Controlling Spatiotemporal Mechanics of Supramolecular Hydrogel Networks with Highly Branched Cucurbit[8]uril Polyrotaxanes

Attempts to rationally tune the macroscopic mechanical performance of supramolecular hydrogel networks through noncovalent molecular interactions have led to a wide variety of supramolecular materials with desirable functions. While the viscoelastic properties are dominated by temporal hierarchy (crosslinking kinetics), direct mechanistic studies on spatiotemporal control of supramolecular hydrogel networks, based on host–guest chemistry, have not yet been established. Here, supramolecular hydrogel networks assembled from highly branched cucurbit[8]uril‐threaded polyrotaxanes (HBP‐CB[8]) and naphthyl‐functionalized hydroxyethyl cellulose (HECNp) are reported, exploiting the CB[8] host–guest complexation. Mechanically locking CB[8] host molecules onto a highly branched hydrophilic polymer backbone, through selective binary complexation with viologen derivatives, dramatically increases the solubility of CB[8]. Additionally, the branched architecture enables tuning of material dynamics of the supramolecular hydrogel networks via both topological (spatial hierarchy) and kinetic (temporal hierarchy) control. Relationship between macroscopic properties (time‐ and temperature‐dependent rheological properties, thermal stability, and reversibility), spatiotemporal hierarchy, and chain dynamics of the highly branched polyrotaxane hydrogel networks is investigated in detail. Such kind of tuning of material mechanics through spatiotemporal hierarchy improves our understanding of the challenging relationship between design of supramolecular polymeric materials and their complex viscoelasticity, and also highlights a facile strategy to engineer dynamic supramolecular materials.     

Healable,Stable and Stiff Hydrogels: Combining Conflicting Properties Using Dynamic and Selective Three‐Component Recognition with Reinforcing Cellulose Nanorods

Nanocomposite hydrogels are prepared combining polymer brush‐modified ‘hard’ cellulose nanocrystals (CNC) and ‘soft’ polymeric domains, and bound together by cucurbit[8]uril (CB[8]) supramolecular crosslinks, which allow dynamic host–guest interactions as well as selective and simultaneous binding of two guests, i.e., methyl viologen (the first guest) and naphthyl units (the second guest). CNCs are mechanically strong colloidal rods with nanometer‐scale lateral dimensions, which are functionalized by surface‐initiated atom transfer radical polymerization to yield a dense set of methacrylate polymer brushes bearing naphthyl units. They can then be non‐covalently cross‐linked through simple addition of poly(vinyl alcohol) polymers containing pendant viologen units as well as CB[8]s in aqueous media. The resulting supramolecular nanocomposite hydrogels combine three important criteria: high storage modulus (G′ > 10 kPa), rapid sol–gel transition (<6 s), and rapid self‐healing even upon aging for several months, as driven by balanced colloidal reinforcement as well as the selectivity and dynamics of the CB[8] three‐component supramolecular interactions. Such a new combination of properties for stiff and self‐healing hydrogel materials suggests new approaches for advanced dynamic materials from renewable sources.     

Patterned Arrays of Supramolecular Microcapsules

Micropatterning of hydrogel has brought innovative outcomes in fundamental and applied material sciences. Previous approaches have mainly been dedicated to fabricate arrays of bulk hydrogel beads, which have inherent challenges including loading ability, scalability, specificity, and versatility. Here, a methodology is presented to create hollow microcapsule arrays from sessile microdroplets. The difference in wettability between hydrophilic and hydrophobic surfaces enables self‐partitioning of liquid into microdroplet arrays, serving as microreservoirs to load complementarily functionalized host–guest polymers, cucurbit[8]uril‐threaded highly branched polyrotaxanes (HBP‐CB[8]) and naphthyl‐functionalized hydroxyethyl cellulose (HEC‐Np). The interfacial dynamic complexation between positively charged HBP‐CB[8] and HEC‐Np occurs in the presence of negatively charged surfactants, resulting in condensed supramolecular hydrogel skins. The hydrogel microcapsules are uniform in size and are developed to encapsulate target cargos in a robust and well‐defined manner. Moreover, the microcapsule substrates are further used for surface enhanced Raman spectroscopy sensing upon loading of gold nanoparticles. This facile assembly of microcapsule arrays has potential applications in controlled cargo delivery, bio‐sensing, high‐throughput analysis, and sorting.     

