Innovation inspired by nature: Biocompatible self-healing injectable hydrogels based on modified-β-chitin for wound healing

Designing a Naturally Inspired Conductive Copolymer to Engineer Wearable Bioadhesives for Sensing Applications

The design of adhesive and conductive soft hydrogels using biopolymers with tunable mechanical properties has received significant interest in the field of wearable sensors for detecting human motions. These hydrogels are primarily fabricated through the modification of biopolymers to introduce cross-linking sites, the conjugation of adhesive components, and the incorporation of conductive materials into the hydrogel network. The development of a multifunctional copolymer that integrates adhesive and conductive properties within a single polymer chain with suitable cross-linking sites eliminates the need for biopolymer modification and the addition of extra conductive and adhesive components. In this study, we synthesized a copolymer based on poly([2-(methacryloyloxy)ethyl] trimethylammonium chloride-co-dopamine methacrylamide) (p(METAC-DMA)) using a controlled radical polymerization, allowing for the efficient conjugation of both adhesive and conductive units within a single polymer chain. Subsequently, our multifunctional hydrogel named Gel-MD was fabricated by mixing the p(METAC-DMA) copolymer with non-modified gelatin in which cross-linking took place in an oxidative environment. We confirmed the biocompatibility of the Gel-MD hydrogel through in vitro studies using NIH 3T3 cells as well as in vivo subcutaneous implantation in rats. Furthermore, the Gel-MD hydrogel was effective and sensitive in detecting various human motions, making it a promising wearable sensor for health monitoring and diagnosis.

Nanomaterials-incorporated polymeric microneedles for wound healing applications

There is a growing and urgent need for developing novel biomaterials and therapeutic approaches for efficient wound healing. Microneedles (MNs), which can penetrate necrotic tissues and biofilm barriers at the wound and deliver active ingredients to the deeper layers in a minimally invasive and painless manner, have stimulated the interests of many researchers in the wound-healing filed. Among various materials, polymeric MNs have received widespread attention due to their abundant material sources, simple and inexpensive manufacturing methods, excellent biocompatibility and adjustable mechanical strength. Meanwhile, due to the unique properties of nanomaterials, the incorporation of nanomaterials can further extend the application range of polymeric MNs to facilitate on-demand drug release and activate specific therapeutic effects in combination with other therapies. In this review, we firstly introduce the current status and challenges of wound healing, and then outline the advantages and classification of MNs. Next, we focus on the manufacturing methods of polymeric MNs and the different raw materials used for their production. Furthermore, we give a summary of polymeric MNs incorporated with several common nanomaterials for chronic wounds healing. Finally, we discuss the several challenges and future prospects of transdermal drug delivery systems using nanomaterials-based polymeric MNs in wound treatment application.

3D Printing of Polysaccharide-Based Hydrogel Scaffolds for Tissue Engineering Applications: A Review

In tissue engineering, 3D printing represents a versatile technology employing inks to construct three-dimensional living structures, mimicking natural biological systems. This technology efficiently translates digital blueprints into highly reproducible 3D objects. Recent advances have expanded 3D printing applications, allowing for the fabrication of diverse anatomical components, including engineered functional tissues and organs. The development of printable inks, which incorporate macromolecules, enzymes, cells, and growth factors, is advancing with the aim of restoring damaged tissues and organs. Polysaccharides, recognized for their intrinsic resemblance to components of the extracellular matrix have garnered significant attention in the field of tissue engineering. This review explores diverse 3D printing techniques, outlining distinctive features that should characterize scaffolds used as ideal matrices in tissue engineering. A detailed investigation into the properties and roles of polysaccharides in tissue engineering is highlighted. The review also culminates in a profound exploration of 3D polysaccharide-based hydrogel applications, focusing on recent breakthroughs in regenerating different tissues such as skin, bone, cartilage, heart, nerve, vasculature, and skeletal muscle. It further addresses challenges and prospective directions in 3D printing hydrogels based on polysaccharides, paving the way for innovative research to fabricate functional tissues, enhancing patient care, and improving quality of life.

