Hydrogel Dressings for Advanced Wound Management

Insights of biopolymeric blended formulations for diabetic wound healing

Diabetic wounds (DWs) pose a significant health burden worldwide, with their management presenting numerous challenges. Biopolymeric formulations have recently gained attention as promising therapeutic approaches for diabetic wound healing. These formulations, composed of biocompatible and biodegradable polymers, offer unique properties such as controlled drug release, enhanced wound closure, and reduced scarring. In this review, we aim to provide a comprehensive overview of the current state of research and future prospects regarding the application of biopolymeric formulations for diabetic wound healing. The review begins by highlighting the underlying pathophysiology of DWs, including impaired angiogenesis, chronic inflammation, and compromised extracellular matrix (ECM) formation. It further explores the key characteristics of biopolymeric materials, such as their biocompatibility, biodegradability, and tunable physicochemical properties, which make them suitable for diabetic wound healing applications. The discussion further delves into the types of biopolymeric formulations utilized in the treatment of DWs. These include hydrogels, nanoparticles (NP), scaffolds, films, and dressings. Furthermore, the review addresses the challenges associated with biopolymeric formulations for diabetic wound healing. In conclusion, biopolymeric formulations present a promising avenue for diabetic wound healing. Their unique properties and versatility allow for tailored approaches to address the specific challenges associated with DWs. However, further research and developments are required to optimize their therapeutic efficacy, stability, manufacturing processes, and regulatory considerations. With continued advancements in biopolymeric formulations, the future holds great promise for improving the management and outcomes of DWs.

Versatile dopamine-functionalized hyaluronic acid-recombinant human collagen hydrogel promoting diabetic wound healing via inflammation control and vascularization tissue regeneration

The management of chronic wounds in diabetes remains challenging due to the complexity of impaired wound healing, delayed healing, susceptibility to infection, and elevated risk of reopening, highlighting the need for effective chronic wound management with innovative approaches such as multifunctional hydrogels. Here, we have produced HA-DA@rhCol hydrogels consisting of dopamine-modified hyaluronic acid and recombinant human collagen type-III (rhCol) by oxidative coupling of the catechol group using the H2O2/HRP catalytic system. The post-reactive hydrogel has a good porous structure, swelling rate, reasonable degradation, rheological and mechanical properties, and the catechol group and dopamine impart to the hydrogel tissue adhesiveness, antioxidant capacity, and excellent photothermal effects leading to superior in vitro antimicrobial activity. In addition, the ability of rhCol to confer hydrogels to promote angiogenesis and wound repair has also been investigated. Cytotoxicity and hemolysis tests demonstrated the good biocompatibility of the hydrogel. Wound closure, collagen deposition and immunohistochemical examination confirmed the ability of the hydrogel to promote diabetic wound healing. In summary, the adhesive hemostatic antioxidative hydrogel with rhCol to promote wound healing in diabetic rat is an excellent chronic wound dressing.

Modulating macrophage phenotype for accelerated wound healing with chlorogenic acid-loaded nanocomposite hydrogel

Wound healing involves distinct phases, including hemostasis, inflammation, proliferation, and remodeling, which is a complex and dynamic process. Conventional preparations often fail to meet multiple demands and provide prompt information about wound status. Here, a pH/ROS dual-responsive hydrogel (OHA-PP@Z-CA@EGF) was constructed based on oxidized hyaluronic acid (OHA), phenylboronic acid-grafted ε-polylysine (PP), chlorogenic acid (CA)-loaded ZIF-8 (Z-CA), and epidermal growth factor (EGF), which possesses intrinsic antibacterial, antioxidant, and angiogenic capacities. Due to the Schiff base and Phenylboronate ester bonds, the hydrogel exhibited excellent mechanical properties, strong adhesion, good biodegradability, high biocompatibility, stable rheological properties, and self-healing ability. Moreover, introducing Z-CA as an initiator and nanofiller led to the additional cross-linking of hydrogel through coordination bonds, which further improved the mechanical properties and antioxidant capabilities. Bleeding models of liver and tail amputations demonstrated rapid hemostatic properties of the hydrogel. Besides, the hydrogel regulated macrophage phenotypes via the NF-κB/JAK-STAT pathways, relieved oxidative stress, promoted cell migration and angiogenesis, and accelerated diabetic wound healing. The hydrogel also enabled real-time monitoring of the wound healing stages by colorimetric detection. This multifunctional hydrogel opens new avenues for the treatment and management of full-thickness diabetic wounds.

Narrative review on nanoparticles based on current evidence: therapeutic agents for diabetic foot infection

Diabetes's effects on wound healing present a major treatment challenge and increase the risk of amputation. When traditional therapies fail, new approaches must be investigated. With their submicron size and improved cellular internalisation, nanoparticles present a viable way to improve diabetic wound healing. They are attractive options because of their innate antibacterial qualities, biocompatibility, and biodegradability. Nanoparticles loaded with organic or inorganic compounds, or embedded in biomimetic matrices such as hydrogels, chitosan, and hyaluronic acid, exhibit excellent anti-inflammatory, antibacterial, and antioxidant properties. Drug delivery systems (DDSs)-more precisely, nanodrug delivery systems (NDDSs)-use the advantages of nanotechnology to get around some of the drawbacks of traditional DDSs. Recent developments show how expertly designed nanocarriers can carry a variety of chemicals, transforming the treatment of diabetic wounds. Biomaterials that deliver customised medications to the wound microenvironment demonstrate potential. Delivery techniques for nanomedicines become more potent than ever, overcoming conventional constraints. Therapeutics for diabetes-induced non-healing wounds are entering a revolutionary era thanks to precisely calibrated nanocarriers that effectively distribute chemicals. This review highlights the therapeutic potential of nanoparticles and outlines the multifunctional nanoparticles of the future that will be used for complete wound healing in diabetics. The investigation of novel nanodrug delivery systems has the potential to revolutionise diabetic wound therapy and provide hope for more efficient and focused therapeutic approaches.

Green Synthesis and Biosafety Assessment of MXene

The rise of MXene-based materials with fascinating physical and chemical properties has attracted wide attention in the field of biomedicine, because it can be exploited to regulate a variety of biological processes. The biomedical applications of MXene are still in its infancy, nevertheless, the comprehensive evaluation of MXene's biosafety is desperately needed. In this review, the composition and the synthetic methods of MXene materials are first introduced from the view of biosafety. The evaluation of the interaction between MXene and cells, as well as the safety of different forms of MXene applied in vivo are then discussed. This review provides a basic understanding of MXene biosafety and may bring new inspirations to the future applications of MXene-based materials in biomedicine.

Enhanced antibacterial activity of porous chitosan-based hydrogels crosslinked with gelatin and metal ions

Addressing the increasing drug resistance in pathogenic microbes, a significant threat to public health, calls for the development of innovative antibacterial agents with versatile capabilities. To enhance the antimicrobial activity of non-toxic biomaterials in this regard, this study focuses on novel, cost-effective chitosan (CS)-based hydrogels, crosslinked using gelatin (GEL), formaldehyde, and metallic salts (Ag+, Cu2+, and Zn2+). These hydrogels are formed by mixing CS and GEL with formaldehyde, creating iminium ion crosslinks with metallic salts without hazardous crosslinkers. Characterization techniques like FTIR, XRD, FESEM, EDX, and rheological tests were employed. FTIR analysis showed metal ions binding to amino and hydroxyl groups on CS, enhancing hydrogelation. FESEM revealed that freeze-dried hydrogels possess a crosslinked, porous structure influenced by various metal ions. Antibacterial testing against gram-negative and gram-positive bacteria demonstrated significant bacterial growth inhibition. CS-based hydrogels containing metal ions showed reduced MIC and MBC values against Staphylococcus aureus (0.5, 8, 16 µg/mL) and Escherichia coli (1, 16, 8 µg/mL) for CS-g-GEL-Ag+, CS-g-GEL-Cu2+, and CS-g-GEL-Zn2+. MTT assay results confirmed high biocompatibility (84.27%, 85.24%, 84.96% viability at 10 µg/mL) for CS-based hydrogels towards HFF-1 cells over 48 h. Therefore, due to their non-toxic nature, these CS hydrogels are promising for antibacterial applications.

