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Utilizing the emulsion-forming ability of partially deacetylated chitin nanofibers, a composite with polystyrene was prepared. A partially deacetylated chitin nanofiber aqueous dispersion was added to styrene to obtain an oil in a water-type Pickering emulsion. Using the emulsion, suspension polymerization was performed to obtain polystyrene fine particles covered with chitin nanofibers. The degree of polymerization of polystyrene increased depending on the mixing ratio of chitin nanofibers. The glass transition temperature of polystyrene and the thermal decomposition temperature of the composite increased with the mixing ratio of chitin nanofibers. This composite could be molded by hot pressing, and the molded product was transparent to some extent. Since chitin nanofibers effectively reinforced polystyrene, Young’s modulus, fracture stress, and fracture strain were greatly improved. The optimum mixing ratio of chitin nanofibers for improving mechanical properties was 7%. When the composite was molded by hot pressing again, the mechanical properties did not decrease. Thus, the nanofiber reinforcement material was recyclable. Utilizing the emulsion-forming ability of partially deacetylated chitin nanofibers, a composite with polystyrene (PS) was prepared. A partially deacetylated chitin nanofiber aqueous dispersion was added to styrene to obtain an oil in a water-type Pickering emulsion. Using the emulsion, suspension polymerization was performed to obtain PS fine particles covered with chitin nanofibers. This composite could be molded by hot pressing, and the molded product was transparent to some extent. Mechanical properties of PS were greatly improved. When the composite was molded again, the mechanical properties did not decrease.

Blue, red and yellow chitin nanofibers were obtained using reactive dyes. Since the chitin nanofibers and the dye are covalently bonded, they are resistant to hot water and detergents. Since the dyed chitin nanofibers can be mixed at an arbitrary ratio, purple, orange, and green nanofibers corresponding to the mixed colors could be obtained. The dyed chitin nanofibers were evaluated by the reflection spectrum and the color space (L*a*b*). From the viewpoint of reaction yield and color properties, the appropriate ratio of the reactive dye to chitin was 5% at the maximum. The morphology of chitin nanofibers was maintained even after the introduction of the reactive dye. A resin combined with dyed chitin nanofibers was prepared. By combining with nanofibers, it may be possible to give color and improve mechanical strength to resin while maintaining the transparency of the resin to some extent.

In this study, maleated chitin nanofibers (MCNFs)-poly (vinyl alcohol) (PVA) composite films were fabricated to evaluate the reinforcement effect of MCNFs to PVA. Maleated chitin nanofibers (MCNFs) were prepared by esterification of α-chitin powder with maleic anhydride and 2 passes grinder treatment. The average diameter of MCNFs was about 10 nm. The PVA-MCNF composites films were prepared by solution casting technique at 0, 1, 3, 5, 10 and 15 wt% of MCNFs. The FTIR and XRD analyses revealed that, there were strong interaction between MCNFs and PVA. The nanocomposite films displayed nearly similar transparency level of PVA film suggesting that the MCNFs were dispersed at the nanoscale range. Both the DSC and TGA analyses have shown that, thermal stability of PVA was significantly enhanced upon inclusion of MCNFs. The tensile testing data also indicated that, the Young’s modulus, tensile strength, elongation at break and toughness of PVA were increased by 71.87%, 41.47%, 49.10% and 261.20%, respectively through incorporation of 3 wt% MCNFs into the PVA matrix. The maximum swelling index of PVA film in deionized water (195%) was reduced to 141% for 3 wt% MCNFs containing composite film. The strong interfacial interactions between MCNFs and PVA were the decisive factors for the betterment of PVA properties. Generally, this study demonstrates a substantial approach in making thermo-mechanically stable and less water sensitive biodegradable nanocomposite films to be applied in making flexible packaging and biomedical materials.

