Chitin and chitosan on the nanoscale

Nanoscale cuttlebone-doped PVA/SA hydrogel with hemostatic and antibacterial properties

Effective wound management remains a major clinical challenge, especially in preventing infections and promoting rapid healing. However, traditional wound dressings often lack multifunctionality, limiting their ability to support hemostasis and antibacterial protection. To address this challenge, in this work, a novel wound dressing was developed utilizing nano-cuttlebone particles, which are rich in calcium carbonate and chitin, to enhance hemostatic and antimicrobial functionality. The dressing, composed of polyvinyl alcohol, sodium alginate, and nano-cuttlebone, addresses the need for advanced wound care solutions. The particle size distribution of the powder was evaluated using a laser particle size analyzer, and the particle size of the nano-cuttlebone was around 75 nm. The drug release experiment showed that the drug release of nano cuttlebone hydrogel was 1.4 times that of micro cuttlebone hydrogel in 48 h. The antibacterial activity of the nano-cuttlebone-doped dressing against S. aureus was 97.32 % and against E. coli was 99.99 %. The cell scratch test showed that the nano-cuttlebone hydrogel gradually migrated to the central area, and its migration rate was 61.43 % after 12 hours. The hydrogel also demonstrated excellent hemostatic ability in a mouse liver injury model and could rapidly stop bleeding within 1 min. In a full-thickness wound model, the nano-cuttlebone hydrogel enhanced collagen deposition and promoted faster wound closure. This study highlights the potential of marine biomaterials for developing multifunctional wound dressings to improve patient outcomes.

Structure and nanotoxicity of fungal chitin-glucan nanofibrils with gradient acid and alkaline treatments

Among nanoscale biopolymers, fungal chitin nanofibrils (ChNFs) stand out for their low carbon footprint and functional properties. However, the nanotoxicity properties of ChNFs have not been fully elucidated. To fill this knowledge gap, here we investigate the cytotoxicity and inflammatory effects of chemically modified ChNFs having gradient acid and alkaline treatments. ChNFs isolated from white mushroom exhibit a long fibrous morphology with diameters of 3-8 nm and lengths of 150-600 nm, and are composed of α-chitin in coexistence with amorphous covalently bounded β-glucans. Both alkaline (2 m NaOH) and acidic (2 m HCl) treatments impact the crystallinity, N-acetylation, zeta potential, and nitrogen content values to provide ranges of 23-to-51 %, 45-to-99 %, -5 to +26 mV, and 2.6-to-5.2 %, respectively. Nanotoxicity studies with colloidal dispersions demonstrate differences in the inflammatory response by cells after chemical post-treatments. The NaOH-treated ChNFs elicited a much lower inflammatory response, attenuating the release of nitrites and the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α). Alginate hydrogels with ChNFs were further fabricated and demonstrated potential to host cells in three-dimensional microenvironments, preserving a good metabolic activity, viability, and cell proliferation. These results may guide new applications of fungal nanochitin in pharmaceutical or tissue engineering.

Reactive bio-based flame retardant derived from chitosan, phytic acid, and epoxidized soybean oil for high-performance biodegradable foam

Due to the shortage of global petrochemical resources, preparing biodegradable polyurethane foam (PUF) with excellent strength and resistance against fire is an important way for sustainable development. A reactive all bio-based flame retardant CPE was prepared using chitosan (CS), phytic acid (PA), and epoxidized soybean oil (ESO) as raw materials. Meanwhile, the bio-based PUF matrix, named ERP, was prepared with ESO, ricinoleic acid (RA) and 4,4-diphenylmethane diisocyanate (PMDI). Thus, ERPC-EG foam with excellent performance was prepared by blending ERP, CPE flame retardant and expandable graphite (EG). The crosslinking of ESO with CS and PA effectively improved the hydrophobicity of CPE flame retardants. Furthermore, the LOI value of ERPC-EG foam is an exceptional 33.5 vol%. In addition, it attains V-0 classification in the UL-94 vertical combustion test, exhibiting excellent flame retardancy. Its peak heat release rate (pHRR) and total smoke release (TSP) during combustion are 99.42 kW/m2 and 0.91 m2, respectively, demonstrating effective smoke suppression capabilities. ERPC-EG foam exhibited a mass loss of 2.35 % following a 60-day burial in soil, indicating its biodegradable nature. This study presents a technique for creating biodegradable polyurethane foam with superior flame retardant properties.

Environmentally friendly pretreatment of chitin using relatively low concentration KOH/urea mixture for enhanced nanofiber preparation

Traditional methods to prepare chitin nanofibers require circular chemical treatment to further purify the chitin from the seller and the morphology of the prepared nanofibers is commonly rod-like one. This study introduces an approach utilizing low-temperature freeze pretreatment of chitin in a relatively low concentration KOH/urea mixture. The crystallinity of β-chitin reduced as the concentration of KOH increased in the pretreatment solvent. The concentration of urea had little effect on the crystallinity of chitin. The pretreated chitin was then oxidized in a 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)/NaBr/NaClO system to prepare nanofibers. The morphologies of the nanofibers can be regulated by oxidizing the chitin pretreated with different concentration of KOH. The nanofibers obtained by oxidizing chitin pretreated by 3 wt% KOH/ 1 wt% urea mixture showed rod-like morphologies with length about 150 nm. The carboxyl content of nanofibers prepared with KOH/urea mixture freeze treated chitin increased compared to that of nanofibers prepared with solely freeze treated chitin. In addition, the pretreatment solvent can be used to treat α-chitin and can be reused. The freeze KOH/urea mixture pretreatment methods can be extended to treat other biomasses for nanofiberization.

Nanochitin and Nanochitosan in Pharmaceutical Applications: Innovations, Applications, and Future Perspective

Nanochitin is a nanoscale form of chitin-a polysaccharide found in the exoskeletons of crustaceans, insects, and some fungal cell walls-that is newly garnering significant attention in the pharmaceutical space. Its good properties, such as biocompatibility, biodegradability, and an easily adjustable surface, render it attractive for various medical and pharmaceutical applications. Nanochitin, from drug delivery systems and wound-care formulations to vaccine adjuvants and antimicrobial strategies, has demonstrated its strong potential in meeting diverse therapeutic needs. This review covers the background of nanochitin, including methods for its extraction and refining and its principal physicochemical and biological properties. It further discusses various hydrolysis and enzymatic approaches for the structural and functional characterization of nanochitin and highlights some pharmaceutical applications where this biopolymer has been studied. The review also addresses toxicity issues, regulatory matters, and challenges in large-scale industrial production. Finally, it underscores novel avenues of investigation and future opportunities, emphasizing the urgent requirement for standardized production methods, rigorous safety assessment, and interdisciplinary partnerships to maximize nanochitin's potential in pharmaceutical research, demonstrating the importance of chitin in drug delivery.