Evolution of Hybrid Hydrogels: Next-Generation Biomaterials for Drug Delivery and Tissue Engineering

Hydrogels, being hydrophilic polymer networks capable of absorbing and retaining aqueous fluids, hold significant promise in biomedical applications owing to their high water content, permeability, and structural similarity to the extracellular matrix. Recent chemical advancements have bolstered their versatility, facilitating the integration of the molecules guiding cellular activities and enabling their controlled activation under time constraints. However, conventional synthetic hydrogels suffer from inherent weaknesses such as heterogeneity and network imperfections, which adversely affect their mechanical properties, diffusion rates, and biological activity. In response to these challenges, hybrid hydrogels have emerged, aiming to enhance their strength, drug release efficiency, and therapeutic effectiveness. These hybrid hydrogels, featuring improved formulations, are tailored for controlled drug release and tissue regeneration across both soft and hard tissues. The scientific community has increasingly recognized the versatile characteristics of hybrid hydrogels, particularly in the biomedical sector. This comprehensive review delves into recent advancements in hybrid hydrogel systems, covering the diverse types, modification strategies, and the integration of nano/microstructures. The discussion includes innovative fabrication techniques such as click reactions, 3D printing, and photopatterning alongside the elucidation of the release mechanisms of bioactive molecules. By addressing challenges, the review underscores diverse biomedical applications and envisages a promising future for hybrid hydrogels across various domains in the biomedical field.

Biological Macromolecule Hydrogel Based on Recombinant Type I Collagen/Chitosan Scaffold to Accelerate Full-Thickness Healing of Skin Wounds

The development of biological macromolecule hydrogel dressings with fatigue resistance, sufficient mechanical strength, and versatility in clinical treatment is critical for accelerating full-thickness healing of skin wounds. Therefore, in this study, multifunctional, biological macromolecule hydrogels based on a recombinant type I collagen/chitosan scaffold incorporated with a metal-polyphenol structure were fabricated to accelerate wound healing. The resulting biological macromolecule hydrogel possesses sufficient mechanical strength, fatigue resistance, and healing properties, including antibacterial, antioxygenic, self-healing, vascularization, hemostatic, and adhesive abilities. Chitosan and recombinant type I collagen formed the scaffold network, which was the first covalent crosslinking network of the hydrogel. The second physical crosslinking network comprised the coordination of a metal-polyphenol structure, i.e., Cu2+ with the catechol group of dopamine methacrylamide (DMA) and stacking of DMA benzene rings. Double-crosslinked networks are interspersed and intertwined in the hydrogel to reduce the mechanical strength and increase its fatigue resistance, making it more suitable for clinical applications. Moreover, the biological macromolecule hydrogel can continuously release Cu2+, which provides strong antibacterial and vascularization properties. An in vivo full-thickness skin defect model confirmed that multifunctional, biological macromolecule hydrogels based on a recombinant type I collagen/chitosan scaffold incorporated with a metal-polyphenol structure can facilitate the formation of granulation tissue and collagen deposition for a short period to promote wound healing. This study highlights that this biological macromolecule hydrogel is a promising acute wound-healing dressing for biomedical applications.

Polysaccharides, proteins, and synthetic polymers based multimodal hydrogels for various biomedical applications: A review

Nature-derived or biologically encouraged hydrogels have attracted considerable interest in numerous biomedical applications owing to their multidimensional utility and effectiveness. The internal architecture of a hydrogel network, the chemistry of the raw materials involved, interaction across the interface of counter ions, and the ability to mimic the extracellular matrix (ECM) govern the clinical efficacy of the designed hydrogels. This review focuses on the mechanistic viewpoint of different biologically driven/inspired biomacromolecules that encourages the architectural development of hydrogel networks. In addition, the advantage of hydrogels by mimicking the ECM and the significance of the raw material selection as an indicator of bioinertness is deeply elaborated in the review. Furthermore, the article reviews and describes the application of polysaccharides, proteins, and synthetic polymer-based multimodal hydrogels inspired by or derived from nature in different biomedical areas. The review discusses the challenges and opportunities in biomaterials along with future prospects in terms of their applications in biodevices or functional components for human health issues. This review provides information on the strategy and inspiration from nature that can be used to develop a link between multimodal hydrogels as the main frame and its utility in biomedical applications as the primary target.

