High-mechanical strength carboxymethyl chitosan-based hydrogel film for antibacterial wound dressing

Valorization of fishery industry waste: Chitosan extraction and its application in the industry

Waste from the fishing industry is disposed of in soils and oceans, causing environmental damage. However, it is also a source of valuable compounds such as chitin. Although chitin is the second most abundant polymer in nature, its use in industry is limited due to the lack of standardized and scalable extraction methods and its poor solubility. The deacetylation process increases its potential applications by enabling the recovery of chitosan, which is soluble in dilute acidic solutions. Chitosan is a polymer of great importance due to its biocompatible and bioactive properties, which include antimicrobial and antioxidant capabilities. Chitin extraction and its deacetylation to obtain chitosan are typically performed using chemical processes that involve large amounts of strongly acidic and alkaline solutions. To reduce the environmental impact of this process, extraction methods based on biotechnological tools, such as fermentation and chitin deacetylase, as well as emerging technologies, have been proposed. These extraction methods have demonstrated the potential to reduce or even avoid using strong solvents and shorten extraction time, thereby reducing costs. Nevertheless, it is important to address existing gaps in this area, such as the requirements for large-scale implementation and the determination of the stoichiometric ratios for each process. This review highlights the use of biotechnological tools and emerging technologies for chitin extraction and chitosan production. These approaches truly minimize environmental impact, reduce the use of strong solvents, and shorten extraction time. They are a reliable alternative to fishery waste valorization, lowering costs; however, addressing the critical gaps for their large-scale implementation remains challenging.

Surface Molding Hydrogel Film Initiated by ZIF-8 with Ethylene Adsorption Performance for Preserving Perishable Fruits

The quality deterioration of postharvest fruits is greatly influenced by ethylene, leading to food wastage worldwide. Therefore, it is urgent to develop an efficient packaging strategy to reduce ethylene concentration and prolong the shelf life of perishable fruits. In this work, a surface-molding hydrogel film was created using ZIF-8 in combination with carboxymethyl starch (CMS) and carboxymethyl chitosan (CMCS). Specifically, ZIF-8 is first anchored on CMS and then rapidly cross-linked in situ with CMCS, forming ZIF-8@CC on the fruit surface (within 10 s). The perfect tight-fitting effects of ZIF-8@CC were observed on various fruit surfaces with different roughness (Ra: ranges from 102 to 308 nm). ZIF-8@CC could absorb 57.3% endogenous ethylene from bananas, and the interaction mechanism between ethylene and ZIF-8 was studied by molecular dynamics simulations, providing insights into the ethylene adsorption capacity of ZIF-8@CC. Moreover, ZIF-8@CC presented excellent antibacterial properties and achieved satisfactory ultralong preservation effects on both nonclimatic and climatic fruits (12 days for strawberries and 14 days for bananas) at room temperature. Importantly, ZIF-8@CC is easily removed, washed, and degradable. These findings offer an efficient and potential food packing material with multifunctional properties for preserving perishable fruits.

Research progress and application of chitosan dressings in hemostasis: A review

Hemorrhage affects human health, and severe bleeding remains a leading contributor to trauma-related mortality. The speed and effectiveness of the application of hemostatic materials are critical. Conventional hemostatic dressings such as bandages and gauze are gradually being replaced by new types of hemostatic dressings due to their poor hemostatic and antibacterial properties. Chitosan, a biopolymer, is biodegradable and nontoxic and possesses hemostatic and antibacterial properties. Chitosan induces hemostasis through direct contact with red corpuscles and platelets, independent of the coagulation pathways of the host, rendering it an optimal hemostatic dressing. It is widely used in wound care, particularly to stop bleeding, promote wound healing, and provide antimicrobial properties. This article reviews the recent research and development of chitosan-based hemostatic dressings, focusing on trauma hemostasis, burn hemostasis, diabetic skin ulcer hemostasis and other aspects. It also emphasizes the significance of chitosan dressings in wound hemostasis and healing, identifies their research opportunities in hemostasis and wound healing, and explores new research directions.

Sodium carboxymethyl cellulose hydrogels containing montmorillonite-NaClO2 for postharvest preservation of Chinese bayberries

Owing to their lack of outer skin, Chinese bayberries are highly susceptible to mechanical damage during picking, which accelerates bacterial invasion and rotting, shortening their shelf life. In this study, montmorillonite (MMT) was used to absorb an aqueous sodium chlorite solution embedded in a carboxymethyl cellulose sodium hydrogel after freeze drying, and the hydrogel was crosslinked by Al3+ ions. Al3+ hydrolyzed to produce H+, creating an acidic environment within the hydrogel and reacting with NaClO2 to slowly release ClO2. We prepared a ClO2 slow-release hydrogel gasket with 0.5 wt% MMT-NaClO2 and investigated its storage effect on postharvest Chinese bayberries. Its inhibition rates against Escherichia coli and Listeria monocytogenes were 98.84% and 98.96%, respectively. The results showed that the gasket preserved the appearance and nutritional properties of the berries. The antibacterial hydrogel reduced hardness loss by 26.57% and ascorbic acid loss by 46.36%. This new storage method could also be applicable to other fruits and vegetables.

Antimicrobial Effect of Waterborne Polyurethane-Based Cellulose Nanofibril/Silver Nanoparticles Composites and Acacia concinna (Willd.) DC Extract (Shikakai)

Antimicrobial coatings are becoming increasingly popular in functional material modification and are essential in addressing microbial infection challenges. In this study, the phytochemical and antimicrobial potential of aqueous, 80% methanol and 80% ethanol pod extracts of Acacia concinna (Willd.) DC (AC) and its application in the green in situ (one pot) synthesis of silver nanoparticles on Cellulose nano fibrils (CNF) and Waterborne polyurethane (WPU) were prepared. The phytochemical evaluation of Acacia concinna crude extracts showed the presence of alkaloids, flavonoids, phenols, tannins, terpenoids, saponins, steroids. The surface plasmon Resonance peak of CNF/AC-AgNPs was 450 nm and the FTIR result confirmed functional groups such as carbonyl, phenols and carboxyl were present which was important for the bio-reduction of silver nanoparticles. The crude AC aqueous pods extract against Gram-positive and Gram-negative bacteria compared with AC ethanol and AC methanol extracts. The WPU/CNF/AC-AgNPs composite dispersion was also good in terms of its antibacterial activities. The WPU/CNF/AC-AgNPs nanocomposites could be applied as bifunctional nanofillers as an antimicrobial agent in food packaging systems and other biological applications.

Carboxymethyl chitosan nanoparticle-modulated cationic hydrogels doped with copper ions for combating bacteria and facilitating wound healing

The simultaneous administration of antibacterial treatment and acceleration of tissue regeneration are crucial for the effective healing of infected wounds. In this work, we developed a facile hydrogel (PCC hydrogel) through coordination and hydrogen interactions by polymerizing acrylamide monomers in the presence of carboxymethyl chitosan nanoparticles and copper ions. The prepared PCC hydrogel demonstrated effective bacterial capture from wound exudation and exhibited a potent bactericidal activity against methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. Furthermore, slow release of copper ions from the hydrogel facilitated wound healing by promoting cell migration, collagen deposition and angiogenesis. Additionally, the PCC hydrogel possessed excellent biocompatibility and hemostatic properties. The practical effectiveness of PCC hydrogel in addressing bacterial infections and facilitating wound healing was verified using a mouse model of MRSA-induced wound infections. Overall, this work presents a simple yet efficient multifunctional hydrogel platform that integrates antibacterial activity, promotion of wound healing, and hemostasis for managing bacteria-associated wounds.

