Hybrid Dry Powders for Rapid Sealing of Gastric Perforations under an Endoscope

Acid-responsive contractile hyaluronic acid-based hydrogel loaded with ginsenoside Rg1 for hemostasis and promotion of gastric wound healing

Due to constant stimulation by stomach acid and local bleeding, gastric tissue wounds tend to heal slowly and complications such as anastomotic leakage have a high incidence. Suturing is often used to treat gastric wounds in clinic, but it still faces risks such as bleeding, slow healing, and leakage. Recently, hydrogel have been widely used to treat various types of wounds. Although hydrogels have shown promising efficacy in wound healing, it is still a challenge in dealing with wounds in gastric tissue for the poor adaptability of traditional materials in acidic environments. Hence, a series of pH responsive and good tissue adhesive hydrogels (MA-HA/AA) based on methacryloyl hyaluronic acid (MA-HA) and acryloyl-6-aminocaproic acid (AA) via in situ photo-crosslinking were designed, and anti-inflammatory and pro-healing traditional Chinese medicines ginsenoside Rg1 was incorporated into the hydrogel to treat gastric tissue wound. These acid-responsive hydrogels could form effective acid-resistant barriers and could lead to hemostasis rapidly through its strong adhesion. Besides, the hydrogels contracted under an acidic environment, which could tighten the gastric tissue wounds and sustained release the loaded ginsenoside Rg1. In addition, the hydrogels showed excellent biocompatibility and in vivo degradability. In summary, the acid-responsive contractile hyaluronic acid hydrogel loaded with ginsenoside Rg1 had good properties for hemostasis and acid-resistance to facilitate the promotion of gastric wounds healing.

Hydrogels in Endoscopic Submucosal Dissection for Gastrointestinal Cancers

Endoscopic Submucosal Dissection (ESD) has emerged as a pivotal technique for the minimally invasive treatment of early gastrointestinal cancers, offering benefits such as reduced trauma, lower complication rates, and cost-effectiveness. Despite its advantages, the selection of optimal biomaterials for submucosal injection poses significant challenges. Current materials used in clinical settings often suffer from rapid diffusion, requiring multiple injections and potentially causing localized inflammation. These issues underscore the importance of identifying more effective submucosal injection materials to minimize postoperative complications and enhance patient outcomes. Recent advancements have highlighted the potential of hydrogels in this context, favored for their ability to maintain mucosal elevation longer and support wound healing. This review comprehensively examines the development and application of hydrogels in ESD, focusing on their physicochemical properties, biocompatibility, and the clinical implications of their use. These issues discuss various formulations of hydrogels, their mechanisms of action, and comparative analyses with traditional materials. Furthermore, the review explores ongoing innovations and future perspectives in hydrogel research, aiming to catalyze further advancements in ESD techniques. STATEMENT OF SIGNIFICANCE: This review critically examines hydrogel technologies in endoscopic submucosal dissection for gastrointestinal cancers, highlighting their role in improving procedural outcomes and patient recovery. It explores hydrogels' ability to enhance mucosal elevation, reduce complications, and accelerate healing, offering insights into their transformative potential in medical treatments. The findings emphasize the development of innovative materials that could significantly advance clinical practices in gastrointestinal cancer management.

Acid-Triggered Charge-Switchable Antibacterial Hydrogel for Accelerated Healing of Gastric Mucosal Wounds

Infection with Helicobacter pylori (H. pylori) is a primary etiological factor for chronic gastritis, peptic ulcers, and gastric cancer. The limited specificity of antibiotics against H. pylori, combined with the risk of severe adverse events from endoscopic submucosal dissection (ESD), presents a major global health challenge in treating gastric mucosal injuries. To address this issue, we developed a targeted antibacterial hydrogel based on a charge-reversal amphiphilic molecule, designed for the harsh gastric acid environment and capable of immediate and strong adhesion. The hydrogel is composed of acryl aspartate (AASP) and cysteine-grafted carboxymethyl chitosan (CMCS-NAC) as the base matrix, integrated with gastric acid-responsive charge-reversal antibacterial molecules (C16N-DCA). Simulated studies show that C16N-DCA undergoes charge reversal under acidic conditions (pH 3), enabling targeted H. pylori eradication mediated by gastric acid, with 98% efficacy and sustained antibacterial activity for up to 36 h. In vitro and in vivo experiments in rodent and porcine models confirmed its safety and efficacy in acidic gastric conditions. This hydrogel offers strong tissue protection and effectively modulates the gastric wound microenvironment, facilitating wound healing and presenting an easily adoptable solution for gastric wound management.

