Injectable antibacterial conductive nanocomposite cryogels with rapid shape recovery for noncompressible hemorrhage and wound healing

Engineering functional natural polymer-based nanocomposite hydrogels for wound healing

Skin injury occurs due to acute trauma, chronic trauma, infection, and surgical intervention, which can result in severe dysfunction and even death in humans. Therefore, clinical intervention is critical for the treatment of skin wounds. One idealized method is to use wound dressings to protect skin wounds and promote wound healing. Among these wound dressings, nanocomposite natural polymer hydrogels (NNPHs) are multifunctional wound dressings for wound healing. The combination of nanomaterials and natural polymer hydrogels avoids the shortcomings of a single component. Moreover, nanomaterials could provide improved antibacterial, anti-inflammatory, antioxidant, stimuli-responsive, electrically conductive and mechanical properties of hydrogels to accelerate wound healing. This review focuses on recent advancements in NNPHs for skin wound healing and repair. Initially, the functions and requirements of NNPHs as wound dressings were introduced. Second, the design, preparation and capacities of representative NNPHs are classified based on their nanomaterial. Third, skin wound repair applications of NNPHs have been summarized based on the types of wounds. Finally, the potential issues of NNPHs are discussed, and future research is proposed to prepare idealized multifunctional NNPHs for skin tissue regeneration.

Oxygen-releasing hydrogels promote burn healing under hypoxic conditions

Hypoxic nonhealing wounds are a common complication in chronic patients, and chronic hypoxia is the main reason for delayed wound healing, so local wound oxygenation may be an effective way to address this problem. Here, we proposed a system consisting of oxygen-releasing microsphere (GC) and self-healing hydrogel (QGO). QGO/GC hydrogel could promote survival, migration and tube formation of human umbilical vein endothelial cells under hypoxic conditions. Moreover, QGO/GC hydrogels exhibited biocompatibility in vitro and in vivo. The hypoxic mouse burn model further confirmed that QGO/GC hydrogel could promote tissue repair by reducing inflammation (TNF-α and IL-1β), increasing angiogenesis (CD31, VEGF and α-SMA) and collagen deposition. This study provided an effective oxygen-releasing hydrogel that could offer a simple and effective method for the clinical treatment of chronic hypoxic wounds. STATEMENT OF SIGNIFICANCE: Burn injury is caused by various exogenous factors such as friction, cold, radiations, electricity, chemicals, hot surfaces or liquids. Severe burn can damage the entire skin layer, and the healing process is delayed due to an unbalanced inflammatory response, excessive reactive oxygen species, lack of angiogenesis (insufficient nutrient and oxygen availability), and susceptibility to infection. In the present study, we proposed an oxygen-releasing hydrogel (QGO/GC). QGO/GC hydrogel could promote survival, migration, and tube formation of human umbilical vein endothelial cells under hypoxic conditions. And QGO/GC hydrogels could promote tissue repair by reducing inflammation, increasing angiogenesis and collagen deposition. This work provided an effective oxygen-releasing hydrogel for the clinical management of chronic hypoxic wounds.

Nanofibrous hemostatic materials: Structural design, fabrication methods, and hemostatic mechanisms

Development of rapid and effective hemostatic materials has always been the focus of research in the healthcare field. Nanofibrous materials which recapitulate the delicate nano-topography feature of fibrin fibers produced during natural hemostatic process, offer large length-to-diameter ratio and surface area, tunable porous structure, and precise control in architecture, showing great potential for staunching bleeding. Here we present a comprehensive review of advances in nanofibrous hemostatic materials, focusing on the following three important parts: structural design, fabrication methods, and hemostatic mechanisms. This review begins with an introduction to the physiological hemostatic mechanism and current commercial hemostatic agents. Then, it focuses on recent progress in electrospun nanofibrous hemostatic materials in terms of composition and structure control, surface modification, and in-situ deposition. The article emphasizes the development of three-dimensional (3D) electrospun nanofibrous materials and their emerging evolution for improving hemostatic function. Next, it discusses the fabrication of self-assembling peptide or protein-mimetic peptide nanofibers, co-assembling supramolecular nanofibers, as well as other nanofibrous hemostatic agents. Further, the article highlights the external and intracavitary hemostatic management based on various nanofiber aggregates. In the end, this review concludes with the current challenges and future perspectives of nanofibrous hemostatic materials. STATEMENT OF SIGNIFICANCE: This article reviews recent advances in nanofibrous hemostatic materials including fabrication methods, composition and structural control, performance improvement, and hemostatic mechanisms. A variety of methods including electrospinning, self-assembly, grinding and refining, template synthesis, and chemical vapor deposition, have been developed to prepare nanofibrous materials. These methods provide robustness in control of the nanofiber architecture in the forms of hydrogels, two-dimensional (2D) membranes, 3D sponges, or composites, showing promising potential in the external and intracavitary hemostasis and wound healing applications. This review will be of great interest to the broad readers in the field of hemostatic materials and multifunctional biomaterials.

4D prints of flexible dosage forms using thermoplastic polyurethane with hybrid shape memory effect

Thermoplastic polyurethanes are versatile materials due to their flexible and elastic properties. In research, medicine, and pharmacy, they are used in dosage forms, implants or as components of medical devices. To gain a deeper understanding of the influences on unfolding or expanding dosage forms, in this publication, 3D printing was used to produce differently shaped and foldable objects from various technical thermoplastic polyurethane filaments. The shape memory behaviour of the dosage forms was exploited to fold and package them in water-soluble hard gelatin capsules. The unfolding time and dimensional recovery of the 3D printed dosage forms were investigated as a function of material properties and shape. As an example, for the use of flexible dosage forms, 3D models have been designed so that their unfolded size is suitable for possible gastric retention. Depending on the shape and material, different unfolding behaviours could be shown. Over a storage period of 60 days, a time related stress on the 4D printed objects was evaluated, which possibly affects the unfolding process. The results of this work aim to be used to evaluate the behaviour of 3D printed unfolding and expanding dosage forms and how they may be suitable for the development of innovative sustained drug delivery concepts or medicinal devices. The basic principle of a hybrid shape memory effect used here could possibly be applied to other drug delivery strategies besides gastric retention.

