Vascularized polypeptide hydrogel modulates macrophage polarization for wound healing

A matrix metalloproteinase-responsive hydrogel system controls angiogenic peptide release for repair of cerebral ischemia/reperfusion injury

JOURNAL/nrgr/04.03/01300535-202502000-00028/figure1/v/2024-05-28T214302Z/r/image-tiff Vascular endothelial growth factor and its mimic peptide KLTWQELYQLKYKGI (QK) are widely used as the most potent angiogenic factors for the treatment of multiple ischemic diseases. However, conventional topical drug delivery often results in a burst release of the drug, leading to transient retention (inefficacy) and undesirable diffusion (toxicity) in vivo. Therefore, a drug delivery system that responds to changes in the microenvironment of tissue regeneration and controls vascular endothelial growth factor release is crucial to improve the treatment of ischemic stroke. Matrix metalloproteinase-2 (MMP-2) is gradually upregulated after cerebral ischemia. Herein, vascular endothelial growth factor mimic peptide QK was self-assembled with MMP-2-cleaved peptide PLGLAG (TIMP) and customizable peptide amphiphilic (PA) molecules to construct nanofiber hydrogel PA-TIMP-QK. PA-TIMP-QK was found to control the delivery of QK by MMP-2 upregulation after cerebral ischemia/reperfusion and had a similar biological activity with vascular endothelial growth factor in vitro. The results indicated that PA-TIMP-QK promoted neuronal survival, restored local blood circulation, reduced blood-brain barrier permeability, and restored motor function. These findings suggest that the self-assembling nanofiber hydrogel PA-TIMP-QK may provide an intelligent drug delivery system that responds to the microenvironment and promotes regeneration and repair after cerebral ischemia/reperfusion injury.

Role of macrophage polarization in diabetic foot ulcer healing: A bibliometric study

BACKGROUND

Diabetic foot ulcers (DFUs) are a significant contributor to disability and mortality in diabetic patients. Macrophage polarization and functional regulation are promising areas of research and show therapeutic potential in the field of DFU healing. However, the complex mechanism, the difficulty in clinical translation, and the large heterogeneity present significant challenges. Hence, this study was to comprehensively analyze the publication status and trends of studies on macrophage polarization and DFU healing.

AIM

To examine the relevant literature on macrophage polarization in DFU healing.

METHODS

A bibliometric analysis was conducted using the Web of Science database. Relevant literature was retrieved from the Web of Science Core Collection database between 2013 to 2023 using literature visualization and analysis software (VOSviewer and CiteSpace) and bibliometric online platforms. The obtained literature was then subjected to visualization and analysis of different countries/regions, institutions, journals, authors, and keywords to reveal the research’s major trends and focus.

RESULTS

The number of publications on the role of macrophage polarization in DFU healing increased rapidly from 2013 to 2023, especially in the latter period. Chinese researchers were the most prolific in this field, with 217 publications, while American researchers had been engaged in this field for a longer period. Qian Tan of Nanjing Drum Tower Hospital and Qian Ding of Nanjing University were the first to publish in this field. Shanghai Jiao Tong University was the institution with the most publications (27). The keywords “bone marrow”, “adjustment, replacement, response, tissue repair”, and “activation, repair, differentiation” appeared more frequently. The study of macrophage polarization in DFU healing focused on the regulatory mechanism, gene expression, and other aspects.

CONCLUSION

This study through the bibliometric method reveals the research trends and development trends in this field of macrophage polarization in DFU healing from 2013 to 2023 in the Web of Science Core Collection database. The key hotspots in this field mainly include the regulation of macrophage activation, gene expression, wound tissue repair, and new wound materials. This study provides references for future research directions.

Zinc-induced photocrosslinked konjac glucomannan/glycyrrhizic acid hydrogel promotes skin wound healing in diabetic mice through immune regulation

Diabetic wound healing is a complex process. Owing to the lack of effective wound dressings, diabetic wound healing is often delayed. Here, injectable composite hydrogels with methacrylic anhydride (MA)-modified Konjac glucomannan and Zn2+-induced glycyrrhizic acid self-assembly were developed for skin wound healing in diabetic mice. Under induction with a photoinitiator and Zn2+, the hydrogel formed rapidly (<5 s) in vitro. The KGMMA/GA/Zn hydrogel demonstrated excellent mechanical properties (strain [40 %] >28 KPa) and physicochemical characteristics, which enabled the adaptation to various complex skin wound environments. Crucially, in vitro and in vivo experiments revealed that the hydrogel had good biocompatibility and low hemolytic properties (1.7 %) and promoted cell migration and tube formation. Hydrogels can modulate the innate properties of the immune system, regulate the polarization of macrophages in the M2 direction, and inhibit the production of ROS and inflammatory factors without the addition of cytokines or drugs in vivo and in vitro. In vivo animal experiments revealed that the hydrogel significantly accelerated the repair process of skin wounds, with a repair efficiency reaching 97.2 %. In summary, this novel hydrogel constitutes a highly effective wound healing dressing and may be a promising approach in tissue regeneration engineering.

