Nanochitin: Chemistry, Structure, Assembly, and Applications

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.

Removal of Ni2+ and Cd2+ from aqueous solutions by bionanosorbents: Isotherm, thermodynamic and mechanistic studies

The present work presents the efficiency and the limit in using bionanosorbents (cellulose, chitin and modified chitin nanocrystals) for the sorption of metal ions M2+ (M = Ni and Cd) in batch systems. Bionanosorbents were extracted from plants and shrimp shells, two available and low-cost materials. If cellulose and chitin nanocrystals did not efficiently remove metals in the experimental conditions of this work, the surface-modified chitin exhibited enhancement for the Ni2+ and Cd2+ adsorption capacity than original chitin nanocrystals. The Langmuir and Freundlich models fitted well to the experimental data from which the maximum adsorption capacity was 139.2 mg Ni g-1 and 38.4 mg Cd g-1. Regarding the Gibbs free energy and the Hall parameter, the sorption of Ni2+ and Cd2+ were spontaneous and favourable for pH around the neutrality. This corroborates the examination of IR spectra of oxidized chitin nanocrystals before and after the sorption process from which the metal removal mechanism was mainly attributed to the formation of complexes and ion exchanges of the bionanosorbent and metal ions. Element mappings of the bionanosorbents after sorption revealed a homogeneous distribution of Cd(II).

Composition of the pretreatment solvent and the structural features of substrates and chitinases influence the bioconversion of α-chitin

Auxiliary domains in chitinases play a significant role in the hydrolysis of chitin and chitooligosaccharides (COS). Pretreatment of α-chitin, followed by enzymatic hydrolysis, considerably enhanced the production of COS with a lower degree of polymerization (DP). We studied the effect of pretreatment solvent composition (KOH-with/without-urea) on the bioconversion of α-chitin and hydrolysis of COS (DP2-6), separately by a multi-modular chitinase CsChiG and its catalytic domain (Cat-CsChiG). Temperature-dependent structural stability of CsChiG and Cat-CsChiG was analyzed using circular dichroism spectroscopy. Deletion of chitin-binding domains in CsChiG influenced the overall secondary structural elements and its thermal stability, affecting the bioconversion of treated substrates and hydrolysis of lower chain length COS. Field emission scanning electron microscope (FESEM) and thermogravimetric analysis-differential thermal analysis (TGA-DTA) corroborate the influence of pretreatment on the structural and thermal stabilities of the pretreated substrates. It is, therefore, concluded that the composition of the pretreatment solvent and structural features of the substrates and modules in the chitinases influence the bioconversion of α-chitin, especially the composition of COS.

Infrared Free-Electron Laser: A Versatile Molecular Cutter for Analyzing Solid-State Biomacromolecules

Free-electron lasers that oscillate in the infrared (IR) range of 1000 (10 μm) to 4000 cm-1 (2.5 μm) were applied to irradiate solid-phase polysaccharides and aromatic biomacromolecules. Synchrotron radiation IR microscopy (SR-IRM) and electrospray ionization mass spectroscopy (ESI-MS) analyses showed that N-acetyl glucosamine was isolated from the powdered exoskeleton of crayfish by irradiation at 1020 cm-1 (9.8 μm), resonating with the C-O stretching mode (νC-O). Irradiation at 3448 cm-1 (2.9 μm), which is resonant with the O-H stretching vibration (νO-H) of sulfonated lignin, dissociates the aggregate state and releases coniferyl aldehyde substituted with sulfinate, as shown by scanning electron microscopy, terahertz-coherent edge radiation spectroscopy, SR-IRM, and ESI-MS. These vibrational excitation reactions proceed at room temperature in the absence of solvent. Current and previous studies have demonstrated that intense IR lasers can be used as versatile tools for unveiling the internal structures of persistent biomacromolecules.

Nano-fibrous biopolymers as building blocks for gel networks: Interactions, characterization, and applications

Biopolymers derived from natural resources are highly abundant, biodegradable, and biocompatible, making them promising candidates to replace non-renewable fossil fuels and mitigate environmental and health impacts. Nano-fibrous biopolymers possessing advantages of biopolymers entangle with each other through inter-/intra-molecular interactions, serving as ideal building blocks for gel construction. These biopolymer nanofibers often synergize with other nano-building blocks to enhance gels with desirable functions and eco-friendliness across various applications in biomedical, environmental, and energy sectors. The inter-/intra-molecular interactions directly affect the assembly of nano-building blocks, which determines the structure of gels, and the integrity of connected nano-building blocks, influencing the mechanical properties and the performance of gels in specific applications. This review focuses on four biopolymer nanofibers (cellulose, chitin, silk, collagen), commonly used in gel preparations, as representatives for polysaccharides and polypeptides. The covalent and non-covalent interactions between biopolymers and other materials have been categorized and discussed in relation to the resulting gel network structures and properties. Nanomechanical characterization techniques, such as surface forces apparatus (SFA) and atomic force microscopy (AFM), have been employed to precisely quantify the intermolecular interactions between biopolymers and other building blocks. The applications of these gels are classified and correlated to the functions of their building blocks. The inter-/intra-molecular interactions act as "sewing threads", connecting all nano-building blocks to establish suitable network structures and functions. This review aims to provide a comprehensive understanding of the interactions involved in gel preparation and the design principles needed to achieve targeted functional gels.

Selective nucleation of chitin nanocrystals in the crystallization of poly(ε-caprolactone-b-l-lactide) diblock copolymer composites

Rod-like chitin nanocrystals (ChNCs) filled biodegradable aliphatic polyesters are of great interest because as-obtained nanocomposites are all-degradable. In this work, we prepared a poly(ε-caprolactone-b-l-lactide) (PCL-b-PLA) copolyester nanocomposite with ChNCs and carried out a crystallization study. The results disclosed that the roles of ChNCs played during crystallization of copolyester matrices were very attractive: as heterogeneous nucleator of PLA phase, whereas as inert filler for PCL phase. Thus, the overall crystallization kinetics of PLA phase were accelerated. The heterogeneous nucleation led to the formation of more amounts of crystallized PLA domains, which favored nucleating following crystallization of PCL phase. In addition, the presence of ChNCs did not strongly influence the microphase-segregated structure of PCL-b-PLA, and had good reinforcements to matrix copolymer. The selective nucleation ability of ChNCs reported in this study is valuable for regulating the structures and properties of nanocomposites based on the ChNCs-filled aliphatic diblock copolyester with double crystalline blocks.

The application of chitin materials in enzymatic catalysis: A review

Enzymatic catalysis offers notable advantages, including exceptional catalytic efficiency, selectivity, and the ability to operate under mild conditions. However, its widespread application is hindered by the high costs associated with enzymes and cofactors. Materials-mediated immobilization technology has proven effective in the recycling of enzymes and cofactors. An optimal carrier material for protein immobilization must be non-toxic, biocompatible, and should not compromise the biological activity or structure of the enzymes. Compared to synthetic polymers, chitin is a promising carrier given its low cost, renewability, abundance of functional groups, and notable biocompatibility and biodegradability. Although numerous reviews on chitosan and other polymers for immobilization have been published, few have addressed using chitin as supports. In this review, chitin-based materials mediated enzyme immobilization, the one-step purification and immobilization of enzymes, as well as co-immobilization of enzymes and cofactors were summarized. Particularly, the significance of chitin materials in the field of enzymatic catalysis was emphasized. This study has the potential to open new avenues for immobilized biocatalysts.

