Self-assembled elastin-like polypeptide fusion protein coacervates as competitive inhibitors of advanced glycation end-products enhance diabetic wound healing

Fusion protein of FGF21 and elastin-like peptide improves wound healing in diabetic mice via inflammation modulation, collagen synthesis, and vascular network formation

Chronic-healing skin wounds are a common complication in diabetic individuals. To alleviate patient suffering, there is a pressing demand for more effective strategies to expedite the repair of diabetic wounds. Fibroblast growth factor 21(FGF21) has been proven to accelerate wound healing, but its stability and ability to assist in the healing of diabetic ulcers have not met expectations. Therefore, we have fused FGF21 with an elastin-like peptide (ELP) to create a recombinant fusion protein (abbreviated as "ELF") to increase the bioactivity and stability in vitro or in vivo. Our results demonstrated that ELF significantly improved the efficiency of FGF21 purification due to the inverse temperature responsive phase transition property of ELP. Meanwhile, the fusion strategy did not impair the structure of FGF21 or diminish its activity, as demonstrated by the highly similar secondary structure of ELF and FGF21, and their considerable inhibitory activity in the glucose consumption experiment of Huh-7 cells. An in vitro migration assay revealed that ELF promoted healing more effectively than either free FGF21 or ELP. Further in vivo study revealed the ability of ELF to improve skin wound healing quality, manifested by lower levels of inflammatory factors, more collagen formation and deposition, and the formation of robust vascular networks, though there was no significant difference in healing rate among the ELF, FGF21, and ELP groups. In conclusion, our study indicated that FGF21 and ELP fusion molecules could be developed as more efficient and cost-effective therapeutic strategies for diabetic wound healing.

Zinc-based Polyoxometalate Nanozyme Functionalized Hydrogels for optimizing the Hyperglycemic-Immune Microenvironment to Promote Diabetic Wound Regeneration

BACKGROUND

In diabetic wounds, hyperglycemia-induced cytotoxicity and impaired immune microenvironment plasticity directly hinder the wound healing process. Regulation of the hyperglycemic microenvironment and remodeling of the immune microenvironment are crucial.

RESULTS

Here, we developed a nanozymatic functionalized regenerative microenvironmental regulator (AHAMA/CS-GOx@Zn-POM) for the effective repair of diabetic wounds. This novel construct integrated an aldehyde and methacrylic anhydride-modified hyaluronic acid hydrogel (AHAMA) and chitosan nanoparticles (CS NPs) encapsulating zinc-based polymetallic oxonate nanozyme (Zn-POM) and glucose oxidase (GOx), facilitating a sustained release of release of both enzymes. The GOx catalyzed glucose to gluconic acid and (H₂O₂), thereby alleviating the effects of the hyperglycemic microenvironment on wound healing. Zn-POM exhibited catalase and superoxide dismutase activities to scavenge reactive oxygen species and H₂O₂, a by-product of glucose degradation. Additionally, Zn-POM induced M1 macrophage reprogramming to the M2 phenotype by inhibiting the MAPK/IL-17 signaling diminishing pro-inflammatory cytokines, and upregulating the expression of anti-inflammatory mediators, thus remodeling the immune microenvironment and enhancing angiogenesis and collagen regeneration within wounds. In a rat diabetic wound model, the application of AHAMA/CS-GOx@Zn-POM enhanced neovascularization and collagen deposition, accelerating the wound healing process.

CONCLUSIONS

Therefore, the regenerative microenvironment regulator AHAMA/CS-GOx@Zn-POM can achieve the effective conversion of a pathological microenvironment to regenerative microenvironment through integrated control of the hyperglycemic-immune microenvironment, offering a novel strategy for the treatment of diabetic wounds.

Blue Laser Triggered Hemostatic Peptide Hydrogel for Gastrointestinal Bleeding Treatment

In an emergency, nonvariceal upper gastrointestinal bleeding (NVUGIB), endoscopic hemostasis is considered the gold standard intervention. However, current endoscopic hemostasis is very challenging to manage bleeding in large-diameter or deep lesions highly prone to rebleeding risk. Herein, a novel hemostatic peptide hydrogel (HPH) is reported, consisting of a self-assembly peptide sequence CFLIVIGSIIVPGDGVPGDG (PFV) and gelatin methacryloyl (GelMA), which can be triggered by blue laser endoscopy (BLE) for nonvariceal upper gastrointestinal bleeding treatment without recurring bleeding concerns. Upon contact with GelMA solution, PFV immediately fibrillates into β-sheet nanofiber and solvent-induced self-assembly to form HPH gel. HPH nanofiber networks induced ultrafast coagulation by enveloping blood cells and activating platelets and coagulation factors even to the blood with coagulopathy. Besides its remarkable hemostatic performance in artery and liver injury models, HPH achieves instant bleeding management in porcine NVUGIB models within 60 s by preventing the rebleeding risk. This work demonstrates an extraordinary hemostatic agent for NVUGIB intervention by BLE for the first time, broadening potential application scenarios, including patients with coagulopathy and promising clinical prospects.

