In situ forming and reactive oxygen species-scavenging gelatin hydrogels for enhancing wound healing efficacy

Recapitulating Antioxidant and Antibacterial Compounds into a Package for Tissue Regeneration: Dual Function Materials with Synergistic Effect

Oxidative damage and infection can prevent or delay tissue repair. Moreover, infection reinforces reactive oxygen species (ROS) formation, which makes the wound's condition even worse. Therefore, the need for antioxidant and antibacterial agents is felt for tissue regeneration. There are emerging up-and-coming biomaterials that recapitulate both properties into a package, offering an effective solution to turn the wound back into a healing state. In this article, the principles of antioxidant and antibacterial activity are summarized. The review starts with biological aspects, getting the readers to familiarize themselves with tissue barriers against infection. This is followed by the chemistry and mechanism of action of antioxidant and antibacterial materials (dual function). Eventually, the outlook and challenges are underlined to provide where the dual-function biomaterials are and where they are going in the future. It is expected that the present article inspires the designing of dual-function biomaterials to more advanced levels by providing the fundamentals and comparative points of view and paving the clinical way for these materials.

Injectable Antioxidant and Oxygen-Releasing Lignin Composites to Promote Wound Healing

The application of engineered biomaterials for wound healing has been pursued since the beginning of tissue engineering. Here, we attempt to apply functionalized lignin to confer antioxidation to the extracellular microenvironments of wounds and to deliver oxygen from the dissociation of calcium peroxide for enhanced vascularization and healing responses without eliciting inflammatory responses. Elemental analysis showed 17 times higher quantity of calcium in the oxygen-releasing nanoparticles. Lignin composites including the oxygen-generating nanoparticles released around 700 ppm oxygen per day at least for 7 days. By modulating the concentration of the methacrylated gelatin, we were able to maintain the injectability of lignin composite precursors and the stiffness of lignin composites suitable for wound healing after photo-cross-linking. In situ formation of lignin composites with the oxygen-releasing nanoparticles enhanced the rate of tissue granulation, the formation of blood vessels, and the infiltration of α-smooth muscle actin⁺ fibroblasts into the wounds over 7 days. At 28 days after surgery, the lignin composite with oxygen-generating nanoparticles remodeled the collagen architecture, resembling the basket-weave pattern of unwounded collagen with minimal scar formation. Thus, our study shows the potential of functionalized lignin for wound-healing applications requiring balanced antioxidation and controlled release of oxygen for enhanced tissue granulation, vascularization, and maturation of collagen.

Engineering Cell Microenvironment Using Nanopattern-Derived Multicellular Spheroids and Photo-Crosslinked Gelatin/Hyaluronan Hydrogels

Cell cultures of dispersed cells within hydrogels depict the interaction of the cell-extracellular matrix (ECM) in 3D, while the coculture of different cells within spheroids combines both the effects of cell-cell and cell-ECM interactions. In this study, the cell co-spheroids of human bone mesenchymal stem cells/human umbilical vein endothelial cells (HBMSC/HUVECs) are prepared with the assistance of a nanopattern, named colloidal self-assembled patterns (cSAPs), which is superior to low-adhesion surfaces. A phenol-modified gelatin/hyaluronan (Gel-Ph/HA-Ph) hydrogel is used to encapsulate the multicellular spheroids and the constructs are photo-crosslinked using blue light. The results show that Gel-Ph/HA-Ph hydrogels with a 5%-to-0.3% ratio have the best properties. Cells in HBMSC/HUVEC co-spheroids are more favorable for osteogenic differentiation (Runx2, ALP, Col1a1 and OPN) and vascular network formation (CD31+ cells) compared to HBMSC spheroids. In a subcutaneous nude mouse model, the HBMSC/HUVEC co-spheroids showed better performance than HBMSC spheroids in angiogenesis and the development of blood vessels. Overall, this study paves a new way for using nanopatterns, cell coculturing and hydrogel technology for the generation and application of multicellular spheroids.

In situ forming ROS-scavenging hybrid hydrogel loaded with polydopamine-modified fullerene nanocomposites for promoting skin wound healing

BACKGROUND

Excessive oxidative stress at the wound sites always leads to a prolonged healing and even causes chronic inflammatory wounds. Therefore, antioxidative dressings with multiple features are desired to improve wound healing performance. Herein, we fabricated a ROS-scavenging hybrid hydrogel by incorporating mussel-inspired fullerene nanocomposites (C60@PDA) into gelatin methacryloyl (GelMA) hydrogel.

RESULTS

The developed C60@PDA/GelMA hydrogel showed a sustainable free radical scavenging ability, and eliminated ROS to protect cells against external oxidative stress damage. Besides, the hydrogel presented favorable cytocompatibility, hemocompatibility, and antibacterial ability in vitro. Furthermore, in a mouse full-thickness wound defect model, the in situ forming hybrid hydrogel accelerated wound closure by 38.5% and 42.9% on day 3 and day 7 over the control. Histological results demonstrated that hybrid hydrogels effectively enhanced wound healing on re-epithelialization, collagen deposition and angiogenesis.

CONCLUSION

Collectively, the C60@PDA/GelMA hydrogel could be a promising dressing for promoting cutaneous wound repair.

Enhanced neural differentiation by applying electrical stimulation utilizing conductive and antioxidant alginate-polypyrrole/poly-l-lysine hydrogels

The challenge of restoration from neurodegenerative disorder requires effective solutions. To enhance the healing efficiencies, scaffolds with antioxidant activities, electroconductivity, and versatile features to encourage neuronal differentiation are potentially useful. Herein, polypyrrole-alginate (Alg-PPy) copolymer was used to design antioxidant and electroconductive hydrogels through the chemical oxidation radical polymerization method. The hydrogels have antioxidant effects to combat oxidative stress in nerve damage thanks to the introduction of PPy. Additionally, poly-l-lysine (PLL) provided these hydrogels with a great differentiation ability of stem cells. The morphology, porosity, swelling ratio, antioxidant activity, rheological behavior, and conductive characteristics of these hydrogels were precisely adjusted by altering the amount of PPy. Characterization of hydrogels showed appropriate electrical conductivity and antioxidant activity for neural tissue applications. Cytocompatibility, live/dead assays, and Annexin V/PI staining by flow cytometry using P19 cells confirmed the excellent cytocompatibility and cell protective effect under ROS microenvironment of these hydrogels in both normal and oxidative conditions. The neural marker investigation in the induction of electrical impulses was assessed through RT-PCR and immunofluorescence assay, demonstrating the differentiation of P19 cells to neurons cultured in these scaffolds. In summary, the antioxidant and electroconductive Alg-PPy/PLL hydrogels demonstrated excellent potential as promising scaffolds for treating neurodegenerative disorders.

