Bioinspired Injectable Self-Healing Hydrogel Sealant with Fault-Tolerant and Repeated Thermo-Responsive Adhesion for Sutureless Post-Wound-Closure and Wound Healing

Polyphenol-mediated hyaluronic acid/tannic acid hydrogel with short gelation time and high adhesion strength for accelerating wound healing

Wound healing is a complex process involving a complicated interplay between numerous cell types and vascular systems. Hyaluronic acid (HA)-based hydrogel facilitates wound healing, and is involved in all processes. However, slow gelation speed and weak adhesion strength limit its ability to form a stable physical barrier quickly. Herein, we propose a HA-based composite hydrogel as the wound dressing based on oxidative coupling reaction. Tannic acid and dopamine-coated carbon particles (DCPs) containing abundant phenolic hydroxyl groups are incorporated into the HA-based hydrogel for increasing the number of crosslinking sites of oxidative coupling of the hydrogel and enhancing adhesion through the formation of covalent bonds and hydrogen bonds between hydrogel and wound sites. The composite hydrogel exhibits short gelation time (<6 s) and high adhesion strength (>8.1 kPa), which are superior to the references and commercial products of its kind. The in vitro experiments demonstrate that the hydrogel has low hemolytic reaction, negligible cytotoxicity, and the ability to promote fibroblast proliferation and migration. The in vivo full-thickness skin defect model experiments demonstrate that the hydrogel can accelerate wound healing under mild photothermal stimulation of DCPs by reducing inflammation, relieving tissue hypoxia, and promoting angiogenesis and epithelialization.

Assembly of polysaccharide-based polymer brush for supramolecular hydrogel dressing

Extracted from Platycodon grandiflorum, platycodon grandiflorum polysaccharides (PGPs) with diverse biological functions have been extensively employed for modification and fabrication of hydrogels for biomedical applications, such as wound dressings. However, since the lack of effective structural design, the reported polysaccharide-based hydrogel dressings are still suffered from structural failures and limited bio-functionality. Herein, we demonstrate a facile and general strategy to fabricate a supramolecular hydrogel composed of PGP-based polymer brush as building blocks combined with a Ca2+-mediated self-assembly process. The specific polymer brush with high branch functionality was achieved with polyacrylamide arms evenly grown on the PGP (grafting efficiency as high as 80 %) with series of chemical modifications. With above structural merits, the resulting hydrogel with densely crosslinked polymer brush featured enhanced mechanical strength as well as self-healing, and shear-thinning behaviors. Further biocompatible investigation indicated the as-prepared hydrogels with admirable performances in self-adhesion (adhesive strength of 16.7-79.5 kPa), a pH-responsive swelling ratio as high as 44 at pH 5.4, and pH-responsive degradation. They also showed antioxidant capacity by scavenging DPPH activity of nearly 80 % in 20 min, hemocompatibility, cell viability and cell migration. Impressively, the PGP-based polymer brush hydrogel served as a wound dressing revealed significant acceleration on wound closure.

Thermoresponsive On-Demand Adhesion and Detachment of a Polyurethane-Urea Bioadhesive

The development of bioadhesives with strong adhesion and on-demand adhesion-detachment behavior is still critically important and challenging for facilitating painless and damage-free removal in clinical applications. In this work, for the first time, we report the easy fabrication of novel polyurethane-urea (PUU)-based bioadhesives with thermoresponsive on-demand adhesion and detachment behavior. The PUU copolymer was synthesized by a simple copolymerization of low-molecular-weight, hydrophilic, and biocompatible poly(ethylene glycol), glyceryl monolaurate (GML, a special chain extender with a long side hydrophobic alkyl group), and isophorone diisocyanate (IPDI). Here, GML was expected to not only adjust the temperature-dependent adhesion behavior but also act as an internal plasticizer. By simple adjustment of the water content, the adhesion strength of the 15 wt % water-containing PUU film toward porcine skin is as high as 55 kPa with an adhesion energy of 128 J/m2 at 37 °C. The adhesion strength dramatically decreases to only 3 kPa at 10 °C, exhibiting switching efficiency as high as 0.95. Furthermore, the present PUU-based adhesive also shows good on-demand underwater adhesion and detachment with a cell viability close to 100%. We propose that biomaterial research fields, especially novel PUU/polyurethane (PU)-based functional materials and bioadhesives, could benefit from such a novel thermoresponsive copolymer with outstanding mechanical and functional performances and an easy synthesis and scaled-up process as described in this article.

Amino acid-crosslinked 4arm-PLGA Janus patch with anti-adhesive and anti-bacterial properties for hernia repair

Presently, the non-biodegradable polypropylene (PP) patches frequently used for hernia repair can cause fibrous tissue growth and adhesions. This study created a Janus Patch with anti-adhesion and antimicrobial properties to improve hernia repair while promoting tissue repair. The biologically active 4arm-PLGA-BLPD was initially synthesized through the modification of 4arm-PLGA with lysine, followed by the fabrication of a Janus patch using a layer-by-layer electrostatic spinning technique. This patch consisted of three layers: a repair layer composed of 4arm-PLGA-BLPD/PCL fiber membrane, a mechanical layer of 4arm-PLGA/PCL fiber membrane, and an antimicrobial layer of EMO-4arm-PLGA/PCL fiber membrane loaded with Emodin (EMO). The results showed that Janus patch exhibited notable tensile strength and elongation at break, enabling it to offer enhanced mechanical reinforcement for abdominal wall defects. In addition, it slowly releases lysine for repair and inhibits bacterial growth with EMO. In vivo experiments demonstrated that the patch effectively induced neovascularization, reduced collagen ac-cumulation, and stabilized the expression of relevant proteins through the up-regulation of MMP1 and MMP9. This facilitated successful repair of the abdominal wall defect model and prevented adhesions. In summary, the Janus patch offers both practical application and theoretical insight for hernia repair.

An injectable hydrogel based on sodium alginate and gelatin treats bacterial keratitis through multimodal antibacterial strategy

Bacterial keratitis is among the most prevalent causes of blindness. Currently, the abuse of antibiotics in clinical settings not only lacks bactericidal effects but also readily induces bacterial resistance, making the clinical treatment of bacterial keratitis a significant challenge. In this study, we present an injectable hydrogel (GS-PNH-FF@CuS/MnS) containing self-assembled diphenylalanine dipeptide (FF) and CuS/MnS nanocomposites (CuS/MnS NCs) that destroy bacterial cell walls through a synergistic combination of mild photothermal therapy (PTT), chemodynamic therapy (CDT), ion release chemotherapy, and self-assembled dipeptide contact, thereby eliminating Pseudomonas aeruginosa. Under 808 nm laser irradiation, the bactericidal efficiency of GS-PNH-FF@CuS/MnS hydrogel against P. aeruginosa in vitro reach up to 96.97 %. Furthermore, GS-PNH-FF@CuS/MnS hydrogel is applied topically to kill bacteria, reduce inflammation, and promote wound healing. Hematoxylin-eosin (H&E) staining, Masson staining, immunohistochemistry and immunofluorescence staining are used to evaluate the therapeutic effect on infected rabbit cornea models in vivo. The GS-PNH-FF@CuS/MnS demonstrate good biocompatibility with human corneal epithelial cells and exhibit no obvious eyes side effects. In conclusion, the GS-PNH-FF@CuS/MnS hydrogel in this study provides an effective and safe treatment strategy for bacterial keratitis through a multimodal approach.

