Mechanically strong and on-demand dissoluble chitosan hydrogels for wound dressing applications

Self-assembling chitosan based injectable and expandable sponge with antimicrobial property for hemostasis and wound healing

Chitosan and chitosan derivative are widely used in hemostasis, antibiosis and wound repair for its good biocompatibility and unique effect. However, the preparation of chitosan based hemostatic materials or wound dressings generally involves chemical crosslinking agent introduction, acid residue or complicated preparation process, which limits its clinical application. In this study, an injectable and expandable chitosan sponge was constructed by chitosan (CS) and quaternized chitosan (QCS) self-assembly without acid retention and chemical crosslinker introduction. In the neutral condition, the hydrogen bond of CS molecules can act as the driving force to form cross-linking network, and the QCS was introduced to regulate the hydrogen bond of CS to avoid the excessive aggregation. The porous QCS/CS sponge was obtained by freeze-drying of the self-assembly QCS/CS hydrogel. The sponge exhibited high expansibility, injectability and water/blood triggered shape memory property. Due to the introduction of QCS, the sponge showed good antibacterial properties, which can protect the wound from bacterial invasion. The convenient and green preparation method of injectable and expandable QCS/CS sponge is a potential method for the treatment of hemostasis and wound healing.

A slime-inspired phycocyanin/κ-carrageenan-based hydrogel bandage with ultra-stretchability, self-healing, antioxidative, and antibacterial activity for wound healing

Hydrogels have attracted extensive attention as wound dressing owing to their excellent multifunctionality, flexibility, and biocompatibility. Due to the frequent movement and stretching of skin as well as complex surface of wound, traditional wound dressings have difficulty to adapt to motion and irregular wounds. Furthermore, excessive reactive oxygen species (ROS) and bacterial infection can induce delayed wound healing. To this end, we developed a set of versatile phycocyanin-based dual network hydrogels (PPC hydrogels) with polyvinyl alcohol (PVA) and κ-carrageenan (CRG) as substrate via forming of borate ester bonds, hydrogen bonds, and electrostatic interaction. The PPC hydrogels not only possessed adaptivity, ultra-stretchability (7036.12 %), efficient self-healing and injectability, but also possessed antioxidative and antibacterial capacities conferred by C-phycocyanin (PC) and rhein. Moreover, the hydrogels also exhibited excellent hemostatic ability and high biocompatibility. More remarkably, the PPC-I hydrogel could accelerate wound healing by effect of anti-inflammation (downregulating TNF-α and IL-6) and promoting collagen deposition and angiogenesis (upregulating CD31), which may be utilized as hydrogel bandages and applied to motion and irregular wounds, thereby promising the application prospect of the hydrogels as wound dressing.

Functional Hydrogels for Aqueous Zinc-Based Batteries: Progress and Perspectives

Aqueous zinc batteries (AZBs) hold great potential for green grid-scale energy storage due to their affordability, resource abundance, safety, and environmental friendliness. However, their practical deployment is hindered by challenges related to the electrode, electrolyte, and interface. Functional hydrogels offer a promising solution to address such challenges owing to their broad electrochemical window, tunable structures, and pressure-responsive mechanical properties. In this review, the key properties that functional hydrogels must possess for advancing AZBs, including mechanical strength, ionic conductivity, swelling behavior, and degradability, from a perspective of the full life cycle of hydrogels in AZBs are summarized. Current modification strategies aimed at enhancing these properties and improving AZB performance are also explored. The challenges and design considerations for integrating functional hydrogels with electrodes and interface are discussed. In the end, the limitations and future directions for hydrogels to bridge the gap between academia and industries for the successful deployment of AZBs are discussed.

Chitosan-Electrospun Fibers Encapsulating Norfloxacin: The Impact on the Biochemical, Oxidative and Immunological Profile in a Rats Burn Model

This study investigates the impact of chitosan-based nanofibers on burn wound healing in a rat model. Two formulations of chitosan nanofibers were prepared through electrospinning. The formulations were then incorporated with different amounts of norfloxacin and underwent surface modifications with 2-formylphenylboronic acid. The burn model was applied to Wistar male rats by the contact method, using a heated steel rod attached to a thermocouple. The effectiveness of the nanofibers was tested against a negative control group and a standard commercial dressing (Atrauman Ag) on the described model and evaluated by wound diameter, histological analysis and biochemical profiling of systemic inflammatory markers. The results showed that chitosan-based dressings significantly accelerated burn healing compared to the control treatments. The high-concentration norfloxacin-infused chitosan coated with 2-formylphenylboronic acid' groups exhibited significant improvements in wound closure and reduced inflammation compared to the other groups; antioxidant enzymes SOD and GPx expression was significantly higher, p < 0.05, whereas pro-oxidative markers such as cortisol were lower (p < 0.05). Macroscopically, the wound area itself was significantly diminished in the chitosan-treated groups (p < 0.05). Furthermore, a histological evaluation indicated enhanced epithelialization and granulation tissue formation within the experiment time frame, while the biochemical panel revealed lower levels of inflammatory cytokines and lower leukocyte counts in the treated groups. These findings highlight the potential of the studied chitosan nanofibers as novel nanosystems for next-generation wound therapies, as well as the clinical utility of the novel chitosan fibers obtained by electrospinning technique.

