Adhesives with excellent adhesion properties are crucial for aquatic activities. However, natural dynamic water can lead to the loss of adhesive molecules and a reduction in adhesion strength. In this work, we propose a unique phase-separated underwater adhesive through the copolymerization of hydrophilic and hydrophobic monomers. The hydrophobic groups repel interfacial water, while the hydrophilic groups form strong bonds with substrates, endowing the adhesive with outstanding adhesion. Moreover, the adhesive exhibits unique self-reinforcing properties in dynamic water. The self-reinforcement is realized through dynamic water-accelerated phase separation kinetics of the adhesive. The dynamic water forms a dense surface of adhesive, reducing adhesive loss and increasing the bonding area. The adhesion strength in dynamic water significantly increases, reaching 1.97-fold of that in static water. In addition, the adhesive demonstrates excellent adaptability and maintains strong adhesion in various water environments. Benefiting from its linear structure and good solubility, the adhesive exhibits recyclability and erasability, which promotes sustainable chemistry and utility. The recycled adhesive retains 95% of its original adhesive strength without obvious damage. The adhesive demonstrates practicality and accessibility in applications such as tube repair and leakage sealing. Overall, this work provides insights into the design and preparation of novel self-reinforcing underwater adhesives.

High-entropy alloys (HEAs), as new catalytic materials, reveal excellent catalytic performance in numerous reactions. However, how to rationally design high-entropy alloy catalysts with high hydrothermal stability for the efficient hydrogenation of biomass in the presence of water remains a challenge. In this work, we successfully synthesized an FeCo3NiCu0.5Zr HEA catalyst by precisely designing the metal composition and adjusting the metal ratios. The catalyst achieved near-complete conversion (>99%) of furfural with up to 98% selectivity toward the target product, furfuryl alcohol, in the presence of 8% water. Even if the water content increased to 20%, the selectivity for furfuryl alcohol remained above 90%, with furfural conversion exceeding 99%. H2-TPR and H2O-TPD characterization results revealed that the HEA nanoparticles not only possessed excellent hydrothermal stability but also dissociated surface free water molecules to generate H* and *OH. Furthermore, the surface oxygen vacancies are generated through the combination of bridging hydroxyl and terminal hydroxyl groups on the HEA surface, accompanied by the release of H2O. The carbonyl group of the furfural molecule preferentially adsorbs on a surface oxygen vacancy in the catalyst, which effectively shortens the distance between the active hydrogen and the carbonyl group, thereby promoting the hydrogenation reaction. This study not only broadens the application of high-entropy metal compounds but also promotes the directional conversion of biomass into high-value-added chemicals in the presence of water.

Marine mussels exhibit remarkable adhesive capabilities, providing key inspiration for developing underwater adhesives. However, most existing underwater adhesives fail to replicate the convenient, robust, rapid, and stable adhesion of marine mussels. In this work, we developed a biomimetic underwater adhesive (BMUA) that combines catechol group with solvent-responsive curing mechanism. BMUA was synthesized via a straightforward one-step free radical polymerization in dimethyl sulfoxide (DMSO), using methacrylic acid (MA) and N-isopropylacrylamide (NIPAM) as hydrogen bond (H-bond) components, methyl methacrylate (MMA) as a hydrophobic monomer, and DOPA-functionalized methacrylate as the adhesive unit. Upon water contact, BMUA undergoes solvent exchange rapidly, triggering the formation of a H-bond and hydrophobic crosslinked network. This process effectively displaces interfacial water and enables solidification, resulting in strong underwater adhesion. The BMUA demonstrates high adhesive strength on various substrates under flowing water and maintains robust bonding stability across a range of pH, salinity, and temperature conditions. Notably, BMUA retains efficient adhesion (>1.4 MPa) even after 45 days and shows promising performance in practical applications such as underwater sealing, targeted bonding, and rapid hemostasis in a rat liver injury model. This work offers a new design strategy for high-performance underwater adhesives that closely mimic the advantageous adhesion of marine mussels.

