Gelation of highly entangled hydrophobic macromolecular fluid for ultrastrong underwater in situ fast tissue adhesion

Advances and applications of biomimetic biomaterials for endogenous skin regeneration

Endogenous regeneration is becoming an increasingly important strategy for wound healing as it facilitates skin's own regenerative potential for self-healing, thereby avoiding the risks of immune rejection and exogenous infection. However, currently applied biomaterials for inducing endogenous skin regeneration are simplistic in their structure and function, lacking the ability to accurately mimic the intricate tissue structure and regulate the disordered microenvironment. Novel biomimetic biomaterials with precise structure, chemical composition, and biophysical properties offer a promising avenue for achieving perfect endogenous skin regeneration. Here, we outline the recent advances in biomimetic materials induced endogenous skin regeneration from the aspects of structural and functional mimicry, physiological process regulation, and biophysical property design. Furthermore, novel techniques including in situ reprograming, flexible electronic skin, artificial intelligence, single-cell sequencing, and spatial transcriptomics, which have potential to contribute to the development of biomimetic biomaterials are highlighted. Finally, the prospects and challenges of further research and application of biomimetic biomaterials are discussed. This review provides reference to address the clinical problems of rapid and high-quality skin regeneration.

Ultra-Hydrophobic Gauze Driving Super-Haemostasis

Controlling bleeding by applying pressing cotton gauze is the most facile treatment in prehospital emergencies. However, the wettable nature of cotton fibers leads to unnecessary blood loss due to excessive blood absorption, inseparable adhesion-induced pain, and pliable to infection. Here, a kind of ultra-hydrophobic haemostatic anti-adhesive gauze whose surface is loaded with polydimethylsiloxane (PDMS) and hydrophobic-modified cellulose nanocrystals (CNCs), achieving a water contact angle of ≈160° is developed. It is demonstrated that the mechanism by which hydrophobic CNCs promote blood clotting is associated with their ability to activate coagulation factors, contributing to fibrin formation, and promoting platelet activation. The blood-restricting effect results from the low surface energy layer formed by PDMS and then the alkyl chains of hydrophobic CNCs are combined. The produced ultra-hydrophobic gauze resists blood flow and diffusion, decreases blood loss, is effortlessly peelable, and minimizes pathogen adhesion. Compared to the commercial cotton gauze, this gauze achieved effective haemostasis and antiadhesion by reducing blood loss by more than 90%, shortening haemostasis time by more than 75%, lowering peeling force by more than 90% and minifying bacterium attachment by more than 95%. This work presents promising applications in terms of prehospital first aid.

Blue Laser Triggered Hemostatic Peptide Hydrogel for Gastrointestinal Bleeding Treatment

In an emergency, nonvariceal upper gastrointestinal bleeding (NVUGIB), endoscopic hemostasis is considered the gold standard intervention. However, current endoscopic hemostasis is very challenging to manage bleeding in large-diameter or deep lesions highly prone to rebleeding risk. Herein, a novel hemostatic peptide hydrogel (HPH) is reported, consisting of a self-assembly peptide sequence CFLIVIGSIIVPGDGVPGDG (PFV) and gelatin methacryloyl (GelMA), which can be triggered by blue laser endoscopy (BLE) for nonvariceal upper gastrointestinal bleeding treatment without recurring bleeding concerns. Upon contact with GelMA solution, PFV immediately fibrillates into β-sheet nanofiber and solvent-induced self-assembly to form HPH gel. HPH nanofiber networks induced ultrafast coagulation by enveloping blood cells and activating platelets and coagulation factors even to the blood with coagulopathy. Besides its remarkable hemostatic performance in artery and liver injury models, HPH achieves instant bleeding management in porcine NVUGIB models within 60 s by preventing the rebleeding risk. This work demonstrates an extraordinary hemostatic agent for NVUGIB intervention by BLE for the first time, broadening potential application scenarios, including patients with coagulopathy and promising clinical prospects.

