Novel multifunctional adenine-modified chitosan dressings for promoting wound healing

Integration of Zn2+, ATP, and bFGF to Nanodressing with Core-Shell Structure Fabricated by Emulsion Electrospinning for Wound Healing

Basic fibroblast growth factor (bFGF) plays an important role in active wound repair. However, the existing dosage forms in clinical applications are mainly sprays and freeze-dried powders, which are prone to inactivation and cannot achieve a controlled release. In this study, a bioactive wound dressing named bFGF-ATP-Zn/polycaprolactone (PCL) nanodressing with a "core-shell" structure was fabricated by emulsion electrospinning, enabling the sustained release of bFGF. Based on the coordination and electrostatic interactions among bFGF, ATP, and Zn2+, as well as their synergistic effect on promoting wound healing, a bFGF-ATP-Zn ternary combination system was prepared with higher cell proliferation activity and used as the water phase for emulsion electrospinning. The bFGF-ATP-Zn/PCL nanodressing demonstrated improved mechanical properties, sustained release of bFGF, cytocompatibility, and hemocompatibility. It increased the proliferation activity of human dermal fibroblasts (HDFs) and enhanced collagen secretion by 1.39 and 3.45 times, respectively, while reducing the hemolysis rate to 3.13%. The application of the bFGF-ATP-Zn/PCL nanodressing in mouse full-thickness skin defect repair showed its ability to accelerate wound healing and reduce wound scarring within 14 days. These results provide a research basis for the development and application of this bioactive wound dressing product.

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.

A DNA-inspired injectable adhesive hydrogel with dual nitric oxide donors to promote angiogenesis for enhanced wound healing

Chronic diabetic wounds are a severe complication of diabetes, often leading to high treatment costs and high amputation rates. Numerous studies have revealed that nitric oxide (NO) therapy is a promising option because it favours wound revascularization. Here, base-paired injectable adhesive hydrogels (CAT) were prepared using adenine- and thymine-modified chitosan (CSA and CST). By further introducing S-nitrosoglutathione (GSNO) and binary l-arginine (bArg), we obtained a NO sustained-release hydrogel (CAT/bArg/GSON) that was more suitable for the treatment of chronic wounds. The results showed that the expression of HIF-1α and VEGF was upregulated in the CAT/bArg/GSON group, and improved blood vessel regeneration was observed, indicating an important role of NO. In addition, the research findings revealed that following treatment with the CAT/bArg/GSON hydrogel, the viability of Staphylococcus aureus and Escherichia coli decreased to 14 ± 2 % and 6 ± 1 %, respectively. Moreover, the wound microenvironment was improved, as evidenced by a 60 ± 1 % clearance of DPPH. In particular, histological examination and immunohistochemical staining results showed that wounds treated with CAT/bArg/GSNO exhibited denser neovascularization, faster epithelial tissue regeneration, and thicker collagen deposition. Overall, this study proposes an effective strategy to prepare injectable hydrogel dressings with dual NO donors. The functionality of CAT/bArg/GSON has been thoroughly demonstrated in research on chronic wound vascular regeneration, indicating that CAT/bArg/GSON could be a potential option for promoting chronic wound healing. STATEMENT OF SIGNIFICANCE: This article prepares a chitosan hydrogel utilizing the principle of complementary base pairing, which offers several advantages, including good adhesion, biocompatibility, and flow properties, making it a good material for wound dressings. Loaded GSNO and bArg can steadily release NO and l-arginine through the degradation of the gel. Then, the released l-arginine not only possesses antioxidant properties but can also continue to generate a small amount of NO under the action of NOS. This design achieves a sustained and stable supply of NO at the wound site, maximizing the angiogenesis-promoting and antibacterial effects of NO. More neovascularization and abundant collagen were observed in the regenerated tissues. This study provides an effective repair hydrogel material for diabetic wound.