Ultrathin, elastic, and self-adhesive nanofiber bio-tape: An intraoperative drug-loading module for ureteral stents with localized and controlled drug delivery properties for customized therapy

During the postoperative management of urinary diseases, oral or intravenous administration of drugs and implanting ureteral stents are usually required, making localized drug delivery by ureteral stent a precise and effective medication strategy. In the traditional drug loading method, the drug was premixed in the implants in production lines and the versatility of drugs was restricted. However, the complex situation in the urinary system fails the possibility of finding a “one fits all” medication plan, and the intraoperative drug-loading of implants is highly desired to support customized therapy. Here, we designed an ultrathin (8 μm), elastic, and self-adhesive nanofiber bio-tape (NFBT) that can easily encapsulate drugs on the stent surface for controllable localized drug delivery. The NFBT exhibited high binding strength to a ureteral stent, a sustained release over 7 d in PBS for hydrophilic drug, and a zero-order release curve over 28 days for the hydrophobic drug nitrofurantoin (NFT). Further in vivo experiments using a porcine ureteral tract infection model demonstrated that NFBT loaded with NFT could significantly reduce the bacterial concentration in urine. The total amount of NFT delivered by the NFBT was about 2.68 wt% of the recommended dose for the systemic administration.

•

An intra operation drug-loading strategy and drug carrier for personalized post-operation management of urinary disease.

•

The NFBT is ultrathin (∼8 μm) with enough binding stress to resist displacement bought by ureteral peristalsis.

•

In vivo antibacterial rate >99.9% for 28 d (porcine UTI model), with 2.68 wt% of the systemically administration dosage.

Influence of Cedar Essential Oil on Physical and Biological Properties of Hemostatic, Antibacterial, and Antioxidant Polyvinyl Alcohol/Cedar Oil/Kaolin Composite Hydrogels

Polyvinyl alcohol (PVA) is a safe and biodegradable polymer. Given the unique physical and chemical properties of PVA, we physically cross-linked PVA with kaolin (K) and cedar essential oil (Ced) using the freeze-thawing approach to fabricate PVA/Ced/K sponge hydrogels as hemostatic, antibacterial, and antioxidant wound healing materials. The physicochemical characteristics of PVA/Ced/K hydrogels, including water swelling profiles and gel fractions, were surveyed. Additionally, the functional groups of hydrogels were explored by Fourier transform infrared spectroscopy (FTIR), while their microstructures were studied using scanning electron microscopy (SEM). Furthermore, the thermal features of the hydrogels were probed by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Evidently, alterations in cedar concentrations resulted in significant variations in size, water uptake profiles, and hydrolytic degradation of the hydrogels. The incorporation of cedar into the PVA/K endowed the hydrogels with significantly improved antibacterial competency against Bacillus cereus (B. cereus) and Escherichia coli (E. coli). Moreover, PVA/Ced/K exhibited high scavenging capacities toward ABTS^•+ and DPPH free radicals. Beyond that, PVA/Ced/K hydrogels demonstrated hemocompatibility and fast blood clotting performance in addition to biocompatibility toward fibroblasts. These findings accentuate the prospective implementation of PVA/Ced/K composite hydrogel as a wound dressing.

Histidine-Triggered GO Hybrid Hydrogels for Microfluidic 3D Printing

Graphene oxide (GO) hydrogels have provided tremendous opportunities in designing and fabricating complex constructs for diverse applications, while their 3D printing without photocuring is still a challenging task due to their low viscosity, uncontrollable gelation, and low interfacial tension. Here, we report a histidine-assisted printing strategy to prepare GO hybrid hydrogels through the microfluidic 3D printing technique. We found that the GO additive could significantly hamper the Knoevenagel condensation (KC) reaction between benzaldehyde and cyanoacetate group-functionalized polymers to form a hydrogel, while these GO mixed solutions were rapidly solidified into a hydrogel when histidine was added. This fascinating phenomenon enabled us to prepare low-viscosity GO mixed polymer solutions as printable inks and generate hydrogel microfibers in histidine solutions. The hydrogel fibers could support cell survival and be further constructed into complex 3D structures through microfluidic 3D printing techniques. Moreover, due to the addition of GO, the microfibers exhibited excellent electrical conductivity and could sense the motion changes and convert these stimuli as electrical resistance signals. This strategy adds an option for the design and application of 3D printable aqueous GO inks in many fields.

Mussel-inspired polysaccharide-based sponges for hemostasis and bacteria infected wound healing

Effective bleeding control and wound protecting from infection play critical roles in the tissue healing process. However, local hemostats are not involved in the whole healing processes to promote the final healing efficiency. Here, a multi-functional mussel-inspired polysaccharide-based sponge with hemostatic, antibacterial and adhesive properties was fabricated via cryopolymerization of oxidized dextran (OD), carboxymethyl chitosan (CC) and polydopamine nanoparticles (PDA-NPs), followed by lyophilization. Combining with the adsorbed thrombin, the sponges yielded a considerably lower amount of blood than the commercially available hemostatic dressings. Benefiting from the high photo-thermal transition efficiency of PDA-NPs, the sponges exhibited excellent antibacterial activity to both gram positive and negative bacteria. Owing to the rapid hemostatic activity and effective infection resistance, the sponges illustrated the significantly acceleratory wound healing efficiency compared with the control group. The thrombin-loaded OD/CC-PDA polysaccharide-based sponge has great potential for future clinical use as wound dressing.

A Narrative Review of Different Hemostatic Materials in Emergency Treatment of Trauma

Hemostatic materials are very important for the treatment of a large number of bleeding trauma patients in battlefield and disaster environments. Different types of hemostatic materials need to be used for emergency hemostasis according to different injury parts and severity. At present, the first-aid hemostatic materials have been well applied to the bleeding of body surface wounds, limbs, and junctions, but there are still no ideal hemostatic materials in the early treatment of first aid for the deep and incompressible bleeding of thoracoabdominal cavity and visceral organs. This paper reviews the classification and mechanism of hemostatic materials, as well as the application and research progress in trauma emergency, so as to provide reference for the application of hemostatic materials in early first-aid emergency.