While various biomedical sealants exist, many suffer from several drawbacks. For example, hydrogels with superior sealing properties often exhibit limitations such as conflict-free, individual, and flexible control over injectability and gel physical properties, as well as limitations regarding applications in diverse sealing scenarios. This article presents PL/OHA, a pH-driven injectable hydrogel sealant designed for wound sealing. PL/OHA employs dynamic bonds, including Schiff base and hydrogen bonds, to produce a biodegradable and biocompatible hydrogel sealant. By individually adjusting the pH value and solid content, the gelation time, mechanical properties, and adhesion strength of PL/OHA can be flexibly controlled to meet different requirements in various wound-sealing contexts. Experiments prove that the injection time of the hydrogel can be flexibly controlled, from several seconds to tens of minutes, by changing the pH value. It also exhibits adjustable mechanical properties. When the solid content of the hydrogel is increased from 24% to 36%, the tensile strength increases from 10.12 to 25.12 kPa, and the compressive strength increases from 97.50 to 516.61 kPa. PL/OHA also exhibits remarkable antibacterial activity, wound healing promotion capacity, and excellent biocompatibility. These properties make it a promising candidate for future clinical applications in wound sealing.

Junctional hemorrhage is a major prehospital care challenge, causing 67 % of preventable deaths. In addition, the high risk of secondary hemorrhage during transportation remains a challenge for long-term wound protection. Present hemostatic materials can't simultaneously achieve "anti-high-pressure, fast hemostasis and stable blockage". Inspired by coagulation process, positively charged dense cross-linked structure-inherited microgels (PEDM) were prepared. PEDM hybrid blood form quasi-bicontinuous composite structure (Q-Bi CS), utilizing blood realize rapid anti-high-pressure hemostasis and stable protection. PEDM can self-gel within 15 s when contact with blood, mimicking primary hemostasis to form a quick mechanical blockage. Blood cells are concentrated within 50 s, which promotes the Q-Bi CS formed in 120 s. Compared to PEDM-PBS, the compression modulus of PEDM-blood is improved by 5.4 times, achieving robust blockage. Q-Bi CS showed stable dynamic adhesion with strength maintained at 90.1 % after 200 cycles. In the rabbit femoral artery hemorrhage model, PEDM can achieve rapid hemostasis within 61 s and prevent secondary hemorrhage. PEDM even controlled porcine iliac artery hemorrhage within 30 s. In this paper, the self-gelling of PEDM matches with coagulation process, and blood is incorporated as the reinforcing phase into the Q-Bi CS, overcoming the difficulty of junctional hemostasis.

Effective closure of long incision wounds is crucial in clinical practice but remains challenging for existing bioadhesives due to the deformations of the long incisions. Herein, we propose a concept of shape-adaptive adhesion and achieve it by designing a class of shape-adaptive, deformable adhesive hydrogels (DAHs) for long incision wound closure. The design strategy is facile yet universally applicable, which involves aldehyde polysaccharides as adhesive primers and microgel-type gelators as building blocks. We demonstrate that the microgel-type gelators are responsible for the integration of a deformable matrix in situ, and aldehyde polysaccharides enhance the adhesive performance of the matrix at cost of a little deformability. Optimization of the flexibility of DAH network is effective in balancing the adhesive and deformable properties, thus developing DAHs featured with the adaptability to irregular shapes, robust adhesive properties, and appropriate deformability. As a result, DAHs achieve shape-adaptive adhesion by effectively bonding the long incision and deforming with it without failure. In vivo results clearly show that DAHs stably close the 4 cm-long incision wounds on the backs and the more dynamic incisions on the napes of rats. The shape-adaptive adhesion achieved by DAHs may provide an alternative way for long incision wound treatment. STATEMENT OF SIGNIFICANCE: Bioadhesive is emerging as an effective tool in clinical wound treatment. However, the closure of severe long incision wounds by currently available bioadhesives is still challenging. In this work, we proposed a concept of shape-adaptive adhesion and accordingly developed a bioadhesive building strategy for long incision wound closure. The strategy is universally applicable, which involves aldehyde polysaccharide as an adhesive primer and microgel-type gelators as building blocks. The results showed that the strategy is effective in developing bioadhesives (DAHs) that simultaneously possess shape-adaptive properties, robust adhesive properties and appropriate deformability, thus overcoming the limitations of most existing bioadhesives. With these features, DAHs successfully achieved shape-adaptive adhesion and stable closure of long incision wounds, providing an effective way for wound treatment.