Synthesis and Applications of Hybrid Polymer Networks Based on Renewable Natural Macromolecules

Macromolecules obtained from renewable natural sources are gaining increasing attention as components for a vast variety of sustainable polymer-based materials. Natural raw materials can facilitate continuous-flow production due to their year-round availability and short replenishment period. They also open new opportunities for chemists and biologists to design and create "bioreplacement" and "bioadvantaged" polymers, where complex structures produced by nature are being modified, upgraded, and utilized to create novel materials. Bio-based macromonomers are expected not only to compete with but to replace some petroleum-based analogs, as well. The development of novel sustainable materials is an ongoing and very dynamic process. There are multiple strategies for transforming natural macromolecules into sophisticated value-added products. Some methods include chemical modification of macromolecules, while others include blending several components into one new system. One of the most promising approaches for incorporating renewable macromolecules into new products is the synthesis of hybrid networks based on one or more natural components. Each one has unique characteristics, so its incorporation into a network brings new sustainable materials with properties that can be tuned according to their end-use. This article reviews the current state-of-the-art and future potential of renewable natural macromolecules as sustainable building blocks for the synthesis and use of hybrid polymer networks. The most recent advancements and applications that involve polymers, such as cellulose, chitin, alginic acid, gellan gum, lignin, and their derivatives, are discussed.

Recent progress of antibacterial hydrogels in wound dressings

Hydrogels are essential biomaterials due to their favorable biocompatibility, mechanical properties similar to human soft tissue extracellular matrix, and tissue repair properties. In skin wound repair, hydrogels with antibacterial functions are especially suitable for dressing applications, so novel antibacterial hydrogel wound dressings have attracted widespread attention, including the design of components, optimization of preparation methods, strategies to reduce bacterial resistance, etc. In this review, we discuss the fabrication of antibacterial hydrogel wound dressings and the challenges associated with the crosslinking methods and chemistry of the materials. We have investigated the advantages and limitations (antibacterial effects and antibacterial mechanisms) of different antibacterial components in the hydrogels to achieve good antibacterial properties, and the response of hydrogels to stimuli such as light, sound, and electricity to reduce bacterial resistance. Conclusively, we provide a systematic summary of antibacterial hydrogel wound dressings findings (crosslinking methods, antibacterial components, antibacterial methods) and an outlook on long-lasting antibacterial effects, a broader antibacterial spectrum, diversified hydrogel forms, and the future development prospects of the field.

Healing Wounds Efficiently with Biomimetic Soft Matter: Injectable Self-Healing Neutral Glycol Chitosan/Dibenzaldehyde-Terminated Poly(ethylene glycol) Hydrogel with Inherent Antibacterial Properties

The high prevalence of acquiring skin wounds, along with the emergence of antibiotic-resistant strains that lead to infections, impose a threat to the physical, mental, and socioeconomic health of society. Among the wide array of wound dressings developed, hydrogels are regarded as a biomimetic soft matter of choice owing to their ability to provide a moist environment ideal for healing. Herein, neutral glycol chitosan (GC) was cross-linked via imine bonds with varying concentrations of dibenzaldehyde-terminated polyethylene glycol (DP) to give glycol chitosan/dibenzaldehyde-terminated polyethylene glycol hydrogels (GC/DP). These dynamic Schiff base linkages (absorption peak at 1638 cm^-1) within the hydrogel structure endowed their ability to recover from damage as characterized by high-low strain exposure in continuous step strain rheology. Along with their good injectability and biodegradability, the hydrogels exhibited remarkable inhibition against E. coli, P. aeruginosa, and S. aureus. GC/DP hydrogels demonstrated high LC50 values in vivo using zebrafish embryos as a model system due to their relative biocompatibility and a remarkable 93.4 ± 0.88% wound contraction at 30-dpw against 49.1 ± 3.40% of the control. To the best of our knowledge, this is the first study that developed injectable glycol chitosan/dibenzaldehyde-terminated polyethylene glycol self-healing hydrogels for application in wound healing with intrinsic bacteriostatic properties against the three bacteria.