Multifunctional GO Hybrid Hydrogel Scaffolds for Wound Healing

Hydrogel dressings have received extensive attention for the skin wound repair, while it is still a challenge to develop a smart hydrogel for adapting the dynamic wound healing process. Herein, we develop a novel graphene oxide (GO) hybrid hydrogel scaffold with adjustable mechanical properties, controllable drug release, and antibacterial behavior for promoting wound healing. The scaffold was prepared by injecting benzaldehyde and cyanoacetate group-functionalized dextran solution containing GO into a collection pool of histidine. As the GO possesses obvious photothermal behavior, the hybrid hydrogel scaffold exhibited an obvious stiffness decrease and effectively promoted cargo release owing to the breaking of the thermosensitive C=C double bond at a high temperature under NIR light. In addition, NIR-assisted photothermal antibacterial performance of the scaffold could be also achieved with the local temperature rising after irradiation. Therefore, it is demonstrated that the GO hybrid hydrogel scaffold with vascular endothelial growth factor (VEGF) encapsulation can achieve the adjustable mechanical properties, photothermal antibacterial, and angiogenesis during the wound healing process. These features indicated that the proposed GO hybrid hydrogel scaffold is potentially valuable for promoting wound healing and other biomedical application.

Design of biopolymer-based hemostatic material: Starting from molecular structures and forms

Uncontrolled bleeding remains as a leading cause of death in surgical, traumatic, and emergency situations. Management of the hemorrhage and development of hemostatic materials are paramount for patient survival. Owing to their inherent biocompatibility, biodegradability and bioactivity, biopolymers such as polysaccharides and polypeptides have been extensively researched and become a focus for the development of next-generation hemostatic materials. The construction of novel hemostatic materials requires in-depth understanding of the physiological hemostatic process, fundamental hemostatic mechanisms, and the effects of material chemistry/physics. Herein, we have recapitulated the common hemostatic strategies and development status of biopolymer-based hemostatic materials. Furthermore, the hemostatic mechanisms of various molecular structures (components and chemical modifications) are summarized from a microscopic perspective, and the design based on them are introduced. From a macroscopic perspective, the design of various forms of hemostatic materials, e.g., powder, sponge, hydrogel and gauze, is summarized and compared, which may provide an enlightenment for the optimization of hemostat design. It has also highlighted current challenges to the development of biopolymer-based hemostatic materials and proposed future directions in chemistry design, advanced form and clinical application.

•

Biopolymers possess sound biocompatibility, biodegradability and bioactivity for the design of hemostatic materials.

•

Molecular structure designs including component and chemical modification are summarized from a microscopic perspective.

•

Design of various forms of hemostatic materials is discussed and compared synthetically from a macroscopic perspective.

Biocompatible and antibacterial Flammulina velutipes-based natural hybrid cryogel to treat noncompressible hemorrhages and skin defects

Hemorrhage, infection, and frequent replacement of dressings bring great clinical challenges to wound healing. In this work, Flammulina velutipes extract (FV) and hydroxyethyl cellulose (HEC) were chemically cross-linked and freeze-dried to obtain novel HFV cryogels (named HFVn, with n = 10, 40, or 70 corresponding to the weight percentage of the FV content), which were constructed for wound hemostasis and full-thickness skin defect repair. Systematic characterization experiments were performed to assess the morphology, mechanical properties, hydrophilic properties, and degradation rate of the cryogels. The results indicated that HFV70 showed a loose interconnected-porous structure and exhibited the highest porosity (95%) and water uptake ratio (over 2,500%) with a desirable degradation rate and shape memory properties. In vitro cell culture and hemocompatibility experiments indicated that HFV70 showed improved cytocompatibility and hemocompatibility. It can effectively mimic the extracellular matrix microenvironment and support the adhesion and proliferation of L929 cells, and its hemolysis rate in vitro was less than 5%. Moreover, HFV70 effectively induced tube formation in HUVEC cells in vitro. The results of the bacteriostatic annulus confirmed that HFV70 significantly inhibited the growth of Gram-negative E. coli and Gram-positive S. aureus. In addition, HFV70 showed ideal antioxidant properties, with the DPPH scavenging rate in vitro reaching 74.55%. In vivo rat liver hemostasis experiments confirmed that HFV70 showed rapid and effective hemostasis, with effects comparable to those of commercial gelatin sponges. Furthermore, when applied to the repair of full-thickness skin defects in a rat model, HFV70 significantly promoted tissue regeneration. Histological analysis further confirmed the improved pro-angiogenic and anti-inflammatory activity of HFV70 in vivo. Collectively, our results demonstrated the potential of HFV70 in the treatment of full-thickness skin defects and rapid hemostasis.

Bioactive inorganic particles-based biomaterials for skin tissue engineering

The challenge for treatment of severe cutaneous wound poses an urgent clinical need for the development of biomaterials to promote skin regeneration. In the past few decades, introduction of inorganic components into material system has become a promising strategy for improving performances of biomaterials in the process of tissue repair. In this review, we provide a current overview of the development of bioactive inorganic particles-based biomaterials used for skin tissue engineering. We highlight the three stages in the evolution of the bioactive inorganic biomaterials applied to wound management, including single inorganic materials, inorganic/organic composite materials, and inorganic particles-based cell-encapsulated living systems. At every stage, the primary types of bioactive inorganic biomaterials are described, followed by citation of the related representative studies completed in recent years. Then we offer a brief exposition of typical approaches to construct the composite material systems with incorporation of inorganic components for wound healing. Finally, the conclusions and future directions are suggested for the development of novel bioactive inorganic particles-based biomaterials in the field of skin regeneration.