Many biological high-performance composites, such as bone, antler, and crustacean cuticles, are composed of densely mineralized and ordered nanofiber materials. The mimicry of even simplistic bioinspired structures, i.e., of densely and homogeneously mineralized nanofibrillar materials with controllable mechanical performance, continues to be a grand challenge. Here, using alkaline phosphatase as an enzymatic catalyst, we demonstrate the dense, homogeneous, and spatially controlled mineralization of calcium phosphate nanostructures within networks of anionically charged cellulose nanofibrils (CNFs) and cationically charged chitin nanofibrils (ChNFs)-both emerging biobased nanoscale building blocks for sustainable high-performance materials design. Our study reveals that anionic CNFs lead to a more homogeneous nanoscale mineralization with very high mineral contents up to ca. 70 wt % with a transition from amorphous to crystalline deposits, while cationic ChNFs yield rod-like crystalline morphologies. The bone-inspired CNF bulk films exhibit a significantly increased stiffness, maintain good flexibility and translucency, and have a significant gain in wet state mechanical properties. The mechanical properties can be tuned both by the enzyme concentration and the mineralization time. Moreover, we also show a spatial control of the mineralization using kinetically controlled substrate uptake in a dialysis reactor, and by spatially selectively incorporating the enzyme into 2D printed filament patterns. The strategy highlights possibilities for spatial encoding of enzymes in tailored structures and patterns and programmed mineralization processes, promoting the potential application of mineralized CNF biomaterials with complex gradients for bone substitutes and tissue regeneration in general.

Pelleted preparations were formulated from sacran (Sac), an anionic, sulfated, carboxyl-containing polysaccharide, which is extracted from the Japanese indigenous cyanobacterium Aphanothece sacrum, and surface-deacetylated chitin nanofibers (SDACNF). The use of this material as an extended-release excipient for tetrahydrocurcumin (THC), a model drug that is used to treat wounds via its radical scavenging ability was examined. The THC used in the study was complexed with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), which increases its water solubility. The radical scavenging activity of the THC/HP-β-CD complex (molar ratio of 1:1) was significantly higher than the values for SDACNF or Sac alone. The rate of release of THC from the Sac/SDACNF pellets containing the THC/HP-β-CD complex decreased with increasing Sac content in the pellet, suggesting that Sac/SDACNF (1:1) and Sac alone pellets function as extended-release excipients for THC. The findings reported here indicate that this can be attributed to the ability of the Sac component to retain fluids, thus extending the effects of the drug. In view of the above experimental outcomes, i.e. wound healing efficacy, fluid absorption, retention and the extended drug release of the system indicates that this preparation, in the appropriate ratios, has the potential for use as a controlled-release drug in wound healing.

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.

Chitin nanofibers were prepared from crab shell for the purpose of utilizing crab shells. After the series chemical treatment and wet pulverization treatment, a uniform fibrous substance having a width of about 10 nm was obtained. The reason why fine fibrous chitin can be obtained is the structure of the crab shell. A characteristic of chitin nanofibers is their high dispersibility in water. Therefore, processing ability is improved, and biological properties of the nanofibers can be evaluated. Chitin nanofibers whose surface is modified to chitosan can be obtained after treatment with a relatively medium concentration of sodium hydroxide. Since chitosan nanofibers have an amino group on the surface, they are positively charged in an acidic aqueous solution. Chitin and chitosan nanofibers have various physiological functions when taken or applied to the skin. Effects of oral ingestion of chitosan nanofibers on chronic kidney disease (CKD) model, non-alcoholic steatohepatitis model, and inflammatory bowel disease model were studied. Furthermore, the biological effects of chitin and chitosan nanofibers for the skin are also investigated.

Optically transparent fibroin nanofiber (FNF) paper was obtained without using binders by passing a fibroin suspension through a mechanical nanofibrillation process using a water-jet. The optical transmittance of the nanofiber paper increased with the number of passes through the water-jet and reached 79.3% and 80.3% of light at 600 nm after 15 and 30 passes, respectively. The fibroin of the transparent nanopaper remained fibrous with a native β-sheet secondary structure. Therefore, the transparent nanopaper showed a high elastic modulus, high thermal durability, and low thermal expansion. This novel protein material, which can be fabricated without toxic chemicals or organic solvents, is bio-friendly and shows promise for new applications in biocompatible photonic devices.