Self-Assembled Fibroblast Growth Factor Nanoparticles as a Therapeutic for Oxidant-Induced Neuronal and Skin Cell Injury

Traumatic brain injury (TBI) and spinal cord injury (SCI) are neurological conditions that result from immediate mechanical injury, as well as delayed injury caused by local inflammation. Furthermore, TBI and SCI often lead to secondary complications, including pressure wounds of the skin, which can heal slowly and are prone to infection. Pressure wounds are localized areas of damaged tissue caused by prolonged pressure on the skin due to immobility and loss of neurological sensation. With the aim to ameliorate these symptoms, we investigated whether fibroblast growth factors 2 (FGF-2) could contribute to recovery. FGF-2 plays a significant role in both neurogenesis and skin wound healing. We developed a recombinant fusion protein containing FGF-2 linked to elastin-like polypeptides (FGF-ELP) that spontaneously self-assembles into nanoparticles at around 33 °C. The nanoparticle's size was ranging between 220 and 250 nm in diameter at 2 μM. We tested this construct for its ability to address neuronal and skin cell injuries. Hydrogen peroxide was used to induce oxidant-mediated injury on cultured neuronal cells to mimic the impact of reactive oxidants released during the inflammatory response in vivo. We found that FGF-ELP nanoparticles protected against hydrogen peroxide-mediated injury and promoted neurite outgrowth. In the skin cell models, cells were depleted from serum to mimic the reduced levels of nutrients and growth factors in chronic skin wounds. FGF-ELP increased the proliferation and migration of human keratinocytes, fibroblasts, and endothelial cells. FGF-ELP is, therefore, a potentially useful agent to provide both neuroprotection and promotion of cellular processes involved in skin wound healing.

Recombinant fibrous protein biomaterials meet skin tissue engineering

Natural biomaterials, particularly fibrous proteins, are extensively utilized in skin tissue engineering. However, their application is impeded by batch-to-batch variance, limited chemical or physical versatility, and environmental concerns. Recent advancements in gene editing and fermentation technology have catalyzed the emergence of recombinant fibrous protein biomaterials, which are gaining traction in skin tissue engineering. The modular and highly customizable nature of recombinant synthesis enables precise control over biomaterial design, facilitating the incorporation of multiple functional motifs. Additionally, recombinant synthesis allows for a transition from animal-derived sources to microbial sources, thereby reducing endotoxin content and rendering recombinant fibrous protein biomaterials more amenable to scalable production and clinical use. In this review, we provide an overview of prevalent recombinant fibrous protein biomaterials (collagens, elastin, silk proteins and their chimeric derivatives) used in skin tissue engineering (STE) and compare them with their animal-derived counterparts. Furthermore, we discuss their applications in STE, along with the associated challenges and future prospects.

Exudate Unidirectional Pump to Promote Glucose Catabolism Triggering Fenton-Like Reaction for Chronic Diabetic Wounds Therapy

The massive accumulation of exudate containing high concentrations of glucose causes wound infection and triggers the release of inflammatory factors, which in turn delays the closure of diabetic wounds. In this study, a Janus membrane is constructed by combining glucose oxidase (GOx) and copper ions (Cu2+) for the treatment of diabetic wounds, which is named as Janus@GOx/Cu2+. It consists of hydrophobic, transitional, and superhydrophilic layers in a three-layer structure with gradient hydrophilicity for self-pumping properties. The Janus@GOx/Cu2+ membrane triggers a series of cascading reactions while pumping out diabetic wound exudates. First, glucose oxidase loaded onto the hydrophilic layer of the Janus@GOx/Cu2+ membrane decomposes glucose into hydrogen peroxide (H2O2) and glucuronic acid, reducing the local glucose level. The generated glucuronic acid neutralizes the local alkaline environment of chronic wounds. Simultaneously, the H2O2 interacts with the Cu2+ contained in the hydrophobic layers of the Janus@GOx/Cu2+ membrane via a Fenton-like reaction, generating hydroxyl radicals with excellent bactericidal properties. Cu2+ promotes angiogenesis and wound healing in diabetic wounds. Under the action of multiple responses, the Janus@GOx/Cu2+ membrane promotes wound healing in diabetic infections.

