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Marine oil exploration is important yet greatly increases the risk of oil leakage, which will result in severe environment pollution and economic losses. It is an urgent need to develop effective underoil adhesives. However, realizing underoil adhesion is even harder than those underwater, due to the stubborn attachment of a highly viscous oil layer on target surface. Here, inspired by endocytosis, a tough gel tape composed of zwitterionic polymer network and zwitterionic surfactants is developed. The amphiphilic surfactants can form micelle to capture the oil droplets and transport them from the interface to gel via electrostatic attraction of polymer backbone, mimicking the endocytosis and achieving robust underoil adhesion. Benefiting from the oil‐resistance of polymer backbone, the gel further realizes a combination of i) long‐term adhesion with high durability, ii) repeated adhesion in oil, and iii) renewable adhesion efficiency after exhausted use. The tape exhibits an ultra‐high adhesive toughness of 2446.86 J m−2 to stainless steel in silicone oil after 30 days' oil‐exposure; such value of adhesive toughness surpasses many of those achieved in underwater adhesion and is greater than underoil adhesion performance of commercial tape. The strategy illustrated here will motivate the design of sustainable and efficient adhesives for wet environments. [ABSTRACT FROM AUTHOR]

Abstract Marine oil exploration is important yet greatly increases the risk of oil leakage, which will result in severe environment pollution and economic losses. It is an urgent need to develop effective underoil adhesives. However, realizing underoil adhesion is even harder than those underwater, due to the stubborn attachment of a highly viscous oil layer on target surface. Here, inspired by endocytosis, a tough gel tape composed of zwitterionic polymer network and zwitterionic surfactants is developed. The amphiphilic surfactants can form micelle to capture the oil droplets and transport them from the interface to gel via electrostatic attraction of polymer backbone, mimicking the endocytosis and achieving robust underoil adhesion. Benefiting from the oil‐resistance of polymer backbone, the gel further realizes a combination of i) long‐term adhesion with high durability, ii) repeated adhesion in oil, and iii) renewable adhesion efficiency after exhausted use. The tape exhibits an ultra‐high adhesive toughness of 2446.86 J m−2 to stainless steel in silicone oil after 30 days' oil‐exposure; such value of adhesive toughness surpasses many of those achieved in underwater adhesion and is greater than underoil adhesion performance of commercial tape. The strategy illustrated here will motivate the design of sustainable and efficient adhesives for wet environments.

The application of meshes in surgery is severely limited by complications associated with the non-absorbable nature, the lack of bioactivities, and the need of sutures and/or staples to fix meshes on tissues. In this contribution, a self-adhesive hydrogel-mesh composite (HMC) with biodegradability and multiple bioactivities was developed to address these issues and meet the clinical requirements. In this HMC system, GelMA hydrogel network was first macrotopological entangled with the fibers of a natural small intestinal submucosa (SIS) meshes, and then strengthened by soaking in a multi-functional H-bond provider (i.e., tannic acid, TA) solution to form the G/SIS-TA composite. The pyrogallol groups of the TA molecules endow G/SIS-TA with excellent wet adhesiveness (shear strength: ∼60 kPa), antioxidant, and antibacterial ability. The G/SIS-TA was also found to exhibit excellent biodegradability, biocompatibility, and immunoregulatory activity. The G/SIS-TA significantly decrease the bacterial burden in a mouse peritonitis infection model and promote the healing of infected full-thickness rat skin wounds in vivo. This work not only reports a novel SIS-based HMC which was efficient in treating infected wounds, but also offers an innovative strategy of the development of self-adhesive bio-patch for various biomedical applications.

