Glycosaminoglycan-based hydrogels capture inflammatory chemokines and rescue defective wound healing in mice

Shark skin and mussel-inspired polyurethane hydrogel sponge for wounds with infection and exudate

Inspired by the antifouling properties of shark skin and the bioadhesion of mussels, our study presents a three-layer biomimetic wound dressing with hierarchical wettability and rapid exudate drainage capabilities. The shark skin-inspired hydrophobic modified polyurethane (PU) sponge provides antifouling properties and serves as a bacterial barrier. The mussel-inspired dopamine-functionalized carboxymethyl chitosan hydrogel (CMCS-DOP) absorbs exudates and forms an in situ hydrogel, effectively capturing and eliminating bacteria. The porous sponge layer in direct contact with the wound facilitates rapid exudate drainage, preventing excessive wound hydration. This hierarchical structure coordinates exudate transport and bacterial removal. The fabricated PCD hydrogel sponge dressing (PCD dressing) exhibits a wettability transition (contact angle: 3°-35°-101°) and a water vapor transmission rate of 1021-797-691 g/m2. It demonstrates potent bactericidal effects against Staphylococcus aureus and Escherichia coli, with survival rates of only 13 % and 14 %, respectively, and bacterial-blocking efficiencies of 89 % and 94 %. In a chronic bacterial infection wound model, the PCD dressing outperforms conventional clinical dressings, increasing the wound healing rate by 25.8 %, reducing inflammation, and enhancing angiogenesis and collagen deposition. Notably, the PCD mitigates oxidative stress at the wound site by regulating the polarization of anti-inflammatory macrophages. This exudate-draining and responsive dressing offers a promising strategy for promoting the healing of wounds with high exudate levels.

An approach for psoriasis of microneedle patch simultaneously targeting multiple inflammatory cytokines and relapse related T cells

Psoriasis is a chronic inflammatory skin disorder affecting approximately 125 million people globally. Topical medications are a cornerstone of current treatment protocols; however, their efficacy in mitigating inflammation is constrained by their predominantly single-target mechanisms. A significant challenge is the lack of pharmaceuticals specifically targeting CD8+ tissue resident memory T (CD8+ TRM) cells, which are the targets in psoriasis relapse. Consequently, relapse rates can soar to 90% post-treatment discontinuation. In this study, we successfully screened a specific macrophage membrane capable of targeting multiple inflammatory factors at psoriatic sites. This membrane was coextruded with etomoxir, a compound that targets CD8+ TRM cells. To enhance drug retention and penetration, we employed a delivery strategy involving PDA and microneedles, resulting in the synthesis of PDA-Etomoxir-Macrophage membrane@microneedle (PEM@m). In vivo, PEM@m exhibited superior efficacy in alleviating psoriasis symptoms and preventing relapse compared to the clinical drug calcipotriol (Cal). Mechanistically, PEM@m broadly inhibits inflammatory signals, and its reduction of CD8+ TRM cells can be associated with decreased activity in the pentose phosphate pathway (PPP). Our study offers a novel and promising approach for the definitive treatment of psoriasis.

Biochemical strategy-based hybrid hydrogel dressing-mediated in situ synthesis of selenoproteins for DFU immunity-microbiota homeostasis regulation

Chronic consequences of diabetes that are most commonly encountered are diabetic foot ulcers (DFUs), driven by microbiota-immune system dyshomeostasis, eventually leading to delayed wound healing. Available therapies, such as systemic or topical administration of anti-inflammatory or antimicrobial agents, are limited due to antibiotic resistance and immune dysfunction. Herein, a hybrid hydrogel dressing is developed as the artificial bioadhesive barrier at wound sites to maintain microbial and immunological homeostasis locally and have potent anti-inflammatory effects. Specifically, Zero-valent selenium nanoparticles are synthesized and encapsulated into the alginate-polyacrylamide interpenetrating hydrogel networks, during which trehalose is adopted to modify the network defects. Besides, as an anti-adhesion agent, trehalose has shown the ability to prevent immune degradation by reducing bacteria binding to HUVECs. The obtained hybrid hydrogel dressing serves as a physical barrier against microbiome invasion, further regulates the composition of the wound microbiome to restore microbial immune homeostasis at the wound site, and cooperatively relieves DFU-associated symptoms. Meanwhile, the hydrogel dressing can synthesize selenoproteins in situ based on biochemical strategies and significantly reduce the secretion of proinflammatory cytokines. The proposed biochemical strategy based on the hybrid hydrogel dressings can efficiently restore microbiota-immune homeostasis in the wounds, presenting a promising approach for DFU therapy in clinics.

Unveiling the therapeutic journey of snail mucus in diabetic wound care

A diabetic wound (DW) is an alteration in the highly orchestrated physiological sequence of wound healing especially, the inflammatory phase. These alterations result in the generation of oxidative stress and inflammation at the injury site. This further leads to the impairment in the angiogenesis, extracellular matrix, collagen deposition, and re-epithelialization. Additionally, in DW there is the presence of microbial load which makes the wound worse and impedes the wound healing cycle. There are several treatment strategies which have been employed by the researchers to mitigate the aforementioned challenges. However, they failed to address the multifactorial pathogenic nature of the disease. Looking at the severity of the disease researchers have explored snail mucus and its components such as achacin, allantoin, elastin, collagen, and glycosaminoglycan due to its multiple therapeutic potentials; however, glycosaminoglycan (GAGs) is very important among all because they accelerate the wound-healing process by promoting reepithelialization, vascularization, granulation, and angiogenesis at the site of injury. Despite its varied applications, the field of snail mucus in wound healing is still underexplored. The present review aims to highlight the role of snail mucus in diabetic wound healing, the advantages of snail mucus over conventional treatments, the therapeutic potential of snail mucus, and the application of snail mucus in DW. Additionally, clinical trials, patents, structural variations, and advancements in snail mucus characterization have been covered in the article.

Design and Structural Elucidation of Glycopeptide Fibrils: Emulating Glycosaminoglycan Functions for Biomedical Applications

Glycosaminoglycans (GAGs) are essential polysaccharides crucial for various cellular functions, such as cell proliferation, migration, and differentiation. However, their complex structure and variability from natural sources pose challenges for functional studies and therapeutic applications. In this study, we engineered a glycopeptide that assembles into fibrils, emulating the functional attributes of GAGs. Utilizing cryo-EM, we elucidated the atomic structure of the designed glycopeptide fibril, which is composed of three identical protofilaments intertwined into a left-handed helix and held together by a variety of intermolecular interactions. Remarkably, the functional sugar units, glucuronic acids, are orderly positioned on the fibril surface, making them readily accessible to the solvent. This distinctive spatial configuration allows the designed glycopeptide fibril to effectively mimic key GAG functionalities, including the promotion of cell proliferation, cell migration, and osteogenic differentiation. Our findings offer a structural framework for designing glycan functionalities on glycopeptide fibrils and open avenues for developing glycopeptide-based materials with versatile biological activities. This work further enhances the potential of these materials for applications in therapeutic and regenerative medicine.

Wound state monitoring by multiplexed, electrochemical, real-time, localized, inflammation-tracking nitric oxide sensor (MERLIN)

Nitric oxide (NO) released endogenously by induced NO synthase (iNOS) in macrophages is a key regulatory biomarker for wound inflammation. Detecting NO directly on the wound bed is challenging due to its short half-life time (6 to 50 seconds), low physiological concentration (nanomolar to micromolar), and interferences in the complex wound environment. Here, we present a compliant, multiplexed, electrochemical, real-time, localized, inflammation-tracking NO sensor (MERLIN) array for in vivo spatiotemporal measurement of NO, with high sensitivity (883 ± 283 nanoamperes per micromolar per square centimeter); selectivity against nitrites (~27,900-fold), ascorbic acid (~3800-fold), and uric acid (~6900-fold); and low limit of detection (~8.00 nM). MERLIN spatiotemporally tracked NO on rat skin wounds for 7 days, and results indicated that NO peaks on day 3, in line with previously reported iNOS activity. MERLIN allows spatial mapping of the NO gradient across the wound bed, which can be used to provide diagnostic information to assist wound care.