Epidermal growth factor-loaded, dehydrated physical microgel-formed adhesive hydrogel enables integrated care of wet wounds

Integrated wound care, a sequential process of promoting wound hemostasis, sealing, and healing, is of great clinical significance. However, the wet environment of wounds poses formidable challenges for integrated care. Herein, we developed an epidermal growth factor (EGF)-loaded, dehydrated physical microgel (DPM)-formed adhesive hydrogel for the integrated care of wet wounds. The DPMs were designed using the rational combination of hygroscopicity and reversible crosslinking of physical hydrogels. Unlike regular bioadhesives, which consider interfacial water as a barrier to adhesion, DPMs utilize water to form desirable adhesive structures. The hygroscopicity allowed the DPMs to absorb interfacial water and subsequently, the interfacial adhesion was realized by the interactions between tissue and DPMs. The reversible crosslinks further enabled DPMs to integrate into hydrogels (DPM-Gels), thus achieving wet adhesion. Importantly, the water-absorbing gelation mode of DPMs enabled facile loading of biologically active EGF to promote wound healing. We demonstrated that the DPM-Gels possessed wet tissue adhesive performance, with about 40 times the wet adhesive strength of fibrin glue and about 4 times the burst pressure of human blood pressure. Upon application at the injury site, the EGF-loaded DPM-Gels sequentially promoted efficient wound hemostasis, stable sealing, and quick healing, achieving integrated care of wet wounds.

Preparation of antimicrobial peptides and their combination with hydrogels for wound healing applications

The problem of drug resistance caused by long-term use of antibiotics has been a concern for many years. As this problem worsens, there are various bacterial-induced infections that have a serious impact on human health. Currently, antimicrobial peptides are good alternatives to antibiotics, which have powerful antimicrobial activity and unique antimicrobial mechanisms. Developing bacterial resistance is not easy. In addition, how to reduce the production cost of antimicrobial peptides and improve the screening efficiency are the problems that must be solved for antimicrobial peptide application. In this study, we employed cell membrane chromatography linked with the one-bead-one-substance approach to screen and prepare the antimicrobial peptide (SALSP), which offers the benefits of fast synthetic screening and easy operation. Meanwhile, the antimicrobial peptide showed great antimicrobial activity and biocompatibility. We prepared a conjugated sodium alginate/gelatin hydrogel wound dressing incorporating antimicrobial peptides to promote wound healing. In conclusion, this research provides solutions for the development and application of antimicrobial peptides.

Smart theranostics for wound monitoring and therapy

To overcome the challenges of poor wound diagnosis and limited clinical efficacy of current wound management, wound dressing materials with the aim of monitoring various biomarkers vital to the wound healing process such as temperature, pH, glucose concentration, and reactive oxygen species (ROS) and improving the therapeutic outcomes have been developed. These innovative theranostic dressings are smartly engineered using stimuli-responsive biomaterials to monitor and regulate local microenvironments and deliver cargos to the wound sites in a timely and effective manner. This review provides an overview of recent advances in novel theranostics for wound monitoring and therapy as well as giving insights into the future treatment of wounds via smart design of theranostic materials.

Novel Biomaterials for Wound Healing and Tissue Regeneration

Skin is the first defense barrier of the human body, which can resist the invasion of external dust, microorganisms and other pollutants, and ensure that the human body maintains the homeostasis of the internal environment. Once the skin is damaged, the health threat to the human body will increase. Wound repair and the human internal environment are a dynamic process. How to effectively accelerate the healing of wounds without affecting the internal environment of the human body and guarantee that the repaired tissue retains its original function as much as possible has become a research hotspot. With the advancement of technology, researchers have combined new technologies to develop and prepare various types of materials for wound healing. This article will introduce the wound repair materials developed and prepared in recent years from three types: nanofibers, composite hydrogels, and other new materials. The paper aims to provide reference for researchers in related fields to develop and prepare multifunctional materials. This may be helpful to design more ideal materials for clinical application, and then achieve better wound healing and regeneration effects.

Bio-gel nanoarchitectonics in tissue engineering

Given the creation of materials based on nanoscale science, nanotechnology must be combined with other disciplines. This role is played by the new concept of nanoarchitectonics, the process of constructing functional materials from nanocomponents. Nanoarchitectonics may be highly compatible with applications in biological systems. Conversely, it would be meaningful to consider nanoarchitectonics research oriented toward biological applications with a focus on materials systems. Perhaps, hydrogels are promising as a model medium to realize nanoarchitectonics in biofunctional materials science. In this review, we will provide an overview of some of the defined targets, especially for tissue engineering. Specifically, we will discuss (i) hydrogel bio-inks for 3D bioprinting, (ii) dynamic hydrogels as an artificial extracellular matrix (ECM), and (iii) topographical hydrogels for tissue organization. Based on these backgrounds and conceptual evolution, the construction strategies and functions of bio-gel nanoarchitectonics in medical applications and tissue engineering will be discussed.

Injectable Biomimetic Gels for Biomedical Applications

Biomimetic gels are synthetic materials designed to mimic the properties and functions of natural biological systems, such as tissues and cellular environments. This manuscript explores the advancements and future directions of injectable biomimetic gels in biomedical applications and highlights the significant potential of hydrogels in wound healing, tissue regeneration, and controlled drug delivery due to their enhanced biocompatibility, multifunctionality, and mechanical properties. Despite these advancements, challenges such as mechanical resilience, controlled degradation rates, and scalable manufacturing remain. This manuscript discusses ongoing research to optimize these properties, develop cost-effective production techniques, and integrate emerging technologies like 3D bioprinting and nanotechnology. Addressing these challenges through collaborative efforts is essential for unlocking the full potential of injectable biomimetic gels in tissue engineering and regenerative medicine.

Self-Healing Dynamic Hydrogel Microparticles with Structural Color for Wound Management

Chronic diabetic wounds confront a significant medical challenge because of increasing prevalence and difficult-healing circumstances. It is vital to develop multifunctional hydrogel dressings, with well-designed morphology and structure to enhance flexibility and effectiveness in wound management. To achieve these, we propose a self-healing hydrogel dressing based on structural color microspheres for wound management. The microsphere comprised a photothermal-responsive inverse opal framework, which was constructed by hyaluronic acid methacryloyl, silk fibroin methacryloyl and black phosphorus quantum dots (BPQDs), and was further re-filled with a dynamic hydrogel. The dynamic hydrogel filler was formed by Knoevenagel condensation reaction between cyanoacetate and benzaldehyde-functionalized dextran (DEX-CA and DEX-BA). Notably, the composite microspheres can be applied arbitrarily, and they can adhere together upon near-infrared irradiation by leveraging the BPQDs-mediated photothermal effect and the thermoreversible stiffness change of dynamic hydrogel. Additionally, eumenitin and vascular endothelial growth factor were co-loaded in the microspheres and their release behavior can be regulated by the same mechanism. Moreover, effective monitoring of the drug release process can be achieved through visual color variations. The microsphere system has demonstrated desired capabilities of controllable drug release and efficient wound management. These characteristics suggest broad prospects for the proposed composite microspheres in clinical applications.

Nature-Inspired Gelatin-Based Adhesive Hydrogel: A Rapid and User-Friendly Solution for Hemostatic Applications

Conventional hemostatic agents face challenges in achieving rapid hemostasis and effective tissue repair due to limited hemostatic scenarios, suboptimal efficacy, and inadequate adhesion to wet tissues. Drawing inspiration from nature-sourced materials, a gelatin-based adhesive hydrogel (AOT)  is designed, easily prepared and quick to form, driven by Schiff base and multiple hydrogen bonds for applications in arterial and liver bleeding models. AOT exhibits exceptional adhesion to wet tissues (48.67 ± 0.16 kPa) and displays superior hemostatic properties with reduced blood loss and hemostatic time compared to other hydrogels and conventional hemostatic materials. Moreover, AOT exhibits good biocompatibility and biodegradability. In summary, this easily prepared adhesive hydrogel has the potential to supplant traditional hemostatic agents, offering a novel approach to achieve swift sealing of hemostasis and facilitate wound healing and repair in broader application scenarios, owing to its unique advantages.