Hydrogel patch-based stem cell transplantation and microenvironment-regulating drug delivery strategy is promising for the treatment of myocardial infarction (MI). However, the low retention of cells and drugs limits their therapeutic efficacies. Here, we propose a prefixed sponge carpet strategy, that is, aldehyde-dextran sponge (ODS) loading anti-oxidative/autophagy-regulating molecular capsules of 2-hydroxy-β-cyclodextrin@resveratrol (HP-β-CD@Res) is first bonded to the rat's heart via capillary removal of interfacial water from the tissue surface, and the subsequent Schiff base reaction between the aldehyde groups on ODS and amino groups on myocardium tissue. Then, an aqueous biocompatible hydrazided hyaluronic acid (HHA) solution encapsulating mesenchymal stem cells (MSCs) is impregnated into the anchored carpet to form HHA@ODS@HP-β-CD@Res hydrogel in situ via click reaction, thus prolonging the in vivo retention time of therapeutic drug and cells. Importantly, the HHA added to outer surface consumes the remaining aldehydes to contribute to nonsticky top surface, avoiding adhesion to other tissues. The embedded HP-β-CD@Res molecular capsules with antioxidant and autophagy regulation bioactivities can considerably improve cardiac microenvironment, reduce cardiomyocyte apoptosis, and enhance the survival of transplanted MSCs, thereby promoting cardiac repair by facilitating angiogenesis and reducing cardiac fibrosis.

Oral submucous fibrosis is a chronic, inflammatory and potentially malignant oral disease. Local delivery of triamcinolone to lesion site is a commonly used therapy. The existing methods for local drug delivery include topical administration and submucosal injection. However, in the wet and dynamic oral microenvironment, these methods have drawbacks such as limited drug delivery efficiency and injection pain. Therefore, it is urgently needed to develop an alternative local drug delivery system with high efficiency and painlessness. Inspired by the structure of band-aid, this study proposed a novel double-layered mucoadhesive microneedle patch for transmucosal drug delivery. The patch consisted of a mucoadhesive silk fibroin/tannic acid top-layer and a silk fibroin microneedle under-layer. When applying the annealing condition for the medium content of β-sheets of silk fibroin, the microneedles in under-layer displayed both superior morphology and mechanical property. The mechanical strength of per needle (0.071N) was sufficient to penetrate the oral mucosa. Sequentially, the gelation efficiency of silk fibroin and tannic acid in top-layer was maximized as the weight ratio of tannic acid to silk fibroin reached 5:1. Moreover, in vitro results demonstrated the double-layered patch possessed undetectable cytotoxicity. The sustained release of triamcinolone was observed from the double-layered patch for at least 7 days. Furthermore, compared with other commercial buccal patches, the double-layered patch exhibited an enhanced wet adhesion strength of 37.74 kPa. In addition, ex vivo mucosal tissue penetration experiment confirmed that the double-layered patch could reach the lamina propria, ensuring effective drug delivery to the lesion site of oral submucous fibrosis. These results illustrate the promising potential of the drug-loaded mucoadhesive microneedle patch for the treatment of oral submucous fibrosis.

Wet adhesives from poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate), castor oil, and styrene butadiene rubber were prepared at variable compositions. These components were exposed to a certain range of irradiation dose for γ-rays. Wet adhesives were characterized by adhesion force, Fourier transform infrared, thermogravimetric analysis and derivative thermal gravimetric, gel permeation chromatography, proton nuclear magnetic resonance spectroscopy and scan electron microscopy. Results declared that dose and composition have significant effect on features of wet adhesives. Further, the adhesion force and thermal stability of wet adhesives improved by increasing the irradiation dose. Moreover, the adhesion force reached ~ 690 (kPa). The analysis of gel permeation chromatography showed that molecular weight of wet adhesive 48,921 (g/mol). The wet adhesives were exploited to trap reptiles and rodents. Through the results, it can be observed that the wet adhesives had good efficiency for trapping the reptiles and rodents. The results showed that the best sample of wet adhesive was from 98% of [poly (vinyl butyral-co-vinyl alcohol-co-vinyl (10%)/castor oil (90%))] to [2% of styrene butadiene rubber] at 30 kGy In conclusion, this study referred that this type of wet adhesive has an excellent ability to adhere and trap of reptiles and rodents such as geckos and mice respectively. Consequently, these wet adhesives could be utilized in pilot scale. [ABSTRACT FROM AUTHOR]