Ultrastretchable, Self-Healable, and Tissue-Adhesive Hydrogel Dressings Involving Nanoscale Tannic Acid/Ferric Ion Complexes for Combating Bacterial Infection and Promoting Wound Healing

Preventing bacterial infections and accelerating wound closure are essential in the process of wound healing. Current wound dressings lack enough mechanical properties, self-healing ability, and tissue adhesiveness, and the bacterial killing also relies on the use of antibiotic drugs. Herein, a well-designed hybrid hydrogel dressing is constructed by simple copolymerization of acrylamide (AM), 3-acrylamido phenylboronic acid (AAPBA), chitosan (CS), and the nanoscale tannic acid (TA)/ferric ion (Fe³⁺) complex (TFe). The resulting hydrogel possesses lots of free catechol, phenylboronic acid, amine, and hydroxyl groups and contains many reversible and dynamic bonds such as multiple hydrogen bonds and boronate ester bonds, thereby showing satisfactory mechanical properties, fast self-healing ability, and desirable tissue-adhesive performance. Benefiting from the high photothermal conversion efficiency of the TFe, the hydrogel exhibits satisfactory antibacterial activity against both Gram-positive and Gram-negative bacteria. Moreover, the embedded TFe also endows the hydrogel with good antioxidant activity, anti-inflammatory property, and cell proliferation to promote tissue regeneration. Remarkably, in vivo animal assays reveal that the hybrid hydrogel effectively eliminates biofilm bacteria in the wound sites and accelerates the healing process of infected wounds. Taken together, the developed versatile hydrogels overcome the shortcomings of traditional wound dressings and are expected to become potential antibacterial dressings for future biomedical applications.

Water-Swellable Cellulose Nanofiber Aerogel for Control of Hemorrhage from Penetrating Wounds

Uncontrolled hemorrhage from wounds with deep and irregular cavities is short of efficient hemostats. Here we report a citric acid-cross-linked carboxymethyl cellulose nanofiber (CA-CMCNF) aerogel for the control of bleeding from penetrating wounds. The compressed CA-CMCNF aerogel could quickly swell into its original shape in water in seconds. The maximum mass and volume expansion ratios were over 6800 and 3000%, respectively. The water-swellable property allows the aerogel to self-expand and fill in the cavities of wounds. The in situ-generated expansion pressure resisted the systolic blood pressure, and the plentiful carboxyl groups triggered the active coagulation pathway, both contributing to the hemostatic capability of the aerogel. Additionally, the aerogel had good biocompatibility and excellent antibacterial capability. The animal experiments revealed that the aerogels significantly reduced both the hemostasis time and the amount of bleeding in a liver penetrating model. Therefore, this study provides a safe and robust hemostatic aerogel for controlling bleeding from penetrating wounds.

Antimicrobial cryogel dressings towards effective wound healing

Cryogels are macroporous hydrogels that have been widely utilized in a variety of biomedical applications including wound dressings. Cryogels reveal superior mechanical and swelling properties as well as large and interconnected porosity. As traditional hydrogel wound dressings generally show undesirable mechanical and swelling characteristics, cryogels, due to their toughness and superfast swelling, offer an outstanding platform to address the growing number of various types of wounds. Moreover, recently, cryogel wound dressings loaded with an antimicrobial agent emerged as a feasible option to reduce infection, and thus improve the wound healing process. However, a comprehensive review of antimicrobial cryogels as a wound dressing is still lacking in the literature. In this review, we summarize the progress of cryogels in the area of wound dressings and provide an overview of the various polymers, namely, natural and synthetic which have been employed in cryogel wound dressing preparation. Furthermore, the most prominent antimicrobial agents incorporated in cryogel wound dressings are provided. Finally, the future directions of cryogel wound dressings for wound healing are also discussed.

Preparation of methacrylated hyaluronate/methacrylated collagen sponges with rapid shape recovery and orderly channel for fast blood absorption as hemostatic dressing

Uncontrolled hemorrhage of deep, narrow, and non-compressible perforating wounds is responsible for many trauma deaths. In this study, a rapid hemostatic sponge with an orderly channel based on methacrylated collagen (ColMA) was prepared via directional freeze-drying technology. The methacrylated hyaluronate (HAMA) was added to further enhance the mechanical properties of the sponge. The sponge presents excellent mechanical strength, rapid shape recovery, and absorption speed, which was faster than those of many reported natural polymer hemostatic sponges. Moreover, ColMA/HAMA sponge showed much better blood-clotting capacity and superior hemostasis performance than commercially available collagen sponges in vitro and in the rat-liver injury model. This study demonstrated a feasible strategy to construct the rapid hemostatic sponge with an orderly channel for the deep and non-compressible perforating wound.

Production of Mesoglycan/PCL Based Composites through Supercritical Impregnation

The development of targeted therapies for wound repair is knowing a growing interest due to the increasing aging of the population and the incidence of chronic pathologies, mainly pressure ulcers. Among molecules recruiting cell populations and promoting the formation of new vital tissue, sodium mesoglycan (MSG) has been proven to be effective in wound healing. In this work, MSG impregnation of polymer matrices has been attempted by a supercritical carbon dioxide-based process. Polymeric matrices are composed of polycaprolactone blends, where water-soluble polymers, polyethylene glycol, polyvinyl pyrrolidone, gelatin, and thermoplastic starch, have been employed to modulate the MSG release, making the devices potentially suitable for topical administrations. Two different techniques have been used to obtain the films: the first one is compression molding, producing compact and continuous structures, and the second one is electrospinning, producing membrane-like designs. A higher amount of MSG can be loaded into the polymeric matrix in the membrane-like structures since, in these films, the impregnation process is faster than in the case of compression molded films, where the carbon dioxide has firstly diffused and then released the active molecule. The type of water-soluble polymer influences the drug release rate: the blend polycaprolactone-gelatin gives a prolonged release potentially suitable for topical administration.

Injectable Antibacterial Gelatin-Based Hydrogel Incorporated with Two-Dimensional Nanosheets for Multimodal Healing of Bacteria-Infected Wounds

The design and development of multifunctional injectable hydrogels with high photothermal antibacterial activity and shape adaptability to accelerate bacteria-infected wound healing is of critical importance in clinical applications. In this study, a hybrid hydrogel composed of gelatin, iron, and MnO2 nanosheets was prepared by multiple interactions, including coordinative and hydrogen bonding as well as electrostatic attraction. The introduced MnO2 and Fe components made the hydrogels photothermally and chemodynamically active, thereby endowing them with potent antibacterial capabilities against both Gram-negative and Gram-positive bacteria. Because of the Fenton activity of the hydrogels, they could produce abandoned oxygen, which is highly crucial in the healing process of wounds. They also showed good cytocompatibility and hemocompatibility as well as high hemostatic properties. Moreover, the injectable hydrogels could fill irregular wounds and significantly accelerate bacteria-infected wound healing through decreasing the inflammatory response and increasing blood vessels. These features indicated the promising potential of the multifunctional hydrogel for healing infected full-thickness wounds.