A Bio-Adaptive Janus-Adhesive Dressing with Dynamic Lubrication Overlayer for Prevention of Postoperative Infection and Adhesion

Wound postoperative infection and adhesion are prevalent clinical conditions resulting from surgical trauma. However, integrating intraoperative repair and postoperative management into a dressing suitable for wounds with unpredictable surface shapes and surroundings remains a formidable challenge. Here, we attempt to introduce a dynamic antifouling surface as wound protective covering and report an in situ formation of slippery-adhesive Janus gel (SAJG) by assembling hydrogel (N-hydrosuccinimide ester-activated powders) and elastomer (Silicon oil-infused polydimethylsiloxane). First powders can rapidly absorb interfacial water to gel and bond to tissue based on network entanglement, forming a tough adhesive hydrogel. Then precured organosilicon is applied to hydrogel and bonded together, forming a slippery elastomer. Due to the molecular polarity difference between hydrogel and elastomer, SAJG exhibits anisotropic surface behavior as evidenced by liquid repellency (hydrophilic vs. hydrophobic), and adhesion performance (bioadhesion vs. antiadhesion). Further, in vivo models are constructed and results demonstrated that the SAJG can effectively prevent bacterial infection to promote wound healing and avoid postoperative adhesion. Predictably, the morphologically adaptive SAJG with slippery and adhesive properties will have tremendous potential in addressing complex wound infections and postoperative complications.

Ultrafast self-gelling, superabsorbent, and adhesive chitosan-based hemostatic powders for rapid hemostasis and wound healing

Hemostatic powders are widely used for managing bleeding from wounds with various irregular shapes. However, their limited liquid absorption capacity and difficulty in removal after application remain significant clinical challenges. Herein, we introduce a multifunctional hemostatic powder composed of dually crosslinked poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride-co-acrylic acid) (pMATC-co-AA) and N-[(2-hydroxy-3-trimethylammonium)propyl] chitosan chloride (HTCC), which are integrated via electrostatic interactions and hydrogen bonding. This hemostatic powder exhibits superb liquid-absorbing capacity (94.5 times its own weight in water and 9.1 times in blood), sufficient adhesive properties (5.9 kPa on pig skin), and on-demand removability. It significantly reduces the number of viable Escherichia coli and Staphylococcus aureus by 4.61 and 4.04 orders of magnitude, respectively, thus providing an effective microbiological barrier for the wound. Furthermore, a series of in vivo and in vitro experiments confirm the powder's excellent hemostatic properties. The hydrogel formed on the wound after hemostasis can be removed by saline rinsing on demand, due to its superb liquid-absorbing capacity. Notably, the powder demonstrates good in vivo biocompatibility, with minimal risk of impeding wound healing, and it facilitates the healing process during the later stages. In sum, the hemostatic powder offers a promising solution for trauma bleeding control and acute wound treatment.

Endoscopic Delivery of a Double-Umbrella-Shaped Hydrogel Occluder with Instant Mechanical Interlock and Robust Wet Adhesion for Gastric Perforation Repair

Achieving robust adhesion of bioadhesives on wet tissues to block gastric perforation remains a challenge due to the gradually deteriorated adhesive-tissue interactions by interfacial acidity and multienzyme gastric fluids, thus accompanying failure shedding and life-threatening risks. Here, we report a biocompatible double-umbrella-shaped endoscopy-deliverable hydrogel occluder (EHO) made of caffeic acid (CA)-grafted chitosan (CS) and polyacrylamide (PAM) by molding technique, which is capable of the customizable, rapid, robust, and long-term sealing of large gastric perforations. In addition to interfacial physiochemical interactions (e.g., H-bonding, chelation) between the tissues and polymers, efficient sealing also integrates the advantages of fast mechanical interlocking in space and gradual self-expansion over time to tolerant acidic and mechanically dynamic environments. The EHO exhibits favorable biodegradability due to the reducible disulfide cross-linkers and remarkable protective barrier functions to impede the infiltration of gastric acid and digestive pepsin into the wound. To validate EHO's therapeutic efficacy, we further demonstrate the robust in vivo sealing to large gastric tissues via endoscopic delivery to the porcine stomach and monitor of healing process with improved retention of endogenous growth factors. Besides, in views of simple hydrogel fabrication using molding technique, the biodegradable EHO can be facilely tailored with various topologies according to application scenarios in surgical and minimally invasive endoscopic delivery, thus offering a promising alternative for clinical repair of gastrointestinal perforations and other organs.

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.

