Dual Physically Cross-Linked κ-Carrageenan-Based Double Network Hydrogels with Superior Self-Healing Performance for Biomedical Application

Molybdoenzymes-emulating bio-heterojunction hydrogel with rapid disinfection and macrophage reprogramming for wound regeneration

Developing hydrogel dressings with the capabilities to accommodate irregular wounds and provide a cascade disinfective-regenerative microenvironment for wound repair is of great importance to combating pathogenic bacteria-infected wounds but remains an ongoing challenge. To address the conundrum, we devise a molybdoenzymes-emulating bio-heterojunction (M-bioHJ) doped double network (DN) hydrogel dressing for bacterial-infected wound healing. The near-infrared (NIR) photothermal effect of the M-bioHJ facilitates the exchange of multiple dynamic crosslinking sites in the hydrogel, endowing the hydrogel with photo-remote reprocessing capabilities to completely accommodate the encountered irregular wounds and ultimately accomplish the admirable therapeutic effect. Meanwhile, the introduced M-bioHJ shows NIR light-enhanced photodynamic activity to induce a massive engendering of reactive oxygen species (ROS), allowing rapid sterilization without reliance on exogenous hydrogen peroxide. Furthermore, the Mo ions released from the M-bioHJ-encapsulated hydrogel can play a crucial role in reprogramming the macrophage phenotype and determining tissue regeneration. Both in vitro and in vivo evidences authenticate the accelerated healing potential of infected wounds through the synergistic effects of photo-reprocessing, disinfection, and macrophage-reprogramming facilitated by the hydrogel. These findings highlight the promising application prospects of such neoteric M-bioHJ-encapsulated hydrogel dressings for wound disinfection and tissue regeneration.

Konjac glucomannan and κ-carrageenan synergistically contribute to the cecal intestinal barrier function of offspring via improving the benefits of maternal milk

As major dietary fibers, konjac glucomannan and κ-carrageenan in the maternal diet potentially improve the breast milk quality and intestinal barrier of the offspring. The study selected thirty-four pregnant sows (Large White × Landrace) with similar parity and backfat. From the 107th day of pregnancy to the 25th day of lactation, they were fed either the basic diet (CON) or the basic diet supplemented with konjac glucomannan and κ-carrageenan (DF). There were 17 replicates in each group, and each replicate consisting of one sow. The results of the milk quality analysis were as follows: in the DF group, the proportions of oleic acid (C18:1n9c), neural acid (C24:1) and monounsaturated fatty acids (MUFAs) in the colostrum, as well as those of palmitic acid (C16:0), palmitoleic acid (C16:1) and ginkgolic acid (C17:1) in the milk, had significantly increased (P < 0.05) and the DF group significantly increased (P < 0.05) the level of glutathione peroxidase (GSH-Px) in milk; In the cecal analysis of the offspring, the DF group significantly increased (P < 0.05) the mRNA levels of occludin, nuclear factor-erythroid 2-related factor 2 (Nrf2), glutamate-cysteine ligase catalytic subunit (GCLC), superoxide dismutase 2 (SOD2) and catalase (CAT), while significantly decreased (P < 0.05) the mRNA level of tumor necrosis factor-alpha (TNF-α). Moreover, the abundance of p_Actinobacteria, g_Sharpea, g_Megasphaera, and g_Acidaminococcus was significantly increased (P < 0.05) in the cecum of offspring in the DF group. In conclusion, konjac glucomannan and κ-carrageenan supplementation in the maternal diet can improve milk quality and positively affect the cecal barrier function of offspring.

Dynamic regulation properties of carrageenan hydrogels based on the Hofmeister effect

κ-Carrageenan (KC) hydrogels are processed from a natural polysaccharide with abundant sources, simple preparation, and superior biocompatibility, which are widely used in the food industry and biomedical applications. Due to fixed water content and loose structure, KC hydrogels crosslinked by hydrogen bonding exhibit inflexible and inferior mechanical properties that considerably restrict their application potential. This study presents a comprehensive investigation of the Hofmeister effect for dynamically modulating KC hydrogels, combining multi-scale mechanistic analysis with versatile applications. The mechanical strength of KC hydrogels was reversibly tuned from 0 to 444 kPa and the hydrogel volume swelling ratio was varied from 0.7 to 1.3 times the original volume. Through a series of characterizations and molecular dynamics simulations, we elucidate the underlying mechanisms via three complementary perspectives: aggregation behavior of molecular chains, microstructural anisotropy, and molecular-level hydrogen bonding interactions. The Hofmeister effect confers dynamic shape tunability properties, regulable volume properties, and adjustable mechanical properties on KC hydrogel, positioning it as a potential shape-regulation material and also rendering it a suitable solution sieve and a probe to measure softness and hardness. The exploration of the Hofmeister effect on KC hydrogels establishes a generalizable framework for understanding Hofmeister effects in natural polymer hydrogels while significantly expanding their potential in intelligent materials.

Supramolecular oral delivery technologies for polypeptide-based drugs

Oral supramolecular drug delivery systems (SDDSs) have shown promising potential, along with a rapid increase in the development of polypeptide-based drugs. Biofriendly, biocompatible, and multistimulation-responsive SDDSs achieve their unique deliverability via noncovalent bonds, which can encapsulate drugs and release them at the target site along the oral tract. In this review, we analyze the oral tract from an anatomical perspective and explain the potential physical, microenvironmental, and systematic barriers, as well as the properties of drug delivery. After understanding the specific environment at different oral sites, the application of SDDSs to the mouth, stomach, small intestine, and cell targeting is summarized. Finally, this review summarizes the application of SDDSs for the successful delivery of drugs and describes how to overcome the barriers of SDDSs in drug delivery using a more biofriendly approach.

Tuning Network Topology through Polymerization-Induced Entanglements for Tough and Low-Hysteresis Double Network Hydrogels

In conventional double network (CDN) hydrogels, dense chemical cross-linking in the first network frequently induces structural imperfections, resulting in significant energy dissipation and substantial hysteresis under stress. To improve structural uniformity, spatial heterogeneities can be minimized by introducing mobile cross-linking, which facilitates the creation of a more homogeneous network. Herein, we employed a polymerization-induced entanglements (PIEs) strategy to tune the first network from a traditional net-like to a fabric-inspired topology, simultaneously promoting greater chain entanglement with the second network. This innovative approach enables PIEs DN hydrogels with exceptional performance, including significantly reduced hysteresis (0.15), high tensile strength (1.25 MPa), and excellent toughness (5800 J/m2), overcoming the long-standing trade-off between toughness and hysteresis observed in CDN hydrogels and offering insights and avenues for expanding DN hydrogel applications.