DNA binding effects of LDH nanozyme for aseptic osteolysis mitigation through STING pathway modulation

Persistent and intense inflammation is recognized as the primary cause of wear-particle-induced aseptic osteolysis, which ultimately resulting in aseptic prosthesis loosening. Reducing inflammation plays a significant role in mitigating osteolysis, and the STING pathway has emerged as a promising therapeutic target for its prevention. Specifically, damaged periprosthetic cells of aseptic osteolysis release double-stranded DNA (dsDNA) into the osteolytic microenvironment, serving as a specific stimulus for the STING pathway. Herein, we found that layered double hydroxide (LDH) nanozyme exhibited a robust DNA-binding capacity primarily mediated by van der Waals interactions, which showed superior performance in inhibiting dsDNA-induced inflammation of aseptic osteolysis. Importantly, such binding capability enabled effective co-loading LDH with STING inhibitor C176, thus facilitating inhibition of the STING pathway. Such synergistic actions contributed to ameliorate the inflammatory milieu and remodel the osteolysis microenvironment successfully to reduce cranial bone damage, which was confirmed on animal model of osteolysis. Collectively, this strategy demonstrated an effective approach by utilizing synergistic effects to establish a positive feedback loop in the treatment of osteolysis, thereby alleviating TiPs-induced periprosthetic osteolysis and preventing postoperative complications.

Advancement on heparin-based hydrogel/scaffolds in biomedical and tissue engineering applications: Delivery carrier and pre-clinical implications

The advancement of biomaterials utilization in biomedical and tissue regenerative applications has emerged progressively. Hydrogels are three-dimensional, hydrophilic polymeric networks that replicate the natural extracellular matrix (ECM), establishing a hydrated porous milieu that emulates biological functions such as proliferation and differentiation of cellular components. The application of biological macromolecules, particularly Heparin-based hydrogel, has garnered considerable interest owing to various intrinsic biological and mechanical properties. This comprehensive review paper is designed to elucidate the derivation of heparin and its purification method for biomedical uses. The article briefly outlines the diverse physiochemical and biological properties of heparin derivative-based hydrogels/scaffolds and emphasizes their significance as vehicles for growth factors, genes, and cells in complex biomedical and tissue engineering applications. This publication also summarizes the potential concerns associated with heparin-based derivatives, efforts to address these issues, and current clinical perspectives. This represents the inaugural instance of an extensive summarization of heparin-based hydrogels in biomedical applications, emphasizing pre-clinical and clinical investigations, which will further assist the scientific community in addressing the challenges associated with heparin-based hydrogels in biomedical contexts.

Hydrogel-based nonwoven with persistent porosity for whole-stage hypertonic wound healing by regulating of water vaporization enthalpy

Moisture induced by wound exudate is crucial throughout the wound repair process. The dressing directly affects the absorption, permeation, and evaporation of the wound exudate. However, most dressings in clinical often result in excessive dryness or moisture of wound due to their monotonous structure and function, leading to ineffective thermodynamic control of evaporation enthalpy. Herein, a hydrogel-based nonwoven dressing (Gel-Fabric) with asymmetric amphiphilic surface and persistent microscopic porous structure is constructed by integrating intrinsic hydrophilic absorbent hydrogel fibers and hydrophobic ultrafine PET fibers. The novel Gel-Fabric facilitates rapid vertical drainage of wound exudate through the capillary effect and Laplace pressure synergy. Additionally, dynamic stepwise moisture management is also achieved by regulating the vaporization enthalpy of exudate. In vivo experiments confirm that Gel-Fabric significantly promotes wound healing, vascularization, and endothelialization, achieving a higher healing rate than ordinary dressings. Furthermore, compared to the clinical dressings, Gel-Fabric significantly reduces the frequency of dressing changes, offering improved outcomes for patients and more efficient wound management for healthcare providers.

Advances in Designer Materials for Chronic Wound Healing

Significance: Nonhealing or chronic wounds represent a significant and growing global health concern, imposing substantial burdens on individuals, health care systems, and economies worldwide. Although the standard-of-care treatment involves the application of wound dressings, most dressing materials are not specifically designed to address the pathological processes underlying chronic wounds. This review highlights recent advances in biomaterial design tailored to chronic wound healing. Recent Advances: Chronic wounds are characterized by persistent inflammation, impaired granulation tissue formation, and delayed re-epithelialization. Newly developed designer materials aim to manage reactive oxygen species and extracellular matrix degradation to suppress inflammation while promoting vascularization, cell proliferation, and epithelial migration to accelerate tissue repair. Critical Issues: Designing optimal materials for chronic wounds remains challenging due to the diverse etiology and a multitude of pathological mechanisms underlying chronic wound healing. While designer materials can target specific aberrations, designing a materials approach that restores all aberrant wound-healing processes remains the Holy Grail. Addressing these issues requires a deep understanding of how cells interact with the materials and the complex etiology of chronic wounds. Future Directions: New material approaches that target wound mechanics and senescence to improve chronic wound closure are under development. Layered materials combining the best properties of the approaches discussed in this review will pave the way for designer materials optimized for chronic wound healing.

A Bio-Responsive Hydrogel with Spatially Heterogeneous Structure for Treating Infectious Tissue Injuries

Infectious tissue injuries, exacerbated by bacterial infections and antibiotic resistance, pose significant challenges for treatment and may lead to life-threatening systemic infections. In this study, a bio-responsive hydrogel system is developed, leveraging silver ions (Ag⁺) encapsulated in Preyssler-type polyoxometalates (POMs). The Ag⁺ ions are selectively released in response to endogenous sodium ions (Na⁺) within the biological environment, enabling broad-spectrum antibacterial activity. The POM serves as a protective matrix for Ag⁺, preserving its bioactivity while mitigating cytotoxicity and the reduction in antimicrobial efficacy associated with prolonged exposure. Additionally, a dual-channel technique is employed to fabricate fiber membranes with controllable and continuously stacked chemical compositions, ensuring efficient and uniform POM incorporation via hydrogen bonding within the fiber matrix. Subsequently, in situ hierarchical cross-linking process generated a spatially heterogeneous hydrogel with an interpenetrating network structure at multiple scales. This differentiated microstructure facilitates the controlled loading and release of diverse therapeutic components. Meanwhile, bioactive exosomes are integrated into the hydrogel, further enhancing its regenerative potential for treating infectious tissue injuries. In vitro and in vivo experiments demonstrated that the advanced hydrogel system provide a viable and efficient platform for addressing the challenges associated with infectious tissue injuries, offering a promising strategy for clinical applications.

Functional hydrogels for accelerated wound healing: advances in conductive hydrogels and self-powered electrical stimulation

Compared to traditional dressings, hydrogel dressings not only protect the wound surface and prevent bacterial infection but also possess excellent moisturizing properties, which can provide an optimal moist environment for wound healing, and exhibit good biocompatibility, making them considered the best wound treatment materials. This review focuses on the research status and application progress of various functional hydrogel dressings, such as hemostatic, antimicrobial, anti-inflammatory, antioxidant, and conductive hydrogels. It proposes the combination of conductive hydrogels with flexible solar cells to form self-powered devices. Compared to traditional externally powered devices, this approach can reduce carbon footprints by utilizing clean energy, aligning with carbon neutrality policy requirements. Additionally, it eliminates the need for frequent battery replacement or power connections, effectively saving labor and operational costs. Self-powered devices can convert solar energy into electrical energy, which is conducted to the wound site through hydrogels, generating continuous electrical stimulation (ES). This electrical stimulation guides the directional migration of keratinocytes and fibroblasts toward the center of the wound; activates the MAPK/ERK signaling pathway to accelerate the cell cycle process, and upregulates the expression of vascular endothelial growth factor, thereby inducing endothelial cell proliferation and lumen formation. These multiple mechanisms work synergistically to promote wound healing. Finally, the review provides an outlook on the emergence and applications of multifunctional hydrogels and stimuli-responsive hydrogels, highlighting common challenges in the future development of hydrogels, such as weak mechanical strength and poor long-term stability, as well as feasible solutions to these issues.

