Lignin nanoparticles formation by multiscale structure control to regulate morphology and their adsorption, nucleation, and growth on chitin nanofibers.

The lignin nanoparticles (LNPs) synthesis relies on lignin polymers with heterogeneous molecules and properties, which impose significant limitations on the preparation and property regulation. The multiscale structure of lignin from monomers to oligomers, provides a potential pathway for precise regulation of its physical and chemical properties. The study addresses this challenge by employing coniferyl alcohol and sinapyl alcohol as monomers and separately utilizing the Zulaufverfaren (ZL) and Zutropfverfaren (ZT) methods to synthesize different types of lignin dehydrogenation polymers (DHPs) including guaiacyl (G)-ZL-DHP, G-ZT-DHP, syringyl (S)-ZL-DHP, and S-ZT-DHP. The investigation highlights the chemical bonds as essential components of lignin primary structure. Additionally, the secondary structure is influenced by branched and linear molecular structures. G unit provides some branching points, which are utilized and amplified in the ZL process of DHPs synthesis. The branched DHPs aggregate at the edge and form rod-like LNPs. While linear DHPs aggregate around the center, presenting polygonal LNPs. The study identifies that the branched LNPs, characterized by more surface charges and lower steric hindrance, can form a stable complex with chitin nanofibers. Emulsions with varying oil-to-water ratios were subsequently prepared, opening a new window for the application of LNPs in fields such as food and cosmetics.

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.

Antireflective Superhydrophobic and Robust Coating Based on Chitin Nanofibers and Methylsilanized Silica for Outdoor Applications.

Antireflective coatings with superhydrophobicity have many outdoor applications, such as solar photovoltaic panels and windshields. In this study, we fabricated an omnidirectional antireflective and superhydrophobic coating with good mechanical robustness and environmental durability via the spin coating technique. The coating consisted of a layer of phytic acid (PA)/polyacrylamide (PAM)/calcium ions (Ca2+) (referred to as Binder), an antireflective layer composed of chitin nanofibers (ChNFs), and a hydrophobic layer composed of methylsilanized silica (referred to as Mosil). The transmittance of a glass slide with the Binder/ChNFs/Mosil coating had a 5.2% gain at a wavelength of 550 nm, and the antireflective coating showed a water contact angle as high as 160° and a water sliding angle of 8°. The mechanical robustness and environmental durability of the coating, including resistance to peeling, dynamic impact, chemical erosion, ultraviolet (UV) irradiation, and high temperature, were evaluated. The coating retained excellent antireflective capacity and self-cleaning performance in the harsh conditions. The increase in voltage per unit area of a solar panel with a Binder/ChNFs/Mosil coating reached 0.4 mV/cm2 compared to the solar panel exposed to sunlight with an intensity of 54.3 × 103 lx. This work not only demonstrates that ChNFs can be used as raw materials to fabricate antireflective superhydrophobic coatings for outdoor applications but also provides a feasible and efficient approach to do so.

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.

Intra-Articular Injection of Chitin Nanofiber Attenuates Osteoarthritis: An Experimental Study in a Rat Model of Osteoarthritis.

Background: This study aimed to evaluate the effect of chitin nanofibers (CNF) produced from crab shells as a medical material for the knee in an osteoarthritic rat model. Methods: The effect of intra-articular CNF injection was evaluated histologically among three groups: saline, hyaluronic acid (HA), and CNF injection groups. The Osteoarthritis Research Society International (OARSI) cartilage, subchondral bone, synovial, and meniscus scores were used for scoring. Results: At 4 weeks, the CNF group had significantly lower scores than the saline group. The Synovial score was lower in HA and CNF groups at 4 weeks than in the saline group. At 4 weeks post-treatment, the thickening of the subchondral bone plate and angiogenesis were significantly reduced in the CNF treatment group compared to those in the saline treatment group (P = 0.02). Conclusion: The anti-inflammatory effects of CNF on knee osteoarthritis were comparable to that of HA in the early stages.

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.

Assembly of porous filaments by interfacial complexation of nanochitin-based Pickering emulsion and seaweed alginate.