Unveiling the multifunctionality of deep eutectic solvents: Their role as solvents, extracting, and curing agents in β-chitin nanowhisker/DGEBA epoxy composites-A comparative study with α-chitin

Chitin, a highly valuable mucopolysaccharide, has revolutionized the biomedical industry due to its exceptional properties and versatile applications. With a focus on green chemistry and sustainable development, this study extracted α-chitin from Metapenaeus monoceros and β-chitin from Uroteuthis duvaucelli using an eco-friendly Deep Eutectic Solvent (DES) system, consisting of choline chloride (hydrogen bond acceptor) and malonic acid (hydrogen bond donor). Chitin nanowhiskers (CNWs) were synthesized via DES and uniformly incorporated into DGEBA epoxy resin using a modified slurry compounding technique. The epoxy was cured with a novel salicylic acid-triethylenetetramine DES system, enhancing the sustainability of the process. This is the first study to compare α- and β-CNWs as sustainable reinforcements in epoxy resin composites. The results revealed that α-CNW composites exhibited remarkable mechanical properties, including 33 % higher tensile strength, 206 % improved impact strength, and 197 % greater fracture toughness compared to β-CNW composites. On the other hand, β-CNW composites demonstrated superior tensile modulus (25.98 %), dynamic mechanical performance, and thermal stability, attributed to β-chitin's high purity and ease of synthesis despite its lower crystallinity. This work underscores the transformative potential of DES in advancing green material design and highlights β-CNWs as promising candidates for high-performance, bio-based composite applications.

Nanofibrous Chitin Clusters Constructed via Controllable Crystalline Structure Transition for 3D Functional Materials

Intensively studied polymeric particle production technologies often rely on the combination of polymer self-assembly and particle processing techniques. Herein, an elegant crystallization transition-mediated strategy is proposed to confine molecular self-assembly within a limited range, avoiding the need for extra particle processing steps. This approach enables the production of the regenerated nanofibrous chitin clusters woven with the helical nanofibers. By dissolving the β-chitin in an aqueous NaOH solution and adjusting the degree of deacetylation (DD value) to 28.0-41.4%, the chitin chains self-assembly pathway is facilitated to undergo a crystalline transition from α-chitin to hydrated chitosan. This transition diminishes the chitin chains self-assembly tendency and confines the self-assembly to the submicro- and micrometer scales. The morphological parameters of these chitin clusters, including cluster size, nanofiber tentacle density, diameter, and helical pitch, can be tuned by adjusting the DD value. These nanofibrous chitin clusters are successfully employed as building blocks to create 3D structural materials for thermal insulation and functional food applications, demonstrating their potential in constructing advanced materials. It is anticipated that the crystalline structure transition-mediated concept can be applied to other polymeric particle fabrication, opening up a new avenue for designing advanced particles for various applications.

Chiral nematic cellulose nanocrystal films: Sucrose modulation for structural color and dynamic behavior

This study explores the effect of sucrose addition on the properties of chiral nematic cellulose nanocrystal (CNC) films for potential food industry applications, including biodegradable packaging and food coloring. The addition of sucrose altered the films' structural color, shifting from blue in pure CNC films to aqua blue, green, yellow-green, and red with increasing sucrose concentrations (up to 21 %). Surface analysis revealed a reduction in contact angle from 96° to 48° due to sucrose's hydrophilic nature and smoother film surfaces. XRD results indicated a decrease in crystallinity from 84.5 % to 15.6 %, linked to the disruption of CNC alignment by sucrose. Mechanical testing showed reduced tensile strength (138 MPa to 35 MPa) and Young's modulus (1.634 GPa to 70 MPa) with higher sucrose content. Notably, over the storage time, films with 21 % sucrose exhibited dynamic structural coloration caused by localized sucrose recrystallization, leading to pitch shifts and color transitions. These findings demonstrate the tunable optical and mechanical properties of CNC-sucrose films, positioning them as promising materials for sustainable food packaging and responsive coatings.

Nanochitin: Green nanomaterial for sustainable applications in agriculture and environmental remediation

The need for a green and sustainable nanomaterial sourced from biomass in the form of nanochitin has raised interest in paving the way towards incorporating biological resources for the production of functional materials. Nanochitin as nanofibers and nanocrystals/whiskers have attractive features like their ability to self-assemble into multidimensional biomaterials while retaining their intrinsic characteristics. Herein, the review discusses chitin's molecular association and hierarchical assemblies and gives an overview of the extraction methods adopted to produce nanochitin. Recent progress in the development of advanced functional nanochitin-based materials/composites and their current application in agriculture and environmental remediation are reviewed to gain a better understanding of their applicability for forthcoming research and improvement. Furthermore, the environmental impact assessment of chitin has been discussed, followed by the techno-economic analysis, thus providing scope for improvement in manufacturing and perspectives on the potential of nanochitin in the context of sustainable material and their role in circular bioeconomy.

3D nanofiber sponge based on natural insect quaternized chitosan/pullulan/citric acid for accelerating wound healing

Extensive traumatic injuries and difficult-to-heal wounds, induced by many circumstances, impose a significant social and economic burden on an annual basis. Thus, innovative wound dressings that encourage wound healing are greatly needed. In this work, we prepared a novel insect chitosan (MCS) using waste pupal shells from housefly (Musca domestica L.) culture. After conducting comparative investigations with commercially available chitosan, it was shown that MCS exhibited comparable qualities and may be used as a substitute source of commercial chitosan. A quaternized chitosan/pullulan/citric acid three-dimensional nanofiber sponge (3D-NS) of natural origin was prepared by electrostatic spinning and gas foaming techniques after MCS was quaternized. In vitro, tests showed that the 3D-NS had a higher liquid absorption capacity than the two-dimensional nanofibrous membrane (2D-NM). Additionally, the 3D-NS showed improved hemostatic, pro-cell proliferation, antibacterial, and anti-inflammatory qualities. In vitro, tests demonstrated that 3D-NS could inhibit the release of inflammatory factors, promote angiogenesis, accelerate collagen deposition, and promote wound contraction. These effects considerably facilitated the healing process of wounds in rats with full-thickness skin damage. In conclusion, the great bioactivity and physicochemical properties of 3D-NS render it an optimal candidate for developing novel wound dressings.

Synthetic chitin oligosaccharide nanocrystals and their higher-order assemblies

Self-assembly is a powerful strategy for creating complex architectures and elucidating the aggregation behaviors of biopolymers. Herein, we investigate the hierarchical assembly of chitin using a bottom-up approach based on synthetic oligosaccharides. We discovered that chitin oligosaccharides self-assemble into platelets, which then form higher-order structures. Subtle changes in experimental conditions drastically altered the self-assembly results, generating a wide array of higher-order architectures. Through systematic investigations employing transmission electron microscopy (TEM), photoinduced force microscopy (PiFM), and atomic force microscopy (AFM), we uncovered the role of water in shaping the different morphologies. This finding gave us the tools to promote the formation of chiral, uniform chitin oligosaccharide bundles. Our work not only sheds light on the fundamental aspects of chitin organization, but also suggests strategies for designing carbohydrate-based materials with tunable structures and properties.