H2O2-PLA-(Alg)2Ca Hydrogel Enriched in Matrigel® Promotes Diabetic Wound Healing

Hydrogel-based dressings exhibit suitable features for successful wound healing, including flexibility, high water-vapor permeability and moisture retention, and exudate absorption capacity. Moreover, enriching the hydrogel matrix with additional therapeutic components has the potential to generate synergistic results. Thus, the present study centered on diabetic wound healing using a Matrigel-enriched alginate hydrogel embedded with polylactic acid (PLA) microspheres containing hydrogen peroxide (H2O2). The synthesis and physicochemical characterization of the samples, performed to evidence their compositional and microstructural features, swelling, and oxygen-entrapping capacity, were reported. For investigating the three-fold goal of the designed dressings (i.e., releasing oxygen at the wound site and maintaining a moist environment for faster healing, ensuring the absorption of a significant amount of exudate, and providing biocompatibility), in vivo biological tests on wounds of diabetic mice were approached. Evaluating multiple aspects during the healing process, the obtained composite material proved its efficiency for wound dressing applications by accelerating wound healing and promoting angiogenesis in diabetic skin injuries.

Synergy of antioxidant and M2 polarization in polyphenol-modified konjac glucomannan dressing for remodeling wound healing microenvironment

Effective skin wound healing and tissue regeneration remain a challenge. Excessive/chronic inflammation inhibits wound healing, leading to scar formation. Herein, we report a wound dressing composed of KGM-GA based on the natural substances konjac glucomannan (KGM) and gallic acid (GA) that accelerates wound healing without any additional drugs. An in vitro study showed that KGM-GA could not only stimulate macrophage polarization to the anti-inflammatory M2 phenotype but also decrease reactive oxygen species (ROS) levels, indicating excellent anti-inflammatory properties. Moreover, in vivo studies of skin wounds demonstrated that the KGM-GA dressing significantly improved wound healing by accelerating wound closure, collagen deposition, and angiogenesis. In addition, it was observed that KGM-GA regulated M2 polarization, reducing the production of intracellular ROS in the wound microenvironment, which was consistent with the in vitro experiments. Therefore, this study designed a multifunctional biomaterial with biological activity, providing a novel dressing for wound healing.

Modulating Inflammation-Mediated Diseases via Natural Phenolic Compounds Loaded in Nanocarrier Systems

The global increase and prevalence of inflammatory-mediated diseases have been a great menace to human welfare. Several works have demonstrated the anti-inflammatory potentials of natural polyphenolic compounds, including flavonoid derivatives (EGCG, rutin, apigenin, naringenin) and phenolic acids (GA, CA, etc.), among others (resveratrol, curcumin, etc.). In order to improve the stability and bioavailability of these natural polyphenolic compounds, their recent loading applications in both organic (liposomes, micelles, dendrimers, etc.) and inorganic (mesoporous silica, heavy metals, etc.) nanocarrier technologies are being employed. A great number of studies have highlighted that, apart from improving their stability and bioavailability, nanocarrier systems also enhance their target delivery, while reducing drug toxicity and adverse effects. This review article, therefore, covers the recent advances in the drug delivery of anti-inflammatory agents loaded with natural polyphenolics by the application of both organic and inorganic nanocarriers. Even though nanocarrier technology offers a variety of possible anti-inflammatory advantages to naturally occurring polyphenols, the complexes' inherent properties and mechanisms of action have not yet been fully investigated. Thus, expanding the quest on novel natural polyphenolic-loaded delivery systems, together with the optimization of complexes' activity toward inflammation, will be a new direction of future efforts.

An Injectable Integration of Autologous Bioactive Concentrated Growth Factor and Gelatin Methacrylate Hydrogel with Efficient Growth Factor Release and 3D Spatial Structure for Accelerated Wound Healing

Growth factors are essential for wound healing owing to their multiple reparative effects. Concentrated growth factor (CGF) is a third-generation platelet extract containing various endogenous growth factors. Here, a CGF extract solution is combined with gelatin methacrylate (GM) by physical blending to produce GM@CGF hydrogels for wound repair. The GM@CGF hydrogels show no immune rejection during autologous transplantation. Compared to CGF, GM@CGF hydrogels not only exhibit excellent plasticity and adhesivity but also prevent rapid release and degradation of growth factors. The GM@CGF hydrogels display good injectability, self-healing, swelling, and degradability along with outstanding cytocompatibility, angiogenic functions, chemotactic functions, and cell migration-promoting capabilities in vitro. The GM@CGF hydrogel can release various effective molecules to rapidly initiate wound repair, stimulate the expressions of type I collagen, transform growth factor β1, epidermal growth factor, and vascular endothelial growth factor, promote the production of granulation tissues, vascular regeneration and reconstruction, collagen deposition, and epidermal cell migration, as well as prevent excessive scar formation. In conclusion, the injectable GM@CGF hydrogel can release various growth factors and provide a 3D spatial structure to accelerate wound repair, thereby providing a foundation for the clinical application and translation of CGF.

Multiscale design of stiffening and ROS scavenging hydrogels for the augmentation of mandibular bone regeneration

Although biomimetic hydrogels play an essential role in guiding bone remodeling, reconstructing large bone defects is still a significant challenge since bioinspired gels often lack osteoconductive capacity, robust mechanical properties and suitable antioxidant ability for bone regeneration. To address these challenges, we first engineered molecular design of hydrogels (gelatin/polyethylene glycol diacrylate/2-(dimethylamino)ethyl methacrylate, GPEGD), where their mechanical properties were significantly enhanced via introducing trace amounts of additives (0.5 wt%). The novel hybrid hydrogels show high compressive strength (>700 kPa), stiff modulus (>170 kPa) and strong ROS-scavenging ability. Furthermore, to endow the GPEGD hydrogels excellent osteoinductions, novel biocompatible, antioxidant and BMP-2 loaded polydopamine/heparin nanoparticles (BPDAH) were developed for functionalization of the GPEGD gels (BPDAH-GPEGD). In vitro results indicate that the antioxidant BPDAH-GPEGD is able to deplete elevated ROS levels to protect cells viability against ROS damage. More importantly, the BPDAH-GPEGD hydrogels have good biocompatibility and promote the osteo differentiation of preosteoblasts and bone regenerations. At 4 and 8 weeks after implantation of the hydrogels in a mandibular bone defect, Micro-computed tomography and histology results show greater bone volume and enhancements in the quality and rate of bone regeneration in the BPDAH-GPEGD hydrogels. Thus, the multiscale design of stiffening and ROS scavenging hydrogels could serve as a promising material for bone regeneration applications.

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Trace additives of DMAEMA markedly enhanced the mechanical performances of the gelatin-based hydrogels through molecular induced multiple crosslinking structures.

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Molecular design strategy combined with bioactive nanocomposites have a synergistically effects on promoting ROS scavenging ability and osteoactivity of the biomimetic hydrogels.