Injectable and self-healing carboxymethyl chitosan/carboxymethyl cellulose/marine snail peptide hydrogel for infected wound healing

Treatment of bacterial infected full-thickness wounds remains a great challenge in clinic. Herein, a HYP hydrogel was prepared using carboxymethyl chitosan, dialdehyde carboxymethyl cellulose, and marine snail peptide (Tyr-Ile-Ala-Glu-Asp-Ala-Glu-Arg) as starting materials. The marine snail peptide with good antioxidant activity could remove the reactive oxygen species in wound sites, thereby alleviating the excessive inflammatory response. The dynamic Schiff-base bonds endowed HYP with good injectable and self-healing abilities. HYP exhibited suitable gelation time, good rheological properties, and unique porosity structure, which were conducive to wound healing. In vitro biological studies indicated that HYP showed good biocompatibility, low hemolysis ratio, and improved antibacterial and antioxidant activities. In vivo study revealed that HYP could promote wound healing in a bacterial infected full-thickness skin defect rat model. The wound tissues showed reduced number of inflammatory cells, newly formed hair follicles, and obvious collagen deposition. The expression of inflammatory and angiogenesis related biomarkers (IL-6, IL-10, CD31, and α-SMA) significantly improved. Therefore, HYP hydrogel showed great application prospect as a wound dressing for bacterial infected wound.

Chondroitin sulfate sponge scaffold for slow-release Mg2+/Cu2+ in diabetic wound management: Hemostasis, effusion absorption, and healing

The management of diabetic wounds presents significant challenges due to persistent inflammation, microenvironmental disruptions, and impaired angiogenesis. To address these issues, this study developed a multifunctional chondroitin sulfate sponge (CSP@Cu-Mg) with anti-inflammatory properties, hemostatic effects, effusion absorption, and enhanced healing promotion. Through ion crosslinking, MgO and CuO were incorporated into the interpenetrating network structure of chondroitin sulfate and acellular dermal matrix, resulting in a sponge with impressive liquid absorption capacity (3450 %) and porosity (83 %). This sponge enabled sustained release of Mg2+/Cu2+ ions, with approximately 40 % cumulative release over 7 days. This release helped reduce inflammation, promote the proliferation and migration of skin repair-related cells, and stimulate angiogenesis. In vivo studies demonstrated that the CSP@Cu-Mg sponge significantly improved diabetic wound healing by modulating inflammation and accelerating collagen deposition, angiogenesis, and re-epithelialization. This extracellular matrix sponge, which synergistically releases Mg2+/Cu2+, presents a promising strategy for comprehensive diabetic wound management with substantial clinical implications.

Design and Applications of Supramolecular Peptide Hydrogel as Artificial Extracellular Matrix

Supramolecular peptide hydrogels (SPHs) consist of peptides containing hydrogelators and functional epitopes, which can first self-assemble into nanofibers and then physically entangle together to form dynamic three-dimensional networks. Their porous structures, excellent bioactivity, and high dynamicity, similar to an extracellular matrix (ECM), have great potential in artificial ECM. The properties of the hydrogel are largely dependent on peptides. The noncovalent interactions among hydrogelators drive the formation of assemblies and further transition into hydrogels, while bioactive epitopes modulate cell-cell and cell-ECM interactions. Therefore, SPHs can support cell growth, making them ideal biomaterials for ECM mimics. This Review outlines the classical molecular design of SPHs from hydrogelators to functional epitopes and summarizes the recent advancements of SPHs as artificial ECMs in nervous system repair, wound healing, bone and cartilage regeneration, and organoid culture. This emerging SPH platform could provide an alternative strategy for developing more effective biomaterials for tissue engineering.

Extraction and Structural Characterization of Four Grape Polysaccharides and Their Protective Effects in Alcohol-Induced Gastric Mucosal Injury

Grapes, recognized as a nutritionally rich fruit, have been found through extensive research to contain various bioactive components. However, the roles of polysaccharides and their bioactive properties remain unclear. Based on this, in our research, four different grape polysaccharides were obtained using an enzymatic-assisted extraction method. We investigated and compared their physicochemical properties, antioxidant activities, and protective effects on gastric mucosa in mice. The results indicated that the monosaccharide compositions of these specific grape polysaccharides were similar; however, their molar ratios, molecular weights, and morphological characteristics varied. The results of radical scavenging tests revealed that red-fleshed grape polysaccharide (RFP) exhibited superior antioxidant properties. In vivo assessments demonstrated that RFP protects against gastric mucosal injury in mice by inhibiting inflammation and radical generation. Therefore, the polysaccharide from red-fleshed grape holds potential application value in the pharmaceutical and food industries.