Efficient healing of diabetic wounds by MSC-EV-7A composite hydrogel via suppression of inflammation and enhancement of angiogenesis

Diabetes mellitus (DM) is characterized by prolonged hyperglycemia, impaired vascularization, and serious complications, such as blindness and chronic diabetic wounds. About 25% of patients with DM are estimated to encounter impaired healing of diabetic wounds, often leading to lower limb amputation. Multiple factors are attributed to the non-healing of diabetic wounds, including hyperglycaemia, chronic inflammation, and impaired angiogenesis. It is imperative to develop more efficient treatment strategies to tackle healing difficulties in diabetic wounds. Mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) are promising for diabetic wound healing considering their anti-inflammatory, pro-angiogenic and pro-proliferative activities. A histone deacetylase 7 (HDAC7)-derived 7-amino-acid peptide (7A) was shown to be highly effective for angiogenesis. However, it has never been investigated whether MSC-EVs are synergistic with 7A for the healing of diabetic wounds. Herein, we propose that MSC-EVs can be combined with 7A to greatly promote diabetic wound healing. The combination of EVs and 7A significantly improved the migration and proliferation of skin fibroblasts. Moreover, EVs alone significantly suppressed LPS-induced inflammation in macrophages, and notably, the combination treatment showed an even better suppression effect. Importantly, the in vivo study revealed that the combination therapy consisting of EVs and 7A in an alginate hydrogel was more efficient for the healing of diabetic wounds in rats than monotherapy using either EV or 7A hydrogels. The underlying mechanisms include suppression of inflammation, improvement of skin cell proliferation and migration, and enhanced collagen fiber disposition and angiogenesis in wounds. In summary, the MSC-EV-7A hydrogel potentially constitutes a novel therapy for efficient healing of chronic diabetic wounds.

Antibacterial Micelles-Loaded Carboxymethyl Chitosan/Oxidized Konjac Glucomannan Composite Hydrogels for Enhanced Wound Repairing

Antibacterial hydrogels have emerged as a promising approach for effective wound treatment. However, despite extensive research on the fabrication of antibacterial hydrogels, it remains challenging to develop injectable, biocompatible, transparent, and mass-producible hydrogels with antibacterial properties. In this study, we successfully fabricated an antibacterial drug-loaded composite hydrogel, named CC45/OKG40/HS, through a Schiff base reaction between carboxymethyl chitosan (CC) and oxidized konjac glucomannan (OKG), followed by the encapsulation of stevioside-stabilized honokiol (HS) micelles. The CC45/OKG40/HS hydrogel exhibited several favorable properties, including a short gel time (<10 min), high water content (>92%), injectability, good adhesiveness, self-healing ability, and high transparency. In vitro experiments confirmed its excellent antibacterial properties, antioxidant activities, and high biocompatibility (no cytotoxicity, hemolysis ratio <5%). Furthermore, in vivo evaluation demonstrated that the CC45/OKG40/HS0.5 hydrogel accelerated wound healing by relieving inflammatory responses and enhancing re-epithelization. Given its feasibility for mass production, the findings showed that the CC45/OKG40/HS hydrogel has the potential as an advanced antibacterial wound dressing for commercial use.

A Nanocomposite Dynamic Covalent Cross-Linked Hydrogel Loaded with Fusidic Acid for Treating Antibiotic-Resistant Infected Wounds

Methicillin-resistant Staphylococcus aureus (MRSA) is associated with high levels of morbidity and is considered a difficult-to-treat infection, often requiring nonstandard treatment regimens and antibiotics. Since over 40% of the emerging antibiotic compounds have insufficient solubility that limits their bioavailability and thus efficacy through oral or intravenous administration, it is crucial that alternative drug delivery products be developed for wound care applications. Existing effective treatments for soft tissue MRSA infections, such as fusidic acid (FA), which is typically administered orally, could also benefit from alternative routes of administration to improve local efficacy and bioavailability while reducing the required therapeutic dose. Herein, we report an antimicrobial poly(oligoethylene glycol methacrylate) (POEGMA)-based composite hydrogel loaded with fusidic acid-encapsulating self-assembled polylactic acid-b-poly(oligo(ethylene glycol) methyl ether methacrylate) (PLA-POEGMA) nanoparticles for the treatment of MRSA-infected skin wounds. The inclusion of the self-assembled nanoparticles (380 nm diameter when loaded with fusidic acid) does not alter the favorable mechanical properties and stability of the hydrogel in the context of its use as a wound dressing, while fusidic acid (FA) can be released from the hydrogel over ∼10 h via a diffusion-controlled mechanism. The antimicrobial studies demonstrate a clear zone of inhibition in vitro and a 1-2 order of magnitude inhibition of bacterial growth in vivo in an MRSA-infected full-thickness excisional murine wound model even at very low antibiotic doses. Our approach thus can both circumvent challenges in the local delivery of hydrophobic antimicrobial compounds and directly deliver antimicrobials into the wound to effectively combat methicillin-resistant infections using a fraction of the drug dose required using other clinically relevant strategies.

Research progress on hydrogel-based drug therapy in melanoma immunotherapy

Melanoma is one of the most aggressive skin tumors, and conventional treatment modalities are not effective in treating advanced melanoma. Although immunotherapy is an effective treatment for melanoma, it has disadvantages, such as a poor response rate and serious systemic immune-related toxic side effects. The main solution to this problem is the use of biological materials such as hydrogels to reduce these side effects and amplify the immune killing effect against tumor cells. Hydrogels have great advantages as local slow-release drug carriers, including the ability to deliver antitumor drugs directly to the tumor site, enhance the local drug concentration in tumor tissue, reduce systemic drug distribution and exhibit good degradability. Despite these advantages, there has been limited research on the application of hydrogels in melanoma treatment. Therefore, this article provides a comprehensive review of the potential application of hydrogels in melanoma immunotherapy. Hydrogels can serve as carriers for sustained drug delivery, enabling the targeted and localized delivery of drugs with minimal systemic side effects. This approach has the potential to improve the efficacy of immunotherapy for melanoma. Thus, the use of hydrogels as drug delivery vehicles for melanoma immunotherapy has great potential and warrants further exploration. [BMB Reports 2024; 57(2): 71-78].

Designing Composite Stimuli-Responsive Hydrogels for Wound Healing Applications: The State-of-the-Art and Recent Discoveries

Effective wound treatment has become one of the most important challenges for healthcare as it continues to be one of the leading causes of death worldwide. Therefore, wound care technologies significantly evolved in order to provide a holistic approach based on various designs of functional wound dressings. Among them, hydrogels have been widely used for wound treatment due to their biocompatibility and similarity to the extracellular matrix. The hydrogel formula offers the control of an optimal wound moisture level due to its ability to absorb excess fluid from the wound or release moisture as needed. Additionally, hydrogels can be successfully integrated with a plethora of biologically active components (e.g., nanoparticles, pharmaceuticals, natural extracts, peptides), thus enhancing the performance of resulting composite hydrogels in wound healing applications. In this review, the-state-of-the-art discoveries related to stimuli-responsive hydrogel-based dressings have been summarized, taking into account their antimicrobial, anti-inflammatory, antioxidant, and hemostatic properties, as well as other effects (e.g., re-epithelialization, vascularization, and restoration of the tissue) resulting from their use.