3-Diethylaminopropyl isothiocyanate modified glycol chitosan for constructing mild-acid sensitive electrospinning antibacterial nanofiber membrane

Bacterial infections would cause pathological inflammation and even generate chronic wound. Herein, a ciprofloxacin (Cip)-loaded mild acid-responsive electrospinning nanofiber membrane (NFM) containing 3-diethylaminopropyl isothiocyanate material grafted glycol chitosan (GC-DEAP) was fabricated to prevent bacterial infection against hemostatic and inflammatory phases of wounds. The presence of Cip and GC-DEAP in the objective NFM (PCL/GC-DEAP/Cip) was confirmed through XRD and FTIR. Meanwhile, PCL/GC-DEAP/Cip NFM exhibited high mechanical profiles, suitable water absorption and water vapour transmission ratio. The non-protonated amphiphilic GC-DEAP under pH 7.4 facilitated the formation of uniform and smooth nanofibers with polycaprolactone (PCL) and Cip. However, the GC-DEAP was demonstrated to sharply respond to the mild-acid environment of the wound and effectively be protonated, and thus improved the swelling ability of NFM and triggered burst release of Cip. Due to the combination between protonated GC-DEAP and Cip, PCL/GC-DEAP/Cip NFM achieved attractive antibacterial activity in the mild-acid environment in vitro, and induced more efficient prevention of wound infection and faster wound healing compared with the commercial chitosan dressing. The designed NFM is expected to be a potential smart wound dressing against hemostatic and inflammatory phases with mild-acid specifically strengthened antibacterial features and satisfactory biocompatibility.

Fabrication and characterization of new levan@CBD biocomposite sponges as potential materials in natural, non-toxic wound dressing applications

Wound healing is a complex process; therefore, new dressings are frequently required to facilitate it. In this study, porous bacterial levan-based sponges containing cannabis oil (Lev@CBDs) were prepared and fully characterized. The sponges exhibited a suitable swelling ratio, proper water vapor transmission rate, sufficient thermal stability, desired mechanical properties, and good antioxidant and anti-inflammatory properties. The obtained Lev@CBD materials were evaluated in terms of their interaction with proteins, human serum albumin and fibrinogen, of which fibrinogen revealed the highest binding effect. Moreover, the obtained biomaterials exhibited antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa, as well as being non-hemolytic material as indicated by hemolysis tests. Furthermore, the sponges were non-toxic and compatible with L929 mouse fibroblasts and HDF cells. Most significantly, the levan sponge with the highest content of cannabis oil, in comparison to others, retained its non-hemolytic, anti-inflammatory, and antimicrobial properties after prolonged storage in a climate chamber at a constant temperature and relative humidity. The designed sponges have conclusively proven their beneficial physicochemical properties and, at the preliminary stage, biocompatibility as well, and therefore can be considered a promising material for wound dressings in future in vivo applications.

Current application and modification strategy of marine polysaccharides in tissue regeneration: A review

Marine polysaccharides (MPs) are exceptional bioactive materials that possess unique biochemical mechanisms and pharmacological stability, making them ideal for various tissue engineering applications. Certain MPs, including agarose, alginate, carrageenan, chitosan, and glucan have been successfully employed as biological scaffolds in animal studies. As carriers of signaling molecules, scaffolds can enhance the adhesion, growth, and differentiation of somatic cells, thereby significantly improving the tissue regeneration process. However, the biological benefits of pure MPs composite scaffold are limited. Therefore, physical, chemical, enzyme modification and other methods are employed to expand its efficacy. Chemically, the structural properties of MPs scaffolds can be altered through modifications to functional groups or molecular weight reduction, thereby enhancing their biological activities. Physically, MPs hydrogels and sponges emulate the natural extracellular matrix, creating a more conducive environment for tissue repair. The porosity and high permeability of MPs membranes and nanomaterials expedite wound healing. This review explores the distinctive properties and applications of select MPs in tissue regeneration, highlighting their structural versatility and biological applicability. Additionally, we provide a brief overview of common modification strategies employed for MP scaffolds. In conclusion, MPs have significant potential and are expected to be a novel regenerative material for tissue engineering.