Antioxidant hydrogel from poly(aspartic acid) and carboxymethylcellulose with quercetin loading as burn wound dressing

Susceptibility to infection and excessive accumulation of reactive oxygen species (ROS) are the greatest obstacles for burn wound healing. In this research, the 5-aminosalicylic acid (ASA) grafted poly(aspartic hydrazide) (PASH) was synthesized by successive ploysuccinimide (PSI) ring opening reaction and reacted with oxidized carboxymethyl cellulose (DCMC) to fabricate biodegradable hydrogel through Schiff-base cross-linking. Moreover, the hydrogel was loaded with quercetin (QT) to enhance its anti-inflammatory performance. The ASA moiety endowed the hydrogel with the free radical scavenging ability and mussel inspired tissue adhesion to maintain the healing bioenvironment of the wound. The loading of QT gave the hydrogel more phenolic hydroxy group and further enhanced the antioxidant capacity of the hydrogel. The in vitro experiment revealed the grafted ASA moiety and the loaded QT greatly enhanced the ROS elimination property and antibacterial property. Moreover, the QT loaded hydrogel accelerated the burn wound repairing rate in the in vivo mice model. Based on above result, the PASH/DCMC could act as a new platform for QT loading to promote the burn wound repairing.

On-Demand Removable Chitosan Based Self-Healing and Antibacterial Hydrogel for Delivery of Tetracycline and Curcumin As Potential Wound Dressing Material

Wound care is a flourishing branch of healthcare wherein a great amount of research is devoted to develop competent wound dressings. Safe, cost-effective, and biocompatible dressings aid in wound healing without inflicting external trauma and subsequent scar formation. Toward this, we have attempted to develop robust wound dressing material with self-healing and antibacterial properties. We have cross-linked chitosan with 4-formyl phenylboronic acid (4-FPBA) and in situ generated dehydroascorbic acid (DHA) utilizing the dynamic imine and boronate ester linkages. Displaying a channeled microstructure in the SEM micrographs, the hydrogel exhibits a massive water uptake capacity of ∼900% at acidic pH. The hydrogel could completely self-heal within 3 min, and the results are further supported by rheological analysis. By virtue of positive surface charge, it shows a promising tissue adhesive property. Moreover, it affords clean and compliant removal from the wound surface via dissolution induced by dopamine to potentially reduce secondary scarring from peeling of wound dressings. The dressing could significantly act against skin infections caused by S. aureus bacteria with enhanced antimicrobial efficiency via loading of antibiotic drug, tetracycline hydrochloride. A sustained release of tetracycline and Curcumin was observed, which demonstrated the release ability for hydrophilic and hydrophobic bioactive agents. In-vitro studies revealed 93% cell viability with a hemolytic ratio as low as 2.5%, thereby presenting a good self-healing and biocompatible material for wound healing.

Incorporation of montmorillonite into microfluidics-generated chitosan microfibers enhances neuron-like PC12 cells for application in neural tissue engineering

The complexity in structure and function of the nervous system, as well as its slow rate of regeneration, makes it more difficult to treat it compared to other tissues. Neural tissue engineering aims to create an appropriate environment for nerve cell proliferation and differentiation. Fibrous scaffolds with suitable morphology and topography and better mimicry of the extracellular matrix have been promising for the alignment and migration of neural cells. On this premise, to improve the properties of the scaffold, we combined montmorillonite (MMT) with chitosan (CS) polymer and created microfibers with variable diameters and varied concentrations of MMT using microfluidic technology and tested its suitability for the rat pheochromocytoma cell line (PC12). According to the findings, CS/MMT 0.1 % compared to CS/MMT 0 % microfibers showed a 201 MPa increase in Young's modulus, a 68 mS/m increase in conductivity, and a 1.4-fold increase in output voltage. Analysis of cell mitochondrial activity verified the non-toxicity, resulting in good cell morphology with orientation along the microfiber. Overall, the results of this project showed that with a low concentration of MMT, the properties of microfibers can be significantly improved and a suitable scaffold can be designed for neural tissue engineering.

Recent development and applications of electrodeposition biocoatings on medical titanium for bone repair

Bioactive coatings play a crucial role in enhancing the osseointegration of titanium implants for bone repair. Electrodeposition offers a versatile and efficient technique to deposit uniform coatings onto titanium surfaces, endowing implants with antibacterial properties, controlled drug release, enhanced osteoblast adhesion, and even smart responsiveness. This review summarizes the recent advancements in bioactive coatings for titanium implants used in bone repair, focusing on various electrodeposition strategies based on material-structure synergy. Firstly, it outlines different titanium implant materials and bioactive coating materials suitable for bone repair. Then, it introduces various electrodeposition methods, including electrophoretic deposition, anodization, micro-arc oxidation, electrochemical etching, electrochemical polymerization, and electrochemical deposition, discussing their applications in antibacterial, osteogenic, drug delivery, and smart responsiveness. Finally, it discusses the challenges encountered in the electrodeposition of coatings for titanium implants in bone repair and potential solutions.

