combination of multiple physical properties is of great importance for widening the application scenarios of biomaterials. It remains a great challenge to fabricate biomolecules-based fibers gaining both mechanical strength and toughness which are comparable to natural spider dragline silks. Here, by mimicking the structure of dragline silks, a high-performance fluorescent fiber Alg-TPEA-PEG is designed by non-covalently cross-linking the polysaccharide chains of alginate with AIEgen-based surfactant molecules as the flexible contact points. The non-covalent cross-linking network provides sufficient energy-dissipating slippage between polysaccharide chains, leading to Alg-TPEA-PEG with highly improved mechanical performances from the plastic strain stage. By successfully transferring the extraordinary mechanical performances of polysaccharide chains to macroscopic fibers, Alg-TPEA-PEG exhibits an outstanding breaking strength of 1.27 GPa, Young's modulus of 34.13 GPa, and toughness of 150.48 MJ m-3, which are comparable to those of dragline silk and outperforming other artificial materials. More importantly, both fluorescent and mechanical properties of Alg-TPEA-PEG can be well preserved under various harsh conditions, and the fluorescence and biocompatibility facilitate its biological and biomedical applications. This study affords a new biomimetic designing strategy for gaining super-strong, super-stiff, and super-tough fluorescent biomaterials.

Three-Dimensional Hierarchical Cellulose Structures Based on Microbial Synthesis and Advanced Biofabrication

Cellulose is the most abundant and important biopolymer in our world, and it can also be biosynthesized by certain types of bacteria, such as Komagataeibacter xylinus. However, due to the requirement of oxygen access during such bacterial cellulose (BC) biosynthesis, as well as the high crystallinity and poor processability of BC, it is very challenging to fabricate 3D BC structures with well-defined shape, geometry, and internal structure. In recent years, the rapid progress of polymer additive manufacturing and biofabrication has provided new and versatile approaches for fabricating hierarchical 3D cellulose structures. This can be achieved by either incorporating BC in the 3D printing feedstock or, more interestingly, by incorporating cellulose-generating bacteria in a living ink followed by in situ BC biosynthesis. In this Perspective, we critically examine the potential of various advanced biofabrication technologies in fabricating hierarchical 3D cellulose structures, especially those based on integrating additive manufacturing with in situ microbial biosynthesis. Moreover, sustainable biocomposites based on BC and microbial biosynthesis are also discussed. The current challenges and future opportunities of microbial-biosynthesis-enabled 3D cellulose structures are highlighted. Their applications in tissue engineering, drug delivery, lightweight composites, thermal management, and energy storage are also discussed.

Applied research and recent advances in the development of flexible sensing hydrogels from cellulose: A review

Flexible wearable smart sensing materials have gained immense momentum, and biomass-based hydrogel sensors for renewable and biologically safe wearable sensors have attracted significant attention in order to meet the growing demand for sustainability and ecological friendliness. Cellulose has been widely used in the field of biomass-based hydrogel sensing materials, being the most abundant biomass material in nature. This review mainly focuses on the types of cellulose hydrogels, the preparation methods and their applications in smart flexible sensing materials. The structure-functional properties-application relationship of cellulose hydrogels and the applications of various cellulose hydrogels in flexible sensing are described in detail. Then it focuses on the methods and mechanisms of cellulose hydrogel flexible sensors preparation, and then summarizes the research of cellulose hydrogel sensors for different types of stimulus response mechanisms to pressure, pH, biomolecules, ions, temperature, humidity, and light. The applications of cellulose hydrogels as flexible sensing materials in biomedical sensing, smart wearable and environmental monitoring are further summarized. Finally, the future development trend of cellulose hydrogels is briefly introduced and the future development of cellulose hydrogel sensing materials is envisioned.

Development of Biomaterials to Modulate the Function of Macrophages in Wound Healing

Wound healing is a complex and precisely regulated process that encompasses multiple stages, including inflammation, anti-inflammation, and tissue repair. It involves various cells and signaling molecules, with macrophages demonstrating a significant degree of plasticity and playing a crucial regulatory role at different stages. In recent years, the use of biomaterials, which include both natural and synthetic polymers or macromolecules, has proliferated for the purpose of enhancing wound healing. This review summarizes how these diverse biomaterials promote wound healing by modulating macrophage behavior and examines the broader implications of these modulations. Additionally, we discuss the limitations associated with the clinical application of immunomodulatory biomaterials and propose potential solutions. Finally, we look towards future developments in the design of immunomodulatory biomaterials intended to enhance wound healing.