Highly ionic conductive, elastic, and biocompatible double-network composite gel for epidermal biopotential monitoring and wearable sensing

Soft ionic conductors are promising candidates for epidermal electrodes, flexible sensors, ionic skins, and other soft iontronic devices. However, their inadequate ionic conductivity and mechanical properties (such as toughness and adhesiveness) are still the main constraints for their wide applications in wearable bioelectronics. Herein, an all-biocompatible composite gel with a double-network (DN) strategy is proposed. Compared to the single network, introducing a double-helix structured ι-carrageenan facilitates the DN gel with greatly enhanced mechanical properties and higher ionic conductivity (16.0 mS cm-1). Moreover, the DN gels exhibit high transparency (>92 %), high stretchability (1660 %), and sufficient adhesion. Benefiting from the above unique features, the DN gels successfully serve as biopotential electrodes, which can dynamically monitor human electrophysiological signals with a higher signal-to-noise ratio and superior environmental stability than the commercial electrode. Additionally, they can be employed as resistive strain sensors for accurate human movement monitoring. Our multifunctional DN composite gels offer a feasible platform for on-skin bioelectronics and human-machine interactions.

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.

A high temperature-resistant, strong, and self-healing double-network hydrogel for profile control in oil recovery

Hydrogels are widely used in profile control to plug high-permeability zones in oil recovery. In this study, a novel double-network (DN) hydrogel is developed for profile control. The two networks of the prepared hydrogel are polyacrylamide (PAAm) crosslinked by N,N'-Methylenebisacrylamide (MBAA) and konjac glucomannan (KGM) crosslinked by borax (B), respectively. The two networks are interconnected by their interpenetrating structures and hydrogen bonds. Based on the results of a series of evaluation experiments, the AAm/KGM DN hydrogels developed in this study exhibit a strong mechanical strength with their fracture stresses exceeding 0.137 MPa. Meanwhile, the AAm/KGM DN hydrogels can remain thermally stable after being heated at 130 °C for 24 h, indicating the good high-temperature resistance of the new sample. Moreover, the prepared AAm/KGM DN hydrogels present excellent self-healing performance due to the abundant hydrogen bonds in their structures, which helps form stable and long-term plugging in porous media. In addition, the pure PAAm hydrogel and the AAm/KGM DN hydrogel are sheared into two dispersed particle gel (DPG) suspensions to investigate their plugging performances. The results demonstrate that the AAm/KGM DN DPG can effectively plug a high-permeability sandpack with a plugging efficiency of 93.2 %, while the pure AAm DPG can only provide a much lower plugging efficiency of 60.5 %. The AAm/KGM DN hydrogel developed in this study, with its high mechanical strength, high-temperature resistance, and self-healing capability, offers a promising new candidate for profile control in oil recovery.

A synergistic enhancement strategy for mechanical and conductive properties of hydrogels with dual ionically cross-linked κ-carrageenan/poly(sodium acrylate-co-acrylamide) network

Applying conductive hydrogels in electronic skin, health monitoring, and wearable devices has aroused great research interest. Yet, it remains a significant challenge to prepare conductive hydrogels simultaneously with superior mechanical, self-recovery, and conductivity performance. Herein, a dual ionically cross-linked double network (DN) hydrogel is fabricated based on K+ and Fe3+ ion cross-linked κ-carrageenan (κ-CG) and Fe3+ ion cross-linked poly(sodium acrylate-co-acrylamide) P(AANa-co-AM). Benefiting from the abundance of hydrogen bonds and metal coordination bonds, the conductive hydrogel has excellent mechanical properties (fracture strain up to 1420 %, fracture stress up to 2.30 MPa, and toughness up to 20.63 MJ/m3) and good self-recovery performance (the recovery rate of the toughness can reach 85 % after waiting for 1 h). Meanwhile, due to the introduction of dual metal ions of K+ and Fe3+, the ionic conductivity of conductive hydrogel is up to 1.42 S/m. Furthermore, the hydrogel strain sensor has good sensitivity with a gauge factor (GF) of 2.41 (0-100 %). It can be a wearable sensor that monitors different human motions, such as sit-ups. This work offers a new synergistic strategy for designing a hydrogel strain sensor with high mechanical, self-recovery, and conductive properties.

A gelatin/acrylamide-based hydrogel for smart drug release monitoring and radiation-induced wound repair in breast cancer

Radiotherapy is a common local treatment for breast cancer, and while it is effective in targeting tumor cells, it inevitably causes significant side effects. These include excessive production of reactive oxygen species (ROS), repeated inflammatory, and severe skin ulceration, all of which can hinder the wound healing process. As a result, there is a pressing need for multifunctional medical dressings that can support wound repair following radiotherapy. In this study, we introduced a novel double-network interpenetrating hydrogel (GEMC), which combined gelatin grafted dopamine (GEDA), acrylamide, nano-clay (NC), and curcumin loaded nanoparticles (CCNPs). Unlike traditional single-function hydrogels, the GEMC hydrogel offered a combination of antioxidant properties, tissue adhesion, and real time drug tracking, effectively addressing the multifaceted challenges of wound healing after radiotherapy. The GEMC hydrogel exhibited impressive antioxidant activity and superior mechanical properties, which collectively improve the support and protection of wounded surfaces. Furthermore, GEMC promoted skin regeneration, angiogenesis and reduced inflammatory in a mouse model of radiotherapy-induced skin ulceration. These results highlight the hydrogel's potential to accelerate would healing and enhance the effectiveness of post-radiotherapy wound care, providing a promising new approach to improving the quality of skin recovery following radiotherapy.

Fast Self-Healing Hyaluronic Acid Hydrogel with a Double-Dynamic Network for Skin Wound Repair

Developing extracellular matrix-derived hydrogel with a fast self-healing capacity to provide a sustainable moist environment able to accelerate wound healing is highly desired for full-thickness skin wound repair. In this study, a fast self-healing hyaluronic acid hydrogel with a dual dynamic network was constructed through a primary reversible acylhydrazone bond formed between aldehyde-modified hyaluronic acid, 3,3'-dithiobis (propionyl hydrazide) (DTP), and secondary dynamic ionic interactions between κ-carrageenan (KC) and K+. Because of the presence of various dynamic covalent bonds such as the acylhydrazone bond, disulfide bond, and noncovalent bonds including hydrogen bonding and ionic interactions, as well as the notable thermoreversible nature of KC, the resultant hydrogel could be self-healed rapidly within 30 min under physiological temperature with a self-healing efficiency of 100%, which was significantly better than other hyaluronic acid hydrogels, as reported previously. Besides, the hydrogel displayed excellent cytocompatibility. According to this study, the hydrogel was administered into the wounds and achieved a superior performance of promoting full-thickness skin wound healing by increasing granulation tissue formation, deposition of collagen as well as the acceleration of re-epithelialization and neovascularization, compared to commercial products, e.g., gauze and 3 M hydrocolloid. We also anticipate that this strategy of double-dynamic network cross-linking can be adopted to fabricate self-healing materials for multiple applications.