Oral ulcers are one of the most common oral diseases in clinical practice. Its etiology is complex and varied. Due to the dynamic nature of the oral environment, the wound surface is painful due to contact and wear, which seriously affects the quality of life of patients. Oral ulcers are often treated with topical drug therapy. Studies have shown that functional hydrogels play a positive role in promoting wound healing, showing unique advantages in wound dressings. In this paper, the causes and healing characteristics of oral ulcers are discussed in depth, and then the common treatment methods for oral ulcers are summarized and compared. Finally, the potential of functional hydrogels in the treatment of oral ulcers is discussed and projected through a review of the literature in recent years., (© 2024 Wiley Periodicals LLC.)

Instant and strong adhesion to underwater adherends is a big challenge due to the continuous interference of water. Mussel foot protein-bioinspired catechol-based adhesives have garnered great interest in addressing this issue. Herein, a novel self-made catecholic compound with a long aliphatic chain was utilized to prepare thin (∼0.07 mm) and optically transparent (>80%) wet/underwater adhesive tapes by UV-initiated polymerization. Its adhesion activity was water-triggered, fast (<1 min), and strong (adhesion strength to porcine skin: ∼1.99 MPa; interfacial toughness: ∼610 J/m 2 , burst pressure: ∼1950 mmHg). The effect of the catechol/phenol group and positively charged moiety on the wet/underwater adhesion to abiotic/biotic substrates was investigated. On the wet/underwater adherends, the tape with catechol groups presented much higher interfacial toughness, adhesion strength, and burst pressure than the analogous tape with phenol groups. The tape with both the catechol group and cationic polyelectrolyte chitosan had a more impressive improvement in its adhesion to wet/underwater biological tissues than to abiotic substrates. Therefore, catechol and a positive moiety in the tape would synergistically enhance its wet/underwater adhesion to various substrates, especially to biological tissues. The instant, strong, and noncytotoxic tape may provide applications in underwater adhesion for sealing and wound closure.

The healing of a wound under tension (hereafter, "tension wound") often coincides with the development of hypertrophic scars in clinical settings. Currently, compress bandages offer a potential alternative for the healing of tension wounds; however, their application in surgery is limited due to their prefabricated patch form. To overcome this, a tension-shielding hydrogel system was designed using photocurable catechol-grafted hyaluronic acid and tannic-acid silver nanoparticles (hereafter, "HTA system"). The hydrogel exhibited tension-shielding capacity, reducing wound tension via shape-fixation and ultimately reducing scar formation. The HTA hydrogel exhibited superior photothermal antibacterial efficacy, self-healing properties, and effective dissipation of energy, thereby promoting tissue regeneration. The hydrogel significantly inhibited the mechanotransduction pathway, thus preventing Engrailed-1 activation and reducing the fibrotic response. The HTA hydrogel system, therefore, provides a treatment strategy for tension wounds, burn wounds and other wounds that are prone to form hypertrophic scars via creating a tension-free local environment. STATEMENT OF SIGNIFICANCE: In our study, we presented a wound-dressing hydrogel system (HTA) that exhibit shape-fixing capacity in tension wound model. Here, we designed and modified a tension regulator, applied it to mice, and furthermore, established a tension wound model in mice with adjustable tension. Outcomes showed that the HTA hydrogel system can effectively form a shape-fixed environment on tension wounds and dynamic wounds, thus promoting scarless healing. Additionally, HTA performs injectability, rapid crosslinking, biocompatibility, wet adhesion, hemostasis and photothermal antibacterial properties. We believe this research has various potential clinical applications, including scarless-healing in tension wounds, treatment of acute bleeding, treatment of infected wounds, and even internal organ repair., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

