Chitosan-based hydrogels: From preparation to biomedical applications

Chitosan-based matrix as a carrier for bacteriophages

Wound healing is a dynamic and complex process where infection prevention is essential. Chitosan, thanks to its bactericidal activity against gram-positive and gram-negative bacteria, as well as anti-inflammatory and hemostatic properties, is an excellent candidate to design dressings for difficult-to-heal wound treatment. The great advantage of this biopolymer is its capacity to be chemically modified, which allows for the production of various functional forms, depending on the needs and subsequent use. Moreover, chitosan can be an excellent polymer matrix for bacteriophage (phage) packing as a novel alternative/supportive antibacterial therapy approach. This study is focused on the preparation and characteristics of chitosan-based material in the form of a film with the addition of Pseudomonas lytic phages (KTN4, KT28, and LUZ19), which would exhibit antibacterial activity as a potential dressing that accelerates the wound healing. We investigated the method of producing a polymer based on microcrystalline chitosan (MKCh) to serve as the matrix for phage deposition. We described some important parameters such as average molar mass, swelling capacity, surface morphology, phage release profile, and antibacterial activity tested in the Pseudomonas aeruginosa bacterial model. The chitosan polysaccharide turned out to interact with phage particles immobilizing them within a material matrix. Nevertheless, with the high hydrophilicity and swelling features of the prepared material, the external solution of bacterial culture was absorbed and phages went in direct contact with bacteria causing their lysis in the polymer matrix. KEY POINTS: • A novel chitosan-based matrix with the addition of active phages was prepared • Phage interactions with the chitosan matrix were determined as electrostatic • Phages in the matrix work through direct contact with the bacterial cells.

Oral administration microrobots for drug delivery

Oral administration is the most simple, noninvasive, convenient treatment. With the increasing demands on the targeted drug delivery, the traditional oral treatment now is facing some challenges: 1) biologics how to implement the oral treatment and ensure the bioavailability is not lower than the subcutaneous injections; 2) How to achieve targeted therapy of some drugs in the gastrointestinal tract? Based on these two issues, drug delivery microrobots have shown great application prospect in oral drug delivery due to their characteristics of flexible locomotion or driven ability. Therefore, this paper summarizes various drug delivery microrobots developed in recent years and divides them into four categories according to different driving modes: magnetic-controlled drug delivery microrobots, anchored drug delivery microrobots, self-propelled drug delivery microrobots and biohybrid drug delivery microrobots. As oral drug delivery microrobots involve disciplines such as materials science, mechanical engineering, medicine, and control systems, this paper begins by introducing the gastrointestinal barriers that oral drug delivery must overcome. Subsequently, it provides an overview of typical materials involved in the design process of oral drug delivery microrobots. To enhance readers' understanding of the working principles and design process of oral drug delivery microrobots, we present a guideline for designing such microrobots. Furthermore, the current development status of various types of oral drug delivery microrobots is reviewed, summarizing their respective advantages and limitations. Finally, considering the significant concerns regarding safety and clinical translation, we discuss the challenges and prospections of clinical translation for various oral drug delivery microrobots presented in this paper, providing corresponding suggestions for addressing some existing challenges.

Reconstruction of Chitosan Network Orders Using the Meniscus Splitting Method for Designing pH-Responsive Materials

Chitosan is a product of deacetylated chitin and a natural polymer that is attractive as a functional and biocompatible material in the pursuit of alternative materials to synthetic plastics for a sustainable society. Although hierarchical architectures, from precise molecular structures to nanofibers and twisted structures, have been clarified, the expansion of the anisotropic microstructures of chitosan into millimeter-scale materials is in the process of development. In this study, a chitosan network was reconstructed from an aqueous solution by using the meniscus splitting method to form a three-dimensionally ordered microstructure. A chitosan membrane deposited on the millimeter scale formed a useful anisotropically pH-responsive hydrogel. During the evaporation of the aqueous solution from a finite space, chitosan underwent ordered deposition by capillary force to form a membrane with oriented microstructures and microlayers. Unlike the cast films formed between solid-liquid and air-liquid interfaces, this membrane formed between two air-liquid interfaces. As a result, the membranes with ordered microstructures were capable of signifying directional swelling in aqueous environments and reversible/irreversible swelling-deswelling changes by controlling the pH range. We envision that the anisotropic pH response of the chitosan network can be utilized under physiological conditions as a next-generation material.

A review of the fungal polysaccharides as natural biopolymers: Current applications and future perspective

As a unique natural resource, fungi are a sustainable source of lipids, polysaccharides, vitamins, proteins, and other nutrients. As a result, they have beneficial medicinal and nutritional properties. Polysaccharides are among the most significant bioactive components found in fungi. Increasing research has revealed that fungal polysaccharides (FPS) contain a variety of bioactivities, including antitumor, antioxidant, immunomodulatory, anti-inflammatory, hepatoprotective, cardioprotective, and anti-aging properties. However, the exact knowledge about FPS and their applications related to their future possibilities must be thoroughly examined to enhance a better understanding of this sustainable biopolymer source. Therefore, FPS' biological applications and their role in the food and feed industry, agriculture, and cosmetics applications were all discussed in this work. In addition, this review highlighted the mode of action of FPS on human diseases by regulating gut microbiota and discussed the mechanism of FPS as antioxidants in the living cell. The structure-activity connections of FPS were also highlighted and explored. Moreover, future perspectives were listed to pave the way for future studies of FPS applications. Hence, this study can be a scientific foundation for future FPS research and industrial applications.

Enhancing Wastewater Depollution: Sustainable Biosorption Using Chemically Modified Chitosan Derivatives for Efficient Removal of Heavy Metals and Dyes

Driven by concerns over polluted industrial wastewater, particularly heavy metals and dyes, this study explores biosorption using chemically cross-link chitosan derivatives as a sustainable and cost-effective depollution method. Chitosan cross-linking employs either water-soluble polymers and agents like glutaraldehyde or copolymerization of hydrophilic monomers with a cross-linker. Chemical cross-linking of polymers has emerged as a promising approach to enhance the wet-strength properties of materials. The chitosan thus extracted, as powder or gel, was used to adsorb heavy metals (lead (Pb2+) and copper (Cu2+)) and dyes (methylene blue (MB) and crystal violet (CV)). Extensive analysis of the physicochemical properties of both the powder and hydrogel adsorbents was conducted using a range of analytical techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and scanning electron microscopy (SEM), as well as 1H and 13C nuclear magnetic resonance (NMR). To gain a comprehensive understanding of the sorption process, the effect of contact time, pH, concentration, and temperature was investigated. The adsorption capacity of chitosan powder for Cu(II), Pb(II), methylene blue (MB), and crystal violet (CV) was subsequently determined as follows: 99, 75, 98, and 80%, respectively. In addition, the adsorption capacity of chitosan hydrogel for Cu(II), Pb(II), MB, and CV was as follows: 85, 95, 85, and 98%, respectively. The experimental data obtained were analyzed using the Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. The isotherm study revealed that the adsorption equilibrium is well fitted to the Freundlich isotherm (R2 = 0.998), and the sorption capacity of both chitosan powder and hydrogel was found to be exceptionally high (approximately 98%) with the adsorbent favoring multilayer adsorption. Besides, Dubinin has given an indication that the sorption process was dominated by Van der Waals physical forces at all studied temperatures.

Statistical design and optimization of nano-transfersomes based chitosan gel for transdermal delivery of cefepime

OBJECTIVES

This research aimed to overcome challenges posed by cefepime excessive elimination rate and poor patient compliance by developing transdermal delivery system using nano-transfersomes based chitosan gel.

METHODS

Rotary evaporation-sonication method and the Box-Behnken model were used to prepare cefepime loaded nano-transfersomes (CPE-NTFs). The physiochemical characterization of CPE-NTFs were analyzed including DLS, deformability index, DSC and antimicrobial study. Optimized CPE-NTFs loaded into chitosan gel and appropriately characterized. In vitro release, ex vivo and in vivo studies were performed.