A flexible, stretchable and wearable strain sensor based on physical eutectogels for deep learning-assisted motion identification

Physical eutectogels as a newly emerging type of conductive gel have gained extensive interest for the next generation multifunctional electronic devices. Nevertheless, some obstacles, including weak mechanical performance, low self-adhesive strength, lack of self-healing capacity, and low conductivity, hinder their practical use in wearable strain sensors. Herein, lignin as a green filler and a multifunctional hydrogen bond donor was directly dissolved in a deep eutectic solvent (DES) composed of acrylic acid (AA) and choline chloride, and lignin-reinforced physical eutectogels (DESL) were obtained by the polymerization of AA. Due to the unique features of lignin and DES, the prepared DESL eutectogels exhibit good transparency, UV shielding capacity, excellent mechanical performance, outstanding self-adhesiveness, superior self-healing properties, and high conductivity. Based on the aforementioned integrated functions, a wearable strain sensor displaying a wide working range (0-1500%), high sensitivity (GF = 18.15), rapid responsiveness, and excellent stability and durability (1000 cycles) and capable of detecting diverse human motions was fabricated. Additionally, by combining DESL sensors with a deep learning technique, a gesture recognition system with accuracy as high as 98.8% was achieved. Overall, this work provides an innovative idea for constructing multifunction-integrated physical eutectogels for application in wearable electronics.

Multifunctional surface of the nano-morphic PEEK implant with enhanced angiogenic, osteogenic and antibacterial properties

Polyetheretherketone (PEEK) is a high-performance polymer suitable for use in biomedical coatings. The implants based on PEEK have been extensively studied in dental and orthopedic fields. However, their inherent inert surfaces and poor osteogenic properties limit their broader clinical applications. Thus, there is a pressing need to produce a multifunctional PEEK implant to address this issue. In response, we developed sulfonated PEEK (sPEEK)-Cobalt-parathyroid hormone (PTH) materials featuring multifunctional nanostructures. This involved loading cobalt (Co) ions and PTH (1-34) protein onto the PEEK implant to tackle this challenge. The findings revealed that the controlled release of Co2+ notably enhanced the vascular formation and the expression of angiogenic-related genes, and offered antimicrobial capabilities for sPEEK-Co-PTH materials. Additionally, the sPEEK-Co-PTH group exhibited improved cell compatibility and bone regeneration capacity in terms of cell activity, alkaline phosphatase (ALP) staining, matrix mineralization and osteogenic gene expression. It surpassed solely sulfonated and other functionalized sPEEK groups, demonstrating comparable efficacy even when compared to the titanium (Ti) group. Crucially, animal experiments also corroborated the significant enhancement of osteogenesis due to the dual loading of cobalt ions and PTH (1-34). This study demonstrated the potential of bioactive Co2+ and PTH (1-34) for bone replacement, optimizing the bone integration of PEEK implants in clinical applications.

Exploring carrageenan: From seaweed to biomedicine-A comprehensive review

Biomaterials are pivotal in the realms of tissue engineering, regenerative medicine, and drug delivery and serve as fundamental building blocks. Within this dynamic landscape, polymeric biomaterials emerge as the frontrunners, offering unparalleled versatility across physical, chemical, and biological domains. Natural polymers, in particular, captivate attention for their inherent bioactivity. Among these, carrageenan (CRG), extracted from red seaweeds, stands out as a naturally occurring polysaccharide with immense potential in various biomedical applications. CRG boasts a unique array of properties, encompassing antiviral, antibacterial, immunomodulatory, antihyperlipidemic, antioxidant, and antitumor attributes, positioning it as an attractive choice for cutting-edge research in drug delivery, wound healing, and tissue regeneration. This comprehensive review encapsulates the multifaceted properties of CRG, shedding light on the chemical modifications that it undergoes. Additionally, it spotlights pioneering research that harnesses the potential of CRG to craft scaffolds and drug delivery systems, offering high efficacy in the realms of tissue repair and disease intervention. In essence, this review celebrates the remarkable versatility of CRG and its transformative role in advancing biomedical solutions.

Stretch Sensor: Development of Biodegradable Film

This article presents research on biodegradable stretch sensors produced using biological material. This sensor uses a piezoresistive effect to indicate stretch, which can be used for force measurement. In this work, an attempt was made to develop the composition of a sensitive material and to design a sensor. The biodegradable base was made from a κ-carrageenan compound mixed with Fe2O3 microparticles and glycerol. The influence of the weight fraction and iron oxide microparticles on the tensile strength and Young's modulus was experimentally investigated. Tensile test specimens consisted of 10-25% iron oxide microparticles of various sizes. The results showed that increasing the mass fraction of the reinforcement improved the Young's modulus compared to the pure sample and decreased the elongation percentage. The GF of the developed films varies from 0.67 to 10.47 depending on composition. In this paper, it was shown that the incorporation of appropriate amounts of Fe2O3 microparticles into κ-carrageenan can achieve dramatic improvements in mechanical properties, resulting in elongation of up to 10%. The developed sensors were experimentally tested, and their sensitivity, stability, and range were determined. Finally, conclusions were drawn on the results obtained.

Self-healing, ultra-stretchable, and highly sensitive conductive hydrogel reinforced by sulfate polysaccharide from Enteromorpha prolifera for human motion sensing

The synthesis of multifunctional conductive hydrogel has attracted extensive attention worldwide due to their integrated properties of stretchability, self-adhesion, self-healing, and high sensitivity, while it is still a challenge. Although various kinds of polysaccharides and their derivatives are used to achieve the aforementioned objective, there are few researches about hydrogel design introducing sulfated polysaccharide from Enteromorpha prolifera (SPE), which is rich in hydroxyl, sulfate, and carboxyl groups providing amounts of reaction sites for hydrogel synthesis. Herein, conductive hydrogel (PAA-Al3+-SPE3) reinforced by SPE was designed by simple one pot hot polymerization method. This hydrogel demonstrated charming extension ratio (up to 4027.40 %), strain stress (up to 59.94 kPa), compressive strength (19.71 Mpa), and high conductivity sensibility (GF 6.76, 300 % - 700 %). Additionally, PAA-Al3+-SPE3 showed good self-healing property (repaired autonomously after 60 s) and satisfied self-adhesion (31.11 kPa) due to the reversible hydrogen bonds and metal coordination interactions. Furthermore, the PAA-Al3+-SPE3 hydrogel showed great real-time sensing performance to monitor various motions. These findings suggest the potential of PAA-Al3+-SPE3 hydrogel as an affordable and reliable conductive sensing material. Meantime, the first utilization of SPE to construct flexible wearable sensors offers new route for the high-value application of Enteromorpha prolifera.

