Modular stimuli-responsive hydrogel sealants for early gastrointestinal leak detection and containment

Real-time detection of gastrointestinal leaks via bismuth chelate-enhanced X-ray gastroenterography

Anastomotic leaks are among the most dreaded complications following gastrointestinal (GI) surgery, and contrast-enhanced X-ray gastroenterography is considered the preferred initial diagnostic method for GI leaks. However, from fundamental research to clinical practice, the only oral iodinated contrast agents currently available for GI leaks detection are facing several challenges, including low sensitivity, iodine allergy, and contraindications in patients with thyroid diseases. Herein, we propose a cinematic contrast-enhanced X-ray gastroenterography for the real-time detection of GI leaks with an iodine-free bismuth chelate (Bi-DTPA) for the first time. The Bi-DTPA, synthesized through a straightforward one-pot method, offers distinct advantages such as no need for purification, a nearly 100 % yield, large-scale production capability, and good biocompatibility. The remarkable X-ray attenuation properties of Bi-DTPA enable real-time dynamic visualization of whole GI tract under both X-ray gastroenterography and computed tomography (CT) imaging. More importantly, the leaky site and severity can be both clearly displayed during Bi-DTPA-enhanced gastroenterography in a rat model with esophageal leakage. The proposed movie-like Bi-DTPA-enhanced X-ray imaging approach presents a promising alternative to traditional GI radiography based on iodinated molecules. It demonstrates significant potential in addressing concerns related to iodine-associated adverse effects and offers an alternative method for visually detecting gastrointestinal leaks.

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.

Artificial intelligence in surgery

Artificial intelligence (AI) is rapidly emerging in healthcare, yet applications in surgery remain relatively nascent. Here we review the integration of AI in the field of surgery, centering our discussion on multifaceted improvements in surgical care in the preoperative, intraoperative and postoperative space. The emergence of foundation model architectures, wearable technologies and improving surgical data infrastructures is enabling rapid advances in AI interventions and utility. We discuss how maturing AI methods hold the potential to improve patient outcomes, facilitate surgical education and optimize surgical care. We review the current applications of deep learning approaches and outline a vision for future advances through multimodal foundation models.

A Laparoscopically Compatible Rapid-Adhesion Bioadhesive for Asymmetric Adhesion, Non-Pressing Hemostasis, and Seamless Seal

Bioadhesive hydrogels offer unprecedented opportunities in hemostatic agents and tissue sealing; however, the application of existing bioadhesive hydrogels through narrow spaces to achieve strong adhesion in fluid-rich physiological environments is challenged either by undesired indiscriminate adhesion or weak wet tissue adhesion. Here, a laparoscopically compatible asymmetric adhesive hydrogel (aAH) composed of sprayable adhesive hydrogel powders and injectable anti-adhesive glue is proposed for hemostasis and to seal the bloody tissues in a non-pressing way, allowing for preventing postoperative adhesion. The powders can seed on the irregular bloody wound to rapidly absorb interfacial fluid, crosslink, and form an adhesive hydrogel to hemostatic seal (blood clotting time and tissue sealing in 10 s, ≈200 mm Hg of burst pressure in sealed porcine tissues). The aAH can be simply formed by crosslinking the upper powder with injectable glue to prevent postoperative adhesion (adhesive strength as low as 1 kPa). The aAH outperforms commercial hemostatic agents and sealants in the sealing of bleeding organs in live rats, demonstrating superior anti-adhesive efficiency. Further, the hemostatic seamless sealing by aAH succeeds in shortening the time of warm ischemia, decreasing the blood loss, and reducing the possibility of rebleeding in the porcine laparoscopic partial nephrectomy model.