Bridging Electrolyte Bulk and Interfacial Chemistry: Dynamic Protective Strategy Enable Ultra-Long Lifespan Aqueous Zinc Batteries

The main bottleneck of rechargeable aqueous zinc batteries (AZBs) is their limited cycle lifespans stemming from the unhealthy electrolyte bulk and fragile interface, especially in the absence of dynamic protection mechanism between them. To overcome this limitation, benefitting from their synergistic physical and chemical properties, chitin nanocrystals (ChNCs) are employed as superior colloid electrolyte to bridge electrolyte bulk and interfacial chemistry for ultra-long lifespan AZBs. This unique strategy not only enables continuous optimization of the electrolyte bulk and interfacial chemistry within the battery but also facilitates self-repairing of mechanical damage both internally and externally, thereby achieving comprehensive, persistent, and dynamic protection. As a result, the modified zinc (Zn) cells present high Zn plating/stripping coulombic efficiencies of 97.71 % ~99.81 % from 5 to 100 mA cm-2, and remarkably service lifespan up to 8,200 h (more than 11 months). Additionally, the Zn//MnO2 full cell exhibits a high capacity retention of 70.1 % after 3,000 cycles at 5 A g-1. This dynamic protective strategy to challenge aqueous Zn chemistry may open up a new avenue for building better AZBs and beyond.

Proteomic insights into nematode-trapping fungi Arthrobotrys oligospora after their response to chitin

Introduction

Nematode-trapping fungi (NTFs) can produce various chitinases to degrade nematode body wall and eggshell chitin during predation. However, the regulatory mechanisms of their expression of chitinases still remain unclear. The primary objective of this study was to elucidate the differential protein profile of A. oligospora, an NTF, in response to chitin.

Material and Methods

Colloidal chitin was added to induce the culture of A. oligospora, and the phenotypic differences before and after induction were observed under inverted microscope. The differential proteins before and after mycelium induction were screened by liquid chromatography-tandem mass spectrometry. The differentially expressed chitinase was expressed in Pichia yeast, and the recombinant enzyme was incubated with Caenorhabditis elegans and its egg suspension to explore its biological activity.

Results

It was found that there was a significant acceleration in the mycelial growth post chitin interaction in A. oligospora. A total of 1,124 differentially expressed proteins (DEPs) were identified between the control group (AO-c) and the experimental group (AO-e), with 183 upregulated and 941 downregulated. Gene Ontology analysis revealed that the DEPs acted in various metabolic processes with catalysis and binding functions. Kyoto Encyclopedia of Genes and Genomes analysis associated these proteins primarily with signalling pathways related to glucose metabolism. Three chitinases were significantly modulated among DEPs. Moreover, enzymatic activity assays demonstrated that one of them effectively degraded C. elegans and its eggs.

Conclusion

These findings suggest that A. oligospora can significantly alter its protein expression profile in response to chitin, thereby facilitating its sugar metabolism and mycelial development. Our study provided new insights into the regulatory mechanisms of nematode predation in A. oligospora.

A nanochitin-drived natural biological adhesive with high cohesive for wound healing

The weak cohesive strength of tissue adhesives hinders their practical applications. To overcome this challenge, we develop a green bio-adhesive that balances both cohesion and adhesion, drawing inspiration from the natural adhesion mechanisms of mussels. This bio-adhesive, referred to as OTS, was ingeniously crafted through the co-assembly of multi-surface-charged chitin nanofibers (OAChN) and tannic acid (TA), integrated with silk fibroin (SF), resulting in a material with enhanced cohesive strength and robust adhesive properties. The adhesive achieved significant cohesion through hydrogen-bonded crosslinking among OAChN, SF, and TA, boasting a tensile strength of 24.53 KPa and allowing for 150 % elastic deformation. OTS adheres effectively to diverse complex surfaces, with adhesive strengths of 14.55 MPa underwater and 8.83 MPa in air, demonstrating excellent versatility. The biocompatibility and degradability of OTS were confirmed by a wound healing model in SD rats, showing no nanotoxicity and effectively promoting wound healing, rapid hemostasis, and sealing. This green adhesive strategy offers a novel approach to augmenting the cohesive strength of tissue adhesives suitable for complex conditions and has potential medical applications ranging from rapid hemostasis to wound healing enhancement.

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.

Bioinspired Nanochitin-Based Porous Constructs for Light-Driven Whole-Cell Biotransformations

Solid-state photosynthetic cell factories (SSPCFs) are a new production concept that leverages the innate photosynthetic abilities of microbes to drive the production of valuable chemicals. It addresses practical challenges such as high energy and water demand and improper light distribution associated with suspension-based culturing; however, these systems often face significant challenges related to mass transfer. The approach focuses on overcoming these limitations by carefully engineering the microstructure of the immobilization matrix through freeze-induced assembly of nanochitin building blocks. The use of nanochitins with optimized size distribution enabled the formation of macropores with lamellar spatial organization, which significantly improves light transmittance and distribution, crucial for maximizing the efficiency of photosynthetic reactions. The biomimetic crosslinking strategy, leveraging specific interactions between polyphosphate anions and primary amine groups featured on chitin fibers, produced mechanically robust and wet-resilient cryogels that maintained their functionality under operational conditions. Various model biotransformation reactions leading to value-added chemicals are performed in chitin-based matrix. It demonstrates superior or comparable performance to existing state-of-the-art matrices and suspension-based systems. The findings suggest that chitin-based cryogel approach holds significant promise for advancing the development of solid-state photosynthetic cell factories, offering a scalable solution to improve the efficiency and productivity of light-driven biotransformation.

Nanochitin From Crab Shells: Production, Chemical Modification, Composite Materials, and Physiological Functions

Large quantities of crab shells are generated in food-processing plants. In this review, the authors summarize a series of research findings on the production of nanochitin, its physical properties, chemical modifications, and functions, which have not been fully addressed in existing literature. Nanochitin, which has a width of 10 nm, is derived from chitin, the main component of crab shells, using a technology similar to that used to produce nanocellulose from wood. Unlike conventional chitin, nanochitin is well dispersed in water, making it easy to mold and process into various products for different applications. They can also be modified for specific uses through processes such as acylation and etherification to enhance their physical properties and add functionality. Nanochitin, which are known for their exceptional mechanical strength, can be blended with resins to create composite films with improved strength and elasticity. These films maintain the transparency of the resin, reduce its thermal expansion, and offer reinforcement. Chitin and its derivative chitosan are used as wound dressings, hemostatic agents, and health foods. Nanochitin and its deacetyl derivatives have diverse functions such as topical medicine for the skin, ingestion as a health food, and use as pesticides or fertilizers for plants.