Biocompatible injectable hydrogels hold significant promise for noninvasive and minimally invasive tissue defects filling and repair applications. However, many tissues are subjected to dynamic mechanical environments. The mechanical properties of hydrogels are significantly affected by long-term dynamic mechanical stimulation after injection. Therefore, when injectable systems are applied to tissue defects for its filling and repair, it is urgent to activate relevant mechanisms that compensate for this strength loss in situ. In this study, we designed and synthesized dibromocyclopropane force-responsive micelles, and combined with our previously proposed "microunit inheritance reformation" strategy, we synthesized injectable hydrogels capable of responding to dynamic force environments to achieve real-time in situ reinforcement for the first time. The system exhibits good injectability and biocompatibility with the reformed hydrogel after injection, effectively inheriting the mechanical properties of the parent hydrogel. The formed network can effectively transmit external dynamic mechanical signals to deform the micelles, which triggers the dibromocyclopropane group to break and open the ring and then cross-links with the hyaluronate preexisting in the hydrogel to strengthen the original network in situ. Taking a physically interacting hydrogel synthesized from NaSS and DMAEA-Q as a model, the strength of the reformed force-responsive hydrogel (as-reformed PA-E) enhanced to 1.7 times that of the original hydrogel after 7 days of prolonged high-frequency biomechanical stimulation at 100 Hz. Meanwhile, by replacing different parent hydrogels and inheriting their initial mechanical properties, the force-responsive injectable system could meet diverse mechanical demands, suggesting the universality of our present strategy. This study provides insights for the synthesis of injectable hydrogels used in noninvasive minimally invasive defect filling applications.

Hydrogels showed superiorities in molecularly imprinting sensors for detecting biomolecules owing to their stimulus-responsive nature. However, the excessive swelling of hydrogel during the elution process damages the imprinting cavities, leading to a reduction in sensitivity. In this study, a molecularly imprinted electrochemical sensor was designed for rapid protein recognition. The sensor utilized a composite hydrogel based on hybrid cross-linked calcium alginate/calcium silicate (CaAlg/CaSiO3) to mitigate the excessive swelling of the CaAlg hydrogel. The preparation involved coating a bare carbon electrode with a sodium silicate-sodium alginate (Na2SiO3-NaAlg) mixed solution, cross-linking with CaCl2 solution, and eluting bovine serum albumin (BSA) with Tris-HCl solution. The incorporation of CaSiO3 nanoparticles stabilized the organic-inorganic hybrid structure, enhancing the hydrogel's resistance to swelling and maintaining cavity integrity. The molecularly imprinted polymer (MIP) sensor demonstrated high selectivity for BSA, excellent repeatability, long-term stability, and reproducibility, showing the potential for improved sensitivity in biomolecule detection.

Efficient adhesion in natural dynamic water could greatly facilitate human aquatic activities. However, the loss of adhesive molecules, the barrier of interfacial water and the difficulty of strong solidification in dynamic water environment hinder the adhesion in natural water in practice. Herein, inspired by the “3C” adhesive mode of marine sessile organisms, we propose a universal applicable concept of water-responsive entanglements (WARE) via a combination of the entanglements and responsiveness of polymers for developing dynamic water-applicable adhesives. We demonstrated that WARE-type adhesives underwent a 3C-mimetic adhesive process, including entangled constraint-mediated initial loss suppression, sufficient dehydration-facilitated underwater contact and water responsiveness-promoted underwater crosslinking, thus completing the adhesive process and achieving strong adhesion in dynamic water. Intriguingly, due to the facile synthesis methodology and unique adhesive mode, the WARE-type adhesives also exhibit traits desirable for practical applications, such as mass producibility, long-term storage, on-demand detachment, and recyclability. Taking common human aquatic activities as examples, we further show the effectiveness of the WARE-type adhesives through their strong adhesive performance in simplifying the underwater exploration process, repairing a broken boat and sealing a leaky underwater pipeline in emergency.

Cartilage defect is one of the common tissue defect clinical diseases and may finally lead to osteoarthritis (OA) which threat patients’ physical and psychological health. Polysaccharide is the main component of extracellular matrix (ECM) in cartilage tissue. In the past decades, polysaccharide-based hydrogels have shown great potential for cartilage regeneration considering unique qualities such as biocompatibility, enhanced cell proliferation, drug delivery, low toxicity, and many others. Structures such as chain length and chain branching make polysaccharides have different physical and chemical properties. In this review, cartilage diseases and current treatment options of polysaccharide-based hydrogels for cartilage defection repair were illustrated. We focus on how components and structures of recently developed materials affect the performance. The challenges and perspectives for polysaccharide-based hydrogels in cartilage repair and regeneration were also discussed in depth.