Anti-oxidant anti-inflammatory and antibacterial tannin-crosslinked citrate-based mussel-inspired bioadhesives facilitate scarless wound healing

The revolutionary role of tissue adhesives in wound closure, tissue sealing, and bleeding control necessitates the development of multifunctional materials capable of effective and scarless healing. In contrast to the use of traditionally utilized toxic oxidative crosslinking initiators (exemplified by sodium periodate and silver nitrate), herein, the natural polyphenolic compound tannic acid (TA) was used to achieve near instantaneous (<25s), hydrogen bond mediated gelation of citrate-based mussel-inspired bioadhesives combining anti-oxidant, anti-inflammatory, and antimicrobial activities (3A-TCMBAs). The resulting materials were self-healing and possessed low swelling ratios (<60%) as well as considerable mechanical strength (up to ∼1.0 MPa), elasticity (elongation ∼2700%), and adhesion (up to 40 kPa). The 3A-TCMBAs showed strong in vitro and in vivo anti-oxidant ability, favorable cytocompatibility and cell migration, as well as photothermal antimicrobial activity against both Staphylococcus aureus and Escherichia coli (>90% bacterial death upon near-infrared (NIR) irradiation). In vivo evaluation in both an infected full-thickness skin wound model and a rat skin incision model demonstrated that 3A-TCMBAs + NIR treatment could promote wound closure and collagen deposition and improve the collagen I/III ratio on wound sites while simultaneously inhibiting the expression of pro-inflammatory cytokines. Further, phased angiogenesis was observed via promotion in the early wound closure phases followed by inhibition and triggering of degradation & remodeling of the extracellular matrix (ECM) in the late stage (supported by phased CD31 (platelet endothelial cell adhesion molecule-1) PDGF (platelet-derived growth factor) and VEGF (vascular endothelial growth factor) expression as well as elevated matrix metalloprotein-9 (MMP-9) expression on day 21), resulting in scarless wound healing. The significant convergence of material and bioactive properties elucidated above warrant further exploration of 3A-TCMBAs as a significant, new class of bioadhesive.

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Citrate-based mussel-inspired bioadhesive prepolymers were crosslinked with tannic acid via hydrogen bonding (3A-TCMBAs).

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3A-TCMBAs showed good tissue adhesiveness, self-healing and elastic properties.

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3A-TCMBAs exhibited photothermal antibacterial, antioxidant and anti-inflammatory efficiency.

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3A-TCMBAs could promote scarless wound healing by enabling phased angiogenesis.

Polyphenol-driven facile assembly of a nanosized acid fibroblast growth factor-containing coacervate accelerates the healing of diabetic wounds

Diabetic wounds are challenging to heal due to complex pathogenic abnormalities. Routine treatment with acid fibroblast growth factor (aFGF) is widely used for diabetic wounds but hardly offers a satisfying outcome due to its instability. Despite the emergence of various nanoparticle-based protein delivery approaches, it remains challenging to engineer a versatile delivery system capable of enhancing protein stability without the need for complex preparation. Herein, a polyphenol-driven facile assembly of nanosized coacervates (AE-NPs) composed of aFGF and Epigallocatechin-3-gallate (EGCG) was constructed and applied in the healing of diabetic wounds. First, the binding patterns of EGCG and aFGF were predicted by molecular docking analysis. Then, the characterizations demonstrated that AE-NPs displayed higher stability in hostile conditions than free aFGF by enhancing the binding activity of aFGF to cell surface receptors. Meanwhile, the AE-NPs also had a powerful ability to scavenge reactive oxygen species (ROS) and promote angiogenesis, which significantly accelerated full-thickness excisional wound healing in diabetic mice. Besides, the AE-NPs suppressed the early scar formation by improving collagen remodeling and the mechanism was associated with the TGF-β/Smad signaling pathway. Conclusively, AE-NPs might be a potential and facile strategy for stabilizing protein drugs and achieving the scar-free healing of diabetic wounds. STATEMENT OF SIGNIFICANCE: Diabetic chronic wound is among the serious complications of diabetes that eventually cause the amputation of limbs. Herein, a polyphenol-driven facile assembly of nanosized coacervates (AE-NPs) composed of aFGF and EGCG was constructed. The EGCG not only acted as a carrier but also possessed a therapeutic effect of ROS scavenging. The AE-NPs enhanced the binding activity of aFGF to cell surface receptors on the cell surface, which improved the stability of aFGF in hostile conditions. Moreover, AE-NPs significantly accelerated wound healing and improved collagen remodeling by regulating the TGF-β/Smad signaling pathway. Our results bring new insights into the field of polyphenol-containing nanoparticles, showing their potential as drug delivery systems of macromolecules to treat diabetic wounds.

Multifunctional hydrogel with reactive oxygen species scavenging and photothermal antibacterial activity accelerates infected diabetic wound healing

Management of diabetic wound has long been a clinical challenge due to pathological microenvironment of excessive inflammation, persistent hyperglycemia, and biofilm infection caused by overdue reactive oxygen species (ROS) production and defective blood vessels. Herein, a multifunctional hydrogel with ROS scavenging and photothermal antibacterial activity based on oxidized dextran (Odex), gallic acid-grafted gelatin (GAG) and Ferric ion, named OGF, was developed for treatment of infected wound in a diabetic mouse. This hydrogel was double-crosslinked by the dynamically Schiff-base bonds formed between aldehyde groups in Odex and amino groups in GAG and the metal coordination bonds formed between Ferric ion and polyphenol groups or carboxyl groups in GAG, which endowed the resulted OGF hydrogel with well injectable, self-healing and adhesive properties. Due to the high-efficiency photothermal effect of Ferric ion/polyphenol chelate, this hydrogel killed Staphylococcus aureus and Escherichia coli rapidly and completely within 3.5 min under near-infrared light radiation. Furthermore, this composed hydrogel presented good antioxidation, hemostasis and biocompatibility. It also remarkably accelerated the complete re‑epithelialization of Staphylococcus aureus‑infected wound in diabetic mice within 18 days by eliminating infection, mitigating oxidative stress and inflammation, and facilitating angiogenesis. Therefore, the proposed multifunctional hydrogel exerts a great potential for translation in the clinical management of diabetic wounds. STATEMENT OF SIGNIFICANCE: High reactive oxygen species (ROS) levels and vascular defects in diabetic wounds can lead to excessive inflammation, persistent hyperglycemia, biofilm infection and other pathological microenvironments, which can further develop to the chronic wounds. In this study, we designed a multifunctional hydrogel with ROS-scavenging ability and photothermal antibacterial activity for the treatment of infected diabetic wound. As expected, this multifunctional hydrogel dressing highly accelerated the complete re‑epithelialization of Staphylococcus aureus‑infected wound in diabetic mouse by eliminating infection, mitigating oxidative stress and inflammation, as well as facilitating angiogenesis. This work provides a promising therapeutic strategy for infected diabetic wound by inhibition of oxidative stress and biofilm infection.

Reoxygenation Modulates the Adverse Effects of Hypoxia on Wound Repair

Hypoxia is a major stressor and a prominent feature of pathological conditions, such as bacterial infections, inflammation, wounds, and cardiovascular defects. In this study, we investigated whether reoxygenation has a protective effect against hypoxia-induced acute injury and burn using the C57BL/6 mouse model. C57BL/6 mice were exposed to hypoxia and treated with both acute and burn injuries and were in hypoxia until wound healing. Next, C57BL/6 mice were exposed to hypoxia for three days and then transferred to normoxic conditions for reoxygenation until wound healing. Finally, skin wound tissue was collected to analyze healing-related markers, such as inflammation, vascularization, and collagen. Hypoxia significantly increased inflammatory cell infiltration and decreased vascular and collagen production, and reoxygenation notably attenuated hypoxia-induced infiltration of inflammatory cells, upregulation of pro-inflammatory cytokine levels (IL-6 and TNF-α) in the wound, and remission of inflammation in the wound. Immunofluorescence analysis showed that reoxygenation increased the expression of the angiogenic factor α-SMA and decreased ROS expression in burn tissues compared to hypoxia-treated animals. Moreover, further analysis by qPCR showed that reoxygenation could alleviate the expression of hypoxic-induced inflammatory markers (IL-6 and TNF), increase angiogenesis (SMA) and collagen synthesis (Col I), and thus promote wound healing. It is suggested that oxygen can be further evaluated in combination with oxygen-releasing materials as a supplementary therapy for patients with chronic hypoxic wounds.