Highly-Strong and Highly-Tough Alginate Fibers with Photo-Modulating Mechanical Properties

The good combination of high strength and high toughness is a long-standing challenge in the design of robust biomaterials. Meanwhile, robust biomaterials hardly perform fast and significant mechanical property changes under the trigger of light at room temperature. These limit the application of biomaterials in some specific areas. Here, photoresponsive alginate fibers are fabricated by using the designed azobenzene-containing surfactant as flexible contact point for cross-linking polysaccharide chains of alginate, which gain high mechanics through reinforced plastic strain and photo-modulating mechanics through isomerization of azobenzene. By transferring molecular motion into macro-scale mechanical property changes, such alginate fibers achieve reversible photo-modulations on the mechanics. Their breaking strength and toughness can be photo-modulated from 732 MPa and 112 MJ m-3 to 299 MPa and 27 MJ m-3, respectively, leading to record high mechanical changes among the developed smart biomaterials. With merits of good tolerance to pH and temperature, fast response to light, and good biocompatibility, the reported fibers will be suitable for working in various application scenarios as new smart biomaterials. This study provides a new design strategy for gaining highly-strong and highly-tough photoresponsive biomaterials.

Enhancement of Visible Light Antibacterial Activities of Cellulose Fibers from Lotus Petiole Decorated ZnO Nanoparticles

Cellulose/ZnO (CZ) nanocomposites are promising antimicrobial materials known for their antibiotic-free nature, biocompatibility, and environmental friendliness. In this study, cellulose fibers extracted from lotus petioles were utilized as a substrate and decorated with various shapes of ZnO nanoparticles (NPs), including small bean, hexagonal ingot-like, long cylindrical, and hexagonal cylinder-shaped NPs. Increasing zinc salt molar concentration resulted in highly crystalline ZnO NPs forming and enhanced interactions between ZnO NPs and -OH groups of cellulose. The thermal stability and UV-visible absorption properties of the CZ samples were influenced by ZnO concentration. Notably, at a ZnO molar ratio of 0.1, the CZ 0.1 sample demonstrated the lowest weight loss, while the optical band gap gradually decreased from 3.0 to 2.45 eV from the CZ 0.01 to CZ 1.0 samples. The CZ nanocomposites exhibited remarkable antibacterial activity against both Staphylococcus aureus (S. aureus, Gram-positive) and Escherichia coli (E. coli, Gram-negative) bacteria under visible light conditions, with a minimum inhibitory concentration (MIC) of 0.005 mg/mL for both bacterial strains. The bactericidal effects increased with higher concentrations of ZnO NPs, even achieving 100% inhibition. Incorporating ZnO NPs onto cellulose fibers derived from lotus plants presents a promising avenue for developing environmentally friendly materials with broad applications in antibacterial and environmental fields.

Room Temperature Phosphorescent Nanofiber Membranes by Bio-Fermentation

Stimuli-responsive materials exhibiting exceptional room temperature phosphorescence (RTP) hold promise for emerging technologies. However, constructing such systems in a sustainable, scalable, and processable manner remains challenging. This work reports a bio-inspired strategy to develop RTP nanofiber materials using bacterial cellulose (BC) via bio-fermentation. The green fabrication process, high biocompatibility, non-toxicity, and abundant hydroxyl groups make BC an ideal biopolymer for constructing durable and stimuli-responsive RTP materials. Remarkable RTP performance is observed with long lifetimes of up to 1636.79 ms at room temperature. Moreover, moisture can repeatedly quench and activate phosphorescence in a dynamic and tunable fashion by disrupting cellulose rigidity and permeability. With capabilities for repeatable moisture-sensitive phosphorescence, these materials are highly suitable for applications such as anti-counterfeiting and information encryption. This pioneering bio-derived approach provides a reliable and sustainable blueprint for constructing dynamic, scalable, and processable RTP materials beyond synthetic polymers.

Controlled Structural Relaxation of Aramid Nanofibers for Superstretchable Polymer Fibers with High Toughness and Heat Resistance

Polymer fibers that combine high toughness and heat resistance are hard to achieve, which, however, hold tremendous promise in demanding applications such as aerospace and military. This prohibitive design task exists due to the opposing property dependencies on chain dynamics because traditional heat-resistant materials with rigid molecular structures typically lack the mechanism of energy dissipation. Aramid nanofibers have received great attention as high-performance nanoscale building units due to their intriguing mechanical and thermal properties, but their distinct structural features are yet to be fully captured. We show that aramid nanofibers form nanoscale crimps during the removal of water, which primarily resides at the defect planes of pleated sheets, where the folding can occur. The precise control of such a structural relaxation can be realized by exerting axial loadings on hydrogel fibers, which allows the emergence of aramid fibers with varying angles of crimps. These crimped fibers integrate high toughness with heat resistance, thanks to the extensible nature of nanoscale crimps with rigid molecular structures of poly(p-phenylene terephthalamide), promising as a template for stable stretchable electronics. The tensile strength/modulus (392-944 MPa/11-29 GPa), stretchability (25-163%), and toughness (154-445 MJ/cm3) are achieved according to the degree of crimping. Intriguingly, a toughness of around 430 MJ/m3 can be maintained after calcination below the relaxation temperature (259 °C) for 50 h. Even after calcination at 300 °C for 10 h, a toughness of 310 MJ/m3 is kept, outperforming existing polymer materials. Our multiscale design strategy based on water-bearing aramid nanofibers provides a potent pathway for tackling the challenge for achieving conflicting property combinations.

