Fabrication and characterisation of α-chitin nanofibers and highly transparent chitin films by pulsed ultrasonication

Nanofibrous composite from chitosan-casein polyelectrolyte complex for rapid hemostasis in rat models in vivo

Bleeding causes ∼5.8 million deaths globally; half of the patients die if rapid hemostasis is not achieved. Here, we report a chitosan-casein (CC)-based nanofibrous polyelectrolyte complex (PEC) that could clot blood within 10 s in the rat femoral artery model in vivo. The nanofiber formation by self-assembly was also optimized for process parameters (concentration, mixing ratio, pH, and ultrasonication). Results showed that increasing the concentration of chitosan from 10 % to 90 % in the formulation increased the productivity (r = 0.99) of PECs but led to increased blood clotting time (r = 0.90) due to an increase in zeta potential (r = 0.98), fiber diameter (r = 0.93), and decreased surface porosity (r = -0.99), absorption capacity (r = -0.99). The pH also influenced the zeta potential of PEC, with an optimized pH of 8.0 ± 0.1 yielding clear nanofibers. Sonication improved the segregation of nanofibers by promoting water removal. The optimized PECs containing chitosan and casein in the ratio of 30:70 (CC30) at a pH of 8.0 and dehydration under sonication could clot the blood within 9 ± 2 s in vitro and 9 ± 2 s in rat femoral artery puncture model. The CC30 formulation did not cause any irritation or corrosion on rat skin. Histopathology and immunohistochemistry of various organs showed that CC30 was biocompatible and non-immunogenic under in vivo conditions.

Applications of high-intensity ultrasound on shrimp: Potential, constraints, and prospects in the extraction and retrieval of bioactive compounds, safety, and quality

The global shrimp market holds substantial prominence within the food industry, registering a significant USD 24.7 billion in worldwide exportation in 2020. However, the production of a safe and high-quality product requires consideration of various factors, including the potential for allergenic reactions, occurrences of foodborne outbreaks, and risks of spoilage. Additionally, the exploration of the recovery of bioactive compounds (e.g., astaxanthin [AX], polyunsaturated fatty acids, and polysaccharides) from shrimp waste demands focused attention. Within this framework, this review seeks to comprehend and assess the utilization of high-intensity ultrasound (HIUS), both as a standalone method and combined with other technologies, within the shrimp industry. The objective is to evaluate its applications, limitations, and prospects, with a specific emphasis on delineating the impact of sonication parameters (e.g., power, time, and temperature) on various applications. This includes an examination of undesirable effects and identifying areas of interest for current and prospective research. HIUS has demonstrated promise in enhancing the extraction of bioactive compounds, such as AX, lipids, and chitin, while concurrently addressing concerns such as allergen reduction (e.g., tropomyosin), inactivation of pathogens (e.g., Vibrio parahaemolyticus), and quality improvement, manifesting in reduced melanosis scores and improved peelability. Nonetheless, potential impediments, particularly related to oxidation processes, especially those associated with lipids, pose a hindrance to its widespread implementation, potentially impacting texture properties. Consequently, further optimization studies remain imperative. Moreover, novel applications of sonication in shrimp processing, including brining, thawing, and drying, represent a promising avenue for expanding the utilization of HIUS in the shrimp industry.

Review on emerging trends and challenges in the modification of xanthan gum for various applications

This review explores the realm of structural modifications and broad spectrum of their potential applications, with a special focus on the synthesis of xanthan gum derivatives through graft copolymerization methods. It delves into the creation of these derivatives by attaching functional groups (-OH and -COOH) to xanthan gum, utilizing a variety of initiators for grafting, and examining their diverse applications, especially in the areas of food packaging, pharmaceuticals, wastewater treatment, and antimicrobial activities. Xanthan gum is a biocompatible, biodegradable, less toxic, bioactive, and cost-effective natural polymer derived from Xanthomonas species. The native properties of xanthan gum can be improved by cross-linking, grafting, curing, blending, and various modification techniques. Grafted xanthan gum has excellent biodegradability, metal binding, dye adsorption, immunological properties, and wound healing ability. Owing to its remarkable properties, such as biocompatibility and its ability to form gels resembling the extracellular matrix of tissues, modified xanthan gum finds extensive utility across biomedicine, engineering, and the food industry. Furthermore, the review also covers various modified derivatives of xanthan gum that exhibit excellent biodegradability, metal binding, dye adsorption, immunological properties, and wound healing abilities. These applications could serve as important resources for a wide range of industries in future product development.

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.

Chitin nanofibers prepared by enzymatic hydrolysis: Characterization and application for Pickering emulsions

Chitin nanofibers (ChNFs) have a wide range of applications in numerous fields owing to their exceptional material properties and biological functionality. This research focused on producing ChNFs with diameters of 20-70 nm using chitinase and ultrasound from crayfish shells. The impact of enzymatic duration on ChNF yield and performance was investigated. Results revealed ChNFs forming a high aspect ratio network structure. Chitinase hydrolysis enhanced ChNF dispersion and yield while improving crystallinity and thermal stability without significantly altering their chemical structure. Enzymatically modified ChNF suspensions also exhibited stable rheological properties. Moreover, ChNFs showed good emulsification and emulsion stability in Pickering emulsion. The mechanism may be the effective adsorption of ChNFs at the oil-water interface, and the formation of a ChNF network in the continuous phase that prevents droplet coalescence. This study highlights that the potential of chitinase and ultrasound for the production of ChNFs and the utilization of crayfish shell waste.

