An adhesive and resilient hydrogel for the sealing and treatment of gastric perforation

In situ 3D bioprinted GDMA/Prussian blue nanozyme hydrogel with wet adhesion promotes macrophage phenotype modulation and intestinal defect repair

Developing hydrogels with wet-adhesion, immunomodulation and regenerative repair capabilities in intestinal repair remains a formidable challenge. In the present study, the development of an anti-inflammatory, wet-adhesive, decellularized extracellular matrix hydrogel produced using three-dimensional (3D) -printing technology is presented. This hydrogel, which integrates gelatin and dopamine, was demonstrated to display excellent wet-adhesion properties, fully harnessing the outstanding regenerative potential of the decellularized small-intestine matrix. Furthermore, the integration of Prussian Blue nanozymes imparted significant anti-inflammatory and antioxidant properties. Through modulating macrophage polarization, the hydrogel was not only found to enhance tissue repair, but also to substantially mitigate inflammation. In vivo experiments (namely, histopathological analyses using a rat model) demonstrated that this hydrogel was able to effectively enhance tissue regeneration and healing in models of intestinal damage. In conclusion, through the utilization of 3D-printing technology, the present study has shown that the precise manufacturing and customization of the hydrogel to various shapes and sizes of intestinal defects may be executed, thereby providing an innovative strategy for intestinal repair. This advanced hydrogel has therefore been shown to hold significant promise as a bioadhesive for both emergency repair and regenerative therapy.

Multi-targeted nanogel drug delivery system alleviates neuroinflammation and promotes spinal cord injury repair

Spinal cord injury (SCI) is significantly hampered by an inflammatory microenvironment, prompting continued efforts in drug development to address inflammation. Research shows that quercetin (Que) exhibits excellent performance in reducing inflammation and neuroprotection. However, its application is limited by poor solubility, notable side effects, and the unique pathophysiology of the spinal cord. In this study, we introduce a novel multifunctional liposome hydrogel drug delivery system (QLipTC@HDM), obtained by incorporating liposomes with blood-spinal cord barrier penetration and injury site targeting properties (LipTC) into a dual-network viscous hydrogel (HDM). Our results demonstrate that encapsulating Que in LipTC (QLipTC) enhances solubility, minimizes toxic side effects, facilitates lesion targeting, and aids in crossing the blood-spinal cord barrier. Moreover, encapsulation in HDM significantly prolongs the retention of QLipTC at the injury site after local administration. Crucially, our findings reveal that QLipTC@HDM induces M2 phenotype transformation in glial cells and in mice with SCI, thereby mitigating inflammation. This intervention additionally preserves the integrity of the blood-spinal cord barrier, optimizes the spinal cord microenvironment, reduces glial scarring, promotes axonal regeneration, and enhances motor function recovery in SCI mice. In summary, our investigations highlight the potential of this disease-specific drug delivery system as a promising therapeutic approach for the treatment and management of SCI.

Electrostatically Enhanced Biomimetic Asymmetric Hydrogel with a Dung Beetle-Inspired Pattern for Internal Trauma Sealing

Herein, a biologically asymmetric adhesion-patterned hydrogel induced by the dung beetle surface was proposed for internal trauma sealing. The electrostatic interaction-enhanced dual networks endowed the hydrogel patch with superior mechanical performance, thus achieving a favorable sealing ability. Poly(acrylic acid) (pAA), chitooligosaccharide (COS), and gelatin were used as the composition of our hydrogel system. Concurrently, the bionic raised structure enabled a significant adhesion drop effect. The surface waviness function, fitted to the curved bumps, showed the design direction of the patterned bumps, which was indicative of subsequent research. Also, the microparticle deposition method could exert a synergistic effect with the patterned surface, which together contributed to the asymmetry of the adhesive hydrogel patch. Following simulation experiments such as in vitro bursting tests, we conducted a rat gastric trauma model to validate the application potential of this bionic asymmetric patterned patch. The asymmetric adhesion hydrogel patch had an excellent sealing effect, antiadhesive properties, and operability and was expected to have a promising application prospect, providing a strategy for the design of subsequent in vivo trauma-sealing biomaterials.