Resveratrol-loaded co-axial electrospun poly(ε-caprolactone)/chitosan/polyvinyl alcohol membranes for promotion of cells osteogenesis and bone regeneration

The guided bone regeneration (GBR) membranes currently used in clinics are usually compromised by their limited osteogenic induction potential. In this study, we fabricate a core-shell poly(ε-caprolactone)/chitosan/polyvinyl alcohol (PCL/CS/PVA) GBR membrane with different amount of resveratrol (RSV), endowing the PCL/CS/PVA GBR membrane with superior osteogenic induction ability, which was not attained by the regular GBR membrane. The prepared GBR membranes were characterized by scanning electron microscopy, transmission electron microscopy, and CCK-8 and live-dead staining assays, and their osteogenic induction ability was evaluated using Col-I immunofluorescence staining, micro-computed tomography, haematoxylin and eosin staining and immunohistochemical staining. Results of the in vitro release experiment confirmed that the membranes exhibited a continuous RSV release profile for 15 days. Furthermore, the cumulative releasing of RSV was increased from 39.68 ± 2.09 μg to 65.8 ± 2.91 μg with increasing contents of RSV from 0.1 % to 0.5 % (w/v) in the core layer of GBR membranes. In particular, the PCL/CS/PVA GBR membrane loading with 0.5 % RSV most efficiently release RSV in a sustained and controlled manner, which significantly induced osteogenic differentiation of pre-osteoblasts in vitro and bone regeneration in vivo. Based on the in vivo histological findings, newly formed bone tissues with 82.46 ± 9.86 % BV/TV and 0.70 ± 0.07gcm-3 BMD were generated in the defect sites treated by the GBR membrane loaded with 0.5 % RSV, which were the largest values among those for all three groups after 12 weeks of post implantation. Overall, the PCL/CS/PVA GBR membrane loaded with 0.5 % RSV has significant potential for bone regeneration.

Chitosan-Based Composites: Development and Perspective in Food Preservation and Biomedical Applications

Chitin, which may be the second-most common polymer after cellulose, is the raw material of chitosan. Chitosan has been infused with various plant extracts and subsidiary polymers to improve its biological and physiological properties. Chitosan's physicochemical properties are enhanced by blending, making them potential candidates that can be utilized in multifunctional areas, including food processing, nutraceuticals, food quality monitoring, food packaging, and storage. Chitosan-based biomaterials are biocompatible, biodegradable, low toxic, mucoadhesive, and regulate chemical release. Therefore, they are used in the biomedical field. The present manuscript highlights the application of chitosan-based composites in the food and biomedical industries.

Accelerated Healing of Infected Diabetic Wounds by a Dual-Layered Adhesive Film Cored with Microsphere-Loaded Hydrogel Composite Dressing

Diabetic wounds, a prevalent chronic disease, are associated with older age. The hyperglycemic microenvironment in diabetic wounds significantly reduces the immune system, inducing bacterial invasion. The coupling of tissue repair and antibacterial treatment is critical for infected diabetic ulcer regeneration. In this study, a dual-layered sodium alginate/carboxymethyl chitosan (SA/CMCS) adhesive film cored with an SA-bFGF microsphere-loaded small intestine submucosa (SIS) hydrogel composite dressing with a graphene oxide (GO)-based antisense transformation system was developed to promote infected diabetic wound healing and bacterial eradication. Initially, our injectable SIS-based hydrogel composite stimulated angiogenesis, collagen deposition, and immunoregulation in diabetic wound repair. The GO-based transformation system subsequently inhibited bacterial viability in infected wounds by post-transformation regulation. Meanwhile, the SA/CMCS film provided stable adhesion covering the wound area to maintain a moist microenvironment, which promoted in situ tissue repair. Our findings provide a promising clinical translation strategy for promoting the healing of infected diabetic wounds.

Chitosan: A Potential Biopolymer in Drug Delivery and Biomedical Applications

Chitosan, a biocompatible and biodegradable polysaccharide derived from chitin, has surfaced as a material of promise for drug delivery and biomedical applications. Different chitin and chitosan extraction techniques can produce materials with unique properties, which can be further modified to enhance their bioactivities. Chitosan-based drug delivery systems have been developed for various routes of administration, including oral, ophthalmic, transdermal, nasal, and vaginal, allowing for targeted and sustained release of drugs. Additionally, chitosan has been used in numerous biomedical applications, such as bone regeneration, cartilage tissue regeneration, cardiac tissue regeneration, corneal regeneration, periodontal tissue regeneration, and wound healing. Moreover, chitosan has also been utilized in gene delivery, bioimaging, vaccination, and cosmeceutical applications. Modified chitosan derivatives have been developed to improve their biocompatibility and enhance their properties, resulting in innovative materials with promising potentials in various biomedical applications. This article summarizes the recent findings on chitosan and its application in drug delivery and biomedical science.