Fabrication of chitin-glucan nanofibers: Insights into mushroom pretreatment and subsequent acidic deep eutectic solvent-based esterification

Mushrooms contain chitin-glucan complex (CGC), a natural copolymer of chitin and glucan, and nanofibrillation enhances its applicability. Here, a novel method was used to fabricate chitin-glucan nanofibers (CGNFs) from white button mushrooms. The first stage was to pretreat the raw mushroom using hot water and alkali to remove water-soluble glucans and alkali-soluble proteins, respectively, producing a CGC amenable to nanofibrillation. The second stage was nanofibrillation via esterification using acidic deep eutectic solvents (DESs) and subsequent ultrasonication. Five choline chloride-based DESs containing mono- or dicarboxylic acid were tested for the CGC esterification. DESs with strong dicarboxylic acids expedited nanofibrillation by homogeneously dispersing the solid CGC, swelling CGC fibrils, and facilitating acidity-dependent esterification leading to steric and electrostatic repulsions. One CGNF, namely CGNF_CCMnA, was characterized: it contained chitin and glucan at an approximate ratio of 8:2 and exhibited desirable properties as nanomaterials, including small diameter (11 nm) and high colloidal (zeta potential < -30 mV above pH 5.8) and thermal stability (Tm, 315 °C). CGNF_CCMnA was tested for the adsorption to methylene blue, revealing a maximum adsorption capacity of 82.58 mg/g. The proposed approach is an efficient and readily applicable method to fabricate various mushroom-derived safe CGNFs and to produce related nanomaterials.

Chitin nanocrystals as natural gel modifier for yielding stronger acid-induced soy protein isolate gel

This study aimed to enhance the rheological properties and thermal stability of acid-induced soy protein isolate (SPI) gels by incorporating chitin nanocrystals (ChNCs) and proposing a gelation mechanism. SPI gels exhibited pseudo-plastic behavior. Increasing ChNCs concentration from 0.00 % to 1.00 % improved G' values, recovery rate, and initial degradation temperature: from 75.6 Pa to 1024.3 Pa, 80.27 % to 85.47 %, and 261.5 °C to 275.8 °C, respectively. FTIR analysis confirmed electrostatic and hydrogen bonding interactions between SPI and ChNCs. Adding 1.00 % ChNCs reduced α-helix content from 19.7 % to 12.1 % while increasing β-sheet content from 46.5 % to 52.6 %. This led to protein unfolding, exposure of Trp residues, and orderly aggregation, forming a dense cross-linked gel network. Gel particle size increased from 185.5 nm (no ChNCs) to 504.4 nm (1.00 % ChNCs), with reduced surface charges. Hydrophobic and electrostatic interactions were key forces stabilizing SPI-ChNCs gels. These findings offer a practical approach to enhancing traditional acid-induced protein gel-based functional foods using naturally sourced chitin nanocrystals.

Omnidirectional antireflective coatings prepared with chitin nanofibers via layer-by-layer self-assembly

Antireflective coatings play an important role in various optical devices. Herein, we developed omnidirectional antireflective coatings fabricated with charged chitin nanofibers (ChNFs) through layer-by-layer (LbL) self-assembly technology. The charged ChNFs were prepared from chitin with modifications of esterification (negatively charged) and esterification followed partial deacetylation (positively charged), respectively, through ultrasonic treatment. The effects of concentration of the ChNF suspensions and number of bilayers on thickness, refractive index and antireflective capacity of the ChNF coatings were investigated. Refractive index of the ChNF coatings can be manipulated by changing concentration of the ChNF suspensions. Thickness of the ChNF coatings depends on number of bilayers and concentration of the ChNF suspensions. The ChNF coating on a glass substrate with 5 bilayers fabricated using the suspensions with concentration 0.1% had a refractive index of 1.36 and yielded 4% gain in transmittance compared to the glass at the wavelength of 550 nm. This work demonstrates that charged ChNFs are promising building blocks to fabricate antireflective coatings on large size substrates with high efficiency and low cost through LbL self-assembly.

Nano-chitin reinforced agarose hydrogels: Effects of nano-chitin addition and acidic gas-phase coagulation

Hydrogels based on natural polymers such as agarose usually show low applicability due to their weak mechanical properties. In this work, we developed a dual cross-linked agarose hydrogel by adding different amounts of TEMPO-oxidized nano-chitin (0-0.2 %) to agarose hydrogel matrices and then physically cross-linked under acidic gas-phase coagulation. The prepared hydrogels were characterized by FTIR, XRD, TGA, and SEM. The effects of nano-chitin addition and acidic gas-phase coagulation on the properties of agarose hydrogels, such as gel strength, swelling degree, rheological properties, and methylene blue (MB) adsorption capacity, were also studied. Structural characterizations confirmed that nano-chitin was successfully introduced into agarose hydrogels. The gel strength, storage modulus, and MB adsorption capacity of agarose hydrogels gradually increased with the increasing nano-chitin addition, whereas the swelling degree decreased. After acidic gas-phase coagulation, agarose/nano-chitin nanocomposite hydrogels exhibited improved gel strength and storage modulus, while the swelling degree and MB adsorption capacity were slightly reduced. The combination of oxidized nano-chitin and acidic gas-phase coagulation is expected to be an effective way to improve the properties of natural polymer hydrogels.