Fungal Chitin Nanofibrils Improve Mechanical Performance and UV-Light Resistance in Carboxymethylcellulose and Polyvinylpyrrolidone Films

Materials from renewable carbon feedstock can limit our dependence on fossil carbon and facilitate the transition from linear carbon-intensive economies to sustainable, circular economies. Chitin nanofibrils (ChNFs) isolated from white mushrooms offer remarkable environmental benefits over conventional crustacean-derived nanochitin. Herein, ChNFs are utilized to reinforce polymers of natural and fossil origin, carboxymethyl cellulose (CMC) and polyvinylpyrrolidone (PVP), respectively. Incorporation of 5 wt % ChNFs increases the Young's modulus from 1217 ± 11 to 1509 ± 22 MPa for PVP and from 1979 ± 48 to 2216 ± 102 MPa for CMC. ChNFs increase surface hydrophobicity and retard the scission of the C-H bond as a result of UV-light irradiation in both polymers under investigation. The yellowing from chain scission is reduced, while long-lasting retention of ductility is ensured. Given these results, we propose the utilization of ChNFs in sustainable polymeric materials from renewable carbon with competitive performance against fossil-based benchmark plastics.

Emerging Nanochitosan for Sustainable Agriculture

Chemical-intensive agriculture challenges environmental sustainability and biodiversity and must be changed. Minimizing the use of agrochemicals based on renewable resources can reduce or eliminate ecosystems and biodiversity threats. Nanochitosan as a sustainable alternative offers promising solutions for sustainable agricultural practices that work at multiple spatial and temporal scales throughout the plant growth cycle. This review focuses on the potential of nanochitosan in sustainable agricultural production and provides insights into the mechanisms of action and application options of nanochitosan throughout the plant growth cycle. We emphasize the role of nanochitosan in increasing crop yields, mitigating plant diseases, and reducing agrochemical accumulation. The paper discusses the sources of nanochitosan and its plant growth promotion, antimicrobial properties, and delivery capacity. Furthermore, we outline the challenges and prospects of research trends of nanochitosan in sustainable agricultural production practices and highlight the potential of nanochitosan as a sustainable alternative to traditional agrochemicals.

Recent advancements and perspectives on processable natural biopolymers: Cellulose, chitosan, eggshell membrane, and silk fibroin

With the rapid development of the global economy and the continuous consumption of fossil resources, sustainable and biodegradable natural biomass has garnered extensive attention as a promising substitute for synthetic polymers. Due to their hierarchical and nanoscale structures, natural biopolymers exhibit remarkable mechanical properties, along with excellent innate biocompatibility and biodegradability, demonstrating significant potential in various application scenarios. Among these biopolymers, proteins and polysaccharides are the most commonly studied due to their low cost, abundance, and ease of use. However, the direct processing/conversion of proteins and polysaccharides into their final products has been a long-standing challenge due to their natural morphology and compositions. In this review, we emphasize the importance of processing natural biopolymers into high-value-added products through sustainable and cost-effective methods. We begin with the extraction of four types of natural biopolymers: cellulose, chitosan, eggshell membrane, and silk fibroin. The processing and post-functionalization strategies for these natural biopolymers are then highlighted. Alongside their unique structures, the versatile potential applications of these processable natural biopolymers in biomedical engineering, biosensors, environmental engineering, and energy applications are illustrated. Finally, we provide a summary and future outlook on processable natural biopolymers, underscoring the significance of converting natural biopolymers into valuable biomaterial platforms.

Biowaste-Derived Triboelectric Nanogenerators for Emerging Bioelectronics

Triboelectric nanogenerators (TENGs) combine contact electrification and electrostatic induction effects to convert waste mechanical energy into electrical energy. As conventional devices contribute to electronic waste, TENGs based on ecofriendly and biocompatible materials have been developed for various energy applications. Owing to the abundance, accessibility, low cost, and biodegradability of biowaste (BW), recycling these materials has gained considerable attention as a green approach for fabricating TENGs. This review provides a detailed overview of BW materials, processing techniques for BW-based TENGs (BW-TENGs), and potential applications of BW-TENGs in emerging bioelectronics. In particular, recent progress in material design, fabrication methods, and biomechanical and environmental energy-harvesting performance is discussed. This review is aimed at promoting the continued development of BW-TENGs and their adoption for sustainable energy-harvesting applications in the field of bioelectronics.

Recent Advances in the Preparation, Antibacterial Mechanisms, and Applications of Chitosan

Chitosan, a cationic polysaccharide derived from the deacetylation of chitin, is widely distributed in nature. Its antibacterial activity, biocompatibility, biodegradability, and non-toxicity have given it extensive uses in medicine, food, and cosmetics. However, the significant impact of variations in the physicochemical properties of chitosan extracted from different sources on its application efficacy, as well as the considerable differences in its antimicrobial mechanisms under varying conditions, limit the full realization of its biological functions. Therefore, this paper provides a comprehensive review of the structural characteristics of chitosan, its preparation methods from different sources, its antimicrobial mechanisms, and the factors influencing its antimicrobial efficacy. Furthermore, we highlight the latest applications of chitosan and its derivatives across various fields. We found that the use of microbial extraction shows promise as a new method for producing high-quality chitosan. By analyzing the different physicochemical properties of chitosan from various sources and the application of chitosan-based materials (such as nanoparticles, films, sponges, and hydrogels) prepared using different methods in biomedicine, food, agriculture, and cosmetics, we expect these findings to provide theoretical support for the broader utilization of chitosan.

Recent advances in chitosan-based smart hydrogel for drug delivery systems

Achieving sustainable and controllable drug delivery is a highly effective disease treatment approach. Chitosan hydrogels, with their unique three-dimensional (3D) porous structures, offer tunable capacity, controllable degradation, various stimuli sensitivities, and the ability to encapsulate therapeutic agents. These characteristics provide chitosan hydrogels with inherent advantages as vehicles for drug delivery systems. In recent years, there has been a notable shift toward embracing the "back-to-nature" ethos, with biomass materials emerging as promising candidates for constructing chitosan hydrogels used in controlled drug release applications. This trend is sustained by their biodegradability, biocompatibility, and non-toxic properties, emphasizing their unique benefits and innovative features. These hydrogels exhibit sensitivity to various factors such as temperature, pH, ion concentration, light, magnetic fields, redox, ultrasound, and multi-responsiveness, offering opportunities for finely tuned drug release mechanisms. This review comprehensively outlines fabrication methods, properties, and biocompatibility of chitosan hydrogel, as well as modification strategies and stimuli-responsive mechanisms. Furthermore, their potential applications in subcutaneous (wound dressing), parental (transdermal drug delivery), oral (gastrointestinal tract), and facial (ophthalmic and brain) drug delivery are briefly discussed. The challenges in clinical application and the future outlook of chitosan-based smart hydrogel are also highlighted.

Chitin Nanocomposites for Fused Filament Fabrication: Flexible Materials with Enhanced Interlayer Adhesion

In this work, we present a series of nanocomposites for Fused filament fabrication (FFF) based on polycaprolactone (PCL) and chitin nanocrystals (ChNCs). The ChNCs were synthesized by acid hydrolysis using HCl or lactic acid (LA). The approach using LA, an organic acid, makes the ChNCs synthesis more sustainable and modifies their surface with lactate groups, increasing their compatibility with the PCL matrix. The ChNCs characterization by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy revealed that both ChNCs presented similar morphologies and crystallinity, while differential scanning calorimetry and thermogravimetric analysis proved that they can bear temperatures up to 210 °C without degrading, which allows their processing in the manufacturing of PCL composites by twin-screw extrusion. Therefore, PCL composites in the form of filaments containing 0.5-1.0 wt % ChNCs were produced and used as feedstock in FFF, and standard tensile and flexural specimens were printed at different temperatures, up to 170 °C, to assess the influence of the ChNCs in the mechanical properties of the material. The tensile testing results showed that the presence of ChNCs enhances the strength and ductility of the PCL matrix, increasing the elongation at break around 20-50%. Moreover, the vertically printed flexural specimens showed a very different bending behavior, such that the pure PCL specimens presented a brittle fracture at 7% strain, while the ChNCs composites were able to bend over themselves. Hence, this work proves that the presence of ChNCs aims to improve the interlayer adhesion of the objects manufactured by FFF due to their good adhesive properties, which is currently a concern for the scientific community and the industrial sector.