Development of biomaterial composite hydrogel as a passive sampler with potential application in wastewater-based surveillance

Nowadays, the need to track fast-spreading infectious diseases has raised due to the recent COVID-19 disease pandemic. As a response, Wastewater-based Surveillance (WBS) has emerged as an early detection and disease tracking method for large populations that enables a comprehensive overview of public health allowing for a faster response from public health sector to prevent large outbreaks. The process to achieve WBS requires a highly intensive sampling strategy with either expensive equipment or trained personnel to continuously sample. The sampling problem can be addressed by passive sampler development. Chitosan-based hydrogels are recognized for their capability to sample and remove various contaminants from wastewater, including metals, dyes, pharmaceuticals, among others. However, chitosan-based hydrogels unique characteristics, can be exploited to develop passive samplers of genetic material that can be a very valuable tool for WBS. This study aimed to develop a novel chitosan hydrogel formulation with enhanced characteristics suitable for use as a passive sampler of genetic material and its application to detect disease-causing pathogens present in wastewater. The study evaluates the effect of the concentration of different components on the formulation of a Chitosan composite hydrogel (Chitosan, Glutaraldehyde, Microcrystalline cellulose (MCC), and Polyethylene glycol (PEG)) on the hydrogel properties using a Box Hunter & Hunter experimental matrix. Hydrogels' weight, thickness, swelling ratio, microscopic morphology (SEM), FTIR assay, and zeta potential were characterized. The resulting hydrogel formulations were shown to be highly porous, positively charged (Zeta potential up to 35.80 ± 1.44 mV at pH 3) and with high water swelling capacity (up to 703.89 ± 15.00 %). Based on the results, a formulation from experimental design was selected and then evaluated its capacity to adsorb genetic material from a control spiked water with Influenza A virus synthetic vector. The adsorption capacity of the selected formulation was 4157.04 ± 64.74 Gene Copies/mL of Influenza A virus synthetic vector. The developed hydrogel showed potential to be used as passive sampler for pathogen detection in wastewater. However, deeper research can be conducted to improve adsorption, desorption and extraction techniques of genetic material from chitosan-hydrogel matrices.

Novel Functional Dressing Materials for Intraoral Wound Care

Intraoral wounds represent a particularly challenging category of mucosal and hard tissue injuries, characterized by the unique structures, complex environment, and distinctive healing processes within the oral cavity. They have a common occurrence yet frequently inflict significant inconvenience and pain on patients, causing a serious decline in the quality of life. A variety of novel functional dressings specifically designed for the moist and dynamic oral environment have been developed and realized accelerated and improved wound healing. Thoroughly analyzing and summarizing these materials is of paramount importance in enhancing the understanding and proficiently managing intraoral wounds. In this review, the particular processes and unique characteristics of intraoral wound healing are firstly described. Up-to-date knowledge of various forms, properties, and applications of existing products are then intensively discussed, which are categorized into animal products, plant extracts, natural polymers, and synthetic products. To conclude, this review presents a comprehensive framework of currently available functional intraoral wound dressings, with an aim to provoke inspiration of future studies to design more convenient and versatile materials.

Enhancing the porosity of chitosan sponges with CBD by adding antimicrobial violacein

Given the growing interest in non-toxic materials with good anti-inflammatory and antimicrobial mechanical properties, this work focuses on preparing chitosan sponges with violacein and cannabis oil crosslinked with dialdehyde chitosan. The sponge was tested for its physicochemical and biological properties, presenting a high swelling rate, good thermal stability, and satisfactory mechanical properties. The obtained sponge's water vapor transmission rate was 2101 g/m2/day and is within the recommended values for ideal wound dressings. Notably, adding violacein favorably affected the material's porosity, which is essential for dressing materials. In addition, studies have shown that the designed material interacts with human serum albumin and exhibits good antioxidant and anti-inflammatory properties. The antibacterial properties of the prepared biomaterial were assessed using the Microtox test against A. fisherii (Gram-negative bacterium) and S. aureus (Gram-positive bacterium). The investigated material provides potential therapeutic benefits due to the synergistic action of chitosan, violacein, and cannabis oil so that it could be used as a dressing material. The natural origin of the substances could provide an attractive and sustainable alternative to traditional commercially available dressings.

Emerging trends and challenges in polysaccharide derived materials for wound care applications: A review

Polysaccharides are favourable and promising biopolymers for wound care applications due to their abundant natural availability, low cost and excellent biocompatibility. They possess different functional groups, such as carboxylic, hydroxyl and amino, and can easily be modified to obtain the desirable properties and various forms. This review systematically analyses the recent progress in polysaccharides derived materials for wound care applications, emphasizing the most commonly used cellulose, chitosan, alginate, starch, dextran and hyaluronic acid derived materials. The distinctive attributes of each polysaccharide derived wound care material are discussed in detail, along with their different forms, i.e., films, membranes, sponges, nanoemulsions, nanofibers, scaffolds, nanocomposites and hydrogels. The processing methods to develop polysaccharides derived wound care materials are also summarized. In the end, challenges related to polysaccharides derived materials in wound care management are listed, and suggestions are given to expand their utilization in the future to compete with conventional wound healing materials.

Proanthocyanidins-based tandem dynamic covalent cross-linking hydrogel for diabetic wound healing

Wound healing in diabetic patients presents significant challenges in clinical wound care due to high oxidative stress, excessive inflammation, and a microenvironment prone to infection. In this study, we successfully developed a multifunctional tandem dynamic covalently cross-linked hydrogel dressing aimed at diabetic wound healing. This hydrogel was constructed using cyanoacetic acid functionalized dextran (Dex-CA), 2-formylbenzoylboric acid (2-FPBA) and natural oligomeric proanthocyanidins (OPC), catalyzed by histidine. The resulting Dex-CA/OPC/2-FPBA (DPOPC) hydrogel can be dissolved triggered by cysteine, thereby achieving "controllable and non-irritating" dressing change. Furthermore, the incorporation of OPC as a hydrogel building block endowed the hydrogel with antioxidant and anti-inflammatory properties. The cross-linked network of the DPOPC hydrogel circumvents the burst release of OPC, enhancing its biosafety. In vivo studies demonstrated that the DPOPC hydrogel significantly accelerated the wound healing process in diabetic mice compared to a commercial hydrogel, achieving an impressive wound closure rate of 98 % by day 14. The DPOPC hydrogel effectively balanced the disrupted inflammatory state during the healing process. This dynamic hydrogel based on natural polyphenols is expected to be an ideal candidate for dressings intended for chronic wounds.

