Injectable thioketal-containing hydrogel dressing accelerates skin wound healing with the incorporation of reactive oxygen species scavenging and growth factor release

ROS-responsive hydrogels: from design and additive manufacturing to biomedical applications

Hydrogels with intricate 3D networks and high hydrophilicity have qualities resembling those of biological tissues, making them ideal candidates for use as smart biomedical materials. Reactive oxygen species (ROS) responsive hydrogels are an innovative class of smart hydrogels, and are cross-linked by ROS-responsive modules through covalent interactions, coordination interactions, or supramolecular interactions. Due to the introduction of ROS response modules, this class of hydrogels exhibits a sensitive response to the oxidative stress microenvironment existing in organisms. Simultaneously, due to the modularity of the ROS-responsive structure, ROS-responsive hydrogels can be manufactured on a large scale through additive manufacturing. This review will delve into the design, fabrication, and applications of ROS-responsive hydrogels. The main goal is to clarify the chemical principles that govern the response mechanism of these hydrogels, further providing new perspectives and methods for designing responsive hydrogel materials.

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

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

Hydrogel-Based Growth Factor Delivery Platforms: Strategies and Recent Advances

Growth factors play a crucial role in regulating a broad variety of biological processes and are regarded as powerful therapeutic agents in tissue engineering and regenerative medicine in the past decades. However, their application is limited by their short half-lives and potential side effects in physiological environments. Hydrogels are identified as having the promising potential to prolong the half-lives of growth factors and mitigate their adverse effects by restricting them within the matrix to reduce their rapid proteolysis, burst release, and unwanted diffusion. This review discusses recent progress in the development of growth factor-containing hydrogels for various biomedical applications, including wound healing, brain tissue repair, cartilage and bone regeneration, and spinal cord injury repair. In addition, the review introduces strategies for optimizing growth factor release including affinity-based delivery, carrier-assisted delivery, stimuli-responsive delivery, spatial structure-based delivery, and cellular system-based delivery. Finally, the review presents current limitations and future research directions for growth factor-delivering hydrogels.

Fast-Gelling Polyethylene Glycol/Polyethyleneimine Hydrogels Degradable by Visible-Light

The treatment of burn wounds remains a clinical challenge due to the need for repeated dressings changes. Therefore, the development of a dressing system that can be atraumatically removed from the wound bed can be considered a breakthrough and improve treatment times. In this work, the development of an injectable, fast-gelling hydrogel is proposed that can change its mechanical properties when exposed to visible light. The hydrogels are prepared by a "click" amino-yne reaction between poly(ethylene glycol) (PEG) functionalized with propiolic acid and the amino groups of poly(ethyleneimine) (PEI). The hydrogels exhibit a fast gelation time, which can be adjusted by changing the weight percentage and molecular weight of the precursors. They also exhibit good swelling ability and adhesion to living tissues. More importantly, their mechanical properties changed upon irradiation with green light. This loss of properties is achieved by a 1 O2 -mediated mechanism, as confirmed by the degradation of the β-aminoacrylate linker. Moreover, the in vitro cell compatibility results of the hydrogels and their degradation products show good cytocompatibility. Therefore, it is believed that these hydrogels can be considered as materials with great potential for an innovative strategy for the treatment of burn wounds.

Cold-stored mulberry leaves affect antioxidant system and silk proteins of silkworm (Bombyx mori) larva

BACKGROUND

Cold storage has been widely used to maintain the quality of vegetables, but whether eating cold-stored vegetables affects health remains unknown.