Chitin nanofiber-coated biodegradable polymer microparticles via one-pot aqueous process

Tailoring the surface of biodegradable microparticles is important for various applications in the fields of cosmetics, biotechnology, and drug delivery. Chitin nanofibers (ChNFs) are one of the promising materials for surface tailoring owing to its functionality, such as biocompatibility and antibiotic properties. Here, we show biodegradable polymer microparticles densely coated with ChNFs. Cellulose acetate (CA) was used as the core material in this study, and ChNF coating was successfully carried out via a one-pot aqueous process. The average particle size of the ChNF-coated CA microparticles was approximately 6 μm, and the coating procedure had little effect on the size or shape of the original CA microparticles. The ChNF-coated CA microparticles comprised 0.2-0.4 wt% of the thin surface ChNF layers. Owing to the surface cationic ChNFs, the ζ-potential value of the ChNF-coated microparticles was +27.4 mV. The surface ChNF layer efficiently adsorbed anionic dye molecules, and repeatable adsorption/desorption behavior was exhibited owing to the coating stability of the surface ChNFs. The ChNF coating in this study was a facile aqueous process and was applicable to CA-based materials of various sizes and shapes. This versatility will open new possibilities for future biodegradable polymer materials that satisfy the increasing demand for sustainable development.

Carbon black and chitin nanofibers for green tyres: Preparation and property evaluation

This research highlights the synergistic use of carbon black (CB) and chitin nanofibers (CHNFs) for developing green tyres for the first time. The CHNFs (12-30 nm) were prepared from chitin powder with the help of steam explosion and mild oxalic acid hydrolysis. The CHNFs were uniformly dispersed in natural rubber (NR) latex, dried, and mixed with CB in a two-roll mill to form NR/CB/CHNF composites. The NR/CB/CHNF composite at 1 phr CHNF loading exhibited tensile and tear strengths that were about 47 and 160 % greater than the NR-Neat, respectively. The dynamic mechanical analysis showed that the loss tangent (tan δ) at 60 °C was 50 % lower for the NR/CB/CHNF 1.0 composite than for the NR/CB50 composite. The study succeeded in developing a new green tyre tread formulation that would be helpful for attaining sustainability and a circular economy.

Reusable and Biodegradable Separation Membranes Prepared from Common Mushrooms for the Removal of Oily and Particulate Contaminants from Water

Mushroom chitin membranes with controllable pore structures were fabricated through a simple process with naturally abundant Agaricus bisporus mushrooms. A freeze-thaw method was applied to alter the pore structures of the membranes, which consist of chitin fibril clusters within the glucan matrix. With tunable pore size and distribution, mushroom chitin membranes could effectively separate stable oil/water emulsions (dodecane, toluene, isooctane, and chili oil) with various chemical properties and concentrations and particle contaminants (carbon black and microfibers) from water. Chitin fibrils tightly pack with each other to form a dense membrane, leading to no permeation of contaminants or water. An increasing number of applied freeze-thaw cycles confers more tortuous pore structures throughout the mushroom chitin membranes, leading to higher flux while maintaining rejection performance. The 3D simulation constructed by the X-ray computed tomography and GeoDict software also demonstrated capturing a considerable amount of contaminants within the membranes' pores, which can be easily removed by water rinsing for further successive filtration. Furthermore, mushroom chitin membranes were almost completely biodegraded after approximately a month of being buried in the soil or kept in a lysozyme solution while possessing mechanical durability demonstrated by consistent filtration performance for repeated usage up to 15 cycles under ambient and external pressure. This research is a proof of concept that mushroom-derived chitin develops functional and biodegradable materials for environmental applications with scalability.

The Loss of Structural Integrity of 3D Chitin Scaffolds from Aplysina aerophoba Marine Demosponge after Treatment with LiOH

Aminopolysaccharide chitin is one of the main structural biopolymers in sponges that is responsible for the mechanical stability of their unique 3D-structured microfibrous and porous skeletons. Chitin in representatives of exclusively marine Verongiida demosponges exists in the form of biocomposite-based scaffolds chemically bounded with biominerals, lipids, proteins, and bromotyrosines. Treatment with alkalis remains one of the classical approaches to isolate pure chitin from the sponge skeleton. For the first time, we carried out extraction of multilayered, tube-like chitin from skeletons of cultivated Aplysina aerophoba demosponge using 1% LiOH solution at 65 °C following sonication. Surprisingly, this approach leads not only to the isolation of chitinous scaffolds but also to their dissolution and the formation of amorphous-like matter. Simultaneously, isofistularin-containing extracts have been obtained. Due to the absence of any changes between the chitin standard derived from arthropods and the sponge-derived chitin treated with LiOH under the same experimental conditions, we suggest that bromotyrosines in A. aerophoba sponge represent the target for lithium ion activity with respect to the formation of LiBr. This compound, however, is a well-recognized solubilizing reagent of diverse biopolymers including cellulose and chitosan. We propose a possible dissolution mechanism of this very special kind of sponge chitin.

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.