Multifunctional antibacterial hydrogels for chronic wound management

Chronic wounds have gradually evolved into a global health challenge, comprising long-term non-healing wounds, local tissue necrosis, and even amputation in severe cases. Accordingly, chronic wounds place a considerable psychological and economic burden on patients and society. Chronic wounds have multifaceted pathogenesis involving excessive inflammation, insufficient angiogenesis, and elevated reactive oxygen species levels, with bacterial infection playing a crucial role. Hydrogels, renowned for their excellent biocompatibility, moisture retention, swelling properties, and oxygen permeability, have emerged as promising wound repair dressings. However, hydrogels with singular functions fall short of addressing the complex requirements associated with chronic wound healing. Hence, current research emphasises the development of multifunctional antibacterial hydrogels. This article reviews chronic wound characteristics and the properties and classification of antibacterial hydrogels, as well as their potential application in chronic wound management.

AgNPs loaded adenine-modified chitosan composite POSS-PEG hybrid hydrogel with enhanced antibacterial and cell proliferation properties for promotion of infected wound healing

Wound healing is a dynamic and complex process, it's urgent to develop new wound dressings with excellent performance to promote wound healing at the different stages. Here, a novel composite hydrogel dressing composed by silver nanoparticles (AgNPs) impregnated adenine-modified chitosan (CS-A) and octafunctionalized polyhedral oligomeric silsesquioxane (POSS) of benzaldehyde-terminated polyethylene glycol (POSS-PEG-CHO) solution was presented to solve the problem of wound infection. Modification of chitosan with adenine, not only can improve the water solubility of chitosan, but also introduce bioactive substances to promote cell proliferation. CS-A and POSS-PEG-CHO were cross-linked by Schiff-base reaction to form the injectable self-healing hydrogel. On this basis, AgNPs were added into the hydrogel, which endows the hydrogel with better antibacterial activity. Moreover, this kind of hydrogel exhibits excellent cell proliferation properties. Studies demonstrated that the hydrogel can significantly accelerate the closure of infected wounds. The histological analysis and immunofluorescence staining demonstrated that the wounds treated with the composite hydrogel exhibited fewer inflammatory cells, more collagen deposition and angiogenesis, faster regeneration of epithelial tissue. Above all, adenine-modified chitosan composite hydrogel with AgNPs loaded was considered as a dressing material with great application potential for promoting the healing of infected wounds.

CO2-Mediated Alkali-Neutralization Curdlan Hydrogels for Potential Wound Healing Application

Physical hydrogels of natural polysaccharides are considered as ideal candidates for wound dressing due to their natural biological activity and no harmful cross-linking agents. However, it remains a challenge to fabricate such hydrogel dressings in a facile and low-cost way. Herein, we reported an easy and cost-effective method to construct CO2-mediated alkali-neutralization Curdlan (CR) hydrogels without using an external cross-linking agent. Two types of hydrogels (denoted as CR-NaOH and CR-Na3PO4, respectively) were fabricated by dissolving CR powders in a NaOH or Na3PO4 aqueous solution, followed by keeping the CR alkaline solutions in air. The obtained pure CR hydrogels possessed a tunable porous structure with walls containing different forms of nanofibrils. These hydrogels exhibited much higher gel strength by comparison with the gels prepared by conventional heating treatment. They were flexible, stretchable, twistable, and conformable to arbitrarily curved skins. Moreover, they exhibited ideal swellability, proper degradability, and water vapor transmission rate, and their physicochemical properties were closely related to CR concentration in the alkaline solution. These two hydrogels also supported the growth of L929 cells. Importantly, studies on wound healing revealed that both 3CR-NaOH and 3CR-Na3PO4 hydrogels were capable of accelerating the wound healing process through recruiting more macrophages/fibroblasts, inducing more collagen deposition and neovascularization (α-SMA and CD31) without carrying any exogenous bioactive components. In conclusion, the present work not only reported promising materials for application in wound therapy but also offered a facile and safe manufacturing procedure for generating pure CR physical hydrogels with better performance.

Multifunctional sodium lignosulfonate/xanthan gum/sodium alginate/polyacrylamide ionic hydrogels composite as a high-performance wearable strain sensor

Recently, conductive hydrogels have shown great promise in flexible electronics and are ideal materials for the preparation of wearable strain sensors. However, developing a simple method to produce conductive hydrogels with excellent mechanical properties, self-adhesion, transparency, anti-freezing, and UV resistance remains a significant challenge. A novel sodium lignosulfonate/xanthan gum/sodium alginate/polyacrylamide/Zn2+/DMSO (SLS/XG/SA/PAM/Zn2+/DMSO) ionic conductive hydrogel was developed using a one-pot method. The resulting ionic conductive hydrogels have excellent mechanical properties (stress: 0.13 MPa, strain: 1629 %), high anti-fatigue properties, self-adhesion properties (iron: 7.37 kPa, pigskin: 4.74 kPa), anti-freezing (freezing point: -33.49 °C) and UV resistance by constructing a chemical and physical hybrid cross-linking network. In particular, the conductivity of G hydrogel reached 6.02 S/m at room temperature and 5.52 S/m at -20 °C. Thus, the hydrogel was assembled into a flexible sensor that could distinguish a variety of large and small scales human movements, such as joint bending, swallowing and speaking in real time with high stability and sensitivity. Moreover, the hydrogel could be used as electronic skin just like human skin and touch screen pen to write.

