A blood-resistant surgical glue for minimally invasive repair of vessels and heart defects

Robust tetra-armed poly (ethylene glycol)-based hydrogel as tissue bioadhesive for the efficient repair of meniscus tears

Repair and preservation of the injured meniscus has become paramount in clinical practice. However, the complexities of various clinic stitching techniques for meniscus repair pose challenges for grassroots doctors. Hence, there is a compelling interest in innovative therapeutic strategies such as bioadhesives. An ideal bioadhesive must cure quickly in aqueous and blood environments, bind strongly, endure arthroscopic washing pressures, and degrade appropriately for tissue regeneration. Here, we present a tetra-poly (ethylene glycol) (PEG)-based hydrogel bioadhesive, boasting high biocompatibility, ultrafast gelation, facile injectable operation, and favorable mechanical strength. In view of the synergistic effects of chemical anchor and physical chain entanglement to tightly bind the meniscus, a seamless interface was formed between the surrounding meniscal tissues and hydrogels, enabling the longitudinal tear of the meniscus fused in situ to withstand large tensile force with the adhesive strength of 541.5 ± 31.4 kPa and arthroscopic washout resistance of 29.4 kPa. Superior to existing commercial adhesives, ours allows sutureless application and arthroscopic assistance, without requiring specialized clinical skills. This research is expected to significantly impact our understanding of meniscal healing and ultimately promote a simpler process for achieving functional and structural recovery in torn menisci.

Blue Laser Triggered Hemostatic Peptide Hydrogel for Gastrointestinal Bleeding Treatment

In an emergency, nonvariceal upper gastrointestinal bleeding (NVUGIB), endoscopic hemostasis is considered the gold standard intervention. However, current endoscopic hemostasis is very challenging to manage bleeding in large-diameter or deep lesions highly prone to rebleeding risk. Herein, a novel hemostatic peptide hydrogel (HPH) is reported, consisting of a self-assembly peptide sequence CFLIVIGSIIVPGDGVPGDG (PFV) and gelatin methacryloyl (GelMA), which can be triggered by blue laser endoscopy (BLE) for nonvariceal upper gastrointestinal bleeding treatment without recurring bleeding concerns. Upon contact with GelMA solution, PFV immediately fibrillates into β-sheet nanofiber and solvent-induced self-assembly to form HPH gel. HPH nanofiber networks induced ultrafast coagulation by enveloping blood cells and activating platelets and coagulation factors even to the blood with coagulopathy. Besides its remarkable hemostatic performance in artery and liver injury models, HPH achieves instant bleeding management in porcine NVUGIB models within 60 s by preventing the rebleeding risk. This work demonstrates an extraordinary hemostatic agent for NVUGIB intervention by BLE for the first time, broadening potential application scenarios, including patients with coagulopathy and promising clinical prospects.

Robust tissue adhesion in biomedical applications: enhancing polymer stability in an injectable protein-based hydrogel

Protein-based hydrogels are appealing materials for a variety of therapeutic uses because they are compatible, biodegradable, and adaptable to biological and chemical changes. Therefore, adherent varieties of hydrogels have received significant study; nevertheless, the majority of them show weak mechanical characteristics, transient adherence, poor biocompatibility activity, and low tensile strength. Here we are reporting, a two-component (BSA-gelatin) protein solution crosslinked with Tetrakis (hydroxymethyl) phosphonium chloride (THPC) to form a novel hydrogel. Compared with classical adhesive hydrogels, this hydrogel showed enhanced mechanical properties, was biocompatible with L929 cells, and had minimal invasive injectability. A considerable, high tensile strength of 73.33 ± 11.54 KPa and faultless compressive mechanical properties of 173 KPa at 75% strain were both demonstrated by this adhesive hydrogel. Moreover, this maximum tissue adhesion strength could reach 18.29 ± 2.22 kPa, significantly higher than fibrin glue. Cell viability was 97.09 ± 6.07%, which indicated that these hydrogels were non-toxic to L929. The fastest gelation time of the BSA-gelatin hydrogel was 1.25 ± 0.17 min at physiological pH and 37 °C. Therefore, the obtained novel work can potentially serve as a tissue adhesive hydrogel in the field of biomedical industries.

Wireless Magnetic Robot for Precise Hierarchical Control of Tissue Deformation

Mechanotherapy has emerged as a promising treatment for tissue injury. However, existing robots for mechanotherapy are often designed on intuition, lack remote and wireless control, and have limited motion modes. Herein, through topology optimization and hybrid fabrication, wireless magneto-active soft robots are created that can achieve various modes of programmatic deformations under remote magnetic actuation and apply mechanical forces to tissues in a precise and predictable manner. These soft robots can quickly and wirelessly deform under magnetic actuation and are able to deliver compressing, stretching, shearing, and multimodal forces to the surrounding tissues. The design framework considers the hierarchical tissue-robot interaction and, therefore, can design customized soft robots for different types of tissues with varied mechanical properties. It is shown that these customized robots with different programmable motions can induce precise deformations of porcine muscle, liver, and heart tissues with excellent durability. The soft robots, the underlying design principles, and the fabrication approach provide a new avenue for developing next-generation mechanotherapy.

Biomechanical Evaluation of an Atraumatic Polymer-assisted Peripheral Nerve Repair System Compared with Conventional Neurorrhaphy Techniques

Background

Microsuturing, the gold standard for peripheral nerve repair, can create tension and damage at the repair site, potentially impacting regeneration and causing neuroma formation. A sutureless and atraumatic polymer-assisted system was developed to address this challenge and support peripheral nerve repair. The system is based on a biocompatible and biodegradable biosynthetic polymer and consists of a coaptation chamber and a light-activated polymer for securing to the nerve. In this study, we compare the system's biomechanical performance and mechanism of action to microsutures and fibrin repairs.

Methods

The system's fixation force was compared with microsutures and fibrin glue, and evaluated across various nerve diameters through tensile testing. Tension and tissue morphology at the repair site were assessed using finite element modeling and scanning electron microscopy.

Results

The fixation force of the polymer-assisted repair was equivalent to microsutures and superior to fibrin glue. This force increased linearly with nerve diameter, highlighting the correlation between polymer surface contact area and performance. Finite element modeling analysis showed stress concentration at the repair site for microsuture repairs, whereas the polymer-assisted repair dissipated stress along the nerve, away from the repair site. Morphological analysis revealed nerve alignment with no tissue trauma for the polymer-assisted repair, unlike microsutures.

Conclusions

The mechanical performance of the polymer-assisted coaptation system is suitable for peripheral nerve repair. The achieved fixation forces are equivalent to those of microsutures and superior to fibrin glue, minimizing stress concentration at the repair site and avoiding trauma to the severed nerve ends.

A Pressure-Sensitive, Repositionable Bioadhesive for Instant, Atraumatic Surgical Application on Internal Organs

Pressure-sensitive adhesives are widely utilized due to their instant and reversible adhesion to various dry substrates. Though offering intuitive and robust attachment of medical devices on skin, currently available clinical pressure-sensitive adhesives do not attach to internal organs, mainly due to the presence of interfacial water on the tissue surface that acts as a barrier to adhesion. In this work, a pressure-sensitive, repositionable bioadhesive (PSB) that adheres to internal organs by synergistically combining the characteristic viscoelastic properties of pressure-sensitive adhesives and the interfacial behavior of hydrogel bioadhesives, is introduced. Composed of a viscoelastic copolymer, the PSB absorbs interfacial water to enable instant adhesion on wet internal organs, such as the heart and lungs, and removal after use without causing any tissue damage. The PSB's capabilities in diverse on-demand surgical and analytical scenarios including tissue stabilization of soft organs and the integration of bioelectronic devices in rat and porcine models, are demonstrated.

