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

Hydrogel adhesives for tissue recovery

Hydrogel adhesives (HAs) are promising and rewarding tools for improving tissue therapy management. Such HAs had excellent properties and potential applications in biological tissues, such as suture replacement, long-term administration, and hemostatic sealing. In this review, the common designs and the latest progress of HAs based on various methodologies are systematically concluded. Thereafter, how to deal with interfacial water to form a robust wet adhesion and how to balance the adhesion and non-adhesion are underlined. This review also provides a brief description of gelation strategies and raw materials. Finally, the potentials of wound healing, hemostatic sealing, controlled drug delivery, and the current applications in dermal, dental, ocular, cardiac, stomach, and bone tissues are discussed. The comprehensive insight in this review will inspire more novel and practical HAs in the future.

"Double-sided protector" Janus hydrogels for skin and mucosal wound repair: applications, mechanisms, and prospects

Skin and mucous membranes serve as crucial barrier tissues within the human body. Defective wound healing not only inflicts pain but also heightens the risk of infection and impairs immune function. Janus hydrogels possess two-sided distinct asymmetric structures that endow them with diverse properties such as high water absorbency, flexibility, anti-adhesion ability etc. These hydrogels also exhibit great potential in biofluid transport, drug delivery and promoting tissue repair. Currently, research efforts predominantly concentrate on the preparation techniques, properties, and biomedical applications. This review summarized its structural characteristics and different forms of designations, and focused on the possible mechanisms, the existing problems and improvement strategies for the skin and mucous tissues wound, aiming to provide new design ideas for repairing complex skin and mucous membrane tissue defects.

Multifunctional Janus Hydrogels: Surface Design Strategies for Next-Generation Clinical Solutions

Janus hydrogels, distinguished by their dual-sided structure with distinct physical and chemical properties, have garnered significant attention in the medical field, particularly for applications in drug delivery, tissue engineering, and wound healing. Their ability to simultaneously perform multiple functions, such as targeted drug release and biomimetic tissue interaction, positions them as a promising platform for advanced therapeutic strategies. The growing interest in these hydrogels is primarily driven by their multifunctionality and capacity to address complex biological needs. This review delves into the design, fabrication methods, and applications of Janus hydrogels in medicine, focusing on their potential to overcome the limitations of conventional therapies and providing a comprehensive overview of their role in contemporary biomedical applications.

A novel strategy for addressing post-surgical abdominal adhesions: Janus hydrogel

Abdominal adhesions are a frequent complication after abdominal surgery, which can cause significant pain and burden to patients. Despite various treatment options, including surgical intervention and pharmacotherapy, these often fail to consistently and effectively prevent postoperative abdominal adhesions. Janus hydrogel is famous for its asymmetric characteristics, which shows great prospects in the prevention and treatment of abdominal adhesion. This review outlines the preparation methods, mechanisms of action, and key applications of Janus hydrogel in the prevention of postoperative abdominal adhesions. Furthermore, we examine the current limitations of the Janus hydrogel anti-adhesion barrier and explore potential future directions for its development.

AA/MA/AMA copolymer and chitosan as self-gelling powders for rapid hemostasis and robust tissue adhesion

Bleeding control by traditional hemostatic materials poses a risk of continuing oozing bleeding, while existing self-gelling hemostatic powders still face challenges in simultaneously achieving robust wound sealing and effectively accelerating blood coagulation. Herein, we reported acrylic acid/methacrylic acid/2-aminoethyl methacrylate copolymer (PAMA) and chitosan (CS) as a new type of self-gelling composite powder (PAMA-CS) for acute bleeding wound sealing with reduced blood leakage. Upon rapid blood absorption, PAMA-CS powders could quickly form an adhesive hydrogel that strongly binds to bleeding tissues, exhibiting high burst pressure tolerance (up to 452.6 mmHg) for wound sealing to prevent bleeding. The incorporation of chitosan endowed significantly enhanced liquid uptake ability and accelerated blood coagulation (clot index of 77.92 % within 30 s) to the PAMA-CS powder. Based on the synergistic effect of tight adhesive sealing and accelerating intrinsic blood coagulation, PAMA-CS powders could achieve effective hemostasis within 20 s for acute bleeding liver and stomach on rats, outperforming commercial hemostatic chitosan powders. Combined with rapid hemostasis, tight & stable wound sealing, and favorable biodegradation, PAMA-CS powders may serve as a promising hemostatic candidate for emergency bleeding control and wound closure.