Interfacial polyelectrolyte complexation spinning is an all-water, easy-to-operate method for production of composite filaments. Herein, this concept is extended to interfacial polyelectrolyte-emulsion complexation (IPEC) that better encodes structural and functional attributes of biomass substances into the filaments. This allows for formation of composite filaments by drawing contacting oppositely-charged chitin nanofiber-stabilized Pickering emulsion and seaweed alginate solution. The parameters affecting spinnability of the system including water-to-oil ratio, alginate concentration, and pH are comprehensively elucidated to support the design and application of IPEC. The composite filaments exhibit varied diameters and diverse porous structures that are adjustable by properties of Pickering droplets. The droplet diameter of precursor emulsion and pore size in the filaments are well correlated, revealing controllability of the IPEC spinning. The filaments are mechanically robust in dry condition and show stable performance even in wet condition. The release rate of filaments that is pre-loaded with hydrophilic drug is regulated by the internal pore size, showing capability on sustained release. This study offers a new perspective toward dry spinning via interfacial complexation of complicated nanochitin-based structural building blocks, aiming at developing high-performance fiber materials for advanced applications.

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.

Chitosan/esterified chitin nanofibers nanocomposite films incorporated with rose essential oil: Structure, physicochemical characterization, antioxidant and antibacterial properties.

Active films were developed based on chitosan, esterified chitin nanofibers and rose essential oil (REO). The joint effects of chitin nanofibers and REO on structure and physicochemical properties of chitosan film were investigated. Scanning electron microscopy and Fourier transform infrared spectroscopy showed that the chitin nanofibers and REO had significant effects on the morphology and chemical structure of chitosan composite films. The negatively charged esterified chitin nanofibers formed a compact network structure through intermolecular hydrogen bonding and electrostatic interactions with the positively charged chitosan matrix. Chitin nanofibers and REO synergistically enhanced the water resistance, mechanical properties and UV resistance of chitosan-based films, but the addition of REO increased the oxygen permeability. Furthermore, the addition of REO enhanced the inhibition of ABTS and DPPH free radicals and microorganisms by chitosan-based film. Therefore, chitosan/chitin nanofiber-based active films containing REO as food packaging materials can potentially provide protection to extend food shelf life.

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 that can be regenerated and recycled for five adsorption-desorption cycle.

Development and characterization of active packaging based on chitosan/chitin nanofibers incorporated with scallion flower extract and its preservation in fresh-cut bananas.

The aim of this study was to develop a novel active packaging using chitosan (CS) and esterified chitin nanofibers (CF) combined with different contents (1, 2 and 4 wt% on CS basis) of scallion flower extract (SFE) to protect banana samples. The addition of CF significantly improved the barrier and mechanical properties of the CS films (p < 0.05) due to hydrogen bonds and electrostatic interactions. Moreover, the addition of SFE not only improved the physical properties of the CS film but also improved the CS film biological activity. The oxygen barrier property and antibacterial ability of CF-4%SFE were approximately 5.3 and 1.9 times higher than those of the CS film, respectively. In addition, CF-4%SFE had strong DPPH radical scavenging activity (74.8 ± 2.3 %) and ABTS radical scavenging activity (84.06 ± 2.08 %). Fresh-cut bananas stored in CF-4%SFE showed less weight loss, starch loss, color and appearance change than those stored in traditional polyethylene film, which indicated that CF-4%SFE was much better at storing fresh-cut bananas than conventional plastic packaging. For these reasons, CF-SFE films have great potential as a candidate to replace traditional plastic packaging and extend the shelf life of packaged foods.

Yeast biomass ornamented macro-hierarchical chitin nanofiber aerogel for enhanced adsorption of cadmium(II) ions.

There is an urgent need to develop sustainable, renewable, and environment-friendly adsorbents to rectify heavy metals from water. In the current study, a green hybrid aerogel was prepared by immobilizing yeast on chitin nanofibers in the presence of a chitosan interacting substrate. A cryo-freezing technique was employed to construct a 3D honeycomb architecture comprising the hybrid aerogel with excellent reversible compressibility and abundant water transportation pathways for the accelerated diffusion of Cadmium(II) (Cd(II)) solution. This 3D hybrid aerogel structure offered copious binding sites to accelerate the Cd(II) adsorption. Moreover, the addition of yeast biomass amplified the adsorption capacity and reversible wet compression of hybrid aerogel. The monolayer chemisorption mechanism explored by Langmuir and pseudo-second-order kinetic exhibited a maximum adsorption capacity of 127.5 mg/g. The hybrid aerogel demonstrated higher compatibility for Cd(II) ions as compared to the other coexisted ions in wastewater and manifested a better regeneration potential following four consecutive sorption-desorption cycles. Complexation, electrostatic attraction, ion-exchange and pore entrapment were perhaps major mechanisms involved in the removal of Cd(II) revealed by XPS and FT-IR. This study unveiled a novel avenue for efficient green-synthesized hybrid aerogel that may be sustainably used as an excellent purifying agent for Cd(II) removal from wastewater.