Silicone Bioadhesive with Shear-Stiffening Effect: Rate-Responsive Adhesion Behavior and Wound Dressing Application

Stimuli-responsive adhesives with on-demand adhesion capabilities are highly advantageous for facilitating wound healing. However, the triggering conditions of stimuli-responsive adhesives are cumbersome, even though some of them are detrimental to the adhesive and adjacent natural tissues. Herein, a novel stimuli-responsive adhesive called shear-stiffening adhesive (SSA) has been created by constructing a poly(diborosiloxane)-based silicone network for the first time, and SSA exhibits a rate-responsive adhesion behavior. Furthermore, we introduced bactericidal factors (PVP-I) into SSA and applied it as a wound dressing to promote the healing of infected wounds. Impressively, the wound dressing not only has excellent biocompatibility and long-term antibacterial properties but also performs well in accelerating wound healing. Therefore, this study provides a new strategy for the synthesis of intelligent adhesives with force rate response, which simplifies the triggering conditions by the force rate. Thus, SSA has great potential to be applied in wound management as an intelligent bioadhesive with on-demand adhesion performance.

Nature-Inspired Gelatin-Based Adhesive Hydrogel: A Rapid and User-Friendly Solution for Hemostatic Applications

Conventional hemostatic agents face challenges in achieving rapid hemostasis and effective tissue repair due to limited hemostatic scenarios, suboptimal efficacy, and inadequate adhesion to wet tissues. Drawing inspiration from nature-sourced materials, a gelatin-based adhesive hydrogel (AOT)  is designed, easily prepared and quick to form, driven by Schiff base and multiple hydrogen bonds for applications in arterial and liver bleeding models. AOT exhibits exceptional adhesion to wet tissues (48.67 ± 0.16 kPa) and displays superior hemostatic properties with reduced blood loss and hemostatic time compared to other hydrogels and conventional hemostatic materials. Moreover, AOT exhibits good biocompatibility and biodegradability. In summary, this easily prepared adhesive hydrogel has the potential to supplant traditional hemostatic agents, offering a novel approach to achieve swift sealing of hemostasis and facilitate wound healing and repair in broader application scenarios, owing to its unique advantages.

Platelet Vesicles Synergetic with Biosynthetic Cellulose Aerogels for Ultra-Fast Hemostasis and Wound Healing

Achieving hemostasis in penetrating and irregular wounds is challenging because the hemostasis factor cannot arrive at the bleeding site, and substantial bleeding will wash away the blood clot. Since the inherently gradual nature of blood clot formation takes time, a physical barrier is needed before blood clot formation. Herein, an ultra-light and shape memory hemostatic aerogel consisting of oxidized bacterial cellulose (OBC) and platelet extracellular vesicles (pVEs) is reported. The OBC-pVEs aerogel provides a physical barrier for the bleeding site by self-expansion, absorbing the liquid from blood to concentrate platelets and clotting factors and accelerating the clot formation by activating platelets and transforming fibrinogen into fibrin. In the rat liver and tail injury models, the blood loss decreases by 73% and 59%, and the bleeding times are reduced by 55% and 62%, respectively. OBC-pVEs aerogel has also been shown to accelerate wound healing. In conclusion, this work introduces an effective tool for treating deep, non-compressible, and irregular wounds and offers valuable strategies for trauma bleeding and wound treatment.

Silk fibroin-based hemostatic powders with instant and robust adhesion performance for sutureless sealing of gastrointestinal defects

Powder-based hemostatic technology has offered unprecedented opportunities in surgical sealing and repair of irregularly shaped and noncompressible wounds. Despite their routine use, existing clinical hemostatic powders are challenged either by poor mechanical properties or inadequate adhesion to bleeding tissues in biological environments. Here, inspired by the mussel foot proteins' fusion assembly strategy, a novel silk fibroin-based hemostatic powder (named as SF/PEG/TA) with instant and robust adhesion performance is developed. Upon absorbing interfacial liquids, the SF/PEG/TA powders rapidly swell into micro-gels and subsequently contact with each other to transform into a macroscopically homogeneous hydrogel in situ, strengthening its interfacial bonding with various substrates in fluidic environments. The in vitro and in vivo results show that the SF/PEG/TA powder possesses ease of use, good biocompatibility, strong antibacterial activities, and effective blood clotting abilities. The superior hemostatic sealing capability of the SF/PEG/TA powder is demonstrated in the rat liver, heart, and gastrointestinal injury models. Moreover, in vivo investigation of rat skin incision and gastrointestinal perforation models validates that the SF/PEG/TA powder promotes wound healing and tissue regeneration. Taken together, compared to existing clinical hemostatic powders, the proposed SF/PEG/TA powder with superior wound treatment capabilities has high potential for clinical hemostasis and emergency rescue.