Biocompatible and biodegradable chitin-based hydrogels crosslinked by BDDE with excellent mechanical properties for effective prevention of postoperative peritoneal adhesion

Postoperative peritoneal adhesions are common complications caused by abdominal and pelvic surgery, which seriously impact the quality of life of patients and impose additional financial burdens. Using of biomedical materials as physical barriers to completely isolate the traumatic organ and injured tissue is an optimal strategy for preventing postoperative adhesions. However, the limited efficacy and difficulties in the complete degradation or integration of biomedical materials with living tissues restrict the application of these materials. In this study, novel chitin-based crosslinked hydrogels with appropriate mechanical properties and flexibilities were developed using a facile and green strategy. The developed hydrogels simultaneously exhibited excellent biocompatibilities and resistance to nonspecific protein adsorption and NIH/3T3 fibroblast adhesion. Furthermore, these hydrogels were biodegradable and could be completely integrated into the native extracellular matrix. The chitin-based crosslinked hydrogels also effectively inhibited postoperative peritoneal adhesions in rat models of adhesion and recurrence. Therefore, these novel chitin-based crosslinked hydrogels are excellent candidate physical barriers for the efficient prevention of postoperative peritoneal adhesions and provide a new anti-adhesion strategy for biomedical applications.

Nanochitin: Chemistry, Structure, Assembly, and Applications

Chitin, a fascinating biopolymer found in living organisms, fulfills current demands of availability, sustainability, biocompatibility, biodegradability, functionality, and renewability. A feature of chitin is its ability to structure into hierarchical assemblies, spanning the nano- and macroscales, imparting toughness and resistance (chemical, biological, among others) to multicomponent materials as well as adding adaptability, tunability, and versatility. Retaining the inherent structural characteristics of chitin and its colloidal features in dispersed media has been central to its use, considering it as a building block for the construction of emerging materials. Top-down chitin designs have been reported and differentiate from the traditional molecular-level, bottom-up synthesis and assembly for material development. Such topics are the focus of this Review, which also covers the origins and biological characteristics of chitin and their influence on the morphological and physical-chemical properties. We discuss recent achievements in the isolation, deconstruction, and fractionation of chitin nanostructures of varying axial aspects (nanofibrils and nanorods) along with methods for their modification and assembly into functional materials. We highlight the role of nanochitin in its native architecture and as a component of materials subjected to multiscale interactions, leading to highly dynamic and functional structures. We introduce the most recent advances in the applications of nanochitin-derived materials and industrialization efforts, following green manufacturing principles. Finally, we offer a critical perspective about the adoption of nanochitin in the context of advanced, sustainable materials.

Ultrasound-assisted fabrication of biopolymer materials: A review

There is an urgent need to develop technologies that can physically manipulate the structure of biocompatible and green polymer materials in order to tune their performance in an efficient, repeatable, easy-to-operate, chemical-free, non-contact, and highly controllable manner. Ultrasound technology produces a cavitation effect that promotes the generation of free radicals, the fracture of chemical chain segments and a rapid change of morphology. The cavitation effects are accompanied by thermal, chemical, and biological effects that interact with the material being studied. With its high efficiency, cleanliness, and reusability applications, ultrasound has a vast range of opportunity within the field of natural polymer-based materials. This work expounds the basic principle of ultrasonic cavitation and analyzes the influence that ultrasonic strength, temperature, frequency and induced liquid surface tension on the physical and chemical properties of biopolymer materials. The mechanism and the influence that ultrasonic modification has on materials is discussed, with highlighted details on the agglomeration, degradation, morphology, structure, and the mechanical properties of these novel materials from naturally derived polymers.

pH indicator films fabricated from soy protein isolate modified with chitin nanowhisker and Clitoria ternatea flower extract

Sensor films are finding wide range of applications. Different type of sensing films is fabricated for the identification of chemicals, ions, heavy metals, changes in the pH, etc. The present report is on the fabrication of pH sensitive films from completely natural sources-soy protein isolate, chitin nano whiskers and flower extract. The highly crystalline chitin nano whiskers (CNW) were extracted from prawn shell under neutral condition via steam explosion technique. Multifunctional Soy protein isolate (SPI) films were prepared by adding chitin nanowhisker and Clitoria ternatea flower extract and its effect on thermal, mechanical and moisture properties of SPI film was investigated. The isolated CNW presented a needle like morphology with a diameter of 10–50 nm and a crystallinity index of 99.67%. The extracted chitin nanowhisker was used to prepare biodegradable films with soy protein isolate immobilized with anthocyanin from Clitoria ternatea flower extract. The prepared Soy protein -chitin nanowhisker films was found to have a tensile strength of about 15.45 ± 0.97 MPa with 8% chitin nanowhisker addition. The addition of CTE was found to decrease the tensile strength of SPI-CNW film but was found to make the film pH sensitive. The developed indicator film showed visible color changes in acidic and basic medium and hence can be used to monitor the freshness of food materials.

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Thin films were fabricated from soy protein isolate, chitin and anthocyanin.

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Packaging films from fully greener and bio origin.

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pH sensing smart films.

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Easy to fabricate and handle.

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Superior mechanical properties and stability.