Advanced chitin-based composite hydrogels enabled by quercetin-mediated assembly for multifunctional applications

Natural building blocks like chitins for self-assembling into complex materials have garnered significant interest owing to the inherent and diverse functionalities. However, challenges persist in the assembly of chitin-based composites, primarily stemming from chitin's poor solubility and compatibility. Herein, a quercetin-mediated multiple crosslinking strategy was developed to enhance compatibility by quercetin-mediated interfacial interactions between chitin and inorganic materials, achieving a series of chitin-based composite hydrogels with high performances. The quercetin-mediated strategy could effectively modulate the non-covalent interactions within hydrogel, which served as the sacrificial bonds to dissipate large energy, leading to the high toughness of chitin-based composite hydrogels (0.70-1.02 MJ·m-3). Furthermore, through utilizing quercetin-assisted non-covalent interactions, effective dispersion of inorganic materials (e.g., molybdenum disulfide, carbon nanotube and calcium carbonate) within hydrogels was achieved, resulting in composite hydrogels with diverse functionalities. Our quercetin-mediated strategy conceptualized in this work paves the way for the development of a diverse array of chitin-based composite hydrogels which incorporate various functional inorganic materials.

Mucoadhesive polyelectrolyte complexes of fucoidan and chitin nanowhiskers to prolong the antiprotozoal activity of metronidazole

The improvement of the specific pharmacological activity of agents with antimicrobial and antiprotozoal properties (e.g. metronidazole, MET) is of interest for clinical applications in the treatment of bacterial infections. In this work, we prepared the polyelectrolyte complexes (PEC) based on chitin nanowhiskers (CNW) and fucoidan (FUC) with hydrodynamic diameters of 244 and 816 nm, a ζ-potential of about -22 mV and good mucoadhesive properties. The incorporation of MET into PEC particles promoted the sustained release of MET for 10 h and maintained the antiprotozoal activity against clinical isolates of Trichomonas vaginalis for up to 10 h. At concentrations of 1-3 mg/mL, the CWN-FUC-MET particles showed no cytotoxicity (HeLa cell line). The sustained drug release rate, combined with pronounced mucoadhesive properties, improved pharmacological activity, and non-cytotoxicity makes the developed biopolymer delivery systems promising candidates for further clinical trials.

Biopolymer-Derived Carbon Materials for Wearable Electronics

Advanced carbon materials are widely utilized in wearable electronics. Nevertheless, the production of carbon materials from fossil-based sources raised concerns regarding their non-renewability, high energy consumption, and the consequent greenhouse gas emissions. Biopolymers, readily available in nature, offer a promising and eco-friendly alternative as a carbon source, enabling the sustainable production of carbon materials for wearable electronics. This review aims to discuss the carbonization mechanisms, carbonization techniques, and processes, as well as the diverse applications of biopolymer-derived carbon materials (BioCMs) in wearable electronics. First, the characteristics of four representative biopolymers, including cellulose, lignin, chitin, and silk fibroin, and their carbonization processes are discussed. Then, typical carbonization techniques, including pyrolysis carbonization, laser-induced carbonization, Joule heating carbonization, hydrothermal transformation, and salt encapsulation carbonization are discussed. The influence of the processes on the morphology and properties of the resultant BioCMs are summarized. Subsequently, applications of BioCMs in wearable devices, including physical sensors, chemical sensors, energy devices, and display devices are discussed. Finally, the challenges currently facing the field and the future opportunities are discussed.

Aldehyde-functionalization of chitin nanocrystals via SI-ARGET ATRP of lignin-derived monomers

Chitin nanocrystals (ChNCs), prepared from a down-sizing process from chitin, have recently captured great attention to access sustainable nanomaterials. The surface modification of ChNCs is crucial to regulate the surface physicochemical properties and introduce specific functions, thus satisfying their diverse applications. In this study, aldehyde-functionalized ChNCs (ChNCs-PVMA) with enhanced hydrophobicity were developed via surface-initiated activators regenerated by electron transfer for atom transfer radical polymerization (SI-ARGET ATRP) of a lignin-derived polymerizable aldehyde monomer, vanillin methacrylate (VMA). The monomer conversion was determined by 1H NMR spectroscopy of the reaction mixture based on the change of the relative ratio of VMA and solvent signals. The prepared ChNCs-PVMA were systematically characterized by FTIR, CP/MAS 13C NMR, XPS, XRD, DSC, TGA, and TEM. The dispersibility of ChNCs and ChNCs-PVMA in water and DMF was evaluated by dynamic light scattering and visual observation, indicating good dispersion of ChNCs-PVMA in organic solvents. Furthermore, based on the available aldehyde groups, the ChNCs-PVMA was reacted with amino acids via Schiff base reaction, demonstrating a rich follow-up chemistry towards diverse functions by the reactive aldehyde groups.

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.

Loosening the Solvation Cage in Polysaccharide Polymer Electrolyte for Sustainable Lithium Metal Batteries

Biomass with naturally ion-conducting segments (e.g., hydroxyl) holds promise for sustainable batteries. Several expeditions are proposed to successfully enhance the ion conduction in biomass polymer mainly by intermolecular structure regulation. Presently, the recognition and research of biomass polymer electrolytes are still limited, requiring continuous explorations to promote the application of such promising electrolytes. Herein, a molecularly asymmetric electrolyte is produced, comprising polysaccharides of starch and chitosan. The strong Li+-O (hydroxyl) interactions are replaced by weak Li+-oxygen (O) of ester carbonyl, and the steric hindrance group -NH3 + promotes the immobilization of anion and stabilization of the interface. Such intermolecular chemical modulations of biomass are achieved by a one-pot esterification and protonation of polysaccharides. A loosely-solvating cage structure with the participation of O of ester carbonyl, glycerol, and anion, allowing the rapid conduction (1.82 × 10-4 S cm-1 at 30 °C) and a high migration number (0.49) of Li+. Moreover, Li symmetric cells (2500 h) and Li4TiO5 | Li cells (400 cycles) employing the SCA electrolyte show superior cycling stability. The polysaccharide BPEs and solvation regulation strategy open up a promising avenue for constructing sustainable batteries.

Extraction of Natural-Based Raw Materials Towards the Production of Sustainable Man-Made Organic Fibres

Bioresources have been gaining popularity due to their abundance, renewability, and recyclability. Nevertheless, given their diverse composition and complex hierarchical structures, these bio-based sources must be carefully processed to effectively extract valuable raw polymeric materials suitable for producing man-made organic fibres. This review will first highlight the most relevant bio-based sources, with a particular focus on promising unconventional biomass sources (terrestrial vegetables, aquatic vegetables, fungi, and insects), as well as agroforestry and industrial biowaste (food, paper/wood, and textile). For each source, typical applications and the biopolymers usually extracted will also be outlined. Furthermore, acknowledging the challenging lignocellulosic structure and composition of these sources, an overview of conventional and emerging pre-treatments and extraction methods, namely physical, chemical, physicochemical, and biological methodologies, will also be presented. Additionally, this review aims to explore the applications of the compounds obtained in the production of man-made organic fibres (MMOFs). A brief description of their evolution and their distinct properties will be described, as well as the most prominent commercial MMOFs currently available. Ultimately, this review concludes with future perspectives concerning the pursuit of greener and sustainable polymeric sources, as well as effective extraction processes. The potential and main challenges of implementing these sources in the production of alternative man-made organic fibres for diverse applications will also be highlighted.