Medical Applications and Cellular Mechanisms of Action of Carboxymethyl Chitosan Hydrogels

Carboxymethyl chitosan (CMCS) hydrogels have been investigated in biomedical research because of their versatile properties that make them suitable for various medical applications. Key properties that are especially valuable for biomedical use include biocompatibility, tailored solid-like mechanical characteristics, biodegradability, antibacterial activity, moisture retention, and pH stimuli-sensitive swelling. These features offer advantages such as enhanced healing, promotion of granulation tissue formation, and facilitation of neutrophil migration. As a result, CMCS hydrogels are favorable materials for applications in biopharmaceuticals, drug delivery systems, wound healing, tissue engineering, and more. Understanding the interactions between CMCS hydrogels and biological systems, with a focus on their influence on cellular behavior, is crucial for leveraging their versatility. Because of the constantly growing interest in chitosan and its derivative hydrogels in biomedical research and applications, the present review aims to provide updated insights into the potential medical applications of CMCS based on recent findings. Additionally, we comprehensively elucidated the cellular mechanisms underlying the actions of these hydrogels in medical settings. In summary, this paper recapitulates valuable data gathered from the current literature, offering perspectives for further development and utilization of carboxymethyl hydrogels in various medical contexts.

Injectable Silver Nanoparticle-Based Hydrogel Dressings with Rapid Shape Adaptability and Antimicrobial Activity

Burns and scalds often result in deep wounds that challenge adequate debridement and inflammation control using traditional sheet-like hydrogel dressings. Herein, we developed an antibacterial, injectable, and self-healing hydrogel (ADCM@Ag) by employing carboxymethyl chitosan (CMCS) for in situ green reduction of silver ions and utilizing a spontaneous Schiff base reaction with aldehyde-functionalized dextran (AD). SEM analysis revealed a porous structure within the hydrogel. Swelling and enzymatic degradation assays demonstrated that ADCM@Ag hydrogel possesses excellent fluid absorption capacity and biodegradability. Mechanical tests indicated good mechanical properties, allowing the hydrogel to withstand external forces when applied to animal wounds. The hydrogel exhibited good injectability, shape adaptability, and self-healing capability. Cell experiments showed that the ADCM@Ag hydrogel avoided the cytotoxicity caused by high concentrations of silver ions and had good cell compatibility. Antimicrobial assays showed that ADCM@Ag exhibited potent bactericidal effects against Gram-negative and Gram-positive bacteria, achieving at least 85% killing efficacy. Collectively, ADCM@Ag hydrogel has good potential for wound dressing applications.

A Microenvironment-Responsive, Controlled Release Hydrogel Delivering Embelin to Promote Bone Repair of Periodontitis via Anti-Infection and Osteo-Immune Modulation

Periodontitis, a prevalent chronic inflammatory disease, poses significant challenges for effective treatment due to its complex etiology involving specific bacteria and the inflammatory immune microenvironment. Here, this study presents a novel approach for the targeted treatment of periodontitis utilizing the immunomodulatory and antibacterial properties of Embelin, a plant-derived compound, within an injectable hydrogel system. The developed Carboxymethyl Chitosan-Oxidized Dextran (CMCS-OD) hydrogel formed via dynamic chemical bonds exhibited self-healing capabilities and pH-responsive behavior, thereby facilitating the controlled release of Embelin and enhancing its efficacy in a dynamic oral periodontitis microenvironment. This study demonstrates that this hydrogel system effectively prevents bacterial invasion and mitigates excessive immune response activation. Moreover, it precisely modulates macrophage M1/M2 phenotypes and suppresses inflammatory cytokine expression, thereby fostering a conducive environment for bone regeneration and addressing periodontitis-induced bone loss. These findings highlight the potential of the approach as a promising strategy for the clinical management of periodontitis-induced bone destruction.

Methacrylated Carboxymethyl Chitosan Scaffold Containing Icariin-Loaded Short Fibers for Antibacterial, Hemostasis, and Bone Regeneration

Bone defects typically result in bone nonunion, delayed or nonhealing, and localized dysfunction, and commonly used clinical treatments (i.e., autologous and allogeneic grafts) have limited results. The multifunctional bone tissue engineering scaffold provides a new treatment for the repair of bone defects. Herein, a three-dimensional porous composite scaffold with stable mechanical support, effective antibacterial and hemostasis properties, and the ability to promote the rapid repair of bone defects was synthesized using methacrylated carboxymethyl chitosan and icariin-loaded poly-l-lactide/gelatin short fibers (M-CMCS-SFs). Icariin-loaded SFs in the M-CMCS scaffold resulted in the sustained release of osteogenic agents, which was beneficial for mechanical reinforcement. Both the porous structure and the use of chitosan facilitate the effective absorption of blood and fluid exudates. Moreover, its superior antibacterial properties could prevent the occurrence of inflammation and infection. When cultured with bone mesenchymal stem cells, the composite scaffold showed a promotion in osteogenic differentiation. Taken together, such a multifunctional composite scaffold showed comprehensive performance in antibacterial, hemostasis, and bone regeneration, thus holding promising potential in the repair of bone defects and related medical treatments.

A 3D bioprinted antibacterial hydrogel dressing of gelatin/sodium alginate loaded with ciprofloxacin hydrochloride

Skin plays a crucial role in human physiological functions, however, it was vulnerable to bacterial infection which delayed wound healing. Nowadays, designing an individual wound dressing with good biocompatibility and sustaining anti-infection capability for healing of chronic wounds are still challenging. In this study, various concentrations of the ciprofloxacin (CIP) were mixed with gelatine (Gel)/sodium alginate (SA) solution to prepare Gel/SA/CIP (GAC) bioinks, following the fabrication of GAC scaffold by an extrusion 3D bioprinting technology. The results showed that the GAC bioinks had good printability and the printed GAC scaffolds double-crosslinked by EDC/NHS and CaCl2 had rich porous structure with appropriate pore size, which were conducive to drug release and cell growth. It demonstrated that the CIP could be rapidly released by 70% in 5 min, which endowed the GAC composite scaffolds with an excellent antibacterial ability. Especially, the antibacterial activities of GAC7.5 against Escherichia coli and Staphylococcus aureus within 24 h were even close to 100%, and the inhibition zones were still maintained 14.78 ± 0.40 mm and 14.78 ± 0.40 mm, respectively, after 24 h. Meanwhile, GAC7.5 also demonstrated impressive biocompatibility which can promote the growth and migration of L929 and accelerate wound healing. Overall, the GAC7.5 3D bioprinting scaffold could be used as a potential skin dressing for susceptible wounds with excellent antibacterial activity and good biocompatibility to meet urgent clinical needs.

A multifunctional chitosan based porous membrane for pH-responsive antibacterial activity and promotion of infected wound healing

Unsatisfactory mechanical and antibacterial properties restricted the solo use of chitosan (CS) as a wound dressing. In this work, a novel CS/hydroxyapatite/ZIF-8 (CS/HAp/ZIF-8, CHZ-10) porous membrane was facilely constructed by in situ loading of ZIF-8 on CS/HAp. The advantages of the three compositions were rationally integrated, and the multifunctionality and practicality of this CS-based dressing were improved. HAp not only improved the mechanical strength and stability of CS, but also promoted cell proliferation and accelerated hemostasis with its released Ca2+. Meanwhile, ZIF-8 enhanced the antibacterial activity of CS by releasing antibacterial Zn2+ in a pH-responsive and sustainable manner, avoiding the bio-accumulation toxicity of heavy metals. Compared with CS/HAp and conventionally used gauze, CHZ-10 exhibited superior coagulation and hemolytic ability, as well as outstanding antibacterial activity against E. coli and S. aureus. Besides, both in vivo observation and histological evaluation demonstrated that CHZ-10 could not only effectively inhibit bacterial infection and reduce inflammation of the wound, but also promote its re-epithelialization, granulation, tissue formation and collagen fibre growth, leading to effectively enhanced wound-healing. This work provides a new method for the easy construction of multifunctional antibacterial dressings based on CS, showing promise for application in clinical wound care.