Ionically assembled hemostatic powders with rapid self-gelation, strong acid resistance, and on-demand removability for upper gastrointestinal bleeding

Upper gastrointestinal bleeding (UGIB) is bleeding in the upper part of the gastrointestinal tract with an acidic and dynamic environment that limits the application of conventional hemostatic materials. This study focuses on the development of N-[(2-hydroxy-3-trimethylammonium) propyl] chitosan chloride/phytic acid (HTCC/PA, HP) powders with fast hemostatic capability and strong acid resistance, for potential applications in managing UGIB. Upon contact with liquids within 5 seconds, HP powders rapidly transform into hydrogels, forming ionic networks through electrostatic interactions. The ionic crosslinking process facilitates the HP powders with high blood absorption (3.4 times of self-weight), sufficient tissue adhesion (5.2 and 6.1 kPa on porcine skin and stomach, respectively), and hemostasis (within 15 seconds for in vitro clotting). Interestingly, the PA imparts the HP powders with strong acid resistance (69.8% mass remaining after 10 days of incubation at pH 1) and on-demand removable sealing while HTCC contributes to fast hemostasis and good wet adhesion. Moreover, the HP powders show good biocompatibility and promote wound healing. Therefore, these characteristics highlight the promising clinical potential of HP powders for effectively managing UGIB.

Novel Functional Dressing Materials for Intraoral Wound Care

Intraoral wounds represent a particularly challenging category of mucosal and hard tissue injuries, characterized by the unique structures, complex environment, and distinctive healing processes within the oral cavity. They have a common occurrence yet frequently inflict significant inconvenience and pain on patients, causing a serious decline in the quality of life. A variety of novel functional dressings specifically designed for the moist and dynamic oral environment have been developed and realized accelerated and improved wound healing. Thoroughly analyzing and summarizing these materials is of paramount importance in enhancing the understanding and proficiently managing intraoral wounds. In this review, the particular processes and unique characteristics of intraoral wound healing are firstly described. Up-to-date knowledge of various forms, properties, and applications of existing products are then intensively discussed, which are categorized into animal products, plant extracts, natural polymers, and synthetic products. To conclude, this review presents a comprehensive framework of currently available functional intraoral wound dressings, with an aim to provoke inspiration of future studies to design more convenient and versatile materials.

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.

Photothermally responsive graphene hybrid dry powders for diabetic wound healing

The treatment of diabetic wounds remains a significant challenge in the medical field. In this study, we present a novel approach using photothermally responsive graphene hybrid dry powders for the treatment of diabetic wounds. These powders, derived from polyacrylic acid (PAA) and polyethyleneimine (PEI), exhibit rapid water absorption at the interface, leading to thein situformation of physically crosslinked hydrogels due to interactions between polymers. Furthermore, by incorporating graphene into the PAA/PEI powder mixture, we establish a multifunctional platform with capabilities such as photothermal antibacterial effects and drug release. Given the outstanding performance of this hybrid material, we demonstrate its potential in wound healing by incorporating the tumor necrosis factor-alpha (TNF-α) inhibitor Etanercept into the PAA/PEI powder. This intervention resulted in a significant improvement in the wound healing process in diabetic rats, as evidenced by the downregulation of inflammatory factors, promotion of collagen deposition, and enhanced vascularization. These remarkable attributes underscore the enormous potential value of the presented hydrogel patches in the field of biomedicine.

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

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

Dough-Kneading-Inspired Design of an Adhesive Cardiac Patch to Attenuate Cardiac Fibrosis and Improve Cardiac Function via Regulating Glycometabolism

Recently, hydrogel adhesive patches have been explored for treating myocardial infarction. However, achieving secure adhesion onto the wet beating heart and local regulation of pathological microenvironment remains challenging. Herein, a dough-kneading-inspired design of hydrogel adhesive cardiac patch is reported, aiming to improve the strength of prevalent powder-formed patch and retain wet adhesion. In mimicking the polysaccharide and protein components of natural flour, methacrylated polyglutamic acid (PGAMA) is electrostatically interacted with hydroxypropyl chitosan (HPCS) to form PGAMA/HPCS coacervate hydrogel. The PGAMA/HPCS hydrogel is freeze-dried and ground into powders, which are further rehydrated with two aqueous solutions of functional drug, 3-acrylamido phenylboronic acid (APBA)/rutin (Rt) complexes for protecting the myocardium from advanced glycation end product (AGEs) injury by reactive oxygen species (ROS) -responsive Rt release, and hypoxanthine-loaded methacrylated hyaluronic acid (HAMA) nanogels for enhancing macrophage targeting ability to regulate glycometabolism for combating inflammation. The rehydrated powders bearing APBA/Rt complexes and HAMA-hypoxanthine nanogels are repeatedly kneaded into a dough-like gel, which is further subjected to thermal-initiated crosslinking to form a stabilized and sticky patch. This biofunctional patch is applied onto the rats' infarcted myocardium, and the outcomes at 28 days post-surgery indicate efficient restoration of cardiac functions and attenuation of cardiac fibrosis.