Ultrastable and supersensitive conductive hydrogels conferred by "sodium alginate stencil" anchoring strategy

Although conductive hydrogels have been widely developed currently, their low sensitivity and poor stability severely limited their practical application in flexible wearable devices. Herein, a green "stencil" anchoring strategy was proposed in this study to engineer an ultra-stable and supersensitive hydrogel by virtue of polydopamine decorating sodium alginate molecular chains as "stencil" to anchor polyaniline as conductive component. The dispersion of polyaniline was significantly improved by the sodium alginate "stencil" in the conductive hydrogel. The developed conductive hydrogel exhibited outstanding properties that outperformed most conventional ones, including extraordinary sensitivity with a gauge factor of 38.2 and excellent stability with negligible shifting upon long-term cyclic stretching. Moreover, the conductive hydrogel displayed great self-adhesion and reliable self-healing performance endowed by its abundant catechol groups, hydrogen bondings and π-π stackings, respectively. Furthermore, the prepared hydrogel was also assembled as flexible strain and self-powered sensors, which displayed excellent sensing performance, indicating great potential in human-machine interactions, information transmission and road transportation.

Scalable and Versatile Metal Ion Solidificated Alginate Hydrogel for Skin Wound Infection Therapy

Bacterial infections in wounds continue to be a major challenge in clinical settings worldwide and represent a significant threat to human health. This work proposes novel expandable and versatile methods for solidifying sodium alginate (SA) with metal ions (such as Fe3+, Co2+, Ni2+, Cu2+, and Zn2+) to create Metal-Alginate (M-Alg) hydrogel with adjustable morphology, composition, and microstructure. It conforms to the wound site, protects against second infection, reduces inflammation, and promotes the healing of infected wounds. Among these hydrogels, Cu-Alginate (Cu-Alg) shows excellent sterilization effect and good efficacy against both gram-positive and gram-negative bacteria, including multidrug-resistant (MDR) strains such as Methicillin-resistant Staphylococcus aureus (MRSA) and Carbapenem-resistant Klebsiella pneumoniae (CRKP) due to its dual antibacterial mechanisms: contact-killing and reactive oxygen species (ROS) burst. Importantly, it exhibits low cytotoxicity and biodegradability. This simple and cost-effective gel-based system has the potential to introduce an innovative approach to the management of wound infection and offers promising new perspectives for the advancement of wound care practice.

Microgels for Cell Delivery in Tissue Engineering and Regenerative Medicine

Microgels prepared from natural or synthetic hydrogel materials have aroused extensive attention as multifunctional cells or drug carriers, that are promising for tissue engineering and regenerative medicine. Microgels can also be aggregated into microporous scaffolds, promoting cell infiltration and proliferation for tissue repair. This review gives an overview of recent developments in the fabrication techniques and applications of microgels. A series of conventional and novel strategies including emulsification, microfluidic, lithography, electrospray, centrifugation, gas-shearing, three-dimensional bioprinting, etc. are discussed in depth. The characteristics and applications of microgels and microgel-based scaffolds for cell culture and delivery are elaborated with an emphasis on the advantages of these carriers in cell therapy. Additionally, we expound on the ongoing and foreseeable applications and current limitations of microgels and their aggregate in the field of biomedical engineering. Through stimulating innovative ideas, the present review paves new avenues for expanding the application of microgels in cell delivery techniques.

Bioinspired wet adhesive carboxymethyl cellulose-based hydrogel with rapid shape adaptability and antioxidant activity for diabetic wound repair

Currently, adhesive hydrogels have shown promising effect in chronic diabetic wound repair. However, there are issues and challenges in treating diabetic wounds due to inadequate wet adhesion, unable to fill irregular and deep wounds, and oxidative stress. Herein, a mussel-inspired naturally hydrogel dressing with rapid shape adaptability, wet adhesion and antioxidant abilities for irregular, deep and frequently movement diabetic wounds repair was constructed by comprising catechol modified carboxymethyl cellulose (CMC-DA) and tannic acid. Benefiting from the reversible hydrogen bonding, the resulting hydrogels exhibited injectability, remarkable self-healing ability, rapid shape adaptability and strong tissue adhesion (45.9 kPa), thereby contributing to self-adaptive irregular-shaped wounds or moving joint parts. Especially, the adhesion strength of the hydrogel on wet tissue still remained at 14.9 kPa. Besides, the hydrogels could be easily detached from the skin by ice-cooling that avoided secondary damage caused by dressing change. Remarkably, the hydrogels possessed excellent antioxidant, satisfactory biocompatibility, efficient hemostasis and antibacterial properties. The in vivo evaluation further demonstrated that the hydrogel possessed considerable wound-healing promotion effect by regulating diabetic microenvironment, attributed to that the hydrogel could significantly reduce inflammatory response, alleviate oxidative stress and regulate neovascularization. Overall, this biosafe adhesive hydrogel had great potentials for diabetic wound management.

A thermally reversible injectable adhesive for intestinal tissue repair and anti-postoperative adhesion

Intestine damage is an acute abdominal disease that usually requires emergency sealing. However, traditional surgical suture not only causes secondary damage to the injured tissue, but also results in adhesion with other tissues in the abdominal cavity. To this end, a thermally reversible injectable gelatin-based hydrogel adhesive (GTPC) is constructed by introducing transglutaminase (TGase) and proanthocyanidins (PCs) into a gelatin system. By reducing the catalytic activity of TGase, the density of covalent and hydrogen bond crosslinking in the hydrogel can be regulated to tune the sol-gel transition temperature of gelatin-based hydrogels above the physiological temperature (42 °C) without introducing any synthetic small molecules. The GTPC hydrogel exhibits good tissue adhesion, antioxidant, and antibacterial properties, which can effectively seal damaged intestinal tissues and regulate the microenvironment of the damaged site, promoting tissue repair and regeneration. Intriguingly, temperature-induced hydrogen bond disruption and reformation confer the hydrogel with asymmetric adhesion properties, preventing tissue adhesion when applied in vivo. Animal experiment outcomes reveal that the GTPC hydrogel can seal the damaged intestinal tissue firmly, accelerate tissue healing, and efficiently prevent postoperative adhesion.

A peptide-based pH-sensitive antibacterial hydrogel for healing drug-resistant biofilm-infected diabetic wounds

Diabetic foot ulcers are a significant complication affecting roughly 15% of diabetic patients. These chronic wounds can be incredibly burdensome, leading to high treatment costs, potential amputations, and additional health complications. Microbiological studies reveal that bacterial infections are the primary culprit behind delayed wound healing. To solve the problem of infection at the wound site, the most fundamental thing is to kill the pathogenic bacteria. Herein, a neoteric strategy to construct novel antibacterial hydrogel COA-T3 that combined photosensitizers (PSs) and antimicrobial peptides (AMPs) via covalent coupling was proposed. Hydrogel COA-T3 composed of quaternized chitosan (QCS) and oxidized dextran (OD) was constructed for co-delivery of the photosensitizer TPI-PN and the antimicrobial peptide HHC10. In vitro and in vivo experiments demonstrated remarkable effectiveness of COA-T3 against drug-resistant bacteria. Furthermore, the hydrogel significantly promoted healing of diabetic infected wounds. This enhanced antibacterial activity is attributed to the pH-sensitive release of both PSs and AMPs within the hydrogel. Additionally, COA-T3 exhibits excellent biocompatibility, making it a promising candidate for wound dressing materials. These findings indicated that the COA-T3 hydrogel is a promising wound dressing material for promoting the healing of diabetic foot ulcers by providing an environment conducive to improved wound healing in diabetic patients.