Different Curcumin-Loaded Delivery Systems for Wound Healing Applications: A Comprehensive Review

Curcumin or turmeric is the active constituent of Curcuma longa L. It has marvelous medicinal applications in many diseases. When the skin integrity is compromised due to either acute or chronic wounds, the body initiates several steps leading to tissue healing and skin barrier function restoration. Curcumin has very strong antibacterial and antifungal activities with powerful wound healing ability owing to its antioxidant activity. Nevertheless, its poor oral bioavailability, low water solubility and rapid metabolism limit its medical use. Tailoring suitable drug delivery systems for carrying curcumin improves its pharmaceutical and pharmacological effects. This review summarizes the most recent reported curcumin-loaded delivery systems for wound healing purposes, chiefly hydrogels, films, wafers, and sponges. In addition, curcumin nanoformulations such as nanohydrogels, nanoparticles and nanofibers are also presented, which offer better solubility, bioavailability, and sustained release to augment curcumin wound healing effects through stimulating the different healing phases by the aid of the small carrier.

Toward Stimuli-Responsive Soft Robots with 3D Printed Self-Healing Konjac Glucomannan Gels

Significant progress in fabricating new multifunctional soft materials and the advances of additive manufacturing technologies have given birth to a new generation of soft robots with complex capabilities, such as crawling, swimming, jumping, gripping, and releasing. Within this vast array of responsive soft materials, hydrogels receive considerable attention due to their fascinating properties, including biodegradable, self-healing, stimuli-responsive, and large volume transformation. Konjac glucomannan (KGM) is an edible polysaccharide that forms a pH-responsive, self-healing hydrogel when crosslinked with borax, and it is the focus of this study. A novel KGM-Borax ink for three-dimensional (3D) printing of free-form structures and soft robots at room temperature is presented. A complete process from ink preparation to the fabrication of a completely cross-linked part is demonstrated. Print setting parameters, rheological properties of the ink and crosslinked gels were characterized. Print quality was found to be consistent across a wide range of print settings. The minimum line width achieved is 650 μm. Tensile testing was carried out to validate the self-healing capability of the KGM-Borax gel. Results show that KGM-Borax has a high self-healing efficiency of 98%. Self-healing underwater was also demonstrated, a rarity for crosslinked gels. The means to form complex structures via 3D printing, reacting to environmental stimuli and the resilience against damage, make this new KGM-Borax gel a promising candidate for the fabrication of the next generation of soft robots.

Facile fabrication of chitin/ZnO composite hydrogels for infected wound healing

When ordinary wounds are infected, the skin's self-healing capacity declines; thus appropriate dressings with both antibacterial ability and healing ability for bacteria-associated wounds are indispensable. In this work, multifunctional chitin/ZnO composite hydrogels have been designed as an infected full-thickness skin wound-healing material. The hydrogels are fabricated by a facile one-pot strategy through the sequential addition of commercial ZnO powders into aqueous alkaline chitin solutions, crosslinking and regeneration. The regenerated nanoscale ZnO particles aggregate into microscale particles and are embedded in the chitin matrix with tight interactions, including hydrogen bonding and coordination interactions. The decoration of ZnO endows the chitin/ZnO composite hydrogels with excellent antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), with acceptable biocompatibility. More importantly, the chitin/ZnO composite hydrogels show an outstanding accelerated infectious full-thickness wound-healing performance with more fibroblast proliferation, more collagen deposition, and more neogenesis of the epithelium and granulation tissue. Therefore, it is expected that the chitin/ZnO composite hydrogels can serve as competitive skin wound dressings for the prevention and control of infections.

