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

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.

Polysaccharides as submucosal injection materials (SIMs) in endoscopic resection: A comprehensive review

Submucosal injection materials (SIMs) play a vital role in the endoscopic treatment of benign and early malignant gastrointestinal lesions by effectively elevating lesions while significantly reducing the risks of thermal injury and bleeding. However, the traditional use of normal saline (NS) presents challenges due to its rapid absorption, which necessitates frequent reapplications and complicates procedural efficiency. Therefore, there is a pressing need for ideal SIMs that are cost-effective, readily available, and suitable for personalized therapy, while also demonstrating excellent biocompatibility and physicochemical stability. Recent advancements have highlighted the potential of polysaccharide-based natural polymers, such as sodium hyaluronate, cellulose, starch derivatives, chitosan, and sodium alginate, due to their superior biocompatibility and biodegradability. These polysaccharides have exhibited enhanced operational characteristics and therapeutic efficacy in animal and clinical studies. Nevertheless, ongoing research must address several challenges, including optimizing cost-effectiveness, improving mechanical strength and bioactivity, and mitigating intraoperative and postoperative complications. This review systematically examines the progress of polysaccharide-based natural polymers in SIMs, evaluates their current status and challenges in both research and clinical applications, and proposes future directions to enhance their utilization in gastrointestinal endoscopic therapy.

Temperature-sensitive injectable chitosan-based hydrogel for endoscopic submucosal dissection

Endoscopic submucosal dissection (ESD) is an effective treatment for polyps and early gastrointestinal cancers, but requires a high level of operator skill. Injecting submucosal materials (SIM) helps create a fluid cushion between the mucosal and muscular layers, making the procedure easier and reducing associated risks. However, SIMs commonly used in current clinical practice tend to spread quickly and fail to provide long-lasting submucosal fluid cushions (SFC). Thus, there is a critical need for a material that is easy to inject while also maintaining a durable barrier. We prepared succinylated hydroxybutyl chitosan (HBC-SA) by adding succinic anhydride (SA) to hydroxybutyl chitosan (HBC). The hydrogel had excellent temperature-sensitive properties and was able to be injected via an endoscopic injection needle even after gel formation. In vitro and in vivo studies showed that it has satisfactory biocompatibility. Functional experiments showed that the submucosal lifting properties of this hydrogel were significantly better than that of normal saline (NS) and sodium hyaluronate (SH), two commonly used clinical materials. In addition, the hydrogel possessed excellent hemostatic properties. Based on these results, HBC-SA is a promising candidate for submucosal injection during ESD.

Easily injectable gelatin-nonanal hydrogel for endoscopic resectioning of gastrointestinal polyps

The use of submucosal injection is crucial for satisfactory submucosal elevation in the early resection of flat polyps originating from the gastrointestinal tract (GIT). Injectable hydrogels derived from natural polypeptides are attractive candidates due to their excellent biocompatibility and easy gelation properties. However, most of the reported hydrogels are not the class of catheter delivery materials due to quick gelation, high inherent viscosity, and injection clogging. This study presents a novel injectable shear-thinning hydrogel platform of small molecules (nonanal) modified gelatin polymer, which offers a promising submucosal injection for effective removal of polyps from GIT. Physicochemical characterizations of hydrogel demonstrate the suitable features as an effective submucosal injection, including shear thinning property, self-assembly, methylene blue dye encapsulation, flow behavior, stability, syringeability (18 G, 21 G, and 24 G needles) and fibrous morphology. Ex vivo investigations of developed submucosal formulation on goat intestines demonstrate the enhanced visibility of cushions and the ability to produce stable, long-lasting cushions of about 8.07 mm up to ∼60 min of submucosal injection. The rapid blood clotting behavior of hydrogel was observed in about 120 s without compromising hemocompatibility with the hemolysis of about 3.77 % only. In vitro biocompatibility of the hydrogel was also verified using the HepG2 and nHDF cells. In vivo study depicts desirable biocompatibility, a non-toxic organ profile, and optimal cushion height in mice models. Studies established the foundation of novel submucosal fluid to improve the therapeutic outcomes of early resection for gastrointestinal polyps.

Injectable chitosan-polyvinylpyrrolidone composite thermosensitive hydrogels with sustained submucosal lifting for endoscopic submucosal dissection

To develop a submucosal injection material with sustained submucosal lifting for endoscopic submucosal dissection (ESD), this study designed and prepared a novel composite thermosensitive hydrogel system with high pH chitosan-polyvinylpyrrolidone-β-glycerophosphate (HpHCS-PVP-GP). HpHCS improved the injectability of the hydrogels and retained the rapid gelation ability at low concentrations. The modification of PVP significantly improved the stability of low-temperature hydrogel precursor solutions and the integrity of hydrogels formed at 37 °C through hydrogen bonds between PVP and HpHCS. A mathematical model was established using response surface methodology (RSM) to evaluate the synergistic effect of HpHCS, GP, and PVP concentrations on gelation time. This RSM model and submucosal lifting evaluation using in vitro pig esophageal models were used to determine the optimal formula of HpHCS-PVP-GP hydrogels. Although the higher PVP concentration (5 % (w/v)) prolonged gelation time, it improved hydrogel mechanical strength, resulting in better submucosal lifting performance. The experiments of Bama mini pigs showed that the heights of the cushions elevated by the HpHCS-5%PVP-GP hydrogel remained about 80 % 1 h after injection. Repeated injections were avoided, and the hydrogel had no cytotoxicity after electric cutting. Therefore, the HpHCS-PVP-GP thermosensitive hydrogel might be a promising submucosal injection material for ESD.

Injectable Modified Sodium Alginate Microspheres for Enhanced Operative Efficiency and Safety in Endoscopic Submucosal Dissection

Endoscopic submucosal dissection (ESD) is an effective method for resecting early-stage tumors in the digestive system. To achieve a low injection pressure of the injected fluid and continuous elevation of the mucosa following injection during the ESD technique, we introduced an innovative injectable sodium-alginate-based drug-loaded microsphere (Cipro-ThSA) for ESD surgery, which was generated through an emulsion reaction involving cysteine-modified sodium alginate (ThSA) and ciprofloxacin. Cipro-ThSA microspheres exhibited notable adhesiveness, antioxidant activity, and antimicrobial properties, providing a certain level of postoperative wound protection. In vitro cell assays confirmed the decent biocompatibility of the material. Lastly, according to animal experiments involving submucosal elevation of porcine colons, Cipro-ThSA microspheres ensure surgically removable lift height while maintaining the mucosa for approximately 246% longer than saline, which could effectively reduce surgical risks while providing sufficient time for operation. Consequently, the Cipro-ThSA microsphere holds great promise as a novel submucosal injection material, in terms of enhancing the operational safety and effectiveness of ESD surgery.