Gas evolution in self-extinguishing and insulative nanopolysaccharide-based hybrid foams

Lightweight, energy-efficient materials in building construction typically include polymeric and composite foams. However, these materials pose significant fire hazards due to their high combustibility and toxic gas emissions, including carbon monoxide and hydrogen cyanide. This study delves into the latter aspects by comparing hybrid systems based on nanofiber-reinforced silica-based Pickering foams with a synthetic reference (polyurethane foams). The extent and dynamics of fire retardancy and toxic gas evolution were assessed, and the results revealed the benefits of combining the thermal insulation of silica with the structural strength of biobased nanofibers, the latter of which included anionic and phosphorylated cellulose as well as chitin nanofibers. We demonstrate that the nanofiber-reinforced silica-based Pickering foams are thermal insulative and provide both fire safety and energy efficiency. The results set the basis for the practical design of hybrid foams to advance environmental sustainability goals by reducing energy consumption in built environments.

Influences of Coagulant Polarity on the Modulus of the Chitin Hydrogel

The chitin hydrogel draws great attention in biomedical fields owing to its high similarity and good affinity for peptides. The conversion of raw chitin to the designed hydrogel through a sol-gel process prevails, while the modulus of the chitin hydrogel is significantly influenced by the factors of gelation technology (i.e., coagulation, involving polymer chain rearrangement and the reconstruction of multiple interactions). Water and several organic solvents such as ethanol, DMAc, and DMSO are effective coagulants for aqueous chitin/KOH/urea solutions. In particular, the concentration of aqueous ethanol solutions displays a high dependency on the modulus of chitin hydrogels. However, recent reports about chitin hydrogel fabrication seldom demonstrate the effect of coagulant factors on hydrogel performance. Our study found that the polarity of the coagulant and its diffusion index for entry into the chitin solution during the coagulation process had a direct influence on the hydrogel modulus. The influence of the two factors was investigated to find out their quantified relationship with the hydrogel modulus, which will inspire a practical method to develop new coagulants to prepare modulus-manipulable chitin hydrogels.

Refined Industrial Tannins via Sequential Fractionation: Exploiting Well-Defined Molecular Structures for Controlled Performance in Pickering Emulsions Costabilized with Chitin Nanofibrils

Tannins from Acacia mearnsii (black wattle) are one of the few industrially available sources of nonlignin polyphenols. The intrinsic chemical heterogeneity and high dispersity of industrial tannins complicate their use in applications where the reactivity or colloidal interactions need to be precisely controlled. Here, we employ a solubility-centered sequential fractionation to obtain homogeneous tannin fractions with a dispersity index lower than 2. The well-defined and homogeneous fractions were characterized using NMR and MALDI-TOF and were used to prepare Pickering emulsions by costabilization with chitin nanofibrils. We demonstrate that the emulsion droplet size and associated properties can be tuned by using tannin fractions of varied molar mass, which is a result of fine control over the tannin-chitin complexation interactions at the oil-water interface. In addition to enhancing emulsion stability, the addition of tannin to chitin-stabilized Pickering emulsions has proven to be a viable strategy for engineering the emulsion's viscoelastic properties, as well as introducing antioxidative properties. Overall, we demonstrate a facile method to finely control the properties of industrial tannins and enable their customization to allow their utilization in high-performance multiphase systems.

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.

Revivable self-assembled supramolecular biomass fibrous framework for efficient microplastic removal

Microplastic remediation in aquatic bodies is essential for the entire ecosystem, but is challenging to achieve with a universal and efficient strategy. Here, we developed a sustainable and environmentally adaptable adsorbent through supramolecular self-assembly of chitin and cellulose. This biomass fibrous framework (Ct-Cel) showcases an excellent adsorption performance for polystyrene, polymethyl methacrylate, polypropylene, and polyethylene terephthalate. The affinity for diverse microplastics is attributed to the transformation of multiple intermolecular interactions between different microplastics and Ct-Cel. Meanwhile, the strong resistance of Ct-Cel to multiple pollutants in water enables an enhanced adsorption when coexisting with microorganisms and Pb2+. Moreover, Ct-Cel can remove 98.0 to 99.9% of microplastics in four types of real water and maintains a high removal efficiency of up to 95.1 to 98.1% after five adsorption cycles. This work may open up prospects for functional biomass materials for cost-efficient remediation of microplastics in complex aquatic environments.

Recent Advances of Bio-Based Hydrogel Derived Interfacial Evaporator for Sustainable Water and Collaborative Energy Storage Applications

Solar interfacial evaporation strategy (SIES) has shown great potential to deal with water scarcity and energy crisis. Biobased hydrogel derived interfacial evaporator can realize efficient evaporation due to the unique structure- properties relationship. As such, increasing studies have focused on water treatment or even potential accompanying advanced energy storage applications with respect of efficiency and mechanism of bio-based hydrogel derived interfacial evaporation from microscale to molecular scale. In this review, the interrelationship between efficient interfacial evaporator and bio-based hydrogel is first presented. Then, special attention is paid on the inherent molecular characteristics of the biopolymer related to the up-to-date studies of promising biopolymers derived interfacial evaporator with the objective to showcase the unique superiority of biopolymer. In addition, the applications of the bio-based hydrogels are highlighted concerning the aspects including water desalination, water decontamination atmospheric water harvesting, energy storage and conversion. Finally, the challenges and future perspectives are given to unveil the bottleneck of the biobased hydrogel derived SIES in sustainable water and other energy storage applications.

Evaluating the strategies to improve strength and water-resistance of chitin nanofibril assembled structures: Molecule-bridging, heat-treatment and deacidifying

Chitin nanofibril (ChiNF) is a promising building block used to fabricate chitin fibers, films or gels via self-assembly from its aqueous suspension. Although mechanical strengthening of its assembled structures has made great advances, the unsatisfactory water-resistance is still a crucial obstacle to practical application and even rarely referred to. Herein, ChiNF was prepared via deacetylation-ultrasonication treatment and the strategies of molecule-bridging, heat-treatment and deacidifying that aiming to improve the strength and water-resistance of its assembled films were evaluated. Molecule-bridging, including tannic acid (TA) or/and chitosan (CS), improved the mechanical properties to some extent, but had no obvious positive effects on water-resistance; heat-treatment was a useful route to enhance both strength and water-resistance; interestingly, deacidifying was more efficient than heat-treatment with respect to improving strength and water-resistance, implying the presence of acid was the major reason for deteriorating assembled structures. Combining molecule-bridging, deacidifying and heat-treatment produced a strong ChiNF-TA/CS cast film with excellent water-resistance. Different from the commonly-used approach of vacuum filtration, these strategies are very suitable for large-scale production of the ChiNF-based self-supported films or coatings via solution casting. Furthermore, the reverse dialysis deacidification simultaneously produced highly concentrated suspensions suitable for dry-spinning, and thus strong chitin macrofibers were successfully fabricated.