Physically cross-linked chitosan gel with tunable mechanics and biodegradability for tissue engineering scaffold

Chitosan, a cationic polysaccharide, exhibits promising potential for tissue engineering applications. However, the poor mechanical properties and rapid biodegradation have been the major limitations for its applications. In this work, an effective strategy was proposed to optimize the mechanical performance and degradation rate of chitosan gel scaffolds by regulating the water content. Physical chitosan hydrogel (HG, with 93.57 % water) was prepared by temperature-controlled cross-linking, followed by dehydration to obtain xerogel (XG, with 2.84 % water) and rehydration to produce wet gel (WG, with 56.06 % water). During this process, changes of water content significantly influenced the water existence state, hydrogen bonding, and the chain entanglements of chitosan in the gel network. The mechanical compression results showed that the chitosan gel scaffolds exhibited tunable compressive strength (0.3128-139 MPa) and compressive modulus (0.2408-1094 MPa). XG could support weights exceeding 65,000 times its own mass while maintaining structural stability. Furthermore, in vitro and in vivo experiments demonstrated that XG and WG exhibited better biocompatibility and resistance to biodegradation compared with HG. Overall, this work contributes to the design and optimization of chitosan scaffolds without additional chemical crosslinkers, which has potential in tissue engineering and further clinical translation.

A highly stretchable, adhesive, and antibacterial hydrogel with chitosan and tobramycin as dynamic cross-linkers for treating the infected diabetic wound

Diabetic wounds pose a significant challenge due to their susceptibility to bacterial infection in a high-glucose environment, which impedes the wound healing process. To address this issue, there is a pressing need to develop suitable hydrogels that can promote the regeneration of diabetic wounds in clinical practice. In this study, we designed and fabricated a highly stretchable, adhesive, transparent, and antibacterial hydrogel through a one-pot radical polymerization of N-[Tris (hydroxymethyl) methyl] acrylamide (THMA) and acrylic acid (AA), and with chitosan and the antibiotic tobramycin as the dynamic physical crosslinkers. The copolymer contains a large number of carboxyl and hydroxyl groups, which can form an interpenetrating network structure with chitosan and tobramycin through multiple dynamic non-covalent bonds. This hydrogel exhibited over 1600 % elongation through an energy dissipation mechanism and strong adhesion to various surfaces without any chemical reaction. In vivo, studies conducted on a staphylococcus aureus-infected full-thickness diabetic skin wound model demonstrated that the hydrogel loaded with tobramycin as one of the crosslinkers had a long-lasting antibacterial activity and effectively accelerated wound healing. Therefore, the antibiotic-loaded adhesive hydrogel we proposed holds great promise as a treatment for bacteria-infected diabetic wounds.

Biocompatible and biodegradable Bletilla striata polysaccharides hydrogels crosslinked by BDDE for wound healing through the regulating of macrophage polarization

Bletilla striata polysaccharide (BSP) is a naturally occurring polysaccharide that demonstrates notable biocompatibility and biodegradability. Additionally, BSP possesses therapeutic attributes, including anti-inflammatory and reparative actions. Herein, we report a novel BSP hydrogel prepared using 1,4-butanediol diglycidyl ether (BDDE) as a cross-linking agent. The hydrogel was synthesized via condensation of the hydroxyl group in the BSP molecule with the epoxy group in BDDE. This technique of preparation preserves BSP's natural properties while avoiding any potentially hazardous or adverse effects that may occur during the chemical alteration. Compared with BSP before crosslinking, BSP hydrogel has distinct advantages, such as a three-dimensional network structure, improved water retention, enhanced swelling capacity, greater thermal stability, and superior mechanical properties. Experiments on in vitro cytotoxicity, hemolysis, and degradation revealed that BSP hydrogel had good biocompatibility and biodegradability. Finally, we evaluated the in vivo wound repair effect of BSP hydrogel, and the results showed that BSP hydrogel had a significant wound-healing effect. Furthermore, the BSP hydrogel promoted the polarization of M1-type macrophages towards the M2-type and reduced the inflammatory response during the wound healing phase. Because of its ease of production, safety, efficacy, and environmental friendliness, BSP hydrogel is considered a highly promising material for wound dressings.

Recent advances in biopolymer-based hydrogels and their potential biomedical applications

Hydrogels are three-dimensional networks of polymer chains containing large amounts of water in their structure. Hydrogels have received significant attention in biomedical applications owing to their attractive physicochemical properties, including flexibility, softness, biodegradability, and biocompatibility. Different natural and synthetic polymers have been intensely explored in developing hydrogels for the desired applications. Biopolymers-based hydrogels have advantages over synthetic polymers regarding improved cellular activity and weak immune response. These properties can be further improved by grafting with other polymers or adding nanomaterials, and they structurally mimic the living tissue environments, which opens their broad applicability. The hydrogels can be physically or chemically cross-linked depending on the structure. The use of different biopolymers-based hydrogels in biomedical applications has been reviewed and discussed earlier. However, no report is still available to comprehensively introduce the synthesis, advantages, disadvantages, and biomedical applications of biopolymers-based hydrogels from the material point of view. Herein, we systematically overview different synthesis methods of hydrogels and provide a holistic approach to biopolymers-based hydrogels for biomedical applications, especially in bone regeneration, wound healing, drug delivery, bioimaging, and therapy. The current challenges and prospects of biopolymers-based hydrogels are highlighted rationally, giving an insight into the progress of these hydrogels and their practical applications.