Biomolecules based hydrogels and their potential biomedical applications: A comprehensive review

The need for biocompatible drug carriers has been significantly increased from the past few years. Researchers show great interest in the development of more versatile and sophisticated biomaterials based drug carriers. Hydrogels are beneficial drug carriers and easily release the controlled amount of drug at target site due to its tunable structure. The hydrogels made-up of potent biological macromolecules including collagen, gelatin, fibrin, elastin, fibroin, chitosan, starch, alginate, agarose and carrageenan have been proven as versatile biomaterials. These are three-dimensional polymeric networks, synthesized by crosslinking of hydrophilic polymers. The biological macromolecules based hydrogels containing therapeutic substances are used in a wide range of biomedical applications including wound healing, tissue engineering, cosmetics and contact lenses. However, many aspects related to hydrogels such as the mechanism of cross-linking and molecular entanglement are not clear. So, there is a need to do more research and exploration toward the extensive and cost-effective use of hydrogels. The present review article elaborately discusses the biomolecules based hydrogels and their possible biomedical applications in different fields.

Development of an In Situ Photo-Crosslinking Antimicrobial Collagen Hydrogel for the Treatment of Infected Wounds

Antimicrobial hydrogels have received considerable attention in the treatment of bacteria-infected wounds. Herein, we develop a neutral, soluble collagen via modification with maleic anhydride, serving as a hydrogel precursor. Maleic anhydride-modified collagen (ColME) could form a gel after exposure to UV light and be loaded with the antimicrobial agents, nisin and levofloxacin, to acquire antimicrobial ability. The ColME hydrogel containing nisin and levofloxacin had good cytocompatibility and effectively killed pathogenic bacterial strains, such as Escherichia coli and Staphylococcus aureus. The antimicrobial ColME hydrogels effectively supported the healing of a full-thickness skin wound infected with S. aureus in a mouse model. Our results demonstrate the potential of antimicrobial hydrogels as effective wound dressings via in situ photogelation for the healing of infected wounds.

Stem cell-derived small extracellular vesicles embedded into methacrylated hyaluronic acid wound dressings accelerate wound repair in a pressure model of diabetic ulcer

Over the past years, the development of innovative smart wound dressings is revolutionizing wound care management and research. Specifically, in the treatment of diabetic foot wounds, three-dimensional (3D) bioprinted patches may enable personalized medicine therapies. In the present work, a methacrylated hyaluronic acid (MeHA) bioink is employed to manufacture 3D printed patches to deliver small extracellular vesicles (sEVs) obtained from human mesenchymal stem cells (MSC-sEVs). The production of sEVs is maximized culturing MSCs in bioreactor. A series of in vitro analyses are carried out to demonstrate the influence of MSC-sEVs on functions of dermal fibroblasts and endothelial cells, which are the primary functional cells in skin repair process. Results demonstrate that both cell populations are able to internalize MSC-sEVs and that the exposure to sEVs stimulates proliferation and migration. In vivo experiments in a well-established diabetic mouse model of pressure ulcer confirm the regenerative properties of MSC-sEVs. The MeHA patch enhances the effectiveness of sEVs by enabling controlled release of MSC-sEVs over 7 days, which improve wound epithelialization, angiogenesis and innervation. The overall findings highlight that MSC-sEVs loading in 3D printed biomaterials represents a powerful technique, which can improve the translational potential of parental stem cell in terms of regulatory and economic impact.

Four-dimensional hydrogel dressing adaptable to the urethral microenvironment for scarless urethral reconstruction

The harsh urethral microenvironment (UME) after trauma severely hinders the current hydrogel-based urethral repair. In fact, four-dimensional (4D) consideration to mimic time-dependent physiological processes is essential for scarless urethral reconstruction, which requires balancing extracellular matrix (ECM) deposition and remodeling at different healing stages. In this study, we develop a UME-adaptable 4D hydrogel dressing to sequentially provide an early-vascularized microenvironment and later-antifibrogenic microenvironment for scarless urethral reconstruction. With the combination of dynamic boronic ester crosslinking and covalent photopolymerization, the resultant gelatin methacryloyl phenylboronic acid/cis-diol-crosslinked (GMPD) hydrogels exhibit mussel-mimetic viscoelasticity, satisfactory adhesion, and acid-reinforced stability, which can adapt to harsh UME. In addition, a temporally on-demand regulatory (TOR) technical platform is introduced into GMPD hydrogels to create a time-dependent 4D microenvironment. As a result, physiological urethral recovery is successfully mimicked by means of an early-vascularized microenvironment to promote wound healing by activating the vascular endothelial growth factor (VEGF) signaling pathway, as well as a later-antifibrogenic microenvironment to prevent hypertrophic scar formation by timing transforming growth factor-β (TGFβ) signaling pathway inhibition. Both in vitro molecular mechanisms of the physiological healing process and in vivo scarless urethral reconstruction in a rabbit model are effectively verified, providing a promising alternative for urethral injury treatment.

Advances in the Applications of Extracellular Vesicle for the Treatment of Skin Photoaging: A Comprehensive Review

Skin photoaging is a complex biological process characterized by the accumulation of oxidative damage and structural changes in the skin, resulting from chronic exposure to ultraviolet (UV) radiation. Despite the growing demand for effective treatments, current therapeutic options for skin photoaging remain limited. However, emerging research has highlighted the potential of extracellular vesicles (EVs), including exosomes, micro-vesicles, apoptotic bodies and liposomes, as promising therapeutic agents in skin rejuvenation. EVs are involved in intercellular communication and can deliver bioactive molecules, including proteins, nucleic acids, and lipids, to recipient cells, thereby influencing various cellular processes. This comprehensive review aims to summarize the current research progress in the application of EVs for the treatment of skin photoaging, including their isolation and characterization methods, roles in skin homeostasis, therapeutic potential and clinical applications for skin photoaging. Additionally, challenges and future directions in EVs-based therapies for skin rejuvenation are discussed.

Sprayable ciprofloxacin-loaded poloxamer hydrogels for wound infection treatment

Topical antimicrobial treatments for severe burns and chronic wounds provide effective treatment against infections, but cause pain and discomfort with application. This study aimed to develop an antimicrobial topical formulation comprising thermoreversible poloxamers (Pluronic F127 and F68) and a broad-spectrum antimicrobial agent (ciprofloxacin hydrochloride, CH), that could be sprayed to eliminate application pain while maintaining antimicrobial activity. Formulations were characterized to determine their sprayability under cold conditions, gelation temperature, final storage modulus at skin temperature, drug release profile, ex vivo permeation through impaired porcine skin, and inhibition against common bacterial pathogens that colonize wounds. All cold formulations were sprayable from simple hand-held, pump-action sprayers due to their low viscosity. Upon heating, 17 and 20% Pluronic F127 formulations produced hydrogels eight to ten degrees below skin temperature, independent of ciprofloxacin loading. Increasing concentrations of Pluronic F127 increased the final storage modulus and viscosity of the gels, while inclusion of Pluronic F68 reduced these properties, showing that hydrogel rheological properties at skin temperature can be tuned via choice of formulation. Drug release was directly correlated to the rheological properties, with stiffer gels resulting in a decrease in drug release rate. Overall, gels released about 65-90% of their load within 12 hours. Ex vivo skin permeation demonstrated that drug was well retained in impaired porcine skin, which is desired to continuously treat bacteria localized to the wound. A well-diffusion assay indicated that the hydrogels had greater bacterial inhibition against Pseudomonas aeruginosa, Escherichia coli, and two strains of Staphylococcus aureus when compared to commercial controls. Overall, the results show the potential of CH-loaded poloxamer formulations as suitable sprayable topical dressings to deliver antimicrobials directly to wounds.