Fast Self-Healing Hyaluronic Acid Hydrogel with a Double-Dynamic Network for Skin Wound Repair

Developing extracellular matrix-derived hydrogel with a fast self-healing capacity to provide a sustainable moist environment able to accelerate wound healing is highly desired for full-thickness skin wound repair. In this study, a fast self-healing hyaluronic acid hydrogel with a dual dynamic network was constructed through a primary reversible acylhydrazone bond formed between aldehyde-modified hyaluronic acid, 3,3'-dithiobis (propionyl hydrazide) (DTP), and secondary dynamic ionic interactions between κ-carrageenan (KC) and K+. Because of the presence of various dynamic covalent bonds such as the acylhydrazone bond, disulfide bond, and noncovalent bonds including hydrogen bonding and ionic interactions, as well as the notable thermoreversible nature of KC, the resultant hydrogel could be self-healed rapidly within 30 min under physiological temperature with a self-healing efficiency of 100%, which was significantly better than other hyaluronic acid hydrogels, as reported previously. Besides, the hydrogel displayed excellent cytocompatibility. According to this study, the hydrogel was administered into the wounds and achieved a superior performance of promoting full-thickness skin wound healing by increasing granulation tissue formation, deposition of collagen as well as the acceleration of re-epithelialization and neovascularization, compared to commercial products, e.g., gauze and 3 M hydrocolloid. We also anticipate that this strategy of double-dynamic network cross-linking can be adopted to fabricate self-healing materials for multiple applications.

Recent Applications of Chitosan and Its Derivatives in Antibacterial, Anticancer, Wound Healing, and Tissue Engineering Fields

Chitosan, a versatile biopolymer derived from chitin, has garnered significant attention in various biomedical applications due to its unique properties, such as biocompatibility, biodegradability, and mucoadhesiveness. This review provides an overview of the diverse applications of chitosan and its derivatives in the antibacterial, anticancer, wound healing, and tissue engineering fields. In antibacterial applications, chitosan exhibits potent antimicrobial properties by disrupting microbial membranes and DNA, making it a promising natural preservative and agent against bacterial infections. Its role in cancer therapy involves the development of chitosan-based nanocarriers for targeted drug delivery, enhancing therapeutic efficacy while minimising side effects. Chitosan also plays a crucial role in wound healing by promoting cell proliferation, angiogenesis, and regulating inflammatory responses. Additionally, chitosan serves as a multifunctional scaffold in tissue engineering, facilitating the regeneration of diverse tissues such as cartilage, bone, and neural tissue by promoting cell adhesion and proliferation. The extensive range of applications for chitosan in pharmaceutical and biomedical sciences is not only highlighted by the comprehensive scope of this review, but it also establishes it as a fundamental component for forthcoming research in biomedicine.

Investigation of the Effects of Phenolic Extracts Obtained from Agro-Industrial Food Wastes on Gelatin Modification

In this study, modified bovine gelatin was produced using the alkaline technique with four different oxidized agro-industrial food waste (pomegranate peel (PP), grape pomace and seed (GP), black tea (BT), and green tea (GT)) phenolic extracts (AFWEs) at three different concentrations (1, 3, and 5% based on dry gelatin). The effect of waste type and concentration on the textural, rheological, emulsifying, foaming, swelling, and color properties of gelatin, as well as its total phenolic content and antioxidant activity, was investigated. Significant improvement in gel strength, thermal stability, and gelation rate of gelatin was achieved by modification with oxidized agro-industrial waste extracts. Compared to the control sample, 46.24% higher bloom strength in the GT5 sample, 5.29 and 6.01 °C higher gelling and melting temperatures in the PP5 sample, respectively, and 85.70% lower tmodel value in the GT3 sample were observed. Additionally, the total phenolic content, antioxidant activity, foam, and emulsion properties of the modified gels increased significantly. This study revealed that gelatins with improved technological and functional properties can be produced by using oxidized phenolic extracts obtained from agricultural industrial food wastes as cross-linking agents in the modification of gelatin.

MOF/MXene-loaded PVA/chitosan hydrogel with antimicrobial effect and wound healing promotion under electrical stimulation and improved mechanical properties

Electrical stimulation modulates cell behavior and influences bacterial activity, so highly conductive, antimicrobial hydrogels are suitable for promoting wound healing. In this study, highly conductive and antimicrobial Ti3C2Tx (MXene) hydrogels composed of chitosan and poly(vinyl alcohol) and AgCu- H2PYDC MOF were developed. In PVACS/MOF/MXene (PCMM) hydrogels, the MXene layer acts as an electrical conductor. The electrical conductivity is 0.61 ± 0.01 S·cm-1. PCMM hydrogels modulate cell behavior and provide ES antimicrobial capacity under ES at 1 V. The metal ions of MOF form coordination with chitosan molecules and increase the cross-linking density between chitosan molecules, thus improving the mechanical properties of the hydrogel (tensile strength 0.088 ± 0.04 MPa, elongation at break 233 ± 11 %). The PCMM gels had good biocompatibility. The PCMM hydrogels achieved 100 % antibacterial activity against E. coli and S. aureus for 12 h. 1 V electrical stimulation of PCMM hydrogel accelerated the wound healing process in mice by promoting cell migration and neovascularization, achieving 97 ± 0.4 % wound healing on day 14. The hydrogel dressing PCMM-0.1 with MOF addition of 0.1 % had the best wound healing promoting effect and which is a promising dressing for promoting wound healing and is a therapeutic strategy worth developing.

Double network self-healing hydrogels based on carboxyethyl chitosan/oxidized sodium alginate/Ca2+: Preparation, characterization and application in dye absorption

This paper presents the formation of a self-healing hydrogel prepared by carboxyethyl modification of chitosan and crosslinking with oxidized sodium alginate. Concurrently, the incorporation of Ca2+ facilitated the formation of "calcium bridges" through intricate coordination with carboxyl moieties, bolstering the attributes of the hydrogel. Various characterization methods, including scanning electron microscopy, texture analysis, and rheological measurements, demonstrated that the introduction of carboxyethyl groups resulted in a more compact hydrogel network structure and improved the hardness and elasticity. The addition of Ca2+ helped to further enhance the mechanical performance of the hydrogel and increase its thermal stability. Then, the adsorption capacity was also investigated, showing adsorption capacities of 46.17 mg/g methylene blue and 46.44 mg/g congo red for carboxyethyl chitosan/oxidized sodium alginate hydrogel, a four-fold increase for congo red versus chitosan/oxidized sodium alginate hydrogel. In addition, the adsorption behavior of CEC/OSA/2%Ca2+ hydrogel can be well described by pseudo-second-order kinetic model and Langmuir adsorption isothermal model. Compared to traditional hydrogels, CEC/OSA/2%Ca2+ hydrogel shows superior mechanical strength, enhanced thermal stability, and improved adsorption capacity, which can effectively adsorb not only methylene blue but also congo red. These advancements demonstrate our hydrogel's innovative properties.

High-Strength, High-Swelling-Resistant, High-Sensitivity Hydrogel Sensor Prepared with Wood That Retains Lignin

Wood-derived hydrogels possess satisfactory longitudinal strength but lack excellent swelling resistance and dry shrinkage resistance when achieving high anisotropy. In this study, we displayed the preparation of highly dimensional stable wood/polyacrylamide hydrogels (wood/PAM-Al3+). The alkali-treated wood retains lignin as the skeleton of the hydrogel. Second, Al ions were added to the metal coordination with lignin. Finally, by employing free radical polymerization, we construct a conductive electronic network using polyaniline within the wood/PAM-Al3+ matrix to create the flexible sensor. This approach leverages lignin's integrated structure within the middle lamella to provide enhanced swelling resistance and stronger binding strength in the transverse direction. Furthermore, coordination between lignin and Al ions improves the mechanical strength of the wood hydrogel. Polyaniline provides stable linear pressure and temperature responses. The wood/PAM-Al3+ exhibits a transverse swelling ratio of 3.90% while achieving a longitudinal tensile strength of 20.5 MPa. This high-strength and high-stability sensor is capable of monitoring macroscale human behavior. Therefore, this study presents a simple yet innovative strategy for constructing tough hydrogels while also establishing an alternative pathway for exploring lignin networks in new functional materials development.