Engineered exosomes as a prospective therapy for diabetic foot ulcers

Diabetic foot ulcer (DFU), characterized by high recurrence rate, amputations and mortality, poses a significant challenge in diabetes management. The complex pathology involves dysregulated glucose homeostasis leading to systemic and local microenvironmental complications, including peripheral neuropathy, micro- and macro-angiopathy, recurrent infection, persistent inflammation and dysregulated re-epithelialization. Novel approaches to accelerate DFU healing are actively pursued, with a focus on utilizing exosomes. Exosomes are natural nanovesicles mediating cellular communication and containing diverse functional molecular cargos, including DNA, mRNA, microRNA (miRNA), lncRNA, proteins, lipids and metabolites. While some exosomes show promise in modulating cellular function and promoting ulcer healing, their efficacy is limited by low yield, impurities, low loading content and inadequate targeting. Engineering exosomes to enhance their curative activity represents a potentially more efficient approach for DFUs. This could facilitate focused repair and regeneration of nerves, blood vessels and soft tissue after ulcer development. This review provides an overview of DFU pathogenesis, strategies for exosome engineering and the targeted therapeutic application of engineered exosomes in addressing critical pathological changes associated with DFUs.

Combined therapeutic strategy based on blocking the deleterious effects of AGEs for accelerating diabetic wound healing

Diabetic foot ulcer is a serious complication of diabetes. Excessive accumulation of advanced glycation end products (AGEs) is one of the critical pathogenic factors in postponing diabetic wound healing. The main pathogenic mechanisms of AGEs include inducing cellular dysfunction, prolonging inflammatory response, increasing oxidative stress and reducing endogenous nitric oxide (NO) production. Combination therapy of blocking the deleterious effects of AGEs and supplementing exogenous NO is hypothesized to promote diabetic wound healing. Here, we presented nanoparticles/hydrogel composite dressings to co-delivery rosiglitazone and S-nitroso glutathione into the wound bed. The designed co-delivery system augmented the survival of fibroblasts, reduced oxidative stress levels, reversed the change of mitochondrial membrane potential and decreased the proinflammatory cytokine expression. Local sustained release of therapeutic agents significantly improved the wound healing of diabetic rats including increasing the wound closure rate, alleviating inflammation, promoting collagen fiber production and angiogenesis. Our finding indicated this local deliver strategy aimed at inhibiting the toxic effects of AGEs has great clinical potential for diabetic wound treatment.

A comparative study on the effects of human serum albumin and α-melanocyte-stimulating hormone fusion proteins on the anti-neuroinflammatory in the central nervous system of adult mice

The immunomodulatory effects of α-melanocyte stimulating hormone (α-MSH) in the central nervous system (CNS) have been investigated for forty years. The clinical applications of α-MSH are limited due to its short half-life. Our previous study has indicated that the short half-life of α-MSH can be extended by fusion with carrier human serum albumin (HSA) and this fusion protein has also retained the anti-inflammatory effect on the CNS. This improvement is still far from the clinical requirements. Thus, we expected to enhance the half-life and activity of the fusion protein by optimizing the linker peptide to get closer to clinical requirements. In a previous study, we screened out two candidates in vitro experiments with a flexible linker peptide (fusion protein with flexible linker peptide, FPFL) and a rigid linker peptide (fusion protein with rigid linker peptide, FPRL), respectively. However, it was not sure whether the anti-inflammatory effects in vitro could be reproduced in vivo. Our results show that FPRL is the best candidate with a longer half-life compared to the traditional flexible linker peptides. Meanwhile, the ability of FPRL to penetrate the blood-brain barrier (BBB) was enhanced, and the inhibition of TNF-α and IL-6 was improved. We also found that the toxicity of FPRL was decreased. All of the results suggested that trying to choose the rigid linker peptide in some fusion proteins may be a potential choice for improving the unsatisfactory characteristics.