Chitin and Chitosan: Prospective Biomedical Applications in Drug Delivery, Cancer Treatment, and Wound Healing

Chitin and its derivative chitosan are highly abundant polymers in nature, appearing in both the shells and exoskeletons of various marine and non-marine species. Since they possess favorable properties, such as biocompatibility, biodegradability, non-toxicity, and non-immunogenicity, they have gained recent attention due to their enormous potential biomedical applications. The polycationic surface of chitosan enables it to form hydrogenic and ionic bonds with drug molecules, which is one of its most useful properties. Because chitosan is biocompatible, it can therefore be used in drug delivery systems. The development of chitosan-based nanoparticles has also contributed to the significance of chitin as a drug delivery system that can deliver drugs topically. Furthermore, chitin can be used in cancer treatment as a vehicle for delivering cancer drugs to a specific site and has an antiproliferative effect by reducing the viability of cells. Finally, chitosan can be used as a wound dressing in order to promote the faster regeneration of skin epithelial cells and collagen production by fibroblasts. As discussed in this review, chitin and chitosan have diverse applications in the medical field. Recognizing the biomedical applications of these two polymers is essential for future research in tissue engineering and nanobiotechnology.

Antibacterial adhesive self-healing hydrogels to promote diabetic wound healing

The development of compressible, stretchable and self-healing hydrogel dressings with good adhesive, antibacterial and angiogenesis properties is needed to promote the regeneration of diabetic wounds in clinical applications. In this work, a series of self-healing, adhesive and antibacterial hydrogels based on gelatin methacrylate (GelMA), adenine acrylate (AA), and CuCl₂ were designed through covalent bonding, coordination complexation of Cu²⁺ and carboxyl groups and hydrogen bonding to promote diabetic wound healing. These hydrogels exhibit efficient self-healing properties, remarkable fatigue resistance, and good adhesive properties due to the hydrogen bond and the metal-ligand coordination provided by the Cu²⁺ and the carboxyl group. The GelMA/AA/Cu1.0 hydrogel (containing 1.0 mg/mL Cu²⁺) with well-balanced biocompatibility and antibacterial properties exhibited efficient hemostatic performance in a mouse liver trauma model and significantly promoted the healing process in a full-thickness skin diabetic wound model. The immunohistochemistry results showed that the GelMA/AA/Cu1.0 hydrogel can promote regular epithelialization and collagen deposition when compared to the Tegaderm^TM Film, GelMA hydrogel, and GelMA/AA/Cu0 hydrogel. The immunofluorescence results confirmed that the GelMA/AA/Cu1.0 hydrogel can reduce the expression of proinflammatory factors and promote angiogenesis. In conclusion, the GelMA/AA/Cu hydrogel is an effective wound dressing to promote the healing process of diabetic skin wounds. STATEMENT OF SIGNIFICANCE: Diabetic wounds exhibit an extremely high risk of bacterial infection and poor angiogenesis in a high-sugar environment, hindering their healing process. Hydrogel wound dressings are a promising wound care material that need to have stable and long-lasting adhesive properties, avoid shedding, provide lasting protection to wounds, antibacterial properties and promote angiogenesis. In this study, a series of self-healing, adhesive, and antibacterial hydrogels based on gelatin methacrylate (GelMA), acrylated adenine (AA), and CuCl₂ were designed and synthesized via free radical polymerization, hydrogen bond, and ionic bond to promote diabetic wound healing. Overall, GelMA/AA/Cu hydrogels are promising materials to promote diabetic wound healing.

Oxidized dextran crosslinked polysaccharide/protein/polydopamine composite cryogels with multiple hemostatic efficacies for noncompressible hemorrhage and wound healing

Noncompressible hemorrhage caused by gunshots and sharp objects leads to higher trauma mortality, and cryogels have great potential in controlling noncompressible hemorrhage applications owing to their shape-memory properties. However, the use of non-toxic crosslinkers to prepare cryogels for noncompressible hemorrhage remains a challenge. In this study, a series of cryogels were prepared using oxidized dextran (ODex) as a biocompatible crosslinker, combined with the good hemostatic properties of chitosan (CS) and human-like collagen (HLC), and polydopamine nanoparticles (PDA-NPs) were also introduced to strengthen the shape recovery speed of the cryogels and further enhance their hemostatic performance. The CS/HLC/ODex/PDA-NPs (CHOP) cryogels presented a highly interconnected macroporous structure, powerful water/blood absorption capacity, robust mechanical performance, and rapid water/blood-triggered shape recovery. In vitro coagulation and coagulation mechanism tests showed that CHOP exhibited strong procoagulant ability, high adhesion to blood cells and fibrinogen, and the capacity to activate platelets and intrinsic pathways. In vivo hemostatic tests indicated that CHOP could effectively shorten the bleeding time and reduce the bleeding volume of liver incision bleeding and liver noncompressible hemorrhage. Meanwhile, CHOP exhibited good biocompatibility and biodegradability, and could promote wound healing. These results suggest that CHOP cryogels will be a promising hemostatic dressing.

