Robust closure of post-endoscopic submucosal dissection perforation by microparticle-based wound dressing

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.

Konjac glucomannan/sodium alginate/ε-poly-l-lysine hydrogel promotes esophageal and colonic wound healing

Endoscopic submucosal dissection (ESD) is widely used to treat gastrointestinal mucosal and submucosal lesions. However, it may cause bleeding, perforation, and stricture. Although these complications can be avoided by introducing materials such as polyglycolic acid and carboxymethyl cellulose sheets, such approaches are expensive and time-consuming. Herein, we report a hydrogel prepared by combining a colloidal solution composed of konjac glucomannan (KGM) and sodium alginate (SA) and a fixative solution containing ε-poly-l-lysine (ε-PLL) and calcium chloride. The two solutions were mixed on the wound surface to form the KGM/SA/ε-PLL hydrogel through hydrogen bonds, coordination bonds, and electrostatic attraction. The effectiveness and convenience of applying the KGM/SA/ε-PLL hydrogel to promote wound healing in the esophagus and colon were assessed in vitro and in vivo. We found that the hydrogel stimulated epithelial proliferation, reduced inflammation, promoted recapillarization, and inhibited fibrosis in the esophagus and colon. Therefore, the KGM/SA/ε-PLL hydrogel is an effective and convenient agent that can promote post-ESD wound healing and is recommended for ulcer bed protection in daily clinical practice.

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.

Effect of sprayable, highly adhesive hydrophobized gelatin microparticles on esophageal stenosis after endoscopic submucosal dissection: an experimental study in a swine model

BACKGROUND

Esophageal mucosal resection for superficial esophageal cancer can lead to postoperative esophageal stricture, with current preventive measures being insufficient. Sprayable wound dressings containing hydrophobized microparticles exhibit strong adhesion. This study aimed to investigate the preventive effects of hydrophobized microparticles on esophageal stenosis following endoscopic submucosal dissection.

METHODS

Circumferential esophageal endoscopic submucosal dissection was performed on miniature swine (n = 6). Swine were categorized into two groups: those sprayed with hydrophobized microparticles (sprayed group) and those not sprayed (non-sprayed group). Hydrophobized microparticles were sprayed onto the sprayed group on Days 0, 3, and 7 of endoscopic submucosal dissection. The non-sprayed group underwent endoscopy on the same days. Esophageal stricture rate, submucosal inflammatory cell infiltration, submucosal fibrosis, and thickening of the muscular layer were compared between the groups on Day 14 of endoscopic submucosal dissection.

RESULTS

Spraying of hydrophobized microparticles was easily performed using an existing endoscopic spraying device. The esophageal stricture rate was significantly lower in the sprayed group than in the non-sprayed group (76.1% versus 90.6%, p < 0.05). The sprayed group showed suppression of inflammatory cell infiltration in the submucosal layer (p < 0.01) and thickening of the muscular layer (p < 0.01).

CONCLUSIONS

Sprayable tissue-adhesive hydrophobized microparticles reduce the stricture rate after esophageal ESD by inhibiting inflammatory cell infiltration, submucosal fibrosis, and thickening of the muscular layer. The use of hydrophobized microparticles for preventing post-endoscopic submucosal dissection esophageal stenosis offers a promising avenue for clinical applications in endoscopic procedures, potentially improving patient outcomes.

Development of a Janus tissue adhesive hemostatic patch based on hydrophobically-modified Alaska pollock gelatin