Injectable Asymmetric Adhesive-Antifouling Bifunctional Hydrogel for Peritoneal Adhesion Prevention

Peritoneal adhesion is a common problem after abdominal surgery and can lead to various medical problems. In response to the lack of in situ retention and pro-wound healing properties of existing anti-adhesion barriers, this work reports an injectable adhesive-antifouling bifunctional hydrogel (AAB-hydrogel). This AAB-hydrogel can be constructed by "two-step" injection. The tissue adhesive hydrogel based on gallic acid-modified chitosan and aldehyde-modified dextran is prepared as the bottom hydrogel (B-hydrogel) by Schiff base reaction. The aldehyde-modified zwitterionic dextran/carboxymethyl chitosan-based hydrogel is formed on the B-hydrogel surface as the antifouling top hydrogel (T-hydrogel). The AAB-hydrogel exhibits good bilayer binding and asymmetric properties, including tissue adhesive, antifouling, and antimicrobial properties. To evaluate the anti-adhesion effect in vivo, the prepared hydrogels are injected onto the wound surface of a mouse abdominal wall abrasion-cecum defect model. Results suggest that the AAB-hydrogel has antioxidant capacity and can reduce the postoperative inflammatory response by modulating the macrophage phenotype. Moreover, the AAB-hydrogel could effectively inhibit the formation of postoperative adhesions by reducing protein deposition, and resisting fibroblast adhesions and bacteria attacking. Therefore, AAB-hydrogel is a promising candidate for the prevention of postoperative peritoneal adhesions.

Phase transition of GvpU regulates gas vesicle clustering in bacteria

Gas vesicles (GVs) are microbial protein organelles that support cellular buoyancy. GV engineering has multiple applications, including reporter gene imaging, acoustic control and payload delivery. GVs often cluster into a honeycomb pattern to minimize occupancy of the cytosol. The underlying molecular mechanism and the influence on cellular physiology remain unknown. Using genetic, biochemical and imaging approaches, here we identify GvpU from Priestia megaterium as a protein that regulates GV clustering in vitro and upon expression in Escherichia coli. GvpU binds to the C-terminal tail of the core GV shell protein and undergoes a phase transition to form clusters in subsaturated solution. These properties of GvpU tune GV clustering and directly modulate bacterial fitness. GV variants can be designed with controllable sensitivity to GvpU-mediated clustering, enabling design of genetically tunable biosensors. Our findings elucidate the molecular mechanisms and functional roles of GV clustering, enabling its programmability for biomedical applications.

50-nm Gas-Filled Protein Nanostructures to Enable the Access of Lymphatic Cells by Ultrasound Technologies

Ultrasound imaging and ultrasound-mediated gene and drug delivery are rapidly advancing diagnostic and therapeutic methods; however, their use is often limited by the need for microbubbles, which cannot transverse many biological barriers due to their large size. Here, the authors introduce 50-nm gas-filled protein nanostructures derived from genetically engineered gas vesicles(GVs) that are referred to as 50 nmGVs. These diamond-shaped nanostructures have hydrodynamic diameters smaller than commercially available 50-nm gold nanoparticles and are, to the authors' knowledge, the smallest stable, free-floating bubbles made to date. 50 nmGVs can be produced in bacteria, purified through centrifugation, and remain stable for months. Interstitially injected 50 nmGVs can extravasate into lymphatic tissues and gain access to critical immune cell populations, and electron microscopy images of lymph node tissues reveal their subcellular location in antigen-presenting cells adjacent to lymphocytes. The authors anticipate that 50 nmGVs can substantially broaden the range of cells accessible to current ultrasound technologies and may generate applications beyond biomedicine as ultrasmall stable gas-filled nanomaterials.

Macrophage-mediated fracture healing: Unraveling molecular mechanisms and therapeutic implications using hydrogel-based interventions

Fracture healing is a complex biological process that involves the orchestrated interplay of various cells and molecular signaling pathways. Among the key players, macrophages have emerged as critical regulators of fracture repair, influencing inflammation, tissue remodeling, and angiogenesis. Recent advances in hydrogel-based therapeutics have provided exciting opportunities to leverage the modulatory effects of macrophages for improving fracture healing outcomes. In the present study, we review the importance of macrophages in fracture repair and their potential therapeutic role in hydrogel-based interventions. We discuss the molecular mechanisms underlying macrophage-mediated effects on fracture healing, and how hydrogels can be utilized as a platform for macrophage modulation. Furthermore, we highlight the translation of hydrogel-based therapies from bench to bedside, including preclinical and clinical studies, and the challenges and opportunities in harnessing the therapeutic potential of macrophages in fracture repair. Overall, understanding the importance of macrophages in fracture healing and the potential of hydrogel-based therapeutics to modulate macrophage responses can pave the way for developing innovative approaches to improve fracture healing outcomes.