The impressive adhesive capacity of marine mussels has inspired various fascinating designs in biomedical fields. Mussel-inspired injectable adhesive hydrogels, as a type of promising mussel-inspired material, have attracted much attention due to their minimally invasive property and desirable functions provided by mussel-inspired components. In recent decades, various mussel-inspired injectable adhesive hydrogels have been designed and widely applied in numerous biomedical fields. The rational incorporation of mussel-inspired catechol groups endows the injectable hydrogels with the potential to exhibit many properties, including tissue adhesiveness and self-healing, antimicrobial, and antioxidant capabilities, broadening the applications of injectable hydrogels in biomedical fields. In this review, we first give a brief introduction to the adhesion mechanism of mussels and the characteristics of injectable hydrogels. Further, the typical design strategies of mussel-inspired injectable adhesive hydrogels are summarized. The methodologies for integrating catechol groups into polymers and the crosslinking methods of mussel-inspired hydrogels are discussed in this section. In addition, we systematically overview recent mussel-inspired injectable adhesive hydrogels for biomedical applications, with a focus on how the unique properties of these hydrogels benefit their applications in these fields. The challenges and perspectives of mussel-inspired injectable hydrogels are discussed in the last section. This review may provide new inspiration for the design of novel bioinspired injectable hydrogels and facilitate their application in various biomedical fields.

In clinical practice, tissue adhesives have emerged as an alternative tool for wound treatments due to their advantages in ease of use, rapid application, less pain, and minimal tissue damage. Since most tissue adhesives are designed for internal use or wound treatments, the biodegradation of adhesives is important. To endow tissue adhesives with biodegradability, in the past few decades, various biodegradable polymers, either natural polymers (such as chitosan, hyaluronic acid, gelatin, chondroitin sulfate, starch, sodium alginate, glucans, pectin, functional proteins, and peptides) or synthetic polymers (such as poly(lactic acid), polyurethanes, polycaprolactone, and poly(lactic-co-glycolic acid)), have been utilized to develop novel biodegradable tissue adhesives. Incorporated biodegradable polymers are degraded in vivo with time under specific conditions, leading to the destruction of the structure and the further degradation of tissue adhesives. In this review, we first summarize the strategies of utilizing biodegradable polymers to develop tissue adhesives. Furthermore, we provide a symmetric overview of the biodegradable polymers used for tissue adhesives, with a specific focus on the degradability and applications of these tissue adhesives. Additionally, the challenges and perspectives of biodegradable polymer-based tissue adhesives are discussed. We expect that this review can provide new inspirations for the design of novel biodegradable tissue adhesives for biomedical applications.

Integrated wound care, a sequential process of promoting wound hemostasis, sealing, and healing, is of great clinical significance. However, the wet environment of wounds poses formidable challenges for integrated care. Herein, we developed an epidermal growth factor (EGF)-loaded, dehydrated physical microgel (DPM)-formed adhesive hydrogel for the integrated care of wet wounds. The DPMs were designed using the rational combination of hygroscopicity and reversible crosslinking of physical hydrogels. Unlike regular bioadhesives, which consider interfacial water as a barrier to adhesion, DPMs utilize water to form desirable adhesive structures. The hygroscopicity allowed the DPMs to absorb interfacial water and subsequently, the interfacial adhesion was realized by the interactions between tissue and DPMs. The reversible crosslinks further enabled DPMs to integrate into hydrogels (DPM-Gels), thus achieving wet adhesion. Importantly, the water-absorbing gelation mode of DPMs enabled facile loading of biologically active EGF to promote wound healing. We demonstrated that the DPM-Gels possessed wet tissue adhesive performance, with about 40 times the wet adhesive strength of fibrin glue and about 4 times the burst pressure of human blood pressure. Upon application at the injury site, the EGF-loaded DPM-Gels sequentially promoted efficient wound hemostasis, stable sealing, and quick healing, achieving integrated care of wet wounds.