Sprayable Hydrogel Sealant for Gastrointestinal Wound Shielding

Naturally occurring internal bleeding, such as in stomach ulcers, and complications following interventions, such as polyp resection post-colonoscopy, may result in delayed (5-7 days) post-operative adverse events-such as bleeding, intestinal wall perforation, and leakage. Current solutions for controlling intra- and post-procedural complications are limited in effectiveness. Hemostatic powders only provide a temporary solution due to their short-term adhesion to GI mucosal tissues (less than 48 h). In this study, a sprayable adhesive hydrogel for facile application and sustained adhesion to GI lesions is developed using clinically available endoscopes. Upon spraying, the biomaterial (based on polyethyleneimine-modified Pluronic micelles precursor and oxidized dextran) instantly gels upon contact with the tissue, forming an adhesive shield. In vitro and in vivo studies in guinea pigs, rabbits, and pig models confirm the safety and efficacy of this biomaterial in colonic and acidic stomach lesions. The authors' findings highlight that this family of hydrogels ensures prolonged tissue protection (3-7 days), facilitates wound healing, and minimizes the risk of delayed complications. Overall, this technology offers a readily adoptable approach for gastrointestinal wound management.

Dehydration-Toughing Dual-Solvent Gels with Viscoelastic Transition for Infectious Wound Treatment

The modulus of traditional biomedical hydrogels increases exponentially meditated by dehydration-stiffing mechanism, which leads to the failure of interface matching between hydrogels and soft tissue wounds. It is found in the study that the dual-solvent gels exhibit dehydration-toughening mechanism with the slowly increasing modulus that are always match the soft tissue wounds. Therefore, dual-solvent glycerol hydrogels (GCFen-gly DGHs) are prepared with hydrophobically modified catechol chitosan (hmCSC) and gelatin based on the supramolecular interactions. GCFen-gly DGHs exhibit excellent water retention capacity with a total solvent content exceeding 80%, permanent skin-like modulus within a range of 0.45 to 4.13 kPa, and stable photothermal antibacterial abilities against S, aureus, E. coli, as well as MRSA. Infectious full-thickness rat skin defect model and tissue section analysis indicate that GCFen-gly DGHs are able to accelerate infectious wound healing by alleviating the inflammatory response, promoting granulation tissue growth, re-epithelialization, collagen deposition, and vascular regeneration. As a result, GCFen-gly DGHs is expected to become the next-generation biological gel materials for infectious wound treatment.

NIR-Responsive injectable hydrogel cross-linked by homobifunctional PEG for photo-hyperthermia of melanoma, antibacterial wound healing, and preventing post-operative adhesion

Current therapeutic approaches for skin cancer face significant challenges, including wound infection, delayed skin regeneration, and tumor recurrence. To overcome these challenges, an injectable adhesive near-infrared (NIR)-responsive hydrogel with time-dependent enhancement in viscosity is developed for combined melanoma therapy and antibacterial wound healing acceleration. The multifunctional hydrogel is prepared through the chemical crosslinking between poly(methyl vinyl ether-alt-maleic acid) and gelatin, followed by the incorporation of CuO nanosheets and allantoin. The synergistic inherent antibacterial potential of CuO nanosheets, the regenerative and smoothing effect of allantoin, the extracellular matrix-mimicking effect of gelatin, and the desirable swelling behavior of the hydrogel results in fast wound recovery after photothermal ablation of the tumor. Additionally, the hydrogel can serve as an alternative to sutures owing to its tissue adhesiveness ability, which can further render it the merits for accelerated repair of abdominal lesions while acting as a biocompatible barrier to prevent peritoneal adhesion.

Reversibly Adhesive, Anti-Swelling, and Antibacterial Hydrogels for Tooth-Extraction Wound Healing

Oral wound treatment faces challenges due to the complex oral environment, thus, sealing the wound quickly becomes necessary. Although some materials have achieved adhesion and sterilization, how to effectively solve the contradiction between strong adhesion and on-demand removal remains a challenge. Herein, a reversibly adhesive hydrogel is designed by free radical copolymerization of cationic monomer [2-(acryloyloxy) ethyl] trimethylammonium chloride (ATAC), hydrophobic monomer ethylene glycol phenyl ether acrylate (PEA) and N-isopropylacrylamide (NIPAAm). The cationic quaternary ammonium salts provide electrostatic interactions, the hydrophobic groups provide hydrophobic interactions, and the PNIPAAm chain segments provide hydrogen bonding, leading to strong adhesion. Therefore, the hydrogel obtains an adhesion strength of 18.67 KPa to oral mucosa and can seal wounds fast within 10 s. Furthermore, unlike pure PNIPAAm, the hydrogel has a lower critical solution temperature of 40.3 °C due to the contribution of ATAC and PEA, enabling rapid removal with 40 °C water after treatment. In addition, the hydrogel realizes excellent anti-swelling ratio (≈80%) and antibacterial efficiency (over 90%). Animal experiments prove that the hydrogel effectively reduces inflammation infiltration, promotes collagen deposition and vascular regeneration. Thus, hydrogel as a multi-functional dressing has great application prospects in oral wound management.

Expansion-clotting chitosan fabrics based on unidirectional fast-absorption fibers for rapid hemorrhage control

The rapid absorption of water from the blood to concentrate erythrocytes and platelets, thus triggering quick closure, is important for hemostasis. Herein, expansion-clotting chitosan fabrics are designed and fabricated by ring spinning of polylactic acid (PLA) filaments as the core layer and highly hydrophilic carboxyethyl chitosan (CECS) fibers as the sheath layer, and subsequent knitting of obtained PLA@CECS core spun yarns. Due to the unidirectional fast-absorption capacity of CECS fibers, the chitosan fabrics can achieve erythrocytes and platelets aggregate quickly by concentrating blood, thus promoting the formation of blood clots. Furthermore, the loop structure of coils formed in the knitted fabric can help them to expand by absorbing water to close their pores, providing effective sealing for bleeding. Besides, They have enough mechanical properties, anti-penetrating ability, and good tissue-adhesion ability in wet conditions, which can form a physical barrier to resist blood pressure during hemostasis and prevent them from falling off the wound, thus enhancing hemostasis synergistically. Therefore, the fabrics exhibit superior hemostatic performance in the rabbit liver, spleen, and femoral artery puncture injury model compared to the gauze group. This chitosan fabric is a promising hemostatic material for hemorrhage control.

Gelatin-based biomaterials and gelatin as an additive for chronic wound repair

Disturbing or disrupting the regular healing process of a skin wound may result in its progression to a chronic state. Chronic wounds often lead to increased infection because of their long healing time, malnutrition, and insufficient oxygen flow, subsequently affecting wound progression. Gelatin-the main structure of natural collagen-is widely used in biomedical fields because of its low cost, wide availability, biocompatibility, and degradability. However, gelatin may exhibit diverse tailored physical properties and poor antibacterial activity. Research on gelatin-based biomaterials has identified the challenges of improving gelatin's poor antibacterial properties and low mechanical properties. In chronic wounds, gelatin-based biomaterials can promote wound hemostasis, enhance peri-wound antibacterial and anti-inflammatory properties, and promote vascular and epithelial cell regeneration. In this article, we first introduce the natural process of wound healing. Second, we present the role of gelatin-based biomaterials and gelatin as an additive in wound healing. Finally, we present the future implications of gelatin-based biomaterials.