Advances in Hydrogels of Drug Delivery Systems for the Local Treatment of Brain Tumors

The management of brain tumors presents numerous challenges, despite the employment of multimodal therapies including surgical intervention, radiotherapy, chemotherapy, and immunotherapy. Owing to the distinct location of brain tumors and the presence of the blood-brain barrier (BBB), these tumors exhibit considerable heterogeneity and invasiveness at the histological level. Recent advancements in hydrogel research for the local treatment of brain tumors have sought to overcome the primary challenge of delivering therapeutics past the BBB, thereby ensuring efficient accumulation within brain tumor tissues. This article elaborates on various hydrogel-based delivery vectors, examining their efficacy in the local treatment of brain tumors. Additionally, it reviews the fundamental principles involved in designing intelligent hydrogels that can circumvent the BBB and penetrate larger tumor areas, thereby facilitating precise, controlled drug release. Hydrogel-based drug delivery systems (DDSs) are posited to offer a groundbreaking approach to addressing the challenges and limitations inherent in traditional oncological therapies, which are significantly impeded by the unique structural and pathological characteristics of brain tumors.

Non-destructive strategy to extract sustainable helix and high-strength Musa core fibers for rapid water conduction and evaporation

The reuse and development of natural waste resources is a hotspots and challenges in the research of new fiber materials and the resolution of environmental concern globally. Herein, this study aimed to develop a simple and direct manual extraction process to extract Musa core fibers (MCFs) for rapid water conduction and evaporation. Through simple processes such as ring cutting and stretching, this green and non-destructive inside-out extraction strategy enabled Musa fibers to be naturally and harmlessly degummed from natural Musa stems, with good maintenance of the fiber structure and highly helical morphology. The extracted fibers are composed of regularly and closely arranged cellulose nanofibrils in the shape of ribbon spirally arranged multi-filaments, and the single filament is about 2.65 μm. The high-purity fibers exhibit ultra-high tensile strength under a non-destructive extraction process, and the ultimate tensile strength in dry state is as high as 742.95 MPa. The tensile strength is affected by the number of fiber bundles, which shows that tensile strength and tensile modulus is higher than those of vascular bundle fibers in dry or wet condition. In addition, the MCFs membrane indicates good water conductivity, with a water absorption height of 50 mm for the sample in only 60 s. Moreover, the water evaporation rate of MCFs reaches 1.37 kg m-2 h-1 in 30 min, which shows that MCFs have excellent water conductivity and evaporation rate compared with ordinary cotton fibers. These results indicate that MCFs have great potential in replacing the use of chemical methods to extract fibers from vascular bundles, providing an effective way to achieve sustainability in quick-drying applications, as well as in the sustainable development of natural waste resources.

Spider-silk-inspired strong and tough hydrogel fibers with anti-freezing and water retention properties

Ideal hydrogel fibers with high toughness and environmental tolerance are indispensable for their long-term application in flexible electronics as actuating and sensing elements. However, current hydrogel fibers exhibit poor mechanical properties and environmental instability due to their intrinsically weak molecular (chain) interactions. Inspired by the multilevel adjustment of spider silk network structure by ions, bionic hydrogel fibers with elaborated ionic crosslinking and crystalline domains are constructed. Bionic hydrogel fibers show a toughness of 162.25 ± 21.99 megajoules per cubic meter, comparable to that of spider silks. The demonstrated bionic structural engineering strategy can be generalized to other polymers and inorganic salts for fabricating hydrogel fibers with broadly tunable mechanical properties. In addition, the introduction of inorganic salt/glycerol/water ternary solvent during constructing bionic structures endows hydrogel fibers with anti-freezing, water retention, and self-regeneration properties. This work provides ideas to fabricate hydrogel fibers with high mechanical properties and stability for flexible electronics.

Bioinspired Supramolecular Hydrogel from Design to Applications

Nature offers a wealth of opportunities to solve scientific and technological issues based on its unique structures and function. The dynamic non-covalent interaction is considered to be the main base of living functions of creatures including humans, animals, and plants. Supramolecular hydrogels formed by non-covalent bonding interactions has become a unique platform for constructing promising materials for medicine, energy, electronic, and biological substitute. In this review, the self-assemble principle of supramolecular hydrogels is summarized. Next, the stimulation of external environment that triggers the assembly or disassembly of supramolecular hydrogels are recapitulated, including temperature, mechanics, light, pH, ions, etc. The main applications of bioinspired supramolecular hydrogels in terms of bionic objects including humans, animals, and plants are also described. Although so many efforts are done for revealing the synergized mechanism of the function and non-covalent interactions on the supramolecular hydrogel, the complexity and variability between stimulus and non-covalent bonding in the supramolecular system still require impeccable theories. As an outlook, the bioinspired supramolecular hydrogel is just beginning to exhibit its great potential in human life, offering significant opportunities in drug delivery and screening, implantable devices and substitutions, tissue engineering, micro-fluidic devices, and biosensors.