Polysaccharide-Based Double-Network Hydrogels: Polysaccharide Effect, Strengthening Mechanisms, and Applications

Polysaccharides are carbohydrate polymers that are major components of plants, animals, and microorganisms, with unique properties. Biological hydrogels are polymeric networks that imbibe and retain large amounts of water and are the major components of living organisms. The mechanical properties of hydrogels are critical for their functionality and applications. Since synthetic polymeric double-network (DN) hydrogels possess unique network structures with high and tunable mechanical properties, many natural functional polysaccharides have attracted increased attention due to their rich and convenient sources, unique chemical structure and chain conformation, inherently desirable cytocompatibility, biodegradability and environmental friendliness, diverse bioactivities, and rheological properties, which rationally make them prominent constituents in designing various strong and tough polysaccharide-based DN hydrogels over the past ten years. This review focuses on the latest developments of polysaccharide-based DN hydrogels to comprehend the relationship among the polysaccharide properties, inner strengthening mechanisms, and applications. The aim of this review is to provide an insightful mechanical interpretation of the design strategy of novel polysaccharide-based DN hydrogels and their applications by introducing the correlation between performance and composition. The mechanical behavior of DN hydrogels and the roles of varieties of marine, microbial, plant, and animal polysaccharides are emphatically explained.

Photothermal Conversion of Hydrogel-Based Biomaterial

Traditional energy from fossil fuels like petroleum and coal is limited and contributes to global environmental pollution and climate change. Developing sustainable and eco-friendly energy is crucial for addressing significant challenges such as climate change, energy dilemma and achieving the long-term development of human society. Biomass hydrogels, which are easily synthesized and modified, have diverse sources and can be designed for different applications. They are being extensively researched for their applications in artificial intelligence, flexible sensing, biomedicine, and food packaging. The article summarizes recent advances in the preparation and applications of biomass-based photothermal conversion hydrogels, discussing the light source, photothermal agents, matrix, and preparation methods in detail. It also explores the use of these hydrogels in seawater desalination, photothermal therapy, antibacterial agents, and light-activated materials, offering new ideas for developing sustainable, efficient, and advanced photothermal conversion biomass hydrogel materials. The article concludes with suggestions for future research, highlighting the challenges and prospects in this field and paving the way for developing of long-lasting, efficient energy materials.

Injectable and self-healing dual crosslinked gelatin/kappa-carrageenan methacryloyl hybrid hydrogels via host-guest supramolecular interaction for wound healing

Injectable hydrogels based on natural polymers have shown great potential for various tissue engineering applications, such as wound healing. However, poor mechanical properties and weak self-healing ability are still major challenges. In this work, we introduce a host-guest (HG) supramolecular interaction between acrylate-β-cyclodextrin (Ac-β-CD) conjugated on methacrylated kappa-carrageenan (MA-κ-CA) and aromatic residues on gelatin to provide self-healing characteristics. We synthesize an MA-κ-CA to conjugate Ac-β-CD and fabricate dual crosslinked hybrid hydrogels with gelatin to mimic the native extracellular matrix (ECM). The dual crosslinking occurs on the MA-κ-CA backbone through the addition of KCl and photocrosslinking process, which enhances mechanical strength and stability. The hybrid hydrogels exhibit shear-thinning, self-healing, and injectable behavior, which apply easily under a minimally invasive manner and contribute to shear stress during the injection. In-vitro studies indicate enhanced cell viability. Furthermore, scratch assays are performed to examine cell migration and cell-cell interaction. It is envisioned that the combination of self-healing and injectable dual crosslinked hybrid hydrogels with HG interactions display a promising and functional biomaterial platform for wound healing applications.

Double network hydrogels: Design, fabrication, and application in biomedicines and foods

Research on the design, fabrication, and application of double network (DN) hydrogels, assembled from pairs of polymers, has grown recently due to their unique structural, physicochemical, and functional properties. DN hydrogels can be designed to exhibit a broader range of functional attributes than single network (SN) ones, which extends their applications in various fields. There has been strong interest in the development of biopolymer DN hydrogels because of their environmental, sustainability, and safety benefits. However, there is limited knowledge on the formation and application of these novel materials. This article reviews the principles underlying the design and fabrication of hydrogels using different crosslinking approaches, including covalent and/or non-covalent bonding, and the formation mechanisms, network structures, and functional attributes of different DN hydrogels. The impact of polymer composition, structural organization, and bonding on the mechanical and functional properties of DN hydrogels is reviewed. Potential applications of these hydrogels are highlighted, including in tissue engineering, biomedicines, and foods. The functional attributes of DN hydrogels can be tailored to each of these applications by careful selection of the biopolymers and crosslinking mechanisms used to assemble them. Finally, areas where further research are needed to overcome the current limitations of DN hydrogels are highlighted.

Improving the mechanical properties of 3D printed GelMA composite hydrogels by tannic acid

The lack of advanced biomaterials is a major challenge in bio‐printing. Gelatin‐methacryloyl (GelMA) hydrogel, as one of the most commonly used biomaterials in 3D printing, has limited the applications of medicine because of its low mechanical properties. In this study, to enhance the mechanical strength of GelMA hydrogels, we prepared a composite hydrogel based on F127 diacrylate (F127DA) and GelMA, followed by lyophilization and tannic acid (TA) treatment. In this composite hydrogel, the F127DA could self‐assemble into nanomicelles as crosslinking centers for monomer polymerization, which provides additional energy dissipation in hydrogels due to the synergistic deformation of micelles and internal rearrangement of physical binding. After lyophilization of the composite hydrogel, the porous hydrogel was formed. The subsequent treatment of TA could diffuse into the inner of the hydrogel and react with the hydrogel via hydrogen bonds, resulting in the significant enhancement of mechanical properties. The maximum tensile deformation of the obtained hydrogel was about 11 times higher than that of GelMA. This work demonstrates a method to enhance the mechanical properties of 3D‐printed GelMA hydrogel with promising application in bioprinting.