Photo-Crosslinked Pro-Angiogenic Hydrogel Dressing for Wound Healing

Severe burns are one of the most devastating injuries, in which sustained inflammation and ischemia often delay the healing process. Pro-angiogenic growth factors such as vascular endothelial growth factor (VEGF) have been widely studied for promoting wound healing. However, the short half-life and instability of VEGF limit its clinical applications. In this study, we develop a photo-crosslinked hydrogel wound dressing from methacrylate hyaluronic acid (MeHA) bonded with a pro-angiogenic prominin-1-binding peptide (PR1P). The materials were extruded in wound bed and in situ formed a wound dressing via exposure to short-time ultraviolet radiation. The study shows that the PR1P-bonded hydrogel significantly improves VEGF recruitment, tubular formation, and cell migration in vitro. Swelling, Scanning Electron Microscope, and mechanical tests indicate the peptide does not affect the overall mechanical and physical properties of the hydrogels. For in vivo studies, the PR1P-bonded hydrogel dressing enhances neovascularization and accelerates wound closure in both deep second-degree burn and full-thickness excisional wound models. The Western blot assay shows such benefits can be related to the activation of the VEGF-Akt signaling pathway. These results suggest this photo-crosslinked hydrogel dressing efficiently promotes VEGF recruitment and angiogenesis in skin regeneration, indicating its potential for clinical applications in wound healing.

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.

Advances and applications of biomimetic biomaterials for endogenous skin regeneration

Endogenous regeneration is becoming an increasingly important strategy for wound healing as it facilitates skin's own regenerative potential for self-healing, thereby avoiding the risks of immune rejection and exogenous infection. However, currently applied biomaterials for inducing endogenous skin regeneration are simplistic in their structure and function, lacking the ability to accurately mimic the intricate tissue structure and regulate the disordered microenvironment. Novel biomimetic biomaterials with precise structure, chemical composition, and biophysical properties offer a promising avenue for achieving perfect endogenous skin regeneration. Here, we outline the recent advances in biomimetic materials induced endogenous skin regeneration from the aspects of structural and functional mimicry, physiological process regulation, and biophysical property design. Furthermore, novel techniques including in situ reprograming, flexible electronic skin, artificial intelligence, single-cell sequencing, and spatial transcriptomics, which have potential to contribute to the development of biomimetic biomaterials are highlighted. Finally, the prospects and challenges of further research and application of biomimetic biomaterials are discussed. This review provides reference to address the clinical problems of rapid and high-quality skin regeneration.

Polymeric silk fibroin hydrogel as a conductive and multifunctional adhesive for durable skin and epidermal electronics

Silk fibroin (SF)-based hydrogels are promising multifunctional adhesive candidates for real-world applications in tissue engineering, implantable bioelectronics, artificial muscles, and artificial skin. However, developing conductive SF-based hydrogels that are suitable for the micro-physiological environment and maintain their physical and chemical properties over long periods of use remains challenging. Herein, we developed an ion-conductive SF hydrogel composed of glycidyl methacrylate silk fibroin (SilMA) and bioionic liquid choline acylate (ChoA) polymer chains, together with the modification of acrylated thymine (ThyA) and adenine (AdeA) functional groups. The resulting polymeric ion-conductive SF composite hydrogel demonstrated high bioactivity, strong adhesion strength, good mechanical compliance, and stretchability. The formed hydrogel network of ChoA chains can coordinate with the ionic strength in the micro-physiological environment while maintaining the adaptive coefficient of expansion and stable mechanical properties. These features help to form a stable ion-conducting channel for the hydrogel. Additionally, the hydrogel network modified with AdeA and ThyA, can provide a strong adhesion to the surface of a variety of substrates, including wet tissue through abundant hydrogen bonding. The biocompatible and ionic conductive SF composite hydrogels can be easily prepared and incorporated into flexible skin or epidermal sensing devices. Therefore, our polymeric SF-based hydrogel has great potential and wide application to be an important component of many flexible electronic devices for personalized healthcare.

D-Peptide cell culture scaffolds with enhanced antibacterial and controllable release properties

The development of peptide-based hydrogels characterized by both high biostability and potent antimicrobial activity, aimed at combating multidrug-resistant bacterial infections and providing scaffolds for cell cultures, continues to pose a significant challenge. The susceptibility of antimicrobial peptides (AMPs) to degradation by cations, serum, and proteases restricted their applications in clinical environments. In this study, we designed a peptide sequence (termed D-IK1) entirely consisting of D-amino acids, an enantiomer of a previously reported AMP IK1. Our results demonstrated remarkably improved antibacterial and anticancer activities of D-IK1 as compared to IK1. D-IK1 self-assembled into hydrogels that effectively inhibited bacterial and cancer cell growth by the controlled and sustained release of D-IK1. Importantly, D-IK1 was extremely stable in salt solutions and resisted serum and protease degradation. In addition, the D-IK1 hydrogel fostered cell adhesion and proliferation, proving its viability as a 3D scaffold for cell culture applications. Our research presents a versatile, highly stable antibacterial hydrogel scaffold with potential widespread applications in cell culture, wound healing, and the eradication of multidrug-resistant bacterial infections.