Injectable-Hydrogel-Based Tissue Sealant for Hemostasis, Bacteria Inhibition, and Pro-Angiogenesis in Organ Bleeding Wounds and Therapeutic Outcome Monitoring Via NIR-II Optical Imaging

Sudden hemorrhage stemming from internal organ wounds poses a grave and potentially fatal risk if left untreated. Injectable-hydrogel-based tissue sealants featuring multiple actions, including fit-to-shape in situ gelation, rapid hemostasis, pro-angiogenic, anti-bacterial and outcome tracking, are ideal for the management of organ trauma wounds. Herein, an injectable-hydrogel tissue sealant AN@CD-PEG&TQ which consists of four-arm 4-arm poly(ethylene glycol) (PEG-SC) succinimidyl carbonate), AN@CD nanoprobe, and two bioactive peptides (anti-microbial peptide Tet213 and pro-angiogenic peptide QK) is developed. Among them, AN@CD nanoparticles form through host/guest complexation of amino-group-containing β-cyclodextrin and adamantyl group, enabling in situ biomarker (NO)-activatable optoacoustic/NIR-II: Near-infrared second biological window fluorescent imaging. The ample ─NH2 groups on the surface of AN@CD readily engage in rapid cross-linking with succinimidyl ester groups located at the ends of four-arm PEG-SC. This cross-linking expedites the gelation process without necessitating additional initiators or cross-linking agents; thus, significantly enhancing both hydrogel's application convenience and biocompatibility. Bioactive peptides (Tet213 and QK) safeguard against possible bacterial infections, facilitate angiogenesis, and eventually, improve organ wounds healing. This hydrogel-based tissue sealant demonstrates superior therapeutic and bioimaging performance in various mouse models including liver hemorrhage, gastric perforation, and bacterial-infected skin wound mouse models, highlighting its potential as a high-performance wound sealant for organ bleeding wound management.

Tough, self-healing and injectable dynamic nanocomposite hydrogel based on gelatin and sodium alginate

Biomacromolecules based injectable and self-healing hydrogels possessing high mechanical properties have widespread potential in biomedical field. However, dynamic features are usually inversely proportional to toughness. It is challenging to simultaneously endow these properties to the dynamic hydrogels. Here, we fabricated an injectable nanocomposite hydrogel (CS-NPs@OSA-l-Gtn) stimultaneously possessing excellent autonomous self-healing performance and high mechanical strength by doping chitosan nanoparticles (CS-NPs) into dynamic polymer networks of oxidized sodium alginate (OSA) and gelatin (Gtn) in the presence of borax. The synergistic effect of the multiple reversible interactions combining dynamic covalent bonds (i.e., imine bond and borate ester bond) and noncovalent interactions (i.e., electrostatic interaction and hydrogen bond) provide effective energy dissipation to endure high fatigue resistance and cyclic loading. The dynamic hydrogel exhibited excellent mechanical properties like maximum 2.43 MPa compressive strength, 493.91 % fracture strain, and 89.54 kJ/m3 toughness. Moreover, the integrated hydrogel after injection and self-healing could withstand 150 successive compressive cycles. Besides, the bovine serum albumin embedded in CS-NPs could be sustainably released from the nanocomposite hydrogel for 12 days. This study proposes a novel strategy to synthesize an injectable and self-healing hydrogel combined with excellent mechanical properties for designing high-strength natural carriers with sustained protein delivery.

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.

Adhesive hydrogel releases protocatechualdehyde-Fe3+ complex to promote three healing stages for accelerated therapy of oral ulcers

Oral ulcers can significantly reduce the life quality of patients and even lead to malignant transformations. Local treatments using topical agents are often ineffective because of the wet and dynamic environment of the oral cavity. Current clinical treatments for oral ulcers, such as corticosteroids, have limitations and side effects for long-term usage. Here, we develop adhesive hydrogel patches (AHPs) that effectively promote the healing of oral ulcers in a rat model. The AHPs are comprised of the quaternary ammonium salt of chitosan, aldehyde-functionalized hyaluronic acid, and a tridentate complex of protocatechualdehyde and Fe3+ (PF). The AHPs exhibit tunable mechanical properties, self-healing ability, and wet adhesion on the oral mucosa. Through controlling the formula of the AHPs, PF released from the AHPs in a temporal manner. We further show that the AHPs have good biocompatibility and the capability to heal oral ulcers rapidly. Both in vitro and in vivo experiments indicate that the PF released from AHPs facilitated ulcer healing by suppressing inflammation, promoting macrophage polarization, enhancing cell proliferation, and inducing epithelial-mesenchymal transition involving inflammation, proliferation, and maturation stages. This study provides insights into the healing of oral ulcers and presents an effective therapeutic biomaterial for the treatment of oral ulcers. STATEMENT OF SIGNIFICANCE: By addressing the challenges associated with current clinical treatments for oral ulcers, the development of adhesive hydrogel patches (AHPs) presents an effective approach. These AHPs possess unique properties, such as tunable mechanical characteristics, self-healing ability, and strong adhesion to the mucosa. Through controlled release of protocatechualdehyde-Fe3+ complex, the AHPs facilitate the healing process by suppressing inflammation, promoting cell proliferation, and inducing epithelial-mesenchymal transition. The study not only provides valuable insights into the healing mechanisms of oral ulcers but also introduces a promising therapeutic biomaterial. This work holds significant scientific interest and demonstrates the potential to greatly improve the treatment outcomes and quality of life for individuals suffering from oral ulcers.

Advancements and Challenges in Self-Healing Hydrogels for Wound Care

This manuscript explores self-healing hydrogels as innovative solutions for diverse wound management challenges. Addressing antibiotic resistance and tailored wound care, these hydrogels exhibit promising outcomes, including accelerated wound closure and tissue regeneration. Advancements in multifunctional hydrogels with controlled drug release, antimicrobial properties, and real-time wound assessment capabilities signal a significant leap toward patient-centered treatments. However, challenges such as scalability, long-term safety evaluation, and variability in clinical outcomes persist. Future directions emphasize personalized medicine, manufacturing innovation, rigorous evaluation through clinical trials, and interdisciplinary collaboration. This manuscript features the ongoing pursuit of effective, adaptable, and comprehensive wound care solutions to transform medical treatments and improve patient outcomes.

Facile General Injectable Gelatin/Metal/Tea Polyphenol Double Nanonetworks Remodel Wound Microenvironment and Accelerate Healing

Treating the most widespread complication of diabetes: diabetic wounds poses a significant clinical obstacle due to the intricate nature of wound healing in individuals with diabetes. Here a novel approach is proposed using easily applicable injectable gelatin/metal/tea polyphenol double nanonetworks, which effectively remodel the wound microenvironment and accelerates the healing process. The gelatin(Gel) crosslink with metal ions (Zr4+ ) through the amino acids, imparting advantageous mechanical properties like self-healing, injectability, and adhesion. The nanonetwork's biological functions are further enhanced by incorporating the tea polyphenol metal nanonetwork through in situ doping of the epigallocatechin gallate (EGCG) with great antibacterial, self-healing, antioxidant, and anticancer capabilities. The in vitro and in vivo tests show that this double nanonetworks hydrogel exhibits faster cell migration and favorable anti-inflammatory and antioxidant properties and can greatly reshape the microenvironment of diabetic wounds and accelerate the wound healing rate. In addition, this hydrogel is completely degraded after subcutaneous injection for 7 days, with nondetectable cytotoxicity in H&E staining of major mice organs and the serum level of liver function indicators. Considering the above-mentioned merits of this hydrogel, it is believed that the injectable gelatin/metal/tea polyphenol double nanonetworks have broad biomedical potential, especially in diabetic wound repair and tissue engineering.