Sorbitol polyglycidyl ether (SPE), which is a bio-based water-soluble epoxy resin, was cured with lysine (Lys) and arginine (Arg) as basic amino acids and with cysteine (Cys) as an acidic amino acid. Furthermore, biocomposites of the Lys- and Arg-cured SPE (SPE-Lys and SPE-Arg) and Cys-cured SPE (SPE-Cys) with chitin nanofiber (ChNF) not higher than 10 wt% were successfully prepared by compression molding and casting methods, respectively. Also, SPE-Cys biocomposites with chitosan nanofiber (CsNF) not higher than 2 wt% were successfully prepared by the casting method. The FT-IR spectral analysis of the cured resins suggested that the e-amino and carboxy groups of Lys, α-amino and carboxy groups of Arg, thiol group of Cys mainly reacted with epoxy groups of SPE. The FT-IR spectral analysis of the ChNF biocomposites suggested that a side reaction of SPE with acetic acid which was contained in ChNF suspension occurred. The dynamic mechanical analysis revealed that a higher order of the loss modulus peak temperature (Tα) was SPE-Lys (39 °C) > SPE-Arg (33 °C) > SPE-Cys (21 °C). Although Tαs of ChNF biocomposites were lower than those of the corresponding cured resins, Tαs of SPE-Cys/CsNF biocomposites were higher than that of SPE-Cys by the action of CsNF as a basic catalyst. The storage moduli over the range of 50–100 °C for SPE-Lys/ChNF, SPE-Cys/ChNF and SPE-Cys/CsNF biocomposites were much higher than those for the corresponding cured resins. SPE-Lys/ChNF and SPE-Cys/CsNF biocomposites exhibited higher tensile strengths and moduli than SPE-Lys and SPE-Cys did, respectively.

The development of chitin-based materials with favorable mechanical properties and biocompatibility is an important research goal owing to the wide-ranging practical applications. In this study, a composite film was prepared using chitin nanofibers and gelatin. The CNF/gelatin composite film was highly viscous and had a fine nanofiber structure. The transmittances indicated high transparency, regardless of nanofiber content. The water content of the CNF/gelatin composite film increased linearly as the gelatin content increased. Although the CNF/gelatin composite film did not induce severe inflammation, it strongly induced fibroblast proliferation, indicating high biocompatibility. Based on these results, the films are suitable for biological applications, e.g., tissue engineering, medicines, and cosmetics.

Chitin nanofibers were prepared by grinder pretreatments and subsequent mechanical treatment using a high-pressure water-jet (HPWJ) system. From SEM observations, grinder pretreatment improved disintegration efficiency in subsequent HPWJ treatment. That is, with pretreatment, excellent nanofiber networks were observed after a single HPWJ treatment, and sufficient nano-fibrillation was accomplished with 5 cycles of HPWJ treatments. The characteristic crystalline structure of α-chitin and degree of relative crystallinity were maintained after a series of mechanical treatments. From UV-Vis spectra, grinder pretreatment improved transparency of chitin nanofiber slurry, indicating the pretreatment facilitated subsequent HPWJ mechanical disintegration. Viscosities of chitin nanofiber slurry also showed that the grinder pretreatment and HPWJ treatment disintegrated the chitin into nanofiber very well. However, excessive HPWJ treatment decreased nano-fiber length, resulting in lower viscosity.

The multifunctional beneficial properties of chitosan in biomedical applications have been recognized in recent years. A major focus of these studies concerned the antioxidant properties of chitosan and its derivatives. In patients and in model rats with chronic renal failure (CRF), the application of chitosan demonstrated high antioxidant activity as well as renoprotective effects. Ingestion of surface-deacetylated chitin (SDAC) nanofibers by CRF rats resulted in a significant decrease in the levels of uremic toxins and oxidative stress, when compared with SDAC. The preparation of elastic gels SDACNFs/ sulfobutyl ether β-cyclodextrin (SBE-β-CD), starting with SDACNFs nanofibers with SBE-β-CD and containing prednisolone proved useful in the study of ulcerous colitis as an experimental model of another disease related to oxidative stress. This technique proved to be an efficient strategy for studies of the effects of chitosan and derivatives, such as SDACNF, in diseases linked to oxidative stress.