Fluorinated poly(aryl ether)/polypropylene composite patch for prevention of abdominal adhesions after hernia repairs

Hernia typically does not heal spontaneously. Large-pore patches, most notably polypropylene patches (PP patches), are the gold standard in hernia repair surgery. However, a single patch is insufficient for both anti-adhesion and tissue fusion, leading to complications such as organ adhesions. In this study, a chemically stable and biocompatible modified fluorinated poly(aryl ether) (FPAE-F) was prepared by grafting perfluoroalkyl groups onto a fluorinated poly(aryl ether) via nucleophilic aromatic substitution. A porous FPAE-F fiber film (eFPAE-F) was fabricated by electrospinning and combined with a PP patch to produce a modified fluorinated poly(aryl ether)/polypropylene (FPAE-F/PP) composite patch. The eFPAE-F layer of the composite patch, which faces the abdominal viscera, exhibits a water contact angle of 151.3 ± 1.2°. This superhydrophobic surface prevents protein adhesion, thereby inhibiting rapid fibroblast proliferation. The small pore size (3.22 ± 1.25 μm) of the eFPAE-F layer effectively impedes fibroblast infiltration while permitting the transport and metabolism of nutrients. In vivo experiments have demonstrated that the composite patch is a viable anti-adhesion material, resulting in no adhesions and low inflammation levels after 2 weeks. Due to its outstanding anti-adhesion properties, eFPAE-F/PP is expected to be applied in the field of hernia repair.

Progress in Polysaccharide-Based Hydrogels for Preventing Postoperative Adhesions: A Review

Postoperative adhesions are common complications following surgery, often accompanied by pain and inflammation that significantly diminish patients' quality of life. Moreover, managing postoperative adhesions incurs substantial cost, imposing a considerable financial burden on both patients and healthcare systems. Traditional anti-adhesion materials are confronted with limitations, such as inadequate tissue adherence in a moist environment and poor degradability, underscoring the urgent need for more effective solutions. Recently, polysaccharide-based hydrogels have received considerable attention for their potential in preventing postoperative adhesions. The hydrogels not only facilitate wound healing but also effectively reduce inflammation, providing a promising approach to preventing postoperative adhesions. This review provides an extensive analysis of the progress made in the development of polysaccharide-based hydrogels for postoperative anti-adhesion therapy. It highlights their principal benefits, outlines future research trajectories, and addresses the ongoing challenges that need to be overcome.

Double-Dynamic-Bond Cross-Linked Hydrogel Adhesive with Cohesion-Adhesion Enhancement for Emergency Tissue Closure and Infected Wound Healing

The hydrogel adhesives with strong tissue adhesion and biological characteristics are urgently needed for injury sealing and tissue repair. However, the negative correlation between tissue adhesion and the mechanical strength poses a challenge for their practical application. Herein, a bio-inspired cohesive enhancement strategy is developed to prepare the hydrogel adhesive with simultaneously enhanced mechanical strength and tissue adhesion. The double cross-linked network is achieved through the cooperation between polyacrylic acid grafted with N-hydroxy succinimide crosslinked by tannic acid and cohesion-enhanced ion crosslinking of sodium alginate and Ca2+. Such a unique structure endows the resultant hydrogel adhesive with excellent tissue adhesion strength and mechanical strength. The hydrogel adhesive is capable of sealing various organs in vitro, and exhibits satisfactory on-demand removability, antibacterial, and antioxidant properties. As a proof of concept, the hydrogel adhesive not only effectively halts non-compressible hemorrhages of beating heart and femoral artery injury models in rats, but also accelerates the healing of infected wound by inhibiting bacteria and reducing inflammation. Overall, this advanced hydrogel adhesive is promising as an emergency rescue adhesive that enables robust tissue closure, timely controlling bleeding, and promoting damaged tissue healing.