Signaling Pathways Triggering Therapeutic Hydrogels in Promoting Chronic Wound Healing

In recent years, there has been a significant increase in the prevalence of chronic wounds, such as pressure ulcers, diabetic foot ulcers, and venous ulcers of the lower extremities. The main contributors to chronic wound formation are bacterial infection, prolonged inflammation, and peripheral vascular disease. However, effectively treating these chronic wounds remains a global challenge. Hydrogels have extensively explored as wound healing dressing because of their excellent biocompatibility and structural similarity to extracellular matrix (ECM). Nonetheless, much is still unknown how the hydrogels promote wound repair and regeneration. Signaling pathways play critical roles in wound healing process by controlling and coordinating cells and biomolecules. Hydrogels, along with their therapeutic ingredients that impact signaling pathways, have the potential to significantly enhance the wound healing process and its ultimate outcomes. Understanding this interaction will undoubtedly provide new insights into developing advanced hydrogels for wound repair and regeneration. This paper reviews the latest studies on classical signaling pathways and potential targets influenced by hydrogel scaffolds in chronic wound healing. This work hopes that it will offer a different perspective in developing more efficient hydrogels for treating chronic wounds.

Stimuli-Responsive Hydrogel Adhesives for Wound Closure and Tissue Regeneration

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

Progress of polysaccharide-based tissue adhesives

Recently, polymer-based tissue adhesives (TAs) have gained the attention of scientists and industries as alternatives to sutures for sealing and closing wounds or incisions because of their ease of use, low cost, minimal tissue damage, and short application time. However, poor mechanical properties and weak adhesion strength limit the application of TAs, although numerous studies have attempted to develop new TAs with enhanced performance. Therefore, next-generation TAs with improved multifunctional properties are required. In this review, we address the requirements of polymeric TAs, adhesive characteristics, adhesion strength assessment methods, adhesion mechanisms, applications, advantages and disadvantages, and commercial products of polysaccharide (PS)-based TAs, including chitosan (CS), alginate (AL), dextran (DE), and hyaluronic acid (HA). Additionally, future perspectives are discussed.

Bionic Bilayer Scaffold for Synchronous Hyperthermia Therapy of Orthotopic Osteosarcoma and Osteochondral Regeneration

Large osseous void, postsurgical neoplastic recurrence, and slow bone-cartilage repair rate raise an imperative need to develop functional scaffold in clinical osteosarcoma treatment. Herein, a bionic bilayer scaffold constituting croconaine dye-polyethylene glycol@sodium alginate hydrogel and poly(l-lactide)/hydroxyapatite polymer matrix is fabricated to simultaneously achieve a highly efficient killing of osteosarcoma and an accelerated osteochondral regeneration. First, biomimetic osteochondral structure along with adequate interfacial interaction of the bilayer scaffold provide a structural reinforcement for transverse osseointegration and osteochondral regeneration, as evidenced by upregulated specific expressions of collagen type-I, osteopontin, and runt-related transcription factor 2. Meanwhile, thermal ablation of the synthesized nanoparticles and mitochondrial dysfunction caused by continuously released hydroxyapatite induce residual tumor necrosis synergistically. To validate the capabilities of inhibiting tumor growth and promoting osteochondral regeneration of our proposed scaffold, a novel orthotopic osteosarcoma model simulating clinical treatment scenarios of bone tumors is established on rats. Based on amounts of in vitro and in vivo results, an effective killing of osteosarcoma and a suitable osteal-microenvironment modulation of such bionic bilayer composite scaffold are achieved, which provides insightful implications for photonic hyperthermia therapy against osteosarcoma and following osseous tissue regeneration.

Nanoengineered Supramolecular Adhesive Sponge for Rapid Hemostasis and Abdominal Wall Wound Healing

Multifunctional dressing biomaterials that can promote tissue adhesion, hemostasis, and soft-tissue wound healing are of great clinical significance. Here, we report a nanocomposite supramolecular sponge constructed by an air-in-water emulsion template composed of methacrylated gelatin (GelMA), Laponite nanoclay, and branched supramolecular polymer (PAMU). The sponge has an interconnected macroporous structure and exhibits tunable mechanical properties with varying Laponite concentration. The nanoengineered sponge is endowed with tissue adhesion by intermolecular hydrogen bonds and ionic interactions contributed by the supramolecular polymer and the Laponite nanoclay. The biocompatible sponge facilitates cell proliferation and blood coagulation in both in vitro and in vivo experiments. In addition, the results of the rat external abdominal wall defect model show that the sponge can promote angiogenesis, collagen deposition, and granulation tissue formation to accelerate wound repair. These findings suggest that the unique air-in-water templated sponge is a promising candidate for applications in hemostasis and wound healing.

A guanosine/konjac glucomannan supramolecular hydrogel with antioxidant, antibacterial and immunoregulatory properties for cutaneous wound treatment

Developing naturally-derived wound dressing materials with intrinsic therapeutic effects is desirable for the clinical applications. Recently, guanosine-based supramolecular G-quadruplex (G4) hydrogel exhibited great potential in preparing biological materials due to its simple fabrication method and responsive gel networks. However, the weak mechanical properties and the consequent burst release of bioactive molecules restrict its clinical applications. Herein, we found that konjac glucomannan (KGM) with immunoregulatory effect did not affect the self-assembly of G-quadruplexes and thus effectively enhancing the mechanical properties of G4 hydrogel. Aloin, as a model drug, was in situ loaded into gel networks, finally obtaining the G4/Aloin-KGM hydrogel. This hydrogel exhibited porous morphology, swelling ability and hemostatic capability. Boronate bonds in G4 networks and aloin collectively endowed the hydrogel with excellent antioxidant performance. Meanwhile, aloin also provided outstanding in vitro and in vivo bactericidal ability. The wounds treated with this biocompatible hydrogel demonstrated faster regeneration of epithelial and dermal tissues, and the whole wound healing stages were accelerated by promoting collagen deposition, facilitating macrophage polarization towards M2 phenotype, down-regulating the expression level of IL-6, and up-regulating the expression level of IL-10, CD31 and α-SMA.

Rapid Preparation of Highly Stretchable and Fast Self-Repairing Antibacterial Hydrogels for Promoting Hemostasis and Wound Healing

Hydrogel dressings have emerged as a vital resource in wound management, offering several advantages over conventional wound dressing materials. Their inherent biocompatibility, ability to replicate the native extracellular matrix, and capacity to provide an ideal environment for cell survival make them particularly valuable. Nevertheless, the mechanical properties of many hydrogel dressings are an area that warrants improvement, as it currently constrains their application range. This limitation is especially evident when skin wounds are addressed in highly active or easily scratched areas. In this study, we present the development of a highly stretchable self-repairing hydrogel by cross-linking poly(vinyl alcohol) (PVA) through dynamic boron ester bonds, coupled with the hydrogen bonding of carboxymethyl cellulose sodium (CMC) via an efficient one-pot method without adding any catalyst. This innovative PVA/CMC hydrogel exhibited remarkable antibacterial properties achieved through the incorporation of bergamot oil, which was dispersed in a β-cyclodextrin solution. The hydrogel's elongation at the point of rupture reached an impressive 1910%, and it was capable of rapid self-healing in just 3 min upon bonding. Additionally, the hydrogel demonstrated excellent hemostatic properties, effectively mitigating blood loss and exudation. In vivo wound models have shown that PVA/CMC significantly expedites wound healing by reducing bacterial infections, inflammatory responses, and blood loss and by promoting collagen deposition. In summary, this research provides crucial insights into its potential as an advanced wound dressing material, particularly well-suited for addressing wounds in places with frequent activities or easy scratches.