Recent advances in biosensors for real time monitoring of pH, temperature, and oxygen in chronic wounds

Chronic wounds are among the major healthcare issues affecting millions of people worldwide with high rates of morbidity, losses of limbs and mortality. Microbial infection in wounds is a severe problem that can impede healing of chronic wounds. Accurate, timely and early detection of infections, and real time monitoring of various wound healing biomarkers related to infection can be significantly helpful in the treatment and care of chronic wounds. However, clinical methodologies of periodic assessment and care of wounds require physical visit to wound care clinics or hospitals and time-consuming frequent replacement of wound dressing patches, which also often adversely affect the healing process. Besides, frequent replacements of wound dressings are highly expensive, causing a huge amount of burden on the national health care systems. Smart bandages have emerged to provide in situ physiochemical surveillance in real time at the wound site. These bandages integrate smart sensors to detect the condition of wound infection based on various parameters, such as pH, temperature and oxygen level in the wound which reduces the frequency of changing the wound dressings and its associated complications. These devices can continually monitor the healing process, paving the way for tailored therapy and improved quality of patient's life. In this review, we present an overview of recent advances in biosensors for real time monitoring of pH, temperature, and oxygen in chronic wounds in order to assess infection status. We have elaborated the recent progress in quantitative monitoring of several biomarkers important for assessing wounds infection status and its detection using smart biosensors. The review shows that real-time monitoring of wound status by quantifying specific biomarkers, such as pH, temperature and tissue oxygenation to significantly aid the treatment and care of chronic infected wounds.

Gel/hydrogel-based in situ biomaterial platforms for cancer postoperative treatment and recovery

Tumor surgical resection is the major strategy for cancer treatment. Meanwhile, perioperative treatment especially the postoperative adjuvant anticancer strategies play essential roles in satisfying therapeutic results and rapid recovery. Postoperative tumor recurrence, metastasis, bleeding, inter-tissue adhesion, infection, and delayed wound healing are vital risks that could lead to poor prognosis or even treatment failure. Therefore, methods targeting these postoperative complications are in desperate need. In situ biomaterial-based drug delivery platforms are promising candidates for postoperative treatment and recovery, resulting from their excellent properties including good biocompatibility, adaptive shape, limited systemic effect, designable function, and easy drug loading. In this review, we focus on introducing the gel/hydrogel-based in situ biomaterial platforms involving their properties, advantages, and synthesis procedures. Based on the loaded contents in the gel/hydrogel such as anticancer drugs, immunologic agents, cell components, and multifunctional nanoparticles, we further discuss the applications of the in situ platforms for postoperative tumor recurrence and metastasis inhibition. Finally, other functions aiming at fast postoperative recovery were introduced, including hemostasis, antibacterial infection, adhesion prevention, tissue repair, and wound healing. In conclusion, gel/hydrogel is a developing and promising platform for postoperative treatment, exhibiting gratifying therapeutic effects and inconspicuous toxicity to normal tissues, which deserves further research and exploration.

Carboxymethyl Chitosan Hydrogels for Effective Wound Healing-An Animal Study

Hydrogels have various applications in medicine, for example, in systems for controlled drug release or as wound dressings, where they provide an appropriate environment for healing and constitute a barrier to microorganisms. The aim of this study was to evaluate the action of carboxymethyl chitosan (CMCS) hydrogels in wound healing therapy in vivo using a laboratory rat model. The hydrogels were formed from aqueous solutions of a CMCS biopolymer via electron beam irradiation, with the presence of a crosslinking agent of poly(ethylene glycol) diacrylate. A histopathological examination of injured tissue, using a model of a hard-to-heal wound, indicated that the CMCS hydrogel supported healing. The new gel dressing, being noncytotoxic, presents great potential in wound treatment, with positive effects on the amount of inflammatory infiltration, young collagen formation, and the degree of epidermalization. A key advantage of the current approach (i.e., using competitive radiation technology for synthesis) is that it includes only one step, with the product being sterilized as it is synthesized. The hydrogel effectively supports wound healing and can serve as a bio-based and biodegradable platform for other medical applications.

Polysaccharide-based hydrogel promotes skin wound repair and research progress on its repair mechanism

Polysaccharides, being a natural, active, and biodegradable polymer, have garnered significant attention due to their exceptional properties. These properties make them ideal for creating multifunctional hydrogels that can be used as wound dressings for skin injuries. Polysaccharide hydrogel has the ability to both simulate the natural extracellular matrix, promote cell proliferation, and provide a suitable environment for wound healing while protecting it from bacterial invasion. Polysaccharide hydrogels offer a promising solution for repairing damaged skin. This review provides an overview of the mechanisms involved in skin damage repair and emphasizes the potential of polysaccharide hydrogels in this regard. For different skin injuries, polysaccharide hydrogels can play a role in promoting wound healing. However, we still need to conduct more research on polysaccharide hydrogels to provide more possibilities for skin damage repair.

Emergence of Nano-Based Formulations for Effective Delivery of Flavonoids against Topical Infectious Disorders

Flavonoids are hydroxylated phenolic substances in vegetables, fruits, flowers, seeds, wine, tea, nuts, propolis, and honey. They belong to a versatile category of natural polyphenolic compounds. Their biological function depends on various factors such as their chemical structure, degree of hydroxylation, degree of polymerization conjugation, and substitutions. Flavonoids have gained considerable attention among researchers, as they show a wide range of pharmacological activities, including coronary heart disease prevention, antioxidative, hepatoprotective, anti-inflammatory, free-radical scavenging, anticancer, and anti-atherosclerotic activities. Plants synthesize flavonoid compounds in response to pathogen attacks, and these compounds exhibit potent antimicrobial (antibacterial, antifungal, and antiviral) activity against a wide range of pathogenic microorganisms. However, certain antibacterial flavonoids have the ability to selectively target the cell wall of bacteria and inhibit virulence factors, including biofilm formation. Moreover, some flavonoids are known to reverse antibiotic resistance and enhance the efficacy of existing antibiotic drugs. However, due to their poor solubility in water, flavonoids have limited oral bioavailability. They are quickly metabolized in the gastrointestinal region, which limits their ability to prevent and treat various disorders. The integration of flavonoids into nanomedicine constitutes a viable strategy for achieving efficient cutaneous delivery owing to their favorable encapsulation capacity and diminished toxicity. The utilization of nanoparticles or nanoformulations facilitates drug delivery by targeting the drug to the specific site of action and exhibits excellent physicochemical stability.

Chitosan-based double network hydrogel loading herbal small molecule for accelerating wound healing

Skin injuries are one of the most common clinical traumas worldwide, and wound dressings are considered to be one of key factors in wound healing. Natural polymer-based hydrogels have been developed as ideal materials for a new generation of dressings due to their excellent biocompatibility and wetting ability. However, the inadequate mechanical performances and lack of efficacy in promoting wound healing have limited the application of natural polymer-based hydrogels as wound dressings. In this work, a double network hydrogel based on natural chitosan molecules was constructed to enhance the mechanical properties, and emodin, a herbal natural product, was loaded into the hydrogel to improve the healing effect of the dressing. The structure of the chitosan-emodin network formed by Schiff base reaction and microcrystalline network of biocompatible polyvinyl alcohol endowed hydrogels with excellent mechanical properties and ensured its integrity as wound dressings. Moreover, the hydrogel showed excellent wound healing properties due to the loading of emodin. The hydrogel dressing could promote cell proliferation, cell migration, and secretion of growth factors. The animal experimental results also demonstrated that the hydrogel dressing facilitated the regeneration of blood vessels and collagen and accelerated wound healing.