Advancements in hydrogel-based drug delivery systems for the treatment of inflammatory bowel disease: a review

Inflammatory bowel disease (IBD) is a chronic disorder that affects millions of individuals worldwide. However, current drug therapies for IBD are plagued by significant side effects, low efficacy, and poor patient compliance. Consequently, there is an urgent need for novel therapeutic approaches to alleviate IBD. Hydrogels, three-dimensional networks of hydrophilic polymers with the ability to swell and retain water, have emerged as promising materials for drug delivery in the treatment of IBD due to their biocompatibility, tunability, and responsiveness to various stimuli. In this review, we summarize recent advancements in hydrogel-based drug delivery systems for the treatment of IBD. We first identify three pathophysiological alterations that need to be addressed in the current treatment of IBD: damage to the intestinal mucosal barrier, dysbiosis of intestinal flora, and activation of inflammatory signaling pathways leading to disequilibrium within the intestines. Subsequently, we discuss in depth the processes required to prepare hydrogel drug delivery systems, from the selection of hydrogel materials, types of drugs to be loaded, methods of drug loading and drug release mechanisms to key points in the preparation of hydrogel drug delivery systems. Additionally, we highlight the progress and impact of the hydrogel-based drug delivery system in IBD treatment through regulation of physical barrier immune responses, promotion of mucosal repair, and improvement of gut microbiota. In conclusion, we analyze the challenges of hydrogel-based drug delivery systems in clinical applications for IBD treatment, and propose potential solutions from our perspective.

Robust integration of light-driven carbon quantum dots with bacterial cellulose enables excellent mechanical and antibacterial biodegradable yarn

Due to the overuse of antimicrobial drugs, bacterial resistance became an urgent problem to be solved. In this study, carbon quantum dots (CQDs) with high photodynamic antibacterial activity were synthesized by a one-pot hydrothermal method and introduced into bacterial cellulose (BC) dispersion solution. Through a wet-spinning and wet-twisting processing strategy, bionic ordering nanocomposite macrofiber (BC/CQDs-based yarn) based on BC were obtained. The results showed that BC/CQDs-based yarn had excellent tensile strength (226.8 MPa) and elongation (22.2 %). Utilizing the light-driven generation of singlet oxygen (1O2) and hydroxyl radical (·OH), BC/CQDs-based yarn demonstrated remarkable antibacterial efficacy, with 99.9999 % (6 log, P < 0.0001) and 96.54 % (1.46 log, P < 0.0004) effectiveness against E. coli and S. aureus, respectively. At the same time, BC/CQDs-based yarn also displayed the characteristics of photothermal, fluorescent, and biodegradability. In summary, the application potential of BC/CQDs-based yarn is significant, opening up a new strategy for the development of sustainable green weaving and bio-based multi-function yarn.

Two way workable microchanneled hydrogel suture to diagnose, treat and monitor the infarcted heart

During myocardial infarction, microcirculation disturbance in the ischemic area can cause necrosis and formation of fibrotic tissue, potentially leading to malignant arrhythmia and myocardial remodeling. Here, we report a microchanneled hydrogel suture for two-way signal communication, pumping drugs on demand, and cardiac repair. After myocardial infarction, our hydrogel suture monitors abnormal electrocardiogram through the mobile device and triggers nitric oxide on demand via the hydrogel sutures' microchannels, thereby inhibiting inflammation, promoting microvascular remodeling, and improving the left ventricular ejection fraction in rats and minipigs by more than 60% and 50%, respectively. This work proposes a suture for bidirectional communication that acts as a cardio-patch to repair myocardial infarction, that remotely monitors the heart, and can deliver drugs on demand.

Light-Emitting Microfibers from Lotus Root for Eco-Friendly Optical Waveguides and Biosensing

Optical biosensors based on micro/nanofibers are highly valuable for probing and monitoring liquid environments and bioactivity. Most current optical biosensors, however, are still based on glass, semiconductors, or metallic materials, which might not be fully suitable for biologically relevant environments. Here, we introduce biocompatible and flexible microfibers from lotus silk as microenvironmental monitors that exhibit waveguiding of intrinsic fluorescence as well as of coupled light. These features make single-filament monitors excellent building blocks for a variety of sensing functions, including pH probing and detection of bacterial activity. These results pave the way for the development of new and entirely eco-friendly, potentially multiplexed biosensing platforms.

Fiber-Based Noncontact Sensor with Stretchability for Underwater Wearable Sensing and VR Applications

The rapid development of artificial intelligent wearable devices has led to an increasing need for seamless information exchange between humans, machines, and virtual spaces, often relying on touch sensors as the primary interaction medium. Additionally, the demand for underwater detection technologies is on the rise owing to the prevalent wet and submerged environment. Here, a fiber-based capacitive sensor with superior stretchability and hydrophobicity is proposed, designed to cater to noncontact and underwater applications. The sensor is constructed using bacterial cellulose (BC)@BC/carbon nanotubes (CNTs) (BBT) helical fiber as the matrix and methyltrimethoxysilane (MTMS) as the hydrophobic modified agent, forming a hydrophobic silylated BC@BC/CNT (SBBT) helical fiber by the chemical vapor deposition (CVD) technique. These fibers exhibit an impressive contact angle of 132.8°. The SBBT helicalfiber-based capacitive sensor presents capabilities for both noncontact and underwater sensing, which exhibits a significant capacitance change of -0.27 (at a distance of 0.5 cm). We have achieved interactive control between real space and virtual space through intelligent data analysis technology with minimal interference from the presence of water. This work has laid a solid foundation of noncontact sensing with attributes such as degradability, stretchability, and hydrophobicity. Moreover, it offers promising solutions for barrier-free communication in virtual reality (VR) and underwater applications, providing avenues for smart human-machine interfaces for submerged use.