Multifunctional Adhesive Hydrogels: From Design to Biomedical Applications

Adhesive hydrogels characterized by structural properties similar to the extracellular matrix, excellent biocompatibility, controlled degradation, and tunable mechanical properties have demonstrated significant potential in biomedical applications, including tissue engineering, biosensors, and drug delivery systems. These hydrogels exhibit remarkable adhesion to target substrates and can be rationally engineered to meet specific requirements. In recent decades, adhesive hydrogels have experienced significant advancements driven by the introduction of numerous multifunctional design strategies. This review initially summarizes the chemical bond-based design strategies for tissue adhesion, encompassing static covalent bonds, dynamic covalent bonds, and non-covalent interactions. Subsequently, the multiple functionalities imparted by these diverse design strategies, including highly stretchable and tough performances, responsiveness to microenvironments, anti-freezing/heating properties, conductivity, antibacterial activity, and hemostatic properties are discussed. In addition, recent advances in the biomedical applications of adhesive hydrogels, focusing on tissue repair, drug delivery, medical devices, and wearable sensors are reviewed. Finally, the current challenges are highlighted and future trends in this rapidly evolving field are discussed.

Bioinspired Wearable Hydrogel Composite with Sustained Drug-Release for Wound Healing and Naked-Eye Visual Early Warning of Wound Dehiscence

Wound healing is critical to the structural and functional restoration of damaged tissue. However, effective wound closure and healing are always great challenges in regenerative engineering. This study provided bioinspired wearable hydrogel composites with drug-releasing hydrogel and nonclose-packed photonic crystals (NPCs) for wound therapy and naked-eye visual early warning of wound dehiscence. Molecular dynamics models and drug-releasing results illustrated the sustained drug release of ibuprofen, and the mechanical properties of the drug-releasing hydrogel were optimized with 1410% tensile strain by introducing fish collagen; their biocompatibility and adhesion were also improved. The structural color of the NPCs blue-shifted from 630 to 500 nm with 15.0% strain, and the original color was customized with poly(methyl methacrylate) (PMMA) concentration and acrylamide content. Compared with the gauze and the traditional hydrogels, the composite provided a moist environment and an effectively closed wound; the debridement and released drug avoided inflammation, and the rat wound was healed 40.5% on the third day and essentially 100% on the 14th day. The work provided a novel strategy for wound healing and naked-eye visual early warning when a wound deforms, which is expected to promote the synergistic development of clinical treatment and visualized early warning.

In Situ 4D Printing of Polyelectrolyte/Magnetic Composites for Sutureless Gastric Perforation Sealing

In situ bioprinting has emerged as one of the most promising techniques for the sutureless tissue sealing of internal organs. However, most existing in situ bioprinting methods are limited by the complex and confined printing space inside the organs, harsh curing conditions for printable bioinks, and poor ability to suturelessly seal injured parts. The combination of in situ bioprinting and 4D printing is a promising technique for tissue repair. Herein, the in situ 4D printing of polyelectrolyte/magnetic composites by gastroscopy for sutureless internal tissue sealing is reported. Using gastric perforation as an example, a gelatin/sodium alginate/magnetic bioink is developed, which can be precisely located by a gastroscope with the assistance of an external magnetic field, solidified in gastric fluid, and firmly adhered to tissue surfaces. The solidified bioink along the defect can be attracted by an external magnetic field, resulting in sutureless sealing. A demonstration using a porcine stomach with an artificial perforation confirms the feasibility of sutureless sealing using 4D printing. Moreover, an in vivo investigation on gastric perforation in a rat model identifies the biocompatibility by H&E and CD68+ staining. This study provides a new orientation and concept for functionality-modified in situ 4D bioprinting.