RESULTS

The CPE-NTFs were physically stable with particle size 222.6 ± 1.8 nm, polydispersity index 0.163 ± 0.02, zeta potential -20.8 ± 0.1 mv, entrapment efficiency 81.4 ± 1.1% and deformability index 71 ± 0.2. DSC analysis confirmed successful drug loading and thermal stability. FTIR analysis showed no chemical interaction among the excipients of CPE-NTFs gel. The antibacterial activity demonstrated a remarkable reduction in the minimum inhibitory concentration of cefepime when incorporated into nano-transfersomes. CPE-NTFs based chitosan gel (CPE-NTFs gel) showed significant physicochemical properties. In vitro release studies exhibited sustained release behavior over 24 h, and ex vivo studies indicated enhanced permeation and retention compared to conventional cefepime gel. In vivo skin irritation studies confirmed CPE-NTFs gel was nonirritating and biocompatible for transdermal delivery.

CONCLUSION

This research showed nano-transfersomes based chitosan gel is a promising approach for cefepime transdermal delivery and provides sustained release of cefepime.

Antibacterial adhesive based on oxidized tannic acid-chitosan for rapid hemostasis

Currently, bacterial infections and bleeding interfere with wound healing, and multifunctional hydrogels with appropriate blood homeostasis, skin adhesion, and antibacterial activity are desirable. In this study, chitosan-based hydrogels were synthesized using oxidized tannic acid (OTA) and Fe3+ as cross-linkers (CS-OTA-Fe) by forming covalent, non-covalent, and metal coordination bonds between Fe3+ and OTA. Our results demonstrated that CS-OTA-Fe hydrogels showed antibacterial properties against Gram-positive bacteria (Staphylococcus aureus)and Gram-negative bacteria (Escherichia coli), low hemolysis rate (< 2 %), rapid blood clotting ability, in vitro (< 2 min), and in vivo (90 s) in mouse liver bleeding. Additionally, increasing the chitosan concentration from 3 wt% to 4.5 wt% enhanced cross-linking in the network, leading to a significant improvement in the strength (from 106 ± 8 kPa to 168 ± 12 kPa) and compressive modulus (from 50 ± 9 kPa to 102 ± 14 kPa) of hydrogels. Moreover, CS-OTA-Fe hydrogels revealed significant adhesive strength (87 ± 8 kPa) to the cow's skin tissue and cytocompatibility against L929 fibroblasts. Overall, multifunctional CS-OTA-Fe hydrogels with tunable mechanical properties, excellent tissue adhesive, self-healing ability, good cytocompatibility, and fast hemostasis and antibacterial properties could be promising candidates for biomedical applications.

Nanocellulose-assisted mechanically tough hydrogel platforms for sustained drug delivery

The controlled delivery of the desired bioactive molecules is required to achieve the maximum therapeutic effects with minimum side effects. Biopolymer-based hydrogels are ideal platforms for delivering the desired molecules owing to their superior biocompatibility, biodegradability, and low-immune response. However, the prolonged delivery of the drugs through biopolymer-based hydrogels is restricted due to their weak mechanical stability. We developed mechanically tough and biocompatible hydrogels to address these limitations using carboxymethyl chitosan, sodium alginate, and nanocellulose for sustained drug delivery. The hydrogels were cross-linked through calcium ions to enhance their mechanical strength. Nanocellulose-added hydrogels exhibited improved mechanical strength (Young's modulus; 23.36 → 30.7 kPa, Toughness; 1.39 → 5.65 MJm-3) than pure hydrogels. The composite hydrogels demonstrated increased recovery potential (66.9 → 84.5 %) due to the rapid reformation of damaged polymeric networks. The hydrogels were stable in an aqueous medium and demonstrated reduced swelling potential. The hydrogels have no adverse effects on embryonic murine fibroblast (3 T3), showing their biocompatibility. No bacterial growth was observed in hydrogels-treated groups, indicating their antibacterial characteristics. The sustained drug released was observed from nanocellulose-assisted hydrogel scaffolds compared to the pure polymer hydrogel scaffold. Thus, hydrogels have potential and could be used as a sustained drug carrier.

Counter-intuitive discovery in the formulation of poorly water-soluble drugs: Amorphous small-molecule gels

Amorphous strategies have been extensively used in improving the dissolution of insoluble drugs for decades due to their high free energy. However, the formation of amorphous small-molecule gels (ASMGs) presents a counter-intuitive discovery that significantly limits their practical application. Recently, ASMGs have garnered attention because of their noncovalent structures, excellent biodegradability, and significant potential in various drug delivery systems in the pharmaceutical field. Hence, a comprehensive review is necessary to contribute to a better understanding of recent advances in ASMGs. This review aimed to introduce the main formation mechanisms, summarize possible influencing factors, generalize unique properties, outline elimination strategies, and discuss clinical application potential with preclinical cases of ASMGs. Moreover, few ASMGs are advanced to clinical stages. Intensive clinical research is needed for further development. We hope that this review can provide more efficient and rational guidance for exploring further clinical applications of ASMGs.

A novel injectable thermo/photo dual-crosslinking hydrogel based on modified chitosan for fast sealing open globe injury

Open globe injuries (OGIs) demand immediate attention to prevent further complications and improve vision prognosis. Herein, we developed a thermo/photo dual-crosslinking injectable hydrogel, HBC_m_Arg, for rapidly sealing OGIs in emergency ophthalmic cases. HBC_m_Arg was prepared with arginine and methacrylic anhydride modified hydroxybutyl chitosan (HBC). HBC_m_Arg was initially in liquid form at 25 °C, enabling easy injection at the injury site. After reaching the ocular surface temperature, it underwent reversible heat-induced gelation to achieve in situ transformation. Further, HBC_m_Arg was capable of rapid photocrosslinking under UV light, forming a dual network structure to bolster mechanical strength, thereby facilitating effective OGI closure. Biocompatibility assessments, including in vitro studies with three ocular cell types and in vivo experiments on rabbit eyes, confirmed the safety profile of HBC_m_Arg. Ex vivo and in vivo burst pressure tests demonstrated the hydrogel's ability to promptly restore intraocular pressure and withstand elevated pressures, underscoring its potential for OGI stabilization. Additionally, the suitable degradation of HBC_m_Arg within ocular tissues, coupled with its stability in ex vivo assessments, presented a delicate balance between stability and biodegradability. In conclusion, HBC_m_Arg holds promise for improving emergency ophthalmic care by providing a rapid, effective, and safe way to seal OGIs in critical situations.

Functionalized chitosan hydrogel promotes osseointegration at the interface of3D printed titanium alloy scaffolds

Autogenous bone transplantation is a prevalent clinical method for addressing bone defects. However, the limited availability of donor bone and the morbidity associated with bone harvesting have propelled the search for suitable bone substitutes. Bio-inspired scaffolds, particularly those fabricated using electron beam melting (EBM) deposition technology, have emerged as a significant advancement in this field. These 3D-printed titanium alloy scaffolds are celebrated for their outstanding biocompatibility and favorable elastic modulus. Thermosensitive chitosan hydrogel, which transitions from liquid to solid at body temperature, serves as a popular carrier in bone tissue engineering. Icariin (ICA), known for its efficacy in promoting osteoblast differentiation from bone marrow mesenchymal stem cells (BMSCs), plays a crucial role in this context. We developed a system combining a 3D-printed titanium alloy with a thermosensitive chitosan hydrogel, capable of local bone regeneration and integration through ICA delivery. Our in vitro findings reveal that this system can gradually release ICA, demonstrating excellent biocompatibility while fostering BMSC proliferation and osteogenic differentiation. Immunohistochemistry and Micro-CT analyses further confirm the effectiveness of the system in accelerating in vivo bone regeneration and enhancing osseointegration. This composite system lays a significant theoretical foundation for advancing local bone regeneration and integration.