Advances in Adhesive Materials for Oral and Maxillofacial Soft Tissue Diseases

Oral diseases represent a prevalent global health burden, profoundly affecting patients' quality of life. Given the involvement of oral mucosa and muscles in diverse physiological functions, coupled with clinical aesthetics considerations, repairing oral and maxillofacial soft tissue defects poses a formidable challenge. Wet-adhesive materials are regarded as promising oral repair materials due to their unique advantages in easily overcoming physical and biological barriers in the oral cavity. This review first introduces the intricate wet-state environment prevalent in the oral cavity, meticulously explaining the fundamental physical and chemical adhesion mechanisms that underpin adhesive materials. It then comprehensively summarizes the diverse types of adhesives utilized in stomatology, encompassing polysaccharide, protein, and synthetic polymer adhesive materials. The review further evaluates the latest research advancements in utilizing these materials to treat various oral and maxillofacial soft tissue diseases, including oral mucosal diseases, periodontitis, peri-implantitis, oral and maxillofacial skin defects, and maxillofacial tumors. Finally, it also highlights the promising future prospects and pivotal challenges related to stomatology application of multifunctional adhesive materials.

An In Situ UV Cross-Linking Asymmetric Adhesive Hydrogel for Noncompressible Hemostasis and Postoperative Adhesion Prevention

Noncompressible hemorrhage control is vital for clinical outcome after surgical treatment and prehospital trauma injuries. Meanwhile, wound bleeding and tissue damage could induce postoperative adhesions, leading to a severe threat to the health of patients. Considerable research had been conducted on the development of hemostatic and antiadhesive materials. However, it was still a great challenge to realize hemostasis and antiadhesion simultaneously especially in inaccessible and irregular wound sites. In this study, a kind of fluid hemostatic agent composed of gelatin methacryloyl/sulfobetaine methacrylate/oxidized konjac glucomannan (termed GOS) was developed, which spread immediately upon contacting the hepatic trauma surface and turned into hydrogels under UV radiation within 5 s, resulting in rapid hemostasis and firm adhesion to tissues (shear strength 486.08 kPa). Importantly, the surface of the as-formed GOS hydrogel exhibited lubricious and nonadhesive properties, exhibiting excellent anti-postoperative adhesion performance in a rat liver hemostasis model and a rat abdominal wall-cecum adhesion model. In addition, the GOS hydrogel reduced the postoperative secretion of inflammatory factors TNF-α and IL-6, facilitating the tissue repair. Therefore, the asymmetrical adhesive GOS hydrogel could fulfill the requirements for simultaneously rapid hemostasis, tissue adhesion, and subsequent excellent antiadhesion, which demonstrated significant potential for diverse clinical surgical operation scenarios.

Rapid Fluid-Induced-Expanding Chitosan-Derived Hemostatic Sponges with Excellent Antimicrobial and Antioxidant Properties for Incompressible Hemorrhage and Wound Healing

Chitosan-based materials are known for their excellent biocompatibility and inherent hemostatic properties. However, their hemostatic efficiency is significantly affected by poor wettability and mechanical strength. Herein, we developed a novel hemostatic super elastic sponge from mussel-inspired chitosan modified with long alkyl and catechol functional groups (HMCC) via a simple freezing-drying procedure. The incorporation of decanal and catechol in the HMCC sponge significantly enhances its antimicrobial and antioxidant properties and facilitates multiple interactions with blood cells, thus promoting their enrichment for rapid hemostasis. Moreover, HMCC sponges exhibit high compressibility and rapid fluid-induced size recovery capacity, enabling wound shape adaptation to ensure minimizing irritation. In vivo experiments revealed that HMCC sponges possessed enhanced procoagulant, hemostasis abilities, and favorable degradability and could promote wound healing in a rat skin wound model. These results highlight the potential of the HMCC sponge as a promising solution for the clinical management of major bleeding.

A supramolecular hydrogel leveraging hierarchical multi-strength hydrogen-bonds hinged strategy achieving a striking adhesive-mechanical balance

To obtain high-performance tissue-adhesive hydrogel embodying excellent mechanical integrity, a supramolecular hydrogel patch is fabricated through in situ copolymerization of a liquid-liquid phase separation precursor composed of self-complementary 2-2-ureido-4-pyrimidone-based monomer and acrylic acid coupled with subsequent corporation of bioactive epigallocatechin gallate. Remarkably, the prepared supramolecular hydrogel leverages hierarchical multi-strength hydrogen-bonds hinged strategy assisted by alkyl-based hydrophobic pockets, broadening the distribution of binding strength of physical junctions, striking a canonical balance between superb mechanical performance and robust adhesive capacity. Ultimately, the fabricated supramolecular hydrogel patch stands out as a high stretchability (1500 %), an excellent tensile strength (2.6 MPa), a superhigh toughness (12.6 MJ m-3), an instant and robust tissue adhesion strength (263.2 kPa for porcine skin), the considerable endurance under cyclic loading and reversible adhesion, a superior burst pressure tolerance (108 kPa) to those of commercially-available tissue sealants, and outstanding anti-swelling behavior. The resultant supramolecular hydrogel patch demonstrates the rapid hemorrhage control within 60 s in liver injury and efficient wound closure and healing effects with alleviated inflammation and reduced scarring in full-thickness skin incision, confirming its medical translation as a promising self-rescue tissue-adhesive patch for hemorrhage prevention and sutureless wound closure.