An Injectable Hydrogel with Ultrahigh Burst Pressure and Innate Antibacterial Activity for Emergency Hemostasis and Wound Repair

Uncontrolled bleeding and wound infections following severe trauma pose significant challenges for existing tissue adhesives, primarily due to their weak wet adhesion, slow adhesion formation, cytotoxicity concerns, and lack of antibacterial properties. Herein, an injectable hydrogel (denoted as ES gel) with rapid, robust adhesive sealing and inherent antibacterial activity based on ε-polylysine and a poly(ethylene glycol) derivative is developed. The engineered hydrogel exhibits rapid gelation behavior, high mechanical strength, strong adhesion to various tissues, and can sustain an ultrahigh burst pressure of 450 mmHg. It also presents excellent biocompatibility, biodegradability, antibacterial properties, and on-demand removability. Significantly improved hemostatic efficacy of ES gel compared to fibrin glue is demonstrated using various injury models in rats and rabbits. Remarkably, the adhesive hydrogel can effectively halt lethal non-compressible hemorrhages in visceral organs (liver, spleen, and heart) and femoral artery injury models in fully anticoagulated pigs. Furthermore, the hydrogel outperforms commercial products in sutureless wound closure and repair in the rat liver defect, skin incision, and infected full-thickness skin wound models. Overall, this study highlights the promising clinical applications of ES gel for managing uncontrolled hemorrhage, sutureless wound closure, and infected wound repair.

Tissue-adhesive, stretchable and compressible physical double-crosslinked microgel-integrated hydrogels for dynamic wound care

Integrated wound care through sequentially promoting hemostasis, sealing, and healing holds great promise in clinical practice. However, it remains challenging for regular bioadhesives to achieve integrated care of dynamic wounds due to the difficulties in adapting to dynamic mechanical and wet wound environments. Herein, we reported a type of dehydrated, physical double crosslinked microgels (DPDMs) which were capable of in situ forming highly stretchable, compressible and tissue-adhesive hydrogels for integrated care of dynamic wounds. The DPDMs were designed by the rational integration of the reversible crosslinks and double crosslinks into micronized gels. The reversible physical crosslinks enabled the DPDMs to integrate together, and the double crosslinked characteristics further strengthen the formed macroscopical networks (DPDM-Gels). We demonstrated that the DPDM-Gels simultaneously possess outstanding tensile (∼940 kJ/m3) and compressive (∼270 kJ/m3) toughness, commercial bioadhesives-comparable tissue-adhesive strength, together with stable performance under hundreds of deformations. In vivo results further revealed that the DPDM-Gels could effectively stop bleeding in various bleeding models, even in an actual dynamic environment, and enable the integrated care of dynamic skin wounds. On the basis of the remarkable mechanical and appropriate adhesive properties, together with impressive integrated care capacities, the DPDM-Gels may provide a new approach for the smart care of dynamic wounds. STATEMENT OF SIGNIFICANCE: Integrated care of dynamic wounds holds great significance in clinical practice. However, the dynamic and wet wound environments pose great challenges for existing hydrogels to achieve it. This work developed robust adhesive hydrogels for integrated care of dynamic wounds by designing dehydrated, physical double crosslinked microgels (DPDMs). The reversible and double crosslinks enabled DPDMs to integrate into macroscopic hydrogels with high mechanical properties, appropriate adhesive strength and stable performance under hundreds of external deformations. Upon application at the injury site, DPDM-Gels efficiently stopped bleeding, even in an actual dynamic environment and showed effectiveness in integrated care of dynamic wounds. With the fascinating properties, DPDMs may become an effective tool for smart wound care.

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.

Triggerable Patches for Medical Applications

Medical patches have garnered increasing attention in recent decades for several diagnostic and therapeutic applications. Advancements in material science, manufacturing technologies, and bioengineering have significantly widened their functionalities, rendering them highly versatile platforms for wearable and implantable applications. Of particular interest are triggerable patches designed for drug delivery and tissue regeneration purposes, whose action can be controlled by an external signal. Stimuli-responsive patches are particularly appealing as they may enable a high level of temporal and spatial control over the therapy, allowing high therapeutic precision and the possibility to adjust the treatment according to specific clinical and personal needs. This review aims to provide a comprehensive overview of the existing extensive literature on triggerable patches, emphasizing their potential for diverse applications and highlighting the strengths and weaknesses of different triggering stimuli. Additionally, the current open challenges related to the design and use of efficient triggerable patches, such as tuning their mechanical and adhesive properties, ensuring an acceptable trade-off between smartness and biocompatibility, endowing them with portability and autonomy, accurately controlling their responsiveness to the triggering stimulus and maximizing their therapeutic efficacy, are reviewed.

An injectable and coagulation-independent Tetra-PEG hydrogel bioadhesive for post-extraction hemostasis and alveolar bone regeneration

Effective control of post-extraction hemorrhage and alveolar bone resorption is critical for successful extraction socket treatment, which remains an unmet clinical challenge. Herein, an injectable Tetra-PEG hydrogel that possesses rapid gelation, firm tissue adhesion, high mechanical strength, suitable degradability, and excellent biocompatibility is developed as a sutureless and coagulation-independent bioadhesive for the management of extraction sockets. Our results demonstrate that the rapid and robust adhesive sealing of the extraction socket by the Tetra-PEG hydrogel can provide reliable protection for the underlying wound and stabilize blood clots to facilitate tissue healing. In vivo experiments using an anticoagulated rat tooth extraction model show that the hydrogel significantly outperformed clinically used cotton and gelatin sponge in hemostatic efficacy, wound closure, alveolar ridge preservation, and in situ alveolar bone regeneration. Histomorphological evaluations reveal the mechanisms for accelerated bone repair through suppressed long-term inflammation, elevated collagen deposition, higher osteoblast activity, and enhanced angiogenesis. Together, our study highlights the clinical potential of the developed injectable Tetra-PEG hydrogel for treating anticoagulant-related post-extraction hemorrhage and improving socket healing.

Silk Fibroin and Its Nanocomposites for Wound Care: A Comprehensive Review

For most individuals, wound healing is a highly organized, straightforward process, wherein the body transitions through different phases in a timely manner. However, there are instances where external intervention becomes necessary to support and facilitate different phases of the body's innate healing mechanism. Furthermore, in developing countries, the cost of the intervention significantly impacts access to treatment options as affordability becomes a determining factor. This is particularly true in cases of long-term wound treatment and management, such as chronic wounds and infections. Silk fibroin (SF) and its nanocomposites have emerged as promising biomaterials with potent wound-healing activity. Driven by this motivation, this Review presents a critical overview of the recent advancements in different aspects of wound care using SF and SF-based nanocomposites. In this context, we explore various formats of hemostats and assess their suitability for different bleeding situations. The subsequent sections discuss the primary causes of nonhealing wounds, i.e., prolonged inflammation and infections. Herein, different treatment strategies to achieve immunomodulatory and antibacterial properties in a wound dressing were reviewed. Despite exhibiting excellent pro-healing properties, few silk-based products reach the market. This Review concludes by highlighting the bottlenecks in translating silk-based products into the market and the prospects for the future.