Development of diffusive gradients in thin-films technique for monitoring polycyclic aromatic hydrocarbons in coastal waters

Addressing the challenge of accurately monitoring polycyclic aromatic hydrocarbons (PAHs) in aquatic systems, this study employed diffusive gradients in thin-films (DGT) technique to achieve methods detection limits as low as 0.02 ng L-1 to 0.05 ng L-1 through in situ preconcentration and determination of time-integrated concentrations. The efficacy of the developed DGT samplers was validated under diverse environmental conditions, demonstrating independence from factors such as pH (5.03-9.01), dissolved organic matter (0-20 mg L-1), and ionic strength (0.0001-0.6 M). Notably, the introduction of a novel theoretical approach to calculate diffusion coefficients based on solvent-accessible volume tailored for PAHs significantly enhanced the method's applicability, particularly for organic pollutants with low solubility. Field deployments in coastal zones validated the DGT method against traditional grab sampling, with findings advocating a 4 to 7-day optimal deployment duration for balancing sensitivity and mitigating lag time effects. These results provide a sophisticated, efficient solution to the persistent challenge of monitoring hydrophobic organic pollutants in aquatic environments, broadening the scope and applicability of DGT in environmental science and providing a robust tool for researchers.

Plant mucus-derived microgels: Blood-triggered gelation and strong hemostatic adhesion

Arrest of bleeding usually applies clotting agents to trigger coagulation procedures or adhesives to interrupt blood flow through sealing the vessel; however, the efficiency is compromised. Here, we propose a concept of integration of hemostasis and adhesion via yam mucus's microgels. The mucus microgels exhibit attractive attributes of hydrogel with uniform size and shape. Their shear-thinning, self-healing and strong adhesion make them feasible as injectable bioadhesion. Exceptionally, the blood can trigger the microgels' gelation with the outcome of super extensibility, which leads to the microgels a strong hemostatic agent. We also found a tight gel adhesive layer formed upon microgels' contacting the blood on the tissue, where there is the coagulation factor XIII triggered to form a dense three-dimensional fibrin meshwork. The generated structures show that the microgels look like hard balls in the dispersed phase into the blood-produced fibrin mesh of a soft net phase. Both phases work together for a super-extension gel. We demonstrated the microgels' fast adhesion and hemostasis in the livers and hearts of rabbits and mini pigs. The microgels also promoted wound healing with good biocompatibility and biodegradability.

Infant friendly adhesive film containing glucose for neonatal hypoglycemia

Neonatal hypoglycemia is a common disease in newborns, which can precipitate energy shortage and follow by irreversible brain and neurological injury. Herein, we present a novel approach for treating neonatal hypoglycemia involving an adhesive polyvinylpyrrolidone/gallic acid (PVP/GA) film loading glucose. The PVP/GA film with loose cross-linking can be obtained by mixing their ethanol solution and drying complex. When depositing this soft film onto wet tissue, it can absorb interfacial water to form a hydrogel with a rough surface, which facilitates tight contact between the hydrogel and tissue. Meanwhile, the functional groups in the hydrogels and tissues establish both covalent and non-covalent bonds, leading to robust bioadhesion. Moreover, the adhered PVP/GA hydrogel can be detached without damaging tissue as needed. Furthermore, the PVP/GA films exhibit excellent antibacterial properties and biocompatibility. Notably, these films effectively load glucose and deliver it to the sublingual tissue of newborn rabbits, showcasing a compelling therapeutic effect against neonatal hypoglycemia. The strengths of the PVP/GA film encompass excellent wet adhesion in the wet and highly dynamic environment of the oral cavity, on-demand detachment, antibacterial efficacy, biocompatibility, and straightforward preparation. Consequently, this innovative film holds promise for diverse biomedical applications, including but not limited to wearable devices, sealants, and drug delivery systems.