A natural polymer-based hydrogel with shape controllability and high toughness and its application to efficient osteochondral regeneration

Hydrogels prepared from sustainable natural polymers have broad prospects in the biological field. However, their poor mechanical properties and challenges in achieving shape control have limited their application. Herein, a novel preforming dual-effect post-enhancing method is proposed to address these issues. The method utilizes the hydrogen bonding of agar to obtain a shape-controllable preformed hydrogel at low polymer concentrations using casting, injection, or 3D printing techniques. Subsequently, the preformed hydrogel was subjected to a permeation process to form a post-enhanced multi-network (PEMN) hydrogel with hierarchical chain entanglements to ensure its high toughness, which exhibits tensile and compressive strengths of up to 0.51 MPa and 1.26 MPa with solely physically crosslinking networks. The excellent biocompatibility of the PEMN hydrogel prepared without the need for additional initiator agents under mild conditions was confirmed by both in vitro and in vivo experiments. Furthermore, the adaptability for irregular defects, suitable toughness, adhesive properties, and degradability of PEMN hydrogels are beneficial to provide mechanical support, induce endogenous cell mineralization, and accelerate the regeneration of cartilage and subchondral bone with more than 40% bone regeneration in 12 weeks. Our work has provided a novel solution to simultaneously achieve shape controllability and high toughness based on natural polymers among the already well-explored strategies for osteochondral regeneration.

Does the disclosure of medical insurance information affect patients' willingness to adopt the diagnosis related groups system

Introduction

Medical insurance information disclosure is not only a direct way for the public to understand and master social insurance information and resource use benefits, but also an important way for the public to participate in medical service governance and supervision. Some studies have shown that information disclosure can significantly reduce the risk perception of user groups, strengthen their trust and reduce the negative impact of information asymmetry.

Methods

Based on risk perception and trust perception theories, this paper focuses on the mechanisms influencing patients' attitudes in the process of implementing a Diagnosis Related Groups payment system. Using medical insurance information disclosure from a governance perspective as the research object, the impact of medical insurance information disclosure on patients' willingness to adopt the Diagnosis Related Groups payment system was analyzed by means of a questionnaire survey, Data analysis and hypothesis testing via SPSS while the mechanism of the impact of medical insurance information disclosure on patients' attitudes was explored in depth.

Results

It was found that medical insurance information disclosure had a significant positive effect on patients' trust perceptions and a significant negative effect on patients' risk perceptions. The more comprehensive information patients received, the stronger their trust and the lower their perceived risk.

Discussion

This paper conducts an empirical study from patients' perspective, broadens the scope of research on medical insurance Diagnosis related groups, enriches the application of risk perception and trust perception theories in the medical field, and provides management suggestions for medical institutions in the management of medical insurance information disclosure.

Physical dual-network photothermal antibacterial multifunctional hydrogel adhesive for wound healing of drug-resistant bacterial infections synthesized from natural polysaccharides

Wound-healing of drug-resistant bacterial infections has always been a clinical challenge. The design and development of effective and economically safe wound dressings with antimicrobial activity and healing-promoting properties is highly desirable, especially in the context of wound-infections. Herein, we designed a physical dual-network multifunctional hydrogel adhesive based on polysaccharide material for the treatment of full-thickness skin defects infected with multidrug-resistant bacteria. The hydrogel utilized ureido-pyrimidinone (UPy)-modified Bletilla striata polysaccharide (BSP) as the first physical interpenetrating network for providing some brittleness and rigidity; and then branched macromolecules formed after cross-linking Fe³⁺ with dopamine-conjugated di-aldehyde-hyaluronic acid as the second physical interpenetrating network for providing some flexibility and elasticity. In this system, BSP and hyaluronic acid (HA) are used as synthetic matrix materials to provide strong biocompatibility and wound-healing ability. In addition, ligand cross-linking of catechol-Fe³⁺ and quadrupole hydrogen-bonding cross-linking of UPy-dimer can form a highly dynamic physical dual-network structure, which imparts good rapid self-healing, injectability, shape-adaptation, NIR/pH responsiveness, high tissue-adhesion and mechanical properties of this hydrogel. Meanwhile, bioactivity experiments demonstrated that the hydrogel also possesses powerful antioxidant, hemostatic, photothermal-antibacterial and wound-healing effects. In conclusion, this functionalized hydrogel is a promising candidate for clinical treatment of full-thickness bacteria-stained wound dressing materials.

Magnetite embedded κ-carrageenan-based double network nanocomposite hydrogel with two-way shape memory properties for flexible electronics and magnetic actuators

Shape memory hydrogels attract increasing attention as flexible strain sensors due to their shape recovery property that can improve the lifetime of the sensor. Herein, we have designed a magnetic shape memory hydrogel based on Fe₃O₄ nanoparticles, carrageenan, and poly (acrylamide-co-acrylic acid) with self-adhesive and conductive properties. The resulting double network hydrogel showed promising actuator and strain sensor applications. Electrical conductivity was observed in this hydrogel without using additional ions. The presence of magnetite nanoparticles increased the tensile strength and temporary shape fixity ratio to around 6.5 MPa and 94.3 %, respectively. The excellent cantilever and catheter-like behavior of the hydrogels were illustrated through magnetic routing by an external magnet. Also, these hydrogels demonstrated suitable performance in the 500 cycles strain sensing tests before and after their initial shape recovery.

κ-Carrageenan-essential oil loaded composite biomaterial film facilitates mechanosensing and tissue regenerative wound healing

Polysaccharides κ-carrageenan (κ-Car) have become a predominant source in developing bioactive materials. We aimed to develop biopolymer composite materials of κ-Car with coriander essential oil (CEO) (κ-Car-CEO) films for fibroblast-associated wound healing. Initially, we loaded the CEO in to κ-Car and CEO through homogenization and ultrasonication to fabricate composite film bioactive materials. After performing morphological and chemical characterizations, we validated the developed material functionalities in both in vitro and in vivo models. The chemical and morphological analysis with physical structure, swelling ratio, encapsulation efficiency, CEO release, and water barrier properties of films examined and showed the structural interaction of κ-Car and CEO-loaded into the polymer network. Furthermore, the bioactive applications of CEO release showed initial burst release followed by controlled release from the κ-Car composite film with fibroblast (L929) cell adhesive capabilities and mechanosensing. Our results proved that the CEO-loaded into the κ-Car film impacts cell adhesion, F-actin organization, and collagen synthesis, followed by in vitro mechanosensing activation, further promoting wound healing in vivo. Our innovative perspectives of active polysaccharide (κ-Car)-based CEO functional film materials could potentially accomplish regenerative medicine.

