Effect of isolation methods of chitin nanocrystals on the properties of chitin-silver hybrid nanoparticles

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.

Production and comparison of structural, thermal and physical characteristics of chitin nanoparticles obtained by different methods

This study examined the impact of acid hydrolysis, tempo oxidation, and mechanical grinding on the physical, thermal, and structural properties of α-chitin nanocrystals and nanofibers. The manufacturing methods could influence the diameter, functional groups, and crystal patterns of the resulting nanoparticles. Analysis of the DLS results revealed that the size of acidic nanocrystals were smaller and showed improved dispersibility. The XRD patterns indicated that the chemical and mechanical treatments did not alter the crystalline arrangement of the α-chitin. FT-IR spectra analysis revealed that the chemical and mechanical methods did not affect the functional groups of the nanoparticles. DSC results showed that the nanoparticles had good thermal stability up to 400 °C, and it was found that the nanofibers had better thermal resistance due to their longer length. In the FE-SEM images, the nanoparticles were observed as fiber mats with a length of more than 100 nm. It was also found that the diameter of the nanoparticles was less than 100 nm.

Preparation of nanochitin using deep eutectic solvents

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

Optimized high-yield synthesis of chitin nanocrystals from shrimp shell chitin by steam explosion

This study attempted for the first time to prepare chitin nanocrystals (ChNCs) from shrimp shell chitin using steam explosion (SE) method. Response surface methodology (RSM) approach was used to optimize the SE conditions. Optimum SE conditions to acquire a maximum yield of 76.78 % were acid concentration (2.63 N), time (23.70 min), and chitin to acid ratio (1:22). Transmission electron microscopy (TEM) revealed the ChNCs produced by SE had an irregular spherical shape with an average diameter of 55.70 ± 13.12 nm. FTIR spectra showed ChNCs were slightly different than chitin due to a shift in peak positions to higher wavenumber and higher peak intensities. XRD patterns indicated ChNCs were a typical α-chitin structure. Thermal analysis revealed ChNCs were less thermally stable than chitin. Compared to conventional acid hydrolysis, the SE approach described in this study is simple, fast, easy, and requires less acid concentration and acid quantity, making it more scalable and efficient for synthesizing ChNCs. Furthermore, the characteristics of the ChNCs will shed light on the potential industrial uses for the polymer.

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/deacetylated chitin nanocomposite film for effective adsorption of organic pollutant from aqueous solution

Cross-linked chitin/deacetylated chitin nanocomposite films can be considered as a potential industrial adsorbent for the removal of organic pollutants for water purification. Chitin (C) and deacetylated chitin (dC) nanofibers were extracted from raw chitin and characterized using FTIR, XRD and TGA techniques. The TEM image confirmed the formation of chitin nanofibers with a diameter range of 10-45 nm. The deacetylated chitin nanofibers (DDA-46 %) having 30 nm diameter was evidenced using FESEM. Further, the C/dC nanofibers were prepared at different ratios (80/20, 70/30, 60/40 & 50/50 ratios) and cross-linked. The highest tensile strength of 40 MPa and Young's modulus of 3872 MPa was exhibited by 50/50C/dC. The DMA studies revealed that the storage modulus enhanced by 86 % for 50/50C/dC (9.06 GPa) in comparison to 80/20C/dC nanocomposite. Further, the 50/50C/dC exhibited a maximum adsorption capacity of 30.8 mg/g at pH = 4 in 30 mg/L of Methyl Orange (MO) dye within 120 min. The experimental data agreed with pseudo-second-order model indicating chemisorption process. The adsorption isotherm data was best described by Freundlich model. The nanocomposite film is an effective adsorbent can be regenerated and recycled for five adsorption-desorption cycle.

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.

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

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

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.

Influence of Chitin Nanocrystals on the Crystallinity and Mechanical Properties of Poly(hydroxybutyrate) Biopolymer

This study focuses on the use of pilot-scale produced polyhydroxy butyrate (PHB) biopolymer and chitin nanocrystals (ChNCs) in two different concentrated (1 and 5 wt.%) nanocomposites. The nanocomposites were compounded using a twin-screw extruder and calendered into sheets. The crystallization was studied using polarized optical microscopy and differential scanning calorimetry, the thermal properties were studied using thermogravimetric analysis, the viscosity was studied using a shear rheometer, the mechanical properties were studied using conventional tensile testing, and the morphology of the prepared material was studied using optical microscopy and scanning electron microscopy. The results showed that the addition of ChNCs significantly affected the crystallization of PHB, resulting in slower crystallization, lower overall crystallinity, and smaller crystal size. Furthermore, the addition of ChNCs resulted in increased viscosity in the final formulations. The calendering process resulted in slightly aligned sheets and the nanocomposites with 5 wt.% ChNCs evaluated along the machine direction showed the highest mechanical properties, the strength increased from 24 to 33 MPa, while the transversal direction with lower initial strength at 14 MPa was improved to 21 MPa.

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.

Nanocomposites derived from licorice residues cellulose nanofibril and chitosan nanofibril: Effects of chitosan nanofibril dosage on resultant properties

Research on nanocomposite film from natural polymers such as cellulose and chitosan is of great importance to promote the development and highly efficient utilization of green and renewable bioresources. In this study, enzymatic pretreatment cellulose nanofibril (ETCNF) derived from licorice residues was prepared, and further processed into nanocomposite film with addition of chitosan nanofibril (CHN). This study focused on the effects of CHN dosage on the main properties of resultant nanocomposite film in terms of crystallinity, thermal stability, light transmittance, hydrophobicity, mechanical properties, and antibacterial activity. The results showed that ETCNF/CHN nanocomposite film exhibited good hydrophobicity especially at higher dosage of CHN, good light transmittance and mechanical properties (tensile strain can reach 39.6 MPa for ETCNF/CHN-10.0%). The as-prepared ETCNF/CHN nanocomposite film also showed good antibacterial activity against Escherichia coli. It was expected that the ETCNF/CHN nanocomposite film would help to realize transformation and high value-added utilization of these biomass residues.