Water-in-water emulsions stabilized by nano-chitin

A water-in-water (W/W) emulsion consists of microdroplets was formed by the spontaneous liquid-liquid separation by mixing polyacrylic acid and chitosan oligosaccharide in water, and these microdropletes were stabilized by nano-chitin, formed water-in-water Pickering emulsions. By taking the advantage of interfacial adsorption of nano-chitin, the W/W emulsion droplets composed of polyacrylic acid/chitosan oligosaccharide (COS/PAA) polyelectrolyte coacervate were successfully stabilized. Research results indicated that composite microspheres were formed by the nano-chitin stabilized COS/PAA emulsion, and the size of these composite microspheres was related to the concentration and morphology of the nano-chitin. As the concentration of nano-chitin increases, the size of the composite microspheres first increases and then decreases, gradually becoming more uniform; whereas a decrease in the length of nano-chitin will lead to an increase in the size of the composite microspheres. The formation of composite microspheres may be due to the electrostatic interactions between nano-chitin and the emulsion droplets. In addition, the composite microspheres exhibit the best release effect for berberine hydrochloride at a pH value of 3.

Gelatin-chitosan interactions in edible films and coatings doped with plant extracts for biopreservation of fresh tuna fish products: A review

The preservation of tuna fish products, which are extremely perishable seafood items, is a substantial challenge due to their instantaneous spoilage caused by microbial development and oxidative degradation. The current review explores the potential of employing chitosan-gelatin-based edible films and coatings, which are enriched with plant extracts, as a sustainable method to prolong the shelf life of tuna fish products. The article provides a comprehensive overview of the physicochemical properties of chitosan and gelatin, emphasizing the molecular interactions that underpin the formation and functionality of these biopolymer-based films and coatings. The synergistic effects of combining chitosan and gelatin are explored, particularly in terms of improving the mechanical strength, barrier properties, and bioactivity of the films. Furthermore, the application of botanical extracts, which include high levels of antioxidants and antibacterial compounds, is being investigated in terms of their capacity to augment the protective characteristics of the films. The study also emphasizes current advancements in utilizing these composite films and coatings for tuna fish products, with a specific focus on their effectiveness in preventing microbiological spoilage, decreasing lipid oxidation, and maintaining sensory qualities throughout storage. Moreover, the current investigation explores the molecular interactions associated with chitosan-gelatin packaging systems enriched with plant extracts, offering valuable insights for improving the design of edible films and coatings and suggesting future research directions to enhance their effectiveness in seafood preservation. Ultimately, the review underscores the potential of chitosan-gelatin-based films and coatings as a promising, eco-friendly alternative to conventional packaging methods, contributing to the sustainability of the seafood industry.

Bioinspired triple-layered membranes for periodontal guided bone regeneration applications

Barrier membranes have been used for the treatment of alveolar bone loss caused by periodontal diseases or trauma. However, an optimal barrier membrane must satisfy multiple requirements simultaneously, which are challenging to combine into a single material. We herein report the design of a bioinspired membrane consisting of three functional layers. The primary layer is composed of clay nanosheets and chitin, which form a nacre-inspired laminated structure. A calcium phosphate mineral layer is deposited on the inner surface of the nacre-inspired layer, while a poly(lactic acid) layer is coated on the outer surface. The composite membrane integrates good mechanical strength and deformability because of the nacre-inspired structure, facilitating operations during the implant surgery. The mineral layer induces the osteogenic differentiation of bone marrow mesenchymal stem cells and increases the stiffness of the membrane, which is an important factor for the regeneration process. The poly(lactic acid) layer can prevent unwanted mineralization on the outer surface of the membrane in oral environments. Cell experiments reveal that the membrane exhibits good biocompatibility and anti-infiltration capability toward connective tissue/epithelium cells. Furthermore, in vitro analyses show that the membrane does not degrade too fast, allowing enough time for bone regeneration. In vivo experiments prove that the membrane can effectively induce better bone regeneration and higher trabecular bone density in alveolar bone defects. This study demonstrates the potential of this bioinspired triple-layered membrane with hierarchical structures as a promising barrier material for periodontal guided tissue regeneration.

Chitin/Chitosan Nanofibers Toward a Sustainable Future: From Hierarchical Structural Regulation to Functionalization Applications

Owing to its multiple fascinating properties of renewability, biodegradability, biocompatibility, and antibacterial activity, chitin is expected to become a green cornerstone of next-generation functional materials. Chitin nanofibers, as building blocks, form multiscale hierarchical structures spanning nano- and macrolevels in living organisms, which pave the way for sophisticated functions. Therefore, from a biomimetic perspective, exploiting chitin nanofibers for use in multifunctional, high-performance materials is a promising approach. Here, we first summarize the latest advances in the multiscale hierarchical structure assembly mode of chitin and its derivative nanofibers, including top-down exfoliation and bottom-up synthesis. Subsequently, we emphasize the environmental impacts of these methods, which are crucial for whether chitin nanofibers can truly contribute to a more eco-friendly era. Furthermore, the latest progress of chitin nanofibers in environmental and medical applications is also discussed. Finally, the potential challenges and tailored solutions of chitin nanofibers are further proposed, covering raw material, structure, function, manufacturing, policies, etc.

Present status and application prospects of green chitin nanowhiskers: A comprehensive review

Petrochemical resources are non-renewable, which has impeded the development of synthetic polymers. The poor degradability of synthetic polymers poses substantial environmental pressure. Additionally, the high cost of synthetic biopolymers with excellent degradation performance limits their widespread application. Thus, it is crucial to seek green, sustainable, low-cost polymers as alternatives to petrochemical-based synthetic polymers and synthetic biopolymers. Chitin is a natural and renewable biopolymer discovered in crustacean shells, insect exoskeletons, and fungal cell walls. Chitin chains consist of crystalline and amorphous regions. Note that various treatments can be employed to remove the amorphous region, enhancing the crystallinity of chitin. Chitin nanowhiskers are a high crystallinity nanoscale chitin product with a high aspect ratio, a large surface area, adjustable surface morphology, and biocompatibility. They discover widespread applications in biomedicine, environmental treatment, food packaging, and biomaterials. Various methods can be utilized for preparing chitin nanowhiskers, including chemical, ionic liquids, deacetylation, and mechanical methods. However, developing an environmentally friendly preparation process remains a big challenge for expanding their applications in different materials and large-scale production. This article comprehensively analyzes chitin nanowhiskers' preparation strategies and their drawbacks. It also highlights the extensive application in different materials and various fields, besides the potential for commercial application.