A freeze-dried gel composed of surface-deacetylated chitin nanofibers (SDACNFs), reinforced with an anionic cyclodextrin, sulfobutyl ether β-cyclodextrin (SBE-β-CD) was evaluated for treating wounds in a rat model, and the results were compared with a SDACNFs gel without SBE-β-CD. The incorporation of prednisolone (PD), a poorly water-soluble drug, in both types of gels and its release from the gels were also compared. In both cases, wound areas were decreased and their effect was higher than that of commercially available wound dressings. The rate of release of PD from the freeze-dried SDACNFs/SBE-β-CD was much faster than that form SDACNFs alone without SBE-β-CD, due to fact that the PD is more soluble in the amorphous SBE-β-CD complex compared to the other preparations. The findings indicate that the freeze-dried SDACNFs/SBE-β-CD gel would be beneficial as a new biomaterial for the treatment of wounds and for preparing homogeneous high-content gels that contain poorly water-soluble drugs.

To investigate the effects of salinity on the behavior and toxicity of functionalized single-walled carbon nanotubes (SWCNTs), which are chemical modified nanotube to increase dispersibility, medaka embryos were exposed to non-functionalized single-walled carbon nanotubes (N-SWCNTs), water-dispersible, cationic, plastic-polymer-coated, single-walled carbon nanotubes (W-SWCNTs), or hydrophobic polyethylene glycol-functionalized, single-walled carbon nanotubes (PEG-SWCNTs) at different salinities, from freshwater to seawater. As reference nanomaterials, we tested dispersible chitin nanofiber (CNF), chitosan-chitin nanofiber (CCNF) and chitin nanocrystal (CNC, i.e. shortened CNF). Under freshwater conditions, with exposure to 10 mg l−1 W-SWCNTs, the yolk sacks of 57.8% of embryos shrank, and the remaining embryos had a reduced heart rate, eye diameter and hatching rate. Larvae had severe defects of the spinal cord, membranous fin and tail formation. These toxic effects increased with increasing salinity. Survival rates declined with increasing salinity and reached 0.0% in seawater. In scanning electron microscope images, W-SWCNTs, CNF, CCNF and CNC were adsorbed densely over the egg chorion surface; however, because of chitin's biologically harmless properties, only W-SWCNTs had toxic effects on the medaka eggs. No toxicity was observed from N-SWCNT and PEG-SWCNT exposure. We demonstrated that water dispersibility, surface chemistry, biomedical properties and salinity were important factors in assessing the aquatic toxicity of nanomaterials. Copyright © 2016 John Wiley & Sons, Ltd.

Chitin (β-(1-4)-poly-N-acetyl-D-glucosamine) is widely distributed in nature. A method for the preparation of chitin nanofibers (CNFs) is reported. CNFs are considered to have several potential applications because they have useful properties such as high specific surface area and porosity. More recently, beneficial effects of CNF as functional foods were reported. First, the anti-inflammatory effect of oral administration of chitin CNFs was demonstrated in a mouse model of inflammatory bowel disease (IBD). It was found that CNFs improved clinical symptoms and suppressed IBD. CNFs decreased the areas with nuclear factor-κB (NF-κB) staining in colon tissue. Second, the anti-obesity effects of surface-deacetylated chitin nanofibers (SDACNF) in a mouse model of high-fat diet-induced obesity was evaluated. SDACNFs suppressed the increase in body weight produced by the high-fat diet; however, CNFs did not suppress such weight gain. SDACNFs decreased serum levels of leptin. These results suggest that CNF and SDACNF are promising functional foods for patients with IBD or obesity.

Chitin, an N-acetylglucosamine polymer, is well-known to have unique biological functions, such as growth promotion and disease resistance induction in plants. Chitin has been expectedly used for improving crop yield using its functions, however, chitin derivatives, such as chitin oligosaccharide (CO) and chitosan, are widely used instead since chitin is difficult to handle because of its insolubility. Chitin nanofiber (CNF), produced from chitin through nanofibrillation, retains its polymeric structure and can be dispersed uniformly even in water. Here, the effects of CO and CNF on plant responses were directly compared in soybeans (Glycine max) to define the most effective method to produce chitin derivatives for plant response induction. The growth promotion of aerial parts was observed only in CNF-treated plants. The transcriptome analysis showed that the number of differentially expressed genes (DEGs) in CNF-treated soybeans was higher than in CO-treated soybeans. Notably, the expression patterns of DEGs were mostly similar but were strongly induced by CNF treatment as compared with the CO group. These results reveal that CNF can induce stronger plant response to chitin than CO in soybeans, suggesting nanofibrillation, rather than oligomerization, as a more effective method to produce chitin derivatives for plant response induction.