Review on design strategies and applications of flexible cellulose‑carbon nanotube functional composites

Combining the excellent biocompatibility and mechanical flexibility of cellulose with the outstanding electrical, mechanical, optical and stability properties of carbon nanotubes (CNTs), cellulose-CNT composites have been extensively studied and applied to many flexible functional materials. In this review, we present advances in structural design strategies and various applications of cellulose-CNT composites. Firstly, the structural characteristics and corresponding treatments of cellulose and CNTs are analyzed, as are the potential interactions between the two to facilitate the formation of cellulose-CNT composites. Then, the design strategies and processing techniques of cellulose-CNT composites are discussed from the perspectives of cellulose fibers at the macroscopic scale (natural cotton, hemp, and other fibers; recycled cellulose fibers); nanocellulose at the micron scale (nanofibers, nanocrystals, etc.); and macromolecular chains at the molecular scale (cellulose solutions). Further, the applications of cellulose-CNT composites in various fields, such as flexible energy harvesting and storage devices, strain and humidity sensors, electrothermal devices, magnetic shielding, and photothermal conversion, are introduced. This review will help readers understand the design strategies of cellulose-CNT composites and develop potential high-performance applications.

Cellulose Dissolution, Modification, and the Derived Hydrogel: A Review

The cellulose-based hydrogel has occupied a pivotal position in almost all walks of life. However, the native cellulose can not be directly used for preparing hydrogel due to the complex non-covalent interactions. Some literature has discussed the dissolution and modification of cellulose but has yet to address the influence of the pretreatment on the as-prepared hydrogels. Firstly, the "touching" of cellulose by derived and non-derived solvents was introduced, namely, the dissolution of cellulose. Secondly, the "conversion" of functional groups on the cellulose surface by special routes, which is the modification of cellulose. The above-mentioned two parts were intended to explain the changes in physicochemical properties of cellulose by these routes and their influences on the subsequent hydrogel preparation. Finally, the "reinforcement" of cellulose-based hydrogels by physical and chemical techniques was summarized, viz., improving the mechanical properties of cellulose-based hydrogels and the changes in the multi-level structure of the interior of cellulose-based hydrogels.

Platelet-Rich Plasma Composite Organohydrogel with Water-Locking and Anti-Freezing to Accelerate Wound Healing

Hydrogels have gained impressive attention in biological medicine due to their excellent biosafety, softness, and varied functional components. However, conventional hydrogels have inherent defects, such as low tensile strength, weak water-locking, and poor anti-freezing. In tissue engineering, once the hydrogel loses water or freezes, it will harden the interaction interfaces and destroy the nascent granulation tissue. Herein, based on the design concept of "hard frame-soft penetration", a composite adhesive organohydrogel is fabricated by introducing bacterial cellulose and platelet-rich plasma (PRP) into a poly-N-(tris[hydroxymethyl]methyl)acrylamide (THMA)/N-acryloyl aspartic acid (AASP) hybrid gel network infiltrated with glycerol/water binary solvent. The resultant organohydrogels exhibit excellent antifreeze properties at low temperatures (-80 °C) and demonstrate stable long-term water retention (91%) in the open environment within 12 days and can adhere firmly to the tissues by the action of "hydrogen bond clusters". Additionally, the introduction of bacterial cellulose matrix endows the organohydrogel with high tensile strength similar to that of skin. In vivo, the PRP-loaded organohydrogel can release a variety of growth factors to accelerate the wound healing process through collagen deposition and angiogenesis. Altogether, this strategy will extend the life of the hydrogel in some harsh medical environments.

Bionic ordered structured hydrogels: structure types, design strategies, optimization mechanism of mechanical properties and applications

Natural organisms, such as lobsters, lotus, and humans, exhibit exceptional mechanical properties due to their ordered structures. However, traditional hydrogels have limitations in their mechanical and physical properties due to their disordered molecular structures when compared with natural organisms. Therefore, inspired by nature and the properties of hydrogels similar to those of biological soft tissues, researchers are increasingly focusing on how to investigate bionic ordered structured hydrogels and render them as bioengineering soft materials with unique mechanical properties. In this paper, we systematically introduce the various structure types, design strategies, and optimization mechanisms used to enhance the strength, toughness, and anti-fatigue properties of bionic ordered structured hydrogels in recent years. We further review the potential applications of bionic ordered structured hydrogels in various fields, including sensors, bioremediation materials, actuators, and impact-resistant materials. Finally, we summarize the challenges and future development prospects of bionic ordered structured hydrogels in preparation and applications.