pH-Responsive Copolymeric Network Gel Using Methacrylated β-Cyclodextrin for Controlled Codelivery of Hydrophilic and Hydrophobic Drugs

In medical science, sometimes two drugs with different solubilities are simultaneously required in combination to treat various diseases. Herein, a pH-responsive, copolymeric, antioxidant, biocompatible, and chemically crosslinked network gel is prepared to explore its capability as a matrix for controlled release of both hydrophobic [ibuprofen (IB)] and hydrophilic [tetracycline hydrochloride (TCH)] drugs, simultaneously. This three-dimensional β-CD-Meth-cl-(PHPMA-co-PAAc) network hydrogel is synthesized via two steps: (I) methacrylation of β-cyclodextrin and (II) grafting of poly(hydroxypropyl methacrylate) and poly(acrylic acid), followed by crosslinking of poly(ethylene glycol) diacrylate onto the backbone of methacrylated β-cyclodextrin (β-CD-Meth). The successful synthesis of the hydrogel is confirmed using several physiochemical characterizations. The β-CD-Meth-cl-(PHPMA-co-PAAc) hydrogel has an excellent network-like surface morphology. The potential pH-responsive high swelling behavior and excellent shrinking features suggest the reversible nature of the synthesized gel. Besides, rheological analyses affirm its excellent viscoelastic nature. This network gel is biodegradable and its non-cytotoxic nature toward human dermal fibroblast cells is demonstrated. Moreover, the dual drug release pattern from the copolymer under both in vitro and in vivo conditions portrays that this hydrogel has superior ability to be used as a controlled release matrix for both hydrophobic and hydrophilic drugs (TCH and IB) with varying solubilities concurrently.

Mechanochemical Transformations of Biomass into Functional Materials

Biomass is one of the promising alternatives to petroleum-derived materials and plays a major role in our fight against climate change by providing renewable sources of chemicals and materials. Owing to its chemical and structural complexity, the transformation of biomass into value-added products requires a profound understanding of its composition at different scales and innovative methods such as combining physical and chemical processes. In this context, the use of mechanochemistry in biomass valorization is currently growing owing to its potentials as an efficient, sustainable, and environmentally friendly approach. This review highlights the latest advances in the transformation of biomass (i. e., chitin, cellulose, hemicellulose, lignin, and starch) to functional materials using mechanochemical-assisted methods. We focused here on the methodology of biomass processing, influencing factors, and resulting properties with an emphasis on achieving functional materials rather than breaking down the biopolymer chains into smaller molecules. Opportunities and limitations associated this methodology were discussed accordingly for future directions.

Crosslinkers for polysaccharides and proteins: Synthesis conditions, mechanisms, and crosslinking efficiency, a review

Polysaccharides and proteins are important macromolecules for developing hydrogels devoted to biomedical applications. Chemical hydrogels offer chemical, mechanical, and dimensional stability than physical hydrogels due to the chemical bonds among the chains mediated by crosslinkers. There are many crosslinkers to synthesize polysaccharides and proteins based on hydrogels. In this review, we revisited the crosslinking reaction mechanisms between synthetic or natural crosslinkers and polysaccharides or proteins. The selected synthetic crosslinkers were glutaraldehyde, carbodiimide, boric acid, sodium trimetaphosphate, N,N'-methylene bisacrylamide, and polycarboxylic acid, whereas the selected natural crosslinkers included transglutaminase, tyrosinase, horseradish peroxidase, laccase, sortase A, genipin, vanillin, tannic acid, and phytic acid. No less important are the reactions involving click chemistry and the macromolecular crosslinkers for polysaccharides and proteins. Literature examples of polysaccharides or proteins crosslinked by the different strategies were presented along with the corresponding highlights. The general mechanism involved in chemical crosslinking mediated by gamma and UV radiation was discussed, with particular attention to materials commonly used in digital light processing. The evaluation of crosslinking efficiency by gravimetric measurements, rheology, and spectroscopic techniques was presented. Finally, we presented the challenges and opportunities to create safe chemical hydrogels for biomedical applications.