Synthesis and evaluation of water-soluble imidazolium salt chitin with broad-spectrum antimicrobial activity and excellent biocompatibility for infected wound healing

Infections caused by bacteria have long constituted a major threat to human health and the economy. Therefore, there is an urgent need to design broad-spectrum antibacterial materials possessing good biocompatibility to treat such infections. Herein, inspired by the good biocompatibility of chitin and antibacterial properties of imidazolium salts, a polysaccharide-based material, imidazolium salt chitin (IMSC), was homogeneously prepared using a facile method with epichlorohydrin as a chemical crosslinker to combine chitin with imidazole to enhance Staphylococcus aureus (S. aureus)-infected wound healing. The characteristics, antimicrobial properties, and biosafety of IMSC were evaluated. The results demonstrated successful grafting of imidazole onto chitin. Furthermore, IMSC exhibited good water solubility, broad-spectrum antimicrobial activity, hemocompatibility, and biocompatibility. Moreover, IMSC enabled complete healing of S. aureus-infected wound in Sprague-Dawley rats within 15 days of application, thus demonstrating that IMSC could reduce wound inflammation and remarkably accelerate wound healing owing to its efficient antibacterial activity and ability to promote collagen deposition in and around the wound area. Therefore, this study provides a promising and potential therapeutic strategy for infected wound healing by synthesizing a water-soluble and broad-spectrum antimicrobial material exhibiting good biocompatibility.

Review: Application of chitosan and its derivatives in medical materials

Chitin is a natural polymeric polysaccharide extracted from marine crustaceans, and chitosan is obtained by removing part of the acetyl group (usually more than 60 %) in chitin's structure. Chitosan has attracted wide attention from researchers worldwide due to its good biodegradability, biocompatibility, hypoallergenic and biological activities (antibacterial, immune and antitumor activities). However, research has shown that chitosan does not melt or dissolve in water, alkaline solutions and general organic solvents, which greatly limits its application range. Therefore, researchers have carried out extensive and in-depth chemical modification of chitosan and prepared a variety of chitosan derivatives, which have expanded the application field of chitosan. Among them, the most extensive research has been conducted in the pharmaceutical field. This paper summarizes the application of chitosan and chitosan derivatives in medical materials over the past five years.

Injectable, self-healing, transparent, and antibacterial hydrogels based on chitosan and dextran for wound dressings

One major shortcoming of biopolymeric based wound dressing so far is the lack of an integrated multi-functional system that could provide suitable mechanical strength, fast self-healing, transparency, antibacterial and antioxidant effects. Benefiting from the dynamic and rapid reaction between glycidyl trimethyl ammonium chloride-graft- chitosan (QCS) and aldehyde-dextran (ODex) under physiological conditions, we designed hydrogels (QCS-ODex) with fast in situ gel-forming (< 70 s), porous structure (300-350 μm), stable storage modulus and the loss modulus, suitable swelling capacity (2.465 folds of chitosan), tissue adhesion, transmission property, free radical scavenging capacity, good self-healing behavior, and injectability, inherent antibacterial (against E. coli and S. aureus) and biocompatibility. Furthermore, Baicalein could be in situ encapsulated into QCS-ODex hydrogels, and the release behavior of Baicalein could be regulated by adjusting the ratio of QCS and ODex. The Baicalein-loaded QCS-ODex hydrogel further facilitated free radical scavenging and antibacterial bioactivities due to the cooperative therapeutic effects between QCS-ODex and Baicalein. This study may provide new insights into designing multi-functional QCS-ODex hydrogels with multiple therapeutic effects as a wound dressing.