Preparation, Characterization and Gelation of a Fungal Nano Chitin Derived from Hericium erinaceus Residue

Nano chitin is a promising biocompatible material with wide applications. In this work, a fungal-derived nano chitin was prepared from Hericium erinaceus residue via mineral/protein purification and subsequent TEMPO-mediated oxidation. The structure, dispersity, and gelation ability of the prepared fungal nano chitin were studied. The results showed that the average length and width of the prepared fungal nano chitin were 336.6 nm and 6.4 nm, respectively, and the aspect ratio exceeded 50:1. The nano chitin retained the basic structure of chitin, while the crystallization index was improved. In addition, the dispersity of the nano chitin in aqueous media was evaluated by the effective diameter, and the polydispersion index was mainly affected by pH and ionic strength. Under acetic acid “gas phase coagulation”, the prepared nano chitin dispersions with mass concentrations of 0.2, 0.4, 0.6, and 0.8% were converted into gels by enhanced hydrogen bond crosslinking between nano chitins.

Chitin Nanocrystals: Environmentally Friendly Materials for the Development of Bioactive Films

Biobased nanomaterials have gained growing interest in recent years for the sustainable development of composite films and coatings, providing new opportunities and high-performance products. In particular, chitin and cellulose nanocrystals offer an attractive combination of properties, including a rod shape, dispersibility, outstanding surface properties, and mechanical and barrier properties, which make these nanomaterials excellent candidates for sustainable reinforcing materials. Until now, most of the research has been focused on cellulose nanomaterials; however, in the last few years, chitin nanocrystals (ChNCs) have gained more interest, especially for biomedical applications. Due to their biological properties, such as high biocompatibility, biodegradability, and antibacterial and antioxidant properties, as well as their superior adhesive properties and promotion of cell proliferation, chitin nanocrystals have emerged as valuable components of composite biomaterials and bioactive materials. This review attempts to provide an overview of the use of chitin nanocrystals for the development of bioactive composite films in biomedical and packaging systems.

Insight into morphological, physicochemical and spectroscopic properties of β-chitin nanocrystalline structures

We systematically investigated the effect of β-chitin (BCH) particle size on the preparation of nanocrystals/nanowhiskers (CWH) by acid hydrolysis. Regardless this variable, CWH aqueous suspension exhibited outstanding stability and the average degree of acetylation remained nearly constant after the acid treatment. In contrast, the morphology, dimensions, crystallinity, and molecular weight of CHW were significantly affect by the particle size. Although needle-like crystals have predominated, BCH particles sizes significantly affected the dimensions and asymmetry of CWH, as confirmed by the rheological and NMR relaxation (T₂) behaviors. According to different SSNMR approaches, the acid hydrolysis meaningless affected the local chain conformation, while the spatial freedom of BCH intersheets, rated upon the mobility of methyl segments, was taken as evidence of higher permeability of acid into small particle sizes. Thus, this study demonstrated the importance of standardizing the surface/bulk proportions of β-chitin aiming to predict and control the CWH morphology and related properties.

Mechanical properties of cellulose nanofibril papers and their bionanocomposites: A review

Cellulose nanofibril (CNF) paper has various applications due to its unique advantages. Herein, we present the intrinsic mechanical properties of CNF papers, along with the preparation and properties of nanoparticle-reinforced CNF composite papers. The literature on CNF papers reveals a strong correlation between the intrafibrillar network structure and the resulting mechanical properties. This correlation is found to hold for all primary factors affecting mechanical properties, indicating that the performance of CNF materials depends directly on and can be tailored by controlling the intrafibrillar network of the system. The parameters that influence the mechanical properties of CNF papers were critically reviewed. Moreover, the effect on the mechanical properties by adding nanofillers to CNF papers to produce multifunctional composite products was discussed. We concluded this article with future perspectives and possible developments in CNFs and their bionanocomposite papers.

Liquid and Solid Functional Bio-Based Coatings

The development of new bio-based coating materials to be applied on cellulosic and plastic based substrates, with improved performances compared to currently available products and at the same time with improved sustainable end of life options, is a challenge of our times. Enabling cellulose or bioplastics with proper functional coatings, based on biopolymer and functional materials deriving from agro-food waste streams, will improve their performance, allowing them to effectively replace fossil products in the personal care, tableware and food packaging sectors. To achieve these challenging objectives some molecules can be used in wet or solid coating formulations, e.g., cutin as a hydrophobic water- and grease-repellent coating, polysaccharides such as chitosan-chitin as an antimicrobial coating, and proteins as a gas barrier. This review collects the available knowledge on functional coatings with a focus on the raw materials used and methods of dispersion/application. It considers, in addition, the correlation with the desired final properties of the applied coatings, thus discussing their potential.

One-Step Preparation of Chitin Nanofiber Dispersion in Full pH Surroundings Using Recyclable Solid Oxalic Acid and Evaluation of Redispersed Performance

This study proposed an efficient and economical preparation pathway from purified chitin to nanofibers that can be dispersed in full pH surroundings. Recyclable oxalic acid was applied to prepare chitin nanofibers in a mild environment along with concurrent modifications of the carboxylic groups on the surface. Pretreatment with oxalic acid significantly improved the mechanical disintegration of chitin into nanofibers, the length of nanofibers reached ∼1100 nm, and the crystallinity and thermal stability of the chitin were basically unchanged with mild treatment. Oxalic acid can be reused many times with a high recovery of over 91%. Most importantly, the obtained nanofibers can be fabricated into films and hydrogels with certain mechanical properties, which can be redispersed into nanofibers using mild mechanical treatment. This method not only produces nanofibers in a green, reusable system but also provides a reference for the potential application of chitin nanofibers in commercial transportation and wide applicability.