Supramolecular hydrogels for wound repair and hemostasis

The unique network characteristics and stimuli responsiveness of supramolecular hydrogels have rendered them highly advantageous in the field of wound dressings, showcasing unprecedented potential. However, there are few reports on a comprehensive review of supramolecular hydrogel dressings for wound repair and hemostasis. This review first introduces the major cross-linking methods for supramolecular hydrogels, which includes hydrogen bonding, electrostatic interactions, hydrophobic interactions, host-guest interactions, metal ligand coordination and some other interactions. Then, we review the advanced materials reported in recent years and then summarize the basic principles of each cross-linking method. Next, we classify the network structures of supramolecular hydrogels before outlining their forming process and propose their potential future directions. Furthermore, we also discuss the raw materials, structural design principles, and material characteristics used to achieve the advanced functions of supramolecular hydrogels, such as antibacterial function, tissue adhesion, substance delivery, anti-inflammatory and antioxidant functions, cell behavior regulation, angiogenesis promotion, hemostasis and other innovative functions in recent years. Finally, the existing problems as well as future development directions of the cross-linking strategy, network design, and functions in wound repair and hemostasis of supramolecular hydrogels are discussed. This review is proposed to stimulate further exploration of supramolecular hydrogels on wound repair and hemostasis by researchers in the future.

Mild hyperthermia-assisted chitosan hydrogel with photothermal antibacterial property and CAT-like activity for infected wound healing

Infected wounds pose a serious threat to public health and pose a significant challenge and financial burden worldwide. The treatment of infected wounds is now an urgent problem to be solved. Herein, mild hyperthermia-assisted hydrogels composed of carboxymethyl chitosan (CMCs), oxidized dextran (Odex), epigallocatechin gallate (EGCG) and PtNPs@PVP (CAT-like nanoenzymes) were proposed for the repair of infected wounds. The incorporation of PtNPs@PVP nanoenzymes give the hydrogels excellent photothermal property and CAT-like activity. When the temperature is maintained at 42-45 °C under 808 nm near infrared (NIR) exposure, the CMCs/Odex/EGCG/Nanoenzymes (COEN2) hydrogel demonstrated highly enhanced antibacterial ability (95.9 % in vivo), hydrogen peroxide (H2O2) scavenging ratio (85.1 % in vitro) and oxygen supply (20.7 mg/L in vitro). Furthermore, this mild-heat stimulation also promoted angiogenesis in the damaged skin area. Overall, this multifunctional hydrogel with antibacterial, antioxidant, oxygen supply, hemostasis, and angiogenesis capabilities has shown great promise in the repair of infected wounds. This study establishes the paradigm of enhanced infected wound healing by mild hyperthermia-assisted H2O2 scavenging, oxygen supplemental, and photothermal antibacterial hydrogels.

Chitosan-sodium percarbonate-based hydrogels with sustained oxygen release potential stimulated angiogenesis and accelerated wound healing

The prolonged hypoxic conditions hinder chronic wounds from healing and lead to severe conditions such as delayed re-epithelialization and enhanced risk of infection. Multifunctional wound dressings are highly required to address the challenges of chronic wounds. Herein, we report polyurethane-coated sodium per carbonate-loaded chitosan hydrogel (CSPUO2 ) as a multifunctional dressing. The hydrogels (Control, CSPU, and CSPUO2 ) were prepared by freeze gelation method and the developed hydrogels showed high porosity, good absorption capacity, and adequate biodegradability. The release of oxygen from the CSPUO2 hydrogel was confirmed by the increase in pH and a sustained oxygen release was observed over the period of 21 days, due to polyurethane (CSPU) coating. The CSPUO2 hydrogel exhibited around 2-fold increased angiogenic potential in CAM assay when compared with Control and CSPU dressing. CSPUO2 also showed good level of antibacterial efficacy against E. coli and S. aureus. In a full-thickness rat wound model, CSPUO2 hydrogel considerably accelerated wound healing with exceptional re-epithelialization granulation tissue formation less inflammatory cells and improved skin architecture highlighting the tremendous therapeutic potential of this hydrogel when compared with control and CSPU to treat chronic diabetic and burn wounds.

Natural polymer-based bioadhesives as hemostatic platforms for wound healing

Medical adhesives are advanced but challenging alternatives to wound closure and repair, especially in mitigating uncontrolled hemorrhage. Ideal hemostatic adhesives need to meet good biocompatibility and biodegradability, adequate mechanical strength, and strong tissue adhesion functionality under wet and dynamic conditions. Considering these requirements, natural polymers such as polysaccharide, protein and DNA, attract great attention as candidates for making bioadhesives because of their distinctive physicochemical performances and biological properties. This review systematically summarizes the advances of bioadhesives based on natural polysaccharide, protein and DNA. Various physical and chemical cross-linking strategies have been introduced for adhesive synthesis and their hemostatic applications are introduced from the aspect of versatility. Furthermore, the possible challenges and future opportunities of bioadhesives are discussed, providing insights into the development of high-performance hemostatic materials.

Injectable smart stimuli-responsive hydrogels: pioneering advancements in biomedical applications

Hydrogels have established their significance as prominent biomaterials within the realm of biomedical research. However, injectable hydrogels have garnered greater attention compared with their conventional counterparts due to their excellent minimally invasive nature and adaptive behavior post-injection. With the rapid advancement of emerging chemistry and deepened understanding of biological processes, contemporary injectable hydrogels have been endowed with an "intelligent" capacity to respond to various endogenous/exogenous stimuli (such as temperature, pH, light and magnetic field). This innovation has spearheaded revolutionary transformations across fields such as tissue engineering repair, controlled drug delivery, disease-responsive therapies, and beyond. In this review, we comprehensively expound upon the raw materials (including natural and synthetic materials) and injectable principles of these advanced hydrogels, concurrently providing a detailed discussion of the prevalent strategies for conferring stimulus responsiveness. Finally, we elucidate the latest applications of these injectable "smart" stimuli-responsive hydrogels in the biomedical domain, offering insights into their prospects.

Self-Assembly of Hemimyzon Formosanus-Inspired Crescent-Shaped Nanosucker Arrays for Reversible Adhesion

Hemimyzon formosanus, a species of ray-finned fish, makes use of crescent-shaped abdominal suckers for adhering to irregular, rough, and slippery gravel in fast-flowing headwaters and minor tributaries. Bioinspired by the adhesion characteristics, two-dimensional non-close-packed colloidal crystals are self-assembled and serve as templates to pattern crescent-shaped shape memory polymer-based nanostructure arrays. By the manipulation of the configuration of nanosuckers through applying common solvent stimulations, the corresponding adhesion performances on glass, sandpaper, or even porcine kidney surfaces can be switched instantaneously and reversibly under ambient conditions. The biomimetic nanostructures indicate possible solutions to a variety of challenges, such as wound nursing, and so on.