Macrophage plasticity: signaling pathways, tissue repair, and regeneration

Macrophages are versatile immune cells with remarkable plasticity, enabling them to adapt to diverse tissue microenvironments and perform various functions. Traditionally categorized into classically activated (M1) and alternatively activated (M2) phenotypes, recent advances have revealed a spectrum of macrophage activation states that extend beyond this dichotomy. The complex interplay of signaling pathways, transcriptional regulators, and epigenetic modifications orchestrates macrophage polarization, allowing them to respond to various stimuli dynamically. Here, we provide a comprehensive overview of the signaling cascades governing macrophage plasticity, focusing on the roles of Toll-like receptors, signal transducer and activator of transcription proteins, nuclear receptors, and microRNAs. We also discuss the emerging concepts of macrophage metabolic reprogramming and trained immunity, contributing to their functional adaptability. Macrophage plasticity plays a pivotal role in tissue repair and regeneration, with macrophages coordinating inflammation, angiogenesis, and matrix remodeling to restore tissue homeostasis. By harnessing the potential of macrophage plasticity, novel therapeutic strategies targeting macrophage polarization could be developed for various diseases, including chronic wounds, fibrotic disorders, and inflammatory conditions. Ultimately, a deeper understanding of the molecular mechanisms underpinning macrophage plasticity will pave the way for innovative regenerative medicine and tissue engineering approaches.

Integrating Bioactive Graded Hydrogel with Radially Aligned Nanofibers to Dynamically Manipulate Wound Healing Process

Skin wound healing is a complex process that requires appropriate treatment and management. Using a single scaffold to dynamically manipulate angiogenesis, cell migration and proliferation, and tissue reconstruction during skin wound healing is a great challenge. We developed a hybrid scaffold platform that integrates the spatiotemporal delivery of bioactive cues with topographical cues to dynamically manipulate the wound-healing process. The scaffold comprised gelatin methacryloyl hydrogels and electrospun poly(ε-caprolactone)/gelatin nanofibers. The hydrogels had graded cross-linking densities and were loaded with two different functional bioactive peptides. The nanofibers comprised a radially aligned nanofiber array layer and a layer of random fibers. During the early stages of wound healing, the KLTWQELYQLKYKGI peptide, which mimics vascular endothelial growth factor, was released from the inner layer of the hydrogel to accelerate angiogenesis. During the later stages of wound healing, the IKVAVS peptide, which promotes cell migration, synergized with the radially aligned nanofiber membrane to promote cell migration, while the nanofiber membrane also supported further cell proliferation. In an in vivo rat skin wound-healing model, the hybrid scaffold significantly accelerated wound healing and collagen deposition, and the ratio of type I to type III collagen at the wound site resembled that of normal skin. The prepared scaffold dynamically regulated the skin tissue regeneration process in stages to achieve rapid wound repair with clinical application potential, providing a strategy for skin wound repair.

Harnessing the potential of hydrogels for advanced therapeutic applications: current achievements and future directions

The applications of hydrogels have expanded significantly due to their versatile, highly tunable properties and breakthroughs in biomaterial technologies. In this review, we cover the major achievements and the potential of hydrogels in therapeutic applications, focusing primarily on two areas: emerging cell-based therapies and promising non-cell therapeutic modalities. Within the context of cell therapy, we discuss the capacity of hydrogels to overcome the existing translational challenges faced by mainstream cell therapy paradigms, provide a detailed discussion on the advantages and principal design considerations of hydrogels for boosting the efficacy of cell therapy, as well as list specific examples of their applications in different disease scenarios. We then explore the potential of hydrogels in drug delivery, physical intervention therapies, and other non-cell therapeutic areas (e.g., bioadhesives, artificial tissues, and biosensors), emphasizing their utility beyond mere delivery vehicles. Additionally, we complement our discussion on the latest progress and challenges in the clinical application of hydrogels and outline future research directions, particularly in terms of integration with advanced biomanufacturing technologies. This review aims to present a comprehensive view and critical insights into the design and selection of hydrogels for both cell therapy and non-cell therapies, tailored to meet the therapeutic requirements of diverse diseases and situations.

Modulating the immune system towards a functional chronic wound healing: A biomaterials and Nanomedicine perspective

Chronic non-healing wounds persist as a substantial burden for healthcare systems, influenced by factors such as aging, diabetes, and obesity. In contrast to the traditionally pro-regenerative emphasis of therapies, the recognition of the immune system integral role in wound healing has significantly grown, instigating an approach shift towards immunological processes. Thus, this review explores the wound healing process, highlighting the engagement of the immune system, and delving into the behaviors of innate and adaptive immune cells in chronic wound scenarios. Moreover, the article investigates biomaterial-based strategies for the modulation of the immune system, elucidating how the adjustment of their physicochemical properties or their synergistic combination with other agents such as drugs, proteins or mesenchymal stromal cells can effectively modulate the behaviors of different immune cells. Finally this review explores various strategies based on synthetic and biological nanostructures, including extracellular vesicles, to finely tune the immune system as natural immunomodulators or therapeutic nanocarriers with promising biophysical properties.