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

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

Self-assembling chitosan based injectable and expandable sponge with antimicrobial property for hemostasis and wound healing

Chitosan and chitosan derivative are widely used in hemostasis, antibiosis and wound repair for its good biocompatibility and unique effect. However, the preparation of chitosan based hemostatic materials or wound dressings generally involves chemical crosslinking agent introduction, acid residue or complicated preparation process, which limits its clinical application. In this study, an injectable and expandable chitosan sponge was constructed by chitosan (CS) and quaternized chitosan (QCS) self-assembly without acid retention and chemical crosslinker introduction. In the neutral condition, the hydrogen bond of CS molecules can act as the driving force to form cross-linking network, and the QCS was introduced to regulate the hydrogen bond of CS to avoid the excessive aggregation. The porous QCS/CS sponge was obtained by freeze-drying of the self-assembly QCS/CS hydrogel. The sponge exhibited high expansibility, injectability and water/blood triggered shape memory property. Due to the introduction of QCS, the sponge showed good antibacterial properties, which can protect the wound from bacterial invasion. The convenient and green preparation method of injectable and expandable QCS/CS sponge is a potential method for the treatment of hemostasis and wound healing.

Bioinspired Asymmetric-Adhesion Janus Hydrogel Patch Regulating by Zwitterionic Polymers for Wet Tissues Adhesion and Postoperative Adhesion Prevention

Asymmetrically adhesive hydrogel patch with robust wet tissue adhesion simultaneously anti-postoperative adhesion is essential for clinical applications in internal soft-tissue repair and postoperative anti-adhesion. Herein, inspired by the lubricative role of serosa and the underwater adhesion mechanism of mussels, an asymmetrically adhesive hydrogel Janus patch is developed with adhesion layer (AL) and anti-adhesion layer (anti-AL) through an in situ step-by-step polymerization process in the mold. The AL exhibits excellent adhesion to internal soft-tissues. In contrast, the anti-AL demonstrated ultralow fouling property against protein and fibroblasts, which hinders the early and advanced stages of development of the adhesion. Moreover, the Janus patch simultaneously promotes tissue regeneration via ROS clearance capability of catechol moieties in the AL. Results from in vivo experiments with rabbits and rats demonstrate that the AL strongly adheres to traumatized tissue, while the anti-AL surface demonstrate efficacy in preventing of post-abdominal surgery adhesions in contrast to clinical patches. Considering the advantages in terms of therapeutic efficacy and off the shelf, the Janus patch developed in this work presents a promise for preventing postoperative adhesions and promoting regeneration of internal tissue defects.

Janus-Structured Microgel Barrier with Tissue Adhesive and Hemostatic Characteristics for Efficient Prevention of Postoperative Adhesion

Postoperative adhesion (POA) is a common and serious complication following various types of surgery. Current physical barriers either have a short residence time at the surgical site with a low tissue attachment capacity or are prone to undesired adhesion formation owing to the double-sided adhesive property, which limits the POA prevention efficacy of the barriers. In this study, Janus-structured microgels (Janus-MGs) with asymmetric tissue adhesion capabilities are fabricated using a novel bio-friendly gas-shearing microfluidic platform. The anti-adhesive side of Janus-MGs, which consists of alginate, hyaluronic acid, and derivatives, endows the material with separation, lubrication, and adhesion prevention properties. The adhesive side provided Janus-MGs with tissue attachment and retention capability through catechol-based adhesion, thereby enhancing the in situ adhesion prevention effect. In addition, Janus-MGs significantly reduced blood loss and shortened the hemostatic time in rats, further reducing adhesion formation. Three commonly used rat POA models with different tissue structures and motion patterns are established in this study, namely peritoneal adhesion, intrauterine adhesion, and peritendinous adhesion models, and the results showed that Janus-MGs effectively prevented the occurrence of POA in all the models. The fabrication of Janus-MGs offers a reliable strategy and a promising paradigm for preventing POA following diverse surgical procedures.