Wetting-enhanced adhesion of photo-polymerized supramolecular adhesives for both smooth and rough surfaces

Efficient interactions between an adhesive and a substrate surface at the molecular level are the basis for the formation of robust adhesion, which substantially relies on interfacial wetting. However, strong adhesives usually improve cohesion but compromise interfacial properties. Herein, we have reported a kind of robust supramolecular adhesive based on the outstanding mobility and interfacial wettability of adhesive precursors. In situ fast photopolymerization endows supramolecular adhesives with more outstanding adhesion for both smooth and rough surfaces in air and underwater in contrast to their counterparts from thermal polymerization. In addition to their low viscosity and high monomer concentration, supramolecular adhesive precursors without any organic solvents possess well-defined hydrogen bonding interactions. These superior properties consistently contribute to the wetting of the substrate and the formation of adhesive polymers with high molecular weights. This work highlights that enhancing interfacial wetting between an adhesive and a substrate is a promising route to achieving robust adhesion.

Low-impedance tissue-device interface using homogeneously conductive hydrogels chemically bonded to stretchable bioelectronics

Stretchable bioelectronics has notably contributed to the advancement of continuous health monitoring and point-of-care type health care. However, microscale nonconformal contact and locally dehydrated interface limit performance, especially in dynamic environments. Therefore, hydrogels can be a promising interfacial material for the stretchable bioelectronics due to their unique advantages including tissue-like softness, water-rich property, and biocompatibility. However, there are still practical challenges in terms of their electrical performance, material homogeneity, and monolithic integration with stretchable devices. Here, we report the synthesis of a homogeneously conductive polyacrylamide hydrogel with an exceptionally low impedance (~21 ohms) and a reasonably high conductivity (~24 S/cm) by incorporating polyaniline-decorated poly(3,4-ethylenedioxythiophene:polystyrene). We also establish robust adhesion (interfacial toughness: ~296.7 J/m2) and reliable integration between the conductive hydrogel and the stretchable device through on-device polymerization as well as covalent and hydrogen bonding. These strategies enable the fabrication of a stretchable multichannel sensor array for the high-quality on-skin impedance and pH measurements under in vitro and in vivo circumstances.

Glycopolymer-Based Antiswelling, Conductive, and Underwater Adhesive Hydrogels for Flexible Strain Sensor Application

With the fast development of soft electronics, underwater adhesion has become a highly desired feature for various sensing uses. Currently, most adhesive hydrogels are based on catechol-based structures, such as polydopamine, pyrogallol, and tannic acid, with very limited structural variety. Herein, a new type of glycopolymer-based underwater adhesive hydrogel has been prepared straightforwardly by random copolymerization of acrylic acid, acetyl-protected/unprotected glucose, and methacrylic anhydride in dimethyl sulfoxide (DMSO). By employing a DMSO-water solvent exchange strategy, the underwater adhesion was skillfully induced by the synergetic effects of hydrophobic aggregation and hydrogen bonding, leading to excellent adhesion behaviors on various surfaces, including pig skins, glasses, plastics, and metals, even after 5 days of storage in water. In addition, the underwater adhesive hydrogels with simple and low-cost protected/unprotected carbohydrate compositions showed good mechanical and rheological properties, together with cytocompatibility and antiswelling behavior in water, all of which are beneficial for underwater adhesions. In application as a flexible strain sensor, the adhesive hydrogel exhibited stable and reliable sensing ability for monitoring human motion in real time, suggesting great potential for intelligent equipment design.

Hydrophobic Polystyrene-Modified Gelatin Enhances Fast Hemostasis and Tissue Regeneration in Traumatic Brain Injury

Hemostatic sealant is required to deal with blood loss, especially in the scenario of traumatic brain injury (TBI), which presents high rates of morbidity and disability. Hemostasis in surgery with traditional gelatin-based sealants often leads to blood loss and other issues in brain because of the hydrophilic gelatin swelling. Herein, hydrophobic effects on the hemostasis in TBI surgery are studied by tuning the chain length of polystyrene (PS) onto methylacrylated gelatin (Gel-MA). The hydrophobicity and hemostatic efficiency can be tuned by controlling the length of PS groups. The platelet activation of modified sealants Gel-MA-2P, Gel-MA-P, and Gel-MA-0.5P is as much as 17.5, 9.1, and 2.1 times higher than Gel-MA in vitro. The hemostatic time of Gel-MA-2P, Gel-MA-P, and Gel-MA-0.5P groups is 2.0-, 1.6-, and 1.1-folds faster than that in Gel-MA group in TBI mice. Increased formation of fibrins and platelet aggregation can also be observed in vitro by scanning electron microscopy. Animal's mortality is lowered by 46%, neurologic deficiency is reduced by 1.5 times, and brain edema is attenuated by 10%. Protein expression is further investigated to exhibit toxic iron-related processes caused by delayed hemostasis and activation of platelets via PI3K/PKC-α signaling. The hydrophobic Gel-MA has the potential in hemostatic TBI and promotes nervous system recovery in brain with the potentials in clinics.