Understanding the structural diversity of chitins as a versatile biomaterial

Chitin is one of the most abundant biopolymers, and it has adopted many different structural conformations using a combination of different natural processes like biopolymerization, crystallization and non-equilibrium self-assembly. This leads to a number of striking physical effects like complex light scattering and polarization as well as unique mechanical properties. In doing so, chitin uses a fine balance between the highly ordered chain conformations in the nanofibrils and random disordered structures. In this opinion piece, we discuss the structural hierarchy of chitin, its crystalline states and the natural biosynthesis processes to create such specific structures and diversity. Among the examples we explored, the unified question arises from the generation of completely different bioarchitectures like the Christmas tree-like nanostructures, gyroids or helicoidal geometries using similar dynamic non-equilibrium growth processes. Understanding the in vivo development of such structures from gene expressions, enzymatic activities as well as the chemical matrix employed in different stages of the biosynthesis will allow us to shift the material design paradigms. Certainly, the complexity of the biology requires a collaborative and multi-disciplinary research effort. For the future's advanced technologies, using chitin will ultimately drive many innovations and alternatives using biomimicry in materials science. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 1)'.

Quantification of energy input required for chitin nanocrystal aggregate size reduction through ultrasound

Nanoparticles have been claimed to contribute efficiently to e.g. the mechanical strength of composite materials when present as individual particles. However, these particles tend to aggregate. In this paper we prepare nanocrystals from chitin, a product with high potential added value for application in bio-based materials, and investigate the effect of ultrasound on de-aggregation. Chitin nanocrystals with a length ~ 200 nm and a diameter ~ 15 nm, were obtained via acid hydrolysis of crude chitin powder. Freeze drying resulted in severe aggregation and after redispersion sizes up to ~ 200 µm were found. Ultrasound treatment was applied and break up behaviour was investigated using static light scattering, dynamic light scattering, and laser diffraction. Our results suggest that the cumulative energy input was the dominant factor for chitin nanocrystal aggregate breakup. When a critical energy barrier of ~ 100 kJ/g chitin nanocrystals was exceeded, the chitin nanocrystal aggregates broke down to nanometre range. The break up was mostly a result of fragmentation: the aggregation energy of chitin nanocrystal aggregates was quantified to be ~ 370 kJ/g chitin nanocrystals and we hypothesize that mainly van der Waals interactions and hydrogen bonds are responsible for aggregation.

Optimum Preparation Conditions for Highly Individualized Chitin Nanofibers Using Ultrasonic Generator

α-Chitin derived from crab shells was treated with 30% sodium hydroxide to prepare partially deacetylated chitin with a deacetylation degree of 36%. Partially deacetylated chitin nanofibers were prepared by applying weak ultrasonic energy generated by a domestic ultrasonic cleaner. The deacetylated chitin was easily disintegrated into nanofibers with the aid of electrostatic repulsion and osmotic pressure effect of amino cations on the chitin surfaces. The nanofibers were characterized in terms of yield, morphology, crystallinity, viscosity, and dispersibility. After a series of characterizations, ultrasonication with 45 kHz frequency and 20 min treatment was found to be the optimum conditions for obtaining fine nanofibers with a high yield.

Potential natural polymer-based nanofibres for the development of facemasks in countering viral outbreaks

The global coronavirus disease 2019 (COVID-19) pandemic has rapidly increased the demand for facemasks as a measure to reduce the rapid spread of the pathogen. Throughout the pandemic, some countries such as Italy had a monthly demand of ca. 90 million facemasks. Domestic mask manufacturers are capable of manufacturing 8 million masks each week, although the demand was 40 million per week during March 2020. This dramatic increase has contributed to a spike in the generation of facemask waste. Facemasks are often manufactured with synthetic materials that are non-biodegradable, and their increased usage and improper disposal are raising environmental concerns. Consequently, there is a strong interest for developing biodegradable facemasks made with for example, renewable nanofibres. A range of natural polymer-based nanofibres has been studied for their potential to be used in air filter applications. This review article examines potential natural polymer-based nanofibres along with their filtration and antimicrobial capabilities for developing biodegradable facemask that will promote a cleaner production.

Biorenewable, transparent, and oxygen/moisture barrier nanocellulose/nanochitin-based coating on polypropylene for food packaging applications

Aluminum-coated polypropylene films are commonly used in food packaging because aluminum is a great gas barrier. However, recycling these films is not economically feasible. In addition, their end-of-life incineration generates harmful alumina-based particulate matter. In this study, coating layers with excellent gas-barrier properties are assembled on polypropylene films through layer-by-layer (LbL) deposition of biorenewable nanocellulose and nanochitin. The coating layers significantly reduce the transmission of oxygen and water vapors, two unfavorable gases for food packaging, through polypropylene films. The oxygen transmission rate of a 60 μm-thick, 20 LbL-coated polypropylene film decreases by approximately a hundredfold, from 1118 to 13.10 cc m^-2 day^-1 owing to the high crystallinity of nanocellulose and nanochitin. Its water vapor transmission rate slightly reduces from 2.43 to 2.13 g m^-2 day^-1. Furthermore, the coated film is highly transparent, unfavorable to bacterial adhesion and thermally recyclable, thus promising for advanced food packaging applications.