Uncontrollable hemorrhage from trauma and open surgery leads to a high percentage of death. Even though some patch-type hemostatic materials have been used in the clinic, sufficient tissue adhesion property and the management of tissue adhesion and anti-adhesion have been the challenges. In this report, we designed Janus tissue adhesive hemostatic patch, consisting of Alaska pollock gelatin (Org-ApGltn) as a support layer and decanoyl group-modified ApGltn (C10-ApGltn) with pentaerythritol poly(ethylene glycol) ether tetrasuccinimidyl glutarate (4S-PEG) as an adhesive layer, named as the C10-ApGltn patch. The C10-ApGltn patch adhered onto blood vessel surface by the activation 4S-PEG and hydrophobic groups in C10-ApGltn through the covalent bond formation and physical interaction. The burst strength of the C10-ApGltn patch was optimized in terms of the degree of substitution, the molecular weight of 4S-PEG, the concentration of C10-ApGltn, and the NHS/NH2 ratio. The optimized C10-ApGltn patch showed significantly higher burst strength with commercially available TachoSil®. The C10-ApGltn patch showed enzymatic degradability in a buffer solution with collagenase. In a rat liver hemorrhage model, the C10-ApGltn patch acted as a sealant on the hemorrhage site and exhibited competitive hemostatic property to TachoSil®.

Impact of hydrophobic modification on biocompatibility of Alaska pollock gelatin microparticles

This study investigates the impact of hydrophobic modification on the immunogenicity, cytotoxicity, and inflammatory response of Alaska pollock gelatin (ApGltn) microparticles (MPs). Gelatin, known for its inherent biocompatibility, was modified with decyl group (C10) to explore potential alterations in its interaction with the immune system. Immunogenicity was evaluated through the measurement of material-specific IgM and IgG responses, indicating no significant increase post-modification. Cytotoxicity against Caco-2 cell lines and NF-κB-mediated LPS-induced inflammation were also assessed, revealing no exacerbation by the modified MPs. Furthermore, C10 modification with different types of linkage such as secondary amine and amide structure did not influence immune reactivity. These findings suggest that C10 modification maintains the non-immunogenicity and biocompatibility of gelatin MPs, supporting their potential use in biomedical applications.

Sprayable Hydrogel Sealant for Gastrointestinal Wound Shielding

Naturally occurring internal bleeding, such as in stomach ulcers, and complications following interventions, such as polyp resection post-colonoscopy, may result in delayed (5-7 days) post-operative adverse events-such as bleeding, intestinal wall perforation, and leakage. Current solutions for controlling intra- and post-procedural complications are limited in effectiveness. Hemostatic powders only provide a temporary solution due to their short-term adhesion to GI mucosal tissues (less than 48 h). In this study, a sprayable adhesive hydrogel for facile application and sustained adhesion to GI lesions is developed using clinically available endoscopes. Upon spraying, the biomaterial (based on polyethyleneimine-modified Pluronic micelles precursor and oxidized dextran) instantly gels upon contact with the tissue, forming an adhesive shield. In vitro and in vivo studies in guinea pigs, rabbits, and pig models confirm the safety and efficacy of this biomaterial in colonic and acidic stomach lesions. The authors' findings highlight that this family of hydrogels ensures prolonged tissue protection (3-7 days), facilitates wound healing, and minimizes the risk of delayed complications. Overall, this technology offers a readily adoptable approach for gastrointestinal wound management.

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.

Improved hydration property of tissue adhesive/hemostatic microparticle based on hydrophobically-modified Alaska pollock gelatin

The management of bleeding is an important aspect of endoscopic surgery to avoid excessive blood loss and minimize pain. In clinical settings, sprayable hemostatic particles are used for their easy delivery, adaptability to irregular shapes, and rapid hydration. However, conventional hemostatic particles present challenges associated with tissue adhesion. In a previous study, we reported tissue adhesive microparticles (C10-sa-MPs) derived from Alaska pollock gelatin modified with decyl groups (C10-sa-ApGltn) using secondary amines as linkages. The C10-sa-MPs adhere to soft tissues through a hydration mechanism. However, their application as a hemostatic agent was limited by their long hydration times, attributed to their high hydrophobicity. In this study, we present a new type microparticle, C10-am-MPs, synthesized by incorporating decanoyl group modifications into ApGltn (C10-am-ApGltn), using amide bonds as linkages. C10-am-MPs exhibited enhanced hydration characteristics compared to C10-sa-MPs, attributed to superior water absorption facilitated by amide bonds rather than secondary amines. Furthermore, C10-am-MPs demonstrated comparable tissue adhesion properties and underwater adhesion stability to C10-sa-MPs. Notably, C10-am-MPs exhibited accelerated blood coagulation in vitro compared to C10-sa-MPs. The application of C10-am-MPs in an in vivo rat liver hemorrhage model resulted in a hemostatic effect comparable to a commercially available hemostatic particle. These findings highlight the potential utility of C10-am-MPs as an effective hemostatic agent for endoscopic procedures and surgical interventions.