Generation of cost-effective MXene@polydopamine-decorated chitosan nanofibrous wound dressing for promoting wound healing

Herein, we designed and fabricated a MXene@polydopamine (MXene@PDA)-decorated chitosan non-woven fabric (M-CNF) hemostatic dressing with super hydrophilic properties for wound repair and regeneration. The M-CNF exhibit excellently wettability characteristics which can rapidly absorb water from blood. Moreover, M-CNF with 15 mg/mL MXene@PDA (M-CNF-15) show better antibacterial performance, excellent blood-clotting performance, better blood cell and platelet adhesion ability than CNF, displaying both active and passive hemostatic mechanisms to accelerate blood clotting in mouse-liver injury model. In addition, the M-CNF-15 also shows better wound healed performance than Tegaderm™ film in a full-thickness skin defect model, and further demonstrating that the MXene@PDA can promote fibrinogen reformation the at the initial phases of the wound healing process. Therefore, this strategy for designing and manufacturing of multi-functional M-CNF wound dressing will have great potential for active local hemostasis and wound repair and regeneration.

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.

Mussel-inspired nanocomposite hydrogel based on alginate and antimicrobial peptide for infected wound repair

Timely hemostasis, antibacterial activity, and good adhesion are essential for wound healing. Here, we report about a novel nanocomposite hydrogel with hemostatic, antibacterial, and adhesive properties constructed with a mussel-inspired strategy. Oxidized alginic acid, dopamine, and antimicrobial peptide ε-polylysine were used to prepare a nanocomposite (ODP), and then further cross-linked with acrylamide to fabricate a nanocomposite hydrogel (ODPA). ODPA hydrogel can adhere to the surface of bleeding organs and arrest bleeding within 30 s. It can also be stretched to 12 times its original length and withstand a compression strain of 40 %, and shows effective inhibition on gram-positive and gram-negative bacteria. Compared with commercial alginate sponge, ODPA hydrogel can accelerate the healing of infected full-thickness wound by reducing inflammation, promoting angiogenesis, and collagen deposition. Therefore, the nanocomposite hydrogel is expected to be a multifunctional dressing for promoting healing of infected wounds.

A 3D bioprinted decellularized extracellular matrix/gelatin/quaternized chitosan scaffold assembling with poly(ionic liquid)s for skin tissue engineering

Currently, a suitable bioink for 3D bioprinting and capable of mimicking the microenvironment of native skin and preventing bacterial infection remains a major challenge in skin tissue engineering. In this study, we prepared a tissue-specific extracellular matrix-based bioink, and dECM/Gel/QCS (dGQ) 3D scaffold assembling with poly(ionic liquid)s (PILs) (dGQP) was obtained by an extrusion 3D bioprinting technology and dynamic hydrogen bonding method. The morphologies, mechanical properties, porosity, hydrophilicity, biodegradation, hemostatic effect, antibacterial ability, and biocompatibility of the hybrid scaffolds were characterized and evaluated. Results showed that the rapid release (2 h) of PILs on the dGQP scaffold can quickly kill gram-negative (E. coli) and gram-positive (S. aureus) bacteria with almost 100 % antibacterial activity and maintained a stable sterile environment for a long time (7 d), which was superior to the dGQ scaffold. The hemostasis and hemolysis test showed that the dGQP scaffold had a good hemostatic effect and excellent hemocompatibility. In vitro cytocompatibility studies showed that although the cell growth on dGQP scaffold was slow in the early stage, the cells proliferated rapidly since day 4 and had high ECM secretion at day 7. Overall, this advanced dGQP scaffold has a considerable potential to be applied in skin tissue engineering.

Liquid-infused microstructured bioadhesives halt non-compressible hemorrhage

Non-compressible hemorrhage is an unmet clinical challenge that accounts for high mortality in trauma. Rapid pressurized blood flows under hemorrhage impair the function and integrity of hemostatic agents and the adhesion of bioadhesive sealants. Here, we report the design and performance of bioinspired microstructured bioadhesives, formed with a macroporous tough xerogel infused with functional liquids. The xerogel can rapidly absorb interfacial fluids such as whole blood and promote blood clotting, while the infused liquids facilitate interfacial bonding, sealing, and antibacterial function. Their synergy enables the bioadhesives to form tough adhesion on ex vivo human and porcine tissues and diverse engineered surfaces without the need for compression, as well as on-demand instant removal and storage stability. We demonstrate a significantly improved hemostatic efficacy and biocompatibility in rats and pigs compared to non-structured counterparts and commercial products. This work opens new avenues for the development of bioadhesives and hemostatic sealants.

Non‐compressible wounds are a major source of high mortality in trauma victims. Here the authors report on the creation of xerogels impregnated with liquid adhesives which can rapidly absorb fluids promoting blood clotting while forming adhesions to tissue and demonstrate the xerogel in ex vivo and in vivo models.

Bacterial Growth-Induced Tobramycin Smart Release Self-Healing Hydrogel for Pseudomonas aeruginosa-Infected Burn Wound Healing

Burns are a common health problem worldwide and are highly susceptible to bacterial infections that are difficult to handle with ordinary wound dressings. Therefore, burn wound repair is extremely challenging in clinical practice. Herein, a series of self-healing hydrogels (QCS/OD/TOB/PPY@PDA) with good electrical conductivity and antioxidant activity were prepared on the basis of quaternized chitosan (QCS), oxidized dextran (OD), tobramycin (TOB), and polydopamine-coated polypyrrole nanowires (PPY@PDA NWs). These Schiff base cross-links between the aminoglycoside antibiotic TOB and OD enable TOB to be slowly released and responsive to pH. Interestingly, the acidic substances during the bacteria growth process can induce the on-demand release of TOB, avoiding the abuse of antibiotics. The antibacterial results showed that the QCS/OD/TOB/PPY@PDA9 hydrogel could kill high concentrations of Pseudomonas aeruginosa (PA), Staphylococcus aureus, and Escherichia coli in a short time and showed a bactericidal effect for up to 11 days in an agar plate diffusion experiment, while showing good in vivo antibacterial activity. Excellent and long-lasting antibacterial properties make it suitable for severely infected wounds. Furthermore, the incorporation of PPY@PDA endowed the hydrogel with near-infrared (NIR) irradiation assisted bactericidal activity of drug-resistant bacteria, conductivity, and antioxidant activity. Most importantly, in the PA-infected burn wound model, the QCS/OD/TOB/PPY@PDA9 hydrogel more effectively controlled wound inflammation levels and promoted collagen deposition, vascular generation, and earlier wound closure compared to Tegaderm dressings. Therefore, the TOB smart release hydrogels with on-demand delivery are extremely advantageous for bacterial-infected burn wound healing.