Bioactive nanomaterials kickstart early repair processes and potentiate temporally modulated healing of healthy and diabetic wounds

Slow-healing and chronic wounds represent a major global economic and medical burden, and there is significant unmet need for novel therapies which act to both accelerate wound closure and enhance biomechanical recovery of the skin. Here, we report a new approach in which bioactives that augment early stages of wound healing can kickstart and engender effective wound closure in healthy and diabetic, obese animals, and set the stage for subsequent tissue repair processes. We demonstrate that a nanomaterial dressing made of silk fibroin and gold nanorods (GNR) stimulates a pro-neutrophilic, innate immune, and controlled inflammatory wound transcriptomic response. Further, Silk-GNR, lasered into the wound bed, in combination with exogeneous histamine, accelerates early-stage processes in tissue repair leading to effective wound closure. Silk-GNR and histamine enhanced biomechanical recovery of skin, increased transient neoangiogenesis, myofibroblast activation, epithelial-to-mesenchymal transition (EMT) of keratinocytes and a pro-resolving neutrophilic immune response, which are hitherto unknown activities for these bioactives. Predictive and temporally coordinated delivery of growth factor nanoparticles that modulate later stages of tissue repair further accelerated wound closure in healthy and diabetic, obese animals. Our approach of kickstarting healing by delivering the "right bioactive at the right time" stimulates a multifactorial, pro-reparative response by augmenting endogenous healing and immunoregulatory mechanisms and highlights new targets to promote tissue repair.

Multiple Natural Polymers in Drug and Gene Delivery Systems

Natural polymers are organic compounds produced by living organisms. In nature, they exist in three main forms, including proteins, polysaccharides, and nucleic acids. In recent years, with the continuous research on drug and gene delivery systems, scholars have found that natural polymers have promising applications in drug and gene delivery systems due to their excellent properties such as biocompatibility, biodegradability, low immunogenicity, and easy modification. However, since the structure, physicochemical properties, pharmacological properties and biological characteristics of biopolymer molecules have not yet been entirely understood, further studies are required before large-scale clinical application. This review focuses on recent advances in the representative natural polymers such as proteins (albumin, collagen, elastin), polysaccharides (chitosan, alginate, cellulose) and nucleic acids. We introduce the characteristics of various types of natural polymers, and further outline the characterization methods and delivery forms of these natural polymers. Finally, we discuss possible challenges for natural polymers in subsequent experimental studies and clinical applications. It provides an important strategy for the clinical application of natural polymers in drug and gene delivery systems.

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.

Thou shall not heal: Overcoming the non-healing behaviour of diabetic foot ulcers by engineering the inflammatory microenvironment

Diabetic foot ulcers (DFUs) are a devastating complication for diabetic patients that have debilitating effects and can ultimately lead to limb amputation. Healthy wounds progress through the phases of healing leading to tissue regeneration and restoration of the barrier function of the skin. In contrast, in diabetic patients dysregulation of these phases leads to chronic, non-healing wounds. In particular, unresolved inflammation in the DFU microenvironment has been identified as a key facet of chronic wounds in hyperglyceamic patients, as DFUs fail to progress beyond the inflammatory phase and towards resolution. Thus, control over and modulation of the inflammatory response is a promising therapeutic avenue for DFU treatment. This review discusses the current state-of-the art regarding control of the inflammatory response in the DFU microenvironment, with a specific focus on the development of biomaterials-based delivery strategies and their cargos to direct tissue regeneration in the DFU microenvironment.

The construction of elastin-like polypeptides and their applications in drug delivery system and tissue repair

Elastin-like polypeptides (ELPs) are thermally responsive biopolymers derived from natural elastin. These peptides have a low critical solution temperature phase behavior and can be used to prepare stimuli-responsive biomaterials. Through genetic engineering, biomaterials prepared from ELPs can have unique and customizable properties. By adjusting the amino acid sequence and length of ELPs, nanostructures, such as micelles and nanofibers, can be formed. Correspondingly, ELPs have been used for improving the stability and prolonging drug-release time. Furthermore, ELPs have widespread use in tissue repair due to their biocompatibility and biodegradability. Here, this review summarizes the basic property composition of ELPs and the methods for modulating their phase transition properties, discusses the application of drug delivery system and tissue repair and clarifies the current challenges and future directions of ELPs in applications.