Valorization of Seafood Waste for Food Packaging Development

Packaging plays a crucial role in protecting food by providing excellent mechanical properties as well as effectively blocking water vapor, oxygen, oil, and other contaminants. The low degradation of widely used petroleum-based plastics leads to environmental pollution and poses health risks. This has drawn interest in renewable biopolymers as sustainable alternatives. The seafood industry generates significant waste that is rich in bioactive substances like chitin, chitosan, gelatins, and alginate, which can replace synthetic polymers in food packaging. Although biopolymers offer biodegradability, biocompatibility, and non-toxicity, their films often lack mechanical and barrier properties compared with synthetic polymer films. This comprehensive review discusses the chemical structure, characteristics, and extraction methods of biopolymers derived from seafood waste and their usage in the packaging area as reinforcement or base materials to guide researchers toward successful plastics replacement and commercialization. Our review highlights recent advancements in improving the thermal durability, mechanical strength, and barrier properties of seafood waste-derived packaging, explores the mechanisms behind these improvements, and briefly mentions the antimicrobial activities and mechanisms gained from these biopolymers. In addition, the remaining challenges and future directions for using seafood waste-derived biopolymers for packaging are discussed. This review aims to guide ongoing efforts to develop seafood waste-derived biopolymer films that can ultimately replace traditional plastic packaging.

Next-generation all-organic composites: A sustainable successor to organic-inorganic hybrid materials

This Review presents an overview of all-organic nanocomposites, a sustainable alternative to organic-inorganic hybrids. All-organic nanocomposites contain nanocellulose, nanochitin, and aramid nanofibers as highly rigid reinforcing fillers. They offer superior mechanical properties and lightweight characteristics suitable for diverse applications. The Review discusses various methods for preparing the organic nanofillers, including top-down and bottom-up approaches. It highlights in situ polymerization as the preferred method for incorporating these nanomaterials into polymer matrices to achieve homogeneous filler dispersion, a crucial factor for realizing desired performance. Furthermore, the Review explores several applications of all-organic nanocomposites in diverse fields including food packaging, performance-advantaged plastics, and electronic materials. Future research directions-developing sustainable production methods, expanding biomedical applications, and enhancing resistance against heat, chemicals, and radiation of all-organic nanocomposites to permit their use in extreme environments-are explored. This Review offers insights into the potential of all-organic nanocomposites to drive sustainable growth while meeting the demand for high-performance materials across various industries.

Recent advances in nanomaterial-stabilized pickering foam: Mechanism, classification, properties, and applications

Pickering foam is a type of foam stabilized by solid particles known as Pickering stabilizers. These solid stabilizers adsorb at the liquid-gas interface, providing superior stability to the foam. Because of its high stability, controllability, versatility, and minimal environmental impact, nanomaterial-stabilized Pickering foam has opened up new possibilities and development prospects for foam applications. This review provides an overview of the current state of development of Pickering foam stabilized by a wide range of nanomaterials, including cellulose nanomaterials, chitin nanomaterials, silica nanoparticles, protein nanoparticles, clay mineral, carbon nanotubes, calcium carbonate nanoparticles, MXene, and graphene oxide nanosheets. Particularly, the preparation and surface modification methods of various nanoparticles, the fundamental properties of nanomaterial-stabilized Pickering foam, and the synergistic effects between nanoparticles and surfactants, functional polymers, and other additives are systematically introduced. In addition, the latest progress in the application of nanomaterial-stabilized Pickering foam in the oil industry, food industry, porous functional material, and foam flotation field is highlighted. Finally, the future prospects of nanomaterial-stabilized Pickering foam in different fields, along with directions for further research and development directions, are outlined.

Multiscale Anion-Hybrid in Atomic Ni Sites for High-Rate Water Electrolysis: Insights into the Charge Accumulation Mechanism

Single-atom catalysts, characterized by transition metal-(N/O)4 units on nanocarbon (M-(N/O)4-C), have emerged as efficient performers in water electrolysis. However, there are few guiding principles for accurately controlling the ligand fields of single atoms to further stimulate the catalyst activities. Herein, using the Ni-(N/O)4-C unit as a model, we develop a further modification of the P anion on the outer shells to modulate the morphology of the ligand. The catalyst thus prepared possesses high activity and excellent long-term durability, surpassing commercial Pt/C, RuO2, and currently reported single-atom catalysts. Notably, mechanistic studies demonstrated that the pseudocapacitive feature of multiscale anion-hybrid nanocarbon is considerable at accumulating enough positive charge [Q], contributing to the high oxygen evolution reaction (OER) order (β) through the rate formula. DFT calculations also indicate that the catalytic activity is decided by the suitable barrier energy of the intermediates due to charge accumulation. This work reveals the activity origin of single atoms on multihybrid nanocarbon, providing a clear experiential formula for designing the electronic configuration of single-atom catalysts to boost electrocatalytic performance.

Microflow sensing and control using an in-channel birefringent biomembrane

This study describes the function, optimization, and demonstration of a new class of passive, low-cost microfluidic flow meters based on birefringent chitosan biomembranes analyzed by polarized microscopy. We subjected the membrane to dynamic flow conditions while monitoring the real-time response of its optical properties. We obtained figures of merit, including the linear response operating range (0 to 65 μL min-1), minimum response time (250 ms), sensitivity (2.03% × 10-3 μL-1 min), and minimum sensor longevity (1 week). In addition, possible sources of interference were identified. Finally, we demonstrate the membrane as a low-cost flow rate measurement device for the close loop control of a commercial pressure-driven pump. Preliminary experiments using a basic PID controller with the membrane-based flow rate measurement device showed that stable control could be achieved and the system could reach steady-state behavior in less than 15 seconds. Analysis of fundamental limits to sensor response time indicate the potential for faster steady-state behaviour.

Advances in Stimuli-Responsive Chitosan Hydrogels for Drug Delivery Systems

Sustainable and controllable drug transport is one of the most efficient ways of disease treatment. Due to high biocompatibility, good biodegradability, and low costs, chitosan and its derivatives are widely used in biomedical fields. Specifically, chitosan hydrogel enables drugs to pass through biological barriers because of their abundant amino and hydroxyl groups that can interact with human tissues. Moreover, the multi-responsive nature (pH, temperature, ions strength, and magnetic field, etc.) of chitosan hydrogels makes precise drug release a possibility. Here, the synthesis methods, modification strategies, stimuli-responsive mechanisms of chitosan-based hydrogels, and their recent progress in drug delivery are summarized. Chitosan hydrogels that carry and release drugs through subcutaneous (dealing with wound dressing), oral (dealing with gastrointestinal tract), and facial (dealing with ophthalmic, ear, and brain) are reviewed. Finally, challenges toward clinic application and the future prospects of stimuli-responsive chitosan-based hydrogels are indicated.