Recent Advancement of Functional Hydrogels toward Diabetic Wound Management

Wound healing is a dynamic, orchestrated process comprising partially overlapping phases of hemostasis, inflammation, proliferation, and remodeling. This programmed process, dysregulated in diabetic individuals, results in chronic diabetic wounds. The normal process of healing halts at the inflammatory stage, and this prolonged inflammatory phase is characteristic of diabetic wounds. There are a few U.S. Food & Drug Administration approved skin substitutes; dermal matrixes are commercially available to manage diabetic wounds. However, expensiveness and nonresponsiveness in a few instances are the major limitations of such modalities. To address the issues, several treatment strategies have been exploited to treat chronic wounds; among them hydrogel-based systems showed promise due to favorable properties such as excellent absorption capabilities, porous structure, tunable mechanical strength, and biocompatibility. In the past two decades, hydrogels have become one of the most acceptable systems in the field of wound dressing material, offering single functionality to multifunctionality. This review focuses on the advancement of functional hydrogels explored for diabetic wound management. The process of diabetic wound healing is discussed in the light of the normal healing process, and the role of macrophages in the process is explained. This review also discusses the different approaches to treat diabetic wounds using functional hydrogels, along with their future opportunities.

Novel ROS-scavenging hydrogel with enhanced anti-inflammation and angiogenic properties for promoting diabetic wound healing

Accelerating angiogenesis of diabetic wounds is crucial to promoting wound healing. Currently, vascular endothelial growth factor (VEGF), an angiogenesis-related bioactive molecule, is widely used in clinic to enhance wound angiogenesis, but it faces problems of inactivation and low utilization due to harsh microenvironment. Here, we developed a novel reactive oxygen species (ROS)-scavenging hydrogel aimed to polarize macrophages toward an anti-inflammatory phenotype, inducing efficient angiogenesis in diabetic wounds. This composite hydrogel with good biosafety and mechanical properties showed sustainable release of bioactive VEGF. Importantly, it could significantly reduce ROS level and rapidly improve wound microenvironment, which ensured the activity of VEGF in vitro and in vivo and successful healing eventually. At the same time, the composite hydrogel exhibited excellent antibacterial properties. In vivo results confirmed good anti-inflammatory, stimulated vascularization and accelerated wound healing attributed to the novel ROS-scavenging hydrogel, which might serve as a promising wound dressing in diabetic wound healing.

Anti-inflammatory hydrogel dressings and skin wound healing

Hydrogels are promising and widely utilized in the biomedical field. In recent years, the anti-inflammatory function of hydrogel dressings has been significantly improved, addressing many clinical challenges presented in ongoing endeavours to promote wound healing. Wound healing is a cascaded and highly complex process, especially in chronic wounds, such as diabetic and severe burn wounds, in which adverse endogenous or exogenous factors can interfere with inflammatory regulation, leading to the disruption of the healing process. Although insufficient wound inflammation is uncommon, excessive inflammatory infiltration is an almost universal feature of chronic wounds, which impedes a histological repair of the wound in a predictable biological step and chronological order. Therefore, resolving excessive inflammation in wound healing is essential. In the past 5 years, extensive research has been conducted on hydrogel dressings to address excessive inflammation in wound healing, specifically by efficiently scavenging excessive free radicals, sequestering chemokines and promoting M₁ -to-M₂ polarization of macrophages, thereby regulating inflammation and promoting wound healing. In this study, we introduced novel anti-inflammatory hydrogel dressings and demonstrated innovative methods for their preparation and application to achieve enhanced healing. In addition, we summarize the most important properties required for wound healing and discuss our analysis of potential challenges yet to be addressed.

Injectable and reactive oxygen species-scavenging gelatin hydrogel promotes neural repair in experimental traumatic brain injury

Oxidative stress caused by the overexpression of reactive oxygen species (ROS) plays an important role in the pathogenesis of traumatic brain injury (TBI). Accumulation of ROS can lead to cell death, neurodegeneration, and neurological deficit. Therefore, the design and application of functional materials with ROS scavenging ability is of great significance for neural repair. Herein, an injectable and antioxidant hydrogel was developed for TBI treatment based on the Schiff base reaction of gallic acid-conjugated gelatin (GGA) and oxidized dextran (Odex). The resulting GGA/Odex hydrogel could effectively scavenge DPPH and ABTS radicals, as well as protect cells from the oxidative damage in vitro. Moreover, GGA/Odex hydrogel possessed well biocompatible features. In a moderate TBI mouse model, in situ implantation of GGA6Odex hydrogel efficiently facilitated neurogenesis and promoted the motor, learning and memory abilities. Also, this composite hydrogel suppressed oxidative stress and inflammation via the activation of Nrf2/HO-1 pathway and the regulating of inflammatory factors secretion and macrophage/microglia polarization. Therefore, this injectable and ROS-scavenging GGA6Odex hydrogel is a promising biomaterial for tissue regenerative medicine, including TBI and other tissue repair relevant to raised ROS circumstance.

Multifunctional dual cross-linked poly (vinyl alcohol)/methacrylate hyaluronic acid/chitooligosaccharide-sinapic acid wound dressing hydrogel

Wound dressing hydrogel with multifunctional properties, including antioxidant and antimicrobial properties and appropriate mechanical, biological, and physical properties is of great interest in wound healing application and it is still a challenge. In the present study, chitooligosaccharides (COS)/ sinapic acid (SA) conjugate (COS-SA) was synthesized using H₂O₂-induced grafting polymerization, and photo cross-linkable hyaluronic acid was synthesized using methacrilation (HAMA). The synthesis of COS-SA and HAMA was confirmed by Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, ultraviolet spectroscopy, and polyphenol assay. Subsequently, we developed duel cross-linked polyvinyl alcohol (PVA)/HAMA composite hydrogel encapsulated with COS-SA as an antioxidant and antimicrobial dressing for full-thickness wound healing application. The chemical, physical, mechanical, antioxidant, antimicrobial, in vitro biocompatibility, and in vivo wound healing properties of hydrogels were subsequently investigated. The results showed that the fabricated composite hydrogel had a uniform porous architecture, excellent fluid absorbability, and appropriate mechanical stability. The introduction of COSs-SA conjugate remarkably enhanced the in vitro biocompatibility, antioxidant, and antimicrobial properties of the hydrogel, leading to the significant promotion of in vivo full-thickness wound closure, re-epithelization, granulation tissue formation, and collagen deposition indicating that COSs-SA incorporated PVA/HAMA hydrogel wound dressing has significant potential for chronic wound healing application.