Sprayable tissue adhesive microparticle-magnetic nanoparticle composites for local cancer hyperthermia

Incomplete removal of early-stage gastrointestinal cancers by endoscopic treatments often leads to recurrence induced by residual cancer cells. To completely remove or kill cancer tissues and cells and prevent recurrence, chemotherapy, radiotherapy, and hyperthermia using biomaterials with drugs or nanomaterials are usually administered following endoscopic treatments. However, there are few biomaterials that can be applied using endoscopic devices to locally kill cancer tissues and cells. We previously reported that decyl group-modified Alaska pollock gelatin-based microparticles (denoted C10MPs) can adhere to gastrointestinal tissues under wet conditions through the formation of a colloidal gel driven by hydrophobic interactions. In this study, we combined C10MPs with superparamagnetic iron oxide nanoparticles (SPIONs) to develop a sprayable heat-generating nanomaterial (denoted SP/C10MP) for local hyperthermia of gastrointestinal cancers. The rheological property, tissue adhesion strength, burst strength, and underwater stability of SP/C10MP were improved through decyl group modification and SPION addition. Moreover, SP/C10MP that adhered to gastrointestinal tissues formed a colloidal gel, which locally generated heat in response to an alternating magnetic field. SP/C10MP successfully killed cancer tissues and cells in colon cancer-bearing mouse models in vitro and in vivo. Therefore, SP/C10MP has the potential to locally kill residual cancer tissues and cells after endoscopic treatments.

A review of hydrogels used in endoscopic submucosal dissection for intraoperative submucosal cushions and postoperative management

Endoscopic submucosal dissection (ESD) has been clinically proved to have prominent advantages in the treatment of early gastrointestinal cancers over traditional surgery, including less trauma, fewer complications, a quicker recovery and lower costs. During the procedure of ESD, appropriate and multifunctional submucosal injected materials (SIMs) as submucosal cushions play an important role, however, even with many advances in design strategies of SIMs over the past decades, the performance of the submucosal cushions with postoperative management function seems to be still unsatisfactory. In this review, we gave a brief historical recount about the clinical development of SIMs, then some common applications of hydrogels used as SIMs in ESD were summarized, while an account of the universal challenges during ESD procedure was also outlined. Going one step further, some cutting-edge functional strategies of hydrogels for novel applications in ESD were exhibited. Finally, we concluded the advantages of hydrogels as SIMs for ESD as well as the treatment dilemma clinicians faced when it comes to deeply infiltrated lesions, some technical perspectives about linking the clinical demand with commercial supply were also proposed. Encompassing the basic elements of SIMs used in ESD surgery and the corresponding postoperative management requirements, this review could be a good reference for relevant practitioners in expanding the research horizon and improving the well-being index of patients.

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.

Effect of particle size on the tissue adhesion and particle floatation of a colloidal wound dressing for endoscopic treatments

Endoscopic submucosal dissection (ESD) is a minimally invasive technique that is widely used to remove gastrointestinal tumors. However, because the walls of the duodenum and large intestine are thin, perforation can easily occur after ESD. We have previously reported that alkyl group-modified Alaska pollock gelatin-based microparticles (C10Ps) formed a colloidal gel that could adhere to defects and close perforations, driven by hydrophobic interactions. The present study focused on the effect of particle size on the colloidal gel properties and the floatation of C10Ps in the air in the delivery of C10Ps. We prepared C10Ps with different particle sizes from 0.1 to 100 µm. The storage modulus and adhesion strength of the C10P colloidal gel increased with decreasing particle size. All the C10Ps formed a colloidal gel layer on duodenum tissue after being sprayed from an endoscopic device. The underwater stability and burst strength of C10Ps with a particle size of 0.1 and 1 µm were higher than for larger C10Ps. Floating of the small-sized C10Ps in the air was observed. The results indicated that C10Ps with a size of 1 µm had suitable properties for use in endoscopic treatments. STATEMENT OF SIGNIFICANCE: We previously reported tissue adhesive microparticles as a spray-deliverable wound dressing in gastrointestinal tissues. However, their functions depending on particle size have not yet been clarified. In the present study, we prepared decyl group-modified Alaska pollock gelatin nano and microparticles (C10Ps) with different particle sizes from 0.1 to 100 µm and evaluated the effect of particle size on the colloidal gel properties (rheological property, underwater stability and perforation-closing ability) and the floatation of C10Ps in the air in the delivery of C10Ps.