Preparation of nanochitin using deep eutectic solvents

Chitin is an abundant and renewable non-wood biopolymer. Nanochitin is formed by the assembly of chitin molecules, which has the advantages of large tensile strength, high specific surface area, and biodegradability, so it has been widely used. However, the traditional methods of preparing nanochitin have many drawbacks. As the new generation of green solvents, deep eutectic solvents (DESs) have been successfully applied in the fields of chitin dissolution, extraction, and nanochitin preparation. In this review, the relevant knowledge of chitin, nanochitin, and DESs was first introduced. Then, the application status of DESs in the fields of chitin was summarized, with a focus on the preparation of nanochitin using DESs. In conclusion, this review provided a comprehensive analysis of the published literature and proposed insights and development trends in the field of preparation of nanochitin using DESs, aiming to provide guidance and assistance for future researchers.

Nanochitosan from crustacean and mollusk byproduct: Extraction, characterization, and applications in the food industry

Crustaceans and mollusks are widely consumed around the world due to their delicacy and nutritious value. During the processing, only 30-40 % of these shellfish are considered edible, while 70-60 % of portions are thrown away as waste or byproduct. These byproducts harbor valuable constituents, notably chitin. This chitin can be extracted from shellfish byproducts through chemical, microbial, enzymatic, and green technologies. However, chitin is insoluble in water and most of the organic solvents, hampering its wide application. Hence, chitin is de-acetylated into chitosan, which possesses various functional applications. Recently, nanotechnology has proven to improve the surface area and numerous functional properties of metals and molecules. Further, the nanotechnology principle can be extended to nanochitosan formation. Therefore, this review article centers on crustaceans and mollusks byproduct utilization for chitosan, its nano-formation, and their food industry applications. The extensive discussion has been focused on nanochitosan formation, characterization, and active site modification. Lastly, nanochitosan applications in various food industries, including biodegradable food packaging, fat replacer, bioactive compound carrier, and antimicrobial agent have been reported.

Nanochitin for sustainable and advanced manufacturing

Presently, the rapid depletion of resources and drastic climate change highlight the importance of sustainable development. In this case, nanochitin derived from chitin, the second most abundant renewable polymer in the world, possesses numerous advantages, including toughness, easy processability and biodegradability. Furthermore, it exhibits better dispersibility in various solvents and higher reactivity than chitin owing to its increased surface area to volume ratio. Additionally, it is the only natural polysaccharide that contains nitrogen. Therefore, it is valuable to further develop this innovative technology. This review summarizes the recent developments in nanochitin and specifically identifies sustainable strategies for its preparation. Additionally, the different biomass sources that can be exploited for the extraction of nanochitin are highlighted. More importantly, the life cycle assessment of nanochitin preparation is discussed, followed by its applications in advanced manufacturing and perspectives on the valorization of chitin waste.

Preparation, characterization, and adsorption kinetics of graphene oxide/chitosan/carboxymethyl cellulose composites for the removal of environmentally relevant toxic metals

This study attempted to develop a low-cost and eco-friendly bio-based composite adsorbent that is highly efficient in capturing potential toxic metals. The bio-composite adsorbent was prepared using graphene oxide (GO), carboxymethyl cellulose (CMC) and chitosan (CS); and characterized using FTIR, SEM-EDX and WAXD techniques. Metal-ion concentration in an aqueous solution was measured by ICP-OES. This article reveals that the adsorption of heavy metal ions varied according to the adsorbent quantity, initial metal concentration, pH, and interaction time. The metal ions' adsorption capacity (mg/g) was observed to increase when the interaction time and metal concentration increased. Conversely, metal ions adsorption was decreased with an increase in adsorbent dosages. The effect of pH on metal ions' adsorption was ion-specific. The substantial adsorption by GO/CMC/CS composite for Co2+, CrO42-, Mn2+ and Cd2+, had the respective values of 43.55, 77.70, 57.78, and 91.38 mg/g under acidic conditions. The metal ions experimental data were best fitted with pseudo-second-order (PSO) kinetics, and Freundlich isotherm model (except Co2+). The separation factors (RL) value in the present investigation were found between 0 and 1, meaning that the metal ions adsorption onto GO/CS/CMC composite is favorable. The RL and sorption intensity (1/n) values fitted well to the adsorption isotherm.

Chitin-based pulps: Structure-property relationships and environmental sustainability

The deconstruction and valorization of chitinous biomass from crustaceans is a promising route for sustainable bioproduct development alternative to petroleum-based materials. However, chitin nanocrystal and chitin nanofibril isolation from crustacean shells is often subjected to extensive processing, compromising their environmental and cost sustainability. To address the sustainability challenge that chitin valorization presents, herein we introduce a mild fibrillation route to generate "chitin pulp"; where a careful control of the macro- and micro-fibrillated chitin with protein and mineral components yields tailored properties. Films produced from protein-rich chitin pulp showed ultimate strength of up to 93 ± 7 MPa. The surface energy and wetting behavior, going from hydrophilic to nearly-hydrophobic, could be tailored as a function of pulp composition. Life cycle assessment of the protein-rich chitin pulps demonstrated that the global warming potential of chitin pulp is reduced by 2 to 3 times when compared to chitin nanocrystals. Overall, this work presents a new and potentially scalable route for the generation of chitin-based materials having a reduced environmental footprint compared to nanochitins and chitosan, thus opening a new route for the valorization of chitin beyond nanochitin for the development of environmentally and economically sustainable materials.

All-in-one porous membrane enables full protection in guided bone regeneration

The sophisticated hierarchical structure that precisely combines contradictory mechanical and biological characteristics is ideal for biomaterials, but it is challenging to achieve. Herein, we engineer a spatiotemporally hierarchical guided bone regeneration (GBR) membrane by rational bilayer integration of densely porous N-halamine functionalized bacterial cellulose nanonetwork facing the gingiva and loosely porous chitosan-hydroxyapatite composite micronetwork facing the alveolar bone. Our GBR membrane asymmetrically combine stiffness and flexibility, ingrowth barrier and ingrowth guiding, as well as anti-bacteria and cell-activation. The dense layer has a mechanically matched space maintenance capacity toward gingiva, continuously blocks fibroblasts, and prevents bacterial invasion with multiple mechanisms including release-killing, contact-killing, anti-adhesion, and nanopore-blocking; the loose layer is ultra-soft to conformally cover bone surfaces and defect cavity edges, enables ingrowth of osteogenesis-associated cells, and creates a favorable osteogenic microenvironment. As a result, our all-in-one porous membrane possesses full protective abilities in GBR.