Kuragel: A biomimetic hydrogel scaffold designed to promote corneal regeneration

Cornea-related injuries are the most common cause of blindness worldwide. Transplantation remains the primary approach for addressing corneal blindness, though the demand for donor corneas outmatches the supply by millions. Tissue adhesives employed to seal corneal wounds have shown inefficient healing and incomplete vision restoration. We have developed a biodegradable hydrogel - Kuragel, with the ability to promote corneal regeneration. Functionalized gelatin and hyaluronic acid form photo-crosslinkable hydrogel with transparency and compressive modulus similar to healthy human cornea. Kuragel composition was tuned to achieve sufficient adhesive strength for sutureless integration to host tissue, with minimal swelling post-administration. Studies in the New Zealand rabbit mechanical injury model affecting corneal epithelium and stroma demonstrate that Kuragel efficiently promotes re-epithelialization within 1 month of administration, while stroma and sub-basal nerve plexus regenerate within 3 months. We propose Kuragel as a regenerative treatment for patients suffering from corneal defects including thinning, by restoration of transparency and thickness.

Enhanced ROS scavenging and tissue adhesive abilities in injectable hydrogels by protein modification with oligoethyleneimine

Postsurgical treatment comprehensively benefits from the application of tissue-adhesive injectable hydrogels, which reduce postoperative complications by promoting wound closure and tissue regeneration. Although various hydrogels have been employed as clinical tissue adhesives, many exhibit deficiencies in adhesive strength under wet conditions or in immunomodulatory functions. Herein, we report the development of reactive oxygen species (ROS) scavenging and tissue-adhesive injectable hydrogels composed of polyamine-modified gelatin crosslinked with the 4-arm poly (ethylene glycol) crosslinker. Polyamine-modified gelatin was particularly potent in suppressing the secretion of proinflammatory cytokines from stimulated primary macrophages. This effect is attributed to its ability to scavenge ROS and inhibit the nuclear translocation of nuclear factor kappa-B. Polyamine-modified gelatin-based hydrogels exhibited ROS scavenging abilities and enhanced tissue adhesive strength on collagen casing. Notably, the hydrogel demonstrated exceptional tissue adhesive properties in a wet environment, as evidenced by its performance using porcine small intestine tissue. This approach holds significant promise for designing immunomodulatory hydrogels with superior tissue adhesion strength compared to conventional medical materials, thereby contributing to advancements in minimally invasive surgical techniques.

Naturally Derived Injectable Dual-Cross-Linked Adhesive Hydrogel for Acute Hemorrhage Control and Wound Healing

Developing biocompatible injectable hydrogels with high mechanical strength and rapid strong tissue adhesion for hemostatic sealing of uncontrolled bleeding remains a prevailing challenge. Herein, we engineer an injectable and photo-cross-linkable hydrogel based on naturally derived gelatin methacrylate (GelMA) and N-hydroxysuccinimide-modified poly(γ-glutamic acid) (γPGA-NHS). The chemically dual-cross-linked hydrogel rapidly forms after UV light irradiation and covalently bonds to the underlying tissue to provide robust adhesion. We demonstrate a significantly improved hemostatic efficacy of the hydrogel using various injury models in rats compared to the commercially available fibrin glue. Notably, the hydrogel can achieve hemostasis in porcine liver and spleen incision, and femoral artery puncture models. Moreover, the hydrogel is used for sutureless repair of the liver defect in a rat model with a significantly suppressed inflammatory response, enhanced angiogenesis, and superior healing efficacy compared to fibrin glue. Together, this study offers a promising bioadhesive for treating severe bleeding and facilitating wound repair.

Advances in Polysaccharides for Cartilage Tissue Engineering Repair: A Review

Cartilage repair has been a significant challenge in orthopedics that has not yet been fully resolved. Due to the absence of blood vessels and the almost cell-free nature of mature cartilage tissue, the limited ability to repair cartilage has resulted in significant socioeconomic pressures. Polysaccharide materials have recently been widely used for cartilage tissue repair due to their excellent cell loading, biocompatibility, and chemical modifiability. They also provide a suitable microenvironment for cartilage repair and regeneration. In this Review, we summarize the techniques used clinically for cartilage repair, focusing on polysaccharides, polysaccharides for cartilage repair, and the differences between these and other materials. In addition, we summarize the techniques of tissue engineering strategies for cartilage repair and provide an outlook on developing next-generation cartilage repair and regeneration materials from polysaccharides. This Review will provide theoretical guidance for developing polysaccharide-based cartilage repair and regeneration materials with clinical applications for cartilage tissue repair and regeneration.

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.

Co-release of nitric oxide and L-arginine from poly (β-amino ester)-based adhesive reprogram macrophages for accelerated wound healing and angiogenesis in vitro and in vivo

Recently, insufficient angiogenesis and prolonged inflammation are crucial challenges of chronic skin wound healing. The sustained release of L-Arginine (L-Arg) and nitric oxide (NO) production can control immune responses, improve angiogenesis, enhance re-epithelialization, and accelerate wound healing. Here, we aim to improve wound healing via the controlled release of NO and L-Arg from poly (β-amino ester) (PβAE). In this regard, PβAE is functionalized with methacrylate poly-L-Arg (PAMA), and the role of PAMA content (50, 66, and 75 wt%) on the adhesive properties, L-Arg, and NO release, as well as collagen deposition, inflammatory responses, and angiogenesis, is investigated in vitro and in vivo. Results show that the PAMA/ PβAE could provide suitable adhesive strength (~25 kPa) for wound healing application. In addition, increasing the PAMA content from 50 to 75 wt% results in an increased release of L-Arg (approximately 1.4-1.7 times) and enhanced NO production (approximately 2 times), promoting skin cell proliferation and migration. The in vitro studies also show that compared to PβAE hydrogel, incorporation of 66 wt% PAMA (PAMA 66 sample) reveals superior collagen I synthesis (~ 3-4 times) of fibroblasts, controlled pro-inflammatory and improved anti-inflammatory cytokines secretion of macrophages, and accelerated angiogenesis (~1.5-2 times). In vivo studies in a rat model with a full-thickness skin defect also demonstrate the PAMA66 sample could accelerate wound healing (~98 %) and angiogenesis, compared to control (untreated wound) and Tegaderm™ commercial wound dressing. In summary, the engineered multifunctional PAMA functionalized PβAE hydrogel with desired NO and L-Arg release, and adhesive properties can potentially reprogram macrophages and accelerate skin healing for chronic wound healing.

What else should hemostatic materials do beyond hemostasis: A review

Massive blood loss due to injury is the leading cause of prehospital deaths in disasters and emergencies. Hemostatic materials are used to realize rapid hemostasis and protect patients from death. Researchers have designed and developed a variety of hemostatic materials. However, in addition to their hemostatic effect, hemostatic materials must be endowed with additional functions to meet the practical application requirements in different scenarios. Here, strategies for modifications of hemostatic materials for use in different application scenarios are listed: effective positioning at the site of deep and narrow wounds to stop bleeding, resistance to high blood pressure and wound movement to maintain wound formation, rapid and easy removal from the wound without affecting further treatment after hemostasis is completed, and continued function when retained in the wound as a dressing (such as antibacterial, antiadhesion, tissue repair, etc.). The problems encountered in the practical use of hemostatic materials and the strategies and progress of researchers will be further discussed in this review. We hope to provide valuable references for the design of more comprehensive and practical hemostatic materials.