A Dry Patch with In Situ Solid-to-Gel Transformation for All-in-One Skin Wound Care

Hydrogel-based dressing materials offer significant potential in expediting skin wound healing. Nevertheless, they face several challenges: poor adhesion to wound tissues, difficulties in preservation under ambient conditions, and limited multifunctionality to support all wound healing stages. In this work, a dry patch is designed to address these persistent issues by featuring an in situ solid-to-gel transformation and Janus wet tissue adhesiveness. The HGP patch integrates a wet adhesive layer combining dopamine-conjugated hyaluronic acid (HD) and poly(acrylic acid) (PAA), a drug-loading layer comprising gelatin (Gel), and a nonadhesive gelation layer of poly(vinyl alcohol) (PVA) and sodium alginate (SA). This hierarchical structural design confers exceptional wound adhesion, hemostatic capabilities, and antibacterial and antioxidant activities, as well as immune regulatory properties. These attributes collectively support accelerated skin wound healing, particularly in cases complicated by bacterial infections. This research charts an approach to engineer hydrogel-based wound dressings through on-site hydrogel formation, thus advancing the treatment of wounds afflicted with complex infections.

An integrally formed Janus supramolecular bio-gel with intelligent adhesion for multifunctional healthcare

Despite the rapid development of Janus adhesive hydrogels, most of them still entail complex fabrication processes and have the inherent flaws, such as fragility and instability, thereby restricting their biomedical applications. In this study, a novel Janus bio-gel with strong mechanical and intelligent adhesion functions is facilely fabricated through a gravity-driven settlement strategy, employing poly-cyclodextrin microspheres (PCDMs). This strategy takes advantage of the sedimentation behavior of PCDMs with various diameters to establish structural disparities on both sides of the Janus bio-gel, thereby resolving multiple predicaments including the tedious synthesis steps and poor bonding of multilayer hydrogels. Owing to the multiple dynamic interactions between polymers and PCDMs, the Janus supramolecular bio-gel demonstrates outstanding mechanical toughness (1.97 MJ/m3) and elongation rate (≈800 %). More attractively, the resulting Janus bio-gel exhibits remarkable adhesiveness (316.4 J/m2 for interfacial toughness) and adhesive differences that are exceed 50 times between the two surfaces. Furthermore, the Janus supramolecular bio-gel also has excellent antibacterial properties, biocompatibility, environmental stability, and multiple monitoring functions, accelerating wound stably healing and monitoring physiologic parameters on the skin. This strategy provides a straightforward and promising approach to directly achieve multifunctional integration for smart health management.

A tough Janus poly(vinyl alcohol)-based hydrogel for wound closure and anti postoperative adhesion

Traditional adhesive hydrogels perform well in tissue adhesion but they fail to prevent postoperative tissue adhesion. To address this challenge, a biodegradable Janus adhesive hydrogel (J-AH) was designed and fabricated by the assembly of three different functional layers including anti-adhesive layer, reinforceable layer, and wet tissue adhesive layer. Each layer of J-AH serves a specific function: the top zwitterionic polymeric anti-adhesive layer shows superior resistance to cell/protein and tissue adhesion; the middle poly(vinyl alcohol)/tannic acid reinforceable matrix layer endows the hydrogel with good mechanical toughness of ∼2.700 MJ/m3; the bottom poly(acrylic acid)/polyethyleneimine adhesive layer imparts tough adhesion (∼382.93 J/m2 of interfacial toughness) to wet tissues. In the rat liver and femoral injury models, J-AH could firmly adhere to the bleeding tissues to seal the wounds and exhibit impressive hemostatic efficiency. Moreover, in the in vivo adhesion/anti-adhesion assay of J-AH between the defected cecum and peritoneal walls, the top anti-adhesive layer can effectively inhibit undesired postoperative abdominal adhesion and inflammatory reaction. Therefore, this research may present a new strategy for the design of advanced bio-absorbable Janus adhesive hydrogels with multi-functions including tissue adhesion, anti-postoperative adhesion and biodegradation. STATEMENT OF SIGNIFICANCE: Despite many adhesive hydrogels with tough tissue adhesion capability have been reported, their proclivity for undesired postoperative adhesion remains a serious problem. The postoperative adhesion may lead to major complications and even endanger the lives of patients. The injectable hydrogels can cover the irregular wound and suppress the formation of postoperative adhesion. However, due to the lack of adhesive properties with tissue, it is difficult for the hydrogels to maintain on the wound surface, resulting in poor anti-postoperative adhesion effect. Herein, we design a Janus adhesive hydrogel (J-AH). J-AH integrates together robust wet tissue adhesion and anti-postoperative adhesion. Therefore, this research may present a new strategy for the design of advanced bio-absorbable Janus adhesive hydrogels.