Injectable conductive micro-cryogel as a muscle stem cell carrier improves myogenic proliferation, differentiation and in situ skeletal muscle regeneration

Volumetric muscle loss (VML) results in the impediment of skeletal muscle function, and there were still great challenges in cell delivery approach with the minimally invasive operation to repair muscle defects. To deliver cells to the VML defects site efficiently, the injectable conductive porous nanocomposite microcryogels based on gelatin (GT) and reduced graphene oxide (rGO) were designed and prepared. The microcryogels were loaded with myoblasts to form an injectable cell delivery system and show the ability to protect cells during injection. Conductive microcryogel with 4 mg/mL rGO (GT/rGO4) enhanced C2C12 cell proliferation and myogenic differentiation during 3D culture compared with pure gelatin microcryogel. In a mice VML model, injection of microcryogel loaded with muscle-derived stem cells into the injury site significantly improved the generation of new muscle fibers and blood vessels, and anti-inflammatory properties. The results show that injectable biodegradable conductive microcryogel can be used as myoblast cell carriers with the potential to maintain cell activity and deliver cells to defective sites, thereby in situ enhancing skeletal muscle regeneration. STATEMENT OF SIGNIFICANCE: Volumetric muscle loss overwhelms the regenerative capacity of skeletal muscle, which results in severe damage to muscle tissues. In the treatment of volumetric muscle loss, conductive niche and muscle stem cells are needed to alleviate excessive scar formation and inflammation to improve muscle regeneration. Injectable gelatin/reduced graphene oxide based nanocomposite microcryogel can enhance the differentiation of seeded muscle stem cells. The improved repair of volumetric muscle loss was achieved via reducing collagen deposition and inflammation in the injected region through the microcryogel cell-delivery therapy, suggesting great potential of the injectable microcryogel as a cell carrier in soft tissue repair.

High efficiency of in-situ cross-linking and acid triggered drug delivery by introducing tobramycin into injectable and biodegradable hydrogels

High efficiency of in-situ cross-linking and acid triggered drug delivery is realized by introducing tobramycin into the hydrogels. Injectable and biodegradable hydrogels are prepared through two steps: First generation of reactive aldehyde groups in the sodium alginate (A-Alg) and then introduction of antibiotic tobramycin as cross-linker. Due to the formation of dynamic Schiff base bonds between the amino groups in tobramycin and aldehyde groups in A-Alg, the gelation of hydrogels can be realized immediately. Thus, tobramycin acts well as the first role cross-linker and the hydrogels containing tobramycin can be injected into the wound during the treatment. In addition, the acid from the decomposition of organic compounds by the bacteria can break the cross-linking points previously formed by tobramycin in the hydrogels. Therefore, tobramycin can be released and act as the second role model drug to kill the bacteria. Because the hydrogels network is broken, the release of tobramycin is more efficient than the traditional drug delivery from hydrogels by diffusion. Based on these unique properties, the present hydrogels containing tobramycin exhibit a good injectable and biodegradable capability. In addition, due to the existence of the reversible acid-labile linkages in the hydrogels, the hydrogels containing tobramycin are also self-healing, which additionally is favorable for the application of wound dressing. More importantly, the antibacterial hydrogels also demonstrate good biocompatibility in vitro and significantly therapeutic effects on an infected mice model in vivo. Based on the above special properties, the hydrogels cross-linked by tobramycin indicate a new approach to prepare hydrogel dressings with low-cost, non-toxicity and good anti-bacterial performance in the treatment of infectious wounds.

Tough Wet Adhesion of Hydrogen-Bond-Based Hydrogel with On-Demand Debonding and Efficient Hemostasis

Hydrogels have been widely used in wet tissues. However, the insufficient adhesion of hydrogels for wound hemostasis remains a grand challenge. Herein, a facile yet effective strategy is developed to fabricate tough wet adhesion of hydrogen-bond-based hydrogel (PAAcVI hydrogel) using copolymerization of acrylic acid and 1-vinylimidazole in dimethyl sulfoxide followed by solvent exchange with water. The PAAcVI hydrogel shows equally robust adhesion (>400 J m^-2) to both wet and dry tissues. Moreover, the PAAcVI hydrogel also exhibits strong long-term stable adhesion underwater and in various wet environments. Meanwhile, the adhesion of PAAcVI hydrogel can be adjusted through Zn²⁺-ion-mediated on-demand debonding, which makes it easy to peel off from the tissue reducing pain during dressing removal and avoiding secondary injury. The PAAcVI hydrogel displays efficient hemostasis in the mice-tail docking model and mice-liver bleeding model. This hydrogen-bond-based hydrogel shows tough wet adhesion, and its adhesion is controllable, demonstrating its promising application in moisture-resistant adhesives, medical adhesives, and hemostatic materials.

Cellulose-Based Cryogel Microspheres with Nanoporous and Controllable Wrinkled Morphologies for Rapid Hemostasis

First-aid hemostatic agents for acute bleeding can save lives in emergency situations. However, rapid hemostasis remains challenging when uncontrolled hemorrhage occurs on lethal noncompressible and irregular wounds. Herein, cellulose-based cryogel microspheres with deliberately customized micromorphologies for ultrafast water transportation and diffusion, including the shark skin riblet-inspired wrinkled surface with low fluid drag and the hydrophilic nanoporous 3D networks, are developed to deal with the acute noncompressible bleeding within seconds. These cryogel microspheres can rapidly absorb a large amount of blood over 6 times their own weight in 10 s and form a robust barrier to seal a bleeding wound without applying pressure. Remarkably, massive bleeding from a cardiac penetrating hole is effectively stopped using the microspheres within 20 s and no blood leakage is observed after 30 min. Additionally, these microspheres could be readily removed without rebleeding and capillary thrombus, which is highly favorable to rapid hemostasis in emergency rescue.