A tough bioadhesive hydrogel supports sutureless sealing of the dural membrane in porcine and ex vivo human tissue

Complete sequestration of central nervous system tissue and cerebrospinal fluid by the dural membrane is fundamental to maintaining homeostasis and proper organ function, making reconstruction of this layer an essential step during neurosurgery. Primary closure of the dura by suture repair is the current standard, despite facing technical, microenvironmental, and anatomic challenges. Here, we apply a mechanically tough hydrogel paired with a bioadhesive for intraoperative sealing of the dural membrane in rodent, porcine, and human central nervous system tissue. Tensile testing demonstrated that this dural tough adhesive (DTA) exhibited greater toughness with higher maximum stress and stretch compared with commercial sealants in aqueous environments. To evaluate the performance of DTA in the range of intracranial pressure typical of healthy and disease states, ex vivo burst pressure testing was conducted until failure after DTA or commercial sealant application on ex vivo porcine dura with a punch biopsy injury. In contrast to commercial sealants, DTA remained adhered to the porcine dura through increasing pressure up to 300 millimeters of mercury and achieved a greater maximum burst pressure. Feasibility of DTA to repair cerebrospinal fluid leak in a simulated surgical context was evaluated in postmortem human dural tissue. DTA supported effective sutureless repair of the porcine thecal sac in vivo. Biocompatibility and adhesion of DTA was maintained for up to 4 weeks in rodents after implantation. The findings suggest the potential of DTA to augment or perhaps even supplant suture repair and warrant further exploration.

Stimuli-Responsive Hydrogel Adhesives for Wound Closure and Tissue Regeneration

Sutures and staplers, as gold standards for clinical wound closure, usually cause secondary tissue injury and require professional technicians and equipment. The noninvasive hydrogel adhesives are used in various biomedical applications, such as wound closure, tissue sealing, and tissue regeneration, due to their remarkable properties. Recently-developed hydrogel adhesives, especially stimuli-responsive hydrogels, have shown great potential owing to their advantages in regulating their performance and functions according to the wound situations or external conditions, thus allowing the wounds to heal gradually. However, comprehensive summary on stimuli-responsive hydrogels as tissue adhesives is rarely reported to date. This review focuses on the advances in the design of various stimuli-responsive hydrogel adhesives over the past decade, including the systems responsive to pH, temperature, photo, and enzymes. Their potential biomedical applications, such as skin closure, cardiovascular and liver hemostasis, and gastrointestinal sealing, are emphasized. Meanwhile, the challenges and future development of stimuli-responsive hydrogel adhesives are discussed. This review aims to provide meaningful insights for the further design of next-generation of hydrogel adhesives for wound closure and tissue regeneration.

A 3D printable tissue adhesive

Tissue adhesives are promising alternatives to sutures and staples for joining tissues, sealing defects, and immobilizing devices. However, existing adhesives mostly take the forms of glues or hydrogels, which offer limited versatility. We report a direct-ink-write 3D printable tissue adhesive which can be used to fabricate bioadhesive patches and devices with programmable architectures, unlocking new potential for application-specific designs. The adhesive is conformable and stretchable, achieves robust adhesion with wet tissues within seconds, and exhibits favorable biocompatibility. In vivo rat trachea and colon defect models demonstrate the fluid-tight tissue sealing capability of the printed patches, which maintained adhesion over 4 weeks. Moreover, incorporation of a blood-repelling hydrophobic matrix enables the printed patches to seal actively bleeding tissues. Beyond wound closure, the 3D printable adhesive has broad applicability across various tissue-interfacing devices, highlighted through representative proof-of-concept designs. Together, this platform offers a promising strategy toward developing advanced tissue adhesive technologies.

Cellulose based composite sponges with oriented porous structure and superabsorptive capacity for quick hemostasis

Excessive bleeding is the leading cause of death in accidents and operations. Ca2+ crosslinked carboxyl nanocellulose (CN)/montmorillonite (MMT) composite (CaCNMMT) sponges were prepared by uniform mixing and directional freeze-drying methods which was inspired by the coordination mechanism of blood clot formation and coagulation cascade activation in natural hemostasis process. Carboxyl nanocellulose (CaCN) sponge has instantaneous water absorption capacity, and CaCNMMT sponges could further activate clotting factors. Therefore, CaCNMMT sponges achieved quick hemostasis by efficient concentrating blood, inducing hemocyte aggregation and stimulating coagulation cascade activation based on the synergistic effects of CN and MMT. Blood clotting index of CaCNMMT (15.90 ± 0.52 %) was significantly lower than CaCN (59.3 ± 1.43 %), and APTT time (22 ± 2 s) was almost equivalent to MMT (20 ± 2 s). CaCNMMT sponge showed good quick hemostatic effect on massive hemorrhage in both tail-breaking and liver injury model which provided a new strategy for the application of MMT in hemostatic and trauma treatment fields.

Bioadhesive Technology Platforms

Bioadhesives have emerged as transformative and versatile tools in healthcare, offering the ability to attach tissues with ease and minimal damage. These materials present numerous opportunities for tissue repair and biomedical device integration, creating a broad landscape of applications that have captivated clinical and scientific interest alike. However, fully unlocking their potential requires multifaceted design strategies involving optimal adhesion, suitable biological interactions, and efficient signal communication. In this Review, we delve into these pivotal aspects of bioadhesive design, highlight the latest advances in their biomedical applications, and identify potential opportunities that lie ahead for bioadhesives as multifunctional technology platforms.

In situ generated hemostatic adhesives: From mechanisms of action to recent advances and applications

Conventional surgical closure techniques, such as sutures, clips, or skin closure strips, may not always provide optimal wound closure and may require invasive procedures, which can result in potential post-surgical complications. As result, there is a growing demand for innovative solutions to achieve superior wound closure and improve patient outcomes. To overcome the abovementioned issues, in situ generated hemostatic adhesives/sealants have emerged as a promising alternative, offering a targeted, controllable, and minimally invasive procedure for a wide variety of medical applications. The aim of this review is to provide a comprehensive overview of the mechanisms of action and recent advances of in situ generated hemostatic adhesives, particularly protein-based, thermoresponsive, bioinspired, and photocrosslinkable formulations, as well as the design challenges that must be addressed. Overall, this review aims to enhance a comprehensive understanding of the latest advancements of in situ generated hemostatic adhesives and their mechanisms of action, with the objective of promoting further research in this field.

A Nature-Inspired Versatile Bio-Adhesive

The application of most hydrogel bio-adhesives is greatly limited due to their high swelling, low underwater adhesion, and single function. Herein, a spatial multi-level physical-chemical and bio-inspired in-situ bonding strategy is proposed, to develop a multifunctional hydrogel bio-glue using polyglutamic acid (PGA), tyramine hydrochloride (TYR), and tannic acid (TA) as precursors and 4-(4,6-dimethoxytriazine-2-yl) -4-methylmorpholine hydrochloride(DMTMM) as condensation agent, which is used for tissue adhesion, hemostasis and repair. By introducing TYR and TA into the PGA chain, it is demonstrated that not only can the strong adhesion of bio-glue to the surface of various fresh tissues and wet materials be realized through the synergistic effect of spatial multi-level physical and chemical bonding, but also this glue can be endowed with the functions of anti-oxidation and hemostasis. The excellent performance of such bio-glue in the repair of the wound, liver, and cartilage is achieved, showing a great potential in clinical application for such bio-glue. This study will open up a brand-new avenue for the development of multifunctional hydrogel biological adhesive.