Progress in Stimuli-Responsive Biomaterials for Treating Cardiovascular and Cerebrovascular Diseases

Cardiovascular and cerebrovascular diseases (CCVDs) describe abnormal vascular system conditions affecting the brain and heart. Among these, ischemic heart disease and ischemic stroke are the leading causes of death worldwide, resulting in 16% and 11% of deaths globally. Although several therapeutic approaches are presented over the years, the continuously increasing mortality rates suggest the need for more advanced strategies for their treatment. One of these strategies lies in the use of stimuli-responsive biomaterials. These "smart" biomaterials can specifically target the diseased tissue, and after "reading" the altered environmental cues, they can respond by altering their physicochemical properties and/or their morphology. In this review, the progress in the field of stimuli-responsive biomaterials for CCVDs in the last five years, aiming at highlighting their potential as early-stage therapeutics in the preclinical scenery, is described.

Adhesive, injectable, and ROS-responsive hybrid polyvinyl alcohol (PVA) hydrogel co-delivers metformin and fibroblast growth factor 21 (FGF21) for enhanced diabetic wound repair

As conventional treatments for diabetic wounds often fail to achieve rapid satisfactory healing, the development of effective strategies to accelerate diabetic wound repair is highly demanded. Herein, fibroblast growth factor 21 (FGF21) and metformin co-loaded multifunctional polyvinyl alcohol (PVA) hydrogel were fabricated for improved diabetic wound healing. The in vitro results proved that the hydrogel was adhesive and injectable, and that it could particularly scavenge reactive oxygen species (ROSs), while the in vivo data demonstrated that the hydrogel could promote angiogenesis by recruiting endothelial progenitor cells (EPCs) through upregulation of Ang-1. Both ROSs’ removal and EPCs’ recruitment finally resulted in enhanced diabetic wound healing. This work opens a strategy approach to diabetic wound management by combining biological macromolecules and small chemical molecules together using one promising environmental modulating drug delivery system.

The potential application of natural products in cutaneous wound healing: A review of preclinical evidence

Under normal circumstances, wound healing can be summarized as three processes. These include inflammation, proliferation, and remodeling. The vast majority of wounds heal rapidly; however, a large percentage of nonhealing wounds have still not been studied significantly. The factors affecting wound nonhealing are complex and diverse, and identifying an effective solution from nature becomes a key goal of research. This study aimed to highlight and review the mechanisms and targets of natural products (NPs) for treating nonhealing wounds. The results of relevant studies have shown that the effects of NPs are associated with PI3K-AKT, P38MAPK, fibroblast growth factor, MAPK, and ERK signaling pathways and involve tumor growth factor (TNF), vascular endothelial growth factor, TNF-α, interleukin-1β, and expression of other cytokines and proteins. The 25 NPs that contribute to wound healing were systematically summarized by an inductive collation of the six major classes of compounds, including saponins, polyphenols, flavonoids, anthraquinones, polysaccharides, and others, which will further direct the attention to the active components of NPs and provide research ideas for further development of new products for wound healing.

Intrinsic ROS Drive Hair Follicle Cycle Progression by Modulating DNA Damage and Repair and Subsequently Hair Follicle Apoptosis and Macrophage Polarization

Hair follicles (HFs) maintain homeostasis through the hair cycles; therefore, disrupting the hair cycle may lead to hair loss. Our previous study showed that apoptosis-inducing factor (AIF) nuclear translocation and poly [ADP-ribose] polymerase 1 (PARP1) upregulation induced apoptosis in mouse hair follicles during the hair cycle transition from anagen to catagen. However, the mechanism underlying this phenomenon remains unclear. In this study, we found that intrinsic ROS levels increased during the hair follicle cycle transition from anagen to catagen, followed by abrupt DNA breaks and activation of homologous recombinant and nonhomologous end joining DNA repair, along with the enhancement of apoptosis. Mice in different stages of the hair cycle were sacrificed, and the dorsal skins were collected. The results of western blot and histological staining indicated that AIF-PARP1 plays a key role in HF apoptosis, but their role in the regulation of the HF cycle is not clear. Mice were treated with inhibitors from anagen to catagen: treatment with BMN 673, a PARP1 inhibitor, increased DNA breaks and activated the cytochrome c/caspase-3-mediated apoptotic pathway, accelerating HF regression. Ac-DEVD-CHO (Ac), a caspase-3 inhibitor, attenuated HF degeneration by upregulating PARP1 expression, suggesting a seesaw relationship between cytochrome c-caspase-3- and AIF-PARP1-mediated apoptosis, wherein PARP1 may be the fulcrum. In addition, macrophages were involved in regulating the hair cycle, and the rate of M1 macrophages around HFs increased during catagen, while more M2 macrophages were found during anagen and telogen. Our results indicate that intrinsic ROS drive HF cycle progression through DNA damage and repair, followed by apoptosis. Intrinsic ROS drive hair follicle cycle progression by modulating DNA damage and repair, and consecutively, hair follicle apoptosis and macrophage polarization work together to promote the hair follicle cycle.

Current Advances in the Development of Hydrogel-Based Wound Dressings for Diabetic Foot Ulcer Treatment

Diabetic foot ulcers (DFUs) are one of the most prevalent complications associated with diabetes mellitus. DFUs are chronic injuries that often lead to non-traumatic lower extremity amputations, due to persistent infection and other ulcer-related side effects. Moreover, these complications represent a significant economic burden for the healthcare system, as expensive medical interventions are required. In addition to this, the clinical treatments that are currently available have only proven moderately effective, evidencing a great need to develop novel strategies for the improved treatment of DFUs. Hydrogels are three-dimensional systems that can be fabricated from natural and/or synthetic polymers. Due to their unique versatility, tunability, and hydrophilic properties, these materials have been extensively studied for different types of biomedical applications, including drug delivery and tissue engineering applications. Therefore, this review paper addresses the most recent advances in hydrogel wound dressings for effective DFU treatment, providing an overview of current perspectives and challenges in this research field.

Functionalized injectable hyaluronic acid hydrogel with antioxidative and photothermal antibacterial activity for infected wound healing

Infected wound healing has always been a challenge in clinic. Effective and economic wound dressings with combined antibacterial activity and pro-healing function are highly desirable, especially in the context of infected wounds. An obvious advantage of antibacterial wound dressing is to avoid the overuse of antibiotics and the occurrence of drug resistance. Herein, an injectable hyaluronic acid hydrogel with antioxidative and photothermal antibacterial activity as a functional dressing was prepared, characterized and evaluated in an experimental infected wound model. This hydrogel was developed by loading graphene oxide (GO) in a natural polymer network consisting of hyaluronic acid grafted with tyramine (HT) and gelatin grafted with gallic acid (GGA). The HT/GGA/GO hydrogels have a porous cross-linked network structure and demonstrate a good stability, biocompatibility, antioxidant, hemostatic and photothermal antibacterial activity against Escherichia coli and Staphylococcus aureus. In addition, in vivo studies have shown that HT₁/GGA₂/GO_0.1 hydrogel dressing combined with photothermal therapy can effectively prevent early infection and accelerate wound healing. These results indicated this functionalized injectable hydrogel HT₁/GGA₂/GO_0.1 has a great potential in wound dressing application.