Antibacterial and hemostatic chitin sponge directly constructed from Pleurotus Eryngii via top-down approach

Chitin, the second most abundant polysaccharide on earth, possesses unique characteristics, including biosafety, biodegradability, and procoagulant activity, making it an attractive material for hemostasis. However, the conventional bottom-up construction of chitin-based materials is intricate and time-consuming. In this study, we have developed a top-down strategy to prepare a 3D porous chitin-based hemostatic sponge with exceptional hemostatic properties and antibacterial activity, directly from the spongy Pleurotus eryngii. The top-down method involves deproteinization, in situ quaternization, and tannin acid crosslinking. The obtained sponge has an interconnected microporous structure with high porosity (89.7 ± 3.2 %), endowing it with high water absorption (2047 ± 105 %) and rapid water-triggered shape-memory behavior (< 2 s). The sponge exhibits superior blood coagulant activity and outperforms standard medical gauze, gelatin sponge, and chitosan sponge in both topical artery and non-compressive liver puncture wound. In addition, the sponge exhibited significant antibacterial activity against both gram-positive Staphylococcus aureus and gram-negative Escherichia coli. In summary, this study provides a straightforward and practical approach for constructing an antibacterial and hemostatic chitin sponge that could be a valuable option for treating bleeding wounds.

Chitosan nanoparticles and based composites as a biocompatible vehicle for drug delivery: A review

The shellfish processing industry is one of the largest growing industries across the globe with a market size of around USD 62B. However, it also leads to a significant environmental issue as it produces >80,000 tons of waste shells globally. Unfortunately, the slow degradation of this waste causes it to accumulate over time, posing a serious threat to the marine environment. The key solution to this problem is to recycle this sea waste into a valuable product like chitin which is further used to produce chitosan. Chitosan is a natural biopolymeric substance obtained via N-deacetylation of the chitin. The chitosan-based nanoparticles are further useful for the fabrication of biopolymeric nanocomposites which are used in various biomedical applications specifically in drug delivery. Here, we review the recent advancements in the development of chitosan-based nanocomposites as a biocompatible carrier for drug delivery, specifically focusing on gene delivery, wound healing, microbial treatment, and anticancer drug delivery. By providing a valuable and up-to-date resource, this review illuminates the current state of research concerning chitosan's pivotal role in the biomedical domain as an efficacious drug delivery agent.

Structural Color from Cellulose Nanocrystals or Chitin Nanocrystals: Self-Assembly, Optics, and Applications

Widespread concerns over the impact of human activity on the environment have resulted in a desire to replace artificial functional materials with naturally derived alternatives. As such, polysaccharides are drawing increasing attention due to offering a renewable, biodegradable, and biocompatible feedstock for functional nanomaterials. In particular, nanocrystals of cellulose and chitin have emerged as versatile and sustainable building blocks for diverse applications, ranging from mechanical reinforcement to structural coloration. Much of this interest arises from the tendency of these colloidally stable nanoparticles to self-organize in water into a lyotropic cholesteric liquid crystal, which can be readily manipulated in terms of its periodicity, structure, and geometry. Importantly, this helicoidal ordering can be retained into the solid-state, offering an accessible route to complex nanostructured films, coatings, and particles. In this review, the process of forming iridescent, structurally colored films from suspensions of cellulose nanocrystals (CNCs) is summarized and the mechanisms underlying the chemical and physical phenomena at each stage in the process explored. Analogy is then drawn with chitin nanocrystals (ChNCs), allowing for key differences to be critically assessed and strategies toward structural coloration to be presented. Importantly, the progress toward translating this technology from academia to industry is summarized, with unresolved scientific and technical questions put forward as challenges to the community.

Biomass-based single- and double-network hydrogels derived from cellulose microfiber and chitosan for potential application as plant growing substrate

A series of hydrogels were synthesized from renewable and low-cost micro-sized cellulose fiber. The single-network hydrogel was composed of cellulose fiber and a small amount of another polysaccharide, chitosan, which 'glued' individual cellulose fiber pieces together through Schiff-base bonding. The double-network hydrogel was constructed by adding a secondary network, the covalently crosslinked polyacrylamide, into the single-network hydrogel, which was synthesized by conducting Schiff-base reaction and free radical polymerization at the same time in a facile one-pot process. In both single- and double-network hydrogels, cellulose fiber constituted the dominant component. Both types of hydrogels exhibited good swelling properties. The double-network hydrogel showed much improved stability against soaking in water and higher salt tolerance. Germination experiment with choy sum seeds sowed on hydrogel surface showed that the seeds were able to germinate and further develop roots, shoots, and true leaves, demonstrating the potential of the biomass-derived hydrogels for soilless plant growing applications.

Progress in construction and release of natural polysaccharide-platinum nanomedicines: A review

Natural polysaccharides are natural biomaterials that have become candidate materials for nano-drug delivery systems due to their excellent biodegradability and biocompatibility. Platinum (Pt) drugs have been widely used in the clinical therapy for various solid tumors. However, their extensive systemic toxicity and the drug resistance acquired by cancer cells limit the applications of platinum drugs. Modern nanobiotechnology provides the possibility for targeted delivery of platinum drugs to the tumor site, thereby minimizing toxicity and optimizing the efficacies of the drugs. In recent years, numerous natural polysaccharide-platinum nanomedicine delivery carriers have been developed, such as nanomicelles, nanospheres, nanogels, etc. Herein, we provide an overview on the construction and drug release of natural polysaccharide-Pt nanomedicines in recent years. Current challenges and future prospectives in this field are also put forward. In general, combining with irradiation and tumor microenvironment provides a significant research direction for the construction of natural polysaccharide-platinum nanomedicines and the release of responsive drugs in the future.

Effect of Surface Functionality on the Rheological and Self-Assembly Properties of Chitin and Chitosan Nanocrystals and Use in Biopolymer Films

Chitin nanocrystals (ChNCs) are unique to all other bio-derived nanomaterials in one aspect: the inherent presence of a nitrogen moiety. By tuning the chemical functionality of this nanomaterial, and thus its charge and hydrogen bonding capacity, one can heavily impact its macroscopic properties such as its rheological and self-assembly characteristics. In this study, two types of ChNCs are made using acid hydrolysis (AH-ChNCs) and oxidative (OX-ChNCs) pathways, unto which deacetylation using a solvent-free procedure is utilized to create chitosan nanocrystals (ChsNCs) of varying degree of deacetylation (DDA). These nanocrystals were then studied for their rheological behavior and liquid crystalline ordering. It was found that with both deacetylation and carboxylation of ChNCs, viscosity continually increased with increasing concentrations from 2 to 8 wt %, contrary to AH-ChNC dispersions in the same range. Interestingly, increasing the amine content of ChNCs was not proportional to the storage modulus, where a peak saturation of amines provided the most stiffness. Conversely, while the introduction of carboxylation increased the elastic modulus of OX-ChNCs by an order of magnitude from that of AH-ChNCs, it was decreased by increasing DDA. Deacetylation and carboxylation both inhibited the formation of a chiral nematic phase. Finally, these series of nanocrystals were incorporated into biodegradable pectin-alginate films as a physical reinforcement, which showed increased tensile strength and Young's modulus values for the films incorporated with ChsNCs. Overall, this study is the first to investigate how surface functionalization of chitin-derived nanocrystals can affect their rheological and liquid crystalline properties and how it augments pectin/alginate films as a physical reinforcement nanofiller.