Natural polymer-based bioadhesives as hemostatic platforms for wound healing

Medical adhesives are advanced but challenging alternatives to wound closure and repair, especially in mitigating uncontrolled hemorrhage. Ideal hemostatic adhesives need to meet good biocompatibility and biodegradability, adequate mechanical strength, and strong tissue adhesion functionality under wet and dynamic conditions. Considering these requirements, natural polymers such as polysaccharide, protein and DNA, attract great attention as candidates for making bioadhesives because of their distinctive physicochemical performances and biological properties. This review systematically summarizes the advances of bioadhesives based on natural polysaccharide, protein and DNA. Various physical and chemical cross-linking strategies have been introduced for adhesive synthesis and their hemostatic applications are introduced from the aspect of versatility. Furthermore, the possible challenges and future opportunities of bioadhesives are discussed, providing insights into the development of high-performance hemostatic materials.

Smart chitosan-based microgels for enhanced photothermal-assisted antibacterial activity

During recent years, antibiotic-resistant bacteria have rapidly emerged owing to the irrational use of antibiotics, rendering a global problem. Currently, few studies introduce customized antibacterial nanoplatforms to overcome antibiotic-resistance according to specific characteristic of bacteria, rather than abuse of antibiotic. Herein, with regard to personalized antibacterial nanoplatform, we design a novel antibiotic delivery nanocarrier composed of polyaniline-grafted-chitosan, presenting pH-responsive, conductive, photothermal, and biodegradable properties. After treatment with divalent anion (SO42-), the negatively charged nanocarriers are obtained for improving the loading efficacy of cationic vancomycin. Meanwhile, the controlled vancomycin release is achieved by lysozyme-triggered degradation of the nanocarrier. With the assistance of photothermal effect, the photothermal-assisted antibacterial effect of the nanocarriers have been effectively enhanced rather than that of a single antibacterial effect of vancomycin. Owing to the low heat resistance of Escherichia coli, photothermal effect can break the antibiotic-resistant bacteria membrane to render the convenient antibiotic entry, leading to the improved antibacterial efficacy. Therefore, the customization of a photothermal-assisted antibacterial on account of the characteristic of specific bacteria can definitely expand our arsenal for enhancing the antibacterial effect against antibiotic-resistant bacteria.

Mesoporous chitosan nanofibers loaded with norfloxacin and coated with phenylboronic acid perform as bioabsorbable active dressings to accelerate the healing of burn wounds

The paper reports new chitosan-based nanofibers, designed to address the healing of burn wounds. To this aim, mesoporous chitosan fiber mats were prepared by electrospinning using poly(ethylene oxide) as sacrificial additive, followed by loading with norfloxacin and coating with an antifungal agent via dynamic imine bonds. Dynamic vapor sorption experiment proved intra-fiber mesopores around 2.7 nm, and UV-vis, FTIR, and NMR spectroscopy confirmed the norfloxacin embedding and the imination reaction. SEM, AFM and POM techniques displayed semicrystalline nanofibers with average diameter around 170 nm entangled into a non-woven mat. Their mesoporous nature favored a rapid adsorption of fluids up to 17 g/g, and a biodegradation rate fitting the wound healing rate, i.e. up to 30 % mass loss in media of pH characteristic to wound exudate and total degradation in that characteristic to normal dermis. The composite fibers released the NFX and 2FPBA in a controlled manner, and showed antimicrobial activity against gram positive, gram negative and fungal strains. They had no cytotoxic effect on normal human dermal fibroblasts, and showed biocompatibility on experimental rats. The investigation of wound healing ability on second/third-degree burn model in rats revealed wound closure and total restoration of the fully functional dermis and epidermis.

Mussel-Inspired Wet-Adhesive Multifunctional Organohydrogel with Extreme Environmental Tolerance for Wearable Strain Sensor

As a flexible artificial material, the conductive hydrogel has broad application prospects in flexible wearable electronics, soft robotics, and biomedical monitoring. However, traditional hydrogels still face many challenges, such as long-term stability, availability in extreme environments, and long-lasting adhesion to the skin surface under sweaty or humid conditions. To circumvent the above issues, one kind of ionic conductive hydrogel was prepared by a simple one-pot method that dissolved chitosan (CS), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), tannic acid (TA), and 2-methoxy-ethyl acrylate (MEA) into dimethyl sulfoxide (DMSO)/H2O solvent. The resulting hydrogel showed excellent tensile properties (1440%), extreme environmental tolerance (-40-60 °C), adhesion (72 KPa at porcine skin), ionic conductivity (0.87 S m-1), and high-efficiency antibacterial property. Furthermore, the produced organohydrogel strain sensor exhibited high strain sensitivity (GF = 4.07), excellent signal sensing capabilities (human joint movement, microexpression, and sound signals), and long-term cyclic stability (400 cycles). Looking beyond, this work provides a simple and promising strategy for using hydrogel sensors in extreme environments for e-skin, health monitoring, and wearable electronic devices.