Molecular-Cellular Two-Pronged Reprogramming of Inflammatory Soft-Tissue Interface with an Immunosuppressive Pure DNA Hydrogel

Effective modulation of persistent inflammation is crucial for chronic wound healing. However, the interaction cascade between inflammatory factors and immune cells at the soft-tissue wound interface poses an incredible challenge for this purpose. Here, we report an immunosuppressive pure DNA hydrogel (Is-pDNAgel) that reprograms inflammatory responses from both molecular and cellular dimensions. Specifically, high-density negative charges enable Is-pDNAgel to efficiently scavenge free chemokines, mitigating neutrophil and macrophage infiltration. Moreover, its immunosuppressive domain synergistically acts on activated residual immune cells and suppresses multiple proinflammatory signaling pathways, thereby creating a positive circuit to boost anti-inflammatory efficacy. Is-pDNAgel can further facilitate migration and proliferation of endogenous endothelial cells owing to its intrinsic extracellular matrix-mimicking structure, promoting re-epithelialization and neovascularization for tissue regeneration without additional bioactive components. Such an "all-in-one" hydrogel outperforms a commercial dressing to accelerate the healing of chronic wounds in a diabetic mouse model, offering a valuable tool for developing regenerative medicine.

Andrias davidianus Derived Glycosaminoglycans Direct Diabetic Wound Repair by Reprogramming Reparative Macrophage Glucolipid Metabolism

Harnessing cross-species regenerative cues to direct human regenerative potential is increasingly recognized as an excellent strategy in regenerative medicine, particularly for addressing the challenges of impaired wound healing in aging populations. The skin mucus of Andrias davidianus plays a critical role in self-protection and tissue repair, yet the fundamental regenerative factors and mechanisms involved remain elusive. Here, this work presents evidence that glycosaminoglycans (GAGs) derived from the skin secretion of Andrias davidianus (SAGs) serve as potent mediators of angiogenesis and inflammatory remodeling, facilitating efficient healing of diabetic wounds. Mechanistic studies reveal that SAGs promote macrophage polarization toward an anti-inflammatory and pro-regenerative phenotype (CD206+/Arg1+) via glucolipid metabolic reprogramming. This process suppresses excessive inflammation and enhances the expression of VEGF and IL-10 to create a facilitative microenvironment for tissue regeneration. Additionally, this work develops SAGs-GelMA composite microspheres that address multiple stages of wound healing, including rapid hemostasis, exudate control, and activation of endogenous regenerative processes. This engineered approach significantly improves the scarless healing of diabetic wounds by facilitating the recruitment and activation of reparative macrophages. The findings offer new insights into the regenerative mechanisms of Andrias davidianus and highlight the potential therapeutic application of SAGs in tissue repair.

Anchoring of Probiotic-Membrane Vesicles in Hydrogels Facilitates Wound Vascularization

Inadequate vascularization significantly hampers wound recovery by limiting nutrient delivery. To address this challenge, we extracted membrane vesicles from Lactobacillus reuteri (LMVs) and identified their angiogenic potential via transcriptomic analysis. We further developed a composite hydrogel system (Gel-LMVs) by anchoring LMVs within carboxylated chitosan and cross-linking it with oxidized hyaluronic acid through a Schiff base reaction. The resulting Gel-LMVs exhibit good biocompatibility and retain the bioactivity of LMVs, which are released in a controlled manner to stimulate cell proliferation, migration, and angiogenesis in vitro by modulating gene expression in critical signaling pathways. Moreover, in an in vivo model, Gel-LMVs upregulate vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule (CD31), leading to accelerated vascularization in early healing stages, while concurrently reducing inflammation and augmenting collagen deposition to enhance wound healing quality. This approach to functionalizing biomaterials with probiotic-MVs offers an advanced strategy for wound healing.

Intrinsic immunomodulatory hydrogels for chronic inflammation

The immune system plays a pivotal role in maintaining physiological homeostasis and influencing disease processes. Dysregulated immune responses drive chronic inflammation, which in turn results in a range of diseases that are among the leading causes of death globally. Traditional immune interventions, which aim to regulate either insufficient or excessive inflammation, frequently entail lifelong comorbidities and the risk of severe side effects. In this context, intrinsic immunomodulatory hydrogels, designed to precisely control the local immune microenvironment, have recently attracted increasing attention. In particular, these advanced hydrogels not only function as delivery mechanisms but also actively engage in immune modulation, optimizing interactions with the immune system for enhanced tissue repair, thereby providing a sophisticated strategy for managing chronic inflammation. In this tutorial review, we outline key elements of chronic inflammation and subsequently explore the strategic design principles of intrinsic immunomodulatory hydrogels based on these elements. Finally, we examine the challenges and prospects of such immunomodulatory hydrogels, which are expected to inspire further preclinical research and clinical translation in addressing chronic inflammation.

Naturally Inspired Tree-Ring Structured Dressing Provides Sustained Wound Tightening and Accelerates Closure

Mechanically regulated wound dressings require a rational combination of contraction and adhesion functions as well as balancing exudate-induced swelling issues. However, many of the reported dressings face the dilemma of impaired function and impeded wound self-contraction due to fluid-absorbing swelling. In this study, inspired by the tree ring, a core-ring structured hydrogel dressing capable of mechanical modulation is designed, and prepare it using a simple two-step photopolymerization process. The core covers the center of the wound, contracts spontaneously at body temperature to generate a contractile force of 3.4 kPa, and resists swelling. Meanwhile, the ring adheres to the normal epidermis around the wound and transfers the contraction stress to the wound edge. The integration of a functionally independent core and ring ultimately achieves effective wound traction and avoids dressing swelling. In murine and porcine skin wound-healing models, this hydrogel with a closely connected core and ring promotes healing by accelerating epidermal closure (50% closure in mouse skin on day 2, 85% closure in pig skin on day 8), collagen deposition, vascular maturation, and extracellular matrix remodeling. These results can guide further research on mechanical force modulation in wound healing, with the potential for clinical translation.

Anti-inflammatory effects of cyclodextrin nanoparticles enable macrophage repolarization and reduce inflammation

Inflammation plays a critical role in the pathophysiology of many diseases, and dysregulation of the involved signaling cascades often culminates in uncontrollable disease progression and, ultimately, chronic manifestation. Addressing these disorders requires balancing inflammation control while preserving essential immune functions. Cyclodextrins (CDs), particularly β-CD, have gained attention as biocompatible biomaterials with intrinsic anti-inflammatory properties, and chemical modification of their backbone offers a promising strategy to enhance their physicochemical properties, adaptability, and therapeutic potential. This study evaluated and characterized the immunomodulatory effects of amphiphilic CD derivatives, which self-assemble into nanoparticles, compared to soluble parent β-CD. In a human macrophage model, CD nanoparticles demonstrated superior anti-inflammatory activity, with derivative-specific effects tied to their physicochemical properties, surpassing the soluble β-CD control. Alongside the downregulation of key pro-inflammatory markers, significant reductions in inflammasome activation and changes in lipid profiles were observed. The findings of this study underscore the potential of cyclodextrin-based nanoparticles as versatile biomaterials for treating the complex pathophysiology of various acute and chronic inflammation-associated disorders.