Gradient heating activated ammonium persulfate oxidation for efficient preparation of high-quality chitin nanofibers

APS is a cheap and eco-friendly oxidant which enables one-step extraction of nanochitin (NCh) from fishery wastes. However, it is challenging to improve the preparation efficiency and NCh quality simultaneously, owing to the uneven or uncontrollable oxidation. Herein, we propose a simple and controllable way to isolate chitin nanofibers (ChNFs) from squid pen by gradient heating activated (GHA)- ammonium persulfate (APS) oxidation. Compared to the isothermal activated (ITA)-APS oxidation, our strategy reduced the mass ratio of squid pen to APS from 1:45 to 1:6 and reaction time from 15 h to 8 h. Meanwhile, the as-prepared ChNFs exhibited high yield (91.5 %), light transmittance (98 % at 500 nm), crystallinity index (96.9 %), and carboxyl content (1.53 mmol/g). GHA-APS oxidation involved multiple continuous heating and isothermal stages. The former stimulates a moderate activation of APS and enhances the oxidation rate, while the latter provides a duration for surface chemistry. This non-isothermal heating facilitates the continuous decomposition of APS at a relatively high and consistent rate, thereby enhances its oxidation efficiency. Furthermore, green assessments indicate this method is simple, time-saving, eco-friendly and cost-effective. Overall, this work introduces a novel perspective for the industrial extraction of high-efficiency and high-quality nanomaterials.

Designing for Degradation: Transient Devices Enabled by (Nano)Cellulose

Transient technology involves materials and devices that undergo controlled degradation after a reliable operation period. This groundbreaking strategy offers significant advantages over conventional devices based on non-renewable materials by limiting environmental exposure to potentially hazardous components after disposal, and by increasing material circularity. As the most abundant naturally occurring polymer on Earth, cellulose is an attractive material for this purpose. Besides, (nano)celluloses are inherently biodegradable and have competitive mechanical, optical, thermal, and ionic conductivity properties that can be exploited to develop sustainable devices and avoid the end-of-life issues associated with conventional systems. Despite its potential, few efforts have been made to review current advances in cellulose-based transient technology. Therefore, this review catalogs the state-of-the-art developments in transient devices enabled by cellulosic materials. To provide a wide perspective, the various degradation mechanisms involved in cellulosic transient devices are introduced. The advanced capabilities of transient cellulosic systems in sensing, photonics, energy storage, electronics, and biomedicine are also highlighted. Current bottlenecks toward successful implementation are discussed, with material circularity and environmental impact metrics at the center. It is believed that this review will serve as a valuable resource for the proliferation of cellulose-based transient technology and its implementation into fully integrated, circular, and environmentally sustainable devices.

Advances in extraction, utilization, and development of chitin/chitosan and its derivatives from shrimp shell waste

Shrimp consumption is in great demand among the seafood used globally. However, this expansion has resulted in the substantial generation and disposal of shrimp shell waste. Through literature search, it has been observed that since 2020, global scholars have shown unprecedented interest in shrimp shell waste and its chitin/chitosan. However, these new insights lack corresponding and comprehensive summarization and analysis. Therefore, this article provides a detailed review of the extraction methods, applications, and the latest research developments on chitin/chitosan from shrimp shells, including micro-nano derivatives, from 2020 to the present. The results indicate that chemical extraction remains the primary technique for the extraction and preparation of chitin/chitosan from shrimp shells. With further refinement and development, adjusting parameters in the chemical extraction process or employing auxiliary techniques such as microwave and radiation enable the customization of target products with different characteristics (e.g., deacetylation degree, molecular weight, and degree of acetylation) according to specific needs. Additionally, in pursuit of environmentally friendly, efficient, and gentle extraction processes, recent research has shifted toward microbial fermentation and green solvent methods for chitin/chitosan extraction. Beyond the traditional antibacterial, film-forming, and encapsulation functionalities, research into the applications of chitosan in biomedical, food processing, new materials, water treatment, and adsorption fields is gradually deepening. Chitin/chitosan derivatives and their modified products have also been a focal point of research in recent years. However, with the rapid expansion, the future development of chitin/chitosan and its derivatives still faces challenges related to the unclear mechanism of action and the complexities associated with industrial scale-up.

Lightweight, Strong, and Transparent Wood Films Produced by Capillary Driven Self-Densification

Wood delignification and densification enable the production of high strength and/or transparent wood materials with exceptional properties. However, processing needs to be more sustainable and besides the chemical delignification treatments, energy intense hot-pressing calls for alternative approaches. Here, this study shows that additional softening of delignified wood via a mild swelling process using an ionic liquid-water mixture enables the densification of tube-line wood cells into layer-by-layer sheet structures without hot-pressing. The natural capillary force induces self-densification in a simple drying process resulting in a transparent wood film. The as-prepared films with ≈150 µm thickness possess an optical transmittance ≈70%, while maintaining optical haze >95%. Due to the densely packed sheet structure with a large interfacial area, the reassembled wood film is fivefold stronger and stiffer than the delignified wood in fiber direction. Owing to a low density, the specific tensile strength and elastic modulus are as high as 282 MPa cm3 g-1 and 31 GPa cm3 g-1. A facile and highly energy efficient wood nanotechnology approach are demonstrated toward more sustainable materials and processes by directly converting delignified wood into transparent wood omitting polymeric matrix infiltration or mechanical pressing.

Biomass-derived polymer as a flexible "zincophilic-hydrophobic" solid electrolyte interphase layer to enable practical Zn metal anodes

Aqueous zinc ion batteries (AZIBs) face significant challenges stemming from Zn dendrite growth and water-contact attack, primarily due to the lack of a well-designed solid electrolyte interphase (SEI) to safeguard the Zn anode. Herein, we report a bio-mass derived polymer of chitin on Zn anode (Zn@chitin) as a novel and robust artificial SEI layer to boost the Zn anode rechargeability. The polymeric chitin SEI layer features both zincophilic and hydrophobic characteristics to target the suppressed dendritic Zn formation as well as the water-induced side reactions, thus harvesting a dendrite-free and corrosion-resistant Zn anode. More importantly, this polymeric interphase layer is strong and flexible accommodating the volume changes during repeated cycling. Based on these benefits, the Zn@chitin anode demonstrates prolonged cycling performance surpassing 1300 h under an ultra-large current density of 20 mA cm-2, and a long cycle life of 680 h with a record-high zinc utilization rate of 80 %. Besides, the assembled Zn@chitin/V2O5 full batteries reveal excellent capacity retention and rate performance under practical conditions, proving the reliability of our proposed strategy for industrial AZIBs. Our research offers valuable insights for constructing high-performance AZIBs, and simultaneously realizes the high-efficient use of cheap biomass from a "waste-to-wealth" concept.