Endoscopy Deliverable and Mushroom-Cap-Inspired Hyperboloid-Shaped Drug-Laden Bioadhesive Hydrogel for Stomach Perforation Repair

Gastrointestinal tract perforation is a full-thickness injury that causes bleeding and fatal infection of the peritoneum. This condition worsens in an acidic gastric environment which interferes with the normal coagulation cascade. Current endoscopic clips to repair gastric perforations are ineffective, and metal or plastic occluders need secondary surgery to remove them. Herein, we report a self-expandable, endoscopy deliverable, adhesive hydrogel to block gastric perforation. We found the nanosilica coating significantly enhanced the adhesive strength even under a simulated strong acidic stomach environment. The developed device was disulfide cross-linked for the reducible degraded gel. By loading with vonoprazan fumarate (VF) and acidic fibroblast growth factor (AFGF), the hyperboloid-shaped device can have a sustained drug release to regulate intragastric pH and promote wound healing. The gel device can be compressed and then expanded like a mushroom when applied in an acute gastric perforation model in both rabbits and minipigs. By utilizing a stomach capsule robot for remotely monitoring the pH and by immunohistochemical analysis, we demonstrated that the compressible hyperboloid-shaped gel could stably block the perforation and promoted wound healing during the 28 days of observation. The real-time pH meter demonstrated that the gel could control intragastric pH above 4 for nearly 60 h to prevent bleeding.

Prevention of postoperative adhesion with a colloidal gel based on decyl group-modified Alaska pollock gelatin microparticles

Postoperative adhesion, bonding of the abdominal wall to damaged organs, causes severe complications after abdominal surgery. Despite the availability of physical barriers (i.e., solutions, films, and hydrogels), adhesion prevention materials that are a single-substance system with stability in wet tissue and ease of use have not been reported. Here, we report a microparticle based, sprayable adhesion prevention material comprising decyl group modified Alaska pollock gelatin (C10-ApGltn). C10-ApGltn microparticles (C10-MPs) were prepared by a coacervation method, freeze drying, and thermal crosslinking. The C10-MPs adhered to and formed a colloidal gel layer on intestinal serosal tissue by hydration without any crosslinking agents. After hydration of the C10-MPs, the resulting colloidal gel layer did not adhere to other tissues. Additionally, the C10-MP colloidal gel layer formed on the stomach serosal tissue showed stability when submersed in saline for 2 days. The colloidal gel layer also showed tissue followability. An in vivo rat adhesion model revealed that C10-MP colloidal gel layer on the cecum and abdominal wall defects effectively reduced postoperative adhesion and induced tissue remodeling, including re-mesothelialization. Therefore, C10-MPs are a potential anti-adhesion material for preventing postoperative adhesion. STATEMENT OF SIGNIFICANCE: We evaluated the postoperative adhesion prevention ability of a colloidal gel based on decyl group modified Alaska pollock gelatin (ApGltn) microparticles (C10-MPs). These microparticles are sprayable and form a colloidal gel with only hydration on the gastrointestinal tissue. We revealed that the modification of the decyl group into ApGltn improved the stability of C10-MP colloidal gel on the tissue by hydrophobic interaction in the in-vitro experiments. The gel prevented postoperative adhesion by being a physical barrier in the in-vivo rat adhesion model.