3D printing/electrospinning of a bilayered composite patch with antibacterial and antiadhesive properties for repairing abdominal wall defects

The application of patch methods for repairing abdominal wall wounds presents a variety of challenges, such as adhesion and limited mobility due to inadequate mechanical strength and nonabsorbable materials. Among these complications, postoperative visceral adhesion and wound infection are particularly serious. In this study, a bilayered composite patch with a gelatin methacryloyl (GelMA)/sodium alginate (SA)-vancomycin (Van)@polycaprolactone (PCL) (GelMA/SA-Van@PCL) antibacterial layer was prepared via coaxial 3D printing and a polycaprolactone (PCL)-silicon dioxide (SiO2) antiadhesive layer (PCL-SiO2) was prepared via electrospinning and electrostatic spray for hernia repair. The evaluation of the physicochemical properties revealed that the composite patch had outstanding tensile properties (16 N cm-1), excellent swelling (swelling rate of 243.81 ± 12.52%) and degradation (degradation rate of 53.14 ± 3.02%) properties. Furthermore, the composite patch containing the antibiotic Van exhibited good antibacterial and long-term drug release properties. Both in vivo and in vitro experiments indicated that the composite patch displayed outstanding biocompatibility and antiadhesive properties and could prevent postoperative infections. In summary, the bilayered composite patch can effectively prevent postoperative complications while promoting tissue growth and repair and holds significant application potential in hernia repair.

Engineered Janus hydrogels: biomimetic surface engineering and biomedical applications

Hydrogel bioadhesives, when applied to dysfunctional tissues substituting the epidermis or endothelium, exhibit compelling characteristics that enable revolutionary diagnostic and therapeutic procedures. Despite their demonstrated efficacy, these hydrogels as soft implants are still limited by improper symmetric surface functions, leading to postoperative complications and disorders. Janus hydrogel bioadhesives with unique asymmetric surface designs have thus been proposed as a reliable and biocompatible hydrogel interface, mimicking the structural characteristics of natural biological barriers. In this comprehensive review, we provide guidelines for the rational design of Janus hydrogel bioadhesives, covering methods for hydrogel surface chemistry and microstructure engineering. The engineering of Janus hydrogels is highlighted, specifically in tuning the basal surface to facilitate instant and robust hydrogel-tissue integration and modulating the apical surface as the anti-adhesion, anti-fouling, and anti-wear barrier. These asymmetric designs hold great potential in clinical translation, supporting applications including hemostasis/tissue sealing, chronic wound management, and regenerative medicine. By shedding light on the potential of Janus hydrogels as bioactive interfaces, this review paper aims to inspire further research and overcome current obstacles for advancing soft matter in next-generation healthcare.

Accelerated, injectable, self-healing, scarless wound dressings using rGO reinforced dextran/chitosan hydrogels incorporated with PDA-loaded asiaticoside

The process of wound healing is intricate and complex, necessitating the intricate coordination of various cell types and bioactive molecules. Despite significant advances, challenges persist in achieving accelerated healing and minimizing scar formation. Herein, a multifunctional hydrogel engineered via dynamic Schiff base crosslinking between oxidized dextran and quaternized chitosan, reinforced with reduced graphene oxide (rGO) is reported. The resulting OQG hydrogels demonstrated injectability to aid in conforming to irregular wound geometries, rapid self-healing to maintain structural integrity and adhesion for intimate integration with wound beds. Moreover, the developed hydrogels possessed antioxidant and antibacterial activities, mitigating inflammation and preventing infection. The incorporation of conductive rGO further facilitated the transmission of endogenous electrical signals, stimulating cell migration and tissue regeneration. In addition, the polydopamine-encapsulated asiaticoside (AC@PDA) nanoparticles were encapsulated in OQG hydrogels to reduce scar formation during in vivo evaluations. In vitro results confirmed the histocompatibility of the hydrogels to promote cell migration. The recovery of the full-thickness rat wounds revealed that these designed OQG hydrogels with the incorporation of AC@PDA nanoparticles could accelerate wound healing, reduce inflammation, facilitate angiogenesis, and minimize scarring when implemented. This multifunctional hydrogel system offers a promising strategy for enhanced wound management and scarless tissue regeneration, addressing the multifaceted challenges in wound care.