Recent Studies on Hydrogels Based on H2O2-Responsive Moieties: Mechanism, Preparation and Application

H₂O₂ is essential for cellular processes and plays a vital role in the regulation of cell signaling pathways, which can be viewed as a warning signal for many kinds of disease including cancer, cardiovascular disease, reproductive abnormalities, diabetes, and renal failure. A H₂O₂-responsive hydrogel (H₂O₂-Gel) is a promising candidate for biomedical applications because of its good biocompatibility, similarity to soft biological tissues, ease of preparation, and its ability to respond to H₂O₂. In this study, the H₂O₂-responsive moieties used to fabricate H₂O₂-Gels were reviewed, including thioethers, disulfide bonds, selenides, diselenium bonds, diketones, boronic, and others. Next, the preparation method of H₂O₂-Gel was divided into two major categories according to their reaction mechanisms: either self-crosslinking or mechanisms entailing the addition of difunctional crosslinkers. Last, the applications of H₂O₂-Gels were emphasized, which have been viewed as desirable candidates in the fields of drug delivery, the detection of H₂O₂, glucose-responsive systems, ROS scavengers, tissue engineering, and cell-encapsulation.

In situ forming and biocompatible hyaluronic acid hydrogel with reactive oxygen species-scavenging activity to improve traumatic brain injury repair by suppressing oxidative stress and neuroinflammation

The efficacy of neural repair and regeneration strategies for traumatic brain injury (TBI) treatment is greatly hampered by the harsh brain lesion microenvironment including oxidative stress and hyper-inflammatory response. Functionalized hydrogel with the capability of oxidative stress suppression and neuroinflammation inhibition will greatly contribute to the repairment of TBI. Herein, antioxidant gallic acid-grafted hyaluronic acid (HGA) was combined with hyaluronic acid-tyramine (HT) polymer to develop an injectable hydrogel by dual-enzymatically crosslinking method. The resulting HT/HGA hydrogel is biocompatible and possesses effective scavenging activity against DPPH and hydroxyl radicals. Meanwhile, this hydrogel improved cell viability and reduced intracellular reactive oxygen species (ROS) production under H₂O₂ insult. The in vivo study showed that in situ injection of HT/HGA hydrogel significantly reduced malondialdehyde (MDA) production and increased glutathione (GSH) expression in lesion area after treatment for 3 or 21 days, which might be associated with the activation of Nrf2/HO-1 pathway. Furthermore, this hydrogel promoted the microglia polarization to M2 (Arg1) phenotype, it also decreased the level of proinflammatory factors including TNF-α and IL-6 and increased anti-inflammatory factor expression of IL-4. Finally, blood-brain barrier (BBB) was protected, neurogenesis in hippocampus was promoted, and the motor, learning and memory ability was enhanced. Therefore, this injectable, biocompatible, and antioxidant hydrogel exhibits a huge potential for treating TBI and allows us to recognize the great value of this novel biomaterial for remodeling brain structure and function.

Copper-Hydrazide Coordinated Multifunctional Hyaluronan Hydrogels for Infected Wound Healing

Bacterial infection and delayed healing are two major obstacles in cutaneous wound management, and developing multifunctional hydrogels with antibacterial and prohealing capabilities presents a promising strategy to dress wounds. However, the simple and facile fabrication of such hydrogel dressings remains challenging. Herein, we report the first observation on hydrazide-metal coordination crosslinking that is utilized to successfully construct a series of hyaluronan (HA)-metal hydrogels by mixing hydrazided HA and metal ion solutions. Considering the antibacterial, prohealing, and proangiogenic properties of HA and Cu(II), as a proof of principle, a HA-Cu hydrogel was systematically investigated as a wound dressing. Surprisingly, the hydrazide-Cu(II) coordination was dynamic in nature and imparted the HA-Cu hydrogel with physicochemical multifunctions, including spontaneous self-healing, shear-thinning injectability, reversible pH/redox/ion pair triple responsiveness, etc. Moreover, the HA-Cu hydrogel exhibited a robust broad-spectrum antibacterial activity and could significantly accelerate infectious wound healing. Impressively, glutathione-triggered hydroxyl radical generation further potentiated wound healing, providing a paradigm for on-demand antibacterial activity enhancement. Hence, the HA-Cu hydrogel is a clinically applicable "smart" dressing for multi-scenario wound healing. We envision that the simple and versatile coordination approach opens up a new avenue to develop multifunctional hydrogels and shows great potential in frontier fields, such as biomedicine, wearable devices, and soft robots.

In situ forming hydrogel recombination with tissue adhesion and antibacterial property for tissue adhesive

In situ forming hydrogels with strong adhesive strength and antibacterial activity are of great interest to serve as tissue adhesive in fields like wound dressing and mass hemorrhage. In this study, hybrid hydrogel (GOHA) based on gelatin and oxidized hyaluronic acid was developed and endowed with excellent mechanical strength and tissue adhesion. According to our results, GOHA hydrogel exhibits a fast gelation time of around 60 s, robust compression strength of 223.43 ± 24.28 kPa, and strong adhesion of 14.33 ± 0.78 kPa to porcine skin, which is much higher than that of commercial fibrin glue (around 1.00 kPa). Meanwhile, through the loading of levofloxacin, obvious antibacterial activity can be obtained for wider applications. Notably, it would not compromise the hemocompatibility and cytocompatibility in vitro. In summary, this kind of hybrid hydrogel shows great potential as tissue adhesive in biomedical fields.

Crosslinkers for polysaccharides and proteins: Synthesis conditions, mechanisms, and crosslinking efficiency, a review

Polysaccharides and proteins are important macromolecules for developing hydrogels devoted to biomedical applications. Chemical hydrogels offer chemical, mechanical, and dimensional stability than physical hydrogels due to the chemical bonds among the chains mediated by crosslinkers. There are many crosslinkers to synthesize polysaccharides and proteins based on hydrogels. In this review, we revisited the crosslinking reaction mechanisms between synthetic or natural crosslinkers and polysaccharides or proteins. The selected synthetic crosslinkers were glutaraldehyde, carbodiimide, boric acid, sodium trimetaphosphate, N,N'-methylene bisacrylamide, and polycarboxylic acid, whereas the selected natural crosslinkers included transglutaminase, tyrosinase, horseradish peroxidase, laccase, sortase A, genipin, vanillin, tannic acid, and phytic acid. No less important are the reactions involving click chemistry and the macromolecular crosslinkers for polysaccharides and proteins. Literature examples of polysaccharides or proteins crosslinked by the different strategies were presented along with the corresponding highlights. The general mechanism involved in chemical crosslinking mediated by gamma and UV radiation was discussed, with particular attention to materials commonly used in digital light processing. The evaluation of crosslinking efficiency by gravimetric measurements, rheology, and spectroscopic techniques was presented. Finally, we presented the challenges and opportunities to create safe chemical hydrogels for biomedical applications.