RESULTS

This study used silkworms as an animal model to evaluate the effects of nutrient changes in cold-stored mulberry leaves (CSML) on health. Compared with fresh mulberry leaves (FML), CSML contained lower vitamin C, soluble sugars and proteins, and higher H2 O2 , suggesting decreased antioxidant ability and nutrition. The CSML did not obviously affect larval survival rate, body weight or dry matter rate, cocoon shape, weight and size, or final rates of cluster and cocooning relative to the FML, suggesting CSML did not alter overall growth and development. However, the CSML increased the initial rates of cluster and cocooning and upregulated BmRpd3, suggesting CSML shortened larval lifespan and enhanced senescence. CSML upregulated BmNOX4, downregulated BmCAT, BmSOD and BmGSH-Px and increased H2 O2 in silkworms, suggesting CSML caused oxidative stress. CSML upregulated ecdysone biosynthesis and inactivation genes and elevated ecdysone concentration in silkworms, suggesting that CSML affected hormone homeostasis. CSML upregulated apoptosis-related genes, downregulated sericin and silk fibroin genes and decreased sericin content rate in silkworms, suggesting oxidative stress and protein deficiency.

CONCLUSION

Cold storage reduced nutrition and antioxidant capability of mulberry leaves. CSML did not influence growth and development of silkworm larva, but affected health by causing oxidative stress and reducing protein synthesis. The findings show that the ingredient changes in CSML had negative effects on health of silkworms. © 2023 Society of Chemical Industry.

Reactive Oxygen Species-Scavenging Nanosystems in the Treatment of Diabetic Wounds

Diabetic wounds are characterized by drug-resistant bacterial infections, biofilm formation, impaired angiogenesis and perfusion, and oxidative damage to the microenvironment. Given their complex nature, diabetic wounds remain a major challenge in clinical practice. Reactive oxygen species (ROS), which have been shown to trigger hyperinflammation and excessive cellular apoptosis, play a pivotal role in the pathogenesis of diabetic wounds. ROS-scavenging nanosystems have recently emerged as smart and multifunctional nanomedicines with broad synergistic applicability. The documented anti-inflammatory and pro-angiogenic ability of ROS-scavenging treatments predestines these nanosystems as promising options for the treatment of diabetic wounds. Yet, in this context, the therapeutic applicability and efficacy of ROS-scavenging nanosystems remain to be elucidated. Herein, the role of ROS in diabetic wounds is deciphered, and the properties and strengths of nanosystems with ROS-scavenging capacity for the treatment of diabetic wounds are summarized. In addition, the current challenges of such nanosystems and their potential future directions are discussed through a clinical-translational lens.

Tannic acid-functionalized 3D porous nanofiber sponge for antibiotic-free wound healing with enhanced hemostasis, antibacterial, and antioxidant properties

Developing an antibiotic-free wound dressing with effective hemostasis and antibacterial and antioxidant capacity is highly desirable. In this work, a three-dimensional (3D) chitosan/polyvinyl alcohol-tannic acid porous nanofiber sponge (3D-TA) was prepared via electrospinning. Compared with two-dimensional (2D) fiber membrane, the unique fluffy 3D-TA nanofiber sponge had high porosity, water absorption and retention ability, hemostatic capacity. Furthermore, the 3D sponge functionalized by tannic acid (TA) endow the sponge with high antibacterial and antioxidant capacity without loading antibiotics. In addition, 3D-TA composite sponges have shown highly biocompatibility against L929 cells. The in vivo experiment shows the 3D-TA is enable to accelerate wound healing. This newly 3D-TA sponges hold great potential as wound dressings for future clinical application.

CuS Hybrid Hydrogel for Near-Infrared-Enhanced Infected Wound Healing: A Gelatin-Assisted Synthesis and Direct Incorporation Strategy

Developing antibacterial hydrogels, with good mechanical strength and self-healing ability to resist bacterial invasion and accelerate skin regeneration, is critical for infected full-thickness skin wound treatment. Herein, we report a gelatin-assisted synthesis and direct incorporation strategy to construct a CuS hybrid hydrogel for infected wound healing applications. CuS nanodots (NDs) were synthesized directly inside a gelatin host matrix (Gel-CuS), and these tightly confined and evenly distributed CuS NDs displayed superb dispersibility and stability against oxidation. Gel-CuS was then used to crosslink with oxidized dextran (ODex) to form a Gel-CuS-8/ODex hydrogel (8 stands for the concentration of CuS, in mM) via a facile Schiff-base reaction, which exhibited improved mechanical properties, excellent adhesion and self-healing ability, suitable swelling and degradation behavior, and good biocompatibility. The Gel-CuS-8/ODex hydrogel can act as an efficient antibacterial agent due to its photothermal and photodynamic properties under a 1064 nm laser irradiation. Furthermore, in animal experiments, when being applied as wound dressing, the Gel-CuS-8/ODex hydrogel significantly promoted infected full-thickness cutaneous wound healing through improved epidermis and granulation tissue formation and accelerated generation of new blood vessels, hair follicles, and collagen deposition after proper near-infrared irradiation treatment. This work provides a promising strategy to synthesize functional inorganic nanomaterials tightly and evenly embedded inside modified natural hydrogel networks for wound healing applications.