Design strategies, properties and applications of cellulose nanomaterials-enhanced products with residual, technical or nanoscale lignin-A review

With the increasing demand for greener alternatives to fossil-derived products, research on cellulose nanomaterials (CNMs) has rapidly expanded. The combination of nanoscale properties and sustainable attributes makes CNMs an asset in the quest for a sustainable society. However, challenges such as the hydrophilic nature of CNMs, their low compatibility with non-polar matrices and modest thermal stability, slow the development of end-uses. Combination of CNMs with amphiphilic lignin can improve the thermal stability, enhance the compatibility with non-polar matrices and, additionally, endow CNMs with new functionalities e.g., UV shielding or antioxidative properties. This article comprehensively reviews the different design strategies and their influence on properties and applications of CNMs containing lignin in various forms; either as residual lignin, added technical lignin, or nanoscale particles. The review focuses especially on the synergy created between CNMs and lignin, paving the way for new production routes and use of CNM/lignin materials in high-performance applications.

Selective Isolation Methods for Cellulose and Chitin Nanocrystals

This Minireview focuses on the selective isolation methods for the preparation of cellulose nanocrystals (CNCs) and chitin nanocrystals (ChNCs). Various selective preparation strategies with specific preparation conditions and reaction mechanisms are summarized. In particular, these selective reaction routes include controlled acid hydrolysis and selective oxidations at specific positions of cellulose or chitin fibers as well as particular reaction sites of the repeating monosaccharide building blocks of their main chains. These lead to selective cleavage of the ordered and non-ordered regions of cellulose and chitin and result in efficient production of CNCs and ChNCs.

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.

Highly recyclable and super-tough hydrogel mediated by dual-functional TiO2 nanoparticles toward efficient photodegradation of organic water pollutants

A novel photocatalytic hydrogel was prepared by loading TiO₂ nanoparticles (TiO₂ NPs) onto the surface of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized chitin nanofibers (TOCNs), which were further incorporated into the polyacrylamide (PAM) matrix. The resultant hydrogel exhibited a macro-porous structure with a low density (~1.45 g/cm³) and high water content (~80%). The well-dispersed TiO₂ NPs not only acted as a crosslinking agent for bridging the three-dimensional porous network structure, but also endowed the hydrogel with good catalytic activity. After the introduction of TiO₂ accounting for 10 wt% of the hydrogel mass, the hydrogels showed compressive strength of 1.46 MPa at 70% strain, tensile stress of 316 kPa, tensile strain of 310%, toughness of 47.25 kJ/m³ and fatigue resistance. Compared with neat TOCN-PAM hydrogel, the uniaxial compressive and tensile strengths of the TiO₂-TOCN-PAM10 hydrogel increased 6.35-fold and 3.70-fold, respectively. Furthermore, the removal of methyl orange (MO) was attributed to the synergistic effect of the adsorption and photocatalytic degradation of the hydrogels. The hydrogels adsorbed up to 8.5% of MO after 150 min of adsorption and a photocatalytic degradation rate of 97.3% achieved after 90 min of UV irradiation at pH = 2. Especially, the TiO₂-TOCN-PAM10 hydrogel exhibited excellent recycling performance: its MO removal efficiency was around 96% even after 10 reuse cycles. The as-prepared hydrogels, with characteristics of excellent stretchability, photocatalytic activity and recyclability, are expected to be used in alleviating organic pollutants in practical wastewater treatments.

Preparation of multifunctional carboxymethyl cellulose-based films incorporated with chitin nanocrystal and grapefruit seed extract

Chitin nanocrystals (ChNC) were isolated from shrimp shells powder using acid hydrolysis and ammonium persulfate methods. Multifunctional carboxymethyl cellulose (CMC) composite films were prepared by adding ChNC and grapefruit seed extract (GSE), and their effects on the optical, mechanical, water vapor barrier, and antibacterial properties of CMC film were investigated. The isolated ChNC had a needle-like structure with a length of 340-370 nm and a diameter of 18-20 nm depending on the isolation method. The CMC films prepared with ChNC and GSE were transparent with high UV barrier properties. The addition of GSE reduced the strength (TS) and stiffness (EM) of CMC films by 10.4% and 30.3%, respectively, while the flexibility (EB) increased by 17.7%. However, when the ChNC was added, the TS and EM of CMC film increased by 19.7% and 58.7%, respectively, and the EB remained the same. The addition of ChNC reduced the water vapor permeability (WVP) of the CMC film by 27%. CMC films containing GSE also showed strong antibacterial activity against foodborne pathogenic bacteria, E. coli and L. monocytogenes.

Applications of cellulose and chitin/chitosan derivatives and composites as antibacterial materials: current state and perspectives

The bacterial infections have always a serious problem to public health. Scientists are developing new antibacterial materials to overcome this problem. Polysaccharides are promising biopolymers due to their diverse biological functions, low toxicity, and high biodegradability. Chitin and chitosan have antibacterial properties due to their cationic nature, while cellulose/bacterial cellulose does not possess any antibacterial activity. Moreover, the insolubility of chitin in common solvents, the poor solubility of chitosan in water, and the low mechanical properties of chitosan have restricted their biomedical applications. In order to solve these problems, chemical modifications such as quaternization, carboxymethylation, cationization, or surface modification of these polymers with different antimicrobial agents, including metal and metal oxide nanoparticles, are carried out to obtain new materials with improved physiochemical and biological properties. This mini review describes the recent progress in such derivatives and composites with potential antibacterial applications.