Diatom-Inspired Bionic Hydrophilic Polysaccharide Adhesive for Rapid Sealing Hemostasis

Diatoms are typical marine biofouling organisms that secrete extracellular polymers (EPS) to achieve strong underwater adhesion. Here, we report a diatom-inspired bionic hydrophilic polysaccharide adhesive composed of diatom biosilica (DB) and bletilla striata polysaccharide (BSP) for rapid sealing hemostasis. The hierarchical porous structure of DB with rich surface silanol groups provides a strong anchored interface effect for BSP, which can significantly enhance cross-linking density and interaction strength of the hydrophilic macromolecular network. BSP/DB adhesive offers 6 times greater mechanical strength and viscosity over BSP under different temperature conditions. The aggregation effect of DBs interface for BSP avoided the washout of BSP/DB adhesive during application in a wet environment before cross-linking occurs. This strengthened the adhesion ability of BSP/DB adhesive to biological tissue that brought out complete sealing hemostasis without blood loss in a rat liver injury model. The dry BSP/DB prepared by lyophilization inherited excellent clotting ability of BSP/DB adhesive, which could realize rapidly the cruor of anticoagulant whole blood within 1 min. The results of animal studies confirmed that dry BSP/DB exhibited superior hemostatic performance over silicate-based inorganic Quikclot, in terms of hemostatic rate, blood loss, dosage, and multiscroll wound closure.

Gelatin-modified 3D printed PGS elastic hierarchical porous scaffold for cartilage regeneration

Regenerative cartilage replacements are increasingly required in clinical settings for various defect repairs, including bronchial cartilage deficiency, articular cartilage injury, and microtia reconstruction. Poly (glycerol sebacate) (PGS) is a widely used bioelastomer that has been developed for various regenerative medicine applications because of its excellent elasticity, biodegradability, and biocompatibility. However, because of inadequate active groups, strong hydrophobicity, and limited ink extrusion accuracy, 3D printed PGS scaffolds may cause insufficient bioactivity, inefficient cell inoculation, and inconsistent cellular composition, which seriously hinders its further cartilage regenerative application. Here, we combined 3D printed PGS frameworks with an encapsulated gelatin hydrogel to fabricate a PGS@Gel composite scaffold. PGS@Gel scaffolds have a controllable porous microstructure, with suitable pore sizes and enhanced hydrophilia, which could significantly promote the cells' penetration and adhesion for efficient chondrocyte inoculation. Furthermore, the outstanding elasticity and fatigue durability of the PGS framework enabled the regenerated cartilage built by the PGS@Gel scaffolds to resist the dynamic in vivo environment and maintain its original morphology. Importantly, PGS@Gel scaffolds increased the rate of cartilage regeneration concurrent with scaffold degradation. The scaffold was gradually degraded and integrated to form uniform, dense, and mature regenerated cartilage tissue with little scaffold residue.

Polymer nanomaterials for use as adjuvant surgical tools

Materials employed in the treatment of conditions encountered in surgical and clinical practice frequently face barriers in translation to application. Shortcomings can be generalized through their reduced mechanical stability, difficulty in handling, and inability to conform or adhere to complex tissue surfaces. To overcome an amalgam of challenges, research has sought the utilization of polymer-derived nanomaterials deposited in various fashions and formulations to improve the application and outcomes of surgical and clinical interventions. Clinically prevalent applications include topical wound dressings, tissue adhesives, surgical sealants, hemostats, and adhesion barriers, all of which have displayed the potential to act as superior alternatives to current materials used in surgical procedures. In this review, emphasis will be placed not only on applications, but also on various design strategies employed in fabrication. This review is designed to provide a broad and thought-provoking understanding of nanomaterials as adjuvant tools for the assisted treatment of pathologies prevalent in surgery. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanoscale Tools and Techniques in Surgery.

Injectable and photocurable macromonomers synthesized using a heterometallic magnesium-titanium metal-organic catalyst for elastomeric polymer networks

Injectable and in situ photocurable biomaterials are receiving a lot of attention due to their ease of application via syringe or dedicated applicator and ability to be used in laparoscopic and robotic minimally invasive procedures. The aim of this work was to synthesize photocurable ester-urethane macromonomers using a heterometallic magnesium-titanium catalyst, magnesium-titanium(iv) butoxide for elastomeric polymer networks. The progress of the two-step synthesis of macromonomers was monitored using infrared spectroscopy. The chemical structure and molecular weight of the obtained macromonomers were characterized using nuclear magnetic resonance spectroscopy and gel permeation chromatography. The dynamic viscosity of the obtained macromonomers was evaluated by a rheometer. Next, the photocuring process was studied under both air and argon atmospheres. Both the thermal and dynamic mechanical thermal properties of the photocured soft and elastomeric networks were investigated. Finally, in vitro cytotoxicity screening of polymer networks based on ISO10993-5 revealed high cell viability (over 77%) regardless of curing atmosphere. Overall, our results indicate that this heterometallic magnesium-titanium butoxide catalyst can be an attractive alternative to commonly used homometallic catalysts for the synthesis of injectable and photocurable materials for medical applications.

An Adhesive/Anti-Adhesive Janus Tissue Patch for Efficient Closure of Bleeding Tissue with Inhibited Postoperative Adhesion

Most of the current bioadhesives cannot perform well on bleeding tissues while postoperative adhesion is a general but serious clinical issue. Here, a three-layer biodegradable Janus tissue patch (J-TP) that is able to simultaneously enable efficient closure of bleeding wounds with significantly promoted clotting ability and suppressed postoperative adhesion of tissues is reported. A dry adhesive hydrogel bottom layer of the J-TP can form rapid (within 15 s) and strong (tensile strength up to 98 kPa) adhesion to bleeding/wet tissues with high bursting pressure (about 312.5 mmHg on a sealed porcine skin) through hydrogen binding and covalent conjugation between the carboxyl & N-hydroxy succinimide (NHS) groups of hydrogel and the primary amine groups of tissues, while the phosphonic motifs can significantly reduce blood loss (by 81% on a rat bleeding liver model) of bleeding wounds. A thin polylactic acid (PLA) middle layer can improve the tensile strength (by 132%) of the J-TP in wet conditions while the grafted zwitterionic polymers can effectively prevent postoperative tissue adhesion and inflammatory reaction. This J-TP may be a promising tissue patch to assist the clinical treatment of injured bleeding tissues with inhibited postoperative adhesion.

Tissue Glue-Based Sealing Patch for the in vivo Prevention of Iatrogenic Prelabor Preterm Rupture of Fetal Membranes

INTRODUCTION

One of the main concerns for all fetal surgeries is the risk of preterm delivery due to the preterm prelabor rupture of the fetal membranes (iPPROM). Clinical approaches to seal fetal membrane (FM) defects are missing due to the lack of appropriate strategies to apply sealing biomaterials at the defect site.

METHODS

Here, we test the performance of a previously developed strategy to seal FM defects with cyanoacrylate-based sealing patches in an ovine model up to 24 days after application.