Chitosan, alginate, hyaluronic acid and other novel multifunctional hydrogel dressings for wound healing: A review

Wound healing is a complex project, and effectively promoting skin repair is a huge clinical challenge. Hydrogels have great prospect in the field of wound dressings because their physical properties are very similar to those of living tissue and have excellent properties such as high water content, oxygen permeability and softness. However, the single performance of traditional hydrogels limits their application as wound dressings. Therefore, natural polymers such as chitosan, alginate and hyaluronic acid, which are non-toxic and biocompatible, are individually or combined with other polymer materials, and loaded with typical drugs, bioactive molecules or nanomaterials. Then, the development of novel multifunctional hydrogel dressings with good antibacterial, self-healing, injectable and multi-stimulation responsiveness by using advanced technologies such as 3D printing, electrospinning and stem cell therapy has become a hot topic of current research. This paper focuses on the functional properties of novel multifunctional hydrogel dressings such as chitosan, alginate and hyaluronic acid, which lays the foundation for the research of novel hydrogel dressings with better performance.

Biomaterials releasing drug responsively to promote wound healing via regulation of pathological microenvironment

Wound healing is characterized by complex, orchestrated, spatiotemporal dynamic processes. Recent findings demonstrated suitable local microenvironments were necessities for wound healing. Wound microenvironments include various biological, biochemical and physical factors, which are produced and regulated by endogenous biomediators, exogenous drugs, and external environment. Successful drug delivery to wound is complicated, and need to overcome the destroyed blood supply, persistent inflammation and enzymes, spatiotemporal requirements of special supplements, and easy deactivation of drugs. Triggered by various factors from wound microenvironment itself or external elements, stimuli-responsive biomaterials have tremendous advantages of precise drug delivery and release. Here, we discuss recent advances of stimuli-responsive biomaterials to regulate local microenvironments during wound healing, emphasizing on the design and application of different biomaterials which respond to wound biological/biochemical microenvironments (ROS, pH, enzymes, glucose and glutathione), physical microenvironments (mechanical force, temperature, light, ultrasound, magnetic and electric field), and the combination modes. Moreover, several novel promising drug carriers (microbiota, metal-organic frameworks and microneedles) are also discussed.

Polysaccharides-Based Injectable Hydrogels: Preparation, Characteristics, and Biomedical Applications

Polysaccharides-based injectable hydrogels are a unique group of biodegradable and biocompatible materials that have shown great potential in the different biomedical fields. The biomolecules or cells can be simply blended with the hydrogel precursors with a high loading capacity by homogenous mixing. The different physical and chemical crosslinking approaches for preparing polysaccharide-based injectable hydrogels are reviewed. Additionally, the review highlights the recent work using polysaccharides-based injectable hydrogels as stimuli-responsive delivery vehicles for the controlled release of different therapeutic agents and viscoelastic matrix for cell encapsulation. Moreover, the application of polysaccharides-based injectable hydrogel in regenerative medicine as tissue scaffold and wound healing dressing is covered.