Polysaccharide Nanocrystals-Based Chiral Nematic Structures: From Self-Assembly Mechanisms, Regulation, to Applications

Chiral architectures, one of the key structural features of natural systems ranging from the nanoscale to macroscale, are an infinite source of inspiration for functional materials. Researchers have been, and still are, strongly pursuing the goal of constructing such structures with renewable and sustainable building blocks via simple and efficient strategies. With the merits of high sustainability, renewability, and the ability to self-assemble into chiral nematic structures in aqueous suspensions that can be preserved in the solid state, polysaccharide nanocrystals (PNs) including cellulose nanocrystals (CNCs) and chitin nanocrystals (ChNCs) offer opportunities to reach the target. We herein provide a comprehensive review that focuses on the development of CNCs and ChNCs for the use in advanced functional materials. First, the introduction of CNCs and ChNCs, and cellulose- and chitin-formed chiral nematic organizations in the natural world, are given. Then, the self-assembly process of such PNs and the factors influencing this process are comprehensively discussed. After that, we showcased the emerging applications of the self-assembled chiral nematic structures of CNCs and ChNCs. Finally, this review concludes with perspectives on the challenges and opportunities in this field.

Preparation of zwitterionically charged chitin nanofibers through one step chemical modification and their application for antireflective coatings

Chitin nanofibers are widely used in many fields because of their biocompatibility, renewability and excellent mechanical properties. Herein, zwitterionically charged chitin nanofibers (ZC-ChNFs) were prepared from chitin via one step chemical modification (oxalic acid pretreatment) and subsequent ultrasound treatment. Effects of pretreatment time on size of the ZC-ChNFs and pH of ZC-ChNF suspensions on the thickness, porosity, refractive index and antireflective capacity of ZC-ChNF coatings were investigated. It was found that, by adjusting pH of the ZC-ChNF suspension, porosity and refractive index of the ZC-ChNF coatings could be controlled. The ZC-ChNF coatings fabricated with smaller ZC-ChNFs had higher antireflective performance and the transmittance gain of a glass with a ZC-ChNF coating was about 3.5 % at a wavelength of 550 nm compared to the bare glass. The results of this work provide a promising pathway to fabricate antireflective coating with ZC-ChNFs just by controlling the pH of ZC-ChNF suspensions.

Chitin nanocrystals-stabilized emulsion as template for fabricating injectable suspension containing polylactide hollow microspheres

One of the promising applications of rod-like chitin nanocrystals (ChNCs) is the use as particle emulsifier to develop Pickering emulsions. We reported a ChNC-stabilized oil-in-water emulsion system, and developed a Pickering emulsion-templated method to prepare polylactide (PLA) hollow microspheres here. The results showed that both non-modified ChNCs and acetylated ChNCs could well emulsify the dichloromethane (DCM) solution of PLA-in-aqueous mannitol solution systems, forming very stable emulsions. At the same oil-to-water ratios and ChNC loadings, the emulsion stability was improved with increasing acetylation levels of ChNCs, accompanied by reduced size of droplets. Through the solvent evaporation, the PLA hollow microspheres were templated successfully, and the surface structure was also strongly dependent on the acetylation level of ChNCs. At a low level of acetylation, the single-hole or multi-hole surface structure formed, which was attributed to the out-diffusion of DCM caused by the solvent extraction and evaporation. These surface defects decreased with increased acetylation levels of ChNCs. Moreover, the aqueous suspension with as-obtained PLA microspheres revealed shear-thinning property and good biocompatibility, thereby had promising application as injectable fillers. This work can provide useful information around tuning surface structures of the Pickering emulsion-templated polymer hollow microspheres by regulating acetylation level of ChNCs.

A Universal Biomacromolecule-Enabled Assembly Strategy for Constructing Multifunctional Aerogels with 90% Inorganic Mass Loading from Inert Nano-Building Blocks

Inert inorganic nano-building blocks, such as carbon nanotubes (CNTs) and boron nitride (BN) nanosheets, possess excellent physicochemical properties. However, it remains challenging to build aerogels with these inert nanomaterials unless they are chemically modified or compounded with petrochemical polymers, which affects their intrinsic properties and is usually not environmentally friendly. Here, a universal biomacromolecule-enabled assembly strategy is proposed to construct aerogels with 90 wt% ultrahigh inorganic loading. The super-high inorganic content is beneficial for exploiting the inherent properties of inert nanomaterials in multifunctional applications. Taking chitosan-CNTs aerogel as a proof-of-concept demonstration, it delivers sensitive pressure response as a pressure sensor, an ultrahigh sunlight absorption (94.5%) raising temperature under light (from 25 to 71 °C within 1 min) for clean-up of crude oil spills, and superior electromagnetic interference shielding performance of up to 68.9 dB. This strategy paves the way for the multifunctional application of inert nanomaterials by constructing aerogels with ultrahigh inorganic loading.

Biofabrication with microbial cellulose: from bioadaptive designs to living materials

Nanocellulose is not only a renewable material but also brings functions that are opening new technological opportunities. Here we discuss a special subset of this material, in its fibrillated form, which is produced by aerobic microorganisms, namely, bacterial nanocellulose (BNC). BNC offers distinct advantages over plant-derived counterparts, including high purity and high degree of polymerization as well as crystallinity, strength, and water-holding capacity, among others. More remarkably, beyond classical fermentative protocols, it is possible to grow BNC on non-planar interfaces, opening new possibilities in the assembly of advanced bottom-up structures. In this review, we discuss the recent advances in the area of BNC-based biofabrication of three-dimensional (3D) designs by following solid- and soft-material templating. These methods are shown as suitable platforms to achieve bioadaptive constructs comprising highly interlocked biofilms that can be tailored with precise control over nanoscale morphological features. BNC-based biofabrication opens applications that are not possible by using traditional manufacturing routes, including direct ink writing of hydrogels. This review emphasizes the critical contributions of microbiology, colloid and surface science, as well as additive manufacturing in achieving bioadaptive designs from living matter. The future impact of BNC biofabrication is expected to take advantage of material and energy integration, residue utilization, circularity and social latitudes. Leveraging existing infrastructure, the scaleup of biofabrication routes will contribute to a new generation of advanced materials rooted in exciting synergies that combine biology, chemistry, engineering and material sciences.

A theory of hydrogel mechanics that couples swelling and external flow

Two aspects of hydrogel mechanics have been studied separately in the past. The first is the swelling and deswelling of gels in a quiescent solvent bath triggered by an environmental stimulus such as a change in temperature or pH, and the second is the solvent flow around and into a gel domain, driven by an external pressure gradient or moving boundary. The former neglects convection due to external flow, whereas the latter neglects solvent diffusion driven by a gradient in chemical potential. Motivated by engineering and biomedical applications where both aspects coexist and potentially interact with each other, this work presents a poroelasticity model that integrates these two aspects into a single framework, and demonstrates how the coupling between the two gives rise to novel physics in relatively simple one-dimensional and two-dimensional flows.