Self-healing hydrogel based on polyphosphate-conjugated pectin with hemostatic property for wound healing applications

Self-healing hydrogels have important application in hemostasis and wound repairing. In this research, pectin based self-healing hydrogel was fabricated with conjugated polyphosphate for hemostatic and wound healing applications. The hydrogel formed without any stimulus and hydrogel kept its biocompatibility; at the same time, the hydrogel degraded completely by enzyme and in vivo. The polyphosphate conjugated hydrogel also showed self-healing property and sustained release performance with strong coagulation characteristic. More importantly, the in vivo experiment revealed that the polyphosphate conjugated hydrogel reduced the blood loss and hemostasis time in hemorrhage model; meanwhile, the hydrogel accelerated the wound repairing rate of the open wound by preventing bacterial invasion. Altogether, the PolyP conjugated hemostatic pectin-based hydrogel is a good candidate as wound dressing material applied in clinic or open wound repairing.

Hydrogel Combined with Phototherapy in Wound Healing

Wound healing is a complex biological process that involves tissue regeneration. Traditional wound dressings are dry, cannot provide a moist environment for wound healing, and do not have high antibacterial properties. Hydrogels, which are capable of retaining large amounts of water, can create a moist healing environment. Currently, phototherapies have exhibited a high potential for the treatment of bacterial infections. Therefore, combining hydrogels with phototherapy can adequately overcome the shortcomings of traditional wound treatment methods and show great potential for wound healing owing to their high efficiency, low irritation, and good antibacterial performance. In this review, the application of hydrogels combined with phototherapy in wound healing is summarized. First, the basic principles of photodynamic therapy and photothermal therapy are briefly introduced. In addition, the progress of the application of hydrogel combined with phototherapy in wound healing is systematically investigated. Finally, the challenges and prospects of combining hydrogel with phototherapy in wound healing are discussed.

Electrospun kaolin-loaded chitosan/PEO nanofibers for rapid hemostasis and accelerated wound healing

Development of chitosan-based hemostatic products and their application in wound healing has always been a research hotspot in the field of emergency treatment and biomedicine. In this study, the classic hemostatic chitosan and the most well-known inorganic hemostatic agent-kaolin were tried to combine to form a more excellent dressing. Together with the aid of non-toxic, harmless and good hydrophilic polyethylene oxide, chitosan/polyethylene oxide (PEO)/kaolin nanofiber membranes (CPKs) were prepared by electrospinning technology. Such membranes exhibited adjustable mechanical properties and good biocompatibility. Furthermore, a series of in vitro coagulation experiments proved that CPKs with 10 % ratio of kaolin (CPK10) has excellent hemostatic ability. Especially, in the whole blood coagulation time (WBCT) assay, the hemostatic time of CPK10 (43 ± 1.4 s) was significantly lower than that of chitosan/polyethylene oxide (CPK0) nanofiber membrane (61 ± 2.2 s) and QuikClot® Combat Gauze (55.7 ± 1.2 s). The further rat liver injury test reconfirmed that CPK10 can stop bleeding better and faster compared to other groups. In addition, CPKs could promote back wound healing in rats within 14 days without significant inflammatory response. This safe and effective hemostatic CPKs is expected to be a promising candidate hemostat in pre-hospital medical care.

Mussel-inspired multifunctional hydrogel dressing with hemostasis, hypoglycemic, photothermal antibacterial properties on diabetic wounds

To meticulously establish an efficient photothermal multifunctional hydrogel dressing is a prospective strategy for the treatment of diabetic chronic wounds. Herein, glucose oxidase (GOx) was added to polydopamine/acrylamide (PDA/AM) hydrogels to reduce hyperglycemia to a normal level (3.9-6.1 mmol L^-1) and enhance compressive properties (55 kPa) and adhesive properties (32.69 kPa), which are capable of hemostasis in the wound. Then, MnO₂ nanoparticles were encapsulated into a polydopamine/acrylamide (PDA/AM) hydrogel, endowing it with excellent antibacterial properties (E. coli and S. aureus were 97.87% and 99.99%) under the irradiation of 808 nm NIR; meanwhile, the biofilm was eliminated completely. Besides, O₂ was generated (18 mg mL^-1) by the decomposition of H₂O₂ under the catalysis of MnO₂, which could accelerate the formation of angiogenesis and promote the crawling and proliferation of cells. Furthermore, the diabetic wound in vivo treated with the PDA/AM/GOx/MnO₂ hydrogel had a less inflammatory response and faster healing speed, which was completely healed in 14 days. Therefore, the multifunctional hydrogels with the capability of high compressible, hemostasis, antibacterial, hyperglycemia manipulation, and O₂ generation, demonstrate promise in diabetic chronic wound dressing.

Injectable shape memory hydroxyethyl cellulose/soy protein isolate based composite sponge with antibacterial property for rapid noncompressible hemorrhage and prevention of wound infection

Uncontrollable hemorrhage and subsequent wound infection are severe threats to life, especially for the deep noncompressible massive bleeding. However, traditional hemostatic materials are ineffective for extreme bleeding and subsequent wound infection. Here, we prepared an injectable shape memory hydroxyethyl cellulose/soy protein isolate based composite sponge (EHSS) for rapid noncompressible hemorrhage and prevention of wound infection. The nano silver (AgNPs)-loaded shape memory sponge (EHP@Ag) was fabricated by mussel-inspired polydopamine coating EHSS sponge, then reducing and immobilizing AgNPs in situ. The EHP@Ag sponges showed rapid blood-triggered shape recovery speed, which is beneficial for administering noncompressible hemorrhage. The results of the hemostatic experiment in vivo demonstrated that EHP@Ag sponge exhibited a desirable hemostasis effect (hemostasis time: 22.75 ± 3.86 s, blood loss: 285.25 ± 24.93 mg) compared to the commercial gelatin sponge (hemostasis time: 49.25 ± 3.30 s, blood loss: 755.50 ± 24.45 mg). Meanwhile, the EHP@Ag sponge has an efficient antibacterial property. Furthermore, the antibacterial experiment in vivo showed that the EHP@Ag sponges could kill bacteria effectively and reduce the bacteria-induced inflammatory response. In summary, the shape memory sponges can quickly control bleeding and avoid bacterial infection, which shows great potential for clinical application as a multifunctional hemostatic agent.