Role of conformation transition of high acyl gellan in the design of double network hydrogels

Double network hydrogels (DNs) with excellent strength and toughness have been preliminarily applied in the preparation of artificial foods. To evaluate the effect of conformation transition of ductile polymers on the physicochemical properties of DNs, we firstly prepared agarose (AR)/high acyl gellan (HAG) DNs and investigated their mechanical properties, and then calcium ion (Ca²⁺) was introduced into optimized AR/HAG DNs to regulate the conformation of ductile chains (HAG) for further increasing their mechanical properties. The mechanical strength of the optimized AR/HAG gel is 5 times and 2 times that of AR and HAG gel, respectively. Compared with adding Ca²⁺ method, immersing Ca²⁺ solution endowed optimized DNs with 5-fold increase in mechanical strength, outstanding textural properties and lower swelling ratio, which was attributed to the extended conformation of ductile chains. Furthermore, the obtained DNs were reminiscent of beef omasum based on their physicochemical properties. Optimized AR/HAG DNs after immersing in 2 wt% CaCl₂ solution exhibited comparable texture properties with beef omasum by three correlation analysis methods and sensory evaluation, providing a new strategy to fabricate biomimetic food with high chewiness by regulating the conformation of ductile polymers in DNs.

Hydrogels as the plant culture substrates: A review

A class of hydrophilic polymers known as "hydrogels" have extensive water content and three-dimensional crosslinked networks. Since the old period, they have been utilized as plant culture substrates to get around the drawbacks of hydroponics and soil. Numerous hydrogels, particularly polysaccharides with exceptional stability, high clarity, and low cost can be employed as plant substrates. Although numerous novel and functionalized hydrogels might assist in overcoming the drawbacks of conventional media and giving them more functions, the existing hydrogel-based plant growth substrates rarely benefit from the developments of gels in the previous few decades. Prospects include the development of new conduction techniques, the creation of potential new hydrogels, and the functionalization of the hydrogel as plant culture substrates.

Self-extinguished and flexible cation exchange membranes based on modified K-Carrageenan/PVA double network hydrogels for electrochemical applications

It is highly desired and yet challenging to develop eco-friendly cation exchange membranes with a combination of good mechanical, electrochemical, and biocompatible properties with a rational economic efficiency for given applications. In this study, new biocompatible double network (DN) hydrogels were prepared based on a blend of modified K-Carrageenan (KC) and polyvinyl alcohol (PVA). Acrylic acid (AA)-grafted KC (KC-g-(PAA)) and (AA-co-tertbutyl acrylate (TBA))-grafted KC (KC-g-P(AA-co-TBA)) were synthesized through an in situ free radical copolymerization. The grafted copolymers were blended with PVA and mixed with ZrOCl₂/KCl and glutaraldehyde (Glu) as the physical and chemical cross-linkers, respectively to produce KC-g-P(AA)/PVA and KC-g-P(AA-co-TBA)/PVA DN hydrogels. The membranes were prepared by a solution casting method. Various techniques were carried out to compare the structural, thermal, mechanical, flammability, and electrochemical properties of the membranes with those of the cross-linked KC, PVA, and KC/PVA membranes. The KC-g-P(AA-co-TBA)/PVA DN membrane showed more desirable properties as the cation exchange membrane with water uptake of 70.7 %, ion exchange capacity of 0.47 meq H⁺ /g, the ionic conductivity of 1.99 × 10^-2 S/cm², and elongation at break of 71.8 %. The prepared biopolymer membrane is very cost-effective and self-extinguished with admissible conductivity for electrochemical applications.

Tough and stretchable all-κ-carrageenan hydrogel based on the cooperative effects between chain conformation transition and stepwise mechanical training

The traditional κ-carrageenan (κCG)-based hydrogel obtained from hot water can rupture easily under mechanical loading. To address this vulnerability, here we presented a robust all-κCG hydrogel without employing the second synthetic network. By simply regulating the polymer chains from random coil to stiff chain conformation in NaOH/urea solvent system via the freeze-thawing process, the as-prepared hydrogel with homogeneous structure can display an enhanced stretchability from 42.1 to 156 %, while maintaining the similar fracture stress. Moreover, upon the stepwise mechanical training and subsequent incubation in KCl aqueous solution, more helical segments of κCG were aligned and involved into the association domains, thus leading to the increment in both the crystallinity and anisotropy. Consequently, a fast self-strengthening behavior occurred, and a more stretchable (fracture strain up to 396 %), strong (stress ∼ 0.55 MPa) and tough (∼1.52 MJ m^-3) κCG hydrogel was obtained. In comparison to the traditional one, the fracture strain and toughness are increased by 8.5 and 11.5 times, respectively. In addition, this κCG hydrogel can demonstrate good recovery and shape-memory behaviors under medium deformation. Hence, this tough all-κCG hydrogel is expected to be tailored into the biomaterials as the wearable device, artificial tendon, and cartilage in the future.

Modulation of poly (acrylic acid) hydrogels with κ-carrageenan for high-performance quasi-solid Al-air batteries

Primary quasi-solid Al-air batteries using hydrogels have attracted increasing research attention owing to their high energy density, good handling, safety and reliability. However, it is still difficult to develop hydrogel electrolytes with high ionic conductivity and water retention owing to limited capacity of single material hydrogels. Herein, we report a hydrogel electrolyte of poly (acrylic acid) (PAA) is modified by κ-carrageenan (KC) for solid-state Al-air batteries. The result suggests that the hydrogels not only exhibit outstanding water retention but also high ionic conductivity, which is attributed to the amorphous phase and hydrophilic group of the KC. Additionally, the lifespan of solid-state Al-air battery is extended at a current density of 5 mA cm^-2 owing to adding KC. Further, the lifetime of open Al-air batteries is improved by self-corrosion inhibition of Al anode.

GelMA/κ-carrageenan double-network hydrogels with superior mechanics and biocompatibility

Hydrogels are crosslinked hydrophilic polymer networks of high-water content. Although they have been widely investigated, preparing hydrogels with excellent mechanical properties and biocompatibility remains a challenge. In the present work, we developed a novel GelMA/κ-carrageenan (GelMA/KC) double network (DN) hydrogel through a dual crosslinking strategy. The three-dimensional (3D) microstructure of KC is the first network, and covalently crosslinked on the κ-carrageenan backbone is the second network. The GelMA/KC hydrogel shows advantages in physical properties, including higher compression strength (10% GelMA/1% KC group, 130 kPa) and Young's modulus (10% GelMA/1% KC group, 300), suggesting its excellent elasticity and compressive capability. When using a higher concentration of GelMA, the hybrid hydrogel has even higher mechanical properties. In addition, the GelMA/KC hydrogel is favorable for cell spreading and proliferation, demonstrating its excellent biocompatibility. This study provides a new possibility for a biodegradable and high-strength hydrogel as a new generation material of orthopedic implants.