Light‐Harvesting Fluorescent Supramolecular Block Copolymers Based on Cyanostilbene Derivatives and Cucurbit[8]urils in Aqueous Solution

A novel system of light‐harvesting supramolecular block copolymers (SBCPs) in water is demonstrated. To realize cucurbit[8]uril (CB[8])‐based SBCPs generating artificial light‐harvesting in water, finely color‐tuned supramolecular homopolymers (SHPs) comprising CB[8] host and different cyanostilbene guests (named as B , G , Y , and R ) emitting blue, green, yellow, and red fluorescence are first synthesized and characterized, respectively. Light‐harvesting SBCPs with mixed guest emitters are then simply produced by mixing blue and red‐emitting SHPs according to the dynamic host–guest exchange interaction. The light‐harvesting SBCPs show highly efficient energy transfer from B (donor D) to R (acceptor A) attributed to the D/A proximity and parallel orientation of their transition dipoles secured in the block copolymer structure. It is comprehensively shown that cyanostilbene/CB[8]‐based fluorescent SBCPs represent a novel and fascinating class of eco‐friendly artificial light‐harvesting system.     

Dual Response to Light and Heat of a Metal–Organic Rotaxane Network Featuring Flexible Viologen-Derived Structs

Metal–organic rotaxane compounds (MORCs) with supramolecular (pseudo)rotaxane motifs as main structures have inherent dynamic character, but their potential as responsive molecular machines is largely hampered by poor responsiveness to external stimuli. In this study, using a multi-functionalized pseudorotaxane linker that combines two kinds of functionalities, a novel MORC, U-bpybc-CB8 (U refers to uranyl, bpybc refers to 1, 1’-bis(4-carboxybenzyl)-4, 4’-bipyridinium, and CB8 is cucurbit[8]uril), with multi-responsive capability that can respond to both light and thermal stimuli, is reported. The characterization, combining spectra measurements and single-crystal X-ray diffraction, shows that, due to the involvement of viologen-functionalized flexible organic dicarboxylate guest molecule in the CB8- involved pseudorotaxane ligand, the resultant uranyl-based MORC exhibits photochromic behavior after UV or visible light irradiation. More interestingly, it is revealed that the exceptional thermal response of U-bpybc-CB8 as temperature increases from 170 to 270 K, i.e., volume expansion followed by contraction after the inflection temperature of ≈230 K, can be stemmed from the lattice flexibility of this metal–organic supramolecular network. The dual responsiveness of MORCs reported here demonstrates the potential of such supramolecular assemblies as smart molecular components like sensors and switches that respond to light irradiation or temperature changes.     

Wet‐Responsive,Reconfigurable, and Biocompatible Hydrogel Adhesive Films for Transfer Printing of Nanomembranes

This study presents a wet‐responsive and biocompatible smart hydrogel adhesive that exhibits switchable and controllable adhesions on demand for the simple and efficient transfer printing of nanomembranes. The prepared hydrogel adhesives show adhesion strength as high as ≈191 kPa with the aid of nano‐ or microstructure arrays on the surface in the dry state. When in contact with water, the nano/microscopic and macroscopic shape reconfigurations of the hydrogel adhesive occur, which turns off the adhesion (≈0.30 kPa) with an extremely high adhesion switching ratio (>640). The superior adhesion behaviors of the hydrogels are maintained over repeating cycles of hydration and dehydration, indicating their ability to be used repeatedly. The adhesives are made of a biocompatible hydrogel and their adhesion on/off can be controlled with water, making the adhesives compatible with various materials and surfaces, including biological substrates. Based on these smart adhesion capabilities, diverse metallic and semiconducting nanomembranes can be transferred from donor substrates to either rigid or flexible surfaces including biological tissues in a reproducible and robust fashion. Transfer printing of a nanoscale crack sensor onto a bovine eye further demonstrates the potential of the reconfigurable hydrogel adhesive for use as a stimuli‐responsive, smart, and versatile functional adhesive for nanotransfer printing.     