Diatom-Inspired Bionic Hydrophilic Polysaccharide Adhesive for Rapid Sealing Hemostasis

Diatoms are typical marine biofouling organisms that secrete extracellular polymers (EPS) to achieve strong underwater adhesion. Here, we report a diatom-inspired bionic hydrophilic polysaccharide adhesive composed of diatom biosilica (DB) and bletilla striata polysaccharide (BSP) for rapid sealing hemostasis. The hierarchical porous structure of DB with rich surface silanol groups provides a strong anchored interface effect for BSP, which can significantly enhance cross-linking density and interaction strength of the hydrophilic macromolecular network. BSP/DB adhesive offers 6 times greater mechanical strength and viscosity over BSP under different temperature conditions. The aggregation effect of DBs interface for BSP avoided the washout of BSP/DB adhesive during application in a wet environment before cross-linking occurs. This strengthened the adhesion ability of BSP/DB adhesive to biological tissue that brought out complete sealing hemostasis without blood loss in a rat liver injury model. The dry BSP/DB prepared by lyophilization inherited excellent clotting ability of BSP/DB adhesive, which could realize rapidly the cruor of anticoagulant whole blood within 1 min. The results of animal studies confirmed that dry BSP/DB exhibited superior hemostatic performance over silicate-based inorganic Quikclot, in terms of hemostatic rate, blood loss, dosage, and multiscroll wound closure.

Tunable backbone-degradable robust tissue adhesives via in situ radical ring-opening polymerization

Adhesives with both robust adhesion and tunable degradability are clinically and ecologically vital, but their fabrication remains a formidable challenge. Here we propose an in situ radical ring-opening polymerization (rROP) strategy to design a backbone-degradable robust adhesive (BDRA) in physiological environment. The hydrophobic cyclic ketene acetal and hydrophilic acrylate monomer mixture of the BDRA precursor allows it to effectively wet and penetrate substrates, subsequently forming a deep covalently interpenetrating network with a degradable backbone via redox-initiated in situ rROP. The resulting BDRAs show good adhesion strength on diverse materials and tissues (e.g., wet bone >16 MPa, and porcine skin >150 kPa), higher than that of commercial cyanoacrylate superglue (~4 MPa and 56 kPa). Moreover, the BDRAs have enhanced tunable degradability, mechanical modulus (100 kPa-10 GPa) and setting time (seconds-hours), and have good biocompatibility in vitro and in vivo. This family of BDRAs expands the scope of medical adhesive applications and offers an easy and environmentally friendly approach for engineering.

Preparation and Hemostatic Effect of Micro-Nanograded Porous Particles Doped with Dopamine-Based Water-Triggered Intelligent Composite Adhesives

The wet environment of water or tissue in bleeding wounds poses significant challenges to the adhesion performance of existing hemostatic adhesives. An intelligent composite adhesive prepared by doping starch-based silicate micro-nanograded porous particles (MBC@CMS) with dopamine-hyperbranched polymers (HPD, 7800 Mw) synthesized by the Michael addition reaction could be triggered by water to form a glue (MBC@CMS-HPD). The results indicated that MBC@CMS-HPD could still have adhesion properties under running water washing and water immersion and could effectively seal the water outlet. The results of the glue-forming mechanism showed that MBC@CMS-HPD had better wettability than water, which could eliminate water molecules at the wet adhesive surface. When contacted with water, the agglomeration of the HPD hydrophobic chain increases the exposure of the catechol group, and the relative atomic mass of the N element on the surface increases from 2.8 to 4.8%. The adhesion of MBC@CMS-HPD was enhanced and stable. MBC@CMS-HPD showed significant hemostasis effects in five injury bleeding models of Sprague-Dawley (SD) rats and New Zealand rabbits. Especially in the fatal femoral artery bleeding model of New Zealand rabbits, MBC@CMS-HPD reduced the amount of bleeding by 75% and shortened the bleeding time by 78% compared with the a-cyanoacrylate adhesives. The results of the coagulation mechanism showed that compared with HPD, MBC@CMS-HPD could activate both endogenous and exogenous coagulation pathways. Among them, after contact with blood, HPD formed a gel to close the blood outlet, and MBC@CMS entered the wound to activate the internal and external coagulation pathways. In addition, HPD and MBC@CMS had good histocompatibility and degradability, which has the potential to be applied to different wounds.