Photonic double-network hydrogel dressings for antibacterial phototherapy and inflammation regulation in the general management of cutaneous regeneration

The treatment of festering pathogenic bacteria-induced skin wounds with increased inflammation is an ongoing challenge. The traditional antibacterial photothermal therapy always results in localized hyperthermia (over 50 °C), which inevitably delays tissue recovery. To address this serious issue, we devise a novel photonic hydrogel by integrating urchin-like Bi₂S₃ nano-heterojunctions (nano-HJs) into double-network hydrogels for infected skin regeneration. The synergy of NIR-triggered heat and ROS enables the hydrogels to achieve a rapid germicidal efficacy against bacteria within 15 min at mild temperature (below 50 °C). In vitro cell analysis results revealed that the photonic hydrogels exhibit superior cytocompatibility even after NIR illumination. More importantly, an in vivo study demonstrated that the photonic hydrogel dressings have a robust ability of accelerating contagious full-thickness wound regeneration through debriding abscesses, eliminating pathogens, improving collagen deposition, promoting angiogenesis, and adjusting the inflammation state. This photonic hydrogel system provides a general management strategy for the remedy of infectious wounds, where the incorporation of nano-HJs endows the hydrogels with the photodisinfection ability; in addition, the multifunctional hydrogels alleviate the damage from overwhelming heat towards surrounding tissues during phototherapy and steer the inflammation during the process of tissue regeneration. Accordingly, this work highlights the promising application of the photonic hydrogels in conquering refractory pathogen-invaded infection.

Thermal insulation properties of lightweight, self-healing, and mesoporous carrageenan/PMMA cryogels

The development of new bio-based cryogel materials with low environmental impact and various properties such as self-healing, flame-retardancy, low thermal conductivity has emerged as a cutting-edge research topic in special-purpose materials and a significant challenge. Herein, we report a simple processing methodology for preparing new mesoporous light weight thermal insulation biomass hybrid cryogels based on natural and biocompatible polymers, including marine glycosaminoglycan carrageenan moss (CM) and polymethyl methacrylate (PMMA) abbreviated as CM/PMMA under cryo conditions. The mechanical, thermal, and physicochemical characterization of the obtained hybrid cryogel was studied. The effect of increasing thickness on thermal conductivity and compressive strength was investigated. The results show that the thermal conductivity increases from 0.068 W m-1 K-1 to 0.124 W m-1 K-1 with increasing thickness. Also, the compressive strength changed from 89.5% MPa to 95.4% MPa. The results revealed that cryogel has a wrinkled surface and interconnected pores and exhibits high flexibility, self-healing ability, flame retardancy, and low thermal conductivity.

MXene/Gelatin/Polyacrylamide Nanocomposite Double Network Hydrogel with Improved Mechanical and Photothermal Properties

The development of smart hydrogel with excellent mechanical properties and photothermal conversion capability is helpful in expending its application fields. Herein, a MXene/gelatin/polyacrylamide (M/G/PAM) nanocomposite double network (NDN) hydrogel was synthesized by γ-ray radiation technology for the first time. Compared with gelatin/polyacrylamide double network hydrogel, the optimized resultant M₃/G/PAM NDN hydrogel shows better mechanical properties (tensile strength of 634 ± 10 kPa, compressive strength of 3.44 ± 0.12 MPa at a compression ratio of 90%). The M₃/G/PAM NDN hydrogel exhibits a faster heating rate of 30 °C min^-1, stable photothermal ability, and mechanical properties even after 20 cycles of on-off 808 nm near-infrared (NIR) laser irradiation (1.0 W cm^-2). Furthermore, the temperature of M₃/G/PAM NDN hydrogel can be increased rapidly from 25 °C to 90 °C in 10 s and could reach 145 °C in 120 s under irradiation by focused NIR laser irradiation (56.6 W cm^-2). The high mechanical property and photothermal properties of M/G/PAM hydrogel are ascribed to the formation of double network and uniform hydrogen bonding between MXene and gelatin and PAM polymers. This work paves the way for construction of photothermal hydrogels with excellent mechanical properties.

Three-Dimensional Printing of Double-Network Hydrogels: Recent Progress, Challenges, and Future Outlook

Hydrogels are widely used materials due to their biocompatibility, their ability to mimic the hydrated and porous extracellular microenvironment, as well as their ability to tune both mechanical and biochemical properties. However, most hydrogels lack mechanical toughness, and shaping them into complicated three-dimensional (3D) structures remains challenging. In the past decade, tough and stretchable double-network hydrogels (DN gels) were developed for tissue engineering, soft robotics, and applications that require a combination of high-energy dissipation and large deformations. Although DN gels were processed into simple shapes by using conventional casting and molding methods, new 3D printing methods have enabled the shaping of DN gels into structurally complex 3D geometries. This review will describe the state-of-art technologies for shaping tough and stretchable DN gels into custom geometries by using conventional molding and casting, extrusion, and optics-based 3D printing, as well as the key challenges and future outlook in this field.

Magnetic-responsive polysaccharide hydrogels as smart biomaterials: Synthesis, properties, and biomedical applications

This review reports recent advances in polysaccharide-based magnetic hydrogels as smart platforms for different biomedical applications. These hydrogels have proved to be excellent, viable, eco-friendly alternative materials for the biomedical field due to their biocompatibility, biodegradability, and possibility of controlling delivery processes via modulation of the remote magnetic field. We first present their main synthesis methods and compare their advantages and disadvantages. Next, the synergic properties of hydrogels prepared with polysaccharides and magnetic nanoparticles (MNPs) are discussed. Finally, we describe the main contributions of polysaccharide-based magnetic hydrogels in the targeted drug delivery, tissue regeneration, and hyperthermia therapy fields. Overall, this review aims to motivate the synthesis of novel composite biomaterials, based on the combination of magnetic nanoparticles and natural polysaccharides, to overcome challenges that still exist in the treatment of several diseases.