A recyclable biomass electrolyte towards green zinc-ion batteries

The operation of traditional aqueous-electrolyte zinc-ion batteries is adversely affected by the uncontrollable growth of zinc dendrites and the occurrence of side reactions. These problems can be avoided by the development of functional hydrogel electrolytes as replacements for aqueous electrolytes. However, the mechanism by which most hydrogel electrolytes inhibit the growth of zinc dendrites on a zinc anode has not been investigated in detail, and there is a lack of a large-scale recovery method for mainstream hydrogel electrolytes. In this paper, we describe the development of a recyclable and biodegradable hydrogel electrolyte based on natural biomaterials, namely chitosan and polyaspartic acid. The distinctive adsorptivity and inducibility of chitosan and polyaspartic acid in the hydrogel electrolyte triggers a double coupling network and an associated synergistic inhibition mechanism, thereby effectively inhibiting the side reactions on the zinc anode. In addition, this hydrogel electrolyte played a crucial role in an aqueous acid-based Zinc/MnO₂ battery, by maintaining its interior two-electron redox reaction and inhibiting the formation of zinc dendrites. Furthermore, the sustainable biomass-based hydrogel electrolyte is biodegradable, and could be recovered from the Zinc/MnO₂ battery for subsequent recycling.

Selenide-linked polydopamine-reinforced hybrid hydrogels with on-demand degradation and light-triggered nanozyme release for diabetic wound healing

BACKGROUND

Multifunctional hydrogels with controllable degradation and drug release have attracted extensive attention in diabetic wound healing. This study focused on the acceleration of diabetic wound healing with selenide-linked polydopamine-reinforced hybrid hydrogels with on-demand degradation and light-triggered nanozyme release.

METHODS

Herein, selenium-containing hybrid hydrogels, defined as DSeP@PB, were fabricated via the reinforcement of selenol-end capping polyethylene glycol (PEG) hydrogels by polydopamine nanoparticles (PDANPs) and Prussian blue nanozymes in a one-pot approach in the absence of any other chemical additive or organic solvent based on diselenide and selenide bonding-guided crosslinking, making them accessible for large-scale mass production.

RESULTS

Reinforcement by PDANPs greatly increases the mechanical properties of the hydrogels, realizing excellent injectability and flexible mechanical properties for DSeP@PB. Dynamic diselenide introduction endowed the hydrogels with on-demand degradation under reducing or oxidizing conditions and light-triggered nanozyme release. The bioactivity of Prussian blue nanozymes afforded the hydrogels with efficient antibacterial, ROS-scavenging and immunomodulatory effects, which protected cells from oxidative damage and reduced inflammation. Further animal studies indicated that DSeP@PB under red light irradiation showed the most efficient wound healing activity by stimulating angiogenesis and collagen deposition and inhibiting inflammation.

CONCLUSION

The combined merits of DSeP@PB (on-demand degradation, light-triggered release, flexible mechanical robustness, antibacterial, ROS-scavenging and immunomodulatory capacities) enable its high potential as a new hydrogel dressing that can be harnessed for safe and efficient therapeutics for diabetic wound healing.

Shape memory and antibacterial chitosan-based cryogel with hemostasis and skin wound repair

Massive damage to the skin can lead to heavy bleeding and potential wound infection. Therefore, the preparation of low-cost wound dressings that meet these requirements by simple methods has a good application prospect. In the study, a shape memory cryogel prepared at low temperatures by mixing chitosan (CS) and citric acid (CA). Silver nanoparticles (Ag NPs) introduced into the cryogel through the reduction of Ag⁺ with tannic acid (TA) as a reducing agent. The CS/CA/Ag cryogel has good mechanical properties and interconnected macroporous structures. The results of hemostasis tests show that CS/CA/Ag cryogel can absorb a large amount of blood and promote blood cell adhesion compared with commercial gelatin sponges and gauze. Meanwhile, CS/CA/Ag cryogel has a good antibacterial ability against S. aureus and E. coli. Furthermore, CS/CA/Ag cryogel significantly promotes wound healing in the full-thickness wound model infected with S. aureus. In conclusion, the cryogel prepared by the simple method has great advantages in rapid hemostasis and promoting wound healing.

Chitosan-based carbon nitride-polydopamine‑silver composite dressing with antibacterial properties for wound healing

Infection represents a major clinical barrier that delays wound healing, while the overuse of antibiotics can lead to bacterial resistance. Hence, it is of particular important to develop a new type of dressing to combat bacterial resistance. Herein, a carbon nitride-polydopamine‑silver complex (C₃N₄-PDA-Ag) was prepared using the photocatalyst C₃N₄ and silver nanoparticles (Ag NPs) to achieve a synergistic antimicrobial effect. The solution casting method was then employed to further modify the C₃N₄-PDA-Ag complex by compounding it with chitosan (CS), thereby forming a C₃N₄-PDA-Ag@CS film. The results revealed that the C₃N₄-PDA-Ag@CS film exhibits superior antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa compared to the CS group. The hemolysis, cytotoxicity, and in vivo implantation experiments indicated that the composite film possesses excellent in vitro and in vivo biocompatibility. In addition, the composite dressing promoted wound healing in infected mice by facilitating collagen deposition and accelerating epidermal regeneration. Collectively, the findings of this study clearly demonstrate that the C₃N₄-PDA-Ag@CS composite dressing has excellent antibacterial properties, biocompatibility, and enhances wound healing, thus providing a strategy for the application of photocatalytic materials for the treatment of infected wounds.