Antimicrobial Nano-Zinc Oxide Biocomposites for Wound Healing Applications: A Review

Chronic wounds are a major concern for global health, affecting millions of individuals worldwide. As their occurrence is correlated with age and age-related comorbidities, their incidence in the population is set to increase in the forthcoming years. This burden is further worsened by the rise of antimicrobial resistance (AMR), which causes wound infections that are increasingly hard to treat with current antibiotics. Antimicrobial bionanocomposites are an emerging class of materials that combine the biocompatibility and tissue-mimicking properties of biomacromolecules with the antimicrobial activity of metal or metal oxide nanoparticles. Among these nanostructured agents, zinc oxide (ZnO) is one of the most promising for its microbicidal effects and its anti-inflammatory properties, and as a source of essential zinc ions. This review analyses the most recent developments in the field of nano-ZnO–bionanocomposite (nZnO-BNC) materials—mainly in the form of films, but also hydrogel or electrospun bandages—from the different preparation techniques to their properties and antibacterial and wound-healing performances. The effect of nanostructured ZnO on the mechanical, water and gas barrier, swelling, optical, thermal, water affinity, and drug-release properties are examined and linked to the preparation methods. Antimicrobial assays over a wide range of bacterial strains are extensively surveyed, and wound-healing studies are finally considered to provide a comprehensive assessment framework. While early results are promising, a systematic and standardised testing procedure for the comparison of antibacterial properties is still lacking, partly because of a not-yet fully understood antimicrobial mechanism. This work, therefore, allowed, on one hand, the determination of the best strategies for the design, engineering, and application of n-ZnO-BNC, and, on the other hand, the identification of the current challenges and opportunities for future research.

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.

A self-fused hydrogel for the treatment of glottic insufficiency through outstanding durability, extracellular matrix-inducing bioactivity and function preservation

Injection laryngoplasty with biomaterials is an effective technique to treat glottic insufficiency. However, the inadequate durability, deficient pro-secretion of extracellular matrix (ECM) and poor functional preservation of current biomaterials have yielded an unsatisfactory therapeutic effect. Herein, a self-fusing bioactive hydrogel comprising modified carboxymethyl chitosan and sodium alginate is developed through a dual-crosslinking mechanism (photo-triggered and dynamic covalent bonds). Owing to its characteristic networks, the synergistic effect of the hydrogel for vocal folds (VFs) vibration and phonation is adequately demonstrated. Notably, owing to its inherent bioactivity of polysaccharides, the hydrogel could significantly enhance the secretion of major components (type I/III collagen and elastin) in the lamina propria of the VFs both in vivo and in vitro. In a rabbit model for glottic insufficiency, the optimized hydrogel (C₁A₁) has demonstrated a durability far superior to that of the commercially made hyaluronic acid (HA) Gel. More importantly, owing to the ECM-inducing bioactivity, the physiological functions of the VFs treated with the C₁A₁ hydrogel also outperformed that of the HA Gel, and were similar to those of the normal VFs. Taken together, through a simple-yet-effective strategy, the novel hydrogel has demonstrated outstanding durability, ECM-inducing bioactivity and physiological function preservation, therefore has an appealing clinical value for treating glottic insufficiency.

Construction of multifunctional wound dressings with their application in chronic wound treatment

As the prevalence of diabetes increases year by year and the aging population continues to intensify in the world, chronic wounds such as diabetic foot ulcers and pressure ulcers have become serious problems that threaten people's health, and have brought an enormous burden to the world healthcare system. Conventional clinical treatment of chronic wounds relies on non-specific topical care (including debridement, infection/inflammation control, and frequent wound dressing changes), which can alleviate disease progression and reduce patient suffering to a certain extent, but the overall cure rate is less than 50% and the recurrence rate is high. Traditional wound dressings such as gauze, hydrocolloids, films and foams are single-function, acting as a physical barrier or absorbing exudates, and cannot meet all the needs of the entire chronic wound healing process. Recently, a large number of novel functional dressings have been reported for chronic wound repair. Based on the progress on wound dressings in recent years and the relevant research experience of our group, the review summarizes and discusses the progress on multifunctional wound dressings (such as microneedles, sponges and hydrogels) with anti-inflammatory, antioxidant, antibacterial, pro-angiogenic and tissue adhesive functions in detail. At the same time, the various responsive mechanisms (in vivo microenvironment or in vitro stimulation) of the smart multifunctional wound dressing are also analyzed in detail. It is expected that the review could provide some inspiration and suggestions for research on dressings for chronic wound treatment.