Synthetic and biopolymers-based antimicrobial hybrid hydrogels: a focused review

The constantly accelerating occurrence of microbial infections and their antibiotic resistance has spurred advancement in the field of material sciences and has guided the development of novel materials with anti-bacterial properties. To address the clinical exigencies, the material of choice should be biodegradable, biocompatible, and able to offer prolonged antibacterial effects. As an attractive option, hydrogels have been explored globally as a potent biomaterial platform that can furnish essential antibacterial attributes owing to its three-dimensional (3D) hydrophilic polymeric network, adequate biocompatibility, and cellular adhesion. The current review focuses on the utilization of different antimicrobial hydrogels based on their sources (natural and synthetic). Further, the review also highlights the strategies for the generation of hydrogels with their advantages and disadvantages and their applications in different biomedical fields. Finally, the prospects in the development of hydrogels-based antimicrobial biomaterials are discussed along with some key challenges encountered during their development and clinical translation.

Designing a bi-layer multifunctional hydrogel patch based on polyvinyl alcohol, quaternized chitosan and gallic acid for abdominal wall defect repair

In abdominal wall defect repair, surgical site infection (SSI) remains the primary cause of failure, while complications like visceral adhesions present significant challenges following patch implantation. We designed a Janus multifunctional hydrogel patch (JMP) with antibacterial, anti-inflammatory, and anti-adhesive properties. The patch comprises two distinct layers: a pro-healing layer and an anti-adhesion layer. The pro-healing layer was created by a simple mixture of polyvinyl alcohol (PVA), quaternized chitosan (QCS), and gallic acid (GA), crosslinked to form PVA/QCS/GA (PQG) hydrogels through GA's self-assembly effect and hydrogen bonding. Additionally, the PVA anti-adhesive layer was constructed using a drying-assisted salting method, providing a smooth and dense physical barrier to prevent visceral adhesion while offering essential mechanical support to the abdominal wall. The hydrogel patch demonstrates widely adjustable mechanical properties, exceptional biocompatibility, and potent antimicrobial properties, along with a sustained and stable release of antioxidants. In rat models of skin and abdominal wall defects, the JMP effectively promoted tissue healing by controlling infection, inhibiting inflammation, stimulating neovascularization, and successfully preventing the formation of visceral adhesions. These compelling results highlight the JMP's potential to improve the success rate of abdominal wall defect repair and reduce surgical complications.

Effect of different crosslinking agents on hybrid chitosan/collagen hydrogels for potential tissue engineering applications

Tissue engineering (TE) demands scaffolds that have the necessary resistance to withstand the mechanical stresses once implanted in our body, as well as excellent biocompatibility. Hydrogels are postulated as interesting materials for this purpose, especially those made from biopolymers. In this study, the microstructure and rheological performance, as well as functional and biological properties of chitosan and collagen hydrogels (CH/CG) crosslinked with different coupling agents, both natural such as d-Fructose (F), genipin (G) and transglutaminase (T) and synthetic, using a combination of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride with N-hydroxysuccinimide (EDC/NHS) will be assessed. FTIR tests were carried out to determine if the proposed crosslinking reactions for each crosslinking agent occurred as expected, obtaining positive results in this aspect. Regarding the characterization of the properties of each system, two main trends were observed, from which it could be established that crosslinking with G and EDC-NHS turned out to be more effective and beneficial than with the other two crosslinking agents, producing significant improvements with respect to the base CH/CG hydrogel. In addition, in vitro tests demonstrated the potential application in TE of these systems, especially for those crosslinked with G, T and EDC-NHS.

Multifunctional chitosan-based lanthanide luminescent hydrogel with stretchability, adhesion, self-healing, color tunability and antibacterial ability

Lanthanide luminescent hydrogels have broad application prospects in various fields. However, most of lanthanide hydrogels possess relatively simple functions, which is not conducive to practical applications. Therefore, it is becoming increasingly urgent to develop multifunctional hydrogels. Herein, a multifunctional chitosan-based lanthanide luminescent hydrogel with ultra-stretchability, multi-adhesion, excellent self-healing, emission color tunability, and good antibacterial ability was prepared by a simple one-step free radical polymerization. In this work, our designed lanthanide complexes [Ln(4-VDPA)3] contain three reaction sites, which can be copolymerized with N-[tris(hydroxymethyl) methyl] acrylamide (THMA), acrylamide (AM), and diacryloyl poly(ethylene glycol) (DPEG) to form the first chemical crosslinking network, while hydroxypropyltrimethyl ammonium chloride chitosan (HACC) interacts with the hydroxyl and amino groups derived from the chemical crosslinking network through hydrogen bonds to form the second physical crosslinking network. The structure of the double network as well as the dynamic hydrogen bond and lanthanide coordination endow the hydrogel with excellent stretchability, adhesion and self-healing properties. Moreover, the introduction of lanthanide complexes and chitosan makes the hydrogel exhibit outstanding luminescence and antibacterial performances. This research not only realizes the simple synthesis of multifunctional luminescent hydrogels, but also provides a new idea for the fabrication of biomass-based hydrogels as intelligent and sustainable materials.

Polysaccharides as a Hydrophilic Building Block of Amphiphilic Block Copolymers for the Conception of Nanocarriers

Polysaccharides are gaining increasing attention for their relevance in the production of sustainable materials. In the domain of biomaterials, polysaccharides play an important role as hydrophilic components in the design of amphiphilic block copolymers for the development of drug delivery systems, in particular nanocarriers due to their outstanding biocompatibility, biodegradability, and structural versatility. The presence of a reducing end in polysaccharide chains allows for the synthesis of polysaccharide-based block copolymers. Compared with polysaccharide-based graft copolymers, the structure of block copolymers can be more precisely controlled. In this review, the synthesis methods of polysaccharide-based amphiphilic block copolymers are discussed in detail, taking into consideration the structural characteristics of polysaccharides. Various synthetic approaches, including reductive amination, oxime ligation, and other chain-end modification reactions, are explored. This review also focuses on the advantages of polysaccharides as hydrophilic blocks in polymeric nanocarriers. The structure and unique properties of different polysaccharides such as cellulose, hyaluronic acid, chitosan, alginate, and dextran are described along with examples of their applications as hydrophilic segments in the synthesis of amphiphilic copolymers to construct nanocarriers for sustained drug delivery.

Hybrid Hydrogels for Immunoregulation and Proangiogenesis through Mild Heat Stimulation to Accelerate Whole-Process Diabetic Wound Healing

Intense and persistent oxidative stress, excessive inflammation, and impaired angiogenesis severely hinder diabetic wound healing. Bioactive hydrogel dressings with immunoregulatory and proangiogenic properties have great promise in treating diabetic wounds. However, the therapeutic effects of dressings always depend on drugs with side effects, expensive cytokines, and cell therapies. Herein, a novel dynamic borate-bonds crosslinked hybrid multifunctional hydrogel dressings with photothermal properties are developed to regulate the microenvironment of diabetic wound sites and accelerate the whole process of its healing without additional medication. The hydrogel is composed of phenylboronic acid-modified chitosan and hyaluronic acid (HA) crosslinked by tannic acid (TA) through borate bonds and Prussian blue nanoparticles (PBNPs) with photothermal response characteristics are embedded in the polymer networks. The results indicate hydrogels show inherent broad-spectrum antioxidative activities through the integrated interaction of borate bonds, TA, and PBNPs. Meanwhile, combined with the regulation of macrophage phenotype by HA, the inflammatory microenvironment of diabetic wounds is transformed. Moreover, the angiogenesis is then enhanced by the mild photothermal effect of PBNPs, followed by promoted epithelialization and collagen deposition. In summary, this hybrid hydrogel system accelerates all stages of wound repair through antioxidative stress, immunomodulation, and proangiogenesis, showing great potential applications in diabetic wound management.

