Despite recent advance in bioinspired adhesives, achieving strong adhesion and sealing hemostasis in aqueous and blood environments is challenging. A hyperbranched polymer (HBP) with a hydrophobic backbone and hydrophilic adhesive catechol side branches is designed and synthesized based on Michael addition reaction of multi-vinyl monomers with dopamine. It is demonstrated that upon contacting water, the hydrophobic chains self-aggregate to form coacervates quickly, displacing water molecules on the adherent surface to trigger increased exposure of catechol groups and thus rapidly strong adhesion to diverse materials from low surface energy to high energy in various environments, such as deionized water, sea water, PBS, and a wide range of pH solutions (pH = 3 to 11) without use of any oxidant. Also, this HBP adhesive (HBPA) exhibits a robust adhesion to fractured bone, precluding the problem of mismatched surface energy and mechanical properties. The HBPA's adhesion is repeatable in a wet condition. Intriguingly, the HBPA is capable of gluing dissimilar materials with distinct properties. Importantly, introducing long alkylamine into this modular hyperbranched architecture contributes to formation of an injectable hemostatic sealant that can rapidly stop visceral bleeding, especially hemorrhage from deep wound.

Water-Triggered Hyperbranched Polymer Universal Adhesives: From Strong Underwater Adhesion to Rapid Sealing Hemostasis.

Marine animals, such as leptocephalus and jellyfish, can sense external stimuli and achieve optical camouflage in the aquatic environment. Fabricating an intelligent soft sensor that can mimic the capabilities of transparent marine animals and function underwater can enable transformative applications in various novel fields. However, previously reported soft sensors struggle to meet the requirements of adhesion, self-healing ability, optical transparency, and stable conductivity in the aquatic environment. Herein, high-performance ionogels by virtue of ion-dipole and ion-ion interactions between fluorine-rich poly(ionic liquid) and ionic liquid are designed. The hydrophobic dynamic viscoelastic networks provide excellent properties for ionogels, including optical transparency, adjustable mechanical properties, underwater self-healing ability, underwater adhesiveness, conductivity, and 3D printability. A mechanically compliant and visually invisible underwater soft sensor based on ionogel is developed. This sensor can achieve optical camouflage, human-body-motion detection, and barrier-free communication in the aquatic environment. A novel contactless sensing mechanism based on changing the electron transfer pathway is proposed. Several interesting functions, such as detection of water environment changes, recognition of objects, delivery of information, and even identification of human standing posture can be realized. Importantly, the ionogel sensor can avoid fatigue and physical damage in the sensing process.

Underwater Communication and Optical Camouflage Ionogels

Recent advances in wet adhesives: Adhesion mechanism, design principle and applications

A Janus Hydrogel Wet Adhesive for Internal Tissue Repair and Anti-Postoperative Adhesion

Dual adhesiveness to tissue and implant biomaterials and bioactivity to stimulate tissue regeneration are interesting properties for developing new generations of tissue-repairing hydrogels with potential new clinical applications. In this study, we developed a unique bioglass (BG)/oxidized sodium alginate (OSA) composite hydrogel with adipic acid dihydrazide (ADH)-modified γ-polyglutamic acid (γ-PGA) as the cross-linking agent, in which the BG plays a multifunctional role to endow the hydrogel‍ with both dual-adhesive and bioactive properties. On one hand, the BG could improve the tissue-bonding strength by providing an alkaline microenvironment to stimulate the bond formation between OSA and the amino groups on the surrounding tissues. On the other hand, BG endows the hydrogel‍ with adhesiveness to implantable materials by releasing Ca ions, which might chelate with the carboxyl groups of the hydrogel‍ matrix. In addition, the composite hydrogel‍ showed excellent bioactivity to promote vascularization and accelerate tissue regeneration. This study demonstrates that a multifunctional hydrogel‍ can be designed by utilizing the multifunctional ions released from silicate BG, and the BG/OSA hydrogel shows good potential as an adhesive and bioactive material for wound-healing applications. An inorganic material known as bioglass can help water-filled hydrogel polymers adhere to injuries and implants that require moist, protective environments. Composed of silica glass infused with calcium, silicate and phosphate ions, bioglass can help regenerate substances such as bone tissue while resisting rejection by the body’s immune system. Jiang Chang and colleagues from the Chinese Academy of Sciences in Shanghai now report that the ions in bioglass can accelerate the formation of bonds between tissue and hydrogels based on alginate, a polysaccharide extracted from seaweed. The team’s studies on live mice demonstrated that the enhanced adhesiveness of the new bioglass hydrogel led to better wound healing compared to stitching or conventional hydrogels. Calcium ion release was identified as a primary factor in helping the new composite stick to implants made from materials including silicone and titanium. The dual-adhesive and bioactive hydrogel ‍is designed and prepared for wound closure and wound healing by incorporation of bioglass into oxidized sodium alginate (OSA) hydrogel system, in which the multifunctional ions released from bioglass play a key role for the dual-adhessiveness to both tissues and implantable materials and bioactivity in enhancing angiogenesis during wound healing.

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A novel dual-adhesive and bioactive hydrogel activated by bioglass for wound healing

Underwater adhesion is crucial to many marine life forms living a sedentary lifestyle. Amongst them, mussel adhesion has been mostly studied, which inspires numerous investigations of 3,4-dihydroxyphenylalanine (DOPA)-based organic adhesives. In contrast, reef-building oysters represent another important “inorganic” strategy of marine molluscs for adhesion by generating biomineralized organic–inorganic adhesives, which is still rarely studied and no synthetic analogues have ever been reported so far. Here, a novel type of oyster-inspired organic–inorganic adhesive based on a biomineralized polyelectrolyte hydrogel is reported, which consists of polyacrylic acid physically cross-linked by very small amorphous calcium carbonate nanoparticles (<3 nm). The mineral-enhanced polyelectrolyte hydrogel adhesive is shown to be injectable, reusable, and optically clear upon curing in air. Moreover, comparable adhesion performance to DOPA-based adhesives is found for the hydrogel adhesive in both dry and wet conditio...

M. A. Cohen Stuart

Papers

Mineral-Enhanced Polyacrylic Acid Hydrogel as an Oyster-Inspired Organic–Inorganic Hybrid Adhesive