Supramolecular Cu(ii) nanoparticles supported on a functionalized chitosan containing urea and thiourea bridges as a recoverable nanocatalyst for efficient synthesis of 1H-tetrazoles

A cost-effective and convenient method for supporting of Cu(ii) nanoparticles on a modified chitosan backbone containing urea and thiourea bridges using thiosemicarbazide (TS), pyromellitic dianhydride (PMDA) and toluene-2,4-diisocyanate (TDI) linkers was designed. The prepared supramolecular (CS-TDI-PMDA-TS-Cu(ii)) nanocomposite was characterized by using Fourier-transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), thermogravimetry/differential thermogravimetry analysis (TGA/DTA), energy-dispersive X-ray spectroscopy (EDS), EDS elemental mapping and X-ray diffraction (XRD). The obtained supramolecular CS-TDI-PMDA-TS-Cu(ii) nanomaterial was demonstrated to act as a multifunctional nanocatalyst for promoting of multicomponent cascade Knoevenagel condensation/click 1,3-dipolar azide-nitrile cycloaddition reactions very efficiently between aromatic aldehydes, sodium azide and malononitrile under solvent-free conditions and affording the corresponding (E)-2-(1H-tetrazole-5-yl)-3-arylacrylenenitrile derivatives. Low catalyst loading, working under solvent-free conditions and short reaction time as well as easy preparation and recycling, and reuse of the catalyst for five consecutive cycles without considerable decrease in its catalytic efficiency make it a suitable candidate for the catalytic reactions promoted by Cu species.

Multifunctional fully biobased aerogels for water remediation: Applications for dye and heavy metal adsorption and oil/water separation

Water ecosystem contamination from industrial pollutants is an emerging threat to both humans and native species, making it a point of global concern. In this work, fully biobased aerogels (FBAs) were developed by using low-cost cellulose filament (CF), chitosan (CS), citric acid (CA), and a simple and scalable approach, for water remediation applications. The FBAs displayed superior mechanical properties (up to ∼65 kPa m³ kg^-1 specific Young's modulus and ∼111 kJ/m³ energy absorption) due to CA acting as a covalent crosslinker in addition to the natural hydrogen bonding and electrostatic interactions between CF and CS. The addition of CS and CA increased the variety of functional groups (carboxylic acid, hydroxyl and amines) on the materials' surface, resulting in super-high dye and heavy metal adsorption capacities (619 mg/g and 206 mg/g for methylene blue and copper, respectively). Further modification of FBAs with a simple approach using methyltrimethoxysilane endowed aerogel oleophilic and hydrophobic properties. The developed FBAs showed a fast performance in water and oil/organic solvents separation with more than 96% efficiency. Besides, the FBA sorbents could be regenerated and reused for multiple cycles without any significant impact on their performance. Moreover, thanks to the presence of amine groups by addition of CS, FBAs also displayed antibacterial properties by preventing the growth of Escherichia coli on their surface. This work demonstrates the preparation of FBAs from abundant, sustainable, and inexpensive natural resources for applications in wastewater purification.

Polysaccharide-Based Stimulus-Responsive Nanomedicines for Combination Cancer Immunotherapy

Cancer immunotherapy is a promising antitumor approach, whereas nontherapeutic side effects, tumor microenvironment (TME) intricacy, and low tumor immunogenicity limit its therapeutic efficacy. In recent years, combination immunotherapy with other therapies has been proven to considerably increase antitumor efficacy. However, achieving codelivery of the drugs to the tumor site remains a major challenge. Stimulus-responsive nanodelivery systems show controlled drug delivery and precise drug release. Polysaccharides, a family of potential biomaterials, are widely used in the development of stimulus-responsive nanomedicines due to their unique physicochemical properties, biocompatibility, and modifiability. Here, the antitumor activity of polysaccharides and several combined immunotherapy strategies (e.g., immunotherapy combined with chemotherapy, photodynamic therapy, or photothermal therapy) are summarized. More importantly, the recent progress of polysaccharide-based stimulus-responsive nanomedicines for combination cancer immunotherapy is discussed, with the focus on construction of nanomedicine, targeted delivery, drug release, and enhanced antitumor effects. Finally, the limitations and application prospects of this new field are discussed.

Control and prevention of microbially influenced corrosion using cephalopod chitosan and its derivatives: A review

Microbially influenced corrosion (MIC) of metals is an important industrial problem, causing 300-500 billion dollars of economic loss worldwide each year. It is very challenging to prevent or control the MIC in the marine environment. Eco-friendly coatings embedded with corrosion inhibitors developed from natural products may be a successful approach for MIC prevention or control. As a natural renewable resource, cephalopod chitosan has a number of unique biological properties, such as antibacterial, antifungal and non-toxicity effects, which attract scientific and industrial interests for potential applications. Chitosan is a positively charged molecule, and the negatively charged bacterial cell wall is the target of its antimicrobial action. Chitosan binds to the bacterial cell wall and disrupts the normal functions of the membrane by, for example, facilitating the leakage of intracellular components and impeding the transport of nutrients into the cells. Interestingly, chitosan is an excellent film-forming polymer. Chitosan may be applied as an antimicrobial coating substance for the prevention or control of MIC. Furthermore, the antimicrobial chitosan coating can serve as a basal matrix, in which other antimicrobial or anticorrosive substances like chitosan nanoparticles, chitosan silver nanoparticles, quorum sensing inhibitors (QSI) or the combination of these compounds, can be embedded to achieve synergistic anticorrosive effects. A combination of field and laboratory experiments will be conducted to test this hypothesis for preventing or controlling MIC in the marine environment. Thus, the proposed review will identify new eco-friendly MIC inhibitors and will assay their potential in future applications in the anti-corrosion industry.

Progresses in lignin, cellulose, starch, chitosan, chitin, alginate, and gum/carbon nanotube (nano)composites for environmental applications: A review

Water sources are becoming increasingly scarce, and they are contaminated by industrial, residential, and agricultural waste-derived organic and inorganic contaminants. These contaminants may pollute the air, water, and soil in addition to invading the ecosystem. Because carbon nanotubes (CNTs) can undergo surface modification, they can combine with other substances to create nanocomposites (NCs), including biopolymers, metal nanoparticles, proteins, and metal oxides. Furthermore, biopolymers are significant classes of organic materials that are widely used for various applications. They have drawn attention due to their benefits such as environmental friendliness, availability, biocompatibility, safety, etc. As a result, the synthesis of a composite made of CNT and biopolymers can be very effective for a variety of applications, especially those involving the environment. In this review, we reported environmental applications (including removal of dyes, nitro compounds, hazardous materialsو toxic ions, etc.) of composites made of CNT and biopolymers such as lignin, cellulose, starch, chitosan, chitin, alginate, and gum. Also, the effect of different factors such as the medium pH, the pollutant concentration, temperature, and contact time on the adsorption capacity (AC) and the catalytic activity of the composite in the reduction or degradation of various pollutants has been systematically explained.

Nano-chitin: Preparation strategies and food biopolymer film reinforcement and applications

Current trends in food packaging systems are toward biodegradable polymer materials, especially the food biopolymer films made from polysaccharides and proteins, but they are limited by mechanical strength and barrier properties. Nano-chitin has great economic value as a highly efficient functional and reinforcing material. The combination of nano-chitin and food biopolymers offers good opportunities to prepare biodegradable packaging films with enhanced physicochemical and functional properties. This review aims to give the latest advances in nano-chitin preparation strategies and its uses in food biopolymer film reinforcement and applications. The first part systematically introduces various preparation methods for nano-chitin, including chitin nanofibers (ChNFs) and chitin nanocrystals (ChNCs). The nano-chitin reinforced biodegradable films based on food biopolymers, such as polysaccharides and proteins, are described in the second part. The last part provides an overview of the current applications of nano-chitin reinforced food biopolymer films in the food industry.

