Fast and High Strength Soft Tissue Bioadhesives Based on a Peptide Dendrimer with Antimicrobial Properties and Hemostatic Ability

An in situ catechol functionalized ε-polylysine/polyacrylamide hydrogel formed by hydrogen bonding recombination with high mechanical property for hemostasis

In situ hydrogel has attracted widely attention in hemostasis due to its ability to match irregular defects, but its application is limited by insufficient mechanical strength and long gelation time. Although some specifical in situ chemically cross-linked hydrogels could be fast formed and exhibit high mechanical strength, they unable to absorb blood. Hence their applications were further limited in emergency hemostasis usage. In this study, a robust hydrogel formed by hydration of powders was developed using multiple hydrogen bonds crosslinking. Here, catechol groups modified ε-polylysine (PL-CAT) and polyacrylamide (PAAM) were used to construct the PL-CAT/PAAM hydrogel. This hydrogel could be formed within 7 s to adhere and seal bleeding sites. The catechol groups endowed the hydrogel outstanding adhesive strength, which was 3.5 times of fibrin glue. Besides, the mechanical performance of in-situ PL-CAT/PAAM hydrogel was explored and the results showed that the hydrogel exhibited high compressive strength (0.47 MPa at 85% strain). Most importantly, the blood loss of wound treated with PL-CAT/PAAM hydrogel powders was 1/7 of untreated group, indicating the hydrogel's excellent hemostatic effect. And the cytotoxicity studies indicated that the PL-CAT/PAAM hydrogel had low toxicity. To summarize, this hydrogel could be a potential hemostatic material in emergency situations.

Injectable Hydrogel Based on Modified Gelatin and Sodium Alginate for Soft-Tissue Adhesive

To assist or replace the traditional suture techniques for wound closure, soft-tissue adhesives with excellent adhesion strength and favorable biocompatibility are of great significance in biomedical applications. In this study, an injectable hydrogel tissue adhesive containing adipic acid dihydrazide–modified gelatin (Gel-ADH) and oxidized sodium alginate (OSA) was developed. It was found that this tissue adhesive possessed a uniform structure, appropriate swelling ratio, good injectability, and excellent hemocompatibility and cytocompatibility. The adhesion capacity of the developed adhesive with optimized component and concentration was stronger than that of the commercial adhesive Porcine Fibrin Sealant Kit. All these results suggested that the developed hydrogel was a promising candidate for a soft-tissue adhesive.

A double-network polysaccharide-based composite hydrogel for skin wound healing

Effective wound dressings are of great significance in preventing infections and promoting wound healing. However, most existing hydrogel dressings have an inadequacy in either mechanical performance, biological activities, or versatilities. Here we presented a double-network cross-linked polysaccharide-based hydrogel composed of collagen peptide-functionalized carboxymethyl chitosan (CS) and oxidized methacrylate sodium alginate (SA). The hydrogel possessed interconnected porous morphologies, suitable swelling ratios, excellent mechanical properties, and favorable biocompatibility. Meanwhile, the in vivo studies using a mouse full-thickness skin defect model showed that the double-network CS/SA hydrogel significantly accelerated wound healing by regulating the inflammatory process, promoting collagen deposition, and improving vascularization. Therefore, the functionalized double-network hydrogel should be a potential candidate as wound dressings.

A multifunctional shape-adaptive and biodegradable hydrogel with hemorrhage control and broad-spectrum antimicrobial activity for wound healing

Hemorrhage is the leading cause of preventable death of injured military and civilian patients, and subsequent infection risks endanger their lives or impede the healing of their wounds. Here, we report an injectable biodegradable hydrogel with hemostatic, antimicrobial, and healing-promoting properties. The hydrogel was prepared by dynamic cross-linking of a natural polysaccharide (dextran) with antimicrobial peptide ε-poly-l-lysine (EPL) and encapsulating base fibroblast growth factor (bFGF). The amino groups of EPL were allowed to react with the aldehyde of oxidized dextran (OD) through the Schiff-base reaction for the generation of hydrogels that have fast self-healing and injectable characteristics and adapt to the shapes of wounds. The prepared OD/EPL hydrogels promoted blood clotting in vitro and stopped bleeding in a rat liver injury model within 6 min through their platelet-aggregating ability and sealing effect. These hydrogels exhibited inherent antimicrobial effects without the use of antibiotics and effectively killed a broad spectrum of pathogenic microbes, including Gram-positive methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative Escherichia coli, and Pseudomonas aeruginosa and fungus Candida albicans in vitro. Moreover, these OD/EPL hydrogels were compatible with mammalian cells in vitro and in vivo and biodegradable in the mouse body. The loaded bFGF can be released sustainably, and it can promote angiogenesis, endothelial cell migration, and consequently accelerate the healing of wounds. The OD/EPL hydrogel inhibited MRSA infection in a rat full-thickness skin wound model and promoted healing. This kind of multifunctional hydrogel is a promising wound dressing for the emergency treatment of acute deep or penetrating injuries.