Bismuth Oxide Composite-Based Agricultural Waste for Wound Dressing Applications

The purpose of this study was to enhance the antimicrobial activity of bagasse paper by coating the paper with bismuth oxide (Bi2O3) and using it to accelerate the process of wound healing. Paper sheets were prepared from sugarcane waste (bagasse). First, the paper sheets were coated with different Bi2O3 concentrations to improve the antimicrobial activity of the paper. After that, the paper sheets were allowed to dry in an oven at 50 °C for 3 h. Then, in vitro antimicrobial activity was evaluated against different microbial species, including Gram-negative bacteria (i.e., Klebsiella pneumonia, Escherichia coli) and Gram-positive bacteria (i.e., Staphylococcus aureus, Streptococcus pyogenes). The obtained results showed that the paper coated with 25% and 100% Bi2O3 had activity against all models of bacteria; however, the paper coated with 100% Bi2O3 composite had the strongest inhibitory effect. Then, bagasse paper was coated with 100% Bi2O3 and different antibiotics, to investigate their wound-healing potency in a wounded rat model for 14 days. Moreover, the paper coated with 100% Bi2O3 inhibited the cellular migration in vitro. Conclusively, coating paper with Bi2O3 enhances the wound-healing potential when applied to wounds. This impact could be ascribed to Bi2O3's broad antibacterial activity, which reduced infection and accelerated the healing process.

Agar/gelatin hydro-film containing EGF and Aloe vera for effective wound healing

In the current study, we produced a hydro-film dressing for the treatment of chronic wounds. The hydro-film structure was composed of gelatin cross-linked with citric acid, agar and Aloe vera extract (AV); additionally epidermal growth factor (EGF) was loaded to promote wound healing. Due to the excellent hydrogel-forming ability of gelatin, the obtained hydro-film was able to swell 884 ± 36% of its dry weight, which could help controlling wound moisture. To improve gelatin mechanical properties, polymer chains were cross-linked with citric acid and agar, reaching an ultimate tensile strength that was in the highest range of human skin. In addition, it showed a slow degradation profile that resulted in a remaining weight of 28 ± 8% at day 28. Regarding, biological activity, the addition of AV and citric acid provided the ability to reduce human macrophage activation, which could help reverse the permanent inflammatory state of chronic wounds. Moreover, loaded EGF, together with the structural AV of the hydro-film, promoted human keratinocyte and fibroblast migration, respectively. Furthermore, the hydro-films presented excellent fibroblast adhesiveness, so they could be useful as provisional matrices for cell migration. Accordingly, these hydro-films showed suitable physicochemical characteristics and biological activity for chronic wound healing applications.

Polymers and Bioactive Compounds with a Macrophage Modulation Effect for the Rational Design of Hydrogels for Skin Regeneration

The development of biomaterial platforms for dispensing reagents of interest such as antioxidants, growth factors or antibiotics based on functional hydrogels represents a biotechnological solution for many challenges that the biomedicine field is facing. In this context, in situ dosing of therapeutic components for dermatological injuries such as diabetic foot ulcers is a relatively novel strategy to improve the wound healing process. Hydrogels have shown more comfort for the treatment of wounds due to their smooth surface and moisture, as well as their structural affinity with tissues in comparison to hyperbaric oxygen therapy, ultrasound, and electromagnetic therapies, negative pressure wound therapy or skin grafts. Macrophages, one of the most important cells of the innate immune system, have been described as the key not only in relation to the host immune defense, but also in the progress of wound healing. Macrophage dysfunction in chronic wounds of diabetic patients leads to a perpetuating inflammatory environment and impairs tissue repair. Modulating the macrophage phenotype from pro-inflammatory (M1) to anti-inflammatory (M2) could be a strategy for helping to improve chronic wound healing. In this regard, a new paradigm is found in the development of advanced biomaterials capable of inducing in situ macrophage polarization to offer an approach to wound care. Such an approach opens a new direction for the development of multifunctional materials in regenerative medicine. This paper surveys emerging hydrogel materials and bioactive compounds being investigated to induce the immunomodulation of macrophages. We propose four potential functional biomaterials for wound healing applications based on novel biomaterial/bioactive compound combination that are expected to show synergistic beneficial outcomes for the local differentiation of macrophages (M1-M2) as a therapeutic strategy for chronic wound healing improvement.

Antibacterial and Cytocompatible pH-Responsive Peptide Hydrogel

A short peptide, FHHF-11, was designed to change stiffness as a function of pH due to changing degree of protonation of histidines. As pH changes in the physiologically relevant range, G' was measured at 0 Pa (pH 6) and 50,000 Pa (pH 8). This peptide-based hydrogel is antimicrobial and cytocompatible with skin cells (fibroblasts). It was demonstrated that the incorporation of unnatural AzAla tryptophan analog residue improves the antimicrobial properties of the hydrogel. The material developed can have a practical application and be a paradigm shift in the approach to wound treatment, and it will improve healing outcomes for millions of patients each year.

Nafcillin-Loaded Photocrosslinkable Nanocomposite Hydrogels for Biomedical Applications

Skin infections are frequently treated via intravenous or oral administration of antibiotics, which can lead to serious adverse effects and may sometimes contribute to the proliferation of resistant bacterial strains. Skin represents a convenient pathway for delivering therapeutic compounds, ensured by the high number of blood vessels and amount of lymphatic fluids in the cutaneous tissues, which are systematically connected to the rest of the body. This study provides a novel, straightforward method to obtain nafcillin-loaded photocrosslinkable nanocomposite hydrogels and demonstrates their performance as drug carriers and antimicrobial efficacy against Gram-positive bacteria. The novel formulations obtained, based on polyvinylpyrrolidone, tri(ethylene glycol) divinyl ether crosslinker, hydrophilic bentonite nanoclay, and/or two types of photoactive (TiO₂ and ZnO) nanofillers, were characterized using various analytical methods (transmission electron microscopy (TEM), scanning electron microscopy-energy-dispersive X-ray analysis (SEM-EDX), mechanical tests (tension, compression, and shear), ultraviolet-visible spectroscopy (UV-Vis), swelling investigations, and via specific microbiological assays ("agar disc diffusion method" and "time-kill test"). The results reveal that the nanocomposite hydrogel possessed high mechanical resistance, good swelling abilities, and good antimicrobial activity, demonstrating a decrease in the bacteria growth between 3log₁₀ and 2log₁₀ after one hour of direct contact with S. aureus.

Photo-crosslinking hydrogel for wound healing in a pilonidal sinus patient after open surgery

Pilonidal sinus is a chronic infectious disease with large incision and high risk of relapse after surgical management. Therefore, effective intervention strategies are urgently needed to reduce the relapse and shorten the wound healing time. Hydrogels have been widely used in regenerative medicine for its great biocompatibility, however, it remains challenging to integrate the material with wound tissues. Here, we reported a case of pilonidal sinus patient using a novel tissue integration material, Photo-crosslinking hydrogel after open surgery. A 38-year-old man with a pilonidal sinus for ˃5 years underwent open surgery. When the surgery was finished, the wound was injected with hydrogel that was irradiated with a ultraviolet light source until covered and solidified completely. Hydrogel needed to be changed 1-2 times per week. We evaluated the healing time as primary outcome and then followed up for ˃1 year to observe the relapse. The wound healed completely in 46 days after open surgery, which was shorter than that reported in other studies. Meanwhile, no recurrence was detected during follow-up. Photo-crosslinking hydrogel effectively promoted wound healing and has the potential to be easily applied in Pilonidal sinus patients after open surgery.

Delivery of Porphyrins Through Self-Assembling Peptide Hydrogels for Accelerated Healing of Experimental Skin Defects In Vivo

INTRODUCTION

The care and healing of skin defects resulting from different causes has been the object of research to achieve rapid and complete skin regeneration. Hydrogels have been used for their ability to maintain hydration during wound healing, absorb wound exudate, and cover the underlying tissue without adherence while being transparent. In this study, we evaluated the efficacy of a hydrogel (H) with encapsulated porphyrin (H+P) on a rat model of surgically-induced skin defects.

METHODS

Four round 6 mm diameter skin defects were performed under general anesthesia on the dorsal area of 24 three-month-old "Young" and 24 twelve-month-old "Mature" male rats. Each age group was separated into the Control, H, and H+P groups, n=8 each, where no therapy, H, or H+P was respectively applied daily for 20 days. Digital photographs and skin biopsies were taken on the third, seventh, 10th, and 20th postoperative days and evaluated by planimetry, histology, and immunohistochemistry.