A Janus hydrogel that enables wet tissue adhesion and resists abdominal adhesions

Hydrogels have indeed achieved significant advancements, yet their clinical translation has been hampered by their inherent limitations in wet adhesion properties. Furthermore, the design of adhesive hydrogels that can resist postoperative adhesions remains an intricate challenge. In this study, we introduce a Janus hydrogel (JGP) that offers a novel approach to address these challenges. The JGP hydrogel has two asymmetrical sides, consisting of an adhesion layer (AL) and an anti-adhesion layer (AAL). Specifically, the AL incorporates three key components: N-[tris(hydroxymethyl)methyl]acrylamide (THMA), acrylic acid (AAc), and the acrylic acid N-hydroxysuccinimide ester (AAc-NHS). By drying the AL, it has a rapid water absorption capability. The abundance of hydroxyl and carboxyl groups in the AL enables the formation of robust hydrogen bonds with tissues, thereby achieving superior adhesive properties. Additionally, the synergistic effect of THMA's tridentate hydrogen bonding and the covalent bonding formed by AAc-NHS with tissue ensures long-lasting wet adhesion. To realize the anti-adhesion function, one side of the AL was immersed in a solution of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), which undergoes crosslinking to form the AAL. A comprehensive series of tests have confirmed that the JGP hydrogel exhibits exceptional mechanical properties, efficient and enduring adhesion, excellent biocompatibility, and degradability. Moreover, it possesses remarkable hemostatic properties and robust anti-abdominal adhesion characteristics.

A bioinspired injectable antioxidant hydrogel for prevention of postoperative adhesion

Postoperative adhesions, a prevalent complication following abdominal surgery, affect 90% of patients undergoing abdominal surgical procedures. Currently, the primary approach to prevent postoperative adhesions involves physical isolation of the surgical site and surrounding tissues using a hydrogel; however, this method represents a rudimentary strategy. Herein, considering the impact of oxidative stress and free radicals on postoperative adhesion during wound healing, an injectable antioxidant hydrogel, named PU-OHA-D, was successfully synthesized, which is formed by the crosslinking of dopamine-modified oxidized hyaluronic acid (OHA-D) and dihydrazide-terminated polyurethane (PU-ADH) through hydrazone bonding. PU-OHA-D hydrogel possesses versatile characteristics such as rapid gel formation, injectability, self-repair capability and biodegradability. Additionally, they exhibit an excellent ability to clear free radicals and superior tissue adhesion. PU-OHA-D can be injected in situ to form a hydrogel to prevent abdominal wall-cecum adhesion. Importantly, it can effectively eliminate free radicals and inhibit oxidative stress at the wound site. Thereby, it leads to collagen physiological degradation and prevents the occurrence of postoperative adhesions. The bioinspired hydrogel demonstrates its great potential in preventing postoperative adhesion and promoting wound healing.

Advances of biological macromolecules hemostatic materials: A review

Achieving hemostasis is a necessary intervention to rapidly and effectively control bleeding. Conventional hemostatic materials currently used in clinical practice may aggravate the damage at the bleeding site due to factors such as poor adhesion and poor adaptation. Compared to most traditional hemostatic materials, polymer-based hemostatic materials have better biocompatibility and offer several advantages. They provide a more effective method of stopping bleeding and avoiding additional damage to the body in case of excessive blood loss. Various hemostatic materials with greater functionality have been developed in recent years for different organs using diverse design strategies. This article reviews the latest advances in the development of polymeric hemostatic materials. We introduce the coagulation cascade reaction after bleeding and then discuss the hemostatic mechanisms and advantages and disadvantages of various polymer materials, including natural, synthetic, and composite polymer hemostatic materials. We further focus on the design strategies, properties, and characterization of hemostatic materials, along with their applications in different organs. Finally, challenges and prospects for the application of hemostatic polymeric materials are summarized and discussed. We believe that this review can provide a reference for related research on hemostatic materials, contributing to the further development of polymer hemostatic materials.