Adipose-derived mesenchymal stem cell-loaded β-chitin nanofiber hydrogel promote wound healing in rats

Because of stem cells are limited by the low efficiency of their cell homing and survival in vivo, cell delivery systems and scaffolds have attracted a great deal of attention for stem cells' successful clinical practice. β-chitin nanofibers (β-ChNF) were prepared from squid pens in this study. Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy proved that β-ChNFs with the diameter of 5 to 10 nm were prepared. β-ChNF dispersion became gelled upon the addition of cell culture medium. Cell culture experiments showed that β-ChNFs exhibited negligible cytotoxicity towards ADSCs and L929 cells, and it was found that more exosomes were secreted by the globular ADSCs grown in the β-ChNF hydrogel. The vivo experiments of rats showed that the ADSCs-loaded β-ChNF hydrogel could directly cover the wound surface and significantly accelerate the wound healing and promote the generation of epithelization, granulation tissue and collagen. In addition, the ADSCs-loaded β-ChNF hydrogel clearly regulated the expressions of VEGFR, α-SMA, collagen I and collagen III. Finally, we showed that ADSCs-loaded β-ChNF hydrogel activated the TGFβ/smad signaling. The neutralization of TGFβ markedly reduced Smad phosphorylation and the expressions of TIMP1, VEGFR and α-SMA. Taken together, these findings suggest that ADSCs-loaded β-ChNF hydrogel promises for treating wounds that are challenge to heal via conventional methods. Graphical abstract.

A hybrid hydrogel composed of chitin and β-glucan for effectively management of wound healing and scarring

Non-functional scar commonly forms after the skin injury. At present, most of the clinical treatments for scar eradication are typically with long treatment courses, low curative effects and expensive. In...

Self-Healing Hydrogels: Preparation, Mechanism and Advancement in Biomedical Applications

Polymeric hydrogels are widely explored materials for biomedical applications. However, they have inherent limitations like poor resistance to stimuli and low mechanical strength. This drawback of hydrogels gave rise to ''smart self-healing hydrogels'' which autonomously repair themselves when ruptured or traumatized. It is superior in terms of durability and stability due to its capacity to reform its shape, injectability, and stretchability thereby regaining back the original mechanical property. This review focuses on various self-healing mechanisms (covalent and non-covalent interactions) of these hydrogels, methods used to evaluate their self-healing properties, and their applications in wound healing, drug delivery, cell encapsulation, and tissue engineering systems. Furthermore, composite materials are used to enhance the hydrogel's mechanical properties. Hence, findings of research with various composite materials are briefly discussed in order to emphasize the healing capacity of such hydrogels. Additionally, various methods to evaluate the self-healing properties of hydrogels and their recent advancements towards 3D bioprinting are also reviewed. The review is concluded by proposing several pertinent challenges encountered at present as well as some prominent future perspectives.

The Versatility of Polymeric Materials as Self-Healing Agents for Various Types of Applications: A Review

The versatility of polymeric materials as healing agents to prevent any structure failure and their ability to restore their initial mechanical properties has attracted interest from many researchers. Various applications of the self-healing polymeric materials are explored in this paper. The mechanism of self-healing, which includes the extrinsic and intrinsic approaches for each of the applications, is examined. The extrinsic mechanism involves the introduction of external healing agents such as microcapsules and vascular networks into the system. Meanwhile, the intrinsic mechanism refers to the inherent reversibility of the molecular interaction of the polymer matrix, which is triggered by the external stimuli. Both self-healing mechanisms have shown a significant impact on the cracked properties of the damaged sites. This paper also presents the different types of self-healing polymeric materials applied in various applications, which include electronics, coating, aerospace, medicals, and construction fields. It is expected that this review gives a significantly broader idea of self-healing polymeric materials and their healing mechanisms in various types of applications.