Bioinspired Mineral–Organic Bone Adhesives for Stable Fracture Fixation and Accelerated Bone Regeneration

The use of hydrogel‐based bone adhesives has the potential to revolutionize the clinical treatment of bone repairs. However, severe deficiencies remain in current products, including cytotoxicity concerns, inappropriate mechanical strength, and poor fixation performance in wet biological environments. Inspired by the unique roles of glue molecules in the robust mechanical strength and fracture resistance of bone, a design strategy is proposed using novel mineral–organic bone adhesives for strong water‐resistant fixation and guided bone tissue regeneration. The system leveraged tannic acid (TA) as a phenolic glue molecule to spontaneously co‐assemble with silk fibroin (SF) and hydroxyapatite (HA) in order to fabricate the inorganic–organic hybrid hydrogel (named SF@TA@HA). The combination of the strong affinity between SF and TA along with sacrificial coordination bonds between TA and HA significantly improves the toughness and adhesion strength of the hydrogel by increasing the amount of energy dissipation at the nanoscale. This in turn facilitated adequate and stable fixation of bone fracture in wet biological environments. Furthermore, SF@TA@HA promotes the regeneration of bone defects at an early stage in vivo. This work presents a type of bioinspired bone adhesive that is able to provide stable fracture fixation and accelerated bone regeneration during the bone remodeling process.     

Hydrogels with Preprogrammable Lifetime via UV‐Induced Polymerization and Degradation

Hydrogels are 3D networks infused with water. When formed via radical polymerization, inherently stable hydrogels are created due to stable covalent carbon–carbon bonds. As such, they remain static soft scaffolds, unlike the dynamic tissue they are often compared to. Herein, a hydrogel capable of autonomously converting from a liquid hydrogel precursor solution into a solid hydrogel for a defined period of time, followed by a further transformation back into a liquid polymer solution, is designed. These antagonistic processes are initiated by the same UV light, which is used as stimulus for both a photopolymerization and a photodegradation simultaneously. It is demonstrated how the lifetime of the hydrogel state can be controlled and visualized on the minute scale. Both the photopolymerization and the photodegradation reactions are studied with various methods such as NMR, IR, and confocal microscopy. The different stages of the transformation, e.g., the hydrogel precursor (liquid), hydrogel (solid), and degraded hydrogel (liquid) are investigated with rheometry, viscosimetry, dynamic light scattering, and gel permeation chromatography. Small changes in the molecular composition of the precursor solution result in macroscopically measurable differences. Such time‐dependent twofold photoreactive systems can be of interest for designing dynamic materials, such as glues and photoresists or for biomedical applications.     

Direct 3D Printing of High Strength Biohybrid Gradient Hydrogel Scaffolds for Efficient Repair of Osteochondral Defect

The emerging 3D printing technique allows for tailoring hydrogel‐based soft structure tissue scaffolds for individualized therapy of osteochondral defects. However, the weak mechanical strength and uncontrollable swelling intrinsic to conventional hydrogels restrain their use as bioinks. Here, a high‐strength thermoresponsive supramolecular copolymer hydrogel is synthesized by one‐step copolymerization of dual hydrogen bonding monomers, N‐acryloyl glycinamide, and N‐[tris(hydroxymethyl)methyl] acrylamide. The obtained copolymer hydrogels demonstrate excellent mechanical properties—robust tensile strength (up to 0.41 MPa), large stretchability (up to 860%), and high compressive strength (up to 8.4 MPa). The rapid thermoreversible gel ? sol transition behavior makes this copolymer hydrogel suitable for direct 3D printing. Successful preparation of 3D‐printed biohybrid gradient hydrogel scaffolds is demonstrated with controllable 3D architecture, owing to shear thinning property which allows continuous extrusion through a needle and also immediate gelation of fluid upon deposition on the cooled substrate. Furthermore, this biohybrid gradient hydrogel scaffold printed with transforming growth factor beta 1 and β‐tricalciumphosphate on distinct layers facilitates the attachment, spreading, and chondrogenic and osteogenic differentiation of human bone marrow stem cells (hBMSCs) in vitro. The in vivo experiments reveal that the 3D‐printed biohybrid gradient hydrogel scaffolds significantly accelerate simultaneous regeneration of cartilage and subchondral bone in a rat model.     

Novel Biocompatible Polysaccharide‐Based Self‐Healing Hydrogel

A novel biocompatible polysaccharide‐based self‐healing hydrogel, CEC‐l‐OSA‐l‐ADH hydrogel (“l” means “linked‐by”), is developed by exploiting the dynamic reaction of N‐carboxyethyl chitosan (CEC) and adipic acid dihydrazide (ADH) with oxidized sodium alginate (OSA). The self‐healing ability, as demonstrated by rheological recovery, macroscopic observation, and beam‐shaped strain compression measurement, is attributed to the coexistence of dynamic imine and acylhydrazone bonds in the hydrogel networks. The CEC‐l‐OSA‐l‐ADH hydrogel shows excellent self‐healing ability under physiological conditions with a high healing efficiency (up to 95%) without need for any external stimuli. In addition, the CEC‐l‐OSA‐l‐ADH hydrogel exhibits good cytocompatibility and cell release as demonstrated by three‐dimensional cell encapsulation. With these superior properties, the developed hydrogel holds great potential for applications in various biomedical fields, e.g., as cell or drug delivery carriers.     