A Comprehensive Review of Hydrogel-Based Drug Delivery Systems: Classification, Properties, Recent Trends, and Applications

As adaptable biomaterials, hydrogels have shown great promise in several industries, which include the delivery of drugs, engineering of tissues, biosensing, and regenerative medicine. These hydrophilic polymer three-dimensional networks have special qualities like increased content of water, soft, flexible nature, as well as biocompatibility, which makes it excellent candidates for simulating the extracellular matrix and promoting cell development and tissue regeneration. With an emphasis on their design concepts, synthesis processes, and characterization procedures, this review paper offers a thorough overview of hydrogels. It covers the various hydrogel material types, such as natural polymers, synthetic polymers, and hybrid hydrogels, as well as their unique characteristics and uses. The improvements in hydrogel-based platforms for controlled drug delivery are examined. It also looks at recent advances in bioprinting methods that use hydrogels to create intricate tissue constructions with exquisite spatial control. The performance of hydrogels is explored through several variables, including mechanical properties, degradation behaviour, and biological interactions, with a focus on the significance of customizing hydrogel qualities for particular applications. This review paper also offers insights into future directions in hydrogel research, including those that promise to advance the discipline, such as stimuli-responsive hydrogels, self-healing hydrogels, and bioactive hydrogels. Generally, the objective of this review paper is to provide readers with a detailed grasp of hydrogels and all of their potential uses, making it an invaluable tool for scientists and researchers studying biomaterials and tissue engineering.

Desert date seed extract-loaded chitosan nanoparticles ameliorate hyperglycemia and insulin deficiency through the reduction in oxidative stress and inflammation

Plants represents a huge source of bioactive materials that have been used since the old times in the treatment of many diseases. Balanites aegyptiaca, known as desert date, has been used in treatment of fever, diabetes and bacterial infection. Desert dates contains a hard seed that resembles 50-60% of the fruit. The seed extract contains many fatty acids, amino acids and other bioactive materials that gives the extract its antioxidant and anti-inflammatory properties. The study aimed to use Balanites seed extract-loaded chitosan nanoparticles (SeEx-C NPs) for the treatment of streptozotocin (STZ)-induced diabetes in male Sprague Dawley rats. Animals were divided into two main divisions (healthy and diabetic rats). Each division contained seven groups (5 rats/group): control untreated group I, SeEx treated group II and group III (10 and 20 mg/kg b.w., respectively), C NPs treated group IV and group V (10 and 20 mg/kg b.w., respectively) and SeEx-C NPs treated group VI and group VII (10 and 20 mg/kg b.w., respectively). The therapeutical effects of SeEx-C NPs were evaluated through biochemical and immunological assessments in rats' pancreases. The results showed that SeEx-C NPs (10 and 20 mg/kg b.w.) reduced the oxidative stress and inflammation in rats' pancreases allowing the islets neogenesis. The loading of SeEx on C NPs allowed the delivery of fatty acids (oleic, lauric and myristic acid), amino acids (lysine, leucine, phenylalanine and valine) and minerals to pancreatic beta-cells in a sustainable manner. SeEx-C NPs administration successfully increased insulin secretion, allowed pancreatic islets neogenesis and reduced oxidative stress and inflammation.

Advances in chitosan and chitosan derivatives for biomedical applications in tissue engineering: An updated review

In recent years, chitosan (CS) has received much attention as a functional biopolymer for various applications, especially in the biomedical field. It is a natural polysaccharide created by the chemical deacetylation of chitin (CT) that is nontoxic, biocompatible, and biodegradable. This natural polymer is difficult to process; however, chemical modification of the CS backbone allows improved use of functional derivatives. CS and its derivatives are used to prepare hydrogels, membranes, scaffolds, fibers, foams, and sponges, primarily for regenerative medicine. Tissue engineering (TE), currently one of the fastest-growing fields in the life sciences, primarily aims to restore or replace lost or damaged organs and tissues using supports that, combined with cells and biomolecules, generate new tissue. In this sense, the growing interest in the application of biomaterials based on CS and some of its derivatives is justifiable. This review aims to summarize the most important recent advances in developing biomaterials based on CS and its derivatives and to study their synthesis, characterization, and applications in the biomedical field, especially in the TE area.

Evaluation of the Potential of Chitosan Nanoparticles as a Delivery Vehicle for Gentamicin for the Treatment of Osteomyelitis

Chitosan nanoparticle delivery systems have the potential for enhancing bone healing and addressing osteomyelitis. The objective was to deliver antimicrobial agents capable of preventing or treating osteomyelitis. Each formulation was optimized to achieve desired characteristics in terms of size (ranging from 100 to 400 nm), PDI (less than 0.5), zeta potential (typically negative), and in vitro release profiles for gentamicin. Entrapment percentages varied with gentamicin ranging from 10% to 65%. The chitosan nanoparticles exhibited substantial antimicrobial efficacy, particularly against P. aeruginosa and MRSA, with zones of inhibition ranging from 13 to 24 mm and a complete reduction in colony forming units observed between 3 and 24 h. These chitosan nanoparticle formulations loaded with antimicrobials hold promise for addressing orthopedic complications.

Chitosan Hydrogel Dressing Loaded with Adipose Mesenchymal Stem Cell-Derived Exosomes Promotes Skin Full-Thickness Wound Repair

Cutaneous trauma repair is still a challenge in the clinic due to the scar formation and slow healing rate, especially for diabetic patients. Various drug-loading wound dressings have been explored to solve this problem. Mesenchymal stem cell (MSC)-derived exosomes have been considered as a potential cell-free drug because of their anti-inflammation function and tissue repair property that are comparable to that of MSCs. Herein, a composite wound dressing (Exo/Gel) consisting of the chitosan hydrogel and adipose MSC-derived exosome (ADMSC-Exo) was designed and fabricated by a physical mixing method to promote the skin full-thickness wound repair. The exosomes were slowly released from the Exo/Gel dressing with the degradation of the chitosan hydrogel. The Exo/Gel displayed enhanced cell migration and angiogenic properties in vitro. And the results in the rat skin wound model showed that the Exo/Gel could promote the regular collagen deposition, angiogenesis, and hair follicle mosaicism regeneration. These results proved that the hydrogel dressing with ADMSCs-derived exosomes can accelerate skin wound healing, which is a strategy for developing wound dressings.

Chitosan and Sodium Hyaluronate Hydrogels Supplemented with Bioglass for Bone Tissue Engineering

The aim of the study was to produce biocomposites based on chitosan and sodium hyaluronate hydrogels supplemented with bioglasses obtained under different conditions (temperature, time) and to perform an in vitro evaluation of their cytocompatibility using both indirect and direct methods. Furthermore, the release of ions from the composites and the microstructure of the biocomposites before and after incubation in simulated body fluid were assessed. Tests on extracts from bioglasses and hydrogel biocomposites were performed on A549 epithelial cells, while MG63 osteoblast-like cells were tested in direct contact with the developed biomaterials. The immune response induced by the biomaterials was also evaluated. The experiments were carried out on both unstimulated and lipopolysaccharide (LPS) endotoxin-stimulated human peripheral blood cells in the presence of extracts of the biocomposites and their components. Extracts of the materials produced do not exhibit toxic effects on A549 cells, and do not increase the production of proinflammatory cytokines tumour necrosis factor alpha (TNF-α) and interleukin (IL-6) by blood cells in vitro. In direct contact with MG63 osteoblast-like cells, biocomposites containing the reference bioglass and those containing SrO are more cytocompatible than biocomposites with ZnO-doped bioglass. Using two testing approaches, the effects both of the potentially toxic agents released and of the surface of the tested materials on the cell condition were assessed. The results pave the way for the development of highly porous hydrogel-bioglass composite scaffolds for bone tissue engineering.