RESULTS

Planimetry results demonstrated significantly decreased perimeter, diameter, and area measurements (p<0.005) of group H+P compared to Control and H groups on days 10 and 20 in the young rats, while in the mature rats, the significant differences were evident earlier (perimeter third day p<0.05; diameter and area seventh day p<0.05 and p<0.005, respectively vs. H). Granulation and scar tissue formation were also reduced in the H+P groups although they were not statistically significant.

CONCLUSIONS

The application of H+P on the skin defects benefited the healing process in both young and mature animal groups, as evidenced by the statistically significant findings of planimetry. The beneficial healing process was more pronounced in the mature animals, both in the level of statistical significance as well as regarding time (evident already on the third day of healing), probably due to porphyrin assisting the reduced healing rate, which is observed in organisms of advanced age.

Antibacterial-Based Hydrogel Coatings and Their Application in the Biomedical Field-A Review

Hydrogels exhibit excellent moldability, biodegradability, biocompatibility, and extracellular matrix-like properties, which make them widely used in biomedical fields. Because of their unique three-dimensional crosslinked hydrophilic networks, hydrogels can encapsulate various materials, such as small molecules, polymers, and particles; this has become a hot research topic in the antibacterial field. The surface modification of biomaterials by using antibacterial hydrogels as coatings contributes to the biomaterial activity and offers wide prospects for development. A variety of surface chemical strategies have been developed to bind hydrogels to the substrate surface stably. We first introduce the preparation method for antibacterial coatings in this review, which includes surface-initiated graft crosslinking polymerization, anchoring the hydrogel coating to the substrate surface, and the LbL self-assembly technique to coat crosslinked hydrogels. Then, we summarize the applications of hydrogel coating in the biomedical antibacterial field. Hydrogel itself has certain antibacterial properties, but the antibacterial effect is not sufficient. In recent research, in order to optimize its antibacterial performance, the following three antibacterial strategies are mainly adopted: bacterial repellent and inhibition, contact surface killing of bacteria, and release of antibacterial agents. We systematically introduce the antibacterial mechanism of each strategy. The review aims to provide reference for the further development and application of hydrogel coatings.

The Development of a Polysaccharide-Based Hydrogel Encapsulating Tobramycin-Loaded Gelatine Microspheres as an Antibacterial System

Bacterial infection contributes to the bioburden of wounds, which is an essential factor in determining whether a wound can heal. Wound dressings with antibacterial properties that can promote wound-healing are highly desired for the treatment of chronic wound infections. Herein, we fabricated a simple polysaccharide-based hydrogel dressing encapsulating tobramycin-loaded gelatine microspheres with good antibacterial activity and biocompatibility. We first synthesised long-chain quaternary ammonium salts (QAS) by the reaction of tertiary amines with epichlorohydrin. The amino groups of carboxymethyl chitosan were then conjugated with QAS through the ring-opening reaction and QAS-modified chitosan (CMCS) was obtained. The antibacterial analysis showed that both QAS and CMCS could kill E. coli and S. aureus at relatively low concentrations. QAS with 16 carbon atoms has a MIC of 16 μg/mL for E. coli and 2 μg/mL for S. aureus. A series of formulations of tobramycin-loaded gelatine microspheres (TOB-G) were generated and the best formulation was selected by comparing the characters of the microspheres. The microsphere fabricated by 0.1 mL GTA was selected as the optimal candidate. We then used CMCS, TOB-G, and sodium alginate (SA) to prepare physically crosslinking hydrogels using CaCl2 and investigated the mechanical properties, antibacterial activity, and biocompatibility of the hydrogels. In summary, the hydrogel dressing we produced can be used as an ideal alternative for the management of bacteria-infected wounds.

Applications of MXene and its modified materials in skin wound repair

The rapid healing and repair of skin wounds has been receiving much clinical attention. Covering the wound with wound dressing to promote wound healing is currently the main treatment for skin wound repair. However, the performance of wound dressing prepared by a single material is limited and cannot meet the requirements of complex conditions for wound healing. MXene is a new two-dimensional material with electrical conductivity, antibacterial and photothermal properties and other physical and biological properties, which has a wide range of applications in the field of biomedicine. Based on the pathophysiological process of wound healing and the properties of ideal wound dressing, this review will introduce the preparation and modification methods of MXene, systematically summarize and review the application status and mechanism of MXene in skin wound healing, and provide guidance for subsequent researchers to further apply MXene in the design of skin wound dressing.

Design Considerations, Formulation Approaches, and Strategic Advances of Hydrogel Dressings for Chronic Wound Management

Wound healing is a complex and dynamic physiological process consisting of a series of cellular and molecular events that initiate immediately after a tissue lesion, to reconstruct the skin layer. It is indubitable that patients with chronic wounds, severely infected wounds, or any metabolic disorder of the wound microenvironment always endure severe pain and discomfort that affect their quality of life. It is essential to treat chronic wounds for conserving the physical as well as mental well-being of affected patients and for convalescing to improve their quality of life. For supporting and augmenting the healing process, the selection of pertinent wound dressing is essential. A substantial reduction in healing duration, disability, associated cost, and risk of recurrent infections can be achieved via engineering wound dressings. Hydrogels play a leading role in the path of engineering ideal wound dressings. Hydrogels, comprising water to a large extent, providing a moist environment, being comfortable to patients, and having biocompatible and biodegradable properties, have found their success as suitable wound dressings in the market. The exploitation of hydrogels is increasing perpetually after substantiation of their broader therapeutic actions owing to their resemblance to dermal tissues, their capability to stimulate partial skin regeneration, and their ability to incorporate therapeutic moieties promoting wound healing. This review entails properties of hydrogel supporting wound healing, types of hydrogels, cross-linking mechanisms, design considerations, and formulation strategies of hydrogel engineering. Various categories of hydrogel wound dressing fabricated recently are discussed based on their gel network composition, degradability, and physical and chemical cross-linking mechanisms, which provide an outlook regarding the importance of tailoring the physicochemical properties of hydrogels. The examples of marketed hydrogel wound dressings are also incorporated along with the future perspectives and challenges associated with them.

Aptamers as Novel Binding Molecules on an Antimicrobial Peptide-Armored Composite Hydrogel Wound Dressing for Specific Removal and Efficient Eradication of Pseudomonas aeruginosa

Here we present for the first time a potential wound dressing material implementing aptamers as binding entities to remove pathogenic cells from newly contaminated surfaces of wound matrix-mimicking collagen gels. The model pathogen in this study was the Gram-negative opportunistic bacterium Pseudomonas aeruginosa, which represents a considerable health threat in hospital environments as a cause of severe infections of burn or post-surgery wounds. A two-layered hydrogel composite material was constructed based on an established eight-membered focused anti-P. aeruginosa polyclonal aptamer library, which was chemically crosslinked to the material surface to form a trapping zone for efficient binding of the pathogen. A drug-loaded zone of the composite released the C14R antimicrobial peptide to deliver it directly to the bound pathogenic cells. We demonstrate that this material combining aptamer-mediated affinity and peptide-dependent pathogen eradication can quantitatively remove bacterial cells from the "wound" surface, and we show that the surface-trapped bacteria are completely killed. The drug delivery function of the composite thus represents an extra safeguarding property and thus probably one of the most important additional advances of a next-generation or smart wound dressing ensuring the complete removal and/or eradication of the pathogen of a freshly infected wound.

Recent Advances in Nano-Drug Delivery Systems for the Treatment of Diabetic Wound Healing

Diabetes mellitus (DM) induced wound healing impairment remains a serious health problem and burden on the clinical obligation for high amputation rates. Based on the features of wound microenvironment, biomaterials loading specific drugs can benefit diabetic wound treatment. Drug delivery systems (DDSs) can carry diverse functional substances to the wound site. Nano-drug delivery systems (NDDSs), benefiting from their features related to nano size, overcome limitations of conventional DDSs application and are considered as a developing process in the wound treatment field. Recently, a number of finely designed nanocarriers efficiently loading various substances (bioactive and non-bioactive factors) have emerged to circumvent constraints faced by traditional DDSs. This review describes various recent advances of nano-drug delivery systems involved in mitigating diabetes mellitus-based non-healing wounds.