Fabrication of Biocompatible Electrospun Poly(ε-caprolactone)/Gelatin Nanofibers Loaded with Pinus radiata Bark Extracts for Wound Healing Applications

In this study, poly(ε-caprolactone) (PCL)/gelatin (GEL) electrospun nanofibers loaded with two different concentrations of Pinus radiata bark extracts (PEs) were fabricated via electrospinning for wound healing applications. The effects of incorporating PE into PCL/GEL electrospun nanofibers were investigated regarding their physicochemical properties and in vitro biocompatibility. All electrospun nanofibers showed smooth, uniform, and bead-free surfaces. Their functional groups were detected by ATR-FTIR spectroscopy, and their total phenol content was measured by a Folin–Ciocalteu assay. With PE addition, the electrospun nanofibers exhibited an increase in their wettability and degradation rates over time and a decrease in their tensile stress values from 20 ± 4 to 8 ± 2 MPa for PCL/GEL and PCL/GEL/0.36%PE samples, respectively. PE was also released from the fibrous mats in a rather controlled fashion. The PCL/GEL/0.18%PE and PCL/GEL/0.36%PE electrospun nanofibers inhibited bacterial activity at around 6 ± 0.1% and 23 ± 0.3% against E. coli and 14 ± 0.1% and 18 ± 0.2% against S. aureus after 24 h incubation, respectively. In vitro cell studies showed that PE-loaded electrospun nanofibers enhanced HaCaT cell growth, attachment, and proliferation, favoring cell migration towards the scratch area in the wound healing assay and allowing a complete wound closure after 72 h treatment. These findings suggested that PE-loaded electrospun nanofibers are promising materials for antibiotic-free dressings for wound healing applications.

Supramolecular Thermo-Contracting Adhesive Hydrogel with Self-Removability Simultaneously Enhancing Noninvasive Wound Closure and MRSA-Infected Wound Healing

Conventional wound closure and dressing are two crucial, time-consuming but isolated principles in wound care. Even though tissue adhesive opens a new era for wound closure, the method and biomaterial that can simultaneously achieve noninvasive wound closure and promote wound healing are highly appreciated. Herein, a novel supramolecular poly(N-isopropylacrylamide) hybrid hydrogel dressing composed of quaternized chitosan-graft-β-cyclodextrin, adenine, and polypyrrole nanotubes via host-guest interaction and hydrogen bonds is developed. The hydrogel demonstrates thermal contraction of 47% remaining area after 2 h at 37 ℃ and tissue adhesion of 5.74 kPa, which are essential for noninvasive wound closure, and multiple mechanical and biological properties including suitable mechanical properties, self-healing, on-demand removal, antioxidant, hemostasis, and photothermal/intrinsic antibacterial activity (higher 99% killing ratio within 5 min after irradiation). In both full-thickness skin incision and excision wound models, the hydrogel reveals significant wound closure after 24 h post-surgery. In acute and methicillin-resistant Staphylococcus aureus-infected wound and photothermal/intrinsic antibacterial activity assays, wounds treated with the hydrogel demonstrate enhanced wound healing with rapid wound closure rate, mild inflammatory response, advanced angiogenesis, and well-arranged collagen fibers. Altogether, the results indicate the hydrogel is promising in synchronously noninvasive wound closure and enhanced wound healing.

Multifunctional Double-Layer Composite Hydrogel Conduit Based on Chitosan for Peripheral Nerve Repairing