Chitosan-Based Biomaterial in Wound Healing: A Review

Wound healing is an evolving and intricate technique that is vital to the restoration of tissue integrity and function. Over the past few decades, chitosan a biopolymer derived from chitin, became known as an emerging biomaterial in the field of healing wounds due to its distinctive characteristics including biocompatibility, biodegradability, affinity to biomolecules, and wound-healing activity. This natural polymer exhibits excellent healing capabilities by accelerating the development of new skin cells, reducing inflammation, and preventing infections. Due to its distinct biochemical characteristics and innate antibacterial activity, chitosan has been extensively researched as an antibacterial wound dressing. Chronic wounds, such as diabetic ulcers and liver disease, are a growing medical problem. Chitosan-based biomaterials are a promising solution in the domain of wound care. The article analyzes the depth of chitosan-based biomaterials and their impact on wound healing and also the methods to enhance the advantages of chitosan by incorporating bioactive compounds. This literature review is aimed to improve the understanding and knowledge about biomaterials and their use in wound healing.

Application of Chitosan-Based Hydrogel in Promoting Wound Healing: A Review

Chitosan is a linear polyelectrolyte with active hydroxyl and amino groups that can be made into chitosan-based hydrogels by different cross-linking methods. Chitosan-based hydrogels also have a three-dimensional network of hydrogels, which can accommodate a large number of aqueous solvents and biofluids. CS, as an ideal drug-carrying material, can effectively encapsulate and protect drugs and has the advantages of being nontoxic, biocompatible, and biodegradable. These advantages make it an ideal material for the preparation of functional hydrogels that can act as wound dressings for skin injuries. This review reports the role of chitosan-based hydrogels in promoting skin repair in the context of the mechanisms involved in skin injury repair. Chitosan-based hydrogels were found to promote skin repair at different process stages. Various functional chitosan-based hydrogels are also discussed.

An antibacterial nanoclay- and chitosan-based quad composite with controlled drug release for infected skin wound healing

Microbial infections of surgical sites and other wounds represent a major impediment for patients. Multifunctional low-cost dressings promoting tissue reparation while preventing infections are of great interest to medical professionals. Here, clay-based laponite nanodiscs (LAP) were loaded with the antibacterial drug kanamycin (KANA) before being embedded into a poly(lactic-co-glycolic acid) (PLGA) membrane and coated with the biopolymer chitosan (CS). Results indicated that these biocompatible materials combined the excellent capacity of LAP for controlled drug release with the mechanical robustness of PLGA and the antibacterial properties of CS as well as its hydrophilicity to form a composite highly suitable as an infection-preventing wound dressing. In vitro, PLGA/LAP/KANA/CS released drugs in a sustainable manner over 30 d, completely inhibited the growth of infectious bacteria, prompted the adhesion fibroblasts, and accelerated their proliferation 1.3 times. In vivo, the composite enabled the fast healing of infected full-thickness skin wounds with a 96.19 % contraction after 14 d. During the healing process, PLGA/LAP/KANA/CS stimulated re-epithelization, reduced inflammation, and promoted both angiogenesis and the formation of dense collagen fibers with an excellent final collagen volume ratio of 89.27 %. Thus, multifunctional PLGA/LAP/KANA/CS made of low-cost components demonstrated its potential for the treatment of infected skin wounds.

Enhancing the Properties of Self-Healing Gelatin Alginate Hydrogels by Hofmeister Mediated Electrostatic Effect

The cross-linker-free hydrogels have gained attention due to their lack of need for chemically modified polymers, resulting in better biocompatibility. The hydrogel properties can be enhanced by altering physical forces such as electrostatics and H-bonds. Tuning the physical interactions between polymers, salts, and plasticisers can unlock new horizons in material properties. This article examines four different salts and mixtures to determine their impact on gelatin-alginate biomaterial design. Drug release, swelling, and rheological properties are represented using a 3-D plot, and optimum samples are identified. It is concluded that kosmotropes yield better release and swelling results than chaotropes. The physical interactions of these salts with polymers are explained using DLS and FTIR/ATR studies, and these findings are corroborated with release, swelling, and rheological analyses. Another aspect of the biomaterial, self-healing property, is also considered. A 3-D plot is prepared using release kinetics, gel strength, and recovery percentage (three important factors for self-healing hydrogels). Chaotropes are identified as better candidates for self-healing behaviour. However, when considering gel strength, release, and self-healing, kosmotropes are favourable. Hence, different salts can be selected based on the desired application for hydrogels. It is also concluded that electrostatic forces hinder the formation of H-bonds between polymer chains.

Ultra-stretchable and conductive polyacrylamide/carboxymethyl chitosan composite hydrogels with low modulus and fast self-recoverability as flexible strain sensors

There is a great demand for the fabrication of soft electronics using hydrogels due to their biomimetic structures and good flexibility. However, conventional hydrogels have poor mechanical properties, which restricts their applications as stretchable sensors. Herein, a facile one-step strategy is proposed to fabricate tough and conductive hydrogels by making use of the graftability of carboxymethyl chitosan without extra conductive matter and crosslinking agent. The obtained polyacrylamide/carboxymethyl chitosan composite hydrogels possess outstanding transmittance and excellent mechanical performances, with tensile breaking stress of 630 kPa, breaking strain of 4560 %, toughness of 8490 kJ/m3. These hydrogels have low modulus of 5-20 kPa, fast recoverability after unloading, high conductivity of ∼0.85 S/m without the addition of other conductive substances and good biocompatibility. The ionic conductivity of the gels originates from the counterions of carboxymethyl chitosan, affording the hydrogels as resistive-type sensors. The resultant hydrogel sensors demonstrate a broad strain window (0.12-1500 %), excellent linear response, high sensitivity with the gauge factor reaching 11.72, and great durability, capable of monitoring diverse human motions. This work provides a new strategy to develop stretchable conductive hydrogels with promising applications in the fields of artificial intelligence and flexible electronics.

Preparation and evaluation of Angelica sinensis polysaccharide-modified chitosan sponge for acute liver injury protection

In this study, a porous sponge material was formed by physically mixing chitosan (CS) and Angelica sinensis polysaccharide (ASP). After removing the water by freeze-drying, the CS/ASP sponge was obtained. The prepared sponges exhibited excellent swelling properties, thermal stability and biocompatibility as well as improvements over the insufficient mechanical properties of pure chitosan sponges. Notably, the ASP released from the CS/ASP sponge could be effectively absorbed by the liver, which endowed the CS/ASP sponge with effective liver-protective effects against CCl4-induced acute liver injury; these protective effects surpassed those of both blank CS and CS/Dextran sponges. The underlying protective mechanism may involve the activation of the Nrf2-mediated antioxidant signaling pathway and the inhibition of hepatocyte apoptosis. Understanding CS/ASP sponges may provide new insights and inspire new methods for the clinical application of ASP. At the same time, we hope to suggest future directions for the development of polysaccharide preparations.

Recent advances in double network hydrogels based on naturally-derived polymers: synthesis, properties, and biological applications

Hydrogels composed of naturally-derived biopolymers have garnered significant research interest due to the bioavailability and biocompatibility of starting materials. However, translating these advantages to practical use is challenged by limitations of mechanical properties and stability of the resulting materials. The development of double network (DN) hydrogels has led to greatly enhanced mechanical properties and shows promise toward broadening the applications of conventional synthetic or natural hydrogels. This review highlights recently developed protein-based and polysaccharide-based DN hydrogels. For each biopolymer, we focus on a subset of DN hydrogels centered around a theme related to synthetic design or applications. Network structures and crosslinking mechanisms that endow enhanced mechanical properties and performance to the materials are discussed. Important applications, including tissue engineering, drug delivery, bioadhesives, wound healing, and wearable sensors, that arise from the inherent properties of the natural polymer or its combination with other materials are also emphasized. Finally, we discuss ongoing challenges to stimulate the discovery of new design principles for the future of DN hydrogels based on naturally-derived polymers for biological applications.