A critical overview of challenging roles of medicinal plants in improvement of wound healing technology

PURPOSE

Chronic diseases often hinder the natural healing process, making wound infections a prevalent clinical concern. In severe cases, complications can arise, potentially leading to fatal outcomes. While allopathic treatments offer numerous options for wound repair and management, the enduring popularity of herbal medications may be attributed to their perceived minimal side effects. Hence, this review aims to investigate the potential of herbal remedies in efficiently treating wounds, presenting a promising alternative for consideration.

METHODS

A literature search was done including research, reviews, systematic literature review, meta-analysis, and clinical trials considered. Search engines such as Pubmed, Google Scholar, and Scopus were used while retrieving data. Keywords like Wound healing 'Wound healing and herbal combinations', 'Herbal wound dressing', Nanotechnology and Wound dressing were used.

RESULT

This review provides valuable insights into the role of natural products and technology-based formulations in the treatment of wound infections. It evaluates the use of herbal remedies as an effective approach. Various active principles from herbs, categorized as flavonoids, glycosides, saponins, and phenolic compounds, have shown effectiveness in promoting wound closure. A multitude of herbal remedies have demonstrated significant efficacy in wound management, offering an additional avenue for care. The review encompasses a total of 72 studies, involving 127 distinct herbs (excluding any common herbs shared between studies), primarily belonging to the families Asteraceae, Fabaceae, and Apiaceae. In research, rat models were predominantly utilized to assess wound healing activities. Furthermore, advancements in herbal-based formulations using nanotechnology-based wound dressing materials, such as nanofibers, nanoemulsions, nanofiber mats, polymeric fibers, and hydrogel-based microneedles, are underway. These innovations aim to enhance targeted drug delivery and expedite recovery. Several clinical-based experimental studies have already been documented, evaluating the efficacy of various natural products for wound care and management. This signifies a promising direction in the field of wound treatment.

CONCLUSION

In recent years, scientists have increasingly utilized evidence-based medicine and advanced scientific techniques to validate the efficacy of herbal medicines and delve into the underlying mechanisms of their actions. However, there remains a critical need for further research to thoroughly understand how isolated chemicals extracted from herbs contribute to the healing process of intricate wounds, which may have life-threatening consequences. This ongoing research endeavor holds great promise in not only advancing our understanding but also in the development of innovative formulations that expedite the recovery process.

Facile preparation of highly adhesive yet ultra-strong poly (vinyl alcohol)/cellulose nanocrystals composite hydrogel enabled by multiple networks structure

Poly (vinyl alcohol) (PVA) hydrogel showed potential applications in bioengineering and wearable sensors fields. It is still a huge challenge to prepare highly adhesive yet strong poly (vinyl alcohol) hydrogel with good biocompatibility. Herein, we prepared a highly self-adhesive and strong poly (vinyl alcohol)/tannic acid@cellulose nanocrystals (PVA/TA@CNCs) composite hydrogel using TA@CNCs as functional nanofiller via facile freezing-thawing method. Multiple networks consisting of hydrogen bonding and coordination interactions endowed the hydrogel with high mechanical strength, excellent flexibility and fracture toughness with adequate energy dissipation mechanism and relatively dense network structure. The tensile strength of PVA/TA@CNCs hydrogel reached the maximum of 463 kPa, increasing by 367 % in comparison with pure PVA hydrogel (99 kPa), demonstrating the synergistic reinforcing and toughening effect of TA@CNCs. The hydrogel exhibited extremely high adhesion not only for various dry and wet substrates such as plastic, metal, Teflon, rubber, glass, leaf, but also sweaty human skin, showing good adhesion durability. The highest adhesion strength to silicone rubber, steel plate and pigskin could reach 197 kPa, 100 kPa and 46.9 kPa, respectively. Meanwhile the hydrogel had negligible cytotoxicity to cells and showed good biocompatibility.

Extracellular matrix-mimetic immunomodulatory fibrous scaffold based on a peony stamens polysaccharide for accelerated wound healing

Re-establishment of the extracellular matrix (ECM) in wound tissue is critical for activating endogenous tissue repair. In this study, we designed an ECM-like scaffold material using plant polysaccharides and assessed its efficacy through in vitro and in vivo experiments. The scaffold accelerates wound healing by regulating inflammatory responses and accelerating tissue regeneration. Briefly, we isolated two polysaccharides of varying molecular weights from peony stamens. One of the polysaccharides exhibits potent immunomodulatory and tissue regeneration activities. We further prepared electrospinning materials containing this polysaccharide. In vitro investigations have demonstrated the polysaccharide's ability to modulate immune responses by targeting TLR receptors. In vivo experiments utilizing a scaffold composed of this polysaccharide showed accelerated healing of full-thickness skin wounds in mice, promoting rapid tissue regeneration. In conclusion, our study shows that this scaffold can mobilize the endogenous regenerative capacity of tissues to accelerate repair by mimicking the characteristics of ECM. The overall study has implications for the design of new, effective, and safer tissue regeneration strategies.