Valorization of food waste to produce intelligent nanofibrous β-chitin films

The efficient use of waste from food processing industry is one of the innovative approaches within sustainable development, because it can be transferred into added value products, which could improve economic, energetic and environmental sectors. In this context, the squid pen waste from seafood industry was used as raw material to obtain nanofibrous β-chitin films. In order to extend functionality of obtained films, elderberry extract obtained from biomass was added at different concentrations. The tensile strength of chitin-elderberry extract films was improved by 52%, elongation at break by 153% and water vapor barrier by 65%. The obtained material showed distinct color change when subjected to acidic or basic solutions. It was proven by CIELab color analysis that all color changes could be easily perceived visually. In addition, the obtained nanofibrous film was successfully used to monitor the freshness of Hake fish. Namely, when the film was introduced in a package that contained fresh fish, its color was efficiently changed within the time during the storage at 4 °C. The obtained results demonstrated that food processing waste could be efficiently valorized, and could give sustainable food package design as a spoilage indicator of high protein food.

Utilization of Marine Waste to Obtain β-Chitin Nanofibers and Films from Giant Humboldt Squid Dosidicus gigas

β-chitin was isolated from marine waste, giant Humboldt squid Dosidicus gigas, and further converted to nanofibers by use of a collider machine under acidic conditions (pH 3). The FTIR, TGA, and NMR analysis confirmed the efficient extraction of β-chitin. The SEM, TEM, and XRD characterization results verified that β-chitin crystalline structure were maintained after mechanical treatment. The mean particle size of β-chitin nanofibers was in the range between 10 and 15 nm, according to the TEM analysis. In addition, the β-chitin nanofibers were converted into films by the simple solvent-casting and drying process at 60 °C. The obtained films had high lightness, which was evidenced by the CIELAB color test. Moreover, the films showed the medium swelling degree (250-290%) in aqueous solutions of different pH and good mechanical resistance in the range between 4 and 17 MPa, depending on film thickness. The results obtained in this work show that marine waste can be efficiently converted to biomaterial by use of mild extractive conditions and simple mechanical treatment, offering great potential for the future development of sustainable multifunctional materials for various industrial applications such as food packaging, agriculture, and/or wound dressing.

Influence of esterification and ultrasound treatment on formation and properties of starch nanoparticles and their impact as a filler on chitosan based films characteristics

Starch nanoparticles were prepared by citrate esterification and ultrasound treatment. With the increase of ultrasonic treatment time, the mean size and PDI of the particles decreased gradually, when the ultrasonic treatment time was 5 min, the prepared starch nanoparticles had a mean size and PDI of 352.8 nm and 0.292, respectively. X-ray diffraction (XRD) showed that the starch nanoparticles prepared by ultrasonic treatment for 5 min had an A-type crystalline structure and a crystallinity of 41.42%. The chitosan composite films were reinforced by esterified starch with different ultrasound treatment times, the results indicated that the addition of starch nanoparticles resulted in a significant increase in the mechanical properties of films. This study indicates that esterification and ultrasound treatment can be used to prepare starch nanoparticles with a higher crystallinity and higher efficiency, which will further promote the application of nanocomposite films in packaging applications.

A review on native well-preserved chitin nanofibrils for materials of high mechanical performance

Novel chitin nanofibrils (ChNF) demonstrate excellent mechanical properties due to a long and extended polymer conformation. The current study highlights the importance of preserving ChNFs for stronger nanomaterials. Various chitin sources - crab, lobster, shrimp, squid pen, mushrooms, and insects have been reviewed. We have discussed preparation protocols and the physical properties of ChNF and presented the mechanical performance of nanomaterials. ChNF close to the native state uses fewer chemicals for treatment and shows a higher molar mass, degree of acetylation, crystallinity index, micrometer length, and a smaller diameter (3 nm), making them cheap, eco-friendly, and competitive to cellulose or synthetic fibrils. A highly acetylated or partially deacetylated ChNF forms a stable colloidal suspension, and it is possible to prepare from it strong films, hydrogels, aerogels, foams, polymer matrix nanocomposites, and microfibers. Moreover, it is possible to regenerate, functionalize, or cross-link the ChNFs to improve nanomaterials' mechanical performance. The preparation protocols remain the key to these achievements. However, the chemical techniques are not friendly ecologically and may hydrolytically degrade the chitin. The biological processes using enzymes or microorganisms are much better but still inefficient. Besides, the processing time limits the rapid preparation of the fibrils in the long-term perspective.

Thermal degradation and lifetime of β-chitin from Dosidicus gigas squid pen: Effect of impact at 9.7 GPa and a comparative study with α-chitin

The kinetics of thermal degradation of β-chitin extracted from Dosidicus gigas squid pen, was studied at normal conditions as well as after being subjected to the action of high-pressure impact of 9.7 GPa. The integral iso-conversional procedure of Kissinger-Akahira-Sunose (KAS) recommended by the ICTAC kinetics committee was applied to the non-isothermal data obtained from thermogravimetry (TGA). Lifetimes were predicted without assumption of any reaction model. Heating rates of β = 10, 15, 20 and 25 °C/min under nitrogen atmosphere were used from room temperature to 1300 °C. A comparative study with α-chitin was performed. All the samples were structurally and chemically characterized by several techniques. The extracted β-chitin was found to be in the monohydrate form; while with the action of high-pressure impact, it was transformed into β-chitin dehydrate showing slightly higher stability. Reliable prediction for lifetimes considering working temperatures over 425 K was found for α and β-chitin.