Emerging Fabrication Strategies of Hydrogels and Its Applications

Recently, hydrogels have been investigated for the controlled release of bioactive molecules, such as for living cell encapsulation and matrices. Due to their remote controllability and quick response, hydrogels are widely used for various applications, including drug delivery. The rate and extent to which the drugs reach their targets are highly dependent on the carriers used in drug delivery systems; therefore the demand for biodegradable and intelligent carriers is progressively increasing. The biodegradable nature of hydrogel has created much interest for its use in drug delivery systems. The first part of this review focuses on emerging fabrication strategies of hydrogel, including physical and chemical cross-linking, as well as radiation cross-linking. The second part describes the applications of hydrogels in various fields, including drug delivery systems. In the end, an overview of the application of hydrogels prepared from several natural polymers in drug delivery is presented.

Facile Solvent-Free Preparation of Antioxidant Idebenone-Loaded Nanoparticles for Efficient Wound Healing

The excessive production of reactive oxygen species (ROS) causes harmful effects, including biomolecular damage and inflammation. ROS due to ultraviolet rays, blue light, and fine dust harm the skin, causing urban-related aging. Therefore, a strong antioxidant that relieves oxidative stress in the skin and removes ROS is required. Idebenone (IB) is a powerful antioxidant but is poorly soluble and thus has low solubility in water, resulting in low bioavailability. In this study, IB-loaded nanoparticles (IB@NPs) were synthesized by loading IB without an organic solvent into nanoparticles that can provide high loading efficiency and stability for solubilization. Indeed, the synthesized IB@NPs exhibited long-term stability through dynamic light scattering, methylene blue staining, and redispersion assays, and IB@NPs prepared with a 5 wt% IB loading content were found to be optimal. The antioxidant activity of IB@NPs evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was significantly higher than that of unloaded IB. In addition, IB@NPs showed excellent biocompatibility, inhibited oxidative damage to mouse NIH-3T3 fibroblasts, and reduced intracellular ROS generation according to an in vitro DPPH antioxidant assay. Most notably, IB@NPs significantly promoted wound healing in vitro, as demonstrated by scratch assays. Therefore, as carriers with excellent stability, IB@NPs have potential cosmetic and pharmaceutical applications.

Bioinspired Multifunctional Black Phosphorus Hydrogel with Antibacterial and Antioxidant Properties: A Stepwise Countermeasure for Diabetic Skin Wound Healing

Cutaneous wound healing, especially diabetic wound healing, is a common clinical challenge. Reactive oxygen species (ROS) and bacterial infection are two major detrimental states that induce oxidative stress and inflammatory responses and impede angiogenesis and wound healing. A derivative of the metabolite itaconate, 4-octyl itaconate (4OI) has attracted increasing research interest in recent years due to its antioxidant and anti-inflammatory properties. In this study, 4OI-modified black phosphorus (BP) nanosheets are incorporated into a photosensitive, multifunctional gelatin methacrylamide hydrogel to produce a new photothermal therapy (PTT) and photodynamic therapy (PDT) system with antibacterial and antioxidant properties for diabetic wound regeneration. Under laser irradiation, the 4OI-BP-entrapped hydrogel enables rapid gelation, forming a membrane on wounds, and offers high PTT and PDT efficacy to eliminate bacterial infection. Without laser irradiation, BP acts as a carrier and controls the release of 4OI, with which it synergistically enhances antioxidant activity, thus alleviating excessive ROS damage to endothelial cells, promoting neovascularization, and facilitating faster diabetic wound closure. These findings indicate that 4OI-BP-entrapped multifunctional hydrogel provides a stepwise countermeasure with antibacterial and antioxidant properties for enhanced diabetic wound healing and may lead to novel therapeutic interventions for diabetic ulcers.

Human Umbilical Cord Mesenchymal Stem Cell-Derived Exosomes Accelerate Diabetic Wound Healing via Ameliorating Oxidative Stress and Promoting Angiogenesis

Diabetic wounds remain a great challenge for clinicians due to the multiple bacterial infections and oxidative damage. Exosomes, as an appealing nanodrug delivery system, have been widely applied in the treatment of diabetic wounds. Endovascular cells are important component cells of the vascular wall. Herein, we investigated the effects of HUCMSCs and HUC-Exos (exosomes secreted by HUCMSCs) on diabetic wound healing. In this study, HUVECs were coincubated with HUCMSCs, and HUC-Exos were utilized for in vitro and in vivo experiments to verify their roles in the regulation of diabetic wound healing. Our results demonstrated that HUCMSCs have the ability to regulate oxidative stress injuries of endothelial cells through exosomes and accelerate diabetic cutaneous wound healing in vitro. The present study suggests that HUC-Exos accelerate diabetic cutaneous wound healing, providing a promising therapeutic strategy for chronic diabetic wound repair.

In Vitro Cell Culture of Rhus coriaria L.: A Standardized Phytocomplex Rich of Gallic Acid Derivatives with Antioxidant and Skin Repair Activity

This study focused on the biological evaluation and chemical characterization of a new ingredient obtained by in vitro cell culture of Rhus coriaria L. An in vitro plant cell culture method permits to cultivate plant in a short period of time and to obtain extract with a high safety profile for the consumer, free from heavy metals, pesticides, aflatoxins, bacterial or fungal contamination. Through the selection of specific cell culture media, it was possible to obtain a Rhus coriaria cell line with a high content of gallic acid derivatives. The Rhus coriaria L. phytocomplex (RC-P), containing 7.6% w/w of acid gallic derivatives, was obtained by drying of plant cell biomass after 14 days of growth in the final selected culture medium. UPLC-ESI-MS and UPLC-DAD analysis allowed to identify numerous gallic acid derivatives, such as galloyl hexose, trigalloyl hexose and high molecular weight galloyl derivatives, and to quantify their overall content. The antioxidant activity of the RC-P was tested by DPPH assay and the wound healing activity was evaluated using a scratch wound healing test on human keratinocytes and fibroblasts. This work showed that RC-P could be a new effective cosmetic ingredient with antioxidant and skin repair activity.

Reactive Oxygen Species-Based Biomaterials for Regenerative Medicine and Tissue Engineering Applications

Reactive oxygen species (ROS), acting as essential mediators in biological system, play important roles in the physiologic and pathologic processes, including cellular signal transductions and cell homeostasis interference. Aberrant expression of ROS in tissue microenvironment can be caused by the internal/external stimuli and tissue injury, which may leads to an elevated level of oxidative stress, inflammatory response, and cellular damage as well as disruption in the tissue repair process. To prevent the formation of excess ROS around the injury site, advanced biomaterials can be remodeled or instructed to release their payloads in an injury microenvironment-responsive fashion to regulate the elevated levels of the ROS, which may also help downregulate the oxidative stress and promote tissue regeneration. A multitude of scaffolds and bioactive cues have been reported to promote the regeneration of damaged tissues based on the scavenging of free radicals and reactive species that confer high protection to the cellular activity and tissue function. In this review, we outline the underlying mechanism of ROS generation in the tissue microenvironment and present a comprehensive review of ROS-scavenging biomaterials for regenerative medicine and tissue engineering applications, including soft tissues regeneration, bone and cartilage repair as well as wound healing. Additionally, we highlight the strategies for the regulation of ROS by scaffold design and processing technology. Taken together, developing ROS-based biomaterials may not only help develop advanced platforms for improving injury microenvironment but also accelerate tissue regeneration.