Preparation and evaluation of blend polymer films for wound dressing using vancomycin-loaded polycaprolactone and carboxymethyl cellulose via crosslinking methods: Effect of mechanical strength, antibacterial activity, and cytotoxicity

Polycaprolactone (PCL) and carboxymethyl cellulose (CMC) are two materials with beneficial properties for wound healing applications. Here, the simple preparation of PCL/CMC polymer films via the crosslinking method was demonstrated for the first time. The polymer films represented the suitable properties of liquid absorption and tensile strength to be used as a wound dressing. The blend polymer films can also load the vancomycin, which prolongs the drug release for effectiveness against S. aureus. The trifluoroethanol showed less toxicity in comparison with other crosslinking agents. This process can also be applied further in other medical devices and wound healing applications.

Preparation Strategies, Functional Regulation, and Applications of Multifunctional Nanomaterials-Based DNA Hydrogels

With the extensive attention of DNA hydrogels in biomedicine, biomaterial, and other research fields, more and more functional DNA hydrogels have emerged to match the various needs. Incorporating nanomaterials into the hydrogel network is an emerging strategy for functional DNA hydrogel construction. Surprisingly, nanomaterials-based DNA hydrogels can be engineered to possess favorable properties, such as dynamic mechanical properties, excellent optical properties, particular electrical properties, perfect encapsulation properties, improved magnetic properties, and enhanced antibacterial properties. Herein, the preparation strategies of nanomaterials-based DNA hydrogels are first highlighted and then different nanomaterial designs are used to demonstrate the functional regulation of DNA hydrogels to achieve specific properties. Subsequently, representative applications in biosensing, drug delivery, cell culture, and environmental protection are introduced with some selected examples. Finally, the current challenges and prospects are elaborated. The study envisions that this review will provide an insightful perspective for the further development of functional DNA hydrogels.

Recent advances of chitosan as a hemostatic material: Hemostatic mechanism, material design and prospective application

Uncontrolled hemorrhage arising from surgery or trauma may cause morbidity and even mortality. Therefore, facilitating control of severe bleeding is imperative for health care worldwide. Among diverse hemostatic materials, chitosan (CS) is becoming the most promising material owing to its non-toxic feature, as well as inherently hemostatic performance. However, further enhancing hemostatic property of CS-based materials without compromising more beneficial functions remains a challenge. In this review, representative hemostatic mechanisms of CS-based materials are firstly discussed in detail, mostly including red blood cells (RBCs) aggregation, platelet adherence and aggregation, as well as interaction with plasma proteins. Also, various forms (involving powder/particle, sponge, hydrogel, nanofiber, and other forms) of CS-based hemostatic materials are systematically summarized, mainly focusing on their design and preparation, characteristics, and comparative analysis of various forms. In addition, varied hemostatic applications are described in detail, such as skin wound hemostasis, liver hemostasis, artery hemostasis, and heart hemostasis. Finally, current challenges and future directions of functional design of CS-based hemostatic materials in diverse hemostatic applications are proposed to inspire more intensive researches.

A chitosan-based antibacterial hydrogel with injectable and self-healing capabilities

The presence of bacteria directly affects wound healing. Chitosan-based hydrogel biomaterials are a solution as they offer advantages for wound-healing applications due to their strong antimicrobial properties. Here, a double-cross-linking chitosan-based hydrogel with antibacterial, self-healing, and injectable properties is reported. Thiolated chitosan was successfully prepared, and the thiolated chitosan molecules were cross-linked by Ag-S coordination to form a supramolecular hydrogel. Subsequently, the amine groups in the thiolated chitosan covalently cross-linked with genipin to further promote hydrogel formation. In vitro experimental results indicate that hydrogel can release Ag+ over an extended time, achieving an antibacterial rate of over 99% against Escherichia coli and Staphylococcus aureus. Due to the reversible and dynamic feature of Ag-S coordination, an antibacterial hydrogel exhibited injectable and self-healing capabilities. Additionally, the hydrogel showed excellent biocompatibility and biodegradability.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-023-00211-z.

All-Natural Injectable Antibacterial Hydrogel Enabled by Chitosan and Borneol

Hydrogels with intrinsic antimicrobial capabilities based on natural strategies have been studied as a hot topic in biomedicine. Nevertheless, it is highly challenging to thoroughly develop a bacteriostatic natural hydrogel. Borneol as a traditional Chinese medicine possesses a unique broad-spectrum antibacterial activity under a membrane-breaking mechanism. In this study, a range of fully natural antibacterial hydrogels are designed and synthesized via the Schiff base cross-linking of carboxymethyl chitosan and dialdehyde dextran grafted natural borneol. The borneol with three configurations is hydrophilically modified onto dextran to boost its antibacterial activity. Also, the synergism of hydrophilic-modified borneol groups and positively charged ammonium ions of carboxymethyl chitosan make the hydrogels totally constrict the E. coli and S. aureus growth during 24 h. Furthermore, the hydrogels exhibit good in vitro cytocompatibility through cytotoxicity, protein adhesion, and hemolytic tests. In view of the injectability, the hydrogels can be delivered to the target site through a minimally invasive route. In short, this work offers a potential tactic to develop antibacterial hydrogels for the treatment of topical wound infections.

An Insight into Biodegradable Polymers and their Biomedical Applications for Wound Healing

Biodegradable polymers, encompassing both natural and synthetic polymers, have demonstrated efficacy as carriers for synthetic drugs, natural bioactive molecules, and inorganic metals. This is due to their ability to control the release of these substances. As a result, various advanced materials, such as nanoparticle- loaded hydrogels, nanofibrous scaffolds, and nanocomposites, have been developed. These materials have shown promise in enhancing processes, such as cell proliferation, vascular angiogenesis, hair growth, and wound healing management. Natural polymers, including hyaluronic acid, collagen, chitosan, gelatin, and alginate, as well as synthetic polymers like polylactic acid, polyglycolic acid, polylactic co-glycolic acid, and PCA, have significant potential for promoting wound healing. This study examines the advancements in biodegradable polymers for wound healing, specifically focusing on each polymer and its distinctive formulations. It also discusses the in vitro experiments conducted using different cell lines, as well as the in vivo studies that explore the numerous uses of these polymers in wound healing. The discussion also included the exploration of modifications or combinations of several polymers, as well as surface changes, in order to produce synergistic effects and address the limitations of individual polymers. The goal was to expedite the healing process of different chronic wounds. Due to this, there have been notable advancements in the technological use of polymeric mixes, including biodegradable polymer-based scaffolds, which have accelerated the process of wound healing.

Effect of Curcumin-containing Nanofibrous Gelatin-hydroxyapatite Scaffold on Proliferation and Early Osteogenic Differentiation of Dental Pulp Stem Cells

BACKGROUND

In recent years, the electrospinning method has received attention because of its usage in producing a mimetic nanocomposite scaffold for tissue regeneration. Hydroxyapatite and gelatin are suitable materials for producing scaffolds, and curcumin has the osteogenesis induction effect.

AIMS

This study aimed to evaluate the toxicity and early osteogenic differentiation stimulation of nanofibrous gelatin-hydroxyapatite scaffold containing curcumin on dental pulp stem cells (DPSCs).