Chitosan Composites with Bacterial Cellulose Nanofibers Doped with Nanosized Cerium Oxide: Characterization and Cytocompatibility Evaluation

In this work, new composite films were prepared by incorporating the disintegrated bacterial cellulose (BCd) nanofibers and cerium oxide nanoparticles into chitosan (CS) matrices. The influence of the amount of nanofillers on the structure and properties of the polymer composites and the specific features of the intermolecular interactions in the materials were determined. An increase in film stiffness was observed as a result of reinforcing the CS matrix with BCd nanofibers: the Young’s modulus increased from 4.55 to 6.3 GPa with the introduction of 5% BCd. A further increase in Young’s modulus of 6.7 GPa and a significant increase in film strength (22% increase in yield stress compared to the CS film) were observed when the BCd concentration was increased to 20%. The amount of nanosized ceria affected the structure of the composite, followed by a change in the hydrophilic properties and texture of the composite films. Increasing the amount of nanoceria to 8% significantly improved the biocompatibility of the films and their adhesion to the culture of mesenchymal stem cells. The obtained nanocomposite films combine a number of favorable properties (good mechanical strength in dry and swollen states, improved biocompatibility in relation to the culture of mesenchymal stem cells), which allows us to recommend them for use as a matrix material for the culture of mesenchymal stem cells and wound dressings.

Estrogen adsorption from an aqueous solution on the chitosan nanoparticles

In this research, chitosan nanoparticles as an efficient and reusable adsorbent with adsorption capacity of 5.79 mg/g, surface area of 62 m²/g and pH_pzc of 8.07 were applied to remove the ethinylestradiol (as a sample of estrogen) from an aqueous wastewater. The chitosan nanoparticles were characterized by SEM, XRD and FT-IR analyses. Four independent variables involving contact time, adsorbent dosage, pH, and initial concentration of estrogen were applied to design the experiments by Design Expert software (CCD under RSM). In fact, number of experiments was minimized and the operating conditions were optimized for the maximum estrogen removal. The results indicated that three independent variables (contact time, adsorbent dosage, and pH) increment increased the estrogen removal while the estrogen initial concentration enhancement decreased the removal due to the concentration polarization phenomenon. The optimum conditions for the estrogen removal (92.50 %) on the chitosan nanoparticles were found at contact time of 220 min, adsorbent dosage of 1.45 g/l, pH of 7.3 and estrogen initial concentration of 5.7 mg/l. Moreover, the Langmuir isotherm and pseudo-second order models could properly legitimize estrogen adsorption process on the chitosan nanoparticles.

Fluorinated carboxymethyl chitosan-based nano-prodrugs for precisely synergistic chemotherapy

The clinical transformation of polysaccharide-based nano-prodrugs remains a long way off, due to the shackles on easy metabolic clearance, dilemma of dose-dependent toxicity and immunogenicity, and poor tumor selectivity. To address these challenges, the fluorinated dual-crosslinked carboxymethyl chitosan (CMCS)-based nano-prodrugs with precise structure were facilely developed through the reaction of CMCS with water-soluble stimuli-responsive synergistic small molecule prodrug (Pt(IV)-1), glutaraldehyde and heptafluorobutyric anhydride successively. The fluorination enabled the nano-prodrugs to display metabolic stability and improve tumoral cellular uptake. The pH/glutathione (GSH)-sensitive dual-crosslinked structure enabled the nano-prodrugs to show physicochemical stability at physiological pH, selective drug release and synergistic cytotoxicity at tumoral intracellular pH/GSH, and circumventing the dilemma of dose-dependent toxicity and immunogenicity induced by that crosslinked or grafted via a single drug. These superior performances promoted stability in long-term storage and circulation, normal blood routine and aminotransferase, fantastic hemocompatibility, selective tumor accumulation and precisely synergistic chemotherapy, therefore achieving significant tumor growth inhibition while minimizing side effects. Thus, the precise fluorinated dual-crosslinked CMCS-based nano-prodrugs have great potential for selective clinical cancer treatment.

Chitosan-based nanoscale systems for doxorubicin delivery: Exploring biomedical application in cancer therapy

Green chemistry has been a growing multidisciplinary field in recent years showing great promise in biomedical applications, especially for cancer therapy. Chitosan (CS) is an abundant biopolymer derived from chitin and is present in insects and fungi. This polysaccharide has favorable characteristics, including biocompatibility, biodegradability, and ease of modification by enzymes and chemicals. CS-based nanoparticles (CS-NPs) have shown potential in the treatment of cancer and other diseases, affording targeted delivery and overcoming drug resistance. The current review emphasizes on the application of CS-NPs for the delivery of a chemotherapeutic agent, doxorubicin (DOX), in cancer therapy as they promote internalization of DOX in cancer cells and prevent the activity of P-glycoprotein (P-gp) to reverse drug resistance. These nanoarchitectures can provide co-delivery of DOX with antitumor agents such as curcumin and cisplatin to induce synergistic cancer therapy. Furthermore, co-loading of DOX with siRNA, shRNA, and miRNA can suppress tumor progression and provide chemosensitivity. Various nanostructures, including lipid-, carbon-, polymeric- and metal-based nanoparticles, are modifiable with CS for DOX delivery, while functionalization of CS-NPs with ligands such as hyaluronic acid promotes selectivity toward tumor cells and prevents DOX resistance. The CS-NPs demonstrate high encapsulation efficiency and due to protonation of amine groups of CS, pH-sensitive release of DOX can occur. Furthermore, redox- and light-responsive CS-NPs have been prepared for DOX delivery in cancer treatment. Leveraging these characteristics and in view of the biocompatibility of CS-NPs, we expect to soon see significant progress towards clinical translation.

Nanochitin and Nanochitosan: Chitin Nanostructure Engineering with Multiscale Properties for Biomedical and Environmental Applications

Nanochitin and nanochitosan (with random-copolymer-based multiscale architectures of glucosamine and N-acetylglucosamine units) have recently attracted immense attention for the development of green, sustainable, and advanced functional materials. Nanochitin and nanochitosan are multiscale materials from small oligomers, rod-shaped nanocrystals, longer nanofibers, to hierarchical assemblies of nanofibers. Various physical properties of chitin and chitosan depend on their molecular- and nanostructures; translational research has utilized them for a wide range of applications (biomedical, industrial, environmental, and so on). Instead of reviewing the entire extensive literature on chitin and chitosan, here, recent developments in multiscale-dependent material properties and their applications are highlighted; immune, medical, reinforcing, adhesive, green electrochemical materials, biological scaffolds, and sustainable food packaging are discussed considering the size, shape, and assembly of chitin nanostructures. In summary, new perspectives for the development of sustainable advanced functional materials based on nanochitin and nanochitosan by understanding and engineering their multiscale properties are described.