ROS-Scavenging Therapeutic Hydrogels for Modulation of the Inflammatory Response

Although reactive oxygen species (ROS) are essential for cellular processes, excessive ROS could be a major cause of various inflammatory diseases because of the oxidation of proteins, DNA, and membrane lipids. It has recently been suggested that the amount of ROS could thus be regulated to treat such physiological disorders. A ROS-scavenging hydrogel is a promising candidate for therapeutic applications because of its high biocompatibility, 3D matrix, and ability to be modified. Approaches to conferring antioxidant properties to normal hydrogels include embedding ROS-scavenging catalytic nanoparticles, modifying hydrogel polymer chains with ROS-adsorbing organic moieties, and incorporating ROS-labile linkers in polymer backbones. Such therapeutic hydrogels can be used for wound healing, cardiovascular diseases, bone repair, ocular diseases, and neurodegenerative disorders. ROS-scavenging hydrogels could eliminate oxidative stress, accelerate the regeneration process, and show synergetic effects with other drugs or therapeutic molecules. In this review, the mechanisms by which ROS are generated and scavenged in the body are outlined, and the effects of high levels of ROS and the resulting oxidative stress on inflammatory diseases are described. Next, the mechanism of ROS scavenging by hydrogels is explained depending on the ROS-scavenging agents embedded within the hydrogel. Lastly, the recent achievements in the development of ROS-scavenging hydrogels to treat various inflammation-associated diseases are presented.

Exploration of sea anemone-inspired high-performance biomaterials with enhanced antioxidant activity

Antioxidant biomaterials have attracted much attention in various biomedical fields because of their effective inhibition and elimination of reactive oxygen species (ROS) in pathological tissues. However, the difficulty in ensuring biocompatibility, biodegradability and bioavailability of antioxidant materials has limited their further development. Novel bioavailable antioxidant materials that are derived from natural resources are urgently needed. Here, an integrated multi-omics method was applied to fabricate antioxidant biomaterials. A key cysteine-rich thrombospondin-1 type I repeat-like (TSRL) protein was efficiently discovered from among 1262 adhesive components and then used to create a recombinant protein with a yield of 500 mg L^-1. The biocompatible TSRL protein was able to self-assemble into either a water-resistant coating through Ca²⁺-mediated coordination or redox-responsive hydrogels with tunable physical properties. The TSRL-based hydrogels showed stronger 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging rates than glutathione (GSH) and ascorbic acid (Aa) and protected cells against external oxidative stress significantly more effectively. When topically applied to mice skin, TSRL alleviated epidermal hyperplasia and suppressed the degradation of collagen and elastic fibers caused by ultraviolet radiation B (UVB) irradiation, confirming that it enhanced antioxidant activity in vivo. This is the first study to successfully characterize natural antioxidant biomaterials created from marine invertebrate adhesives, and the findings indicate the excellent prospects of these biomaterials for great applications in tissue regeneration and cosmeceuticals.

Biomechanical Motion-Activated Endogenous Wound Healing through LBL Self-Powered Nanocomposite Repairer with pH-Responsive Anti-Inflammatory Effect

Wound care is still worthy of concern, and effective measures such as electrical stimulating therapy (EST) have sparked compellingly for wound repair. Especially, portable and point-of-care EST devices get extremely desired but these are often limited by inevitable external power sources, lack of biological functions, and mechanical properties conforming to skin tissue. Herein, a dress-on-person self-powered nanocomposite bioactive repairer of wound is designed. As such, the cooperation of the film prepared by layer-by-layer self-assembling 2-hydroxypropyltrimethyl ammonium chloride chitosan (HTCC), alginate (ALG), and poly-dopamine/Fe³⁺ nanoparticles (PFNs), with a self-powered nanogenerator (SN) driven by motion into a nanocomposite repairer (HAP/SN-NR) is conducted. The HAP/SN-NR not only guides cell behavior (proliferation and migration rate ≈61.7%, ≈52.3%), but also facilitates neovascularization (enhanced CD31 expression >4-fold) through its self-powered EST, and the endogenous wound closure with no inflammatory in rats owing to reactive oxygen species (ROS)-clearance of HAP/SN-NR in vitro/vivo through responsively releasing poly-dopamine nanoparticles at wound pH. Enormous efforts illustrate that the repairer is endowed with high self-adhesion to tissue, self-healing, and biodegradation, accelerating wound healing (50% closure ≈5 days). This strategy sheds light on novel multifunctional portable sensor-type dressings and propels the development of intelligent medical devices.

Membranous Extracellular Matrix-Based Scaffolds for Skin Wound Healing

Membranous extracellular matrix (ECM)-based scaffolds are one of the most promising biomaterials for skin wound healing, some of which, such as acellular dermal matrix, small intestinal submucosa, and amniotic membrane, have been clinically applied to treat chronic wounds with acceptable outcomes. Nevertheless, the wide clinical applications are always hindered by the poor mechanical properties, the uncontrollable degradation, and other factors after implantation. To highlight the feasible strategies to overcome the limitations, in this review, we first outline the current clinical use of traditional membranous ECM scaffolds for skin wound healing and briefly introduce the possible repair mechanisms; then, we discuss their potential limitations and further summarize recent advances in the scaffold modification and fabrication technologies that have been applied to engineer new ECM-based membranes. With the development of scaffold modification approaches, nanotechnology and material manufacturing techniques, various types of advanced ECM-based membranes have been reported in the literature. Importantly, they possess much better properties for skin wound healing, and would become promising candidates for future clinical translation.

Facile Polyphenol-Europium Assembly Enabled Functional Poly(l-Lactic Acid) Nanofiber Mats with Enhanced Antioxidation and Angiogenesis for Accelerated Wound Healing

Burns, trauma, surgery and chronic diabetic ulcers are the most common reasons causing skin wounds in clinic. Thus, developing a functional wound dressing has been an imperative issue. Herein, functional wound dressing (poly(l-lactic acid) PLLA-((tanic acid (TA)/europium (Eu))_n ) is fabricated through a facile polyphenol-europium ion assembly to ameliorate wound microenvironment via scavenging excessive reactive oxygen species (ROS) and promoting angiogenesis. The physicochemical characterization indicates that the multicycle assembled TA/Eu is uniformly deposited on PLLA-(TA/Eu)_n nanofiber mats surface. In vitro 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant tests display good antioxidant ability by scavenging more than 75% ROS, and significantly increasing the antioxidant enzyme levels in vivo. Cytocompatibility experiments illustrate that PLLA-(TA/Eu)_n nanofiber mats can promote the adhesion and proliferation of human umbilical vein endothelial cells (HUVECs) and L929 cells. Meanwhile, real-time quantitative polymerase chain reaction (PCR) (RT-qPCR) and western blot assays illustrate that it can stimulate proangiogenesis by elevating the expression of angiogenesis-related genes and proteins. In vivo Sprague-Dawley (SD) rats experiments indicate that PLLA-(TA/Eu)_n nanofiber mats can significantly promote wound healing by improving both angiogenesis and antioxidant activity. Taken together, the functional PLLA-(TA/Eu)_n nanofiber mats can offer significant promise as wound dressing for accelerated wound healing.