Ultrafast UV-Curable Adhesives for Optical Pick-Ups

This paper describes novel ultraviolet (UV)-curable adhesives with an ultrafast curing rate which are fully cured within 8 s for optical pick-up (OPU) applications. Two kinds of oligomers (novolac epoxy acrylate and urethane acrylate), additives, and inorganic fillers were prepared for the formulation of the adhesives. In addition, three kinds of photo-initiator [2,2-dimethoxy-2-phenylacetophenone and 2-hydroxy-2-methylpropiophenone for surface curing and (2,4,6-trimethylbenzoyl) diphenyl phosphine oxide (TMDPO) for deep curing] were mixed to increase the curing rate. Photo-differential scanning calorimetry (photo-DSC) analyses showed that the newly formulated UV adhesives had faster curing rate than conventional UV adhesives. The UV adhesives were applied to OPUs for DVD/CD-RW, and five kinds of reliability tests, i.e., thermal shock, low-temperature storage, high-temperature storage, high temperature/high humidity, and nonoperation shock tests, were conducted to evaluate the adhesive reliability. According to the results of reliability tests and thermal stress simulations, the UV adhesives with lower storage modulus (E′) showed better thermal shock reliability due to lower thermal stresses. In addition, OPUs assembled using the UV adhesives passed all reliability tests. Consequently, the UV adhesives were successfully applied to OPUs in OPU production lines, contributing to mass production.     

Hydrogel Adhesion: A Supramolecular Synergy of Chemistry,Topology, and Mechanics

Adhering hydrogels to various materials is fundamental to a large array of established and emerging applications. The last few years have seen transformative advances in achieving strong hydrogel adhesion, which is a supramolecular phenomenon. Two adherends connect through covalent bonds, noncovalent complexes, polymer chains, polymer networks, or nanoparticles. Separating the adherends dissipates energy through cascading events across length scales, including bond cleavage, chain retraction, and bulk hysteresis. A unifying principle has emerged: strong hydrogel adhesion requires the synergy of chemistry of bonds, topology of connection, and mechanics of dissipation. This synergy characterizes hydrogel adhesion to various materials (another hydrogel, tissue, elastomer, plastic, metal, glass, and ceramic) in various operations (cast, coat, print, attach, pierce, and glue). Strong adhesion can be made permanent, reversible, degradable, or on‐demand detachable. The development of hydrogel adhesion and its applications adheres disciplines, discovers interlinks, and forges cohesion. Discussed throughout the review are immediate opportunities for fundamental studies and practical applications.     

Bioinspired Anisotropic Hydrogel Actuators with On–Off Switchable and Color‐Tunable Fluorescence Behaviors

An effective approach to develop a novel macroscopic anisotropic bilayer hydrogel actuator with on–off switchable fluorescent color‐changing function is reported. Through combining a collapsed thermoresponsive graphene oxide‐poly(N‐isopropylacrylamide) (GO‐PNIPAM) hydrogel layer with a pH‐responsive perylene bisimide‐functionalized hyperbranched polyethylenimine (PBI‐HPEI) hydrogel layer via macroscopic supramolecular assembly, a bilayer hydrogel is obtained that can be tailored and reswells to form a 3D hydrogel actuator. The actuator can undergo complex shape deformation caused by the PNIPAM outside layer, then the PBI‐HPEI hydrogel inside layer can be unfolded to trigger the on–off switch of the pH‐responsive fluorescence under the green light irradiation. This work will inspire the design and fabrication of novel biomimetic smart materials with synergistic functions.     

Mussel Inspired Dynamic Cross‐Linking of Self‐Healing Peptide Nanofiber Network

A general drawback of supramolecular peptide networks is their weak mechanical properties. In order to overcome a similar challenge, mussels have adapted to a pH‐dependent iron complexation strategy for adhesion and curing. This strategy also provides successful stiffening and self‐healing properties. The present study is inspired by the mussel curing strategy to establish iron cross‐link points in self‐assembled peptide networks. The impact of peptide‐iron complexation on the morphology and secondary structure of the supramolecular nanofibers is characterized by scanning electron microscopy, circular dichroism and Fourier transform infrared spectroscopy. Mechanical properties of the cross‐linked network are probed by small angle oscillatory rheology and nanoindentation by atomic force microscopy. It is shown that iron complexation has no influence on self‐assembly and β‐sheet‐driven elongation of the nanofibers. On the other hand, the organic‐inorganic hybrid network of iron cross‐linked nanofibers demonstrates strong mechanical properties comparable to that of covalently cross‐linked network. Strikingly, iron cross‐linking does not inhibit intrinsic reversibility of supramolecular peptide polymers into disassembled building blocks and the self‐healing ability upon high shear load. The strategy described here could be extended to improve mechanical properties of a wide range of supramolecular polymer networks.     