Biologically inspired bioactive hydrogels for scarless corneal repair

Corneal injury-induced fibrosis occurs because of corneal epithelial basement membrane (EBM) injury and defective regeneration. Corneal fibrosis inhibition and transparency restoration depend on reestablished EBM, where the collagen network provides structural stability and heparan sulfate binds corneal epithelium-derived cytokines to regulate homeostasis. Inspired by this, bioactive hydrogels (Hep@Gel) composed of collagen-derived gelatins and highly anionic heparin were constructed for scarless corneal repair. Hep@Gel resembled the barrier function of the EBM regarding surface-confined binding, long-time sequestration, and progressive degradation of IL-1, TGF-β, and PDGF-BB, which robustly inhibited the apoptosis and myofibroblast transition of keratocytes. Animal models of rabbits and nonhuman primates confirmed that Hep@Gel effectively limited the influx of inflammatory and fibrotic cytokines from the epithelium into the stroma to down-regulate the wound healing cascade, contributing to better vision quality with 73% reduced fibrosis. Hep@Gel offers a solution for preventing corneal injury-induced scarring and substituting for lamellar keratoplasty to remove scarring.

Early Initiation of Icodextrin Reduces Peritoneal Dialysis-Associated Peritonitis Risk: A Retrospective Cohort Study

INTRODUCTION

Peritonitis is a common and serious complication of peritoneal dialysis (PD) that leads to its discontinuation and death. Icodextrin (ICO) improves peritoneal ultrafiltration and its early use reduces mortality. However, its effectiveness in reducing PD-associated infections remains to be elucidated.

METHODS

This retrospective observational study enrolled patients who underwent PD between September 2011 and March 2020. The patients were classified into two groups: those who received ICO at the initiation of PD therapy (early ICO) and those who received ICO later or not at all (late/no ICO) and were followed up from PD induction until PD cessation, death, or 3 years had passed.

RESULTS

Of the 82 patients (age, 61 [53-72] years), 21 received early ICO. During follow-up (36 [14-36] months), the incidence of PD-associated peritonitis was 0.17 episodes per patient-year. Log-rank tests indicated that PD-associated peritonitis and tunnel infection (TI)-free survival rates were significantly better with the early use of ICO than with late/no ICO (p = 0.02 and p = 0.01, respectively). The early use of ICO remained significantly associated with decreased incidence of both peritonitis and TI (hazard ratio [HR], 0.19; 95% confidence interval [CI], 0.06-0.69 and HR, 0.10; 95% CI, 0.01-0.78, respectively) using Cox regression analysis adjusted for potential confounders.

CONCLUSION

Beginning ICO administration at the initiation of PD shows promise for mitigating the risks of PD-associated peritonitis and TI.

Immunomodulatory Hydrogel for Electrostatically Capturing Pro-inflammatory Factors and Chemically Scavenging Reactive Oxygen Species in Chronic Diabetic Wound Remodeling

Diabetic wound exhibits the complex characteristics involving continuous oxidative stress and excessive expression of pro-inflammatory cytokines to cause a long-term inflammatory microenvironment. The repair healing of chronic diabetic wounding is tremendously hindered due to persistent inflammatory reaction. To address the aforementioned issues, here, a dual-functional hydrogel is designed, consisting of N1-(4-boronobenzyl)-N3-(4-boronophenyl)-N1, N1, N3, N3-tetramethylpropane-1, 3-diaminium (TSPBA) modified polyvinyl alcohol (PVA) and methacrylamide carboxymethyl chitosan (CMCSMA) can not only electrostatically adsorb proinflammatory cytokines of IL1-β and TNF-α, but can also chemically scavenge the excessive reactive oxygen species (ROS) in situ. Both in vitro and in vivo evaluations verify that the negatively charged and ROS-responsive hydrogel (NCRH) can effectively modulate the chronic inflammatory microenvironment of diabetic wounds and significantly enhance wound remodeling. More importantly, the well-designed NCRH shows a superior skin recovery in comparison with the commercial competitor product of wound dressing. Consequently, the current work highlights the need for new strategies to expedite the healing process of diabetic wounds and offers a wound dressing material with immunomodulation.

A microenvironment-modulating dressing with proliferative degradants for the healing of diabetic wounds

Diabetic wounds are usually entangled in a disorganized and self-perpetuating microenvironment and accompanied by a prolonged delay in tissue repair. Sustained and coordinated microenvironment regulation and tissue regeneration are key to the healing process of diabetic wounds, yet they continue to pose a formidable challenge. Here we report a rational double-layered dressing design based on chitosan and a degradable conjugated polymer polydiacetylene, poly(deca-4,6-diynedioic acid) (PDDA), that can meet this intricate requirement. With an alternating ene-yne backbone, PDDA degrades when reacting with various types of reactive oxygen species (ROS), and more importantly, generates proliferative succinic acid as a major degradant. Inheriting from PDDA, the developed PDDA-chitosan double layer dressing (PCD) can eliminate ROS in the microenvironment of diabetic wounds, alleviate inflammation, and downregulate gene expression of innate immune receptors. PCD degradation also triggers simultaneous release of succinic acid in a sustainable manner, enabling long-term promotion on tissue regeneration. We have validated the biocompatibility and excellent performance of PCD in expediting the wound healing on both diabetic mouse and porcine models, which underscores the significant translational potential of this microenvironment-modulating, growth-promoting wound dressing in diabetic wounds care.

Inflammation-Modulating Biomedical Interventions for Diabetic Wound Healing: An Overview of Preclinical and Clinical Studies

A diabetic wound exemplifies the challenge of chronic, nonhealing wounds. Elevated blood sugar levels in diabetes profoundly disrupt macrophage function, impairing crucial activities such as phagocytosis, immune response, cell migration, and blood vessel formation, all essential for effective wound healing. Moreover, the persistent presence of pro-inflammatory cytokines and reactive oxygen species, coupled with a decrease in anti-inflammatory factors, exacerbates the delay in wound healing associated with diabetes. This review emphasizes the dysfunctional inflammatory responses underlying diabetic wounds and explores preclinical studies of inflammation-modulating bioactives and biomaterials that show promise in expediting diabetic wound healing. Additionally, this review provides an overview of selected clinical studies employing biomaterials and bioactive molecules, shedding light on the gap between extensive preclinical research and limited clinical studies in this field.

Biomedical Applications and Nutritional Value of Specific Food-Derived Polysaccharide-Based Hydrogels

Food-derived polysaccharide-based hydrogels (FPBHs), which are composed of polysaccharides derived from food sources exhibit great potential for biomedical applications. The FPBHs possess a wide range of biological activities and can be utilized in the treatment of various clinical diseases. However, the majority of research efforts have predominantly focused on nonspecific polysaccharides derived from various sources (most plants, animals, and microorganisms), whereas the exploration of hydrogels originating from specific polysaccharides with distinct bioactivity extracted from natural food sources remains limited. In this review, a comprehensive search was conducted across 3 major databases (PubMed, Web of Science, and Medline) until October 24, 2024 to include 32 studies that employed FPBHs for biomedical applications. This review provides an overview of hydrogels based on specific food-derived polysaccharides by summarizing their types, sources, molecular weight, monosaccharide composition, and biological activities. The crosslinking strategies employed in the fabrication of FPBHs were demonstrated. The attributes and characteristics of FPBHs were delined, including their physical, chemical, and functional properties. Of particular note, the review highlights in vivo and in vitro studies exploring the biomedical applications of FPBHs and delve into the nutritional value of specific food-derived polysaccharides. The challenges encountered in basic research involving FPBHs were enumerated as well as limitation in their clinical practice. Finally, the potential market outlook for FPBHs in the future was also discussed.