Surface modified chitin nanofibers (SMCNFs) were easily prepared by reacting chitin powder with dodecenyl succinic anhydride (DDSA) and mechanical treatment. The resulted SMCNFs were homogenously dispersed in a series of organic solvents since more hydrophobic group was introduced on the surface of chitin nanofibers. Poly (methyl methacrylate) (PMMA)/SMCNFs nanocomposite films were prepared by simple solution casting method. The homogenous dispersion of the SMCNFs in the PMMA matrix was facilitated, due to the presence of hydrogen bonding and hydrophobic interactions between the nanofillers and the PMMA matrix. Thus, PMMA/SMCNFs nanocomposite films shown high optical transparency, which were nearly the same as the transmittance of the neat PMMA film. Tensile testing results revealed that, inclusion of SMCNFs in the PMMA matrix yielding a more fracture strain and tougher films than the neat PMMA film. Thermal analysis of the neat PMMA and nanocomposite films demonstrated that, the thermal stability of PMMA was significantly enhanced upon inclusion of SMCNFs. The remarkable reinforcement effect of SMCNFs in enhancing the mechanical and thermal properties of PMMA without altering its transparency was resulted from their crystallinity, high aspect ratio, and homogenous dispersibility in the DMF solvent and PMMA polymer matrix.

Chitin, a polymer of N‑acetyl‑d‑glucosamine, is a beneficial material for agriculture because it enhances plant growth and disease control. Although chitin utilization is limited by handling difficulties, chitin nanofiber (CNF) can be more feasibly used since it behaves as a water-soluble material. To broaden the utilization of chitin, protein/CaCO3/chitin nanofiber (P/Ca/CNF) and protein/chitin nanofiber (P/CNF) complexes were prepared from crab shells without using environmentally hazardous chemical in chitin purification processes. Chitin was disintegrated into nanofibers by grinder pretreatment and the subsequent use of a high-pressure water jet system. The nanofibrillation degree depended on the number of mechanical treatments applied. The addition of CNFs to soil slightly enhanced tomato growth relative to that of CNF-untreated or crushed crab shell-treated plants. Furthermore, CNFs treatment reduced the incidence of Fusarium wilt disease in tomato plants. Disease inhibition by P/Ca/CNF and P/CNF was more effective than that by crushed crab shells, and comparable to that by pure CNF. There was no significant relationship between disease reduction level and nanofibrillation degree. In conclusion, P/Ca/CNF prepared with the minimal number of steps was sufficiently able to inhibit Fusarium wilt disease in tomato, and could thus be an eco-friendly material to control plant diseases in sustainable agriculture.

Chitins obtained by fermentation of shrimp wastes using Lactobacillus brevis with and without further inoculations with Rhizopus oligosporus resulted in higher molecular weight than the commercial biopolymer. After grinding in acidic conditions, the attained chitins were fully fibrillated by a mechanical treatment throughout ten passes in a high-pressure water jet system as evidenced by field-emission scanning electron microscopy. The chitin sample crystallinities decreased from 85% to 68%. A previous chitin sample bleaching, as well as the sonication of chitin nanofiber suspensions, enhanced the transparency in the resulting nanofiber sheets. Suspensions and sheets of chitin extracted by L. brevis with successive R. oligosporus inoculations displayed higher transmittance and acetylation degree, as well as improved mechanical properties compared to chitin extracted with only L. brevis. Mechanical studies demonstrated that Young's modulus of the nanofibers using this biological chitin was remarkably higher than that for the commercial product, an important characteristic in polymer reinforcements.

We previously reported a chitin nanofiber hydrogel from squid pen β-chitin by a simple NaOH treatment. In the present study, a calcium phosphate/chitin nanofiber hydrogel was prepared for bone tissue engineering. Calcium phosphate was mineralized on the hydrogel by incubation in a solution of diammonium hydrogen phosphate solution followed by calcium nitrate tetrahydrate. X-ray diffractometry and Fourier transform infrared spectroscopy showed the formation of calcium phosphate crystals. The morphology of the calcium phosphate crystals changed depending on the calcification time. After mineralization, the mechanical properties of the hydrogel improved due to the reinforcement effect of calcium phosphate crystal. In an animal experiment, calcium phosphate/chitin nanofiber hydrogel accelerated mineralization in subcutaneous tissues. Morphological osteoblasts were observed.