Injectable Antiswelling and High-Strength Bioactive Hydrogels with a Wet Adhesion and Rapid Gelling Process to Promote Sutureless Wound Closure and Scar-free Repair of Infectious Wounds

Developing injectable antiswelling and high-strength bioactive hydrogels with wet tissue adhesiveness and a rapid gelling process to meet the requirements for rapid hemostasis, sutureless wound closure, and scar-free repair of infected skin wounds continues to have ongoing challenges. Herein, injectable, antibacterial, and antioxidant hydrogel adhesives based on poly(citric acid-co-polyethylene glycol)-g-dopamine and amino-terminated Pluronic F127 (APF) micelles loaded with astragaloside IV (AS) are prepared. The H2O2/horseradish peroxidase (HRP) system is used to cause cross-linking of the hydrogel network through oxidative coupling between catechol groups and chemical cross-linking between the catechol group and the amino group. The hydrogels exhibit a rapid gelling process, high mechanical strength, an antiswelling effect, good antioxidant property, H2O2 release behavior, and degradability. In addition, the hydrogels present good wet tissue adhesiveness, high bursting pressure, excellent antibacterial activity, long-term sustained release of AS, and good biocompatibility. The hydrogels perform good hemostasis on mouse liver, rat liver, and rabbit femoral vein bleeding models and achieve much better closure and healing of skin incisions than biomedical glue and surgical sutures. Furthermore, the hydrogel dressing significantly improved the scar-free repair of MRSA-infected full thickness skin defect wounds by modulating inflammation, regulating the ratio of collagen I/III, and improving the vascularization and granulation tissue formation. Thus, AS-loaded hydrogels show huge potential as multifunctional dressings for in vivo hemostasis, sutureless wound closure, and scar-free repair of infected skin wounds.

Bioinspired Adhesive Antibacterial Hydrogel with Self-Healing and On-Demand Removability for Enhanced Full-Thickness Skin Wound Repair

Adhesive-caused injury is a great threat for extensive full-thickness skin trauma because extra-strong adhesion can incur unbearable pain and exacerbate trauma upon removal. Herein, inspired by the mussel, we designed and fabricated an adhesive antibacterial hydrogel dressing based on dynamic host-guest interaction that enabled on-demand stimuli-triggered removal to effectively care for wounds. In contrast with most hard-to-removable dressing, this adhesive antibacterial hydrogel exhibited strong adhesion property (85 kPa), which could achieve painless and noninvasive on-demand separation within 2 s through a host-guest competition mechanism (amantadine). At the same time, the hydrogel exhibited rapid self-healing properties, and the broken hydrogel could be completely repaired within 5 min. The hydrogel also had excellent protein adsorption properties, mechanical properties, antibacterial properties, and biocompatibility. This on-demand removal was facilitated by the introduction of amantadine as a competitive guest, without any significant adverse effects on cell activity (>90%) or wound healing (98.5%) in vitro. The full-thickness rat-skin defect model and histomorphological evaluation showed that the hydrogel could significantly promote wound healing and reduce scar formation by regulating inflammation, accelerating skin re-epithelialization, and promoting granulation tissue formation. These results indicate that the developed adhesive antibacterial hydrogel offers a promising therapeutic strategy for the healing of extensive full-layer skin injuries.

Gelatin Sponges with a Uniform Interoperable Pore Structure and Biodegradability for Liver Injury Hemostasis and Tissue Regeneration

Developing a hemostatic sponge that can effectively control bleeding from visceral injuries while guiding in situ tissue regeneration in incompressible wounds remains a challenge. Most of the existing hemostatic sponges degrade slowly, are relatively single-functioning, and cannot cope with complex environments. Herein, a biodegradable rapidly hemostatic sponge (GPZ) was created by dual-dynamic-bond cross-linking among Zn2+, protocatechualdehyde (PA)-containing catechol and aldehyde groups, and gelatin. GPZ had a uniformly distributed interconnected pore structure with excellent fluid absorption. It could effectively absorb the oozing blood and increase the blood concentration while stimulating platelet activation and accelerating blood coagulation. Compared to commercial hemostats, GPZ treatment significantly accelerated hemostasis in the rat liver defect model (∼0.33 min, ≥50% reduction in the hemostatic time) and in the rabbit liver defect model (∼1.02 min, ≥60% reduction in the hemostatic time). Additionally, GPZ had excellent antibacterial and antioxidant properties that effectively protected the wound from infection and excessive inflammation. In the liver regeneration model, GPZ significantly increased the rate of hepatic tissue repair and promoted rapid functional recovery without complications and adverse reactions. Overall, we designed a simple and effective biodegradable rapid hemostatic sponge with good clinical translational potential for treating lethal incompressible bleeding and promoting wound healing.

Research progress related to thermosensitive hydrogel dressings in wound healing: a review

Wound healing is a dynamic and complex process in which the microenvironment at the wound site plays an important role. As a common material for wound healing, dressings accelerate wound healing and prevent external wound infections. Hydrogels have become a hot topic in wound-dressing research because of their high water content, good biocompatibility, and adjustable physical and chemical properties. Intelligent hydrogel dressings have attracted considerable attention because of their excellent environmental responsiveness. As smart polymer hydrogels, thermosensitive hydrogels can respond to small temperature changes in the environment, and their special properties make them superior to other hydrogels. This review mainly focuses on the research progress in thermosensitive intelligent hydrogel dressings for wound healing. Polymers suitable for hydrogel formation and the appropriate molecular design of the hydrogel network to achieve thermosensitive hydrogel properties are discussed, followed by the application of thermosensitive hydrogels as wound dressings. We also discuss the future perspectives of thermosensitive hydrogels as wound dressings and provide systematic theoretical support for wound healing.

Marine biomaterials in biomedical nano/micro-systems

Marine resources in unique marine environments provide abundant, cost-effective natural biomaterials with distinct structures, compositions, and biological activities compared to terrestrial species. These marine-derived raw materials, including polysaccharides, natural protein components, fatty acids, and marine minerals, etc., have shown great potential in preparing, stabilizing, or modifying multifunctional nano-/micro-systems and are widely applied in drug delivery, theragnostic, tissue engineering, etc. This review provides a comprehensive summary of the most current marine biomaterial-based nano-/micro-systems developed over the past three years, primarily focusing on therapeutic delivery studies and highlighting their potential to cure a variety of diseases. Specifically, we first provided a detailed introduction to the physicochemical characteristics and biological activities of natural marine biocomponents in their raw state. Furthermore, the assembly processes, potential functionalities of each building block, and a thorough evaluation of the pharmacokinetics and pharmacodynamics of advanced marine biomaterial-based systems and their effects on molecular pathophysiological processes were fully elucidated. Finally, a list of unresolved issues and pivotal challenges of marine-derived biomaterials applications, such as standardized distinction of raw materials, long-term biosafety in vivo, the feasibility of scale-up, etc., was presented. This review is expected to serve as a roadmap for fundamental research and facilitate the rational design of marine biomaterials for diverse emerging applications.

Physical dynamic double-network hydrogels as dressings to facilitate tissue repair

Double-network hydrogels can be tuned to have high mechanical strength, stability, elasticity and bioresponsive properties, which can be combined to create self-healing, adhesive and antibacterial wound dressings. Compared with single-network hydrogel, double-network hydrogel shows stronger mechanical properties and better stability. In comparison with chemical bonds, the cross-linking in double networks makes them more flexible than single-network hydrogels and capable of self-healing following mechanical damage. Here, we present the stepwise synthesis of physical double-network hydrogels where hydrogen bonds and coordination reactions provide self-healing, pH-responsive, tissue-adhesive, antioxidant, photothermal and antibacterial properties, and can be removed on demand. We then explain how to carry out physical, chemical and biological characterizations of the hydrogels for use as wound dressings, yet the double-network hydrogels could also be used in different applications such as tissue engineering scaffolds, cell/drug delivery systems, hemostatic agents or in flexible wearable devices for monitoring physiological and pathological parameters. We also outline how to use the double-network hydrogels in vivo as wound dressings or hemostatic agents. The synthesis of the ureido-pyrimidinone-modified gelatin, catechol-modified polymers and the hydrogels requires 84 h, 48 h and 1 h, respectively, whereas the in vivo assays require 3.5 weeks. The procedure is suitable for users with expertise in biomedical polymer materials.