Multifunctional Elastin-Like Polypeptide Fusion Protein Coacervates Inhibit Receptor-Mediated Proinflammatory Signals and Promote Angiogenesis in Mouse Diabetic Wounds

Objective: Chronic skin wounds are one of the most devastating complications in diabetic patients due to the formation of advanced glycation end-products (AGEs) resulting from nonenzymatic glycation of proteins and lipids in hyperglycemia. AGEs, upon binding their receptors (RAGEs), trigger proinflammatory signals that impair wound healing in diabetes and contribute to the pathology of chronic skin wounds. Approach: We previously developed a recombinant fusion protein containing the binding domain of RAGE (vRAGE) linked to elastin-like polypeptides (ELPs) that acts as a competitive inhibitor of AGEs, and another ELP fusion protein containing stromal cell-derived factor 1 (SDF1) that promotes revascularization. In this study, we report the effects of protein coacervates incorporating both vRAGE-ELP and SDF1-ELP on wound healing in an in vitro diabetes-mimicking cell culture system, and in in vivo in full-thickness wounds on diabetic mice. Results: The combination of vRAGE-ELP and SDF1-ELP increased cell metabolic activity in AGE-stimulated endothelial cells, promoted in vitro tube formation and accelerated healing in an in vitro cell migration assay. When used in a single topical application on full-thickness excisional skin wounds in diabetic mice, wound closure in the combination groups reached almost 100% on postwounding day 35, compared to 62% and 85% on the same days in animals treated with fibrin gel control and vehicle control consisting of ELP alone. Innovation: To our knowledge, this is the first study that attempts to reverse the AGE-RAGE-mediated signaling as well as to promote cell proliferation and vascularization in one single treatment. Conclusion: The codelivery of vRAGE-ELP and SDF1-ELP has potential for the treatment of diabetic wounds.

Renewable marine polysaccharides for microenvironment-responsive wound healing

Marine polysaccharides (MPs) are an eco-friendly and renewable resource with a distinctive set of biological functions and are regarded as biological materials that can be in contact with tissues and body fluids for an extended time and promote tissue or organ regeneration. Skin tissue is easily invaded by the external environment due to its softness and large surface area. However, the body's natural physiological healing process is often too slow or suffers from the incomplete restoration of skin structure and function. Functional wound dressings are crucial for skin tissue engineering. Herein, popular MPs from different sources are summarized systematically. In particular, the structure-effectiveness of MP-based wound dressings and the physiological remodeling process of different wounds are reviewed in detail. Finally, the prospect of MP-based smart wound dressings is stated in conjunction with the wound microenvironment and provides new opportunities for high-value biomedical applications of MPs.

Peptide-based coacervates in therapeutic applications

Coacervates are droplets formed by liquid‒liquid phase separation. An increasing number of studies have reported that coacervates play an important role in living cells, such as in the generation of membraneless organelles, and peptides contribute to condensate droplet formation. Peptides with versatile functional groups and special secondary structures, including α-helices, β-sheets and intrinsically disordered regions, provide novel insights into coacervation, such as biomimetic protocells, neurodegenerative diseases, modulations of signal transmission, and drug delivery systems. In this review, we introduce different types of peptide-based coacervates and the principles of their interactions. Additionally, we summarize the thermodynamic and kinetic mechanisms of peptide-based coacervates and the associated factors, including salt, pH, and temperature, affecting the phase separation process. We illustrate recent studies on modulating the functions of peptide-based coacervates applied in biological diseases. Finally, we propose their promising broad applications and describe the challenges of peptide-based coacervates in the future.

Alginate/polyvinyl alcohol films for wound healing: Advantages and challenges

The skin is the largest organ in the human body and its physical integrity must be maintained for body homeostasis and to prevent the entry of pathogenic microorganisms. Sodium alginate (SA) and polyvinyl alcohol (PVA) are two polymers widely used in films for wound dressing applications. Furthermore, blends between SA and PVA improve physical, mechanical and biological properties of the final wound healing material when compared to the individual polymers. Different drugs have been incorporated into SA/PVA-based films to improve wound healing activity. It is noteworthy that SA/PVA films can be crosslinked with Ca²⁺ or other agents, which improves physicochemical and biological properties. Thus, SA/PVA associations are promising for the biomedical field, as a potential alternative for wound treatment. This review focuses on the main techniques for obtaining SA/PVA films, their physical-chemical characterization, drug incorporation, and the advantages and challenges of these films for wound healing.

Macrophage polarization in diabetic wound healing

Impaired wound healing is one of the severe complications of diabetes. Macrophages have been shown to play a vital role in wound healing. In different wound environments, macrophages are classified into two phenotypes: classically activated macrophages and alternatively activated macrophages. Dysregulation of macrophage phenotypes leads to severely impaired wound healing in diabetes. Particularly, uncontrolled inflammation and abnormal macrophage phenotype are important reasons hindering the closure of diabetic wounds. This article reviews the functions of macrophages at various stages of wound healing, the relationship between macrophage phenotypic dysregulation and diabetic wound healing and the mechanism of macrophage polarization in diabetic wound healing. New therapeutic drugs targeting phagocyte polarization to promote the healing of diabetic wounds might provide a new strategy for treating chronic diabetic wound healing.