Reversible Mechanical Contraception and Endometriosis Treatment Using Stimuli-Responsive Hydrogels

Female sterilization via fallopian tube ligation is a common procedure; However, after the operation, over 10% of women seek re-fertilization, which is frequently unsuccessful. In addition, there is evidence that fallopian tubes contribute to the spread of endometriotic tissue as they serve as channels for proinflammatory media entering the abdominal cavity via retrograde menstruation. Here, stimuli-degradable hydrogel implants are presented for the functional, biocompatible, and reversible occlusion of fallopian tubes. The hydrogel implants, designed with customized swelling properties, mechanically occlude fallopian tubes in a high-performance manner with burst pressures reaching 255-558 mmHg, exceeding normal abdominal pressures (95 mmHg). Their damage-free removal can be achieved within 30 min using near-visible UV light or a glutathione solution, employing a method akin to standard fallopian tube perfusion diagnostics. Ultrasound-guided implant placement is demonstrated using a clinical hysteroscope in a human-scale uterus model and biocompatibility in a porcine in vivo model. Importantly, the prevention of live sperm as well as endometrial cell passage through blocked fallopian tubes is demonstrated. Overall, a multifunctional system is presented that constitutes a possible means of on-demand, reversible contraception along with the first-ever mechanical approach to abdominal endometriosis prevention and treatment.

A magnetic multi-layer soft robot for on-demand targeted adhesion

Magnetic soft robots have shown great potential for biomedical applications due to their high shape reconfigurability, motion agility, and multi-functionality in physiological environments. Magnetic soft robots with multi-layer structures can enhance the loading capacity and function complexity for targeted delivery. However, the interactions between soft entities have yet to be fully investigated, and thus the assembly of magnetic soft robots with on-demand motion modes from multiple film-like layers is still challenging. Herein, we model and tailor the magnetic interaction between soft film-like layers with distinct in-plane structures, and then realize multi-layer soft robots that are capable of performing agile motions and targeted adhesion. Each layer of the robot consists of a soft magnetic substrate and an adhesive film. The mechanical properties and adhesion performance of the adhesive films are systematically characterized. The robot is capable of performing two locomotion modes, i.e., translational motion and tumbling motion, and also the on-demand separation with one side layer adhered to tissues. Simulation results are presented, which have a good qualitative agreement with the experimental results. The feasibility of using the robot to perform multi-target adhesion in a stomach is validated in both ex-vivo and in-vivo experiments.

Nanothermometry-Enabled Intelligent Laser Tissue Soldering

While often life-saving, surgical resectioning of diseased tissues puts patients at risk for post-operative complications. Sutures and staples are well-accepted and routinely used to reconnect tissues, however, their mechanical mismatch with biological soft tissue and invasiveness contribute to wound healing complications, infections, and post-operative fluid leakage. In principle, laser tissue soldering offers an attractive, minimally-invasive alternative for seamless soft tissue fusion. However, despite encouraging experimental observations, including accelerated healing and lowered infection risk, critical issues related to temperature monitoring and control during soldering and associated complications have prevented their clinical exploitation to date. Here, intelligent laser tissue soldering (iSoldering) with integrated nanothermometry is introduced as a promising yet unexplored approach to overcome the critical shortcomings of laser tissue soldering. It demonstrates that adding thermoplasmonic and nanothermometry nanoparticles to proteinaceous solders enables heat confinement and non-invasive temperature monitoring and control, offering a route to high-performance, leak-tight tissue sealing even at deep tissue sites. The resulting tissue seals exhibit excellent mechanical properties and resistance to chemically-aggressive digestive fluids, including gastrointestinal juice. The iSolder can be readily cut and shaped by surgeons to optimally fit the tissue defect and can even be applied using infrared light from a medically approved light source, hence fulfilling key prerequisites for application in the operating theatre. Overall, iSoldering enables reproducible and well-controlled high-performance tissue sealing, offering new prospects for its clinical exploitation in diverse fields ranging from cardiovascular to visceral and plastic surgery.