[Display omitted] • A novel self-adhesive hydrogel-mesh composite, i.e., G/SIS-TA is developed by combining SIS meshes, GelMA, and tannic acid. • G/SIS-TA can strongly adhere to wet porcine skin (shear strength: ∼60 kPa) with notable biodegradability. • G/SIS-TA shows a remarkable biocompatibility, antioxidant, antibacterial properties and immunoregulatory activity. • G/SIS-TA can reduce bacterial burden in mouse peritonitis infection model, and enhance wound healing in infected rat full-thickness wound model. The application of meshes in surgery is severely limited by complications associated with the non-absorbable nature, the lack of bioactivities, and the need of sutures and/or staples to fix meshes on tissues. In this contribution, a self-adhesive hydrogel-mesh composite (HMC) with biodegradability and multiple bioactivities was developed to address these issues and meet the clinical requirements. In this HMC system, GelMA hydrogel network was first macrotopological entangled with the fibers of a natural small intestinal submucosa (SIS) meshes, and then strengthened by soaking in a multi-functional H-bond provider (i.e., tannic acid, TA) solution to form the G/SIS-TA composite. The pyrogallol groups of the TA molecules endow G/SIS-TA with excellent wet adhesiveness (shear strength: ∼60 kPa), antioxidant, and antibacterial ability. The G/SIS-TA was also found to exhibit excellent biodegradability, biocompatibility, and immunoregulatory activity. The G/SIS-TA significantly decrease the bacterial burden in a mouse peritonitis infection model and promote the healing of infected full-thickness rat skin wounds in vivo. This work not only reports a novel SIS-based HMC which was efficient in treating infected wounds, but also offers an innovative strategy of the development of self-adhesive bio-patch for various biomedical applications. [ABSTRACT FROM AUTHOR]

Tissue adhesives have been widely used in biomedical applications. However, the presence of a hydrated layer on the surface of wet tissue severely hinders their adhesion capacities, resulting in ineffective wound treatment. To address this issue, a dry particle dressing (plas@SF/tann- hydro -pwd) capable of removing the hydrated layer and converting in situ to bioadhesives (plas@SF/tann- hydro -gel) was fabricated via simple physical mixing based on the hydrophobic-hydrogen bonding synergistic effect and Schiff-base reaction. It was found that the plas@SF/tann- hydro -gel bioadhesive, which was changed from plas@SF/tann- hydro -pwd dressing by adsorption of water, exhibited good wet adhesion to diverse biological tissues. In addition, the wet adhesion qualities of the plas@SF/tann- hydro -gel adhesive was studied under a variety of demanding conditions, including a wide range of temperatures, varying pH levels, highly concentrated salt solutions, and simulated fluids. Experiments on animals had showed that the adhesive plas@SF/tann- hydro -gel has superior wet adhesion qualities and superior wound healing properties compared to the commercial product Tegaderm™. This study develops a new wet-adhesion technique employing dry particle dressing to eliminate the hydrated layer over wet tissues for the in situ creation of gel bioadhesives for wound healing. [ABSTRACT FROM AUTHOR]

Adhesion on wet surface is of significance but remains challenging. Despite large steps forward in wet adhesives, they suffer from complicated preparation procedures and unbalanced properties. Herein, we develop a simple one-pot approach to fabricate a supramolecular adhesive with simultaneous enhancement in wet adhesion and mechanical toughness, which is achieved via citric acid (CA)-regulated supramolecular network of N-hydroxy succinimide (NHS) grafted polyacrylic acid chain and gelatin. CA not only reinforces supramolecular network by forming abundant hydrogen bonds, but also repels the NHS groups exposed outward to increase the opportunity for bonding with the target surface. The resultant adhesive shows fast and robust wet adhesion, high mechanical strength and elongation, as well as good biocompatibility. Such features enable the resultant adhesive with high potential in a variety of biomedical settings, such as tissue adhesion, sealant, and skin-adhesive strain sensor. This study opens a new avenue for the development of advanced bioadhesives, holding broad clinical application prospects. • The adhesive was fabricated with citric-acid-regulated supramolecular network. • Wet adhesion and mechanical properties were enhanced after citric acid addition. • The adhesive poses high potential in a variety of biomedical settings. • It opens a new avenue for the development of advanced bioadhesives. [ABSTRACT FROM AUTHOR]