Electric field-modulated evaporative thin film deposition of bio-particles for piezoelectric applications

Bio-based functional materials can be used to replace or limit the use of synthetic materials sourced from unsustainable sources. However, the potential of such materials remains largely unexplored. In this study, we demonstrate the use of weak AC electric fields to deposit ultra-thin piezoelectric films from cellulose nanocrystals (CNC). This is the first time electric fields are used to realize <50 nm thick uniform bio-based piezoelectric films wherein the bioparticles exhibit unidirectional arrangement. Interestingly, we found that the use of weak AC electric fields of suitable frequencies completely mitigates the coffee ring effect (CRE), which results in defect-free uniform ultra-thin films. Additionally, the electric fields appear to help in realizing unidirectional alignment of particles in the films, which enhances their piezoelectric properties. The method was also tested for chitin nanocrystals (ChNC), which have a similar aspect ratio but bear opposite polarity surface charges, and the influence of the field on coffee ring formation and particle orientation in CNC thin film deposition was validated. The phenomena can be attributed to the constant spatio-temporal curvature of the evaporating liquid film, the transient state between the three-phase contact (TPC) line, the electric field-dependent contact angle, and the permanent and field-induced dipole moments. These factors lead to particle polarization and alignment. The films have an optimum electrical frequency of deposition at which they are continuous and uniformly thin, have unidirectional alignment of particles, and function as a single dipole.

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.

Crystalline nanoxylan from hot water extracted wood xylan at multi-length scale: Molecular assembly from nanocluster hydrocolloids to submicron spheroids

As a contribution to expand accessibility in the territory of bio-based nanomaterials, we demonstrate a novel material strategy to convert amorphous xylan preserved in wood biomass to hierarchical assemblies of crystalline nanoxylan on a multi-length scale. By reducing the end group in pressurized hot water extracted (PHWE) xylan to primary alcohol as a xylitol form with borohydride reduction, the endwise-peeling depolymerization is effectively impeded in the alkali-catalyzed hydrolytic cleavage of side substitutions in xylan. Nanoprecipitation by a gradual pH decrease resulted in a stable hydrocolloid dispersion in the form of worm-like nanoclusters assembled with primary crystallites, owing to the self-assembly of debranched xylan driven by strong intra- and inter-chain H-bonds. With evaporation-induced self-assembly, we can further construct the hydrocolloids as dry submicron spheroids of crystalline nanoxylan (CNX) with a high average elastic modulus of 47-83 GPa. Taking the advantage that the chain length and homogeneity of PHWE-xylan can be tailored, a structure-performance correlation was established between the structural order in CNX and the phosphorescent emission of this crystalline biopolymer. Rigid clusterization and high crystallinity that are constructed by strong intra- and inter-molecule interactions within the nanoxylan effectively restrict the molecular motion, thereby promoting the emission of ultralong organic phosphorescence.

Activating Adsorption Sites of Waste Crayfish Shells via Chemical Decalcification for Efficient Capturing of Nanoplastics

The property of being stubborn and degradation resistant makes nanoplastic (NP) pollution a long-standing remaining challenge. Here, we apply a designed top-down strategy to leverage the natural hierarchical structure of waste crayfish shells with exposed functional groups for efficient NP capture. The crayfish shell-based organic skeleton with improved flexibility, strength (14.37 to 60.13 MPa), and toughness (24.61 to 278.98 MJ m-3) was prepared by purposefully removing the inorganic components of crayfish shells through a simple two-step acid-alkali treatment. Due to the activated functional groups (e.g., -NH2, -CONH-, and -OH) and ordered architectures with macropores and nanofibers, this porous crayfish shell exhibited effective removal capability of NPs (72.92 mg g-1) by physical interception and hydrogen bond/electrostatic interactions. Moreover, the sustainability and stability of this porous crayfish shell were demonstrated by the maintained high-capture performance after five cycles. Finally, we provided a postprocessing approach that could convert both porous crayfish shell and NPs into a tough flat sheet. Thus, our feasible top-down engineering strategy combined with promising posttreatment is a powerful contender for a recycling approach with broad application scenarios and clear economic advantages for simultaneously addressing both waste biomass and NP pollutants.

Nano-enabled smart and functional materials toward human well-being and sustainable developments

Fabrication and operation on increasingly smaller dimensions have been highly integrated with the development of smart and functional materials, which are key to many technological innovations to meet economic and societal needs. Along with researchers worldwide, the Waterloo Institute for Nanotechnology (WIN) has long realized the synergetic interplays between nanotechnology and functional materials and designated 'Smart & Functional Materials' as one of its four major research themes. Thus far, WIN researchers have utilized the properties of smart polymers, nanoparticles, and nanocomposites to develop active materials, membranes, films, adhesives, coatings, and devices with novel and improved properties and capabilities. In this review article, we aim to highlight some of the recent developments on the subject, including our own research and key research literature, in the context of the UN Sustainability development goals.

Chitin Nanofibers Enable the Colloidal Dispersion of Carbon Nanomaterials in Aqueous Phase and Hybrid Material Coassembly

Chitin nanofibrils (ChNF) sourced from discarded marine biomass are shown as effective stabilizers of carbon nanomaterials in aqueous media. Such stabilization is evaluated for carbon nanotubes (CNT) considering spatial and temporal perspectives by using experimental (small-angle X-ray scattering, among others) and theoretical (atomistic simulation) approaches. We reveal that the coassembly of ChNF and CNT is governed by hydrophobic interactions, while electrostatic repulsion drives the colloidal stabilization of the hybrid ChNF/CNT system. Related effects are found to be transferable to multiwalled carbon nanotubes and graphene nanosheets. The observations explain the functionality of hybrid membranes obtained by aqueous phase processing, which benefit from an excellent areal mass distribution (correlated to piezoresistivity), also contributing to high electromechanical performance. The water resistance and flexibility of the ChNF/CNT membranes (along with its tensile strength at break of 190 MPa, conductivity of up to 426 S/cm, and piezoresistivity and light absorption properties) are conveniently combined in a device demonstration, a sunlight water evaporator. The latter is shown to present a high evaporation rate (as high as 1.425 kg water m-2 h-1 under one sun illumination) and recyclability.

Effect of hydrophobic modification of chitin nanocrystals on role as anti-nucleator in the crystallization of poly(ε-caprolactone)/polylactide blend

Biodegradable polymer blends filled with rod-like polysaccharide nanocrystals have attracted much attention because each component in this type of ternary composites is biodegradable, and the final properties are more easily tailored comparing to those of binary composites. In this work, chitin nanocrystals (ChNCs) were used as nanofiller for the biodegradable poly(ε-caprolactone) (PCL)/polylactide (PLA) immiscible blend to prepare ternary composites for a crystallization study. The results revealed that the crystallization behavior of PCL/PLA blend matrices strongly depended on the surface properties of ChNCs. Non-modified ChNCs and modified ChNCs played completely different roles during crystallization of the ternary systems: the former was inert filler, while the latter acted as anti-nucleator to the PCL phase. This alteration was resulted from the improved ChNC-PCL affinity after modification of ChNCs, which was due to the 'interfacial dilution effect' and the preferential dispersion of ChNCs. This work presents a unique perspective on the nucleation role of ChNCs in the crystallization of immiscible PCL/PLA blends, and opens up a new application scenario for ChNCs as anti-nucleator.