Design of stretchable and self-powered sensing device for portable and remote trace biomarkers detection

Timely and remote biomarker detection is highly desired in personalized medicine and health protection but presents great challenges in the devices reported so far. Here, we present a cost-effective, flexible and self-powered sensing device for H2S biomarker analysis in various application scenarios based on the structure of galvanic cells. The sensing mechanism is attributed to the change in electrode potential resulting from the chemical adsorption of gas molecules on the electrode surfaces. Intrinsically stretchable organohydrogels are used as solid-state electrolytes to enable stable and long-term operation of devices under stretching deformation or in various environments. The resulting open-circuit sensing device exhibits high sensitivity, low detection limit, and excellent selectivity for H2S. Its application in the non-invasive halitosis diagnosis and identification of meat spoilage is demonstrated, emerging great commercial value in portable medical electronics and food security. A wireless sensory system has also been developed for remote H2S monitoring with the participation of Bluetooth and cloud technologies. This work breaks through the shortcomings in the traditional chemiresistive sensors, offering a direction and theoretical foundation for designing wearable sensors catering to other stimulus detection requirements.

Surgical Sealant with Integrated Shape-Morphing Dual Modality Ultrasound and Computed Tomography Sensors for Gastric Leak Detection

Postoperative anastomotic leaks are the most feared complications after gastric surgery. For diagnostics clinicians mostly rely on clinical symptoms such as fever and tachycardia, often developing as a result of an already fully developed, i.e., symptomatic, surgical leak. A gastric fluid responsive, dual modality, electronic-free, leak sensor system integrable into surgical adhesive suture support materials is introduced. Leak sensors contain high atomic number carbonates embedded in a polyacrylamide matrix, that upon exposure to gastric fluid convert into gaseous carbon dioxide (CO2 ). CO2 bubbles remain entrapped in the hydrogel matrix, leading to a distinctly increased echogenic contrast detectable by a low-cost and portable ultrasound transducer, while the dissolution of the carbonate species and the resulting diffusion of the cation produces a markedly reduced contrast in computed tomography imaging. The sensing elements can be patterned into a variety of characteristic shapes and can be combined with nonreactive tantalum oxide reference elements, allowing the design of shape-morphing sensing elements visible to the naked eye as well as artificial intelligence-assisted automated detection. In summary, shape-morphing dual modality sensors for the early and robust detection of postoperative complications at deep tissue sites, opening new routes for postoperative patient surveillance using existing hospital infrastructure is reported.

Biologically inspired gastrointestinal stapler design: "Getting to Zero" complications

As next generation stapling devices enter the marketplace with robotic adaptations, tri-staple technology, preloaded reinforcement materials, etc., in this perspective piece we assert that a "refresh" in our understanding of the mechanisms of action of these devices is needed. While much attention has been paid to explain the mechanical features of one device versus another, it seems that little to no attention is being paid to understand how an intestinal anastomosis responds biologically to the variations in their use and design. Here we will review various aspects of gastrointestinal stapling in the context of emerging technology in the field and expose the gaps in knowledge that exist regarding the effect of gastrointestinal stapling on the biology of healing.

50-nm gas-filled protein nanostructures to enable the access of lymphatic cells by ultrasound technologies

Ultrasound imaging and ultrasound-mediated gene and drug delivery are rapidly advancing diagnostic and therapeutic methods; however, their use is often limited by the need of microbubbles, which cannot transverse many biological barriers due to their large size. Here we introduce 50-nm gas-filled protein nanostructures derived from genetically engineered gas vesicles that we referred to as 50nm GVs. These diamond-shaped nanostructures have hydrodynamic diameters smaller than commercially available 50-nm gold nanoparticles and are, to our knowledge, the smallest stable, free-floating bubbles made to date. 50nm GVs can be produced in bacteria, purified through centrifugation, and remain stable for months. Interstitially injected 50nm GVs can extravasate into lymphatic tissues and gain access to critical immune cell populations, and electron microscopy images of lymph node tissues reveal their subcellular location in antigen-presenting cells adjacent to lymphocytes. We anticipate that 50nm GVs can substantially broaden the range of cells accessible to current ultrasound technologies and may generate applications beyond biomedicine as ultrasmall stable gas-filled nanomaterials.

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.