Bioinspired, Robust, and Absorbable Cellulose Nanofibrils/Chitosan Filament with Remarkable Cytocompatibility and Wound Healing Properties

Surgical threads are of great importance to prevent wound infection and accelerate tissue healing in surgical treatment. Cellulose nanofibrils (CNF) and chitosan (CS) are attracting increasing attention to be employed as biomedicine materials due to their nontoxicity, cytocompatibility, and biodegradability. However, a robust and absorbable cellulose-based surgical thread has not been explored. Therefore, in this work, a bioinspired CNF/CS composite thread containing 5% cationic polyacrylamide (CPAM) by the mass of CS was prepared, and the obtained CNF/CS-5C thread exhibited excellent mechanical properties and low swelling ratio in water due to the high cross-link degree. Especially, the tensile strength (1877 ± 107 MPa) of this thread was much higher than that of most reported CNF-based threads. Meanwhile, compared with commercial silk and Vicryl surgical threads, the CNF/CS-5C thread exhibited better in vitro cytocompatibility toward endothelial and fibroblast cells and lower inflammatory response in vivo to subcutaneous tissues of rats. In addition, the obtained thread could be regarded as a promising absorbable suture, which exhibited excellent wound healing performances in vivo. Therefore, the prepared absorbable thread will open a new window to prepare novel and advanced cellulose-based threads for medical applications.

Recent advances in bacterial cellulose-based antibacterial composites for infected wound therapy

Wound infection arising from pathogenic bacteria brought serious trouble to the patient and medical system. Among various wound dressings that are effective in killing pathogenic bacteria, antimicrobial composites based on bacterial cellulose (BC) are becoming the most popular materials due to their success in eliminating pathogenic bacteria, preventing wound infection, and promoting wound healing. However, as an extracellular natural polymer, BC is not inherently antimicrobial, which means that it must be combined with other antimicrobials to be effective against pathogens. BC has many advantages over other polymers, including nano-structure, significant moisture retention, non-adhesion to the wound surface, which has made it superior to other biopolymers. This review introduces the recent advances in BC-based composites for the treatment of wound infection, including the classification and preparation methods of composites, the mechanism of wound treatment, and commercial application. Moreover, their wound therapy applications include hydrogel dressing, surgical sutures, wound healing bandages, and patches are summarized in detail. Finally, the challenges and future prospects of BC-based antibacterial composites for the treatment of infected wounds are discussed.

Advances, challenges, and prospects for surgical suture materials

As one of the long-established and necessary medical devices, surgical sutures play an essentially important role in the closing and healing of damaged tissues and organs postoperatively. The recent advances in multiple disciplines, like materials science, engineering technology, and biomedicine, have facilitated the generation of various innovative surgical sutures with humanization and multi-functionalization. For instance, the application of numerous absorbable materials is assuredly a marvelous progression in terms of surgical sutures. Moreover, some fantastic results from recent laboratory research cannot be ignored either, ranging from the fiber generation to the suture structure, as well as the suture modification, functionalization, and even intellectualization. In this review, the suture materials, including natural or synthetic polymers, absorbable or non-absorbable polymers, and metal materials, were first introduced, and then their advantages and disadvantages were summarized. Then we introduced and discussed various fiber fabrication strategies for the production of surgical sutures. Noticeably, advanced nanofiber generation strategies were highlighted. This review further summarized a wide and diverse variety of suture structures and further discussed their different features. After that, we covered the advanced design and development of surgical sutures with multiple functionalizations, which mainly included surface coating technologies and direct drug-loading technologies. Meanwhile, the review highlighted some smart and intelligent sutures that can monitor the wound status in a real-time manner and provide on-demand therapies accordingly. Furthermore, some representative commercial sutures were also introduced and summarized. At the end of this review, we discussed the challenges and future prospects in the field of surgical sutures in depth. This review aims to provide a meaningful reference and guidance for the future design and fabrication of innovative surgical sutures. STATEMENT OF SIGNIFICANCE: This review article introduces the recent advances of surgical sutures, including material selection, fiber morphology, suture structure and construction, as well as suture modification, functionalization, and even intellectualization. Importantly, some innovative strategies for the construction of multifunctional sutures with predetermined biological properties are highlighted. Moreover, some important commercial suture products are systematically summarized and compared. This review also discusses the challenges and future prospects of advanced sutures in a deep manner. In all, this review is expected to arouse great interest from a broad group of readers in the fields of multifunctional biomaterials and regenerative medicine.