Hyaluronic acid-g-lipoic acid granular gel for promoting diabetic wound healing

Diabetic patients are prone to developing chronic inflammation after trauma and have persistent nonhealing wounds. Reactive oxygen species (ROS) and recurrent bacterial infections at the site of long-term wounds also further delay skin wound healing and tissue regeneration. In this study, a granular gel (which exhibits ROS scavenging and antibacterial properties) is fabricated based on hyaluronic acid-g-lipoic acid (HA-LA). Briefly, HA-LA is synthesized to fabricate HA-LA microgels, which are further assembled by Ag⁺ via its coordination effect with disulfide in dithiolane to form a granular gel. The extrudable bulk granular gel possesses a shear-thinning feature and is immediately restored to a solid state after extrusion, and this can be easily applied to the whole wound area. Therefore, the grafted LA not only allows for the construction of the granular gel but also removes excess ROS from the microenvironment. Additionally, the presence of Ag⁺ realizes the assembly of microgels and has antibacterial effects. In vivo experiments show that the HA-LA granular gel eliminates excessive ROS at the wound site and up-regulates the secretion of reparative growth factors, thus, accelerating common and diabetic wound healing significantly. Therefore, the ROS-scavenging granular gel that can be applied to the wound surface with chronic inflammation demonstrates strong clinical utility.

Local Drug Delivery Strategies towards Wound Healing

A particular biological process known as wound healing is connected to the overall phenomena of growth and tissue regeneration. Several cellular and matrix elements work together to restore the integrity of injured tissue. The goal of the present review paper focused on the physiology of wound healing, medications used to treat wound healing, and local drug delivery systems for possible skin wound therapy. The capacity of the skin to heal a wound is the result of a highly intricate process that involves several different processes, such as vascular response, blood coagulation, fibrin network creation, re-epithelialisation, collagen maturation, and connective tissue remodelling. Wound healing may be controlled with topical antiseptics, topical antibiotics, herbal remedies, and cellular initiators. In order to effectively eradicate infections and shorten the healing process, contemporary antimicrobial treatments that include antibiotics or antiseptics must be investigated. A variety of delivery systems were described, including innovative delivery systems, hydrogels, microspheres, gold and silver nanoparticles, vesicles, emulsifying systems, nanofibres, artificial dressings, three-dimensional printed skin replacements, dendrimers and carbon nanotubes. It may be inferred that enhanced local delivery methods might be used to provide wound healing agents for faster healing of skin wounds.

Current state of knowledge on intelligent-response biological and other macromolecular hydrogels in biomedical engineering: A review

Because intelligent hydrogels have good biocompatibility, a rapid response, and good degradability as well as a stimulus response mode that is rich, hydrophilic, and similar to the softness and elasticity of living tissue, they have received widespread attention and are widely used in biomedical engineering. In this article, we conduct a systematic review of the use of smart hydrogels in biomedical engineering. First, we introduce the properties and applications of hydrogels and compare the similarities and differences between traditional hydrogels and smart hydrogels. Secondly, we summarize the intelligent hydrogel types, the mechanisms of action used by different hydrogels, and the materials for preparing different types of hydrogels, such as the materials for the preparation of temperature-responsive hydrogels, which mainly include gelatin, carrageenan, agarose, amylose, etc.; summarize the morphologies of different hydrogels, such as films, fibers and microspheres; and summarize the application of smart hydrogels in biomedical engineering, such as for the delivery of proteins, antibiotics, deoxyribonucleic acid, etc. Finally, we summarize the shortcomings of current research and present future prospects for smart hydrogels. The purpose of this paper is to provide researchers engaged in related fields with a systematic review of the application of intelligent hydrogels in biomedical engineering. We hope that they will get some inspiration from this work to provide new directions for the development of related fields.

Advances in the Physico-Chemical, Antimicrobial and Angiogenic Properties of Graphene-Oxide/Cellulose Nanocomposites for Wound Healing

Graphene oxide (GO) and its reduced form (rGO) have recently attracted a fascinating interest due to their physico-chemical properties, which have opened up new and interesting opportunities in a wide range of biomedical applications, such as wound healing. It is worth noting that GO and rGO may offer a convenient access to its ready dispersion within various polymeric matrices (such as cellulose and its derivative forms), owing to their large surface area, based on a carbon skeleton with many functional groups (i.e., hydroxyl, carboxyl, epoxy bridge, and carbonyl moieties). This results in new synergic properties due to the presence of both components (GO or rGO and polymers), acting at different length-scales. Furthermore, they have shown efficient antimicrobial and angiogenic properties, mostly related to the intracellular formation of reactive oxygen species (ROS), which are advantageous in wound care management. For this reason, GO or rGO integration in cellulose-based matrixes have allowed for designing highly advanced multifunctional hybrid nanocomposites with tailored properties. The current review aims to discuss a potential relationship between structural and physico-chemical properties (i.e., size, edge density, surface chemistry, hydrophilicity) of the nanocomposites with antimicrobials and angiogenic mechanisms that synergically influence the wound healing phenomenon, by paying particular attention to recent findings of GO or rGO/cellulose nanocomposites. Accordingly, after providing a general overview of cellulose and its derivatives, the production methods used for GO and rGO synthesis, the mechanisms that guide antimicrobial and angiogenic processes of tissue repair, as well as the most recent and remarkable outcomes on GO/cellulose scaffolds in wound healing applications, will be presented.

Xenogeneic mesenchymal stem cell biocurative improves skin wounds healing in diabetic mice by increasing mast cells and the regenerative profile

Introduction

Diabetes mellitus (DM) is a chronic disease and a major cause of mortality and morbidity worldwide. The hyperglycemia caused by DM induces micro and macrovascular complications that lead, among other consequences, to chronic wounds and amputations. Cell therapy and tissue engineering constitute recent therapeutic alternatives to improve wound healing in diabetic patients. The current study aimed to analyze the effectiveness of biocuratives containing human mesenchymal stem cells (MSCs) associated with a hydrogel matrix in the wound healing process and related inflammatory cell profile in diabetic mice.

Methods

Biocuratives containing MSCs were constructed by 3D bioprinting, and applied to skin wounds on the back of streptozotocin (STZ)-induced type 1 diabetic (T1D) mice. The healing process, after the application of biocuratives with or without MSCs was histologically analyzed. In parallel, genes related to growth factors, mast cells (MC), M1 and M2 macrophage profiles were evaluated by RT-PCR. Macrophages were characterized by flow cytometry, and MC by toluidine blue staining and flow cytometry.

Results

Mice with T1D exhibited fewer skin MC and delayed wound healing when compared to the non-diabetic group. Treatment with the biocuratives containing MSCs accelerated wound healing and improved skin collagen deposition in diabetic mice. Increased TGF-β gene expression and M2 macrophage-related markers were also detected in skin of diabetic mice that received MSCs-containing biocuratives. Finally, MSCs upregulated IL-33 gene expression and augmented the number of MC in the skin of diabetic mice.

Conclusion

These results reveal the therapeutic potential of biocuratives containing MSCs in the healing of skin wounds in diabetic mice, providing a scientific base for future treatments in diabetic patients.