RESULTS

Patches sealed tightly the fetoscopy-induced FM defects and remained firmly attached to the defect over 10 days. At 10 days after treatment, 100% (13/13) of the patches were attached to the FMs, and 24 days after treatment 25% (1/4) of the patches placed in CO2 insufflation, and 33% (1/3) in NaCl infusion remained. However, all successfully applied patches (20/24) led to a watertight sealing at 10 or 24 days after treatment. Histological analysis indicated that cyanoacrylates induced a moderate immune response and disrupted the FM epithelium.

CONCLUSION

Together, these data show the feasibility of minimally invasive sealing of FM defects by locally gathering tissue adhesive. Further development to combine this technology with refined tissue glues or healing-inducing materials holds great promise for future clinical translation.

Reversible adhesives with controlled wrinkling patterns for programmable integration and discharging

Switchable and minimally invasive tissue adhesives have great potential for medical applications. However, on-demand adherence to and detachment from tissue surfaces remain difficult. We fabricated a switchable hydrogel film adhesive by designing pattern-tunable wrinkles to control adhesion. When adhered to a substrate, the compressive stress generated from the bilayer system leads to self-similar wrinkling patterns at short and long wavelengths, regulating the interfacial adhesion. To verify the concept and explore its application, we established a random skin flap model, which is a crucial strategy for repairing severe or large-scale wounds. Our hydrogel adhesive provides sufficient adhesion for tissue sealing and promotes neovascularization at the first stage, and then gradually detaches from the tissue while a dynamic wrinkling pattern transition happens. The gel film can be progressively ejected out from the side margins after host-guest integration. Our findings provide insights into tunable bioadhesion by manipulating the wrinkling pattern transition.

Adhesive cryogel particles for bridging confined and irregular tissue defects

BACKGROUND

Reconstruction of damaged tissues requires both surface hemostasis and tissue bridging. Tissues with damage resulting from physical trauma or surgical treatments may have arbitrary surface topographies, making tissue bridging challenging.

METHODS

This study proposes a tissue adhesive in the form of adhesive cryogel particles (ACPs) made from chitosan, acrylic acid, 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The adhesion performance was examined by the 180-degree peel test to a collection of tissues including porcine heart, intestine, liver, muscle, and stomach. Cytotoxicity of ACPs was evaluated by cell proliferation of human normal liver cells (LO2) and human intestinal epithelial cells (Caco-2). The degree of inflammation and biodegradability were examined in dorsal subcutaneous rat models. The ability of ACPs to bridge irregular tissue defects was assessed using porcine heart, liver, and kidney as the ex vivo models. Furthermore, a model of repairing liver rupture in rats and an intestinal anastomosis in rabbits were established to verify the effectiveness, biocompatibility, and applicability in clinical surgery.

RESULTS

ACPs are applicable to confined and irregular tissue defects, such as deep herringbone grooves in the parenchyma organs and annular sections in the cavernous organs. ACPs formed tough adhesion between tissues [(670.9 ± 50.1) J/m² for the heart, (607.6 ± 30.0) J/m² for the intestine, (473.7 ± 37.0) J/m² for the liver, (186.1 ± 13.3) J/m² for muscle, and (579.3 ± 32.3) J/m² for the stomach]. ACPs showed considerable cytocompatibility in vitro study, with a high level of cell viability for 3 d [(98.8 ± 1.2) % for LO2 and (98.3 ± 1.6) % for Caco-2]. It has comparable inflammation repair in a ruptured rat liver (P = 0.58 compared with suture closure), the same with intestinal anastomosis in rabbits (P = 0.40 compared with suture anastomosis). Additionally, ACPs-based intestinal anastomosis (less than 30 s) was remarkably faster than the conventional suturing process (more than 10 min). When ACPs degrade after surgery, the tissues heal across the adhesion interface.

CONCLUSIONS

ACPs are promising as the adhesive for clinical operations and battlefield rescue, with the capability to bridge irregular tissue defects rapidly.

Preliminary Application Research of 3D Bioprinting in Craniofacial Reconstruction

INTRODUCTION

In recent years, 3-dimensional (3D) printing has been widely used in regenerative medicine research and other fields because of its ability to customize macroscopic morphology and precisely control microstructure. Polymer scaffolds are 1 of the commonly used 3D bioprinting materials for defect repair and have recently been a research focus. Our article explored the bone-formation accelerating effect of 3D-printed porous scaffold Poly(glycerol sebacate) [PGS] in the critical bone defect of an enhancing rabbit mandibular model. Also, we overview and summarize the classification of 3D bioprinting materials and prospects for their various application scenarios in craniofacial reconstruction surgery.

MATERIALS AND METHODS

A PGS elastomer scaffold was prepared by polymerizing equimolar amounts of sebacic acid and glycerol using a biological 3D printer. Six male New Zealand white rabbits were prepared (3 for the control group and 3 for the PGS group), each weighing 3 kg. Osteotomy was performed at the anterior edge of the ascending ramus of the mandible with a bone saw to open the 8 mm defect. Defects of the control group were empty, and defects of the PGS group were put into 8 mm-wide PGS elastomer scaffolds. The rabbits were euthanized 6 weeks after the operation, and the postoperative mandibles were collected. Information (presence or absence of pus from infection, nonunion, degree of macroscopic bone healing) was recorded, and the skeletal tissue was fixed in a paraformaldehyde solution.

RESULTS

The mandible on the enhanced side was significantly longer than that on the opposite side, and the contralateral incisor was hyperplasia. The mandibles of rabbits in each group healed well, and there was no obvious local infection and purulence. The gross specimen appearance showed that both ends of the defect were connected. When comparing the reconstructed mandibles of the two groups, it is apparent that the width and thickness of the new bone in the PGS group were significantly better than that in the control group.

CONCLUSIONS

This article verifies the effect of 3D polypore PGS scaffolds in animal craniomaxillofacial bone defects and introduces various application scenarios of 3D printing materials in craniomaxillofacial reconstruction surgery. There are quite good application prospects for 3D bioprinting in animal experiments and even clinical treatment of craniofacial defects.

A Super Tough, Rapidly Biodegradable, Ultrafast Hemostatic Bioglue

Death happening due to massive hemorrhage has been involved in military conflicts, traffic accidents, and surgical injuries of various human disasters. Achieving rapid and effective hemostasis to save lives is crucial in urgent massive bleeding situations. Herein, a covalent cross-linked AG-PEG glue based on extracellular matrix-like amino-gelatin (AG) and PEG derivatives is developed. The AG-PEG glue gelatinizes fast and exhibits firm and indiscriminate close adhesion with various moist tissues upon being dosed. The formed glue establishes an adhesive and robust barrier to seal the arterial, hepatic, and cardiac hemorrhagic wounds, enabling it to withstand up to 380 mmHg blood pressure in comparison with normal systolic blood pressure of 60-180 mmHg. Remarkably, massive bleeding from a pig cardiac penetrating hole with 6 mm diameter is effectively stopped using the glue within 60 s. Postoperative indexes of the treated pig gradually recover and the cardiac wounds regrow significantly at 14 days. Possessing on-demand solubility, self-gelling, and rapid degradability, the AG-PEG glue may provide a fascinating stop-bleeding approach for clinical hemostasis and emergency rescue.