Antibacterial coaxial hydro-membranes accelerate diabetic wound healing by tuning surface immunomodulatory functions

Diabetic foot ulcers, typical non-healing wounds, represent a severe clinical problem. Advanced glycation end-products (AGEs), which create a prolonged pro-inflammatory micro-environment in defective sites, can be responsible for refractoriness of these ulcers. Macrophages are polarized to the M2 phenotype to facilitate the transition from a pro-inflammatory microenvironment to an anti-inflammatory microenvironment, which has been demonstrated to be an effective way to accelerate diabetic wound closure. Herein, we developed coaxial hydro-membranes mimicking the extracellular matrix structure that are capable of anti-inflammatory and antibacterial functions for diabetic wound repair. These fibrous membranes maintain a moist microenvironment to support cell proliferation. Macrophages grow in an elongated shape on the surface of the fibrous membranes. The fibrous membranes effectively impaired macrophage AGE-induced M1 polarization and induced macrophage polarization towards the M2 phenotype. The effects of the fibrous membranes on the interactions between macrophages and repair cells under a diabetic condition were also investigated. Furthermore, in vivo results from a full-thickness diabetic wound model confirmed the potential of the coaxial hydro-membranes to accelerate wound healing. This study's results indicate that the developed bioactive anti-inflammatory and antibacterial wound dressing can affect AGE-induced macrophage activation and crosstalk between macrophages and fibroblasts for treating diabetic wounds.

Effect of composite biodegradable biomaterials on wound healing in diabetes

The repair of diabetic wounds has always been a job that doctors could not tackle quickly in plastic surgery. To solve this problem, it has become an important direction to use biocompatible biodegradable biomaterials as scaffolds or dressing loaded with a variety of active substances or cells, to construct a wound repair system integrating materials, cells, and growth factors. In terms of wound healing, composite biodegradable biomaterials show strong biocompatibility and the ability to promote wound healing. This review describes the multifaceted integration of biomaterials with drugs, stem cells, and active agents. In wounds, stem cells and their secreted exosomes regulate immune responses and inflammation. They promote angiogenesis, accelerate skin cell proliferation and re-epithelialization, and regulate collagen remodeling that inhibits scar hyperplasia. In the process of continuous combination with new materials, a series of materials that can be well matched with active ingredients such as cells or drugs are derived for precise delivery and controlled release of drugs. The ultimate goal of material development is clinical transformation. At present, the types of materials for clinical application are still relatively single, and the bottleneck is that the functions of emerging materials have not yet reached a stable and effective degree. The development of biomaterials that can be further translated into clinical practice will become the focus of research.

Ceria Nanoenzyme-Based Hydrogel with Antiglycative and Antioxidative Performance for Infected Diabetic Wound Healing

Diabetic wound healing still faces a dilemma because of the hostile hyperglycemic, oxidative, and easily-infected wound microenvironment. In addition, advanced glycation end products (AGEs) further impede wound repair by altering the immunological balance. Herein, ceria nanorods with distinctive antiglycative and excellent antioxidative capacities are innovatively introduced into a self-healing and erasable hydrogel, which could reshape the wound microenvironment by expediting hemostasis, inhibiting infection, reducing AGEs, and continuously depleting reactive oxygen species. The remitted oxidative stress and glycosylation synergistically regulate inflammatory responses, and promote revascularization and extracellular matrix deposition, resulting in accelerated diabetic wound repair. This study provides a highly efficient strategy for constructing nanoenzyme-reinforced antiglycative hydrogel that regulates every wound healing stage for diabetic wound management.