The use of traditional small molecule functional monomers for protein imprinting could cause protein conformational damage, limiting the effectiveness of protein recognition. Herein, macromonomers with amide, imidazole, and benzene ring functional groups (MA-PAVS), and sodium alginate modified with methyl methacrylate ester (MA-Alg) were synthesized. These macromonomers were cross-linked with polyethylene glycol methacrylate (PEGMA) on the modified bare carbon electrode through UV initiation, resulting in the construction of an electrochemical sensor imprinted with bovine serum albumin (BSA) hydrogel. MA-Alg hydrogels and MA-PAVS have a unique role in enhancing the specificity of MIPs recognition while maintaining protein conformational stability. The alginate heteropolymeric hydrogel provides a porous structure that facilitates the interaction between target protein and MIPs, while the MA-PAVS monomer tends to interact with the protein surface rather than entering its internal space, greatly enhancing the specificity of MIPs recognition. The MIPs sensor exhibited excellent electrochemical performance and rapid recognition ability with a detection limit of 1.5×10-9 mg mL-1 (S/N=3). Real sample experiments confirmed that the sensor achieved recoveries of 97.1% to 101.8% for bovine serum albumin, making it a promising solution for protein detection in complex samples.

Prehospital rescue of accidental massive bleeding is crucial for saving lives. However, currently available hemostatic materials are still in infancy in treating accidental bleeding due to the challenges in fully satisfying the complex outdoor hemostatic requirements. Herein, we designed an epidermal growth factor (EGF)- incorporated, microparticle-formed, high-strength, dynamic environment-stable hemostatic gel system for prehospital rescue. Carboxyl and dimethylamide were employed as the hydrogen bond (H-bond) groups and were carefully engineered into the microparticles (DHMs). We demonstrated that the unique H-bond crosslinked micronized structure enabled the DHM-based gelling system to adequately meet the outdoor hemostatic requirements. The stable H-bond groups allow the DHMs to be stored at room temperature and be easily carried around. The small sizes (150-250 mu m) of the DHMs enabled the filling of irregular defects, and upon encountering water, these DHMs integrated into hydrogels (DHMs-gels) with high mechanical strength (1.61 MPa), strong tissue adhesiveness (66.5 kPa) and stable performance under dynamic environments. In vivo results showed that the EGFincorporated DHMs-gels (DHMs-EGF gel) achieved a 100 % survival rate in a simulated rescue process and promoted wound healing. Simultaneously possessing multiple prehospital rescue-required properties, the hemostatic DHMs-EGF may become an effective tool for emergency rescue.

Integrated wound care through sequentially promoting hemostasis, sealing, and healing holds great promise in clinical practice. However, it remains challenging for regular bioadhesives to achieve integrated care of dynamic wounds due to the difficulties in adapting to dynamic mechanical and wet wound environments. Herein, we reported a type of dehydrated, physical double crosslinked microgels (DPDMs) which were capable of in situ forming highly stretchable, compressible and tissue-adhesive hydrogels for integrated care of dynamic wounds. The DPDMs were designed by the rational integration of the reversible crosslinks and double crosslinks into micronized gels. The reversible physical crosslinks enabled the DPDMs to integrate together, and the double crosslinked characteristics further strengthen the formed macroscopical networks (DPDM-Gels). We demonstrated that the DPDM-Gels simultaneously possess outstanding tensile (∼940 kJ/m3) and compressive (∼270 kJ/m3) toughness, commercial bioadhesives-comparable tissue-adhesive strength, together with stable performance under hundreds of deformations. In vivo results further revealed that the DPDM-Gels could effectively stop bleeding in various bleeding models, even in an actual dynamic environment, and enable the integrated care of dynamic skin wounds. On the basis of the remarkable mechanical and appropriate adhesive properties, together with impressive integrated care capacities, the DPDM-Gels may provide a new approach for the smart care of dynamic wounds. STATEMENT OF SIGNIFICANCE: Integrated care of dynamic wounds holds great significance in clinical practice. However, the dynamic and wet wound environments pose great challenges for existing hydrogels to achieve it. This work developed robust adhesive hydrogels for integrated care of dynamic wounds by designing dehydrated, physical double crosslinked microgels (DPDMs). The reversible and double crosslinks enabled DPDMs to integrate into macroscopic hydrogels with high mechanical properties, appropriate adhesive strength and stable performance under hundreds of external deformations. Upon application at the injury site, DPDM-Gels efficiently stopped bleeding, even in an actual dynamic environment and showed effectiveness in integrated care of dynamic wounds. With the fascinating properties, DPDMs may become an effective tool for smart wound care.