Peripheral nerve regeneration and functional recovery is a major challenge in clinical practice. Nerve conduit is an effective treatment for peripheral nerve repair, but the traditional hollow nerve conduit is not satisfactory in peripheral nerve repair due to the limitation of cell migration and nutrient transport. Herein, the double cross-linked hydrogels with injectable, self-healing, and conductive properties are synthesized by the Schiff base reaction between polyaniline-modified carboxymethyl chitosan and aldehyde-modified Pluronic F-127 (F127-CHO), and the hydrophobic interaction of F127-CHO. The conductive hydrogel is injected into the cavity of chitosan conduit prepared by electrodeposition. The inner conductive hydrogel and the outer chitosan conduit are formed into a whole through the Schiff base reaction to obtain a double-layer composite hydrogel nerve conduit. The double-layer composite hydrogel neural conduit loaded with 7,8-dihydroxyflavone (DHF) has excellent degradability, biocompatibility, antioxidant activity, and Schwann cell proliferation activity. In the rat sciatic nerve defect model, the double-layer composite hydrogel nerve conduit significantly promotes sciatic nerve regeneration compared with the chitosan hollow conduit. Surprisingly, the repair ability of double-layered hydrogel nerve conduit loaded with DHF is comparable to that of autologous transplantation. Therefore, this multifunctional double-layer composite hydrogel conduit has great potential for peripheral nerve repairing.

Chitosan/Alginate Hydrogel Dressing Loaded FGF/VE-Cadherin to Accelerate Full-Thickness Skin Regeneration and More Normal Skin Repairs

The process of full-thickness skin regeneration is complex and has many parameters involved, which makes it difficult to use a single dressing to meet the various requirements of the complete regeneration at the same time. Therefore, developing hydrogel dressings with multifunction, including tunable rheological properties and aperture, hemostatic, antibacterial and super cytocompatibility, is a desirable candidate in wound healing. In this study, a series of complex hydrogels were developed via the hydrogen bond and covalent bond between chitosan (CS) and alginate (SA). These hydrogels exhibited suitable pore size and tunable rheological properties for cell adhesion. Chitosan endowed hemostatic, antibacterial properties and great cytocompatibility and thus solved two primary problems in the early stage of the wound healing process. Moreover, the sustained cytocompatibility of the hydrogels was further investigated after adding FGF and VE-cadherin via the co-culture of L929 and EC for 12 days. The confocal 3D fluorescent images showed that the cells were spherical and tended to form multicellular spheroids, which distributed in about 40-60 μm thick hydrogels. Furthermore, the hydrogel dressings significantly accelerate defected skin turn to normal skin with proper epithelial thickness and new blood vessels and hair follicles through the histological analysis of in vivo wound healing. The findings mentioned above demonstrated that the CS/SA hydrogels with growth factors have great potential as multifunctional hydrogel dressings for full-thickness skin regeneration incorporated with hemostatic, antibacterial, sustained cytocompatibility for 3D cell culture and normal skin repairing.

Chitosan-based hydrogels with injectable, self-healing and antibacterial properties for wound healing

Developing an efficient and available material for improved cutaneous tissue regeneration is a major challenge in healthcare. Inspired by the concept of moist wound healing, the injectable and self-healing adenine-modified chitosan (AC) hydrogels are designed to significantly accelerate wound healing without the addition of therapeutic drugs. A series of AC derivatives with degree of substitution (DS) ranging from 0.21 to 0.55 were synthesized in aqueous solutions, and the AC hydrogels were prepared by a simple heating/cooling process. AC hydrogels presented good self-healing, low swelling rate capacity, biocompatibility, promote cell proliferation and excellent hemostatic effect. The hydrogels displayed excellent antibacterial activities against gram-negative bacteria, gram-positive bacteria, fungi and drug-resistance bacteria. Moreover, the full-thickness skin defect model experiments showed that AC hydrogels could reduce inflammatory cell infiltration and accelerate wound healing significantly. The hydrogel can shed new light on designing of the multifunctional dressings for wound healing.

Antimicrobial cotton gauzes modified with poly(acrylic acid-co-maltodextrin) hydrogel using chitosan as crosslinker

Cotton gauzes were grafted with a hydrogel of maltodextrin (MD) and poly(acrylic acid) (PAAc) using N-maleyl chitosan as crosslinker to obtain materials with antimicrobial properties. Reaction parameters including monomer, crosslinker, and initiator concentrations were studied. The modification with the copolymer poly(acrylic acid)-co-maltodextrin (PAAc-co-MD) was corroborated by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The grafted gauzes (gauze-g-(PAAc-co-MD)) were able to load vancomycin and inhibit the growth of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. In addition, the incorporation of chitosan as crosslinker showed a synergistic effect against these bacteria. The prepared gauze-g-(PAAc-co-MD) materials could be used in the biomedical area particularly as antimicrobial wound dressings.