Glucose and MMP-9 dual-responsive hydrogel with temperature sensitive self-adaptive shape and controlled drug release accelerates diabetic wound healing

Chronic diabetic wounds are an important healthcare challenge. High concentration glucose, high level of matrix metalloproteinase-9 (MMP-9), and long-term inflammation constitute the special wound environment of diabetic wounds. Tissue necrosis aggravates the formation of irregular wounds. All the above factors hinder the healing of chronic diabetic wounds. To solve these issues, a glucose and MMP-9 dual-response temperature-sensitive shape self-adaptive hydrogel (CBP/GMs@Cel&INS) was designed and constructed with polyvinyl alcohol (PVA) and chitosan grafted with phenylboric acid (CS-BA) by encapsulating insulin (INS) and gelatin microspheres containing celecoxib (GMs@Cel). Temperature-sensitive self-adaptive CBP/GMs@Cel&INS provides a new way to balance the fluid-like mobility (self-adapt to deep wounds quickly, approximately 37 °C) and solid-like elasticity (protect wounds against external forces, approximately 25 °C) of self-adaptive hydrogels, while simultaneously releasing insulin and celecoxib on-demand in the environment of high-level glucose and MMP-9. Moreover, CBP/GMs@Cel&INS exhibits remodeling and self-healing properties, enhanced adhesion strength (39.65 ± 6.58 kPa), down-regulates MMP-9, and promotes cell proliferation, migration, and glucose consumption. In diabetic full-thickness skin defect models, CBP/GMs@Cel&INS significantly alleviates inflammation and regulates the local high-level glucose and MMP-9 in the wounds, and promotes wound healing effectively through the synergistic effect of temperature-sensitive shape-adaptive character and the dual-responsive system.

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The hydrogel with temperature-sensitive adaptive shape can fill irregular wounds.

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The hydrogel on-demand releases drugs responding to diabetic wound environment.

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The hydrogel significantly accelerated diabetic wound healing.

Curcumin-incorporated 3D bioprinting gelatin methacryloyl hydrogel reduces reactive oxygen species-induced adipose-derived stem cell apoptosis and improves implanting survival in diabetic wounds

Background

Gelatin methacryloyl (GelMA) hydrogels loaded with stem cells have proved to be an effective clinical treatment for wound healing. Advanced glycation end product (AGE), interacting with its particular receptor (AGER), gives rise to reactive oxygen species (ROS) and apoptosis. Curcumin (Cur) has excellent antioxidant activity and regulates intracellular ROS production and apoptosis. In this study, we developed a Cur-incorporated 3D-printed GelMA to insert into adipose-derived stem cells (ADSCs) and applied it to diabetic wounds.

Methods

GelMA hydrogels with Cur were fabricated and their in vitro effects on ADSCs were investigated. We used structural characterization, western blot, ROS and apoptosis assay to evaluate the antioxidant and anti-apoptotic activity, and assessed the wound healing effects to investigate the mechanism underlying regulation of apoptosis by Cur via the AGE/AGER/nuclear factor-κB (NF-κB) p65 pathway.

Results

A 10% GelMA scaffold exhibited appropriate mechanical properties and biocompatibility for ADSCs. The circular mesh structure demonstrated printability of 10% GelMA and Cur-GelMA bioinks. The incorporation of Cur into the 10% GelMA hydrogel showed an inhibitory effect on AGEs/AGER/NF-κB p65-induced ROS generation and ADSC apoptosis. Furthermore, Cur-GelMA scaffold promoted cell survival and expedited in vivo diabetic wound healing.

Conclusions

The incorporation of Cur improved the antioxidant activity of 3D-printed GelMA hydrogel and mitigated AGE/AGER/p65 axis-induced ROS and apoptosis in ADSCs. The effects of scaffolds on wound healing suggested that Cur/GelMA-ADSC hydrogel could be an effective biological material for accelerating wound healing.

Regenerative Approaches for Chronic Wounds

Chronic skin wounds are commonly found in older individuals who have impaired circulation due to diabetes or are immobilized due to physical disability. Chronic wounds pose a severe burden to the health-care system and are likely to become increasingly prevalent in aging populations. Various treatment approaches exist to help the healing process, although the healed tissue does not generally recapitulate intact skin but rather forms a scar that has inferior mechanical properties and that lacks appendages such as hair or sweat glands. This article describes new experimental avenues for attempting to improve the regenerative response of skin using biophysical techniques as well as biochemical methods, in some cases by trying to harness the potential of stem cells, either endogenous to the host or provided exogenously, to regenerate the skin. These approaches primarily address the local wound environment and should likely be combined with other modalities to address regional and systemic disease, as well as social determinants of health. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Tandem mass tag-based serum proteomic profiling revealed diabetic foot ulcer pathogenesis and potential therapeutic targets