Superwetting Injectable Hydrogel with Ultrastrong and Fast Tissue Adhesion for Minimally Invasive Hemostasis

Injectable hydrogels have recently emerged as alternatives to sutures for various clinical indications. However, existing injectable hydrogels are unsuitable for hemostasis in minimally invasive surgery because of their weak interfacial adhesion and complex/prolonged processing. Herein, a superwetting injectable hydrogel composed of oppositely charged polysaccharides is developed. The spontaneous spreading of the injectable hydrogel on the surfaces achieves complete wetting and forms tight interfacial contact by absorbing the interfacial water. The superwetting ability and subsequent covalent crosslinking perform fast and ultrastrong wet adhesion (140 kPa) on the tissue surface. Ex vivo porcine and in vivo rat models show that the hydrogel successfully leads to the aggregation of erythrocytes for targeted hemostasis (in less than 12 s) without requiring external adjuncts, and no postsurgical adhesions to the peripheral tissues. This further demonstrates that hydrogel can act as an effective hemostasis agent in laparoscopic surgery in a rabbit model. Overall, the strong wet adhesion, antibacterial properties, and easy operability make this injectable hydrogel a promising candidate for hemostasis applications, as it can successfully combine clinical efficacy and transformation opportunities for minimally invasive surgery.

High Performance Marine and Terrestrial Bioadhesives and the Biomedical Applications They Have Inspired

This study has reviewed the naturally occurring bioadhesives produced in marine and freshwater aqueous environments and in the mucinous exudates of some terrestrial animals which have remarkable properties providing adhesion under difficult environmental conditions. These bioadhesives have inspired the development of medical bioadhesives with impressive properties that provide an effective alternative to suturing surgical wounds improving closure and healing of wounds in technically demanding tissues such as the heart, lung and soft tissues like the brain and intestinal mucosa. The Gecko has developed a dry-adhesive system of exceptional performance and has inspired the development of new generation re-usable tapes applicable to many medical procedures. The silk of spider webs has been equally inspiring to structural engineers and materials scientists and has revealed innovative properties which have led to new generation technologies in photonics, phononics and micro-electronics in the development of wearable biosensors. Man made products designed to emulate the performance of these natural bioadhesive molecules are improving wound closure and healing of problematic lesions such as diabetic foot ulcers which are notoriously painful and have also found application in many other areas in biomedicine. Armed with information on the mechanistic properties of these impressive biomolecules major advances are expected in biomedicine, micro-electronics, photonics, materials science, artificial intelligence and robotics technology.

A sandwiched patch toward leakage-free and anti-postoperative tissue adhesion sealing of intestinal injuries

Ideal repair of intestinal injury requires a combination of leakage-free sealing and postoperative antiadhesion. However, neither conventional hand-sewn closures nor existing bioglues/patches can achieve such a combination. To this end, we develop a sandwiched patch composed of an inner adhesive and an outer antiadhesive layer that are topologically linked together through a reinforced interlayer. The inner adhesive layer tightly and instantly adheres to the wound sites via -NHS chemistry; the outer antiadhesive layer can inhibit cell and protein fouling based on the zwitterion structure; and the interlayer enhances the bulk resilience of the patch under excessive deformation. This complementary trilayer patch (TLP) possesses a unique combination of instant wet adhesion, high mechanical strength, and biological inertness. Both rat and pig models demonstrate that the sandwiched TLP can effectively seal intestinal injuries and inhibit undesired postoperative tissue adhesion. The study provides valuable insight into the design of multifunctional bioadhesives to enhance the treatment efficacy of intestinal injuries.

Natural Small Biological Molecule Based Supramolecular Bioadhesives with Innate Photothermal Antibacterial Capability for Nonpressing Hemostasis and Effective Wound Healing

Bioadhesives with immediate wound closure, efficient hemostasis, and antibacterial properties that can well integrate with tissue are urgently needed in wound management. Natural small biological molecule based bioadhesives hold great promise for manipulating wound healing by taking advantage of integrated functionalities, synthetic simplification, and accuracy, cost efficiency and biosafety. Herein, a natural small biological molecule based bioadhesive, composed of natural small biological molecules (α-lipoic acid and tannic acid) and a small amount of ferric chloride, was prepared via an extremely simple and green route for wound management. In this system, covalent and noncovalent interactions between each component resulted in the self-healing supramolecular bioadhesive. It possessed appropriate wet-tissue adhesion, efficient nonpressing hemostasis and free radical scavenging abilities. More importantly, the interaction between tannic acid and Fe³⁺ endowed the bioadhesive with innate and steady photothermal activity, which showed excellent photothermal bactericidal activity to both E. coli and S. aureus. The bioadhesive promoted wound healing for linear and circular wounds in vivo, especially for infectious wounds under near-infrared (NIR) irradiation. This bioadhesive will have promising value as a safe and effective antimicrobial adhesive for infectious wound management.

Minimally-invasive cardiac surgery: a bibliometric analysis of impact and force to identify key and facilitating advanced training

Background

The number of citations an article receives is a marker of its scientific influence within a particular specialty. This bibliometric analysis intended to recognise the top 100 cited articles in minimally-invasive cardiac surgery, to determine the fundamental subject areas that have borne considerable influence upon clinical practice and academic knowledge whilst also considering bibliometric scope. This is increasingly relevant in a continually advancing specialty and one where minimally-invasive cardiac procedures have the potential for huge benefits to patient outcomes.

Methods

The Web of Science (Clarivate Analytics) data citation index database was searched with the following terms: [Minimal* AND Invasive* AND Card* AND Surg*]. Results were limited to full text English language manuscripts and ranked by citation number. Further analysis of the top 100 cited articles was carried out according to subject, author, publication year, journal, institution and country of origin.

Results

A total of 4716 eligible manuscripts were retrieved. Of the top 100 papers, the median (range) citation number was 101 (51–414). The most cited paper by Lichtenstein et al. (Circulation 114(6):591–596, 2006) published in Circulation with 414 citations focused on transapical transcatheter aortic valve implantation as a viable alternative to aortic valve replacement with cardiopulmonary bypass in selected patients with aortic stenosis. The Annals of Thoracic Surgery published the most papers and received the most citations (n = 35; 3036 citations). The United States of America had the most publications and citations (n = 52; 5303 citations), followed by Germany (n = 27; 2598 citations). Harvard Medical School, Boston, Massachusetts, published the most papers of all institutions. Minimally-invasive cardiac surgery pertaining to valve surgery (n = 42) and coronary artery bypass surgery (n = 30) were the two most frequent topics by a large margin.

Conclusions

This work establishes a comprehensive and informative analysis of the most influential publications in minimally-invasive cardiac surgery and outlines what constitutes a citable article. Undertaking a quantitative evaluation of the top 100 papers aids in recognising the contributions of key authors and institutions as well as guiding future efforts in this field to continually improve the quality of care offered to complex cardiac patients.