Photothermal effective CeO2NPs combined in thermosensitive hydrogels with enhanced antibacterial, antioxidant and vascularization performance to accelerate infected diabetic wound healing

Chronic diabetic wound healing remains a formidable challenge due to susceptibility to bacterial infection, excessive oxidative stress, and poor angiogenesis. To address these issues, a sodium alginate (SA) based photothermal hydrogel dressing with multifunction was fabricated to facilitate wound treatment. Ceria nanoparticles (CeO2NPs) was synthesized, and their antibacterial performance by near-infrared light triggered photothermal effects was first studied and verified in this work. In addition, to release CeO2NPs to achieve antioxidation and pro-vascularization, thermosensitive gelatin (Gel) was utilized to embed the nanoparticles in advance and then composited in SA hydrogel networks. SA network was finally strengthened by acid soaking to form partially crystalline regions to act as natural crosslinkers. Results showed that the Gel/SA/CeO2 hydrogel displayed temperature-responsive release of CeO2NPs, significant antibacterial and antioxidative activity, as well as the ability to remove without injury and promote infected diabetic wound healing with low cytotoxicity, according to antibacterial investigations, cell studies, and in vivo animal studies. This research offers not only a successful method for quickening the healing of diabetic wounds but also a fresh approach to the general use of CeO2NPs.

Fabrication of a textile-based triboelectric nanogenerator toward high-efficiency energy harvesting and material recognition

Textile-based triboelectric nanogenerator (T-TENG) devices, particularly, narrow-gap mode, have been conceived and developed for obtaining energy harvesting and tactile sensing devices unaffected by the external environment. Enhancing the interfacial area of T-TENG materials offers exciting opportunities to improve the device output performance. In this work, a narrow-gap T-TENG was fabricated with a facile process, and a new strategy for improving the device output is proposed. The new structural sensor (polydimethylsiloxane (PDMS)-encapsulated electroless copper plating (EP-Cu) cotton) with multiple electricity generation mechanism was designed and fabricated for enhancing recognition accuracy. The result shows that only PDMS layer strain was established at an external stress of 1.24-12.4 kPa and the fibers laterally slip at a stress of 12.4-139 kPa; more importantly, the output performance of the TENG displayed a linear relationship under corresponding stress ranges. The as-fabricated device demonstrated the ability to convert different energies such as vibration, raindrops, wind and human motions into electrical energy with excellent sensitivity. Interestingly, the output signal of the as-fabricated TENG device is a combination of output signals from PDMS/EP-Cu and PDMS/recognition object devices. To be precise, there are two TENG devices (PDMS/EP-Cu and PDMS/recognition object) that work when the as-fabricated TENG device is under 12.4-139 kPa stress. Accompanied by unique characteristics, the generated TENG signals are capable of recognition of contact materials. Combining the TENG signal and deep learning technology, we explore a strategy that can enable the as-fabricated device to recognize 8 different materials with 99.48% recognition accuracy in the natural environment.

Hydrogel fibers for wearable sensors and soft actuators

Owing to superior softness, wetness, responsiveness, and biocompatibility, bulk hydrogels are being intensively investigated for versatile functions in devices and machines including sensors, actuators, optics, and coatings. The one-dimensional (1D) hydrogel fibers possess the metrics from both the hydrogel materials and structural topology, endowing them with extraordinary mechanical, sensing, breathable and weavable properties. As no comprehensive review has been reported for this nascent field, this article aims to provide an overview of hydrogel fibers for soft electronics and actuators. We first introduce the basic properties and measurement methods of hydrogel fibers, including mechanical, electrical, adhesive, and biocompatible properties. Then, typical manufacturing methods for 1D hydrogel fibers and fibrous films are discussed. Next, the recent progress of wearable sensors (e.g., strain, temperature, pH, and humidity) and actuators made from hydrogel fibers is discussed. We conclude with future perspectives on next-generation hydrogel fibers and the remaining challenges. The development of hydrogel fibers will not only provide an unparalleled one-dimensional characteristic, but also translate fundamental understanding of hydrogels into new application boundaries.

The biosynthesis of amidated bacterial cellulose derivatives via in-situ strategy

Bacterial cellulose, as a kind of natural biopolymer produced by bacterial fermentation, has attracted wide attention owing its unique physical and chemical properties. Nevertheless, the single functional group on the surface of BC greatly hinders its wider application. The functionalization of BC is of great significance to broaden the application of BC. In this work, N-acetylated bacterial cellulose (ABC) was successfully prepared using K. nataicola RZS01-based direct synthetic method. FT-IR, NMR and XPS confirmed the in-situ modification of BC by acetylation. The SEM and XRD results demonstrated that ABC has a lower crystallinity and higher fiber width compare with pristine 88 BCE % cell viability on NIH-3 T3 cell and near zero hemolysis ratio indicate its good biocompatibility. In addition, the as-prepared acetyl amine modified BC was further treated by nitrifying bacteria to enrich its functionalized diversity. This study provides a mild in-situ pathway to construct BC derivatives in an environmentally friendly way during its metabolism.