Janus hydrogels: merging boundaries in tissue engineering for enhanced biomaterials and regenerative therapies

In recent years, the design and synthesis of Janus hydrogels have witnessed a thriving development, overcoming the limitations of single-performance materials and expanding their potential applications in tissue engineering and regenerative medicine. Janus hydrogels, with their exceptional mechanical properties and excellent biocompatibility, have emerged as promising candidates for various biomedical applications, including tissue engineering and regenerative therapies. In this review, we present the latest progress in the synthesis of Janus hydrogels using commonly employed preparation methods. We elucidate the surface and interface interactions of these hydrogels and discuss the enhanced properties bestowed by the unique "Janus" structure in biomaterials. Additionally, we explore the applications of Janus hydrogels in facilitating regenerative therapies, such as drug delivery, wound healing, tissue engineering, and biosensing. Furthermore, we analyze the challenges and future trends associated with the utilization of Janus hydrogels in biomedical applications.

Hemoadhican-Based Bioabsorbable Hydrogel for Preventing Postoperative Adhesions

Postoperative peritoneal adhesions are a prevalent clinical issue following abdominal and pelvic surgery, frequently resulting in heightened personal and societal health burdens. Traditional biomedical barriers offer limited benefits because of practical challenges for doctors and their incompatibility with laparoscopic surgery. Hydrogel materials, represented by hyaluronic acid gels, are receiving increasing attention. However, existing antiadhesive gels still have limited effectiveness or carry the risk of complications in clinical applications. Herein, we developed a novel hydrogel using polysaccharide hemoadhican (HD) as the base material and polyethylene glycol diglycidyl ether (PEGDE) as the cross-linking agent. The HD hydrogels exhibit appropriate mechanical properties, injectability, and excellent cytocompatibility. We demonstrate resistance to protein adsorption and L929 fibroblast cell adhesion to the HD hydrogel. The biodegradability and efficacy against peritoneal adhesion are further evaluated in C57BL/6 mice. Our results suggest a potential strategy for anti-postoperative tissue adhesion barrier biomaterials.

Janus Polyurethane Adhesive Patch with Antibacterial Properties for Wound Healing

Despite the rapid development of tissue adhesives, flaws including allergies, poor stability, and indiscriminate double-sided adhesive properties limit their application in the medical field. In this work, Janus polyurethane patches were spontaneously prepared by adjusting the difference in the functional group distribution between the top and bottom sides of the patch during emulsion drying. Consequently, poor adhesion was exhibited on the bottom surface, while the top surface can easily adhere to metals, polymers, glasses, and tissues. The difference in adhesive strength to pork skin between the two surfaces is more than 5 times. The quaternary ammonium salt and hydrophilic components on the surface of the polyurethane patch enable the rapid removal and absorption of water from the tissue surface to achieve wet adhesion. Animal experiments have demonstrated that this multifunctional Janus polyurethane patch can promote skin wound closure and healing of infected wounds. This facile and effective strategy to construct Janus polyurethane patch provides a promising method for the development of functional tissue-adhesives.

Double-layer adhesives for preventing anastomotic leakage and reducing post-surgical adhesion

Preventing anastomotic leakage (AL) and postoperative adhesions after gastrointestinal surgery is crucial for ensuring a favorable surgical prognosis. However, AL prevention using tissue adhesives can unintentionally lead to undesirable adhesion formation, while anti-adhesive agents may interfere with wound healing and contribute to AL. In this study, we have developed a double-layer patch, consisting of an adhesive layer on one side, utilizing gallic acid-conjugated chitosan (CHI-G), and an anti-adhesive layer on the opposite side, employing crosslinked hyaluronic acid (cHA). These CHI-G/cHA double-layer adhesives significantly prevented AL by forming physical barriers of CHI-G and reduced post-surgical adhesion at the anastomosis sites by the anti-adhesive layers of cHA. The bursting pressure (161.1 ± 21.6 mmHg) of double-layer adhesives-applied rat intestine at postoperative day 21 was far higher than those of the control (129.4 ± 5.7 mmHg) and the commercial anti-adhesives-applied group (120.8 ± 5.2 mmHg). In addition, adhesion score of double-layer adhesives-applied rat intestine was 3.6 ± 0.3 at postoperative day 21, which was similar to that of the commercial anti-adhesives-applied group (3.6 ± 0.3) and lower than that of the control group (4.9 ± 0.5). These findings indicate that the double-layer patch (CHI-G/cHA) has the potential to effectively prevent both postoperative adhesions and anastomotic leakage, offering a promising solution for gastrointestinal surgery.