Chitin and Chitosan Derivatives as Biomaterial Resources for Biological and Biomedical Applications

Chitin is a long-chain polymer of N-acetyl-glucosamine, which is regularly found in the exoskeleton of arthropods including insects, shellfish and the cell wall of fungi. It has been known that chitin can be used for biological and biomedical applications, especially as a biomaterial for tissue repairing, encapsulating drug for drug delivery. However, chitin has been postulated as an inducer of proinflammatory cytokines and certain diseases including asthma. Likewise, chitosan, a long-chain polymer of N-acetyl-glucosamine and d-glucosamine derived from chitin deacetylation, and chitosan oligosaccharide, a short chain polymer, have been known for their potential therapeutic effects, including anti-inflammatory, antioxidant, antidiarrheal, and anti-Alzheimer effects. This review summarizes potential utilization and limitation of chitin, chitosan and chitosan oligosaccharide in a variety of diseases. Furthermore, future direction of research and development of chitin, chitosan, and chitosan oligosaccharide for biomedical applications is discussed.

Intestinal Population in Host with Metabolic Syndrome during Administration of Chitosan and Its Derivatives

Chitosan and its derivatives can alleviate metabolic syndrome by different regulation mechanisms, phosphorylation of AMPK (AMP-activated kinase) and Akt (also known as protein kinase B), suppression of PPAR-γ (peroxisome proliferator-activated receptor-γ) and SREBP-1c (sterol regulatory element–binding proteins), and translocation of GLUT4 (glucose transporter-4), and also the downregulation of fatty-acid-transport proteins, fatty-acid-binding proteins, fatty acid synthetase (FAS), acetyl-CoA carboxylase (acetyl coenzyme A carboxylase), and HMG-CoA reductase (hydroxy methylglutaryl coenzyme A reductase). The improved microbial profiles in the gastrointestinal tract were positively correlated with the improved glucose and lipid profiles in hosts with metabolic syndrome. Hence, this review will summarize the current literature illustrating positive correlations between the alleviated conditions in metabolic syndrome hosts and the normalized gut microbiota in hosts with metabolic syndrome after treatment with chitosan and its derivatives, implying that the possibility of chitosan and its derivatives to serve as therapeutic application will be consolidated. Chitosan has been shown to modulate cardiometabolic symptoms (e.g., lipid and glycemic levels, blood pressure) as well as gut microbiota. However, the literature that summarizes the relationship between such metabolic modulation of chitosan and prebiotic-like effects is limited. This review will discuss the connection among their structures, biological properties, and prebiotic effects for the treatment of metabolic syndrome. Our hope is that future researchers will consider the prebiotic effects as significant contributors to the mitigation of metabolic syndrome.

Revamping squid gladii to biodegradable composites: In situ grafting of polyaniline to β-chitin and their antibacterial activity

The global health concern on wound care is becoming more challenging with the emerging prevalence of inexorable antibiotic resistance. Amidst this crisis, various material innovations have been made to combat this dilemma. Herein, squid pens, which are regarded as discards in the seafood industry, were biorefined into β-chitin-graft-polyaniline (β-chitin-g-PANI) composites for possible wound dressing development. β-chitin was first chemically extracted from gladii, and was then grafted with PANI via in situ chemical oxidative polymerization of various concentrations of aniline, to produce the β-chitin-g-PANI composites. Supporting data from FTIR, UV-Vis, SEM, TGA, and DSC suggest that β-chitin was successfully grafted with PANI. Moreover, improved conductivity and in vitro degradation of the composites were observed as compared to β-chitin and PANI alone, respectively. Zones of inhibition observed from agar diffusion method suggest that the synthesized composites have antibacterial activity against E. coli and S. aureus. The resulting physicochemical and biological properties of integrating conducting PANI to β-chitin substantiated and rendered the β-chitin-g-PANI composites desirable candidates for the development wound care products.