OBJECTIVE

The objective of the present investigation was the evaluation of the proliferative effect and primary osteogenic stimulation of DPSCs with a nanofibrous gelatin-hydroxyapatite scaffold containing curcumin. Hydroxyapatite and gelatin were used as suitable and biocompatible materials to make a scaffold suitable for stimulating osteogenesis. Curcumin was added to the scaffold as an osteogenic differentiation- enhancing agent.

METHODS

The effect of nano-scaffold on the proliferation of DPSCs was evaluated. The activity of alkaline phosphatase (ALP) as the early osteogenic marker was considered to assess primary osteogenesis stimulation in DPSCs.

RESULTS

The nanofibrous gelatin-hydroxyapatite scaffold containing curcumin significantly increased the proliferation and the ALP activity of DPSCs (P<0.05). The proliferative effect was insignificant in the first 2 days, but the scaffold increased cell proliferation by more than 40% in the fourth and sixth days. The prepared scaffold increased the activity of the ALP of DPSCs by 60% compared with the control after 14 days (p<0.05).

CONCLUSION

The produced nanofibrous gelatin-hydroxyapatite scaffold containing curcumin can be utilized as a potential candidate in tissue engineering and regeneration of bone and tooth.

FUTURE PROSPECTS

The prepared scaffold in the present study could be a beneficial biomaterial for tissue engineering and the regeneration of bone and tooth soon.

Synthesis of organic-solvent-soluble cellulose and preparation of fluorescent polyurethanes for the detection and removal of Hg+ ions

Modifying cellulose to obtain materials with favorable processing properties and functions is highly significant, especially, for the detection and removal of heavy metal ions. In this study, fluorescent cellulose-based polyurethane (PU) films containing naphthalimide fluorophore were synthesized and could use for the convenient detection and removal of Hg+ ions. Firstly, the microcrystalline cellulose was treated with SOCl2 to convert some -OH groups into -Cl. Simultaneously, a naphthalimide derivative (NAN) with -NH- groups was synthesized. Subsequently, a fluorescent cellulose-based probe (Cel-NAN) was prepared by utilizing the substitution reaction between -Cl on cellulose and -NH- on NAN. Finally, two cellulose-based fluorescent PU films (Cel-NAN-PU1 and Cel-NAN-PU2) were successfully synthesized by reacting the unreacted -OH groups on Cel-NAN with PEG-1000 and HDI/IPDI. These as-prepared PU films could serve as portable fluorescence test papers to Hg+ ions in aqueous solutions. Upon contact with Hg+ ions, the fluorescence was quenched, acting as a "turn-off" probe. Simultaneously, these films could serve as adsorbents for the removal of Hg+ ions from aqueous systems. Cel-NAN-PU1 film exhibited a removal efficiency over 80 % and an adsorption capacity of 8.4 mg·cm-2 for Hg+. These cellulose-based fluorescent PU films possess promising potential in the field of mercury pollution control.

Review on chitosan-based antibacterial hydrogels: Preparation, mechanisms, and applications

Chitosan (CS) is known for its remarkable properties, such as good biocompatibility, biodegradability, and renewability, in addition to its antibacterial and biological activities. However, as CS is insoluble in water, it displays limited antibacterial performance under neutral and physiological conditions. A viable solution to this problem is grafting chemically modified groups onto the CS framework, thereby increasing its solubility and enhancing its antibacterial effect. Herein, the antibacterial action mechanism of CS and its derivatives is reviewed, confirming the prevalent use of composite materials comprising CS and its derivatives as an antibacterial agent. Generally, the antimicrobial ability of CS-based biomaterials can be enhanced by incorporating supplementary polymers and antimicrobial agents. Research on CS-based composite biomaterials is ongoing and numerous types of biomaterials have been reported, including inorganic nanoparticles, antibacterial agents, and CS derivatives. The development of these composite materials has considerably expanded the application of CS-based antibacterial materials. This study reviews the latest progress in research regarding CS-based composite hydrogels for wound repair, tissue engineering, drug release, water purification, and three-dimensional printing applications. Finally, the summary and future outlook of CS-based antibacterial hydrogels are presented in anticipation of a broader range of applications of CS-based antibacterial hydrogels.

Bletilla Striata polysaccharides thermosensitive gel for photothermal treatment of bacterial infection

Skin is the most important defense shield which touched external environment directly. Effectively clearing microbes in infected wound via non-antibiotic therapy is crucial for the promotion of recovery in complex biological environments, and the wound healing is a crucial process after sterilization to avoid superinfection. Herein, a kind of Prussian blue-based photothermal responsive gel, Bletilla striata polysaccharide-mingled, isatin-functionalized Prussian blue gel (PB-ISA/BSP gel) was reported for effective treatment of bacterial infection and wound healing. The introduction of effective components of traditional Chinese medicine (TCM), isatin (ISA), enhanced the efficiency of sterilization synergistically. Furthermore, the process of wound healing was promoted by Bletilla striata polysaccharides (BSP). PB-ISA@BSP had a considerable antibacterial rate with 98.5 % under an 808 nm laser for 10 min in vitro. Besides, PB-ISA/BSP gel showed an effective antibacterial efficacy in vivo and a fast wound healing rate as well. The as-prepared functional particles can invade and destroy bacteria membrane to kill microbes. This work highlights that PB-ISA/BSP gel is a promising antibacterial agent based on synergistically enhanced photothermal effect and wound healing promotion ability and provides inspiration for future therapy based on the synergy between photothermal agent and active components in TCM.

Carboxymethyl chitosan-gelatin-mesoporous silica nanoparticles containing Myrtus communis L. extract as a novel transparent film wound dressing

Wound healing and health care requirements have attracted more attention, and the need to develop new drug-containing dressings to accelerate wound healing is required. Carboxymethyl chitosan (CMCS)/gelatin-based films with mesoporous silica nanoparticles (MSNs) containing the Myrtus communis L. (Myrtle) aqueous extract were designed to answer this demand. Myrtle aqueous extract included total phenolic content and good free radical scavenging ability in vitro assay. The infrared spectroscopy characterized the functional groups of myrtle extract and biocomposite films. It was found that mesoporous silica nanoparticles increased the tensile strength of the flexible dressings, which is essential in therapeutic uses. MSNs influenced swelling ratio, oxygen, and water vapor permeability that indicates the CMCS/Gelatin/Myrtle/5 % MSNs wound dressing can absorb wound exudates and preserve skin moisture. Also, these biocompatible nanoparticles reduced the cytotoxicity of fibroblast cells due to the decelerated drug release. Correspondingly, silica nanoparticles affected the extract release rate and could accumulate and release the extract prolonged in CMCS/Gelatin/Myrtle/5 % MSNs models. Finally, histological analysis showed collagen growth and fibroblast migration in wounds treated with CMCS/Gelatin/Myrtle/5 % MSNs, causing proper wound contraction and accelerating wound healing in mice models. The results suggest that CMCS/Gelatin/Myrtle/5 % MSNs films have a beneficial application as wound dressings.