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.

Polysaccharide Nanofiber-Stabilized Pickering Emulsion Microparticles Induce Pyroptotic Cell Death in Hepatocytes and Kupffer Cells.

The intracellular uptake and interaction behavior of emulsion microparticles in liver cells critical to host defense and inflammation is significant to understanding their potential cytotoxicity and biomedical applications. In this study, the cell death responses of fibroblastic, hepatocyte, and Kupffer cells (KCs) induced by four types of emulsion particles that are stabilized by polysaccharide nanofibers (cellulose or chitin), an inorganic nanoparticle (ß-tricalcium phosphate), or surfactants are compared. Pickering emulsion (PE) microparticles stabilized by polysaccharide nanofibers or inorganic nanoparticles have a droplet size of 1-3 µm, while the surfactant-stabilized emulsion has a diameter of ≈190 nm. Polysaccharide nanofiber-stabilized PEs (PPEs) markedly induce lactate dehydrogenase release in all cell types. Additionally, characteristic pyroptotic cell death, which is accompanied by cell swelling, membrane blebbing, and caspase-1 activation, occurs in hepatocytes and KCs. These PE microparticles are co-cultured with lipopolysaccharide-primed KCs associated with cytokine interleukin-1ß release, and the PPEs demonstrate biological activity as a mediator of the inflammation response. Well-designed PPE microparticles induce pyroptosis of liver cells, which may provide new insight into regulating inflammation-related diseases for designing potent anticancer drugs and vaccine adjuvants.

Photocrosslinked Fish Collagen Peptide/Chitin Nanofiber Composite Hydrogels from Marine Resources: Preparation, Mechanical Properties, and an In Vitro Study.

Fish collagen peptide (FCP) is a water-soluble polymer with easy accessibility, bioactivity, and reactivity due to its solubility. The gelation of FCP can be carried out by chemical crosslinking, but the mechanical strength of FCP hydrogel is very low because of its intrinsically low molecular weight. Therefore, the mechanical properties of FCP gel should be improved for its wider application as a biomaterial. In this study, we investigated the mechanical properties of M-FCP gel in the context of understanding the influence of chitin nanofibers (CHNFs) on FCP hydrogels. FCP with a number average molecular weight (Mn) of ca. 5000 was reacted with glycidyl methacrylate (GMA) and used for the preparation of photocrosslinked hydrogels. Subsequently, composite hydrogels of methacrylate-modified FCP (M-FCP) and CHNF were prepared by the photoirradiation of a solution of M-FCP containing dispersed CHNF at an intensity of ~60 mW/cm2 for 450 s in the presence of 2-hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone (Irgacure 2959) as a photoinitiator. Compression and tensile tests of the FCP hydrogels were carried out using a universal tester. The compression and tensile strength of the hydrogel increased 10-fold and 4-fold, respectively, by the addition of 0.6% CHNF (20% M-FCP), and Young's modulus increased 2.5-fold (20% M-FCP). The highest compression strength of the M-FCP/CHNF hydrogel was ~300 kPa. Cell proliferation tests using fibroblast cells revealed that the hydrogel with CHNF showed good cell compatibility. The cells showed good adhesion on the M-FCP gel with CHNF, and the growth of fibroblast cells after 7 days was higher on the M-FCP/CHNF gel than on the M-FCP gel without CHNF. In conclusion, we found that CHNF improved the mechanical properties as well as the fibroblast cell compatibility, indicating that M-FCP hydrogels reinforced with CHNF are useful as scaffolds and wound-dressing materials.

Porosity-Induced Improvement in KOH Activation of Chitin Nanofiber-Based Porous Carbon Leading to Ultrahigh Specific Capacitance.

The applicability of chitin-based carbon as a supercapacitor electrode material was investigated by adjusting its pore structure through polystyrene latex templating, without significant N doping. 2,2,6,6-tetramethylpiperidinyloxy (TEMPO)-oxidized chitin nanofibers were mixed with polystyrene latex, hydrothermally treated at 220 °C, carbonized, and activated using KOH at 800 °C, yielding activated hierarchical porous carbon. The variation of both polystyrene latex amount and carbonization temperature resulted in changes in the surface area and pore structure, which dictated the degree of pore uniformity and activation efficiency. The pore structure affected activation by allowing the selective removal of amorphous carbon, exposing the basal plane carbon, resulting in higher specific capacitance. By making activated hierarchical porous carbon more conducive to activation, specific capacitance of 567 F g-1 at 0.5 A g-1 was achieved, with no loss in performance after 10000 charge-discharge cycles.