Immunomodulatory Biomaterials: Tailoring Surface Properties to Mitigate Foreign Body Reaction and Enhance Tissue Regeneration

The immune cells have demonstrated the ability to promote tissue repair by removing debris, breaking down the extracellular matrix, and regulating cytokine secretion profile. If the behavior of immune cells is not well directed, chronic inflammation and foreign body reaction (FBR) will lead to scar formation and loss of biomaterial functionality. The immunologic response toward tissue repair or chronic inflammation after injury and implantation can be modulated by manipulating the surface properties of biomaterials. Tailoring surface properties of biomaterials enables the regulation of immune cell fate such as adhesion, proliferation, recruitment, polarization, and cytokine secretion profile. This review begins with an overview of the role of immune cells in tissue healing and their interactions with biomaterials. It then discusses how the surface properties of biomaterials influence immune cell behavior. The core focus is reviewing surface modification methods to create innovative materials that reduce foreign body reactions and enhance tissue repair and regeneration by modulating immune cell activities. The review concludes with insights into future advancements in surface modification techniques and the associated challenges.

Bioresponsive Immunotherapeutic Materials

The human immune system is an interaction network of biological processes, and its dysfunction is closely associated with a wide array of diseases, such as cancer, infectious diseases, tissue damage, and autoimmune diseases. Manipulation of the immune response network in a desired and controlled fashion has been regarded as a promising strategy for maximizing immunotherapeutic efficacy and minimizing side effects. Integration of "smart" bioresponsive materials with immunoactive agents including small molecules, biomacromolecules, and cells can achieve on-demand release of agents at targeted sites to reduce overdose-related toxicity and alleviate off-target effects. This review highlights the design principles of bioresponsive immunotherapeutic materials and discusses the critical roles of controlled release of immunoactive agents from bioresponsive materials in recruiting, housing, and manipulating immune cells for evoking desired immune responses. Challenges and future directions from the perspective of clinical translation are also discussed.

Granular Biomaterials as Bioactive Sponges for the Sequestration and Release of Signaling Molecules

A major challenge for the regeneration of chronic wounds is an underlying dysregulation of signaling molecules, including inflammatory cytokines and growth factors. To address this, it is proposed to use granular biomaterials composed of jammed microgels, to enable the rapid uptake and delivery of biomolecules, and provide a strategy to locally sequester and release biomolecules. Sequestration assays on model biomolecules of different sizes demonstrate that granular hydrogels exhibit faster transport than comparable bulk hydrogels due to enhanced surface area and decreased diffusion lengths. To demonstrate the potential of modular granular hydrogels to modulate local biomolecule concentrations, microgel scaffolds are engineered that can simultaneously sequester excess pro-inflammatory factors and release pro-healing factors. To target specific biomolecules, microgels are functionalized with affinity ligands that bind either to interleukin 6 (IL-6) or to vascular endothelial growth factor A (VEGF-A). Finally, disparate microgels are combined into a single granular biomaterial for simultaneous sequestration of IL-6 and release of VEGF-A. Overall, the potential of modular granular hydrogels is demonstrated to locally tailor the relative concentrations of pro- and anti-inflammatory factors.

Self-Growing Hydrogel Bioadhesives for Chronic Wound Management

Hydrogel bioadhesives have emerged as a promising alternative to wound dressings for chronic wound management. However, many existing bioadhesives do not meet the functional requirements for efficient wound management through dynamically mechanical modulation, due to the reduced wound contractibility, frequent wound recurrence, incapability to actively adapt to external microenvironment variation, especially for those gradually-expanded chronic wounds. Here, a self-growing hydrogel bioadhesive (sGHB) patch that exhibits instant adhesion to biological tissues but also a gradual increase in mechanical strength and interfacial adhesive strength within a 120-h application is presented. The gradually increased mechanics of the sGHB patch could effectively mitigate the stress concentration at the wound edge, and also resist the wound expansion at various stages, thus mechanically contracting the chronic wounds in a programmable manner. The self-growing hydrogel patch demonstrated enhanced wound healing efficacy in a mouse diabetic wound model, by regulating the inflammatory response, promoting the faster re-epithelialization and angiogenesis through mechanical modulation. Such kind of self-growing hydrogel bioadhesives have potential clinical utility for a variety of wound management where dynamic mechanical modulation is indispensable.

Therapeutic Effect of Decellularized Extracellular Matrix from Fish Skin for Accelerating Skin Regeneration

A cellular matrix derived from natural tissue functions as a highly biocompatible and versatile material for wound healing application. It provides a complex and highly organized environment with biological molecules and physical stimuli. Recently, various kinds of tissue/organ decellularized extracellular matrixes (dECMs) from bovine and porcine have been used as biomedical applications to support tissue regeneration but inherit religious restrictions and the risk of disease transmission to humans. Marine fish-derived dECMs are seen as attractive alternatives due to their similarity to mammalian physiology, reduced biological risks, and fewer religious restrictions. The aim of this study was to derive a decellularized matrix from the olive flounder (Paralichthys olivaceus) skin and evaluate its suitability as a wound healing application. Olive flounder skin was treated with a series of chemical treatments to remove cellular components. Decellularized fish skin (dFS) was confirmed to be successful in decellularization by evaluating the DNA content (2.84%). The dFS was characterized and evaluated in vivo to assess its biological activities. The mouse wound defect model was used to evaluate the in vivo performance of the dFS compared with that of the decellularized porcine skin (dPS). The resultant dFS was shown to enhance wound healing compared with the no-treatment group and dPS. This study suggests that dFS has potential for skin regeneration application.

Polysaccharide- and protein-based hydrogel dressings that enhance wound healing: A review

Hydrogels can possess desired biochemical and mechanical properties, excellent biocompatibility, satisfactory biodegradability, and biological capabilities that promote skin repair, making them ideal candidates for skin healing dressings. Polysaccharides, such as chitosan, hyaluronic acid and sodium alginate as well as proteins, including gelatin, collagen and fibroin proteins, are biological macromolecules celebrated for their biocompatibility and biodegradability, are at the forefront of innovative hydrogel dressing development. This work first summarizes the skin wound healing process and its influencing factors, and then systematically articulates the multifunctional roles of hydrogels based on biological macromolecules (polysaccharides and proteins) as dressing in addressing bacterial infection, hemorrhage and inflammation during wound healing. Furthermore, this review explores the potential of these hydrogels as vehicles for combination therapy, by incorporating growth factors or stem cells. Finally, the article offers insights into future directions of such hydrogels in wound repair field.

A Multifunctional Nanostructured Hydrogel as a Platform for Deciphering Niche Interactions of Hematopoietic Stem and Progenitor Cells

For over half a century, hematopoietic stem cells (HSCs) have been used for transplantation therapy to treat severe hematologic diseases. Successful outcomes depend on collecting sufficient donor HSCs as well as ensuring efficient engraftment. These processes are influenced by dynamic interactions of HSCs with the bone marrow niche, which can be revealed by artificial niche models. Here, a multifunctional nanostructured hydrogel is presented as a 2D platform to investigate how the interdependencies of cytokine binding and nanopatterned adhesive ligands influence the behavior of human hematopoietic stem and progenitor cells (HSPCs). The results indicate that the degree of HSPC polarization and motility, observed when cultured on gels presenting the chemokine SDF-1α and a nanoscale-defined density of a cellular (IDSP) or extracellular matrix (LDV) α4β1 integrin binding motif, are differently influenced on hydrogels functionalized with the different ligand types. Further, SDF-1α promotes cell polarization but not motility. Strikingly, the degree of differentiation correlates negatively with the nanoparticle spacing, which determines ligand density, but only for the cellular-derived IDSP motif. This mechanism potentially offers a means of predictably regulating early HSC fate decisions. Consequently, the innovative multifunctional hydrogel holds promise for deciphering dynamic HSPC-niche interactions and refining transplantation therapy protocols.