Natural Underwater Bioadhesive Offering Cohesion Modulation via Hydrogen Bond Disruptor: A Highly Injectable and in Vivo Stable Remedy for Gastric Ulcer Resolution

Injectable bioadhesives are attractive for managing gastric ulcers through minimally invasive procedures. However, the formidable challenge is to develop bioadhesives that exhibit high injectability, rapidly adhere to lesion tissues with fast gelation, provide reliable protection in the harsh gastric environment, and simultaneously ensure stringent standards of biocompatibility. Here, a natural bioadhesive with tunable cohesion is developed based on the facile and controllable gelation between silk fibroin and tannic acid. By incorporating a hydrogen bond disruptor (urea or guanidine hydrochloride), the inherent network within the bioadhesive is disturbed, inducing a transition to a fluidic state for smooth injection (injection force <5 N). Upon injection, the fluidic bioadhesive thoroughly wets tissues, while the rapid diffusion of the disruptor triggers instantaneous in situ gelation. This orchestrated process fosters the formed bioadhesive with durable wet tissue affinity and mechanical properties that harmonize with gastric tissues, thereby bestowing long-lasting protection for ulcer healing, as evidenced through in vitro and in vivo verification. Moreover, it can be conveniently stored (≥3 m) postdehydration. This work presents a promising strategy for designing highly injectable bioadhesives utilizing natural feedstocks, avoiding any safety risks associated with synthetic materials or nonphysiological gelation conditions, and offering the potential for minimally invasive application.

Injectable-Hydrogel-Based Tissue Sealant for Hemostasis, Bacteria Inhibition, and Pro-Angiogenesis in Organ Bleeding Wounds and Therapeutic Outcome Monitoring Via NIR-II Optical Imaging

Sudden hemorrhage stemming from internal organ wounds poses a grave and potentially fatal risk if left untreated. Injectable-hydrogel-based tissue sealants featuring multiple actions, including fit-to-shape in situ gelation, rapid hemostasis, pro-angiogenic, anti-bacterial and outcome tracking, are ideal for the management of organ trauma wounds. Herein, an injectable-hydrogel tissue sealant AN@CD-PEG&TQ which consists of four-arm 4-arm poly(ethylene glycol) (PEG-SC) succinimidyl carbonate), AN@CD nanoprobe, and two bioactive peptides (anti-microbial peptide Tet213 and pro-angiogenic peptide QK) is developed. Among them, AN@CD nanoparticles form through host/guest complexation of amino-group-containing β-cyclodextrin and adamantyl group, enabling in situ biomarker (NO)-activatable optoacoustic/NIR-II: Near-infrared second biological window fluorescent imaging. The ample ─NH2 groups on the surface of AN@CD readily engage in rapid cross-linking with succinimidyl ester groups located at the ends of four-arm PEG-SC. This cross-linking expedites the gelation process without necessitating additional initiators or cross-linking agents; thus, significantly enhancing both hydrogel's application convenience and biocompatibility. Bioactive peptides (Tet213 and QK) safeguard against possible bacterial infections, facilitate angiogenesis, and eventually, improve organ wounds healing. This hydrogel-based tissue sealant demonstrates superior therapeutic and bioimaging performance in various mouse models including liver hemorrhage, gastric perforation, and bacterial-infected skin wound mouse models, highlighting its potential as a high-performance wound sealant for organ bleeding wound management.

Chinese herb pollen derived micromotors as active oral drug delivery system for gastric ulcer treatment

Considerable efforts have been devoted to treating gastric ulcers. Attempts in this field tend to develop drug delivery systems with prolonged gastric retention time. Herein, we develop novel Chinese herb pollen-derived micromotors as active oral drug delivery system for treating gastric ulcer. Such Chinese herb pollen-derived micromotors are simply produced by asymmetrically sputtering Mg layer onto one side of pollen grains. When exposed to gastric juice, the Mg layer can react with the hydrogen ions, resulting in intensive generation of hydrogen bubbles to propel the micromotors. Benefiting from the autonomous motion and unique spiny structure, our micromotors can move actively in the stomach and adhere to the surrounding tissues. Besides, their special architecture endows the micromotors with salient capacity of drug loading and releasing. Based on these features, we have demonstrated that our Chinese herb pollen-derived micromotors could effective deliver berberine hydrochloride and show desirable curative effect on the gastric ulcer model of mice. Therefore, these Chinese herb pollen-derived micromotors are anticipated to serve as promising oral drug delivery carriers for clinical applications.