An injectable photopolymerizable chitosan hydrogel doped anti-inflammatory peptide for long-lasting periodontal pocket delivery and periodontitis therapy

Periodontitis is a common chronic inflammatory disease caused by plaque that leads to alveolar bone resorption and tooth loss. Inflammation control and achieving better tissue repair are the key to periodontitis treatment. In this study, human β-Defensin 1 short motif Pep-B with inflammation inhibition and differentiation regulation properties, is firstly used in the treatment of periodontitis, and an injectable photopolymerizable Pep-B/chitosan methacryloyl composite hydrogel (CMSA/Pep-B) is constructed. We confirm that Pep-B improves inflammation, and restores osteogenic behavior and function of injured stem cells. CMSA/Pep-B has good injectability, fluidity and photopolymerizability, and can sustainably release Pep-B to maintain drug concentration in periodontal pockets. Furthermore, animal experiments showed that CMSA/Pep-B significantly ameliorated the inflammation of the periodontium and reduced the alveolar bone loss by decreasing inflammatory infiltration, osteoclast formation and collagen destruction. In conclusion, CMSA/Pep-B is envisaged to be a novel bioactive material or therapeutic drug for treating periodontitis.

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.

Photodynamic Therapy Directed to Melanoma Skin Cancer by Thermosensitive Hydrogel Containing Chlorophyll A

Melanoma, a severe form of skin cancer intricately linked to genetic and environmental factors, is predicted to reach 100,000 new cases worldwide by 2040, underscoring the need for effective and safe treatment options. In this study, we assessed the efficacy of a photosensitizer called Chlorophyll A (Chl-A) incorporated into hydrogels (HGs) made of chitosan (CS) and poloxamer 407 (P407) for Photodynamic Therapy (PDT) against the murine melanoma cell line B16-F10. The HG was evaluated through various tests, including rheological studies, SEM, and ATR-FTIR, along with cell viability assays. The CS- and P407-based HGs effectively released Chl-A and possessed the necessary properties for topical application. The photodynamic activity of the HG containing Chl-A was evaluated in vitro, demonstrating high therapeutic potential, with an IC50 of 25.99 µM-an appealing result when compared to studies in the literature reporting an IC50 of 173.8 µM for cisplatin, used as a positive control drug. The developed formulation of CS and P407-based HG, serving as a thermosensitive system for topical applications, successfully controlled the release of Chl-A. In vitro cell studies associated with PDT exhibited potential against the melanoma cell line.

Cellulase-immobilized chitosan-coated magnetic nanoparticles for saccharification of lignocellulosic biomass

Devising and consolidating cost-effective and greener technologies for sustainable energy production pertain to some of the most pressing needs of the present times. Bioconversion of abundantly available lignocellulosic materials into fermentable sugars to produce biofuels involves the cost-extensive requirement of hydrolytic enzymes called cellulases. Cellulases are highly selective and eco-friendly biocatalysts responsible for deconstruction of complex polysaccharides into simple sugars. Currently, immobilization of cellulases is being carried out on magnetic nanoparticles functionalized with suitable biopolymers such as chitosan. Chitosan, a biocompatible polymer, exhibits high surface area, chemical/thermal stability, functionality, and reusability. The chitosan-functionalized magnetic nanocomposites (Ch-MNCs) present a nanobiocatalytic system that enables easy retrieval, separation, and recycling of cellulases, thereby offering a cost-effective and sustainable approach for biomass hydrolysis. These functional nanostructures show enormous potential owing to certain physicochemical and structural features that have been discussed in a comprehensive manner in this review. It provides an insight into the synthesis, immobilization, and application of cellulase immobilized Ch-MNCs for biomass hydrolysis. This review aims to bridge the gap between sustainable utilization and economic viability of employing replenishable agro-residues for cellulosic ethanol production by incorporating the recently emerging nanocomposite immobilization approach.

Advancements in Composite Materials and Their Expanding Role in Biomedical Applications

The synthesis of a Ni-doped ZnO nanocomposite incorporating chitosan (CS/Ni-doped ZnO) was achieved via a precipitation method, followed by annealing at 250 °C. This study comprehensively examined the nanocomposite's structural, functional, morphological, and porosity properties using various analytical techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high-resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analysis. The presence of chitosan (CS) and nickel (Ni) within the nanocomposite, along with their influence on reducing the band gap of ZnO particles and enhancing the generation of electron-hole pairs, was confirmed using UV-visible near-infrared spectroscopy (UV-vis-NIR). The electrochemical properties of the CS/Ni-doped ZnO nanocomposite were investigated via electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) by utilizing a phosphate buffer solution with a pH of 6, which closely resembled the typical pH of bacterial cell walls. Finally, the prepared CS/Ni-doped ZnO nanocomposite was evaluated for its antibacterial and anticancer activities. The results demonstrated the highest inhibition of bacterial growth in P. vulgaris, whereas the lowest inhibition was found in S. aureus across various concentrations, thus highlighting its potential in antimicrobial applications. The cytotoxicity of CS/Ni-doped ZnO nanocomposites demonstrated remarkable effects with a half-maximum inhibitory concentration of approximately 80 ± 0.23 µg mL-1 against MCF-7 breast cancer cell lines, following a dose-dependent manner.

A New and Rapid HPLC Method to Determine the Degree of Deacetylation of Glutaraldehyde-Cross-Linked Chitosan

Chitosan is a linear biopolymer composed of D-glucosamine and N-acetylglucosamine units. The percentage of D-glucosamine in the polymeric chain can vary from one sample to another and is expressed as the degree of deacetylation (DDA). Since this parameter has an impact on many properties, its determination is often critical, and potentiometric titration is a common analytical technique to measure the DDA. Cross-linking with glutaraldehyde is one of the most explored modifications of chitosan; however, the determination of the DDA for the resulting reticulated chitosan resins can be challenging. In this paper, we report a new, rapid, and efficient method to determine the DDA of glutaraldehyde-cross-linked chitosan resins via HPLC. This method relies on the use of 2,4-dinitrophenylhydrazine (DNPH) as a derivatizing agent to measure the level of reticulation of the polymer (LR) after the reticulation step. In this study, we prepare three calibration curves (with an R2 value over 0.92) for three series of reticulated polymers covering a large range of reticulation levels to demonstrate that a correlation can be established between the LR established via HPLC and the DDA obtained via titration. The polymers are derived from three different chitosan starting materials. These standard calibration curves are now used on a routine basis in our lab, and the HPLC method has allowed us to change our DDA analysis time from 20 h to 5 min.

Double network structure via ionic bond and covalent bond of carboxymethyl chitosan and poly(ethylene glycol): Factors affecting hydrogel formation

The factors were studied that affect the formation of DN hydrogel, which was prepared using a water-based, environmental-friendly system. The DN hydrogel was designed and prepared based on a cross-linked, polysaccharide-based, polymer carboxymethyl chitosan (CMCS) via an ionic crosslinking reaction for the first network structure. UV irradiation created a radical crosslinking reaction of poly(ethylene glycol) from a double bond at the chain end for the second network structure. It was found that the optimum hydrogel was produced using 9.5 %v/v of 1000PEGGMA, CMCS 5%w/v, and CaCl₂ 3%w/v. The results showed the highest percentage of the gel fraction was 87.84 % and the hydrogel was stable based on its rheological properties. Factors affecting the hydrogel formation were the concentration and molecular weight of PEGGMA and the concentrations of CMCS and calcium chloride (CaCl₂). The DN hydrogel had bioactivity due to its octacalcium phosphate (OCP) hydroxyapatite crystal form. In addition, the composite DN scaffold with a conductive polymer of chitosan-grafted-polyaniline (CS-g-PANI) had conduction of 2.33 × 10^-5 S/cm when the concentration of CS-g-PANI was 3 mg/ml, confirming the semi-conductive nature of the material. All the results indicated that DN hydrogel could be a candidate to apply in tissue-engineering applications.