Advances and Challenges in Immune-Modulatory Biomaterials for Wound Healing Applications

Wound healing progresses through three distinct stages: inflammation, proliferation, and remodeling. Immune regulation is a central component throughout, crucial for orchestrating inflammatory responses, facilitating tissue repair, and restraining scar tissue formation. Elements such as mitochondria, reactive oxygen species (ROS), macrophages, autophagy, ferroptosis, and cytokines collaboratively shape immune regulation in this healing process. Skin wound dressings, recognized for their ability to augment biomaterials' immunomodulatory characteristics via antimicrobial, antioxidative, pro- or anti-inflammatory, and tissue-regenerative capacities, have garnered heightened attention. Notwithstanding, a lack of comprehensive research addressing how these dressings attain immunomodulatory properties and the mechanisms thereof persists. Hence, this paper pioneers a systematic review of biomaterials, emphasizing immune regulation and their underlying immunological mechanisms. It begins by highlighting the importance of immune regulation in wound healing and the peculiarities and obstacles faced in skin injury recovery. This segment explores the impact of wound metabolism, infections, systemic illnesses, and local immobilization on the immune response during healing. Subsequently, the review examines a spectrum of biomaterials utilized in skin wound therapy, including hydrogels, aerogels, electrospun nanofiber membranes, collagen scaffolds, microneedles, sponges, and 3D-printed constructs. It elaborates on the immunomodulatory approaches employed by these materials, focusing on mitochondrial and ROS modulation, autophagic processes, ferroptosis, macrophage modulation, and the influence of cytokines on wound healing. Acknowledging the challenge of antibiotic resistance, the paper also summarizes promising plant-based alternatives for biomaterial integration, including curcumin. In its concluding sections, the review charts recent advancements and prospects in biomaterials that accelerate skin wound healing via immune modulation. This includes exploring mitochondrial transplantation materials, biomaterial morphology optimization, metal ion incorporation, electrostimulation-enabled immune response control, and the benefits of composite materials in immune-regulatory wound dressings. The ultimate objective is to establish a theoretical foundation and guide future investigations in the realm of skin wound healing and related materials science disciplines.

The Influence of Sulfation Degree of Glycosaminoglycan-Functionalized 3D Collagen I Networks on Cytokine Profiles of In Vitro Macrophage-Fibroblast Cocultures

Cell-cell interactions between fibroblasts and immune cells, like macrophages, are influenced by interaction with the surrounding extracellular matrix during wound healing. In vitro hydrogel models that mimic and modulate these interactions, especially of soluble mediators like cytokines, may allow for a more detailed investigation of immunomodulatory processes. In the present study, a biomimetic extracellular matrix model based on fibrillar 3D collagen I networks with a functionalization with heparin or 6-ON-desulfated heparin, as mimics of naturally occurring heparan sulfate, was developed to modulate cytokine binding effects with the hydrogel matrix. The constitution and microstructure of the collagen I network were found to be stable throughout the 7-day culture period. A coculture study of primary human fibroblasts/myofibroblasts and M-CSF-stimulated macrophages was used to show its applicability to simulate processes of progressed wound healing. The quantification of secreted cytokines (IL-8, IL-10, IL-6, FGF-2) in the cell culture supernatant demonstrated the differential impact of glycosaminoglycan functionalization of the collagen I network. Most prominently, IL-6 and FGF-2 were shown to be regulated by the cell culture condition and network constitution, indicating changes in paracrine and autocrine cell-cell communication of the fibroblast-macrophage coculture. From this perspective, we consider our newly established in vitro hydrogel model suitable for mechanistic coculture analyses of primary human cells to unravel the role of extracellular matrix factors in key events of tissue regeneration and beyond.

Targeting Macrophage Polarization for Reinstating Homeostasis following Tissue Damage

Tissue regeneration and remodeling involve many complex stages. Macrophages are critical in maintaining micro-environmental homeostasis by regulating inflammation and orchestrating wound healing. They display high plasticity in response to various stimuli, showing a spectrum of functional phenotypes that vary from M1 (pro-inflammatory) to M2 (anti-inflammatory) macrophages. While transient inflammation is an essential trigger for tissue healing following an injury, sustained inflammation (e.g., in foreign body response to implants, diabetes or inflammatory diseases) can hinder tissue healing and cause tissue damage. Modulating macrophage polarization has emerged as an effective strategy for enhancing immune-mediated tissue regeneration and promoting better integration of implantable materials in the host. This article provides an overview of macrophages' functional properties followed by discussing different strategies for modulating macrophage polarization. Advances in the use of synthetic and natural biomaterials to fabricate immune-modulatory materials are highlighted. This reveals that the development and clinical application of more effective immunomodulatory systems targeting macrophage polarization under pathological conditions will be driven by a detailed understanding of the factors that regulate macrophage polarization and biological function in order to optimize existing methods and generate novel strategies to control cell phenotype.

Advances and challenges in regenerative therapies for abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a significant source of mortality worldwide and carries a mortality of greater than 80% after rupture. Despite extensive efforts to develop pharmacological treatments, there is currently no effective agent to prevent aneurysm growth and rupture. Current treatment paradigms only rely on the identification and surveillance of small aneurysms, prior to ultimate open surgical or endovascular repair. Recently, regenerative therapies have emerged as promising avenues to address the degenerative changes observed in AAA. This review briefly outlines current clinical management principles, characteristics, and pharmaceutical targets of AAA. Subsequently, a thorough discussion of regenerative approaches is provided. These include cellular approaches (vascular smooth muscle cells, endothelial cells, and mesenchymal stem cells) as well as the delivery of therapeutic molecules, gene therapies, and regenerative biomaterials. Lastly, additional barriers and considerations for clinical translation are provided. In conclusion, regenerative approaches hold significant promise for in situ reversal of tissue damages in AAA, necessitating sustained research and innovation to achieve successful and translatable therapies in a new era in AAA management.

Photodynamic therapy mediated by methylene blue-loaded PEG accelerates skin mouse wound healing: an immune response

PURPOSE

Conventional approaches for enhancing wound healing may not always yield satisfactory results. Instead, we test the effectiveness of a newly developed photodynamic therapy (PDT) that uses methylene blue (MB) loaded with polyethylene glycol (PEG) (MB-PEG) hydrogel to accelerate wound healing process in mice.

METHODS

A dorsal skin incision with 6 mm punch which topically subjected to MB-PEG hydrogel and a low-level laser light of red light to assess the regeneration process of wounded skin. A total of 63 adult male CD1 mice divided into normal group (no treatment) and other wound groups received different treatments of laser (650 ± 5 nm and power intensity of 180 mW/cm2), MB-PEG, or PDT (MB-PEG followed by laser). The wound healing parameters were investigated by histological examination of the skin and measuring of proinflammatory cytokines at the early stage (48 h) and a late one on day 21.

RESULTS

at 48 h, the score of tissue granulation, inflammation, and angiogenesis process were markedly improved in wounded groups that received MB + PEG combined with laser compared to the group treated with laser alone. On day 21, a significant improvement of the inflammation was detected in the group treated with MB + PEG plus laser compared to the other groups. At 48 h, the upregulated serum levels of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in the wound group were significantly (P < 0.001) reduced in the group treated with MB + PEG combined with laser.

CONCLUSION

MB-PEG based hydrogel improves and accelerates wound closure in the context of laser compared to either single treatment.