A review on the synthesis of graft copolymers of chitosan and their potential applications

Chitosan is an antimicrobial, biodegradable and biocompatible natural polymer, commercially derived from the partial deacetylation of chitin. Currently modified chitosan has occupied a major part of scientific research. Modified chitosan has excellent biotic characteristics like biodegradation, antibacterial, immunological, metal-binding and metal adsorption capacity and wound-healing ability. Chitosan is an excellent candidate for drug delivery, food packaging and wastewater treatment and is also used as a supporting object for cell culture, gene delivery and tissue engineering. Modification of pure chitosan via grafting improves the native properties of chitosan. Chitosan grafted copolymers exhibit high significance and are extensively used in numerous fields. In this review, modifications of chitosan through several graft copolymerization techniques such as free radical, radiation, and enzymatic were reported and the properties of grafted chitosan were discussed. This review also discussed the applications of grafted chitosan in the fields of drug delivery, food packaging, antimicrobial, and metal adsorption as well as dye removal.

Optically Transparent Multiscale Composite Films for Flexible and Wearable Electronics

One of the key breakthroughs enabling flexible electronics with novel form factors is the deployment of flexible polymer films in place of brittle glass, which is one of the major structural materials for conventional electronic devices. Flexible electronics requires polymer films with the core properties of glass (i.e., dimensional stability and transparency) while retaining the pliability of the polymer, which, however, is fundamentally intractable due to the mutually exclusive nature of these characteristics. An overview of a transparent fiber-reinforced polymer, which is suggested as a potentially viable structural material for emerging flexible/wearable electronics, is provided. This includes material concept and fabrication and a brief review of recent research progress on its applications over the past decade.

Maria H, Gopi S, Volova T, C. M. Fernandes S, Thomas S. Extraction of Nanochitin from Marine Resources and Fabrication of Polymer Nanocomposites: Recent Advances

Industrial sea food residues, mainly crab and shrimp shells, are considered to be the most promising and abundant source of chitin. In-depth understanding of the biological properties of chitin and scientific advancements in the field of nanotechnology have enabled the development of high-performance chitin nanomaterials. Nanoscale chitin is of great economic value as an efficient functional and reinforcement material for a wide range of applications ranging from water purification to tissue engineering. The use of polymers and nanochitin to produce (bio) nanocomposites offers a good opportunity to prepare bioplastic materials with enhanced functional and structural properties. Most processes for nanochitin isolation rely on the use of chemical, physical or mechanical methods. Chitin-based nanocomposites are fabricated by various methods, involving electrospinning, freeze drying, etc. This review discusses the progress and new developments in the isolation and physico-chemical characterization of chitin; it also highlights the processing of nanochitin in various composite and functional materials.

Nanomaterials Derived from Fungal Sources-Is It the New Hype?

Greener alternatives to synthetic polymers are constantly being investigated and sought after. Chitin is a natural polysaccharide that gives structural support to crustacean shells, insect exoskeletons, and fungal cell walls. Like cellulose, chitin resides in nanosized structural elements that can be isolated as nanofibers and nanocrystals by various top-down approaches, targeted at disintegrating the native construct. Chitin has, however, been largely overshadowed by cellulose when discussing the materials aspects of the nanosized components. This Perspective presents a thorough overview of chitin-related materials research with an analytical focus on nanocomposites and nanopapers. The red line running through the text emphasizes the use of fungal chitin that represents several advantages over the more popular crustacean sources, particularly in terms of nanofiber isolation from the native matrix. In addition, many β-glucans are preserved in chitin upon its isolation from the fungal matrix, enabling new horizons for various engineering solutions.

Polysaccharide-based component and their relevance in edible film/coating: a review

Purpose

The purpose of this paper is to present an overview of functional properties of the polysaccharide-based component and their application in developing edible film and coating for the food processing sector.

Design/methodology/approach

In this review study, approximately 271 research and review articles focusing on studies related to polysaccharide-based components and their film-forming properties. This article also focused on the application of polysaccharide-based edible film in the food sector.

Findings

From the literature reviewed, polysaccharide components and components-based edible film/coating is the biodegradable and eco-friendly packaging of the materials and directly consumed by the consumer with food. It has been reported that the polysaccharide components have excellent properties such as being nontoxic, antioxidant, antimicrobial, antifungal and with good nutrients. The polysaccharide-based edible film has lipid and gas barrier properties with excellent transparency and mechanical strength. In various studies, researchers worked on the development of polysaccharide-based edible film and coating by incorporating plant based natural antioxidants. This was primarily done for obtaining improved physical and chemical properties of the edible film and coating. In future, the technology of developing polysaccharide-based edible film and coating could be used for extending the shelf life and preserving the quality of fruits and vegetables at a commercial level. There is more need to understand the role of edible packaging and sustainability in the food and environment sector.

Originality/value

Through this review paper, possible applications of polysaccharide-based components and their function property in the formation of the edible film and their effect on fruits, vegetables and other food products are discussed after detailed studies of literature from thesis and journal article.