Conductive, Self-Healing, Adhesive, and Antibacterial Hydrogels Based on Lignin/Cellulose for Rapid MRSA-Infected Wound Repairing

The abuse of antibiotics induces the emergence of drug-resistant bacteria, which greatly increases the difficulty of clinical treatment of infected wounds. It is urgent to design a multifunctional wound dressing independent of antibiotics. In this work, we designed multifunctional hydrogels based on lignin and cellulose in natural polymers. Lignin with antioxidant properties could reduce silver nanoparticles in situ and could also be used as a crosslinking agent to construct hydrogels between hydroxypropyl cellulose modified with phenylboric acid by a dynamic borate bond. Hydrogels have excellent properties such as self-healing, shape adaptability, biocompatibility, blood compatibility, antioxidant properties, excellent broad-spectrum antimicrobial properties, good tissue adhesion, and electrical conductivity. The tissue adhesion of hydrogels endows them with an excellent hemostasis property in a rat liver injury model. In vivo experiments demonstrated that hydrogels can maintain a moist healing environment, reduce inflammatory cell infiltration, promote M2 macrophage polarization, accelerate collagen deposition, promote the regeneration of new blood vessels, and significantly speed up the wound healing of methicillin-resistant Staphylococcus aureus (MRSA)-infected wounds. Therefore, these multifunctional hydrogels are an excellent candidate to treat multiple stages of wound healing and have a broad application prospect in the medical field.

Antibacterial, antioxidant and biocompatible nanosized quercetin-PVA xerogel films for wound dressing

Topical use of antimicrobial agents to treat wounds to inhibit bacterial invasion and facilitate wound healing is an effective strategy. In this work, an antibacterial xerogel film for potential applications in wound dressings was developed. First, a natural antibacterial agent, quercetin (Qu), was made into water-soluble quercetin-borate (QuB) nanoparticles by merging a solvent exchange method with the borate esterification reaction. QuB nanoparticles were then employed as the cross-linking agent to achieve gelation of poly(vinyl alcohol) (PVA) to obtain antimicrobial QuB-PVA composite microgels. Furthermore, QuB-PVA microgels were utilized as raw materials to produce xerogel films via an electrospray technique. The as-prepared QuB-PVA xerogel films exhibited excellent bacteriostasis, antioxidation, biocompatibility, self-healing, accelerated skin regeneration and functional restoration, and promoted skin wound healing. The QuB-PVA films significantly facilitated the in vivo healing speed of full-thickness skin wounds compared to commercial dressings. We believe that the present multifunctional QuB-PVA xerogel film is an excellent candidate for the wound dressings.

Starch Solutions Prepared under Different Conditions as Modifiers of Chitosan/Poly(aspartic acid)-Based Hydrogels

Recently, there has been great interest in the application of polysaccharides in the preparation of diverse biomaterials which result from their biocompatibility, biodegradability and biological activity. In this work, the investigations on chitosan/poly(aspartic acid)-based hydrogels modified with starch were described. Firstly, a series of hydrogel matrices was prepared and investigated to characterize their swelling properties, structure via FT-IR spectroscopy, elasticity and tensile strength using the Brookfield texture analyzer as well as their impact on simulated physiological liquids. Hydrogels consisting of chitosan and poly(aspartic acid) in a 2:1 volume ratio were elastic (9% elongation), did not degrade after 30-day incubation in simulated physiological liquids, exhibited a relative biocompatibility towards these liquids and similar swelling in each absorbed medium. This hydrogel matrix was modified with starch wherein two of its form were applied-a solution obtained at an elevated temperature and a suspension obtained at room temperature. Hydrogels modified with hot starch solution showed higher sorption that unmodified materials. This was probably due to the higher starch inclusion (i.e., a larger number of hydrophilic groups able to interact with the adsorbed liquid) when this polysaccharide was given in the form of a hot solution. Hydrogels modified with a cold starch suspension had visible heterogeneous inequalities on their surfaces and this modification led to the obtainment materials with unrepeatable structures which made the analysis of their properties difficult and may have led to misleading conclusions.