A 3D printable dynamic nanocellulose/nanochitin self-healing hydrogel and soft strain sensor.

Presented here is the synthesis of a 3D printable nano-polysaccharide self-healing hydrogel for flexible strain sensors. Consisting of three distinct yet complementary dynamic bonds, the crosslinked network comprises imine, hydrogen, and catecholato-metal coordination bonds. Self-healing of the hydrogel is demonstrated by macroscopic observation, rheological recovery, and compression measurements. The hydrogel was produced via imine formation of carboxyl methyl chitosan, oxidized cellulose nanofibers, and chitin nanofibers followed by two subsequent crosslinking stages: immersion in tannic acid (TA) solution to create hydrogen bonds, followed by soaking in FeIII solution to form catecholato-metal coordination bonds between TA and FeIII. The metal coordination bonds were critical to imparting conductivity to the hydrogel, a requirement for flexible strain sensors. The hydrogel exhibits excellent shear-thinning and dynamic properties with high autonomous self-healing (up to 89%) and self-recovery (up to 100%) at room temperature without external stimuli. Furthermore, it shows good printability, biocompatibility, and strain sensing ability.

Efficient Protection of Silver Nanowire Transparent Electrodes by All-Biorenewable Layer-by-Layer Assembled Thin Films.

An efficient protection strategy for silver nanowire-based transparent electrodes (AgNW TEs) is developed to enhance their poor adhesion force on substrates and thermal, optical, chemical, and electrical stabilities. Chitin nanofibers (CNFs) and alkali lignin (AL), which possess high mechanical property, a gas/moisture barrier, and UV absorption properties, are successively assembled on AgNW TEs through layer-by-layer (LBL) assembly based on their oppositely charged surfaces. The formation of LBL-assembled CNFs and AL (CNF/AL)10 bilayers, where 10 is the optimized number of bilayers, on the aldehyde-modified AgNW (Al-AgNW) TEs does not deteriorate their electrical conductivity (17.3 ± 2.1 Ω/□) and transmittance (90.1 ± 0.3% at 550 nm), and the (CNF/AL)10 bilayer-coated Al-AgNW [(CNF/AL)10@Al-AgNW] TEs present considerable enhancement in their adhesion force and thermal, optical, chemical, and electrical durability. In detail, their optoelectrical properties are stable over 200 cycles of the scotch peel-off test, for 10 h sonication, up to 350 °C, under UV/O3 treatment for 100 min, in 10% HCl and 28% NH3 for 6 and 12 h, and at an electrical potential up to 14 V, respectively. These features make (CNF/AL)10@Al-AgNW TEs suitable as a durable high-performance transparent heater.

Disease resistance and growth promotion activities of chitin/cellulose nanofiber from spent mushroom substrate to plant.

Some studies have reported the method for treating the spent mushroom substrate (SMS). However, the effective use as a functional raw material based on properties of SMS remains a formidable challenge. In this study, we investigated the usefulness of SMS in agriculture to develop a new method for treating and utilizing it. First, we attempted to isolate chitin/cellulose nanofiber complex (CCNFC) from SMS using chemical pretreatment and mechanical fibrillation. The characterization results like SEM, FT-IR, and XRD showed that we successfully isolated the CCNFC from SMS. Second, we explored the biological activities of the CCNFC for its potential application as a functional agricultural nanomaterial. CCNFC water dispersion with low concentration (0.1 and 1 mg/mL) exhibited significant plant disease resistance and plant growth promotion activities. Our results suggested that SMS may provide a useful source of functional agricultural nanomaterial, which may contribute to treating and applying it in agriculture.

Bioactive Pectin-Murta (Ugni molinae T.) Seed Extract Films Reinforced with Chitin Fibers.

This study investigated the biocomposite pectin films enriched with murta (Ugni molinae T.) seed polyphenolic extract and reinforced by chitin nanofiber. The structural, morphological, mechanical, barrier, colorimetric, and antioxidant activity of films were evaluated. The obtained data clearly demonstrated that the addition of murta seed extract and the high load of chitin nanofibers (50%) provided more cohesive and dense morphology of films and improved the mechanical resistance and water vapor barrier in comparison to the control pectin film. The antioxidant activity ranged between 71% and 86%, depending on the film formulation and concentration of chitin nanofibers. The presented results highlight the potential use of chitin nanofibers and murta seed extract in the pectin matrix to be applied in functional food coatings and packaging, as a sustainable solution.