Carboxymethyl chitosan-based hydrogel-Janus nanofiber scaffolds with unidirectional storage-drainage of biofluid for accelerating full-thickness wound healing

Self-pumping wound scaffolds designed for directional biofluid transport are extensively investigated. They efficiently extract excessive biofluids from wounds, while maintaining an optimally humid wound environment, thus facilitating rapid wound healing. However, the existing designed scaffolds are insufficiently focused on stimulating the hydrophobic layer at the wound site, thereby exacerbating inflammation and impeding the wound healing process. Herein, we engineered and fabricated a hydrophilic-hydrophobic-hydrophilic sandwich-structured hydrogel-Janus nanofiber scaffold (NFS) employing a Layer-by-Layer (LbL) method. This scaffold comprises a hydrophilic carboxymethyl chitosan/silver (CMCS-Ag) hydrogel component in conjunction with a poly(caprolactone)/poly(caprolactone)-poly(citric acid)-co-ε-polylysine (PCL/PCL-PCE) Janus NFS. It is noteworthy that the hydrogel-Janus nanofiber scaffold not only demonstrates outstanding water absorption (202.2 %) and unidirectional biofluid transport capability but also possesses high breathability (308.663 m3/m2 h kPa), appropriate pore size (6.7-7.5 μm), excellent tensile performance (270 ± 10 %), and superior mechanical strength (26.36 ± 1.77 MPa). Moreover, in vitro experimentation has convincingly demonstrated the impeccable biocompatibility of hydrogel-Janus NFS. The inherent dual-antibacterial properties in CMCS-Ag and PCE significantly augment fibroblast proliferation and migration. In vivo studies further underscore its capability to expedite wound healing by absorption and expulsion of wound exudates, thereby fostering collagen deposition and vascularization. As such, this work potentially provides fresh insights into the design and fabrication of multifunctional biomimetic scaffolds, holding immense potential in the medical field for efficient wound healing.

Three-dimensional bioprinting of tissue-engineered skin: Biomaterials, fabrication techniques, challenging difficulties, and future directions: A review

As an emerging new manufacturing technology, Three-dimensional (3D) bioprinting provides the potential for the biomimetic construction of multifaceted and intricate architectures of functional integument, particularly functional biomimetic dermal structures inclusive of cutaneous appendages. Although the tissue-engineered skin with complete biological activity and physiological functions is still cannot be manufactured, it is believed that with the advances in matrix materials, molding process, and biotechnology, a new generation of physiologically active skin will be born in the future. In pursuit of furnishing readers and researchers involved in relevant research to have a systematic and comprehensive understanding of 3D printed tissue-engineered skin, this paper furnishes an exegesis on the prevailing research landscape, formidable obstacles, and forthcoming trajectories within the sphere of tissue-engineered skin, including: (1) the prevalent biomaterials (collagen, chitosan, agarose, alginate, etc.) routinely employed in tissue-engineered skin, and a discerning analysis and comparison of their respective merits, demerits, and inherent characteristics; (2) the underlying principles and distinguishing attributes of various current printing methodologies utilized in tissue-engineered skin fabrication; (3) the present research status and progression in the realm of tissue-engineered biomimetic skin; (4) meticulous scrutiny and summation of the extant research underpinning tissue-engineered skin inform the identification of prevailing challenges and issues.

Multi-functional composite dressings with sustained release of MSC-SLP and anti-adhesion property for accelerating wound healing

Exudate management is of significant clinical value for the treatment of acute wound. Various wound dressings have been developed to restore the function of injured tissues and promote wound healing, but proper exploiting the healing factors inside exudate and achieving anti-adhesion wound care remains a challenge. Herein, we present a novel multi-functional composite dressing (MCD) by coupling supernatant lyophilized powder of mesenchymal stem cells (MSC-SLP) with a sandwich-structured wound dressing (SWD). The developed MCDs demonstrated unique unidirectional drainage capability, stable anti-adhesion characteristics, and improved wound healing performance. The designed SWD with both superhydrophobic inner surface and liquid-absorption ability of mid layer enables the dressings exhibit desired anti-adhesion property to neoformative granulation tissues, favorable shielding effect to exogenous bacteria, as well as appropriate exudate-retaining capability and unidirectional exudate-absorption property. The introduction of MSC-SLP in SWD was demonstrated to further improve wound healing quality. Compared to medical gauze, the synergic effect of SWD and MSC-SLP significantly accelerates wound healing rate by over 30%, avoids tissue avulsion when changing dressings, and produces a flat-smooth closure surface. More importantly, the wound treated with MCDs presents more skin accessory organs and blood vessels in regenerated tissues than other groups. In vivo/vitro biocompatibility evaluations indicated little toxicity, demonstrating the biosecurity of the developed dressings. The proposed method offers great potential in clinical applications particularly for chronic wound treatments.

Advancements in Regenerative Hydrogels in Skin Wound Treatment: A Comprehensive Review

This state-of-the-art review explores the emerging field of regenerative hydrogels and their profound impact on the treatment of skin wounds. Regenerative hydrogels, composed mainly of water-absorbing polymers, have garnered attention in wound healing, particularly for skin wounds. Their unique properties make them well suited for tissue regeneration. Notable benefits include excellent water retention, creating a crucially moist wound environment for optimal healing, and facilitating cell migration, and proliferation. Biocompatibility is a key feature, minimizing adverse reactions and promoting the natural healing process. Acting as a supportive scaffold for cell growth, hydrogels mimic the extracellular matrix, aiding the attachment and proliferation of cells like fibroblasts and keratinocytes. Engineered for controlled drug release, hydrogels enhance wound healing by promoting angiogenesis, reducing inflammation, and preventing infection. The demonstrated acceleration of the wound healing process, particularly beneficial for chronic or impaired healing wounds, adds to their appeal. Easy application and conformity to various wound shapes make hydrogels practical, including in irregular or challenging areas. Scar minimization through tissue regeneration is crucial, especially in cosmetic and functional regions. Hydrogels contribute to pain management by creating a protective barrier, reducing friction, and fostering a soothing environment. Some hydrogels, with inherent antimicrobial properties, aid in infection prevention, which is a crucial aspect of successful wound healing. Their flexibility and ability to conform to wound contours ensure optimal tissue contact, enhancing overall treatment effectiveness. In summary, regenerative hydrogels present a promising approach for improving skin wound healing outcomes across diverse clinical scenarios. This review provides a comprehensive analysis of the benefits, mechanisms, and challenges associated with the use of regenerative hydrogels in the treatment of skin wounds. In this review, the authors likely delve into the application of rational design principles to enhance the efficacy and performance of hydrogels in promoting wound healing. Through an exploration of various methodologies and approaches, this paper is poised to highlight how these principles have been instrumental in refining the design of hydrogels, potentially revolutionizing their therapeutic potential in addressing skin wounds. By synthesizing current knowledge and highlighting potential avenues for future research, this review aims to contribute to the advancement of regenerative medicine and ultimately improve clinical outcomes for patients with skin wounds.

Immunomodulatory hydrogels for skin wound healing: cellular targets and design strategy

Skin wounds significantly impact the global health care system and represent a significant burden on the economy and society due to their complicated dynamic healing processes, wherein a series of immune events are required to coordinate normal and sequential healing phases, involving multiple immunoregulatory cells such as neutrophils, macrophages, keratinocytes, and fibroblasts, since dysfunction of these cells may impede skin wound healing presenting persisting inflammation, impaired vascularization, and excessive collagen deposition. Therefore, cellular target-based immunomodulation is promising to promote wound healing as cells are the smallest unit of life in immune response. Recently, immunomodulatory hydrogels have become an attractive avenue to promote skin wound healing. However, a detailed and comprehensive review of cellular targets and related hydrogel design strategies remains lacking. In this review, the roles of the main immunoregulatory cells participating in skin wound healing are first discussed, and then we highlight the cellular targets and state-of-the-art design strategies for immunomodulatory hydrogels based on immunoregulatory cells that cover defect, infected, diabetic, burn and tumor wounds and related scar healing. Finally, we discuss the barriers that need to be addressed and future prospects to boost the development and prosperity of immunomodulatory hydrogels.