A reduced polydopamine nanoparticle-coupled sprayable PEG hydrogel adhesive with anti-infection activity for rapid wound sealing

There is a growing demand to develop sprayable hydrogel adhesives with rapid-forming and antibacterial abilities to instantly seal open wounds and combat pathogen infection. Herein, we propose to design a polydopamine nanoparticle (PDA NP) coupled PEG hydrogel that can quickly solidify via an amidation reaction after spraying as well as tightly binding PDA NPs to deliver reactive oxygen species (ROS) and induce a photothermal effect for bactericidal activity, and provide a hydrophilic surface for antifouling activity. The molecular structure of the 4-arm-PEG-NHS precursor was regulated to increase its reactivity with 4-arm-PEG-NH2, which thus shortened the gelation time of the PEG adhesive to 1 s to allow a fast solidification after being sprayed. The PEG-NHS precursor also provided covalent binding with tissue and PDA NPs. The reduced PDA NPs have redox activity to convey electrons to oxygen to generate ROS (H2O2), thus endowing the hydrogel with ROS dependent antibacterial ability. Moreover, NIR irradiation can accelerate the ROS release because of the photothermal effect of PDA NPs. In vitro tests demonstrated that H2O2 and the NIR-photothermal effect synergistically induced a fast bacterial killing, and an in vivo anti-infection test also proved the effectiveness of PEG-PDA. The sprayable PEG-PDA hydrogel adhesive, with rapid-forming performance and a dual bactericidal mechanism, may be promising for sealing large-scale and acute wound sites or invisible bleeding sites, and protect them from pathogen infection.

Polymeric Tissue Adhesives

Polymeric tissue adhesives provide versatile materials for wound management and are widely used in a variety of medical settings ranging from minor to life-threatening tissue injuries. Compared to the traditional methods of wound closure (i.e., suturing and stapling), they are relatively easy to use, enable rapid application, and introduce minimal tissue damage. Furthermore, they can act as hemostats to control bleeding and provide a tissue-healing environment at the wound site. Despite their numerous current applications, tissue adhesives still face several limitations and unresolved challenges (e.g., weak adhesion strength and poor mechanical properties) that limit their use, leaving ample room for future improvements. Successful development of next-generation adhesives will likely require a holistic understanding of the chemical and physical properties of the tissue-adhesive interface, fundamental mechanisms of tissue adhesion, and requirements for specific clinical applications. In this review, we discuss a set of rational guidelines for design of adhesives, recent progress in the field along with examples of commercially available adhesives and those under development, tissue-specific considerations, and finally potential functions for future adhesives. Advances in tissue adhesives will open new avenues for wound care and potentially provide potent therapeutics for various medical applications.

An injectable serotonin–chondroitin sulfate hydrogel for bio-inspired hemostatic adhesives with high wound healing capability

An injectable hydrogel inspired by platelet clotting mediators is developed based on natural components of the human body including serotonin and chondroitin sulfate, which exhibits improved hemostatic performance and wound healing capability.

Bioinspired Non-Immunogenic Multifunctional Sealant for Efficient Blood Clotting and Suture-Free Wound Closure

Engineering bioinspired peptide-based molecular medicine is an emerging paradigm for the management of traumatic coagulopathies and inherent bleeding disorder. A hemostat-based strategy in managing uncontrolled bleeding is limited due to the lack of adequate efficacy and clinical noncompliance. In this study, we report an engineered adhesive peptide-based hybrid regenerative medicine, sealant 5, which is designed integrating the structural and functional features of fibrin and mussel foot-pad protein. AFM studies have revealed that sealant 5 (55.8 ± 6.8 nN adhesive force) has higher adhesive force than fibrin (46.4 ± 7.3 nN adhesive force). SEM data confirms that sealant 5 retains its network-like morphology both at 37 and 60 °C, inferring its thermal stability. Both sealant 5 and fibrin exhibit biodegradability in the presence of trypsin, and sealant 5 also showed biocompatibility in the presence of fibroblast cells. Engineered sealant 5 efficiently promotes hemostasis with enhanced adhesiveness and less blood-loss than fibrin. In vivo data suggests that in heparinized conditions, sealant 5 ceases bleeding at 212.3 ± 15.1 s, whereas fibrin halts bleeding at 294.3 ± 21.4 s and blood-loss is ∼4-fold less in sealant 5 than in fibrin. In a heparinized system, sealant 5 facilitates faster blood-clotting than fibrin (∼82 s faster) and RADA-16, a reported peptide-based sealant (∼113 s faster). Additionally, in the case of sealant 5, the process of clotting mimicry-like fibrin is independent of the body's own coagulation system. Sealant 5 efficiently halts bleeding for both external and internal wounds, even for a heparinized system overcoming the bacterial infection. ELISA data and PMBC cell proliferation data support the non-immunogenic feature of sealant 5. Though fibrin and sealant 5 have exhibited comparable efficacy in suture-free wound closure, in vivo H&E staining images have revealed infiltration of very few immune cells as well as the presence of abundant collagen formation in the case of sealant 5-treated wound. Such nature-inspired non-immunogenic sealants offer exciting possibilities for the treatment of uncontrolled bleeding vis-à-vis wound closure.