Biophysical Control of the Glioblastoma Immunosuppressive Microenvironment: Opportunities for Immunotherapy

GBM is the most aggressive and common form of primary brain cancer with a dismal prognosis. Current GBM treatments have not improved patient survival, due to the propensity for tumor cell adaptation and immune evasion, leading to a persistent progression of the disease. In recent years, the tumor microenvironment (TME) has been identified as a critical regulator of these pro-tumorigenic changes, providing a complex array of biomolecular and biophysical signals that facilitate evasion strategies by modulating tumor cells, stromal cells, and immune populations. Efforts to unravel these complex TME interactions are necessary to improve GBM therapy. Immunotherapy is a promising treatment strategy that utilizes a patient's own immune system for tumor eradication and has exhibited exciting results in many cancer types; however, the highly immunosuppressive interactions between the immune cell populations and the GBM TME continue to present challenges. In order to elucidate these interactions, novel bioengineering models are being employed to decipher the mechanisms of immunologically "cold" GBMs. Additionally, these data are being leveraged to develop cell engineering strategies to bolster immunotherapy efficacy. This review presents an in-depth analysis of the biophysical interactions of the GBM TME and immune cell populations as well as the systems used to elucidate the underlying immunosuppressive mechanisms for improving current therapies.

Electrospun fibers based anisotropic silk fibroin film with photodynamic antibacterial therapy for S. aureus infected wound healing

Bacterial infection has been regarded as a life-threatening problem in clinic. In addition to screening of new antibiotics, it is important to develop highly effective antibacterial materials against antibiotic resistance with capacities on modulating chronic inflammation. Herein, aligned Chlorin e6 (Ce6) conjugated silk fibroin electrospun fibers were successfully fabricated on silk fibroin based film via electrospining to achieve effective photodynamic antibacterial activities under near infrared (NIR) irradiation. The aligned electrospun fiber based film composite (SFCF@Film) exhibited good mechanical properties and desirable hemocompatibility. SFCF@Film provided a promising guidance cue for directing cell orientation and promoting cell growth. Significantly, SFCF@Film effectively generated ROS under NIR irradiation to kill S. aureus for treating wound infections within 10 min and promoted M2 polarization of macrophages for wound healing at later stage. Therefore, we believed that this engineered bioscaffold can be a powerful strategy for handling wound infection.

Body temperature-induced adhesive hyaluronate/gelatin-based hybrid hydrogel dressing for promoting skin regeneration

Skin wound management faces significant clinical challenges, including continuous bacterial infection and inflammation. Therefore, developing removable hydrogel dressings with intrinsic multifunctional properties is highly desirable. In this study, a body temperature-induced adhesive and removable hydrogel was designed to treat skin defect wounds. The HA/Gel-R-Ag hybrid gel was prepared by incorporating a silver ion-crosslinked sulfhydryl hyaluronate/gelatin-based polymeric gel network into a supramolecular rhein gel network, thereby significantly enhancing its mechanical properties. Temperature-responsive gelatin chains give the hybrid gel reversible tissue adhesiveness and detachment, thus avoiding secondary injury to wounds when changing the hydrogels. The hybrid gel exhibited excellent bactericidal ability owing to the antibacterial capacity of the silver ions and rhein. Moreover, both HA and rhein endowed the hybrid gel with immunoregulatory effects by promoting macrophage polarization from pro-inflammatory M1 phenotype to anti-inflammatory M2 phenotype. In a full-thickness skin defect mouse mode, this porous, degradable, and biocompatible HA/Gel-R-Ag hybrid gel boosted skin regeneration by inhibiting inflammation and promoting collagen deposition and angiogenesis. It is thus a simple method for widening the application range of mechanically weak rhein gels and providing a promising wound dressing material with multiple intrinsic functions for treating skin wounds.

Photopolymerizable, immunomodulatory hydrogels of gelatin methacryloyl and carboxymethyl chitosan as all-in-one strategic dressing for wound healing

Microenvironment regeneration in wound tissue is crucial for wound healing. However, achieving desirable wound microenvironment regeneration involves multiple stages, including hemostasis, inflammation, proliferation, and remodeling. Traditional wound dressings face challenges in fully manipulating all these stages to achieve quick and complete wound healing. Herein, we present a VEGF-loaded, versatile wound dressing hydrogel based on gelatin methacryloyl (GelMA) and carboxymethyl chitosan (CMCS), which could be easily fabricated using UV irradiation. The newly designed GelMA-CMCS@VEGF hydrogel not only exhibited strong tissue adhesion capacity due to the interactions between CMCS active groups and biological tissues, but also possessed desirable extensible properties for frequently moving skins and joints. Furthermore, the hydrogel demonstrates exceptional abilities in blood cell coagulation, hemostasis and cell recruitment, leading to the promotion of endothelial cells proliferation, adhesion, migration and angiogenesis. Additionally, in vivo studies demonstrated that the hydrogel drastically shortened hemostatic time, and achieved satisfactory therapeutic efficacy by suppressing inflammation, modulating M1/M2 polarization of macrophages, significantly promoting collagen deposition, stimulating angiogenesis, epithelialization and tissue remodeling. This work contributes to the design of versatile hydrogel dressings for rapid and complete wound healing therapy.