Chitosan produced by the deacetylation of chitin is a cationic polymer with antimicrobial properties. In this study, we demonstrate the improvement of chitosan properties by nanofibrillation. Nanofiber sheets were prepared from nanofibrillated chitosan under neutral conditions. The Young’s modulus and tensile strength of the chitosan NF sheets were higher than those of the chitosan sheets prepared from dissolving chitosan in acetic acid. The chitosan NF sheets showed strong mycelial growth inhibition against dermatophytes Microsporum and Trichophyton. Moreover, the chitosan NF sheets exhibited resistance to degradation by the fungi, suggesting potentials long-lasting usage. In addition, surface-deacetylated chitin nanofiber (SDCNF) sheets were prepared. The SDCNF sheet had a high Young’s modulus and tensile strength and showed antifungal activity to dermatophytes. These data indicate that nanofibrillation improved the properties of chitosan. Thus, chitosan NF and SDCNF sheets are useful candidates for antimicrobial materials.

Silver nanoparticles were prepared on chitin nanofiber surfaces by UV light reduction of silver ions. The chitin nanofibers could be efficient substrates to immobilize silver nanoparticles with stable dispersion states. The dispersion and the nanocomposite film with acrylic resin showed characteristic absorption property in the visible light region due to the effect of the silver nanoparticles. Silver nanoparticles endowed strong antifungal activity to chitin nanofibers.

Chitosan nanofibers were easily prepared from fully deacetylated chitosan dry powder using a high-pressure waterjet system. From SEM observation, after 10 cycles of treatment, most of the chitosan had been reduced to homogeneous nanofibers measuring tens of nanometers. On the other hand, further mechanical treatment did not show a significant change. Relative crystallinity of chitosan nanofibers gradually decreased as the number of passes increased since high-pressure waterjet treatment damaged the crystalline region of chitosan nanofibers. The transmittance of the chitosan nanofiber slurry increased steeply, as the number of passes increased, indicating that the chitosan fibers were disintegrated effectively. Viscosity of chitosan nanofiber slurry also showed that the chitosan disintegrated well into nanofibers up to 10 passes. Above 10 passes, disintegration efficiency was saturated. The molecular weights of the nanofibers steeply decreased due to the depolymerization of chitosan by mechanical disintegration. The Young's modulus and tensile strength of chitosan nanofiber sheets were improved as the number of treatments increased, but further treatments deteriorated the tensile strength.

N-halamine chitin nanofiber (NF) film was prepared by the reaction of chitin NF film with sodium hypochlorite solution to endow the film with antibacterial and antifungal activities. The amount of active chlorine content loaded on the chitin NF film depended on the sodium hypochlorite concentration and reaction time. FT-IR, UV-vis, XRD, and TG analyses showed that the N-H bond was substituted to the N-Cl bond and that the reaction took place at the chitin NF surface. After chlorination, the characteristic nanochitin morphology was maintained. Although the active chlorine content of the film gradually decreased by disassociation of the N-Cl bond, chlorine was rechargeable into chitin NF by another sodium hypochlorite solution treatment. The chlorinated chitin NF film showed strong efficacies against Gram-negative and -positive bacteria of Escherichia coli and Staphylococcus aureus, respectively. Moreover, the films showed 100% and 80% inhibition of spore germination when faced against Alternaria alternata and Penicillium digitatum fungi, respectively.

Poly(p-phenylene benzobisoxazole) (PBO) nanofibers were prepared from commercially available PBO fiber by a simple downsizing process for the first time. Partial alkaline hydrolysis of the oxazole ring brought ionic functional groups onto the fiber surface, enabling the disintegration of the PBO fiber into nanofibers with the help of an electrostatic repulsive force. The obtained nanofibers, whose average diameter was 24 nm, were characterized by SEM, FT-IR, ζ-potential analysis, XRD, and TGA. They dispersed homogeneously in water due to the surface charges. Filtration allowed a PBO nanofiber sheet to be easily prepared from the homogeneous dispersion in water.