Genipin crosslinked porous chitosan beads as robust supports for β-galactosidase immobilization: Characterization, stability, and bioprocessing potential

This study aimed to modify the porosity of chitosan beads using Na2CO3 as a porogen agent and to crosslink them with genipin for the immobilization of β-galactosidase from Aspergillus oryzae. Immobilization was performed under four different pH conditions (4.5, 6.0, 7.5, and 9.0), resulting in biocatalysts named B4, B6, B7, and B9, respectively. The immobilized enzymes were characterized for immobilization parameters and stability, including thermal, pH, storage, and operational stability. The optimal conditions for the support were determined as 50 mM Na2CO3. The biocatalyst exhibited nearly 100 % retention of initial activity after 5 h of incubation at different pH conditions and showed improved thermal stability compared to the free enzyme across all pH conditions. After 50 cycles of lactose hydrolysis, all biocatalysts retained at least 71 % of their initial activity, with B6 retaining nearly 100 %. Scanning electron microscopy revealed structural modifications, particularly in B4, leading to weakened support structure after reuse. Continuous lactose hydrolysis showed increased productivity from 41.3 to 48.1 g L-1 h-1 for B6, with 78.1 % retention of initial capacity. All biocatalysts retained >95 % activity when stored at 4 °C for 20 weeks, highlighting their suitability for enzyme immobilization in continuous and discontinuous bioprocesses.

A general route to strong, conductive and antibacterial curdlan-based purely natural eutectohydrogels with self-assembled layer-by-layer network structure

To promote the application extension of curdlan from food industry- dominant to advanced flexible biomaterials, a novel group of purely natural curdlan gels with noticeable performance was developed through a simple heating-cooling approach, i.e., heating the dispersion of pristine curdlan in mixed acidic natural deep eutectic solvents (NADESs) and water at 60-90 °C, and cooling at ambient temperature. The NADESs employed are composed of choline chloride and natural organic acids (lactic acid as the representative). The as-developed gels (called eutectohydrogels) are not only compressible and stretchable but conductive, which traditional curdlan hydrogels are not attainable. The compressive stress at 90 % strain exceeds 2.00 ± 0.03 MPa, the tensile strength and fracture elongation reach 0.131 ± 0.002 MPa and 300 ± 9 % respectively, attributed to the distinctive, reciprocally linked self-assembled layer-by-layer network structure formed during gelation. An electric conductivity up to 2.22 ± 0.04 S‧m^-1 is achieved. The excellent mechanics and conductivity confer them good strain-sensing behavior. Additionally, the eutectohydrogels display high antibacterial activity against S. aureus (a model Gram-positive bacterium) and E. coli (a model Gram-negative bacterium). The outstanding comprehensive performance together with the purely natural attribute makes them broad application prospects in biomedical fields like flexible bioelectronics.

Chitosan-Based Self-Healing Hydrogel: From Fabrication to Biomedical Application

Biocompatible self-healing hydrogels are new-generation smart soft materials that hold great promise in biomedical fields. Chitosan-based self-healing hydrogels, mainly prepared via dynamic imine bonds, have attracted broad attention due to their mild preparation conditions, excellent biocompatibility, and self-recovery ability under a physiological environment. In this review, we present a comprehensive overview of the design and fabrication of chitosan-based self-healing hydrogels, and summarize their biomedical applications in tissue regeneration, customized drug delivery, smart biosensors, and three/four dimensional (3D/4D) printing. Finally, we will discuss the challenges and future perspectives for the development of chitosan-based self-healing hydrogels in the biomedical field.

A Cu@ZIF-8 encapsulated antibacterial and angiogenic microneedle array for promoting wound healing

Skin wounds caused by external injuries remain a serious challenge in clinical practice. Wound dressings that are antibacterial, pro-angiogenic, and have potent regeneration capacities are highly desirable for wound healing. In this study, a minimally invasive and wound-friendly Cu@ZIF-8 encapsulated PEGDA/CMCS microneedle (MN) array was fabricated using the molding method to promote wound healing. The MNs had good biocompatibility, excellent mechanical strength, as well as strong antibacterial properties and pro-angiogenic effects. When incubated with H2O2, Cu@ZIF-8 nanoparticles generated reactive oxygen species, which contributed to their antibacterial properties. Due to the oxidative stress of the cupric ions released from Cu@ZIF-8 and the anti-bacterial capability of the PEGDA/CMCS hydrogel scaffold, such an MN array presents excellent antibacterial activity. Moreover, with the continuous release of Cu ions from the scaffold, such MNs are effective in terms of promoting angiogenesis. With considerable biocompatibility and a minimally invasive approach, the degradable MN array composed of PEGDA/CMCS possessed superior capabilities to continuously and steadily release the loaded ingredients and avoid secondary damage to the wound. Benefiting from these features, the Cu@ZIF-8 encapsulated degradable MN array can dramatically accelerate epithelial regeneration and neovascularization. These results indicated that the combination of Cu@ZIF-8 and degradable MN arrays is valuable in promoting wound healing, which opened a new window for treatment of skin defection.

Animal tissue-derived biomaterials for promoting wound healing

The skin serves as the primary barrier between the human body and external environment, and is therefore susceptible to damage from various factors. In response to this challenge, animal tissue-derived biomaterials have emerged as promising candidates for wound healing due to their abundant sources, low side-effect profiles, exceptional bioactivity, biocompatibility, and unique extracellular matrix (ECM) mimicry. The evolution of modern engineering technology and therapies has allowed these animal tissue-derived biomaterials to be transformed into various forms and modified to possess the necessary properties for wound repair. This review provides an overview of the wound healing process and the factors that influence it. We then describe the extraction methods, important properties, and recent practical applications of various animal tissue-derived biomaterials. Our focus then shifts to the critical properties of these biomaterials in skin wound healing and their latest research developments. Finally, we critically examine the limitations and future prospects of biomaterials generated from animal tissues in this field.

Injectable, antibacterial, and oxygen-releasing chitosan-based hydrogel for multimodal healing of bacteria-infected wounds

Bacterial infection is one of the main challenges of wound healing. It imposes financial and healthcare costs. The emergence of antibiotic-resistant bacteria has increased concerns about this challenge, and made finding alternative solutions a crucial aim. We created a new, antibacterial, multifunctional hydrogel with synergistic chemodynamic and photothermal features for wound-healing applications. We fabricated a chitosan (CT)-based hydrogel containing tannic acid (TA), Fe, and MnO2 nanosheets (CT-TA-Fe-MnO2) via a simple method and characterized it. The antibacterial features (resulting from the production of reactive oxygen species within bacterial cells) and healing ability (via anti-inflammatory and hemostatic features) of the hydrogel were confirmed in vitro. In vivo results revealed the effectiveness of the CT-TA-Fe-MnO2 hydrogel in decreasing the hemostatic time, improving anti-inflammatory effects, and promoting wound healing during 14 days by enhancing the deposition and maturation of collagen fibers without affecting the vital organs. The fabricated CT-TA-Fe-MnO2 hydrogel could be a promising candidate with antibacterial and anti-inflammatory activities suitable for wound-healing applications.

Self-Assembled Chitosan/Dialdehyde Carboxymethyl Cellulose Hydrogels: Preparation and Application in the Removal of Complex Fungicide Formulations from Aqueous Media

Environmental contamination with pesticides occurs at a global scale as a result of prolonged usage and, therefore, their removal by low-cost and environmentally friendly systems is actively demanded. In this context, our study was directed to investigate the feasibility of using some self-assembled hydrogels, comprising chitosan (CS) and carboxymethylcellulose (CMC) or dialdehyde (DA)-CMC, for the removal of four complex fungicide formulations, namely Melody Compact (MC), Dithane (Dt), Curzate Manox (CM), and Cabrio®Top (CT). Porous CS/CMC and CS/DA-CMC hydrogels were prepared as discs by combining the semi-dissolution acidification sol-gel transition method with a freeze-drying approach. The obtained CS/CMC and CS/DA-CMC hydrogels were characterized by gel fraction yield, FTIR, SEM, swelling kinetics, and uniaxial compression tests. The batch-sorption studies indicated that the fungicides' removal efficiency (RE%) by the CS/CMC hydrogels was increased significantly with increasing sorbent doses reaching 94%, 93%, 66% and 48% for MC, Dt, CM and CT, respectively, at 0.2 g sorbent dose. The RE values were higher for the hydrogels prepared using DA-CMC than for those prepared using non-oxidized CMC when initial fungicide concentrations of 300 mg/L or 400 mg/L were used. Our results indicated that CS/DA-CMC hydrogels could be promising biosorbents for mitigating pesticide contamination of aqueous environments.