Functional adhesive hydrogels for biological interfaces

Hydrogel adhesives are extensively employed in biological interfaces such as epidermal flexible electronics, tissue engineering, and implanted device. The development of functional hydrogel adhesives is a critical, yet challenging task since combining two or more attributes that seem incompatible into one adhesive hydrogel without sacrificing the hydrogel's pristine capabilities. In this Review, we highlight current developments in the fabrication of functional adhesive hydrogels, which are suitable for a variety of application scenarios, particularly those that occur underwater or on tissue/organ surface conditions. The design strategies for a multifunctional adhesive hydrogel with desirable properties including underwater adhesion, self-healing, good biocompatibility, electrical conductivity, and anti-swelling are discussed comprehensively. We then discuss the challenges faced by adhesive hydrogels, as well as their potential applications in biological interfaces. Adhesive hydrogels are the star building blocks of bio-interface materials for individualized healthcare and other bioengineering areas.

Photocurable injectable Janus hydrogel with minimally invasive delivery for all-in-one treatment of gastric perforations and postoperative adhesions

Background: Surgical sutures for sealing gastric perforations (GP) are associated with severe inflammation and postoperative adhesions. Hydrogel bioadhesives offer a potential alternative for sutureless repair of GP; however, their application in minimally invasive surgery is limited due to their prefabricated patch-form, lacking in situ gelation capability. In this study, we emphasized an all-in-one minimally invasive strategy for sutureless repair of acute GP. Methods: an injectable photocurable Janus hydrogel was synthesized, and their ability to seal GP was performed. A rat GP model was used to verify the wound healing and antiadhesion efficiency of hydrogels, and a rabbit GP model was used to verify their laparoscopic feasibility. A fresh human corpse GP model was further employed to verify the user-friendliness of a minimally invasive deliverable (MID) device. A minipig GP model was utilized to evaluate the all-in-one minimally invasive strategy for the treatment of acute GP. Results: Such injectable Janus hydrogel exhibited asymmetric adhesiveness, where the inner-facing side of the hydrogel displays strong sealing and wound healing abilities for GP, while the outward-facing side prevents postoperative adhesion formation. We further developed a minimally invasive deliverable (MID) device integrating hydrogel-delivery parts and photocrosslinking-gelation parts in a laparoscope system. The precise delivery and rapid fluid-tight sealing process of the injectable Janus hydrogel using the MID device for in situ GP repair were demonstrated in a simulated clinical scenario. The in vivo effectiveness of GP sutureless repair was successfully validated in porcine models, with further exploration of the underlying mechanism. Conclusions: Our findings reveal that the injectable Janus hydrogel offers an all-in-one strategy for sutureless GP repair and concurrent prevention of postoperative adhesion formation by incorporating the MID device in minimally invasive surgery, presenting the significant potential to reduce patient surgical complications.

Case report: Catastrophic event: neonatal gastric perforation and complication of capillary leak syndrome

Neonatal gastric perforation (NGP) is a rare, but life-threatening condition that can lead to serious conditions, such as capillary leak syndrome (CLS). Here, we present the case of a preterm male infant with NGP complicated by CLS after stomach repair. The patient was born at 33 2/7 weeks, weighed 1,770 g, and was diagnosed with respiratory distress syndrome. On the fourth day of life, the patient presented with distention and an unstable cardiovascular system. Routine blood tests revealed a white blood cell count of 2.4 × 109/L. Chest and abdominal radiography revealed a pneumoperitoneum, suggesting a gastrointestinal perforation. The patient was urgently transferred to a tertiary hospital for exploratory laparotomy, where a 2 cm diameter perforation was discovered in the stomach wall and subsequently repaired. Pathological findings indicated the absence of a muscular layer in the stomach wall. The patient unexpectedly developed CLS postoperatively, leading to multiorgan dysfunction and eventual death. The underlying pathological mechanism of NGP-induced CLS may be related to severe chemical peritonitis, sepsis, endothelial glycocalyx dysfunction, enhanced systemic inflammation, and translocation of the gut microbiota, causing endothelial hyperpermeability. Notablely, abdominal surgery itself can be a significant triggering factor for CLS occurrence. Complications of NGP and CLS are extremely dangerous. Investigating the mechanism by which NGP triggers CLS could potentially improve the prognosis. Conservative treatment for pneumoperitoneum secondary to gastric perforation may be a reasonable option, especially when the condition of the patient is unstable.