Scalable Underwater Adhesives with High-Strength, Long-Term, and Harsh-Environment Adhesion Enabled by Heterocyclic Chemistry

Developing scalable and high-performance underwater adhesives is important in various biomedical and industrial applications. However, despite massive efforts, the realization of such adhesives remains a challenging task, as mainly imposed by the difficulty in balancing the interfacial and bulk properties via an efficient way. Here, we report a facile yet effective strategy to construct a novel underwater adhesive with multiple advantaged performances by virtue of heterocyclic chemistry. This adhesive is designed with the cooperation of a heterocycle-based versatile adhesive functionality and an eco-friendly hydrophilic matrix with cross-linkable sites, which allows water absorption to destroy hydration layer, diverse molecular interactions to enhance interfacial adhesion, and abundant covalent crosslinks to strengthen bulk cohesion. Such a rational design endows the adhesive with strong underwater adhesion (up to 1.16 MPa for wood and 0.36 MPa for poly(tetrafluoroethylene) (PTFE)), long-term durability (maintaining pristine strength even after 4 months), and harsh-environment stability (salt, acidic/alkaline, low/high-temperature solutions). This strategy is also generic to derive more adhesive formulas, which offers a new direction for designing the next-generation underwater adhesives with high performance and scalability for practical applications.

Development of Organs-on-Chips and Their Impact on Precision Medicine and Advanced System Simulation

Drugs may undergo costly preclinical studies but still fail to demonstrate their efficacy in clinical trials, which makes it challenging to discover new drugs. Both in vitro and in vivo models are essential for disease research and therapeutic development. However, these models cannot simulate the physiological and pathological environment in the human body, resulting in limited drug detection and inaccurate disease modelling, failing to provide valid guidance for clinical application. Organs-on-chips (OCs) are devices that serve as a micro-physiological system or a tissue-on-a-chip; they provide accurate insights into certain functions and the pathophysiology of organs to precisely predict the safety and efficiency of drugs in the body. OCs are faster, more economical, and more precise. Thus, they are projected to become a crucial addition to, and a long-term replacement for, traditional preclinical cell cultures, animal studies, and even human clinical trials. This paper first outlines the nature of OCs and their significance, and then details their manufacturing-related materials and methodology. It also discusses applications of OCs in drug screening and disease modelling and treatment, and presents the future perspective of OCs.

Molecular architecture regulation for the design of instant and robust underwater adhesives

Development of underwater adhesives with instant and robust adhesion to diverse substrates remains challenging. A strategy taking the structural advantage of phenylalanine derivative, N-acryloyl phenylalanine (APA), is proposed to facilely prepare a series of underwater polymeric glue-type adhesives (UPGAs) through one-pot radical polymerization with commonly used hydrophilic vinyl monomers. The adjacent phenyl and carboxyl groups in APA realize the synergy between interfacial interactions and cohesion strength, by which the UPGAs could achieve instant (~5 seconds) and robust wet tissue adhesion strength (173 kilopascal). The polymers with varied hydrophobicity and substitutional groups as well as carboxyl and phenyl groups in separated components are designed to investigate the underwater adhesion mechanism. The universality of APA for the construction of UPGAs is also verified by the copolymerization with different hydrophilic monomers, and the applications of the UPGAs have been validated in diverse hemorrhage models and distinct substrates. Our work may give a promising solution to design potent underwater adhesives.

Achieving strong, stable, and durable underwater adhesives based on a simple and generic amino-acid-resembling design

Developing underwater adhesives is important in many applications. Despite extensive progress, achieving strong, stable, and durable underwater adhesion via a simple and effective way is still challenging, mainly due to the conflict between the interfacial and bulk properties. Here, we report a unique bio-inspired strategy to facilely construct superior underwater adhesives with desirable interfacial and bulk properties. For adhesive design, a hydrophilic backbone is utilized to quickly absorb water for effective dehydration, and a novel amino acid-resembling functional block is developed to provide versatile molecular interactions for high interfacial adhesion. Moreover, the conjunction of these two components enables the generation of abundant covalent crosslinks for robust bulk cohesion. Such a rational design allows the adhesive to present a boosted underwater adhesion (3.92 MPa to glass), remarkable durability (maintaining high strength after one month), and good stability in various harsh environments (pH, salt, high temperature, and organic solvents). This strategy is generic, allowing the derivation of more similar adhesive designs easily and triggering new thinking for designing bio-inspired adhesives and beyond.