Self-Healing Injectable Hydrogels for Tissue Regeneration

Biomaterials with the ability to self-heal and recover their structural integrity offer many advantages for applications in biomedicine. The past decade has witnessed the rapid emergence of a new class of self-healing biomaterials commonly termed injectable, or printable in the context of 3D printing. These self-healing injectable biomaterials, mostly hydrogels and other soft condensed matter based on reversible chemistry, are able to temporarily fluidize under shear stress and subsequently recover their original mechanical properties. Self-healing injectable hydrogels offer distinct advantages compared to traditional biomaterials. Most notably, they can be administered in a locally targeted and minimally invasive manner through a narrow syringe without the need for invasive surgery. Their moldability allows for a patient-specific intervention and shows great prospects for personalized medicine. Injected hydrogels can facilitate tissue regeneration in multiple ways owing to their viscoelastic and diffusive nature, ranging from simple mechanical support, spatiotemporally controlled delivery of cells or therapeutics, to local recruitment and modulation of host cells to promote tissue regeneration. Consequently, self-healing injectable hydrogels have been at the forefront of many cutting-edge tissue regeneration strategies. This study provides a critical review of the current state of self-healing injectable hydrogels for tissue regeneration. As key challenges toward further maturation of this exciting research field, we identify (i) the trade-off between the self-healing and injectability of hydrogels vs their physical stability, (ii) the lack of consensus on rheological characterization and quantitative benchmarks for self-healing injectable hydrogels, particularly regarding the capillary flow in syringes, and (iii) practical limitations regarding translation toward therapeutically effective formulations for regeneration of specific tissues. Hence, here we (i) review chemical and physical design strategies for self-healing injectable hydrogels, (ii) provide a practical guide for their rheological analysis, and (iii) showcase their applicability for regeneration of various tissues and 3D printing of complex tissues and organoids.

Functional Thermoresponsive Hydrogel Molecule to Material Design for Biomedical Applications

Temperature-induced, rapid changes in the viscosity and reproducible 3-D structure formation makes thermos-sensitive hydrogels an ideal delivery system to act as a cell scaffold or a drug reservoir. Moreover, the hydrogels’ minimum invasiveness, high biocompatibility, and facile elimination from the body have gathered a lot of attention from researchers. This review article attempts to present a complete picture of the exhaustive arena, including the synthesis, mechanism, and biomedical applications of thermosensitive hydrogels. A special section on intellectual property and marketed products tries to shed some light on the commercial potential of thermosensitive hydrogels.

Multifunctional hydrogels for wound dressings using xanthan gum and polyacrylamide

Developing advanced dressings that integrate multiple functions is one of the major challenges in current clinical wound treatment. In this study, Xanthan gum (XG) and polyacrylamide (PAAm) materials were used to prepare hydrogel dressings by one-pot method. With the combination of the PAAm network and the XG network, the PAAm-XG hydrogels showed the tensile strength of 0.36 MPa and the stretchability as large as 2078 %. The prepared PAAm-XG hydrogels had excellent water uptake efficiency with the swelling ratio of 1200 %. Besides, the developed dressings possessed outstanding biocompatibility, universal adhesion and self-healing ability. More importantly, the PAAm-XG hydrogels can be successfully loaded with Cefixime and human recombinant epidermal growth factor, and these loaded hydrogels released these bioactive molecules in sustained ways. As a result, both E. coli and S. aureus bacteria were inactivated after contacting with the Cefixime-loaded hydrogels for 24 h. Furthermore, in vivo data demonstrated that the PAAm-XG hydrogel dressings significantly accelerated the wound healing in a mouse model. All of these indicate that the multifunctional PAAm-XG hydrogels are promising candidates for wound treatment.

Rational mechanochemical design of Diels-Alder crosslinked biocompatible hydrogels with enhanced properties

An important but often overlooked feature of Diels-Alder (DA) cycloadditions is the ability for DA adducts to undergo mechanically induced cycloreversion when placed under force. Herein, we demonstrate that the commonly employed DA cycloaddition between furan and maleimide to crosslink hydrogels results in slow gelation kinetics and "mechanolabile" crosslinks that relate to reduced material strength. Through rational computational design, "mechanoresistant" DA adducts were identified by constrained geometries simulate external force models and employed to enhance failure strength of crosslinked hydrogels. Additionally, utilization of a cyclopentadiene derivative, spiro[2.4]hepta-4,6-diene, provided mechanoresistant DA adducts and rapid gelation in minutes at room temperature. This study illustrates that strategic molecular-level design of DA crosslinks can provide biocompatible materials with improved processing, mechanical durability, lifetime, and utility.

Construction of tissue-customized hydrogels from cross-linkable materials for effective tissue regeneration

Hydrogels are prevalent scaffolds for tissue regeneration because of their hierarchical architectures along with outstanding biocompatibility and unique rheological and mechanical properties. For decades, researchers have found that many materials (natural, synthetic, or hybrid) can form hydrogels using different cross-linking strategies. Traditional strategies for fabricating hydrogels include physical, chemical, and enzymatical cross-linking methods. However, due to the diverse characteristics of different tissues/organs to be regenerated, tissue-customized hydrogels need to be developed through precisely controlled processes, making the manufacture of hydrogels reliant on novel cross-linking strategies. Thus, hybrid cross-linkable materials are proposed to tackle this challenge through hybrid cross-linking strategies. Here, different cross-linkable materials and their associated cross-linking strategies are summarized. From the perspective of the major characteristics of the target tissues/organs, we critically analyze how different cross-linking strategies are tailored to fit the regeneration of such tissues and organs. To further advance this field, more appropriate cross-linkable materials and cross-linking strategies should be investigated. In addition, some innovative technologies, such as 3D bioprinting, the internet of medical things (IoMT), and artificial intelligence (AI), are also proposed to improve the development of hydrogels for more efficient tissue regeneration.

Dual Cross-Linked Starch–Borax Double Network Hydrogels with Tough and Self-Healing Properties

Herein, we have fabricated starch–borax double cross-linked network (DC) hydrogels with tough and self-healing properties using a one-pot method. The addition of borax significantly increased the storage modulus and loss modulus of these starch–borax DC hydrogels. The maximum compression stress (~288 kPa) of starch–borax DC hydrogels containing 5% borax was about ten times greater than that of a pure-starch hydrogel. The texture profile analysis values of the DC hydrogels—including hardness, springiness, cohesiveness, and adhesiveness—increased compared to pure-starch hydrogels. In addition, starch–borax DC hydrogels exhibited excellent self-healing and shape-recovery properties. These DC hydrogels, with a variety of excellent properties, have potential applications in agricultural, biomedical, and industrial fields.