Magnetic nanostructure and biomolecule synergistically promoted Suaeda-inspired self-healing hydrogel composite for seawater evaporation

Multifunctional hydrogels with excellent comprehensive performance are essential prerequisite for the implementation of effective water resources technology with high efficiency and low energy consumption. Inspired by the water purification and self-healing properties of natural plants, and based on the synergy of photothermal and biological effects, high photothermal Fe₃O₄ nanoparticles and natural polyhydroxy oligomeric proanthocyanidin (OPC) are introduced into a water-active polyvinyl alcohol (PVA) hydrogel. Two new bio-hydrogels of PVA/Fe₃O₄/graphite and PVA/OPC with self-healing and stretchable properties are proposed and designed. The obtained hydrogels exhibit reversible covalent cross-linked water-promoted healing (chemically) and photothermal melting/recrystallization healing (physically). The double-layered hydrogel composite demonstrates a dual response function (sunlight and near-infrared light), along with water purification properties. It is prepared through a water spray triggered self-healing process. The ultimate fracture strain of the photothermal layer and purification layer hydrogel was more than 1000% and 400% respectively after self-healing.After 48 h of hydrogel composite adsorption, the color of a methylene blue solution faded, and the absorption peak at 664 nm decreased. In addition, this research adopts a phased evaporation method to concentrate local energy and provide power for seawater evaporation. The evaporation efficiency of seawater induced by near-infrared (NIR) light was up to 3.15 kg m^-2 h^-1, whereas that under sunlight was 1.25 kg m^-2 h^-1. Selection of the evaporation excitation light source allowed control of the evaporation efficiency. The proposed technology is expected to be widely applicable to the staged evaporation of seawater as well as water purification.

Janus mucosal dressing with a tough and adhesive hydrogel based on synergistic effects of gelatin, polydopamine, and nano-clay

There are many problems and challenges related to the treatment of highly prevalent oral mucosal diseases and oral drug delivery because of a large amount of saliva present in the oral cavity, the accompanying oral movements, and unconscious swallowing in the mouth. Therefore, an ideal oral dressing should possess stable adhesion and superior tough strength in the oral cavity. However, this fundamental requirement greatly limits the use of synthetic adhesive dressings for oral dressings. Here, we developed a mussel-inspired Janus gelatin-polydopamine-nano-clay (GPC) hydrogel with controlled adhesion and toughness through the synergistic physical and chemical interaction of gelatin (Gel), nano-clay, and dopamine (DA). The hydrogel not only exhibits strong wet adhesion force (63 kPa) but also has high toughness (1026 ± 100 J m^-3). Interfacial adhesion of hydrogels is achieved by modulating the interaction of catechol groups of the hydrogel with specific functional groups (e.g., NH₂, SH, OH, and COOH) on the tissue surface. The matrix dissipation of the hydrogel is regulated by physical crosslinking of gelatin, chemical crosslinking of gelatin with polydopamine (Michael addition and Schiff base formation), and nano-clay-induced constraint of the molecular chain. In addition, the GPC hydrogel shows high cell affinity and favors cell adhesion and proliferation. The hydrogel's instant and strong mucoadhesive properties provide a long-lasting therapeutic effect of the drug, thereby enhancing the healing of oral ulcers. Therefore, mussel-inspired wet-adhesion Janus GPC hydrogels can be used as a platform for mucosal dressing and drug delivery systems. STATEMENT OF SIGNIFICANCE: It is a great challenge to treat oral mucosal diseases due to the large amount of saliva present in the oral cavity, the accompanying oral movements, unconscious swallowing, and flushing of drugs in the mouth. To overcome the significant limitations of clinical bioadhesives, such as weakness, toxicity, and poor usage, in the present study, we developed a simple method through the synergistic effects of gelatin, polydopamine, and nano-clay to prepare an optimal mucosal dressing (Janus GPC) that integrates Janus, adhesion, toughness, and drug release property. It fits effectively in the mouth, resists saliva flushing and oral movements, provides oral drug delivery, and reduces patient discomfort. The Janus GPC adhesive hydrogels have great commercial potential to support further the development of innovative therapies for oral mucosal diseases.

Biocompatible Hemostatic Sponge Exhibiting Broad-Spectrum Antibacterial Activity

Hemorrhage during accidents or surgery is a significant challenge that can contribute to mortality. This is further aggravated due to bacterial infections at the injured site. Therefore, rapid application of a hemostatic and antibacterial material is highly necessary as a pretreatment for patients' survival. Herein, we have developed a hemostatic sponge (Hemobac) through amide crosslinking of gelatin and an N-(2-hydroxy) propyl-3-trimethylammonium chitosan (HTCC)-silver chloride nanocomposite (QAm₁-Ag_0.1) to mitigate bacterial infections, while aiding hemostasis. This Hemobac sponge completely eradicated (∼4-5 log) a wide range of Gram-positive and Gram-negative bacteria encompassing various clinical isolates within 6 h. The antihemorrhagic ability of Hemobac was ascertained through SEM images, which exhibited the presence of agglomerated blood cells onto the sponge with a significantly low blood-clotting index value (∼23 ± 1). Notably, Hemobac reduced the blood loss by ∼70-80% in the liver puncture model and femoral vein injury model in mice, displaying its improved hemostatic ability over a marketed gelatin-based sponge. Negligible hemolytic activity (∼6%) and retained healthy morphology of mammalian cells were observed upon exposure to the Hemobac sponge. Minimal immune response was noticed at the Hemobac-treated wound in mice through histopathology analysis. Collectively, these findings indicate that this biocompatible Hemobac sponge can stop the bleeding instantaneously and combat bacterial infections.