A fucoidan-gelatin wound dressing accelerates wound healing by enhancing antibacterial and anti-inflammatory activities

Microbial infections and the slow regression of inflammation are major impediments to wound healing. Herein, a tilapia fish skin gelatin-fucose gum-tannic acid (Gel&Fuc-TA) hydrogel wound dressing (Gel&Fuc-TA) was designed to promote wound healing by mixing and reacting tannic acid (TA) with tilapia fish skin gelatin (Gel) and fucoidan (Fuc). Gel&Fuc-TA hydrogel has a good network structure as well as swelling and release properties, and shows excellent antibacterial, antioxidant, cell compatibility, and hemostatic properties. Gel&Fuc-TA hydrogel can promote the expression of vascular endothelial growth factor (VEGF), platelet endothelial cell adhesion molecule-1 (CD-31), and alpha-smooth muscle actin (α-SMA), enhance collagen deposition, and accelerate wound repair. Gel&Fuc-TA hydrogel can change the wound microbiome, reduce wound microbiome colonization, and decrease the expression of microbiome-related proinflammatory factors, such as lipopolysaccharide (LPS), Toll-like receptor 2 (TLR2), and Toll-like receptor 4 (TLR4). Gel&Fuc-TA hydrogel effectively regulates the conversion of wound macrophages to the M2 (anti-inflammatory phenotype) phenotype, decreases the expression of interleukin-6 (IL-6), interleukin-1β (IL-1β) and tumor necrosis factor-alpha (TNF-α), and increases the expression of arginase-1 (Arg-1), interleukin-10 (IL-10) and transforming growth factor-beta (TGF-β), thereby reducing the inflammatory response. In summary, Gel&Fuc-TA hydrogel prepared using a rational green cross-linking reaction can effectively accelerate wound healing.

Current Progress and Outlook of Nano-Based Hydrogel Dressings for Wound Healing

Wound dressing is an important tool for wound management. Designing wound dressings by combining various novel materials and drugs to optimize the peri-wound environment and promote wound healing is a novel concept. Hydrogels feature good ductility, high water content, and favorable oxygen transport, which makes them become some of the most promising materials for wound dressings. In addition, nanomaterials exhibit superior biodegradability, biocompatibility, and colloidal stability in wound healing and can play a role in promoting healing through their nanoscale properties or as carriers of other drugs. By combining the advantages of both technologies, several outstanding and efficient wound dressings have been developed. In this paper, we classify nano-based hydrogel dressings into four categories: hydrogel dressings loaded with a nanoantibacterial drug; hydrogel dressings loaded with oxygen-delivering nanomedicines; hydrogel dressings loaded with nanonucleic acid drugs; and hydrogel dressings loaded with other nanodelivered drugs. The design ideas, advantages, and challenges of these nano-based hydrogel wound dressings are reviewed and analyzed. Finally, we envisaged possible future directions for wound dressings in the context of relevant scientific and technological advances, which we hope will inform further research in wound management.

Sericin-Based Poly(Vinyl) Alcohol Relieves Plaque and Epidermal Lesions in Psoriasis; a Chance for Dressing Development in a Specific Area

The noncontagious immune-mediated skin disease known as psoriasis is regarded as a chronic skin condition with a 0.09-11.4% global prevalence. The main obstacle to the eradication of the disease continues to be insufficient treatment options. Sericin, a natural biopolymer from Bombyx mori cocoons, can improve skin conditions via its immunomodulatory effect. Many external therapeutic methods are currently used to treat psoriasis, but sericin-based hydrogel is not yet used to treat plaques of eczema. Through the use of an imiquimod rat model, this study sought to identify the physical and chemical characteristics of a silk sericin-based poly(vinyl) alcohol (SS/PVA) hydrogel and assess both its therapeutic and toxic effects on psoriasis. The cytokines, chemokines, and genes involved in the pathogenesis of psoriasis were investigated, focusing on the immuno-pathological relationships. We discovered that the SS/PVA had a stable fabrication and proper release. Additionally, the anti-inflammatory, antioxidant, and anti-apoptotic properties of SS/PVA reduced the severity of psoriasis in both gross and microscopic skin lesions. This was demonstrated by a decrease in the epidermal histopathology score, upregulation of nuclear factor erythroid 2-related factor 2 and interleukin (IL)-10, and a decrease in the expression of tumor necrosis factor (TNF)-α and IL-20. Moreover, the genes S100a7a and S100a14 were downregulated. Additionally, in rats given the SS/PVA treatment, blood urea nitrogen, creatinine, and serum glutamic oxaloacetic transaminase levels were within normal limits. Our findings indicate that SS/PVA is safe and may be potentiated to treat psoriasis in a variety of forms and locations of plaque because of its physical, chemical, and biological characteristics.

Recent advances in responsive hydrogels for diabetic wound healing

Poor wound healing after diabetes mellitus remains a challenging problem, and its pathophysiological mechanisms have not yet been fully elucidated. Persistent bleeding, disturbed regulation of inflammation, blocked cell proliferation, susceptible infection and impaired tissue remodeling are the main features of diabetic wound healing. Conventional wound dressings, including gauze, films and bandages, have a limited function. They generally act as physical barriers and absorbers of exudates, which fail to meet the requirements of the whol diabetic wound healing process. Wounds in diabetic patients typically heal slowly and are susceptible to infection due to hyperglycemia within the wound bed. Once bacterial cells develop into biofilms, diabetic wounds will exhibit robust drug resistance. Recently, the application of stimuli-responsive hydrogels, also known as "smart hydrogels", for diabetic wound healing has attracted particular attention. The basic feature of this system is its capacities to change mechanical properties, swelling ability, hydrophilicity, permeability of biologically active molecules, etc., in response to various stimuli, including temperature, potential of hydrogen (pH), protease and other biological factors. Smart hydrogels can improve therapeutic efficacy and limit total toxicity according to the characteristics of diabetic wounds. In this review, we summarized the mechanism and application of stimuli-responsive hydrogels for diabetic wound healing. It is hoped that this work will provide some inspiration and suggestions for research in this field.

Design strategies for adhesive hydrogels with natural antibacterial agents as wound dressings: Status and trends

The wound healing process is usually susceptible to different bacterial infections due to the complex physiological environment, which significantly impairs wound healing. The topical application of antibiotics is not desirable for wound healing because the excessive use of antibiotics might cause bacteria to develop resistance and even the production of super bacteria, posing significant harm to human well-being. Wound dressings based on adhesive, biocompatible, and multi-functional hydrogels with natural antibacterial agents have been widely recognized as effective wound treatments. Hydrogels, which are three-dimensional (3D) polymer networks cross-linked through physical interactions or covalent bonds, are promising for topical antibacterial applications because of their excellent adhesion, antibacterial properties, and biocompatibility. To further improve the healing performance of hydrogels, various modification methods have been developed with superior biocompatibility, antibacterial activity, mechanical properties, and wound repair capabilities. This review summarizes hundreds of typical studies on various ingredients, preparation methods, antibacterial mechanisms, and internal antibacterial factors to understand adhesive hydrogels with natural antibacterial agents for wound dressings. Additionally, we provide prospects for adhesive and antibacterial hydrogels in biomedical applications and clinical research.

Combination therapy of hydrogel and stem cells for diabetic wound healing

Diabetic wounds (DWs) are a common complication of diabetes mellitus; DWs have a low cure rate and likely recurrence, thus affecting the quality of patients’ lives. As traditional therapy cannot effectively improve DW closure, DW has become a severe clinical medical problem worldwide. Unlike routine wound healing, DW is difficult to heal because of its chronically arrested inflammatory phase. Although mesenchymal stem cells and their secreted cytokines can alleviate oxidative stress and stimulate angiogenesis in wounds, thereby promoting wound healing, the biological activity of mesenchymal stem cells is compromised by direct injection, which hinders their therapeutic effect. Hydro-gels form a three-dimensional network that mimics the extracellular matrix, which can provide shelter for stem cells in the inflammatory microenvironment with reactive oxygen species in DW, and maintains the survival and viability of stem cells. This review summarizes the mechanisms and applications of stem cells and hydrogels in treating DW; additionally, it focuses on the different applications of therapy combining hydrogel and stem cells for DW treatment.