Elastomeric, bioadhesive and pH-responsive amphiphilic copolymers based on direct crosslinking of poly(glycerol sebacate)-co-polyethylene glycol

Poly(glycerol sebacate) (PGS), a synthetic biorubber, is characterised by its biocompatibility, high elasticity and tunable mechanical properties; however, its inherent hydrophobicity and insolubility in water make it unsuitable for use in advanced biomaterials like hydrogels fabrication. Here, we developed new hydrophilic PGS-based copolymers that enable hydrogel formation through use of two different types of polyethylene glycol (PEG), polyethylene glycol (PEG2) or glycerol ethoxylate (PEG3), combined at different ratios. A two-step polycondensation reaction was used to produce poly(glycerol sebacate)-co-polyethylene glycol (PGS-co-PEG) copolymers that were then crosslinked thermally without the use of initiators or crosslinkers, resulting in PGS-co-PEG2 and PGS-co-PEG3 amphiphilic polymers. It has been illustrated that the properties of PGS-co-PEG copolymers can be controlled by altering the type and amount of PEG. PGS-co-PEG copolymers containing PEG ≥ 40% showed high swelling, flexibility, stretching, bioadhesion and biocompatibility, and good enzymatic degradation and mechanical properties. Also, the addition of PEG created hydrogels that demonstrated pH-responsive behaviours, which can be used for bioapplications requiring responding to physicochemical dynamics. Interestingly, PGS-co-40PEG2 and PGS-co-60PEG3 had the highest shear strengths, 340.4 ± 49.7 kPa and 336.0 ± 35.1 kPa, and these are within the range of commercially available sealants or bioglues. Due to the versatile multifunctionalities of these new copolymer hydrogels, they can have great potential in soft tissue engineering and biomedicine.

Accelerating skin regeneration and wound healing by controlled ROS from photodynamic treatment

Cellular metabolisms produce reactive oxygen species (ROS) which are essential for cellular signaling pathways and physiological functions. Nevertheless, ROS act as “double-edged swords” that have an unstable redox balance between ROS production and removal. A little raise of ROS results in cell proliferation enhancement, survival, and soft immune responses, while a high level of ROS could lead to cellular damage consequently protein, nucleic acid, and lipid damages and finally cell death. ROS play an important role in various pathological circumstances. On the contrary, ROS can show selective toxicity which is used against cancer cells and pathogens. Photodynamic therapy (PDT) is based on three important components including a photosensitizer (PS), oxygen, and light. Upon excitation of the PS at a specific wavelength, the PDT process begins which leads to ROS generation. ROS produced during PDT could induce two different pathways. If PDT produces control and low ROS, it can lead to cell proliferation and differentiation. However, excess production of ROS by PDT causes cellular photo damage which is the main mechanism used in cancer treatment. This review summarizes the functions of ROS in living systems and describes role of PDT in production of controllable ROS and finally a special focus on current ROS-generating therapeutic protocols for regeneration and wound healing.

An injectable mitochondria-targeted nanodrug loaded-hydrogel for restoring mitochondrial function and hierarchically attenuating oxidative stress to reduce myocardial ischemia-reperfusion injury

Timely reperfusion is the common treatment for myocardial infarction. However, ischemia-reperfusion (I/R) therapy can lead to oxidative stress and mitochondrial dysfunction that further aggravate myocardial injury, and no effective therapy is currently available for alleviating myocardial I/R injury. Herein, we engineer a mitochondria-targeted Szeto-Schiller (SS31) peptide modified-amphiphilic polymer (PTPS) that self-assembles into nanomicelles (PTPSCs) for loading cyclosporine A (CsA). The PTPSCs are then encapsulated into a pH/ROS dual responsive injectable hydrogel crosslinked with reversible imine and boronic ester bonds. The loaded PTPSCs are controllably delivered from the hydrogel matrix in response to the low pH and high ROS microenvironment of the I/R heart, thus realizing reconstruction of mitochondrial function and unprecedented hierarchical attenuation of oxidative stress. The boronic ester in the hydrogel consumes the ROS in cardiac microenvironment, and the mitochondria-targeted delivery of CsA is revealed to inhibit mitochondria-mediated apoptosis signaling pathway to prevent cardiomyocyte apoptosis, meanwhile attenuating the mitochondrial ROS output to reduce the level of cytosolic ROS. Additionally, SS31 can also serve as an antioxidant to consume ROS in the mitochondria. In rat model of myocardial I/R injury with administration of this injectable hydrogel, the targeted release of PTPSCs efficiently restores mitochondrial and cardiac function.