A Biodegradable High-Performance Microsupercapacitor for Environmentally Friendly and Biocompatible Energy Storage

Biodegradable and biocompatible microscale energy storage devices are very crucial for environmentally friendly microelectronics and implantable medical applications. Herein, a biodegradable and biocompatible microsupercapacitor (BB-MSC) with satisfying overall performance is realized via the combination of three-dimensional (3D) printing technique and biodegradable materials. Due to the 3D-interconnected structure of electrodes and elaborated design of electrolyte, the as-prepared BB-MSC exhibits superior overall performance than most of biodegradable devices, including a wide operation voltage of 1.8 V, high areal specific capacitance of 251 mF/cm2, good cycle stability, and favorable low-temperature resistance (-20 °C), demonstrative of reliability and practicality of our devices even in frosty environments. Importantly, the smooth degradation has been realized for the BB-MSC after being buried in natural soil for ∼90 days, and its implantation does not affect the healthy status of SD rats. Therefore, this work explores avenues for the design and construction of environmentally friendly and biocompatible microscale energy storage devices.

Applications of Silk Fibroin in Human and Veterinary Medicine

The properties of silk make it a promising material for medical applications, both in human and veterinary medicine. Its predominant amino acids, glycine and alanine, exhibit low chemical reactivity, reducing the risk of graft rejection, a notable advantage over most synthetic polymers. Hence, silk is increasingly used as a material for 3D printing in biomedicine. It can be used to build cell scaffolding with the desired cytocompatibility and biodegradability. In combination with gelatine, silk can be used in the treatment of arthritis, and as a hydrogel, to regenerate chondrocytes and mesenchymal cells. When combined with gelatine and collagen, it can also make skin grafts and regenerate the integumentary system. In the treatment of bone tissue, it can be used in combination with polylactic acid and hydroxyapatite to produce bone clips having good mechanical properties and high immunological tolerance. Furthermore, silk can provide a good microenvironment for the proliferation of bone marrow stem cells. Moreover, research is underway to produce artificial blood vessels using silk in combination with glycidyl methacrylate. Silk vascular grafts have demonstrated a high degree of patency and a satisfactory degree of endothelial cells coverage.

Recent advances in immunomodulatory hydrogels biomaterials for bone tissue regeneration

There is a high incidence of fractures in clinical practice and therapy. The repairment of critical size defects in the skeletal system remains a huge challenge for surgeons and researchers, which can be overcame by the application of bone tissue-engineered biomaterials. An increasing number of investigations have revealed that the immune system plays a vital role in the repair of bone defects, especially macrophages, which can modulate the integration of biomaterials and bone regeneration in multiple ways. Therefore, it has become increasingly important in regenerative medicine to regulate macrophage polarization to prevent inflammation caused by biomaterial implantation. Recent studies have stressed the importance of hydrogel-based modifications and the incorporation of various cellular and molecular signals for regulating immune responses to promote bone tissue regeneration and integrate biomaterials. In this review, we first elaborate briefly on the described the general physiological mechanism and process of bone tissue regeneration. Then, we summarized the immunomodulatory role macrophages play in bone repair. In addition, the role of hydrogel-based immune modification targeting macrophage modulation in accelerating and enhancing bone tissue regeneration was also discussed. Finally, we highlighted future directions and research strategies related to hydrogel optimization for the regulation of the immune response during bone regeneration and healing.

Microenvironment-responsive Cu-phenolic networks coated nanofibrous dressing with timely macrophage phenotype transition for chronic MRSA infected wound healing

Methicillin-resistant Staphylococcus aureus (MRSA) infection is a pressing clinical issue that impedes wound healing. Pro-inflammatory M1 macrophages is required to clear bacteria and recruit various cell types during the initial phase of wound healing, but timing of this process is crucial. Herein, a microenvironment-responsive nanofibrous dressing capable of timely macrophage phenotype transition in vivo is constructed by coating copper ions (Cu2+)-polydopamine (PDA) networks on poly (ε-caprolactone) fiber (PCL-fiber) membrane. During the initial post-implantation period, the nanofibrous dressing show pH-sensitive Cu2+ release in the acidic infection microenvironment. The release Cu2+ have a direct killing effect on MRSA, and promote the proinflammatory M1 phenotype of macrophages to enhance the antibacterial macrophage response. Later, PDA to become a reactive oxygen species (ROS) scavenger when in microenvironments with elevated ROS levels, which conferred the dressing with an immunomodulatory activity that convert M1 macrophages into M2 macrophages. In vivo examination in an MRSA infected full-thickness skin wounds of rat model demonstrates that this dressing significantly facilitated infection eradication and wound healing through modulating local inflammatory phenotype. Overall, this study offers a simple and effective approach for timely manipulation of inflammation progression to promote infected wound healing.