A cyanoacrylate/triethyl citrate/nanosilica-based closure glue with wet-adhesion capability for treatment of superficial varicose veins

Varicose veins in legs are common in clinics. Currently, medical adhesive-based, minimally invasive endovenous occlusion is used to treat them. However, the most common cyanoacrylate medical adhesives do not perform well when used under blood/wet conditions. In particular, poor adhesion, short curing time, and high heat release greatly limit their clinical use. In this paper, we demonstrate the use of a composite system composed of butyl-cyanoacrylate, triethyl citrate, and nanosilica that exhibits a blood/wet-adhesion capability to serve as a new sealing glue. Hydrophobic triethyl citrate groups displace boundary waters while also protecting cyanoacrylate monomers from undergoing rapid polymerization. Nanosilica increases viscosity, which contributes to in situ extrusion molding and retention. An optimal formulation, FAL-006, exhibited good physical and chemical properties in vitro. The performed additional safety assays indicated that FAL-006 has good biocompatibility. The closure efficiency of FAL-006 in vivo was evaluated in both a rat abdominal aortic closure model and in a sheep lower limb venous closure model. Taken together, these results indicate that FAL-006 exhibits promising potential for use in clinical applications. Furthermore, this study provides a new strategy for designing underwater adhesive agents for additional clinical applications, and a strategy for constructing other biomaterials needed for use under wet conditions.

Reversible adhesives with controlled wrinkling patterns for programmable integration and discharging

Switchable and minimally invasive tissue adhesives have great potential for medical applications. However, on-demand adherence to and detachment from tissue surfaces remain difficult. We fabricated a switchable hydrogel film adhesive by designing pattern-tunable wrinkles to control adhesion. When adhered to a substrate, the compressive stress generated from the bilayer system leads to self-similar wrinkling patterns at short and long wavelengths, regulating the interfacial adhesion. To verify the concept and explore its application, we established a random skin flap model, which is a crucial strategy for repairing severe or large-scale wounds. Our hydrogel adhesive provides sufficient adhesion for tissue sealing and promotes neovascularization at the first stage, and then gradually detaches from the tissue while a dynamic wrinkling pattern transition happens. The gel film can be progressively ejected out from the side margins after host-guest integration. Our findings provide insights into tunable bioadhesion by manipulating the wrinkling pattern transition.

Room temperature nondestructive encapsulation via self-crosslinked fluorosilicone polymer enables damp heat-stable sustainable perovskite solar cells

Encapsulation engineering is an effective strategy to improve the stability of perovskite solar cells. However, current encapsulation materials are not suitable for lead-based devices because of their complex encapsulation processes, poor thermal management, and inefficient lead leakage suppression. In this work, we design a self-crosslinked fluorosilicone polymer gel, achieving nondestructive encapsulation at room temperature. Moreover, the proposed encapsulation strategy effectively promotes heat transfer and mitigates the potential impact of heat accumulation. As a result, the encapsulated devices maintain 98% of the normalized power conversion efficiency after 1000 h in the damp heat test and retain 95% of the normalized efficiency after 220 cycles in the thermal cycling test, satisfying the requirements of the International Electrotechnical Commission 61215 standard. The encapsulated devices also exhibit excellent lead leakage inhibition rates, 99% in the rain test and 98% in the immersion test, owing to excellent glass protection and strong coordination interaction. Our strategy provides a universal and integrated solution for achieving efficient, stable, and sustainable perovskite photovoltaics.