Self-healing, self-adhesive, and stretchable conductive hydrogel for multifunctional sensor prepared by catechol modified nanocellulose stabilized poly(α-thioctic acid)

Self-healing, self-adhesive, and stretchable bio-based conductive hydrogels exhibit properties similar to those of biological tissues, making them an urgent requirement for emerging wearable devices. The primary challenge lies in devising straightforward strategies to accomplish all the aforementioned performances and achieve equilibrium among them. This study used the natural compound thioctic acid (TA) and modified cellulose to prepare conductive hydrogels with stretchability, healing, and self-adhesion through a simple one-step strategy. Metastable poly(TA) was obtained through ring-opening polymerization of lithiated TA, followed by the introduction of dopamine-grafted cellulose nanofibers (DCNF) to stabilize poly(TA) and prepare PTALi/DCNF hydrogels with the aforementioned properties. The hydrogels demonstrated remarkable conductivity, attributed to the existence of Li + ions, with a maximum conductivity of 17.36 mS/cm. The self-healing capacity of the hydrogels was achieved owing to the presence of disulfide bond in TA. The introduction of DCNF can effectively stabilize poly(TA), endow the hydrogel with self-adhesion ability, improve the mechanical properties, and further enhance the formability of hydrogels. Generally, bio-based PTALi/DCNF hydrogels with stretchability, self-healing, self-adhesion, and conductivity are obtained through a simple strategy and used as a sensor with a wide response range and high sensitivity. Hydrogels have significant potential for application in wearable electronic devices, electronic skins, and soft robots.

New insights into balancing wound healing and scarless skin repair

Scars caused by skin injuries after burns, wounds, abrasions and operations have serious physical and psychological effects on patients. In recent years, the research of scar free wound repair has been greatly expanded. However, understanding the complex mechanisms of wound healing, in which various cells, cytokines and mechanical force interact, is critical to developing a treatment that can achieve scarless wound healing. Therefore, this paper reviews the types of wounds, the mechanism of scar formation in the healing process, and the current research progress on the dual consideration of wound healing and scar prevention, and some strategies for the treatment of scar free wound repair.

A CS-based composite scaffold with excellent photothermal effect and its application in full-thickness skin wound healing

The development of natural polymer-based scaffolds with excellent biocompatibility, antibacterial activity, and blood compatibility, able to facilitate full-thickness skin wound healing, remains challenging. In this study, we have developed three chitosan (CS)-based porous scaffolds, including CS, CS/CNT (carbon nanotubes) and CS/CNT/HA (nano-hydroxyapatite, n-HA) using a freeze-drying method. All three scaffolds have a high swelling ratio, excellent antibacterial activity, outstanding cytocompatibility and blood compatibility in vitro. The introduction of CNTs exhibited an obvious increase in mechanical properties and exerts excellent photothermal response, which displays excellent healing performance as a wound dressing in mouse full-thickness skin wound model when compared to CS scaffolds. CS/CNT/HA composite scaffolds present the strongest ability to promote full-thickness cutaneous wound closure and skin regeneration, which might be ascribed to the synergistic effect of photothermal response from CNT and excellent bioactivity from n-HA. Overall, the present study indicated that CNT and n-HA can be engineered as effective constituents in wound dressings to facilitate full-thickness skin regeneration.

Aramid Nanofibers-Reinforced Rhein Fibrous Hydrogels as Antibacterial and Anti-Inflammatory Burn Wound Dressings

Burn injuries are one of the most devastating traumas. The development of polymer-based hydrogel dressings to prevent bacterial infection and accelerate burn wound healing is continuously desired. Mechanical strong hydrogels that encapsulated antibacterial drugs have gained increasing attention. Herein, aramid nanofibers (ANFs)-reinforced rhein fibrous hydrogels (ANFs/Rhein) were fabricated through a one-pot procedure to serve as a possible treatment for the Staphylococcus aureus-infected burn wound. ANFs preserved the highly aligned backbones and the mechanical properties of Kevlar, and its combination with an antibacterial drug rhein produced a composite hydrogel that possesses favorable physicochemical properties including appropriate mechanical strength, high water holding capacity, satisfactory antibacterial efficiency, and excellent biocompatibility. As wound dressings, ANFs/Rhein hydrogels provided a moist environment for the wound site and released antibacterial drugs continuously to improve the wound healing rate by efficiently restraining bacterial infection, reducing inflammation, enhancing collagen deposition, and promoting the formation of blood vessels, in this way to offer a potential treatment strategy for bacteria-associated burn wound healing.

Recent advances of the nanocomposite hydrogel as a local drug delivery for diabetic ulcers

Diabetic ulcer is a serious complication of diabetes. Compared with that of healthy people, the skin of patients with a diabetic ulcer is more easily damaged and difficult to heal. Without early intervention, the disease will become increasingly serious, often leading to amputation or even death. Most current treatment methods cannot achieve a good wound healing effect. Numerous studies have shown that a nanocomposite hydrogel serves as an ideal drug delivery method to promote the healing of a diabetic ulcer because of its better drug loading capacity and stability. Nanocomposite hydrogels can be loaded with one or more drugs for application to chronic ulcer wounds to promote rapid wound healing. Therefore, this paper reviews the latest progress of delivery systems based on nanocomposite hydrogels in promoting diabetic ulcer healing. Through a review of the recent literature, we put forward the shortcomings and improvement strategies of nanocomposite hydrogels in the treatment of diabetic ulcers.