Prospects of Using Chitosan-Based Biopolymers in the Treatment of Peripheral Nerve Injuries

Peripheral nerve injuries are common neurological disorders, and the available treatment options, such as conservative management and surgical repair, often yield limited results. However, there is growing interest in the potential of using chitosan-based biopolymers as a novel therapeutic approach to treating these injuries. Chitosan-based biopolymers possess unique characteristics, including biocompatibility, biodegradability, and the ability to stimulate cell proliferation, making them highly suitable for repairing nerve defects and promoting nerve regeneration and functional recovery. Furthermore, these biopolymers can be utilized in drug delivery systems to control the release of therapeutic agents and facilitate the growth of nerve cells. This comprehensive review focuses on the latest advancements in utilizing chitosan-based biopolymers for peripheral nerve regeneration. By harnessing the potential of chitosan-based biopolymers, we can pave the way for innovative treatment strategies that significantly improve the outcomes of peripheral nerve injury repair, offering renewed hope and better prospects for patients in need.

Nanozyme-Integrated Thermoresponsive In Situ Forming Hydrogel Enhances Mesenchymal Stem Cell Viability and Paracrine Effect for Efficient Spinal Cord Repair

Mesenchymal stem cell (MSC)-based therapy has emerged as a promising strategy for the treatment of spinal cord injury (SCI). However, the hostile microenvironment of SCI, which can adversely affect the survival and paracrine effect of the implanted MSCs, severely limits the therapeutic efficacy of this approach. Here, we report on a ceria nanozyme-integrated thermoresponsive in situ forming hydrogel (CeNZ-gel) that can enable dual enhancement of MSC viability and paracrine effect, leading to highly efficient spinal cord repair. The sol-gel transition property of the CeNZ-gel at body temperature ensures uniform coverage of the hydrogel in injured spinal cord tissues. Our results demonstrate that the CeNZ-gel significantly increases the viability of transplanted MSCs in the microenvironment by attenuating oxidative stress and, more importantly, promotes the secretion of angiogenic factors from MSCs by inducing autophagy of MSCs. The synergy between the oxidative stress-relieving effect of CeNZs and the paracrine effect of MSCs accelerates angiogenesis, nerve repair, and motor function recovery after SCI, providing an efficient strategy for MSC-based SCI therapy.

Characteristics of Chitosan Films with the Bioactive Substances-Caffeine and Propolis

Chitosan is a natural and biodegradable polymer with promising potential for biomedical applications. This study concerns the production of chitosan-based materials for future use in the medical industry. Bioactive substances-caffeine and ethanolic propolis extract (EEP)-were incorporated into a chitosan matrix to increase the bioactivity of the obtained films and improve their mechanical properties. Acetic and citric acids were used as solvents in the production of the chitosan-based films. The obtained materials were characterized in terms of their antibacterial and antifungal activities, as well as their mechanical properties, including tensile strength and elongation at break. Moreover, the chemical structures and surface morphologies of the films were assessed. The results showed that the solution consisting of chitosan, citric acid, caffeine, and EEP exhibited an excellent antiradical effect. The activity of this solution (99.13%) was comparable to that of the standard antioxidant Trolox (92.82%). In addition, the film obtained from this solution showed good antibacterial activity, mainly against Escherichia coli and Enterococcus faecalis. The results also revealed that the films produced with citric acid exhibited higher activity levels against pathogenic bacteria than the films obtained with acetic acid. The antimicrobial effect of the chitosan-based films could be further enhanced by adding bioactive additives such as caffeine and propolis extract. The mechanical tests showed that the solvents and additives used affected the mechanical properties of the films obtained. The film produced from chitosan and acetic acid was characterized by the highest tensile strength value (46.95 MPa) while the chitosan-based film with citric acid showed the lowest value (2.28 MPa). The addition of caffeine and propolis to the film based on chitosan with acetic acid decreased its tensile strength while in the case of the chitosan-based film with citric acid, an increase in strength was observed. The obtained results suggested that chitosan films with natural bioactive substances can be a promising alternative to the traditional materials used in the medical industry, for example, as including biodegradable wound dressings or probiotic encapsulation materials.

Amikacin-Loaded Chitosan Hydrogel Film Cross-Linked with Folic Acid for Wound Healing Application

PURPOSE

Numerous carbohydrate polymers are frequently used in wound-dressing films because they are highly effective materials for promoting successful wound healing. In this study, we prepared amikacin (AM)-containing hydrogel films through the cross-linking of chitosan (CS) with folic acid along with methacrylic acid (MA), ammonium peroxodisulfate (APS), and methylenebisacrylamide (MBA). In the current studies, an effort has been made to look at the possibilities of these materials in developing new hydrogel film wound dressings meant for a slow release of the antibiotic AM and to enhance the potential for wound healing.

METHODS

Free-radical polymerization was used to generate the hydrogel film, and different concentrations of the CS polymer were used. Measurements were taken of the film thickness, weight fluctuation, folding resistance, moisture content, and moisture uptake. HPLC, FTIR, SEM, DSC, and AFM analyses were some of the different techniques used to confirm that the films were successfully developed.

RESULTS

The AM release profile demonstrated regulated release over a period of 24 h in simulated wound media at pH 5.5 and 7.4, with a low initial burst release. The antibacterial activity against gram-negative bacterial strains exhibited substantial effectiveness, with inhibitory zones measuring approximately 20.5 ± 0.1 mm. Additionally, in vitro cytocompatibility assessments demonstrated remarkable cell viability, surpassing 80%, specifically when evaluated against human skin fibroblast (HFF-1) cells.

CONCLUSIONS

The exciting findings of this study indicate the promising potential for further development and testing of these hydrogel films, offering effective and controlled antibiotic release to enhance the process of wound healing.

A dual physical crosslinking starch-based hydrogel exhibiting high strength, fatigue resistance, excellent biocompatibility, and biodegradability

Simultaneous realization of high strength, toughness, and fatigue resistance in natural starch-based hydrogel materials is challenging. A facile method of in situ self-assembly and a freeze-thaw cycle was proposed to construct double-network nanocomposite hydrogels of debranched corn starch/polyvinyl alcohol (Gels). Rheology, chemical structure, microstructure, and mechanical property of Gels were investigated. Notably, short linear starch chains were self-assembled into nanoparticles and subsequently into 3D microaggregates, which were tightly wrapped by starch and PVA network. Compared with corn starch single-network and starch/PVA double-network hydrogels, the Gels reached up to a higher compressive strength (ca. 1095.7 kPa), and then achieved to ∼20-30-fold improvement in compressive strength. Recovery efficiency exceeded 85% after 20 successive compression loading-unloading cycle tests. Furthermore, the Gels had good biocompatibility to L929 cells. Hence, the high-performance starch hydrogels are thought to serve as a biodegradable and biocompatible material to replace synthetic hydrogels, which can broaden their application fields.

Synthesis, Characterization, Properties, and Biomedical Application of Chitosan-Based Hydrogels

The prospective applications of chitosan-based hydrogels (CBHs), a category of biocompatible and biodegradable materials, in biomedical disciplines such as tissue engineering, wound healing, drug delivery, and biosensing have garnered great interest. The synthesis and characterization processes used to create CBHs play a significant role in determining their characteristics and effectiveness. The qualities of CBHs might be greatly influenced by tailoring the manufacturing method to get certain traits, including porosity, swelling, mechanical strength, and bioactivity. Additionally, characterization methods aid in gaining access to the microstructures and properties of CBHs. Herein, this review provides a comprehensive assessment of the state-of-the-art with a focus on the affiliation between particular properties and domains in biomedicine. Moreover, this review highlights the beneficial properties and wide application of stimuli-responsive CBHs. The main obstacles and prospects for the future of CBH development for biomedical applications are also covered in this review.