Injectable, self-healing hydrogel adhesives with firm tissue adhesion and on-demand biodegradation for sutureless wound closure

Tissue adhesives have garnered extensive interest as alternatives and supplements to sutures, whereas major challenges still remain, including weak tissue adhesion, inadequate biocompatibility, and uncontrolled biodegradation. Here, injectable and biocompatible hydrogel adhesives are developed via catalyst-free o-phthalaldehyde/amine (hydrazide) cross-linking reaction. The hydrogels demonstrate rapid and firm adhesion to various tissues, and an o-phthalaldehyde-mediated tissue adhesion mechanism is established. The hydrogel adhesives show controlled degradation profiles of 6 to 22 weeks in vivo through the incorporation of disulfide bonds into hydrogel network. In liver and blood vessel injury, the hydrogels effectively seal the incisions and rapidly stop bleeding. In rat and rabbit models of full-thickness skin incision, the hydrogel adhesives quickly close the incisions and accelerate wound healing, which exhibit efficacies superior to those of commercially available fibrin glue and cyanoacrylate glue. Thus, the hydrogel adhesives show great potential for sutureless wound closure, hemostasis sealing, and prevention of leakage in surgical applications.

Concentration Selection of Biofriendly Enzyme-Modified Gelatin Hydrogels for Periodontal Bone Regeneration

Periodontitis is challenging to cure radically due to its complex periodontal structure and particular microenvironment of dysbiosis and inflammation. However, with the assistance of various materials, cell osteogenic differentiation could be improved, and the ability of hard tissue regeneration could be enhanced. This study aimed to explore the appropriate concentration ratio of biofriendly transglutaminase-modified gelatin hydrogels for promoting periodontal alveolar bone regeneration. Through a series of characterization and cell experiments, we found that all the hydrogels possessed multi-space network structures and demonstrated their biocompatibility. In vivo and in vitro osteogenic differentiation experiments also confirmed that the group 40-5 (transglutaminase-gelatin concentration ratio) possessed a favorable osteogenic potential. In summary, we conclude that such hydrogel with a 40-5 concentration is most conducive to promoting periodontal bone reconstruction, which might be a new route to deal with the dilemma of clinical periodontal treatment.

Hydrogels for Mucosal Drug Delivery

Mucosal tissues are often a desirable site of drug action to treat disease and engage the immune system. However, systemically administered drugs suffer from limited bioavailability in mucosal tissues where technologies to enable direct, local delivery to these sites would prove useful. In this Spotlight on Applications article, we discuss hydrogels as an attractive means for local delivery of therapeutics to address a range of conditions affecting the eye, nose, oral cavity, gastrointestinal, urinary bladder, and vaginal tracts. Considering the barriers to effective mucosal delivery, we provide an overview of the key parameters in the use of hydrogels for these applications. Finally, we highlight recent work demonstrating their use for inflammatory and infectious diseases affecting these tissues.

Biomaterial-mediated strategies for accurate and convenient diagnosis, and effective treatment of diabetes: advantages, current progress and future perspectives

As a kind of widespread chronic disease, diabetes potentially triggers serious complications, thereby severely threatening patients' life and health. To achieve the goal of more accurate and convenient diagnosis, and effective treatment of diabetes that what could be achieved based on traditional methods, many biomaterial-mediated strategies have been launched in recent studies, and have shown promising application potentials. In this review, we have systematically summarized the biomaterial-mediated diagnosis strategies in three parts including combined use of biomedical nanomaterials or organometallic compounds and Raman spectroscopy, utilization of gas sensors made of biomedical metal-oxides to detect glucose in exhaled gas, and detection of glucose by wearable sensors made of biomaterials with high sensitivity and conductivity, and the biomaterial-mediated treatment strategies in four parts including antidiabetic drug delivery by nanoparticles, transdermal drug delivery systems, gels and vesicles, and achieving insulin secretion by transplantation of pancreatic endocrine cells or tissue engineered islets. In particular, advantages of every strategy, current research progress, as well as the challenges and perspectives are elaborated. This review will certainly help to spark new ideas and possibilities for accurate and convenient diagnosis, and effective treatment of diabetes.