Jute Stick-Derived Cellulose-Based Hydrogel: Synthesis, Characterization, and Methylene Blue Removal from Aqueous Solution

In this work, microcrystalline cellulose (MCC) was isolated from jute sticks and sodium carboxymethyl cellulose (Na-CMC) was synthesized from the isolated MCC. Na-CMC is an anionic derivative of microcrystalline cellulose. The microcrystalline cellulose-based hydrogel (MCCH) and Na-CMC-based hydrogel (Na-CMCH) were prepared by using epichlorohydrin (ECH) as a crosslinker by a chemical crosslinking method. The isolated MCC, synthesized Na-CMC, and corresponding hydrogels were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electronic microscopy (SEM), and energy dispersive spectroscopy (EDS) for functional groups, crystallinity, surface morphology, and composite elemental composition, respectively. Pseudo-first-order, pseudo-second-order, and Elovich models were used to investigate the adsorption kinetics. The pseudo-second-order one is favorable for both hydrogels. Freundlich, Langmuir, and Temkin adsorption isotherm models were investigated. MCCH follows the Freundlich model (R2 = 0.9967), and Na-CMCH follows the Langmuir isotherm model (R2 = 0.9974). The methylene blue (MB) dye adsorption capacities of ionic (Na-CMCH) and nonionic (MCCH) hydrogels in different contact times (up to 600 min), initial concentrations (10-50 ppm), and temperatures (298-318 K) were investigated and compared. The maximum adsorption capacity of MCCH and Na-CMCH was 23.73 and 196.46 mg/g, respectively, and the removal efficiency of MB was determined to be 26.93% for MCCH and 58.73% for Na-CMCH. The Na-CMCH efficiently removed the MB from aqueous solutions as well as spiked industrial wastewater. The Na-CMCH also remarkably efficiently reduced priority metal ions from an industrial effluent. An effort has been made to utilize inexpensive, readily available, and environmentally friendly waste materials (jute sticks) to synthesize valuable adsorbent materials.

An underwater stable and durable gelatin composite hydrogel coating for biomedical applications

Developing underwater stable and durable hydrogel coatings with drag-reducing, drug release, and antibacterial properties is essential for lots of biomedical applications. However, most hydrogel coatings cannot meet the requirement of underwater stability and versatility, which severely limits their widespread use. In this work, an underwater stable, durable and substrate-independent gelatin composite hydrogel (GMP) coating is developed through covalent crosslinks, where a silane coupling agent with an unsaturated double bond is grafted onto a substrate of co-deposited polydopamine and polyethylenimine. GMP coating can be easily coated onto various medical device surfaces, such as artificial joints, catheters, tracheal tubes and titanium alloys, showing excellent structural stability and mechanical tunability under extreme conditions of ultrasonic treatment for 1 h (400 W of ultrasonic power) or underwater shearing for 14 days (400 rpm). Besides, friction experiment reveals that GMP coating exhibits good lubrication properties (coefficient of friction < 0.003). The drug-loading and bacterial inhibition ring tests show that the GMP coating has a tunable drug release ability with the final releasing ratios of 70-95% by changing the content of poly (ethylene glycol) diacrylate. This work offers a scalable approach of fabricating bio-functional and stable hydrogel coatings, which can be potentially used in biomedical applications.

Recent advances in chitosan-based materials; The synthesis, modifications and biomedical applications

The attention to polymer-based biomaterials, for instance, chitosan and its derivatives, as well as the techniques for using them in numerous scientific domains, is continuously rising. Chitosan is a decomposable naturally occurring polymeric material that is mostly obtained from seafood waste. Because of its special ecofriendly, biocompatible, non- toxic nature as well as antimicrobial properties, chitosan-based materials have received a lot of interest in the field of biomedical applications. The reactivity of chitosan is mainly because of the amino and hydroxyl groups in its composition, which makes it further fascinating for various uses, including biosensing, textile finishing, antimicrobial wound dressing, tissue engineering, bioimaging, gene, DNA and drug delivery and as a coating material for medical implants. This study is an overview of the different types of chitosan-based materials which now a days have been fabricated by applying different techniques and modifications that include etherification, esterification, crosslinking, graft copolymerization and o-acetylation etc. for hydroxyl groups' processes and acetylation, quaternization, Schiff's base reaction, and grafting for amino groups' reactions. Furthermore, this overview summarizes the literature from recent years related to the important applications of chitosan-based materials (i.e., thin films, nanocomposites or nanoparticles, sponges and hydrogels) in different biomedical applications.

Engineering of PVA/PVP Hydrogels for Agricultural Applications

Hydrogels have gained significant popularity in agricultural applications in terms of minimizing waste and mitigating the negative environmental impact of agrochemicals. This review specifically examines the utilization of environmentally friendly, shapable hydrogels composed of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) in various casings for crop protection against different pests, fertilizing, and watering. To activate their effectiveness, PVA/PVP hydrogels were loaded with both hydrophilic and hydrophobic environmentally friendly pesticides, namely hydrogen peroxide (HP), the essential oil thymol, and urea as a fertilizer, either separately or in combination. This review covers various physical and chemical approaches used for loading, shaping, and controlling the release profiles of pesticides and fertilizers. Additionally, it explores the evaluation of the chemical composition, structure, classification, rheology, and morphology of the hydrogels as well as their impact on the thermal stability of the encapsulated pesticides and fertilizer, followed by biological tests. These hydrogels significantly contribute to the stabilization and controlled release of essential nutrients and biocides for plants, while maintaining excellent biocidal and fertilizing properties as well as sustainability characteristics. By shedding light on the latest insights into the concepts, applications, and results of these hydrogels, this review demonstrates their immense potential for widespread future use in agriculture.

Excellent Dark/Light Dual-Mode Photoresponsive Activities Based on g-C3N4/CMCh/PVA Nanocomposite Hydrogel Using Electron Beam Radiation Method

Photocatalytic technology for inactivating bacteria in water has received much attention. In this study, we reported a dark-light dual-mode sterilized g-C3N4/chitosan/poly (vinyl alcohol) hydrogel (g-CP) prepared through freeze-thaw cycling and an in situ electron-beam radiation method. The structures and morphologies of g-CP were confirmed using Fourier infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), solid ultraviolet diffuse reflectance spectroscopy (UV-vis DRS), and Brunauer-Emmett-Teller (BET). Photocatalytic degradation experiments demonstrated that 1 wt% g-CP degraded rhodamine B (RhB) up to 65.92% in 60 min. At the same time, g-CP had good antimicrobial abilities for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) within 4 h. The shapes of g-CP were adjustable (such as bar, cylinder, and cube) and had good mechanical properties and biocompatibility. The tensile and compressive modulus of 2 wt% g-CP were 0.093 MPa and 1.61 MPa, respectively. The Cell Counting Kit-8 (CCK-8) test and Hoechst33342/PI double staining were used to prove that g-CP had good biocompatibility. It is expected to be applied to environmental sewage treatment and wound dressing in the future.

Bimetal-Organic Framework-Loaded PVA/Chitosan Composite Hydrogel with Interfacial Antibacterial and Adhesive Hemostatic Features for Wound Dressings

Silver-containing wound dressings have shown attractive advantages in the treatment of wound infection due to their excellent antibacterial activity. However, the introduction of silver ions or AgNPs directly into the wound can cause deposition in the body as particles. Here, with the aim of designing low-silver wound dressings, a bimetallic-MOF antibacterial material called AgCu@MOF was developed using 3, 5-pyridine dicarboxylic acid as the ligand and Ag+ and Cu2+ as metal ion sites. PCbM (PVA/chitosan/AgCu@MOF) hydrogel was successfully constructed in PVA/chitosan wound dressing loaded with AgCu@MOF. The active sites on the surface of AgCu@MOF increased the lipophilicity to bacteria and caused the bacterial membrane to undergo lipid peroxidation, which resulted in the strong bactericidal properties of AgCu@MOF, and the antimicrobial activity of the dressing PCbM was as high as 99.9%. The chelation of silver ions in AgCu@MOF with chitosan occupied the surface functional groups of chitosan and reduced the crosslinking density of chitosan. PCbM changes the hydrogel crosslinking network, thus improving the water retention and water permeability of PCbM hydrogel so that the hydrogel has the function of binding wet tissue. As a wound adhesive, PCbM hydrogel reduces the amount of wound bleeding and has good biocompatibility. PCbM hydrogel-treated mice achieved 96% wound recovery on day 14. The strong antibacterial, tissue adhesion, and hemostatic ability of PCbM make it a potential wound dressing.