Povidone-iodine enhanced underwater tape

Realizing rapid and stable bonding under humid conditions has remained a challenge in adhesion science and wound dressing. In this study, polyacrylate-based underwater tape with water-enhanced adhesion and antimicrobial performance was designed and synthesized. Good underwater adhesion performance is achieved through the reasonable selection of comonomers, among which 4-hydroxybutyl acrylate (4-HBA) and isobornyl acrylate (IBOA) provide rich hydrogen bond interactions and a rigid side chain stable structure, respectively. The former effectively increases the interface strength between the tape and the substrate, while the latter ensures that the tape can maintain a good cohesion strength under water. Besides, povidone iodine (PVP-I₂) as a reinforcing filler and germicidal factor endows the tape with tunable mechanical properties and impressive antimicrobial abilities. This work provides a facile approach to prepare a wet adhesive for medical and industrial fields which can be used as wound dressing and underwater adhesive materials.

Underwater instant adhesion mechanism of self-assembled amphiphilic hemostatic granular hydrogel from Andrias davidianus skin secretion

The widespread use of biological tissue adhesives for tissue repair is limited by their weak adhesion in a wet environment. Herein, we report the wet adhesion mechanism of a dry granular natural bioadhesive from Andrias davidianus skin secretion (ADS). Once contacting water, ADS granules self-assemble to form a hydrophobic hydrogel strongly bonding to wet substrates in seconds. ADS showed higher shear adhesion than current commercial tissue adhesives and an impressive 72-h underwater adhesion strength of ∼47kPa on porcine skin tissue. The assembled hydrogel in water maintained a dissipation energy of ∼8 kJ/m³, comparable to the work density of muscle, exhibiting its robustness. Unlike catechol adhesion mechanism, ADS wet adhesion mechanism is attributed to water absorption by granules, and the unique equilibrium of protein hydrophobicity, hydrogen bonding, and ionic complexation. The in vivo adhesion study demonstrated its excellent wet adhesion and hemostasis performance in a rat hepatic and cardiac hemorrhage model.

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Dry granule adhesive of Andrias davidianus skin secretion build strong wet adhesion

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The granules absorb water and self-assemble to form a hydrophobic adhesive in seconds

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The adhesive showed 72-h underwater adhesion strength of ∼47kPa on porcine skin tissue

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Remarkable hemostasis effect was found on rat hepatic and cardiac hemorrhage model

Nature-Derived Okra Gel as Strong Hemostatic Bioadhesive in Human Blood, Liver, and Heart Trauma of Rabbits and Dogs

Bioadhesive performance can be compromised due to bleeding. Bleeding increases mortality. Adhesives with hemostatic function are of great significance. A sustainable and robust hemostatic bioadhesive from okra is reported. The adhesive strength reaches around three and six-fold higher than commercial fibrin on pigskin and glass, respectively. The okra gel presents high-pressure resistance and great underwater adhesive strength. In human blood experiments, the okra gel can activate platelets, enhance the adhesion of activated platelets, and release coagulation factors XI and XII. By forming a fast gel layer and closely adhering to the wound, it can quickly stop bleeding in the liver and heart of rabbits and dogs. Meanwhile, okra gel can cause platelet activation at the wound site and further strengthen its hemostatic performance. It is biocompatible, biodegradable, and can promote wound healing and shows potential as a sustainable bioadhesive, especially in the scenario of significant hemorrhage.

Liquid-infused microstructured bioadhesives halt non-compressible hemorrhage

Non-compressible hemorrhage is an unmet clinical challenge that accounts for high mortality in trauma. Rapid pressurized blood flows under hemorrhage impair the function and integrity of hemostatic agents and the adhesion of bioadhesive sealants. Here, we report the design and performance of bioinspired microstructured bioadhesives, formed with a macroporous tough xerogel infused with functional liquids. The xerogel can rapidly absorb interfacial fluids such as whole blood and promote blood clotting, while the infused liquids facilitate interfacial bonding, sealing, and antibacterial function. Their synergy enables the bioadhesives to form tough adhesion on ex vivo human and porcine tissues and diverse engineered surfaces without the need for compression, as well as on-demand instant removal and storage stability. We demonstrate a significantly improved hemostatic efficacy and biocompatibility in rats and pigs compared to non-structured counterparts and commercial products. This work opens new avenues for the development of bioadhesives and hemostatic sealants.

Non‐compressible wounds are a major source of high mortality in trauma victims. Here the authors report on the creation of xerogels impregnated with liquid adhesives which can rapidly absorb fluids promoting blood clotting while forming adhesions to tissue and demonstrate the xerogel in ex vivo and in vivo models.