In vitro and in vivo study of novel antimicrobial gellan-polylysine polyion complex fibers as suture materials

GELLAN GUM: and gellan-derived materials have never been used for suture materials due to their lack of strength and toughness. In this study, gellan and ε-polylysine formed a polyion complex in water solution, and the complex was transformed into fibers via wet-spinning. The fibers were bundled, twisted, and elongated, and the resultant twisted and elongated yarn (GPF) had a diameter of 97.53-103.76 μm and tensile strength of 4 N. The swelling ratio of GPF was 165.55%-183.23% in weight in normal saline, and the linear density was 2.84-3.31 g/km. GPF was tested using agar diffusion tests and it was found that the fibers had good antibacterial activity against Escherichia coli and Staphylococcus epidermidis. In weight loss experiments, GPF was found to be undegradable in normal saline and slightly degradable (residual weight ratio was 83.2 ± 1.2%) in simulated body fluid with trypsin within 7 days. Moreover, GPF showed no cytotoxicity toward BV-2 cells in cytotoxity tests with CCK8 and no hemolysis in hemolytic tests with fresh C57 mice blood. Finally, GPF was assessed using mouse dorsal cross-cutting model, and none of the mice that were tested with GPF showed infection or rejection reaction. Therefore, GPF is a promising suture material, and this study provides a new development direction for the application of gellan materials with improved mechanical properties.

Natural Polymer-Based Antimicrobial Hydrogels without Synthetic Antibiotics as Wound Dressings

Wound healing is usually accompanied by bacterial infection. The excessive use of synthetic antibiotics leads to drug resistance, posing a significant threat to human health. Hydrogel-based wound dressings aimed at mitigating bacterial infections have emerged as an effective wound treatment. The review presented herein particularly focuses on the hydrogels originating from natural polymers. To further enhance the performance of wound dressings, various strategies and approaches have been developed to endow the hydrogels with excellent broad-spectrum antibacterial activity. Those that are summarized in the current review are the hydrogels with intrinsic or stimuli-triggered bactericidal properties and others that serve as vehicles for loading antibacterial agents without synthetic antibiotics. Specific attention is paid to antimicrobial mechanisms and the antibacterial performance of hydrogels. Practical antibacterial applications to accelerate the wound healing employing these antibiotic-free hydrogels are also introduced along with the discussion on the current challenges and perspectives leading to new technologies.

Multifunctional Alginate Hydrogel Protects and Heals Skin Defects in Complex Clinical Situations

Skin defects, soft tissue damage, and fractures often occur simultaneously in severe trauma. Under current medical technology, fractures can be quickly fixed by internal or external repair techniques, and early functional exercises can be performed. However, skin defects heal over a long time and can even be difficult to heal. Functional exercise may cause cutting of fresh granulation to break and impair wound healing. Functional exercise and wound healing seem to contradict each other. In this study, an alginate hydrogel was developed. With self-healing characteristics, the hydrogel tightly adhered to the wound and could self-heal breaks in the gel caused by functional exercises. These characteristics enable this hydrogel to be used in complex clinical situations to solve sports rehabilitation and skin defect repair problems. In addition, this hydrogel can slowly release strontium ions, promote angiogenesis and collagen deposition in the wound, and quickly heal the wound.

Preparation of aminated fish scale collagen and oxidized sodium alginate hybrid hydrogel for enhanced full-thickness wound healing

Acute full-thickness wounds require a more extended healing period, thus increasing the risk of infection. Severe infection frequently resulted in wound ulceration, necrosis, and even life-threatening complications. Here, a hybrid hydrogel comprising aminated collagen (AC), oxidized sodium alginate (OSA), and antimicrobial peptides (polymyxin B sulfate and bacitracin) was developed to enhance full-thickness wound healing. The AC with low immunogenicity and high biocompatibility was made from marine fish scales, which are eco-friendly, low-cost, and sustainable. The cross-linked hydrogel was formed by a Schiff base reaction without any catalysts and additional procedures. As expected, the presented hybrid hydrogel can effectively against E. coli and S. aureus, as well as promote cell growth and angiogenesis in vitro. In addition, the hydrogel can promote full-thickness wound healing in a rat model through accelerating reepithelialization, collagen deposition, and angiogenesis. Our work demonstrated that the hybrid hydrogel has promising applications in the field of wound healing, which would prompt the utilization of marine fish resources during food processing.