Advances in Hydrogel Adhesives for Gastrointestinal Wound Closure and Repair

Millions of individuals undergo gastrointestinal (GI) tract surgeries each year with common postoperative complications including bleeding, perforation, anastomotic leakage, and infection. Today, techniques such as suturing and stapling seal internal wounds, and electrocoagulation stops bleeding. These methods induce secondary damage to the tissue and can be technically difficult to perform depending on the wound site location. To overcome these challenges and to further advance wound closure, hydrogel adhesives are being investigated to specifically target GI tract wounds because of their atraumatic nature, fluid-tight sealing capability, favorable wound healing properties, and facile application. However, challenges remain that limit their use, such as weak underwater adhesive strength, slow gelation, and/or acidic degradation. In this review, we summarize recent advances in hydrogel adhesives to treat various GI tract wounds, with a focus on novel material designs and compositions to combat the environment-specific challenges of GI injury. We conclude with a discussion of potential opportunities from both research and clinical perspectives.

Instant and Tough Adhesives for Rapid Gastric Perforation and Traumatic Pneumothorax Sealing

Hydrogel adhesives are hot spots due to their ubiquity and practical relevance. However, achieving a robust wet adhesion is still a challenge due to the preferential formation of hydrogen bonds between interfacial fluids and bulk hydrogel, as well as targeted substrates. Herein, a half-dry adhesive consisting of a silk fibroin (SF) semi-interpenetrating network and poly(acrylic acid) covalent network, which can allow a rapid liquid adsorption and repulsion process encountering a wet tissue, is reported. The remaining water enables excellent hydrogel flexibility to a dynamic surface, while the β-sheet fold endows its tough bulk strength under the peeling-off process. Notably, the wet adhesion energy versus porcine skin is 1440 J m^-2 due to the combination of hydrogen bonds, electrostatic interactions, and chain entanglement derived from SF. In particular, both in vitro and in vivo outcomes indicate excellent hemostatic effects and result in incision closure of skin, artery, gastric perforation, and lung. After the first-stage closure, polyacrylic-silk fibroin adhesive (PSA) sealants can detach from the lung surface, fitting well to the healing period. By virtue of the reliable adhesion and good noncytotoxicity, PSA may be a prospective candidate for tissue sealant and drug carrier applications.

Multifunctional 3D platforms for rapid hemostasis and wound healing: Structural and functional prospects at biointerfaces

354Fabrication of multifunctional hemostats is indispensable against chronic blood loss and accelerated wound healing. Various hemostatic materials that aid wound repair or rapid tissue regeneration has been developed in the last 5 years. This review provides an overview of the three-dimensional (3D) hemostatic platforms designed through the latest technologies like electrospinning, 3D printing, and lithography, solely or in combination, for application in rapid wound healing. We critically discuss the pivotal role of micro/nano-3D topography and biomaterial properties in mediating rapid blood clots and healing at the hemostat-biointerface. We also highlight the advantages and limitations of the designed 3D hemostats. We anticipate that this review will guide the fabrication of smart hemostats of the future for tissue engineering applications.

Injectable Adhesive Hydrogels for Soft tissue Reconstruction: A Materials Chemistry Perspective

Injectable bioadhesives offer several advantages over conventional staples and sutures in surgery to seal and close incisions or wounds. Despite the growing research in recent years few injectable bioadhesives are available for clinical use. This review summarizes the key chemical features that enable the development and improvements in the use of polymeric injectable hydrogels as bioadhesives or sealants, their design requirements, the gelation mechanism, synthesis routes, and the role of adhesion mechanisms and strategies in different biomedical applications. It is envisaged that developing a deep understanding of the underlying materials chemistry principles will enable researchers to effectively translate bioadhesive technologies into clinically-relevant products.