Oral submucous fibrosis is a chronic, inflammatory and potentially malignant oral disease. Local delivery of triamcinolone to lesion site is a commonly used therapy. The existing methods for local drug delivery include topical administration and submucosal injection. However, in the wet and dynamic oral microenvironment, these methods have drawbacks such as limited drug delivery efficiency and injection pain. Therefore, it is urgently needed to develop an alternative local drug delivery system with high efficiency and painlessness. Inspired by the structure of band-aid, this study proposed a novel double-layered mucoadhesive microneedle patch for transmucosal drug delivery. The patch consisted of a mucoadhesive silk fibroin/tannic acid top-layer and a silk fibroin microneedle under-layer. When applying the annealing condition for the medium content of β-sheets of silk fibroin, the microneedles in under-layer displayed both superior morphology and mechanical property. The mechanical strength of per needle (0.071N) was sufficient to penetrate the oral mucosa. Sequentially, the gelation efficiency of silk fibroin and tannic acid in top-layer was maximized as the weight ratio of tannic acid to silk fibroin reached 5:1. Moreover, in vitro results demonstrated the double-layered patch possessed undetectable cytotoxicity. The sustained release of triamcinolone was observed from the double-layered patch for at least 7 days. Furthermore, compared with other commercial buccal patches, the double-layered patch exhibited an enhanced wet adhesion strength of 37.74 kPa. In addition, ex vivo mucosal tissue penetration experiment confirmed that the double-layered patch could reach the lamina propria, ensuring effective drug delivery to the lesion site of oral submucous fibrosis. These results illustrate the promising potential of the drug-loaded mucoadhesive microneedle patch for the treatment of oral submucous fibrosis., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Cheng, Yang, Liao, Yi, Zhou, Dai, Liu and Liu.)

Double network hydrogel with excellent mechanical properties is a polymer material composed of interpenetrating polymer network structure. In this study, poly(acrylamide-co-acrylic acid)/sodium alginate (P(AAM-co-AAC)/SA) hydrogels were rapidly prepared by photopolymerization under green LED irradiation. Subsequently, poly(acrylamide-co-acrylic acid)/sodium alginate/tannic acid (P(AAM-co-AAC)/SA/TA) hydrogels were prepared by immersion method. The morphology, mechanical properties, the wet adhension ability and swelling behaviour morphology of P(AAM-co-AAC)/SA/TA hydrogels were studied in detail. The double network hydrogel has excellent mechanical properties, with the elongation at break and tensile strength reaching 862% and 0.77 MPa respectively. The hydrogel with tannic acid showed excellent adhesion, wet adhesion and anti-swelling capability. Our research provides a more efficient and environmentally friendly preparation method for hydrogels used in wet environment. [Display omitted] • Hydrogel with excellent mechanical properties was rapidly prepared by photopolymerization under green LED irradiation. • By adding tannic acid, the hydrogel with adhesive property was obtained. • Hydrogel has adhesion in wet environment and maintains certain mechanical properties. [ABSTRACT FROM AUTHOR]

• Glycine was modified and combined with HAp to form an adhesive layer with tissues. • Modified MEGG layer can avoid undifferentiated adhesion and secondary damage. • The Janus patches exhibited asymmetric adhesion and instant wet adhesion. • The Janus patches had an effective treatment and repair effect on OUs. Oral ulcers (OUs) are the most common lesions of the oral mucosa and severely reduce patients' quality of life. Several types of patches for the self-treatment of OU have been developed, which have partially alleviated the problems caused by OUs. However, their wide application is limited by a few factors, including the suboptimal adhesion to the wound in the complex oral environment and the discoloration of the degraded products. Herein, an ideal Janus patch for the accelerated treatment and cure of OUs, comprising bifunctional sides, was designed. Inspired by the composition and hybrid adhesive mechanism of barnacles, glycine was modified and combined with hydroxyapatite nanoparticles (HAp) to create an adhesive layer that would form abundant covalent bonds with tissues; the HAp act as a bridge to bond polymer chains mimicking the organic–inorganic hybrid mechanism of barnacles, achieving analogous instant wet adhesion. Additionally, double bond-modified gellan gum served as a slippery layer to avoid undifferentiated adhesion and secondary damage. When applied to rat OUs, the Janus patch exhibited instant wet adhesion, with the longest residue time, overcoming the limitations of commercial products, and withstood chewing and biting and other mouth movements, thus achieving an excellent therapeutic efficacy. [ABSTRACT FROM AUTHOR]