Configurationally Confined Multilevel Supramolecular Assemblies for Modulating Multicolor Luminescence

Herein, multilevel supramolecular assemblies are reported based on sulfobutylether-β-cyclodextrin (SBE-βCD) and cucurbit[8]uril (CB[8]), which can control the topological morphology from nanoparticles to nanosheets and modulate the multicolor luminescence. Benefiting from the large cavity of CB[8] and its strong binding affinity with positively charged tetraphenylethylene pyridinium (TPE-Py), a 1:2 stoichiometric supramolecular assembly is formed through host–guest interactions with binding constants of 2.95 × 10¹¹ M⁻² and fluorescence bathochromic shift about 35 nm due to the macrocyclic confinement effect, thereby endowing the fluorescence enhancement about 20 times when further assembled with negatively charged SBE-βCD to form nanosheets through electrostatic interactions. In contrast, the direct assembly of TPE-Py and SBE-βCD can form nanoparticles through electrostatic interactions, showing only tenfold enhancement and no bathochromic shift due to the lack of macrocyclic confinement effect. After doping the near-infrared dye acceptor sulfonated aluminum phthalocyanine (AlPcS4), the nanosheets structure exhibits a higher energy transfer efficiency of about 75% and a larger antenna effect of 29.3 than that of nanoparticles. The multilevel supramolecular assemblies can be used in multicolor luminescence information storage and multiple logical gate systems, providing an efficient approach for configurationally confined topological morphology regulation and luminescent materials.     

Physical Double‐Network Hydrogel Adhesives with Rapid Shape Adaptability,Fast Self‐Healing,Antioxidant and NIR/pH Stimulus‐Responsiveness for Multidrug‐Resistant Bacterial Infection and Removable Wound Dressing

Developing physical double‐network (DN) removable hydrogel adhesives with both high healing efficiency and photothermal antibacterial activities to cope with multidrug‐resistant bacterial infection, wound closure, and wound healing remains an ongoing challenge. An injectable physical DN self‐healing hydrogel adhesive under physiological conditions is designed to treat multidrug‐resistant bacteria infection and full‐thickness skin incision/defect repair. The hydrogel adhesive consists of catechol–Fe³⁺ coordination cross‐linked poly(glycerol sebacate)‐co‐poly(ethylene glycol)‐g‐catechol and quadruple hydrogen bonding cross‐linked ureido‐pyrimidinone modified gelatin. It possesses excellent anti‐oxidation, NIR/pH responsiveness, and shape adaptation. Additionally, the hydrogel presents rapid self‐healing, good tissue adhesion, degradability, photothermal antibacterial activity, and NIR irradiation and/or acidic solution washing‐assisted removability. In vivo experiments prove that the hydrogels have good hemostasis of skin trauma and high killing ratio for methicillin‐resistant staphylococcus aureus (MRSA) and achieve better wound closure and healing of skin incision than medical glue and surgical suture. In particular, they can significantly promote full‐thickness skin defect wound healing by regulating inflammation, accelerating collagen deposition, promoting granulation tissue formation, and vascularization. These on‐demand dissolvable and antioxidant physical double‐network hydrogel adhesives are excellent multifunctional dressings for treating in vivo MRSA infection, wound closure, and wound healing.     

Trigger-Detachable Hydrogel Adhesives for Bioelectronic Interfaces

Recent electronics technology development has provided unprecedented opportunities for enabling implantable bioelectronics for long-term disease monitoring and treatment. Current electronics-tissue interfaces are characterized by weak physical interactions, suffering from potential interfacial failure or dislocation during long-term application. On the other hand, some new technologies can be used to achieve robust electronics-tissue interfaces; however, such technologies are limited by potential risks and the discomfort associated with postdetachment of the bioelectronics. Here, a hydrogel-based electronics-tissue interface based on the exploitation of dynamic interactions (such as boronate-diol complexation) that features an interfacial toughness over 400 J m⁻² is presented. Moreover, these hydrogel adhesion layers are also trigger-detachable by dissociating the dynamic complexes (i.e., addition of glucose). These hydrogel-based bioelectronic interfaces enable the in vivo recording of physiological signals (i.e., electromyograph, blood pressure, or pulse rates). Upon mild triggering, these bioelectronics can be easily detached without causing any damage, trauma, or discomfort to the skin, tissues, and organs. This kind of trigger-detachable hydrogel adhesives offer general applicability in bioelectronic interfaces, exhibiting promising utility in monitoring, modulating, and treating diseases where temporary monitoring of physiologic signals, interfacial robustness, and postremoval of bioelectronics are required.     