Double-network hydrogel enhanced by SS31-loaded mesoporous polydopamine nanoparticles: Symphonic collaboration of near-infrared photothermal antibacterial effect and mitochondrial maintenance for full-thickness wound healing in diabetes mellitus

Diabetic wound healing has become a serious healthcare challenge. The high-glucose environment leads to persistent bacterial infection and mitochondrial dysfunction, resulting in chronic inflammation, abnormal vascular function, and tissue necrosis. To solve these issues, we developed a double-network hydrogel, constructed with pluronic F127 diacrylate (F127DA) and hyaluronic acid methacrylate (HAMA), and enhanced by SS31-loaded mesoporous polydopamine nanoparticles (MPDA NPs). As components, SS31, a mitochondria-targeted peptide, maintains mitochondrial function, reduces mitochondrial reactive oxygen species (ROS) and thus regulates macrophage polarization, as well as promoting cell proliferation and migration, while MPDA NPs not only scavenge ROS and exert an anti-bacterial effect by photothermal treatment under near-infrared light irradiation, but also control release of SS31 in response to ROS. This F127DA/HAMA-MPDA@SS31 (FH-M@S) hydrogel has characteristics of adhesion, superior biocompatibility and mechanical properties which can adapt to irregular wounds at different body sites and provide sustained release of MPDA@SS31 (M@S) NPs. In addition, in a diabetic rat full thickness skin defect model, the FH-M@S hydrogel promoted macrophage M2 polarization, collagen deposition, neovascularization and wound healing. Therefore, the FH-M@S hydrogel exhibits promising therapeutic potential for skin regeneration.

Injectable hydrogel encapsulated with VEGF-mimetic peptide-loaded nanoliposomes promotes peripheral nerve repair in vivo

Repair of peripheral nerve crush injury remains a major clinical challenge. Currently, oral or intravenous neurotrophic drugs are the main treatment for peripheral nerve crush injury; however, this repair process is slow, and the final effect may be uncertain. The current study aimed at developing an injectable hydrogel with vascular endothelial growth factor (VEGF)-mimetic peptide (QK)-encapsulated nanoliposomes (QK-NLs@Gel) for sustainable drug release that creates an appropriate microenvironment for nerve regeneration. The QK-encapsulated nanoliposomes (QK-NLs) could facilitate the proliferation, migration, and tube formation capacities of human umbilical vein endothelial cells through the VEGF signaling pathway. The QK-NLs@Gel hydrogel encapsulated with QK-NLs showed enhanced physical properties and appropriate biocompatibility in vitro. Thereafter, the QK-NLs@Gel hydrogel was directly injected into the site of peripheral nerve crush injury in a rat model, where it enhanced revascularization and promoted the M2-polarization of the macrophages, thus providing an optimized microenvironment for nerve regeneration. At four weeks post-surgery, the QK-NLs@Gel injected rats exhibited enhanced axon regeneration, remyelination, and better functional recovery in comparison with other groups in vivo. Overall, these findings demonstrate that the composite hydrogel could promote a multicellular pro-regenerative microenvironment at the peripheral nerve injury site, thus revealing great potential for peripheral nerve restoration. STATEMENT OF SIGNIFICANCE: Peripheral nerve injury (PNI) is a leading public health issue, and how to delivery beneficial drugs to injured sites efficiently is still a big challenge. In the current study, an injectable hydrogel with VEGF-mimetic peptide (QK)-encapsulated nanoliposomes (QK-NLs@Gel) was first developed and used to repair a rat crush injury model. Our results showed that QK-NLs promoted the proliferation, migration, and angiogenesis of HUVEC via VEGF signaling pathway in vitro. Furthermore, when injected to the crushed sites in vivo, the QK-NLs@Gel hydrogel could accelerate nerve repair through enhanced revascularization and M2-polarization of macrophages. These results collectively demonstrate that injection of QK-NLs@Gel hydrogel could create an appropriate microenvironment for peripheral nerve regeneration. This strategy is effective, economical, and convenient for clinical applications.

The contribution of immunohistochemistry to the development of hydrogels for skin repair and regeneration

Hydrogels based on various polymeric materials have been successfully developed in recent years for a variety of skin applications. Several studies have shown that hydrogels with regenerative, antibacterial, and antiinflammatory properties can provide faster and better healing outcomes, particularly in chronic diseases where the normal physiological healing process is significantly hampered. Various experimental tests are typically performed to assess these materials' ability to promote angiogenesis, re-epithelialization, and the production and maturation of new extracellular matrix. Immunohistochemistry is important in this context because it allows for the visualization of in situ target tissue factors involved in the various stages of wound healing using antibodies labelled with specific markers detectable with different microscopy techniques. This review provides an overview of the various immunohistochemical techniques that have been used in recent years to investigate the efficacy of various types of hydrogels in assisting skin healing processes. The large number of scientific articles published demonstrates immunohistochemistry's significant contribution to the development of engineered biomaterials suitable for treating skin injuries.