Food gels: principles, interaction mechanisms and its microstructure

Food hydrogels are important materials having great scientific interest due to biocompatibility, safety and environment-friendly characteristics. In the food industry, hydrogels are widely used due to their three-dimensional crosslinked networks. Furthermore, they have attracted great attention due to their wide range of applications in the food industry, such as fat replacers, encapsulating agents, target delivery vehicles, and many more. In addition to basic and recent knowledge on food hydrogels, this review exclusively focuses on sensorial perceptions, nutritional significance, body interactions, network structures, mechanical properties, and potential hydrogel applications in food and food-based matrices. Additionally, this review highlights the structural design of hydrogels, which provide the forward-looking idea for future applications of food hydrogels (e.g., 3D or 4D printing).

Silk fibroin nanoparticles and β-tricalcium phosphate loaded tissue engineered gelatin bone scaffolds: A Nature-based, low-cost solution

Tissue engineering has recently attracted attention as an alternative to traditional treatment methods for tissue and organ damage. Since bone is one of the most important vital parts of the body, the treatment of bone damage is important. Silk fibroin is a natural polymer with properties such as biocompatibility and biodegradability, which attracts attention with its controlled release, especially in drug delivery systems. In this study, gelatin-based scaffolds loaded with silk fibroin nanoparticles and β -tricalcium phosphate (β -TCP) were developed to be used as a potential drug delivery system in bone tissue engineering. The chosen nanoparticle formulation has a 294 nm average diameter with a 0.380 polidispersity index (PDI). In vitro characterization of scaffolds was performed by mechanical, morphological characterization, swelling capacity, Differential Scanning Calorimetry (DSC), Fourier-Transform Infrared Spectroscopy (FT-IR) measurements, and biocompatibility was evaluated by cell culture studies. Swelling index, tensile strength, elongation at break, and Young modulus of the β -TCP and silk nanoparticles loaded scaffold were found as 456%, 1.476 MPa, 6.75%, and 24 MPa, respectively. In vitro cell culture studies have shown that scaffolds prepared in the present study can accelerate osteoblast differentiation and increase the healing rate of bone tissues. In addition, they have the potential to be used as a drug delivery system in bone tissue engineering that needs to be evaluated with further studies.

Biodegradable piezoelectric skin-wound scaffold

Electrical stimulation (ES) induces wound healing and skin regeneration. Combining ES with the tissue-engineering approach, which relies on biomaterials to construct a replacement tissue graft, could offer a self-stimulated scaffold to heal skin-wounds without using potentially toxic growth factors and exogenous cells. Unfortunately, current ES technologies are either ineffective (external stimulations) or unsafe (implanted electrical devices using toxic batteries). Hence, we propose a novel wound-healing strategy that integrates ES with tissue engineering techniques by utilizing a biodegradable self-charged piezoelectric PLLA (Poly (l-lactic acid)) nanofiber matrix. This unique, safe, and stable piezoelectric scaffold can be activated by an external ultrasound (US) to produce well-controlled surface-charges with different polarities, thus serving multiple functions to suppress bacterial growth (negative surface charge) and promote skin regeneration (positive surface charge) at the same time. We demonstrate that the scaffold activated by low intensity/low frequency US can facilitate the proliferation of fibroblast/epithelial cells, enhance expression of genes (collagen I, III, and fibronectin) typical for the wound healing process, and suppress the growth of S. aureus and P. aeruginosa bacteria in vitro simultaneously. This approach induces rapid skin regeneration in a critical-sized skin wound mouse model in vivo. The piezoelectric PLLA skin scaffold thus assumes the role of a multi-tasking, biodegradable, battery-free electrical stimulator which is important for skin-wound healing and bacterial infection prevention simultaneuosly.

Facile preparation of biocompatible and antibacterial water-soluble films using polyvinyl alcohol/carboxymethyl chitosan blend fibers via centrifugal spinning

Water-soluble polyvinyl alcohol/carboxymethyl chitosan (PVA/CMCS) blend fiber films were successfully prepared using a plane-collection centrifugal spinning machine. The addition of CMCS significantly increased the shear viscosity of the PVA/CMCS blend solution. The effects of spinning temperature on the shear viscosity and the centrifugal spinnability of PVA/CMCS blend solution were discussed. The PVA/CMCS blend fibers were uniform, and their average diameters ranged from 1.23 μm to 29.01 μm. It was found that the CMCS was distributed evenly in the PVA matrix and increased the crystallinity of PVA/CMCS blend fiber films. The hydrogen bonds between the hydroxyl group of PVA and the carboxymethyl group of CMCS were also detected. An in vitro cell study of human skin fibroblast cells on the PVA/CMCS blend fiber films confirmed biocompatibility. The maximum tensile strength and elongation at break of PVA/CMCS blend fiber films could reach 3.28 MPa and 29.52 %, respectively. The colony-plate-count tests indicated that the PVA16-CMCS2 presented 72.05 % and 21.36 % antibacterial rates against Staphylococcus aureus (10⁴ CFU/mL) and Escherichia coli (10³ CFU/mL), respectively. These values indicated that the newly prepared PVA/CMCS blend fiber films are promising materials for cosmetic and dermatological applications.

Injectable multifunctional carboxymethyl chitosan/hyaluronic acid hydrogel for drug delivery systems

Injectable hydrogels with notable mechanical properties and self-healing ability are promising carriers for use as a drug delivery system. Here, adipic acid dihydrazide (ADH) and calcium ions (Ca2+) were introduced into quaternary ammonium carboxymethyl chitosan and aldehyde-modified hyaluronic acid hydrogels (QCS + OHA). The hydrogels were synthesized through the interaction of the Schiff bases (imine bonds, acylhydrazone bonds) and coordination bonds via a facile one-step approach. The gelation time (∼54 s) ensured excellent injectability. The QCS + OHA + ADH + Ca2+ hydrogel had notable mechanical properties (compressive stress up to 896.30 KPa), good self-healing ability (up to 94 %), good pH responsiveness, and excellent antibacterial properties. In addition, the QCS + OHA + ADH + Ca2+ hydrogel had a high drug loading capacity (121.3 mg/g) and sustained drug release behaviour (≥120 h). The results of cytotoxicity tests showed a high cell proliferation rate (up to 98 %) and good cytocompatibility. In summary, this work presents an injectable and self-healing pH-responsive hydrogel that can be used as a carrier for drug delivery systems.

Evaluation of newly copolymers and their montmorillonite nanocomposite as cold flow improver for petroleum lubricating oil

The great demand on the energy makes the attention toward modifying lubricating oil. This work tends to prepare the following copolymers; octadecylmethacrylate-co-dodecene (CP1) and octadecylmethacrylate-co-hexadecene (CP2) by free radical solution polymerization using laboratory prepared octadecylmethacrylate monomer with either 1-dodecene or 1-hexadecene. The same monomers also used to prepare their polymers nanocomposite (NP1, NP2) with 1% of nanomontmorolonite by emulsion polymerization. The structures of the prepared polymers and their nanocomposite were elucidated by FTIR, 1HNMR, TGA, DSC, TEM and DLS. These polymers were used as pour point depressant, flow improver and viscosity modifier and showed high efficiency. After comparison of the data of the polymers and their nanocomposite, the nanocomposite give the best results where the pour point decreased from 0 °C to - 18, - 27, - 24 and - 33 °C for CP1, CP2, NP1 and NP2 respectively at the optimum concentration 10,000 ppm. On the other hand the viscosity index increased from 86.57 to 93.25, 92.41, 94.17 and 93.103 for CP1, CP2, NP1 and NP2 respectively, the apparent viscosity increased from 55.863 to 69.31, 119.41, 111.28, and 166.89 cP also the yield stress increased from 652.19 to 1076.3, 1074 and 1480 D/cm2 for CP1, CP2, NP1 and NP2 respectively.