A Nature-Derived, Hetero-Structured, Pro-Healing Bioadhesive Patch for High-Performance Sealing of Wet Tissues

Tissue adhesives are promising alternatives to sutures and staples to achieve wound closure and hemostasis. However, they often do not work well on tissues that are soaked in blood or other biological fluids, and organs that are typically exposed to a variety of harsh environments such as different pH values, nonhomogeneous distortions, continuous expansions and contractions, or high pressures. In this study, a nature-derived multilayered hetero-bioadhesive patch (skin secretion of Andrias davidianus (SSAD)-Patch) based on hydrophilic/hydrophobic pro-healing bioadhesives derived from the SSAD is developed, which is designed to form pressure-triggered strong adhesion with wet tissues. The SSAD-Patch is successfully applied for the sealing and healing of tissue defects within 10 s in diverse extreme injury scenarios in vivo including rat stomach perforation, small intestine perforation, fetal membrane defect, porcine carotid artery incision, and lung lobe laceration. The findings reveal a promising new type of self-adhesive regenerative SSAD-Patch, which is potentially adaptable to broad applications (under different pH values and air or liquid pressures) in sutureless wound sealing and healing.

Gluing blood into adhesive gel by oppositely charged polysaccharide dry powder inspired by fibrin fibers coagulation mediator

Hemostatic powders that adapt to irregularly shaped wounds, allowing for easy application and stable storage, have gained popularity for first-aid hemorrhage control. However, traditional powders often provide weak thrombus support and exhibit limited tissue adhesion, making them susceptible to dislodgment by the bloodstream. Inspired by fibrin fibers coagulation mediator, we have developed a bi-component hemostatic powder composed of positively charged quaternized chitosan (QCS) and negatively charged catechol-modified alginate (Cat-SA). Upon application to the wound, the bi-component powders (QCS/Cat-SA) rapidly absorb plasma and dissolve into chains. These chains interact with each other to form a network, which can effectively bind and entraps clustered red blood cells and platelets, ultimately leading to the creation of a durable and robust thrombus. Significantly, these interconnected polymers adhere to the injury site, offering protection against thrombus disruption caused by the bloodstream. Benefiting from these synthetic properties, QCS/Cat-SA demonstrates superior hemostatic performance compared to commercial hemostatic powders like Celox™ in both arterial injuries and non-compressible liver puncture wounds. Importantly, QCS/Cat-SA exhibits excellent antibacterial activity, cytocompatibility, and hemocompatibility. These advantages of QCS/Cat-SA, including strong blood clotting, wet tissue adherence, antibacterial activity, biosafety, ease of use, and stable storage, make it a promising hemostatic agent for emergency situations.

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.

Cohering Plasma into Adhesive Gel by Natural Biopolymer-Nanoparticle Hybrid Powder for Efficient Hemostasis and Wound Healing

Hemostatic powder is commonly used in emergency bleeding control due to its suitability for irregularly shaped wounds, ease of use, and stable storage. However, traditional powder often has limited tissue adhesion and weak thrombus support, which makes it vulnerable to displacement by blood flow. Herein, we have developed a tricomponent hemostatic powder (MQS) composed of mesoporous bioactive glass nanoparticle (MBG), positively charged quaternized chitosan (QCS), and negatively charged catechol-modified alginate (SADA). Upon application to the wound, MBG with its high specific surface area quickly absorbs plasma, concentrating the blood coagulation factor. Simultaneously, the water-soluble QCS and SADA interact with each other and form a net, which can be further cross-linked by MBG. This network efficiently binds and entraps clustered blood coagulation factors, ultimately resulting in the formation of a durable and robust thrombus. Furthermore, the formed net adheres to the injury site, offering protection against thrombus disruption caused by the bloodstream. Benefiting from the synergistic effect of these three components, MQS demonstrates superior hemostatic performance compared to commercial hemostatic powders like Celox in both arterial injuries and noncompressible liver puncture wounds. Furthermore, MQS can effectively accelerate wound healing. In addition, MQS exhibits excellent antibacterial activity, cytocompatibility, and hemocompatibility. These advantages of MQS, including strong blood clotting, wet tissue adherence, antibacterial activity, wound healing ability, biosafety, ease of use, and stable storage, make it a promising hemostatic agent for emergency situations.