ADSC-exo@MMP-PEG smart hydrogel promotes diabetic wound healing by optimizing cellular functions and relieving oxidative stress

Diabetic wound complications are financially costly and difficult to heal in worldwide. Whereas the therapies of diabetic wound, such as wound dressing, endocrine therapy or flap-transplantations, were not satisfied. Based on our previous study of exosome secreted by adipose-derived stem cell (ADSC-exo), we loaded ADSC-exo into the matrix metalloproteinase degradable polyethylene glycol (MMP-PEG) smart hydrogel. Physical and chemical properties of ADSC-exo@MMP-PEG smart hydrogel were tested by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), weight loss examination, etc. As the hydrogel degraded in response to MMP, ADSC-exo was released and subsequently enhanced cell function via Akt signaling. Moreover, treatment with ADSC-exo@MMP-PEG smart hydrogel significantly relieved the H₂O₂-induced oxidative stress, which was widely recognized as a major cause of diabetic wound nonhealing. Similar results were achieved in mice diabetic wound models, in which the ADSC-exo@MMP-PEG treatment group displayed a significantly accelerated wound healing. To summarize, the present smart hydrogel with enzyme-response and exosome-release was proved to be benefit for diabetic wounds healing, which provides a reliable theoretical basis for application of ADSC-exo in treatment of diabetic wounds.

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Loading ADSC-exo into PEG formed a smart hydrogel.

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The smart hydrogel delivered exosome in response to MMP-2.

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The smart hydrogel promoted diabetic wound healing by optimizing cellular functions.

Chitosan/Sodium Alginate/Velvet Antler Blood Peptides Hydrogel Promoted Wound Healing by Regulating PI3K/AKT/mTOR and SIRT1/NF-κB Pathways

Skin wound healing is a principal clinical challenge, and it is necessary to develop effective alternative treatments. Excessive inflammatory response is linked to delayed healing. This study was the first to report a multi-functional chitosan/sodium alginate/velvet antler blood peptides (VBPs) hydrogel (CAVBPH) and explore its potential mechanism to promote wound healing. The results showed that CAVBPH possessed desirable characteristics including thermo-sensitivity, antioxidation, antibacterial activity, biosafety, VBPs release behavior, etc., and significantly accelerated skin wound healing in mice. Specifically, the CAVBPH treatment enhanced cell proliferation, angiogenesis, and extracellular matrix (ECM) secretion, and also relieved inflammation at the wound site compared to the PBS-treated group and blank hydrogel scaffold-treated group. Mechanistically, the efficacy of CAVBPH might be related to the activation of the PI3K/AKT/mTOR and SIRT1/NF-κB pathways. Overall, CAVBPH seems to be a promising therapy for skin repair, probably relying on the abundant short-chain peptides in VBPs.

Progress in hydrogels for skin wound repair

As the first defensive line between the human body and the outside world, the skin is vulnerable to damage from the external environment. Skin wounds can be divided into acute wounds (mechanical injuries, chemical injuries and surgical wounds, etc.) and chronic wounds (burns, infections, diabetes, etc.). In order to manage skin wound, a variety of wound dressings have been developed, including gauze, films, foams, nanofibers, hydrocolloids and hydrogels. Recently, hydrogels have received much attention because of their natural extracellular matrix (ECM)-mimik structure, tunable mechanical properties, and facile bioactive substance delivery capability. They show great potential application in skin wound repair. This paper first introduces the anatomy and function of the skin, the process of wound healing and conventional wound dressings, and then introduces the composition and construction methods of hydrogels. Next, this paper introduces the necessary properties of hydrogels in skin wound repair and the latest research progress of hydrogel dressings for skin wound repair. Finally, the future development goals of hydrogel materials in the field of wound healing are proposed. This article is protected by copyright. All rights reserved.

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.

Rational design of flexible microneedles coupled with CaO2@PDA-loaded nanofiber films for skin wound healing on diabetic rats

Skin ulcers is one of the complications of diabetes. At present, the treatment of diabetic skin wound is still not satisfactory, and the efficiency of drug delivery is limited by the depth...