Tough, Recyclable, and Degradable Elastomers for Potential Biomedical Applications

Elastomers have many industrial, medical and commercial applications, however, their huge demand raises an important question of how to dispose of the out-of-service elastomers. Ideal elastomers that are concurrently tough, recyclable, and degradable are in urgent need, but their preparation remains a rigorous challenge. Herein, a polycaprolactone (PCL) based polyurethane elastomer is designed and prepared to meet this demand. Owing to the presence of dynamic coordination bond and the occurrence of strain-induced crystallization, the obtained elastomer exhibits a high toughness of ≈372 MJ m^-3 and an unprecedented fracture energy of ≈646 kJ m^-2 , which is much higher than natural rubber (≈50 MJ m^-3 for toughness and ≈10 kJ m^-2 for fracture energy). In addition, the elastomer can be recycled at least three times using solvent without losing its mechanical properties and can be degraded by lipase in ≈2 months. Finally, biological experiments demonstrate that the elastomer possesses good biocompatibility and can facilitate wound healing in mice when used as sutures. It is believed that the obtained elastomer meets the requirements for next-generation elastomers and is expected to be used in emerging fields such as biomedicine, flexible electronics, robotics and beyond.

Core-Shell Filament with Excellent Wound Healing Property Made of Cellulose Nanofibrils and Guar Gum via Interfacial Polyelectrolyte Complexation Spinning

Natural polymer-based sutures have attractive cytocompatibility and degradability in surgical operations. Herein, anionic cellulose nanofibrils (ACNF) and cationic guar gum (CGG) are employed to produce nontoxic CGG/ACNF composite filament with a unique core-shell structure via interfacial polyelectrolyte complexation (IPC) spinning. The comprehensive characterization and application performance of the resultant CGG/ACNF filament as a surgical suture are thoroughly investigated in comparison with silk and PGLA (90% glycolide and 10% l-lactide) sutures in vitro and in vivo, respectively. Results show that the CGG/ACNF filament with the typical core-shell structure and nervation pattern surface exhibits a high orientation index (0.74) and good mechanical properties. The tensile strength and knotting strength of CGG/ACNF suture prepared by twisting CGG/ACNF filaments increase by 69.5%, and CGG/ACNF suture has a similar friction coefficient to silk and PGLA sutures. Moreover, CGG/ACNF suture with antibiosis and cytocompatibility exhibits better growth promotion of cells than silk suture, similar to PGLA suture in vitro. In addition, the stitching experiment of mice with the CGG/ACNF suture further confirms better healing properties and less inflammation in vivo than silk and PGLA sutures do. Hence, the CGG/ACNF suture with a simple preparation method and excellent application properties is promising in surgical operations.

Stretchable One-Dimensional Conductors for Wearable Applications

Continuous, one-dimensional (1D) stretchable conductors have attracted significant attention for the development of wearables and soft-matter electronics. Through the use of advanced spinning, printing, and textile technologies, 1D stretchable conductors in the forms of fibers, wires, and yarns can be designed and engineered to meet the demanding requirements for different wearable applications. Several crucial parameters, such as microarchitecture, conductivity, stretchability, and scalability, play essential roles in designing and developing wearable devices and intelligent textiles. Methodologies and fabrication processes have successfully realized 1D conductors that are highly conductive, strong, lightweight, stretchable, and conformable and can be readily integrated with common fabrics and soft matter. This review summarizes the latest advances in continuous, 1D stretchable conductors and emphasizes recent developments in materials, methodologies, fabrication processes, and strategies geared toward applications in electrical interconnects, mechanical sensors, actuators, and heaters. This review classifies 1D conductors into three categories on the basis of their electrical responses: (1) rigid 1D conductors, (2) piezoresistive 1D conductors, and (3) resistance-stable 1D conductors. This review also evaluates the present challenges in these areas and presents perspectives for improving the performance of stretchable 1D conductors for wearable textile and flexible electronic applications.

Mussel-inspired nanocomposite hydrogel based on alginate and antimicrobial peptide for infected wound repair

Timely hemostasis, antibacterial activity, and good adhesion are essential for wound healing. Here, we report about a novel nanocomposite hydrogel with hemostatic, antibacterial, and adhesive properties constructed with a mussel-inspired strategy. Oxidized alginic acid, dopamine, and antimicrobial peptide ε-polylysine were used to prepare a nanocomposite (ODP), and then further cross-linked with acrylamide to fabricate a nanocomposite hydrogel (ODPA). ODPA hydrogel can adhere to the surface of bleeding organs and arrest bleeding within 30 s. It can also be stretched to 12 times its original length and withstand a compression strain of 40 %, and shows effective inhibition on gram-positive and gram-negative bacteria. Compared with commercial alginate sponge, ODPA hydrogel can accelerate the healing of infected full-thickness wound by reducing inflammation, promoting angiogenesis, and collagen deposition. Therefore, the nanocomposite hydrogel is expected to be a multifunctional dressing for promoting healing of infected wounds.

Bacterial cellulose: A promising biopolymer with interesting properties and applications

The ever-increasing demands for materials with desirable properties led to the development of materials that impose unfavorable influences on the environment and the ecosystem. Developing a low-cost, durable, and eco-friendly functional material with biological origins has become necessary to avoid these consequences. Bacterial cellulose generated by bacteria dispenses excellent structural and functional properties and satisfies these requirements. BC and BC-derived materials are essential in developing pure and environmentally safe functional materials. This review offers a detailed understanding of the biosynthesis of BC, properties, various functionalization methods, and applicability in biomedical, water treatment, food storage, energy conversion, and energy storage applications.