Minimally Invasive Bimanual Fetal Surgery—A Review

Background: The aim of this review is to discuss experimental and clinical techniques and interventions of fetal surgery which have been performed minimally invasively by the means of a three-port approach for the fetoscope and instruments for the left and right hand of the surgeon (bimanual minimally invasive fetal surgery). Methods: a print and electronic literature search was performed; the titles and abstracts were screened and included reports were reviewed in a two-step approach. First, reports other than minimally invasive fetal surgery were excluded, then a full text review and analysis of the reported data was performed. Results: 17 reports were included. The heterogeneity of the included reports was high. Although reports on human fetoscopic surgical procedures can be found, most of them do not pick out bimanual fetal surgery as a central theme but rather address interventions applying a fetoscope with a working channel for a laser fiber, needle or flexible instrument. Most reports were on experimentation in animal models, the human application of minimally invasive fetoscopic bimanual surgery is rare and has at best been explored for the prenatal treatment of spina bifida. Some reported bimanual fetoscopic procedures were performed on the exteriorized uterus via a maternal laparotomy and can therefore not be classified as being truly minimally invasive. Discussion: our results demonstrate that minimally invasive fetoscopic bimanual surgery is rare, even in animal models, excluding many other techniques and procedures that are loosely termed ‘minimally invasive fetal surgery’ which we suggest to better label as ‘interventions’. Thus, more research on percutaneous minimally invasive bimanual fetoscopic surgery is warranted, with the aim to reduce the maternal, uterine and fetal trauma for correction of congenital malformations.

Nature-Derived Okra Gel as Strong Hemostatic Bioadhesive in Human Blood, Liver, and Heart Trauma of Rabbits and Dogs

Bioadhesive performance can be compromised due to bleeding. Bleeding increases mortality. Adhesives with hemostatic function are of great significance. A sustainable and robust hemostatic bioadhesive from okra is reported. The adhesive strength reaches around three and six-fold higher than commercial fibrin on pigskin and glass, respectively. The okra gel presents high-pressure resistance and great underwater adhesive strength. In human blood experiments, the okra gel can activate platelets, enhance the adhesion of activated platelets, and release coagulation factors XI and XII. By forming a fast gel layer and closely adhering to the wound, it can quickly stop bleeding in the liver and heart of rabbits and dogs. Meanwhile, okra gel can cause platelet activation at the wound site and further strengthen its hemostatic performance. It is biocompatible, biodegradable, and can promote wound healing and shows potential as a sustainable bioadhesive, especially in the scenario of significant hemorrhage.

Injectable Click Fibroin Bioadhesive Derived from Spider Silk for Accelerating Wound Closure and Healing Bone Fracture

Wound closure is a critical step in postoperative wound recovery. Substantial advancements have been made in many different means of facilitating wound closure, including the use of tissue adhesives. Compared to conventional methods, such as suturing, tissue bioadhesives better accelerate wound closure. However, several existing tissue adhesives suffer from cytotoxicity, inadequate tissue adhesive strength, and high costs. In this study, a series of bioadhesives was produced using non-swellable spider silk-derived silk fibroin protein and an outer layer of swellable polyethylene glycol and tannic acid. The gelation time of the spider silk-derived silk fibroin protein bioadhesive is less than three minutes and thus can be used during rapid surgical wound closure. By adding polyethylene glycol (PEG) 2000 and tannic acid as co-crosslinking agents to the N-Hydroxysuccinimide (NHS), and 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) reaction, the adhesive strength of the bioadhesive became 2.5 times greater than that of conventional fibrin glue adhesives. Silk fibroin bioadhesives do not show significant cytotoxicity in vitro compared with other bioadhesives. In conclusion, silk fibroin bioadhesive is promising as a new medical tool for more effective and efficient surgical wound closure, particularly in bone fractures.

In situ forming injectable γ-poly(glutamic acid)/PEG adhesive hydrogels for hemorrhage control

Rapidly in situ forming adhesive hydrogels are promising candidates for efficient hemostasis due to their easy administration and minimal invasion. However, development of biocompatible and high-performance hemostatic hydrogels without any additional toxic agents remains a challenge. Herein, a series of novel injectable adhesive hydrogels based on N-hydroxysuccinimide (NHS) modified γ-poly(glutamic acid) (γPGA-NHS) and tetra-armed poly(ethylene glycol) amine (Tetra-PEG-NH₂) were developed. Among all samples, PGA₁₀-PEG₁₅ and PGA₁₀-PEG₂₀ hydrogels with higher PEG contents exhibited rapid gelation time (<20 s), strong mechanical strength (compression modulus up to ∼75 kPa), good adhesive properties (∼15 kPa), and satisfactory burst pressure (∼18-20 kPa). As a result, PGA₁₀-PEG₁₅ and PGA₁₀-PEG₂₀ hydrogels showed a remarkable reduction in hemostasis time and blood loss compared with gauze and fibrin glue. More importantly, the PGA₁₀-PEG₂₀ hydrogel was also successfully used to seal femoral arterial trauma. Subcutaneous implantation experiments indicated a good biocompatibility of the hydrogels in vivo. All these results strongly support that the developed PGA-PEG hydrogels could serve as promising hemostatic agents in emergency and clinical situations.

A double crosslinking adhesion mechanism for developing tough hydrogel adhesives

Tough hydrogel adhesives that consist of a robust gel network and can strongly adhere to wet tissues have shown great promise as the next generation of bioadhesives. While a variety of chemistries can be utilized to construct the tough gel network, the covalent conjugation methods for tissue adhesion are still limited. Here we report, for the first time, the use of side product-free amine-thiolactone chemistry which initiates a double crosslinking adhesion mechanism to develop tough gel adhesives. Thiolactone groups can conjugate with tissue-surface amines via a ring-opening reaction. The resultant thiol end groups can be further crosslinked into disulfide linkages, enabling the formation of a robust and stable adhesion layer. The thiolactone-bearing tough hydrogel composed of methacrylate-modified gelatin, acrylic acid, and thiolacone acrylamide exhibited good biocompatibility and mechanical properties, and strong adhesion to various types of engineering solids and tissues. We also demonstrated its ability to function as a tissue sealant and drug depot. The novel adhesion mechanism will diversify future design of bioadhesives for hemostasis, drug delivery, tissue repair, and other applications. STATEMENT OF SIGNIFICANCE: Tough hydrogel adhesives with excellent tissue-adhesive and mechanical properties have demonstrated tremendous promise for hemostasis, tissue repair, and drug delivery applications. However, the covalent chemistry for tissue adhesion has been limited, which narrows the choice of materials for the design of bioadhesives and may pose a safety concern. Here, for the first time, we report the use of side product-free amine-thiolactone chemistry, which involves a double crosslinking adhesion mechanism, for developing tough hydrogel adhesives. We demonstrate that thiolactone-bearing tough hydrogels exhibit favorable biocompatibility and mechanical properties, and superior adhesion to both engineering solids and tissues. Our new adhesion technology will greatly facilitate future development of advanced bioadhesives for numerous biomedical applications.

Adhesive anastomosis for organ transplantation

The recent development of tough tissue adhesives has stimulated intense interests among material scientists and medical doctors. However, these adhesives have seldom been tested in clinically demanding surgeries. Here we demonstrate adhesive anastomosis in organ transplantation. Anastomosis is commonly conducted by dense sutures and takes a long time, during which all the vessels are occluded. Prolonged occlusion may damage organs and even cause death. We formulate a tough, biocompatible, bioabsorbable adhesive that can sustain tissue tension and pressurized flow. We expose the endothelial surface of vessels onto a gasket, press two endothelial surfaces to the adhesive using a pair of magnetic rings, and reopen the bloodstream immediately. The time for adhesive anastomosis is shortened compared to the time for sutured anastomosis. We have achieved adhesive anastomosis of a great vein in transplanting the liver of a pig. After the surgery, the adhesive is absorbed, the vein heals, and the pig lives for over one month.