Hydrogels with robust wet adhesion are desirable for applications in aqueous environments. Wet adhesion arising from synergy between hydrophobic and catechol components in mussel foot proteins has been highlighted. However, optimizing hydrogels with multiple components is challenging because of their complex structure-property relationships. Herein, high-throughput screening of a series of hydrophobic alkyl monomers and adhesive catechol derivatives was used to systematically develop wet adhesive hydrogels. Short alkyl chains promote wet adhesion by repelling water at the adhesive interface, whereas long alkyl chains form strong hydrophobic interactions inside the hydrogel network that impede or dissipate energy for wet adhesion. The optimized wet adhesive hydrogel, containing short alkyl chain, was applied for rapid hemostasis and wound healing because of the synergistic effect of catechol and alkyl groups and its immunomodulation ability, which is revealed through a transcriptomic analysis. Conductive nanocomponents were incorporated into the optimized hydrogel to produce a wearable device, which was used for continuous monitoring human electrocardiogram (ECG) during swimming, and in situ epicardial ECG on a porcine living and beating heart. This study demonstrated an efficient and generalized molecular design strategy for multifunctional wet adhesive hydrogels.

Noninvasive electrophysiological signal monitoring is significant for health care and scientific research. The simultaneous achievement of wet adhesion, stretchability, breathability, and low contact impedance is highly recommended in the epidermal electrode but still challenging. In this work, a monolayer porous film electrode with a pore size and wall thickness of less than ∼10 μm is fabricated via the breath figure method (BFM) and metal sputtering, and it was subsequently applied using epidermal electrophysiological monitoring. The ultrahigh permeability is comparable to the naked skin because the through holes of the monolayer porous film match well with the pores on human skin. The stretchability of 50% is realized with the combination of Au microcrack and the monolayer porous structure. The wet adhesion of 0.17 N/cm is established on the chemical bonding between the electrode and the epidermis. The contact impedance is comparable with the gold standard Ag/AgCl gel electrode, especially after sweating. Stable and precise electrophysiological signals are measured. Especially, the perspiration resistance of the monolayer porous film outperforms that of the gel electrode. The monolayer porous structure provides a new avenue to improve the breathability of the epidermal electronics.

Hydrogel patch-based stem cell transplantation and microenvironment-regulating drug delivery strategy is promising for the treatment of myocardial infarction (MI). However, the low retention of cells and drugs limits their therapeutic efficacies. Here, we propose a prefixed sponge carpet strategy, that is, aldehyde-dextran sponge (ODS) loading anti-oxidative/autophagy-regulating molecular capsules of 2-hydroxy-β-cyclodextrin@resveratrol (HP-β-CD@Res) is first bonded to the rat's heart via capillary removal of interfacial water from the tissue surface, and the subsequent Schiff base reaction between the aldehyde groups on ODS and amino groups on myocardium tissue. Then, an aqueous biocompatible hydrazided hyaluronic acid (HHA) solution encapsulating mesenchymal stem cells (MSCs) is impregnated into the anchored carpet to form HHA@ODS@HP-β-CD@Res hydrogel in situ via click reaction, thus prolonging the in vivo retention time of therapeutic drug and cells. Importantly, the HHA added to outer surface consumes the remaining aldehydes to contribute to nonsticky top surface, avoiding adhesion to other tissues. The embedded HP-β-CD@Res molecular capsules with antioxidant and autophagy regulation bioactivities can considerably improve cardiac microenvironment, reduce cardiomyocyte apoptosis, and enhance the survival of transplanted MSCs, thereby promoting cardiac repair by facilitating angiogenesis and reducing cardiac fibrosis., Competing Interests: The authors declare no conflicts of interest., (© 2022 The Authors.)