Glycosaminoglycans' Ability to Promote Wound Healing: From Native Living Macromolecules to Artificial Biomaterials

Glycosaminoglycans (GAGs) are important for the occurrence of signaling molecules and maintenance of microenvironment within the extracellular matrix (ECM) in living tissues. GAGs and GAG-based biomaterial approaches have been widely explored to promote in situ tissue regeneration and repair by regulating the wound microenvironment, accelerating re-epithelialization, and controlling ECM remodeling. However, most approaches remain unacceptable for clinical applications. To improve insights into material design and clinical translational applications, this review highlights the innate roles and bioactive mechanisms of native GAGs during in situ wound healing and presents common GAG-based biomaterials and the adaptability of application scenarios in facilitating wound healing. Furthermore, challenges before the widespread commercialization of GAG-based biomaterials are shared, to ensure that future designed and constructed GAG-based artificial biomaterials are more likely to recapitulate the unique and tissue-specific profile of native GAG expression in human tissues. This review provides a more explicit and clear selection guide for researchers designing biomimetic materials, which will resemble or exceed their natural counterparts in certain functions, thereby suiting for specific environments or therapeutic goals.

Zirconium-Based Metal-Organic Framework Capable of Binding Proinflammatory Mediators in Hydrogel Form Promotes Wound Healing Process through a Multiscale Adsorption Mechanism

The regulation of proinflammatory mediators has been explored to promote natural healing without abnormal inflammation or autoimmune response induced by their overproduction. However, most efforts to control these mediators have relied on pharmacological substances that are directly engaged in biological cycles. It is believed that functional porous materials removing target mediators provide a new way to promote the healing process using their adsorption mechanisms. In this study, the Zr-based metal-organic frameworks (MOF)-808 (Zr6 O4 (OH)4 (BTC)2 (HCOO)6 ) crystals are found to be effective at removing proinflammatory mediators, such as nitric oxide (NO), cytokines, and reactive oxygen species (ROS) in vitro and in vivo, because of their porous structure and surface affinity. The MOF-808 crystals are applied to an in vivo skin wound model as a hydrogel dispersion. Hydrogel containing 0.2 wt% MOF-808 crystals shows significant improvement in terms of wound healing efficacy and quality over the corresponding control. It is also proven that the mode of action is to remove the proinflammatory mediators in vivo. Moreover, the application of MOF-808-containing hydrogels promotes cell activation, proliferation and inhibits chronic inflammation, leading to increased wound healing quality. These findings suggest that Zr-based MOFs may be a promising drug-free solution for skin problems related to proinflammatory mediators.

Advanced function, design and application of skin substitutes for skin regeneration

The development of skin substitutes aims to replace, mimic, or improve the functions of human skin, regenerate damaged skin tissue, and replace or enhance skin function. This includes artificial skin, scaffolds or devices designed for treatment, imitation, or improvement of skin function in wounds and injuries. Therefore, tremendous efforts have been made to develop functional skin substitutes. However, there is still few reports systematically discuss the relationship between the advanced function and design requirements. In this paper, we review the classification, functions, and design requirements of artificial skin or skin substitutes. Different manufacturing strategies for skin substitutes such as hydrogels, 3D/4D printing, electrospinning, microfluidics are summarized. This review also introduces currently available skin substitutes in clinical trials and on the market and the related regulatory requirements. Finally, the prospects and challenges of skin substitutes in the field of tissue engineering are discussed.

A carboxymethyl chitosan/oxidized hyaluronic acid composite hydrogel dressing loading with stem cell exosome for chronic inflammation wounds healing

Stem cell exosomes (Exo) play an important role in the transformation of macrophages, but the rapid clearance of Exo in vivo limits their therapeutic effects for chronic inflammation wounds healing. Here, stem cell Exo was isolated and introduced to a composite hydrogel including carboxymethyl chitosan (CMCS) and oxidized hyaluronic acid (OHA) through chemical cross-linking, which formed an Exo-loaded (CMCS/OHA/Exo) hydrogel. The CMCS/OHA/Exo hydrogel exhibited a function of Exo sustained release and an Exo protection within 6 days. This CMCS/OHA/Exo hydrogel was much better than CMCS/OHA hydrogel or Exo solution in macrophage cell phagocytosis, proliferation and migration in vitro, especially, played an obviously positive role in the transformation of macrophages compared with the reference groups. For the treatment of the chronic inflammation wounds in vivo, the CMCS/OHA/Exo hydrogel had the best results at wound heal rate and inhibiting the secretion of inflammatory factors, and it was far superior to reference groups in wound re-epithelization and collagen production. CMCS/OHA/Exo hydrogels can promote Exo release based on hydrogel degradation to regulate macrophages transformation and accelerate chronic wound healing. The study offers a method for preparing Exo-loaded hydrogels that effectively promote the transformation of macrophages and accelerate chronic inflammatory wound healing.

Evaluation of the Modification Effects of Heparin/Dalteparin on Silk Fibroin Structure and Physical Properties for Skin Wound Healing

We have developed a functionalized silk fibroin (BSF) that can serve as an improved fundamental material for dressings by specifically capturing growth factors secreted during the healing process and supplying them to cells accumulated in the wound area to enhance the tissue regeneration efficiency. When considering the design of heparin-modified BSF, there is a difficulty with binding to high-molecular-weight polysaccharides without disrupting the hydrophobic crystalline structure of the BSF. In this study, a low-molecular-weight pharmaceutical heparin, dalteparin, was selected and cross-linked with the tyrosine residue presence in the BSF non-crystalline region. When targeting 3D porous applications like nanofiber sheets, as it is crucial not only to enhance biological activity but also to improve handling by maintaining stability in water and mechanical strength, a trade-off between improved cell affinity and reduced mechanical strength depending on crystalline structure was evaluated. The use of dalteparin maintained the mechanical strength better than unfractionated heparin by reducing the effect on disturbing BSF recrystallization. Film surface hydrophilicity and cell proliferation induction were significantly higher in the dalteparin group. For BSF functionalization, using purified heparin was an effective approach that achieved a balance between preserving the mechanical properties and induction of tissue regeneration, offering the potential for various forms 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.

Designing Hydrogels for Immunomodulation in Cancer Therapy and Regenerative Medicine

The immune system not only acts as a defense against pathogen and cancer cells, but also plays an important role in homeostasis and tissue regeneration. Targeting immune systems is a promising strategy for efficient cancer treatment and regenerative medicine. Current systemic immunomodulation therapies are usually associated with low persistence time, poor targeting to action sites, and severe side effects. Due to their extracellular matrix-mimetic nature, tunable properties and diverse bioactivities, hydrogels are intriguing platforms to locally deliver immunomodulatory agents and cells, as well as provide an immunomodulatory microenvironment to recruit, activate, and expand host immune cells. In this review, the design considerations, including polymer backbones, crosslinking mechanisms, physicochemical nature, and immunomodulation-related components, of the hydrogel platforms, are focused on. The immunomodulatory effects and therapeutic outcomes in cancer therapy and tissue regeneration of different hydrogel systems are emphasized, including hydrogel depots for delivery of immunomodulatory agents, hydrogel scaffolds for cell delivery, and immunomodulatory hydrogels depending on the intrinsic properties of materials. Finally, the remained challenges in current systems and future development of immunomodulatory hydrogels are discussed.

Marine-derived polysaccharides and their therapeutic potential in wound healing application - A review

Polysaccharides originating from marine sources have been studied as potential material for use in wound dressings because of their desirable characteristics of biocompatibility, biodegradability, and low toxicity. Marine-derived polysaccharides used as wound dressing, provide several benefits such as promoting wound healing by providing a moist environment that facilitates cell migration and proliferation. They can also act as a barrier against external contaminants and provide a protective layer to prevent further damage to the wound. Research studies have shown that marine-derived polysaccharides can be used to develop different types of wound dressings such as hydrogels, films, and fibres. These dressings can be personalised to meet specific requirements based on the type and severity of the wound. For instance, hydrogels can be used for deep wounds to provide a moist environment, while films can be used for superficial wounds to provide a protective barrier. Additionally, these polysaccharides can be modified to improve their properties, such as enhancing their mechanical strength or increasing their ability to release bioactive molecules that can promote wound healing. Overall, marine-derived polysaccharides show great promise for developing effective and safe wound dressings for various wound types.