Characterization of By-products with High Fat Content Derived from the Production of Bovine Gelatin

Background: Gelatin is a protein obtained by partial hydrolysis of collagen contained in skins, connective tissue and/or animal bones, which are by-products of the meat industry. The main raw material to produce bovine gelatin is the dermis of the skin, but there is a variation in fat and moisture content depending on the bovine skin origin. As a contribution to the circular economy and sustainability, these by-products with high fat content and the fat released from them during the gelatin production process can be managed for food industries, mainly in the development or formulation of animal feed. Methods: For the initial physicochemical characterization, moisture, fat, protein and ashes content were determined. Once the by-products with high fat content were identified, alteration parameters such as acidity, peroxide and saponification indexes were evaluated. Additionally, thermal, rheological and fatty acid composition characterization was carried out in order to study the possible applications of the by-products. Results and Discussion: The results showed that certain by-products have a fat content of less than 15%, so the viability of their use is limited. On the other hand, some by-products have a fat content exceeding 30%; however, their extraction can only be done manually, resulting in a low efficiency process. By-products removed from the supernatant in the extractors presented fat percentages of 99.9 and 98.9%, and there exists the possibility of implementing a mechanical method for their extraction. The analysis of alteration and oxidation parameters, thermal and rheological characterization, fatty acid profile and solid fat content were exclusively conducted on these high-fat content by-products. Based on the characterization, these by-products could be valued and incorporated into animal feed formulations. Nevertheless, certain limitations exist for their use in applications such as biodiesel production or the food industry.

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.

High-strength, antibacterial, antioxidant, hemostatic, and biocompatible chitin/PEGDE-tannic acid hydrogels for wound healing

Natural polymer hydrogels are widely used in various aspects of biomedical engineering, such as wound repair, owing to their abundance and biosafety. However, the low strength and the lack of function restricted their development and application scope. Herein, we fabricated novel multifunctional chitin/PEGDE-tannic acid (CPT) hydrogels through chemical- and physical-crosslinking strategies, using chitin as the base material, polyethylene glycol diglycidyl ether (PEGDE) and tannic acid (TA) as crosslinking agents, and 90 % ethanol as the regenerative bath. CPT hydrogels maintained a stable three-dimensional porous structure with suitable water contents and excellent biocompatibility. The mechanical properties of hydrogels were greatly improved (tensile stress up to 5.43 ± 1.14 MPa). Moreover, CPT hydrogels had good antibacterial, antioxidant, and hemostatic activities and could substantially promote wound healing in a rat model of full-thickness skin defect by regulating inflammatory responses and promoting collagen deposition and blood vessel formation. Therefore, this work provides a useful strategy to fabricate novel multifunctional CPT hydrogels with excellent mechanical, antibacterial, antioxidant, hemostatic, and biocompatible properties. CPT hydrogels could be promising candidates for wound healing.

Potential use of propolis-loaded quaternized chitosan/pectin hydrogel films as wound dressings: Preparation, characterization, antibacterial evaluation, and in vitro healing assay

Quaternized chitosan (QCS) was blended with pectin (Pec) to improve water solubility and antibacterial activity of the hydrogel films. Propolis was also loaded into hydrogel films to improve wound healing ability. Therefore, the aim of this study was to fabricate and characterize the propolis-loaded QCS/Pec hydrogel films for use as wound dressing materials. The morphology, mechanical properties, adhesiveness, water swelling, weight loss, release profiles, and biological activities of the hydrogel films were investigated. Scanning Electron Microscope (SEM) investigation indicated a homogenous smooth surface of the hydrogel films. The blending of QCS and Pec increased tensile strength and Young's modulus values of the hydrogel films. Moreover, the blending of QCS and Pec improved the stability of the hydrogel films in the medium and controlled the release characteristics of propolis from the hydrogel films. The antioxidant activity of the released propolis from the propolis-loaded hydrogel films was ~21-36 %. The propolis-loaded QCS/Pec hydrogel films showed the bacterial growth inhibition, especially against S. aureus and S. pyogenes. The propolis-loaded hydrogel films were non-toxicity to mouse fibroblast cell line (NCTC clone 929) and supported the wound closure. Therefore, the propolis-loaded QCS/Pec hydrogel films might be good candidates for use as wound dressing materials.

Tissue Adhesive, Biocompatible, Antioxidant, and Antibacterial Hydrogels Based on Tannic Acid and Fungal-Derived Carboxymethyl Chitosan for Wound-Dressing Applications

This study aimed to develop hydrogels for tissue adhesion that are biocompatible, antioxidant, and antibacterial. We achieved this by using tannic acid (TA) and fungal-derived carboxymethyl chitosan (FCMCS) incorporated in a polyacrylamide (PAM) network using free-radical polymerization. The concentration of TA greatly influenced the physicochemical and biological properties of the hydrogels. Scanning electron microscopy showed that the nanoporous structure of the FCMCS hydrogel was retained with the addition of TA, resulting in a nanoporous surface structure. Equilibrium-swelling experiments revealed that increasing the concentration of TA significantly improved water uptake capacity. Antioxidant radical-scavenging assays and porcine skin adhesion tests confirmed the excellent adhesive properties of the hydrogels, with adhesion strengths of up to 39.8 ± 1.2 kPa for 1.0TA-FCMCS due to the presence of abundant phenolic groups on TA. The hydrogels were also found to be biocompatible with skin fibroblast cells. Furthermore, the presence of TA significantly enhanced the antibacterial properties of the hydrogels against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Therefore, the developed drug-free antibacterial and tissue-adhesive hydrogels can potentially be used as wound dressings for infected wounds.

Recent advances in carboxymethyl chitosan-based materials for biomedical applications

Chitosan (CS) and its derivatives have been applied extensively in the biomedical field owing to advantageous characteristics including biodegradability, biocompatibility, antibacterial activity and adhesive properties. The low solubility of CS at physiological pH limits its use in systems requiring higher dissolving ability and a suitable drug release rate. Besides, CS can result in fast drug release because of its high swelling degree and rapid water absorption in aqueous media. As a water-soluble derivative of CS, carboxymethyl chitosan (CMC) has certain improved properties, rendering it a more suitable candidate for wound healing, drug delivery and tissue engineering applications. This review will focus on the antibacterial, anticancer and antitumor, antioxidant and antifungal bioactivities of CMC and the most recently described applications of CMC in wound healing, drug delivery, tissue engineering, bioimaging and cosmetics.

An injectable elastic hydrogel crosslinked with curcumin-gelatin nanoparticles as a multifunctional dressing for the rapid repair of bacterially infected wounds

Injectable self-healing hydrogel dressings with excellent elasticity and multifunctional repair effects have been in high demand in wound healing applications, while maintaining stable elasticity in injectable multifunctional hydrogel dressings is still a challenge. Based on carboxymethyl chitosan (CMCS), curcumin-gelatin nanoparticles (CG NPs), and sodium alginate oxide (OSA), we developed a double-crosslinking injectable elastic self-healing hydrogel without any chemical cross-linking agent as a multifunctional wound healing dressing. CG NPs were more stable than pure curcumin (Cur) nanoparticles and could regulate the cross-linking of injectable hydrogels for high elasticity and rapid self-healing. We found that the CG NPs endowed the injectable hydrogel with good anti-inflammatory, antibacterial, and reactive oxygen scavenging activities and could significantly shorten the wound healing time in infected full-thickness skin defect rats by promoting the polarization of M2-type macrophages, reducing oxidative damage, accelerating collagen deposition, enhancing granulation formation, and elevating angiogenesis. Taken together, the tunable elastic injectable hydrogel dressing exhibited a long-term service life with sustained repair function and can be taken as an optimal candidate for bacteria-infected wound healing.