Salt‐Assisted Toughening of Protein Hydrogel with Controlled Degradation for Bone Regeneration

Recently, strong polymer‐based hydrogels have been intensively investigated. However, the development of tough protein hydrogels with controlled degradation for bone regeneration has rarely been reported. Here, regenerated silk fibroin/gelatin (RSF/G) hydrogels with both strength and controlled degradation are prepared via physically and chemically double‐crosslinked networks. As a representative example, the 9%RSF/3%G hydrogel shows approximately 80% elongation and a compressive and tensile modulus of up to 0.25 and 0.21 MPa, respectively. It also shows a degradation rate that can be adjusted to approximately three months in vivo, a value between that of the rapidly degrading gelatin hydrogel and the slowly degrading RSF hydrogel. The 9%RSF/3%G hydrogel has good biocompatibility and promotes the proliferation and differentiation of bone marrow–derived stem cells compared with the control and pure RSF hydrogels. At 12 weeks after implantation of the gel in a calvarial defect, micro‐computed tomography shows greater bone volume and bone mineral density in the 9%RSF/3%G group. More importantly, histology reveals more mineralization and enhancements in the quality and rate of bone regeneration with less of a tissue response in the 9%RSF/3%G group. These results indicate the promising potential of this tough protein hydrogel with controlled degradation for bone regeneration applications.     

Shear‐Thinning Supramolecular Hydrogels with Secondary Autonomous Covalent Crosslinking to Modulate Viscoelastic Properties In Vivo

Clinical percutaneous delivery of synthetically engineered hydrogels remains limited due to challenges posed by crosslinking kinetics—too fast leads to delivery failure, too slow limits material retention. To overcome this challenge, supramolecular assembly is exploited to localize hydrogels at the injection site and introduce subsequent covalent crosslinking to control final material properties. Supramolecular gels are designed through the separate pendant modifications of hyaluronic acid (HA) by the guest–host pair cyclodextrin and adamantane, enabling shear‐thinning injection and high target site retention (>98%). Secondary covalent crosslinking occurs via addition of thiols and Michael‐acceptors (i.e., methacrylates, acrylates, vinyl sulfones) on HA and increases hydrogel moduli (E = 25.0 ± 4.5 kPa) and stability (>3.5 fold in vivo at 28 d). Application of the dual‐crosslinking hydrogel to a myocardial infarct model shows improved outcomes relative to untreated and supramolecular hydrogel alone controls, demonstrating its potential in a range of applications where the precise delivery of hydrogels with tunable properties is desired.     

Injectable Self-Healing Natural Biopolymer-Based Hydrogel Adhesive with Thermoresponsive Reversible Adhesion for Minimally Invasive Surgery

Biocompatible hydrogel adhesives with multifunctional properties, including injectability, fast self-healing, and suitable on-demand detachment, are highly desired for minimally invasive procedures, but such materials are still lacking. Herein, an injectable self-healing biocompatible hydrogel adhesive with thermoresponsive reversible adhesion based on two extracellular matrix-derived biopolymers, gelatin and chondroitin sulfate, is developed to be used as a surgical adhesive for sealing or reconnecting ruptured tissues. The resulting hydrogels present good self-healing and can be conveniently injected through needles. The strong tissue adhesion at physiological temperatures originates from the Schiff base and hydrogen bonding interactions between the hydrogel and tissue that can be weakened at low temperatures, thereby easily detaching the hydrogel from the tissue in the gelation state. In vivo and ex vivo rat model show that the adhesives can effectively seal bleeding wounds and fluid leakages in the absence of sutures or staples. Specifically, a proof of concept experiment in a damaged rat liver model demonstrates the ability of the adhesives to act as a suitable laparoscopic sealant for laparoscopic surgery. Overall, the adhesive has several advantages, including low cost and ease of production and application that make it an exceptional multifunctional tissue adhesive/sealant, effective in minimally invasive surgical applications.