Achieving strong adhesion between the interfaces of similar and dissimilar materials is highly desirable in various fields. However, the adhesion of common adhesives is diminished and even eliminated upon contact with water, because it prevents direct contact between the adhesive and adherend substrate and competes with the substrate surface groups to interact with the adhesive functional groups. So far, numerous mussel-inspired catechol-based wet adhesives have been reported, opening a pathway for the development of wet adhesives. However, catechol is sensitive to pH, oxidation, and temperature, which limit its adhesion capability and application convenience. To overcome these limitations, many non-catechol-based adhesives have been explored and prepared in recent years. This review systematically summarizes and discusses several types of wet adhesives starting with the most extensively investigated catechol-based wet adhesives, followed by a focus on non-catechol-based wet adhesives that adhere though hydrogen bonding, electrostatic interactions, dynamic covalent bonding, topological entanglement, and dry polymer crosslinking, as well as by mimicking adhesion in organisms. Finally, wet adhesives that can debond on demand are discussed. This review describes the opportunities and challenges encountered in the design and development of wet adhesives with more advanced adhesion performances and application prospects. [Display omitted] [ABSTRACT FROM AUTHOR]

Healing soft-tissue wounds with an irregular, complicated topography in a bleeding environment demands the development of a dressing that is wet-adhesive, haemostatic, and antibacterial. To meet this unmet demand, we designed a flexible nanosheet (~77 nm thick) made of two layers, one is the antibacterial and haemostatic gelatin modified with dopamine (DA) and antimicrobial peptide (AMP) and mixed with Ca 2+ ions as coagulation factors, and another is the mechanically strong polycaprolactone (PCL). This flexible nanosheet exhibited robust mechanical strength, continuous and effective adhesion to a topographically irregular tissue surface under a wet condition, and a high platelet adhesion capacity. Moreover, the nanosheet presented a significantly reduced clotting time of 4 min and a high bactericidal rate of nearly 100%. An in vivo evaluation of the nanosheet using both murine dorsal skin and liver models further revealed that the nanosheet could successfully seal and heal the wounds in a bleeding environment, efficiently control haemorrhaging, and exert an excellent antibacterial effect in two weeks. Our work suggests that this nanosheet holds great promise in healing the bleeding soft-tissue wounds for treating acute trauma., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Weak polyelectrolyte multilayers (PEMs) assembled by the layer-by-layer method are known to become tacky upon contact with water and behave as a viscoelastic fluid, but this wet adhesive property and how it can be modified by external stimuli has not yet been fully explored. We present here a study on the wet adhesive performance of PEMs consisting of branched poly(ethylene imine) and poly(acrylic acid) under controlled conditions (e.g., pH, type of salt, and ionic strength) using a 90° peel test. The multilayers demonstrate stick-slip behavior and fail cohesively in nearly all cases. The peel force is the highest at neutral pH, and it decreases in both acidic/basic environments because of inhibited polyelectrolyte mobility. The addition of salts with various metal ions generally reduces the peel force, and this effect tracks with the ionic strength. When transition metal ions are used, their ability to form coordination bonds increases the peel force, with two exceptions (Cu 2+ and Zn 2+ ). With a transition metal ion such as Fe 3+ , the peel force first increases as a function of the concentration and then eventually decreases. The peel force increases proportionally to the peel rate. The films are also characterized via zeta potential (when assembled onto colloidal particles) and shear rheometry. This work provides insight into both the wet adhesive properties of PEMs and the interactions between PEMs and metal ions.