Diabetic foot ulcer (DFU), one of the most serious complications of diabetes mellitus, is associated with a high amputation rate and decreased life quality. The impact of blood serum proteins on the occurrence and development of DFU has attracted a lot of interest. In this study, we aimed to define and compare the serum proteome of patients with DFU and healthy control (HC) to provide new insights into DFU pathogenesis. DFU patients and age- and sex-matched HCs were enrolled in this study (n = 54). We screened alterations in blood serum proteins from DFU patients and HC using a tandem mass tag (TMT) method based on liquid chromatography-mass spectrometry (LC-MS/MS) quantitative proteomics, and the differentially expressed proteins (DEPs) were further validated by parallel reaction monitoring (PRM) and enzyme-linked immunosorbent assay (ELISA). A total of 173 DEPs (100 up-regulated and 73 down-regulated) were identified between the DFU and HC groups (P < 0.05). Proteomic and bioinformatics analyses indicated that the proteins in the DFU group were mainly related to extracellular matrix (ECM)-receptor interaction and complement and coagulation cascades. The up-regulated DEPs were further verified by PRM and ELISA. LRG1, CD5L, CRP, IGHA1, and LBP were proved upregulated in DFU and these proteins are mainly related to immune response and complement activation. Our findings help to provide a more comprehensive understanding of the pathogenesis of DFU and new insight into potential therapeutic targets.

Phenytoin-loaded bioactive nanoparticles for the treatment of diabetic pressure ulcers: formulation and in vitro/in vivo evaluation

Drug repurposing offers the chance to explore the full potential of existing drugs while reducing drug development time and costs. For instance, the anticonvulsant drug phenytoin (PHT) has been investigated for its wound healing properties. However, its poor solubility and variability of doses used topically limit its use. Hence, the aim of this study was to improve the properties and wound healing efficacy of PHT for the treatment of diabetic bedsores. PHT was encapsulated, using a modified ionic gelation method, in either positively or negatively charged chitosan-alginate nanoparticles (NPs), which possess previously demonstrated wound healing potential. These NPs were characterized by transmission electron microscopy, differential scanning calorimetry, and Fourier-transform infrared spectroscopy. PHT-loaded NPs were evaluated in vivo for their pressure ulcers' healing potential using diabetic rats. The prepared NPs, especially the positively charged particles, exhibited superior wound healing efficacy compared to PHT suspension, with respect to healing rates, granulation tissue formation, tissue maturation, and collagen content. The positively charged NPs resulted in a 56.54% wound closure at day 7, compared to 37% for PHT suspension. Moreover, skin treated with these NPs showed a mature dermis structure with skin appendages, which were absent in all other groups, in addition to the highest collagen content of 63.65%. In conclusion, the use of a bioactive carrier enhanced the healing properties of PHT and allowed the use of relatively low doses of the drug. Our findings suggest that the prepared NPs offer an effective antibiotic-free delivery system for diabetic wound healing applications.

Histology Scoring System for Murine Cutaneous Wounds

Monitoring wound progression over time is a critical aspect for studies focused on in-depth molecular analysis or on evaluating the efficacy of potential novel therapies. Histopathological analysis of wound biopsies can provide significant insight into healing dynamics, yet there is no standardized and reproducible scoring system currently available. The purpose of this study was to develop and statistically validate a scoring system based on parameters in each phase of healing that can be easily and accurately assessed using either Hematoxylin & Eosin (H&E) or Masson's Trichrome (MT) staining. These parameters included re-epithelization, epithelial thickness index, keratinization, granulation tissue thickness, remodeling, and the scar elevation index. The initial phase of the study was to (1) optimize and clarify healing parameters to limit investigator bias and variability; (2) compare the consistency of parameters assessed using H&E versus MT staining. During the validation phase of this study, the accuracy and reproducibility of this scoring system was independently iterated upon and validated in four different types of murine skin wound models (Excisional; punch biopsy; pressure ulcers; burn wounds). A total of n = 54 histology sections were randomized, blinded, and assigned to two groups of independent investigators (n = 5 per group) for analysis. The sensitivity of each parameter (ranging between 80% and 95%) is reported with illustrations on the appropriate assessment method using ImageJ software. In the validated scoring system, the lowest score (score:0) is associated with an open/unhealed wound as is evident immediately and within the first day postinjury, whereas the highest score (score:12) is associated with a completely closed and healed wound without excessive scarring. This study defines and describes the minimum recommended criteria for assessing wound healing dynamics using the SPOT skin wound score. The acronym SPOT refers to the academic and scientific institutions that were involved in the development of the scoring system, namely, Stellenbosch University, Polish Academy of Sciences, Obatala Sciences, and the University of Texas Southwestern.