Injectable hydrogels that can withstand compressive and tensile forces hold great promise for preventing rebleeding in dynamic mechanical environments after emergency hemostasis of wounds. However, current injectable hydrogels often lack sufficient compressive or tensile performance. Here, a microstructure-united heterogeneous injectable hydrogel (MH) was constructed. The heterogeneous structure endowed MH with a unique "microstructures consecutive transmission" feature, which allowed it to exhibit high compressive and tensile performance simultaneously. In this work, two types of sodium alginate doped hydrogels with different microstructures were physically smashed into microgels, respectively. By mixing the microgels, MH with one micro-pores featured microstructure and another nano-pores featured microstructure can be formed. The obtained MH can withstand both compressive and tensile forces and showed high mechanical performance (compressive modulus: 345.67 ± 10.12 kPa and tensile modulus: 245.19 ± 7.82 kPa). Furtherly, MH was proven to provide stable and sustained hemostasis in the dynamic mechanical environment. Overall, this work provided an effective strategy for constructing injectable hydrogel with high compressive and tensile performance for hemostasis in dynamic mechanical environments.

Deployment of adhesives in natural seawater to in situ bonds is urgently needed in engineering fields. However, stable adhesion in natural seawater remains a challenge due to the turbulent environment and high ion concentration. Herein, we reported a viscous, macromolecular underwater adhesive enhanced by Hofmeister effect (EHUA) for practical application in dynamic seawater. EHUA was synthesized via a facile one-step copolymerization. After transferred into seawater, the solvent of EHUA was exchanged to seawater, and thereby hydrogen bonds inside the adhesive were activated and enhanced by Hofmeister effect. We demonstrated EHUA can adhere on the surface in turbulent seawater, and the adhesive strength could reach 1.691 MPa. In addition, the adhesives also exhibited long-term storage stability and convenient recyclability. These fascinating properties enable adhesives to seal leaky pipelines, repair damaged ships and construct buildings in turbulent seawater. This work may open an avenue for the design of adhesives for seawater environments.

Trauma requires immediate hemostasis during primary care, as well as durable hemostasis that can withstand dynamic wound exposure. Although current hemostatic materials can treat bleeding sites in emergency situations, their mechanical strength and storage conditions limit their practical application. The simultaneous combination of good mechanical properties, storage stability, biocompatibility, and rapid hemostasis of hemostatic materials remains a challenge. In this paper, a novel hemostatic material based on multiple non-covalent bond crosslinking, which has excellent mechanical properties, good biocompatibility, storage stability, and rapid hemostasis ability, is reported. Under the drive of multiple non-covalent bonds, the flowability of hydrogel micro-modules (HM) decreases rapidly within 20 s after exposure to physiological saline. The HM form a gel barrier with a tensile strength of 62.10 kPa and an elongation at break of 1976% under multiple non-covalent bonding. Furthermore, the mechanical properties do not change significantly after 30 days of storage. Cell viability is maintained at over 80% after 3 days of incubation with the cells, and the hemolysis test shows a very low hemolysis rate (2.08%). The hemostatic gel formed by HM effectively prevents secondary bleeding in dynamic hemostasis experiments simulating transportation. This work provides a hemostatic material with comprehensive properties for practical applications.

With the emergence of various hydrogels with excellent functions, the air‐drying of hydrogels has attracted extensive attention. Improving the water retention capacity is critical in the application of hydrogels. Herein, inspired by the dense aggregation structure of natural hydrophilic macromolecules, hydrophilic substances (gelatin and glycerol) are first applied to enhance the water retention capacity of hydrogels by constructing a quenched double‐hydrophilic coating. The weight retention ratio of the modified hydrogels is increased to 72.5% at 25 °C and 40 RH% after 5 days. Furthermore, the construction of hydrophilic coating on the surface does not affect the mechanical properties, and the modified hydrogels still retain strong water retention capacity after loading. In addition, this approach is applicable to hydrogels with different shapes and types, and various materials can be selected. Therefore, the proposed method provides new insights for expanding the application scope and service life of hydrogels.