A protein–chitin nanofiber complex was successfully prepared from crab shells by a mechanical treatment after the removal of CaCO3. One step in the conventional series of treatments—i.e., the removal of proteins—was omitted to bring down the production cost of the nanofibers. The obtained protein–chitin nanofibers had uniform width of approximately 20 nm and a high aspect ratio. These characteristics were similar to conventional chitin nanofibers. The optically transparent protein–chitin nanofiber composite was fabricated with acrylic resin. The nanofibers reinforced the acrylic resin film and thereby increased its mechanical properties. Proteins on the chitin nanofiber surface affected the biomineralization of CaCO3 in the crab shell. Mineralization of CaCO3 on the protein–chitin nanofiber was carried out by the gas-diffusion method. Protein molecules on the chitin NFs increased the chances for biomineralization to occur. The protein molecules stabilized the formation of vaterite and inhibited the transformation of vaterite to calcite.

Surface N -maleylation and N -naphthaloylation of chitin nanofiber (NF) were achieved by reaction with maleic and naphthalic anhydrides in water, respectively. Maleyl and naphthaloyl groups were sufficiently introduced to an amino group on a surface-deacetylated chitin NF. The characteristic nanofiber morphology was maintained after maleylation and naphthaloylation. These NFs were homogeneously dispersed in several organic solvents. Especially, naphthaloyl chitin NF was dispersed even in aromatic solvents, owing to the high level of solvation interactions with the naphthaloyl group. The NF dispersions in those aromatic solvents exhibited a dispersive-to-precipitate transition response at approximately 29 °C. Moreover, the naphthaloyl chitin NF dispersion cut harmful ultraviolet light. The maleyl chitin NF formed a self-standing gel after cross-linking polymerization.

We prepared a gel starting from deacetylated chitin nanofibers by utilizing electrostatic interactions with an anionic cyclodextrin, sulfobutyl ether β-cyclodextrin (SBE-β-CyD). Among the various C...

We introduce a simple preparation procedure for aramid nanofibers from Twaron fibers by using a downsizing process. Alkaline hydrolysis pretreatment brings ionic charges on the fiber surface, allowing facile disintegration of Twaron into nanofibers by virtue of the electrostatic repulsive force. Since the nanofibers can be dispersed homogeneously in water, the processability and formability of the polymer were improved. The resulting aramid nanofibers, having a high degree of physical performance, a uniform nanosized morphology, and a high surface-to-volume ratio, will expand the range of novel applications of aramid fibers.

The aim of this study was to evaluate the effects of cellulose nanofibers from Japanese pear (P-CNF) on acute IBD by using a mouse model of this disorder. Furthermore, using this mouse model, we compared the effects between P-CNF and cellulose nanofibers from wood (W-CNF). P-CNF suppressed shortening of the colon length and improved the histological tissue injury in the mice. It also suppressed the activation of nuclear factor-kappa B and fibrosis of the colon, as well as the myeloperoxidase activation of inflammatory cells such as leukocytes. On the other hand, W-CNF did not improve the histological tissue injury, or suppress shortening of the colon length, colon inflammation, and fibrosis in the mice. These results revealed that P-CNF has anti-inflammatory effects in the experimental IBD mouse model. Our results indicate that P-CNF could be a potential source of new dietary fiber for patients with IBD.

Cellulose and chitin exist in nature as highly crystalline nanofibers. Previously, we reported preparing unique hydrogels from cellulose nanofibers by a simple NaOH treatment without use of any specific solvents or cross-linking agents. In the present study, a similar gel preparation was applied to β-chitin nanofibers extracted from purified squid pen powder. The crystal structure of chitin nanofibers was transformed from β-chitin to α-chitin by NaOH(aq) treatment above 30 wt%. The crystal conversion involving the interdigitation among adjacent nanofibers caused the formation of stable hydrogels with a α-chitin nanofiber network. The use of ethanol voided the dissolution during neutralization and enabled preparation of a higher crystalline hydrogel with high mechanical strength. It achieved a Young’s modulus of 16.6 MPa, a tensile strength of 7 MPa and a strain at break of 52.2 %, on average. Finally, we note that the shrinkage of the cellulose I and β-chitin nanofibers in aqueous NaOH solutions was caused by the release of tensile residual stress due to the intracrystalline swelling in NaOH solutions.

Surface-deacetylated chitin nanofiber reinforced chitosan films were prepared. The nano-composite films were highly transparent of approximately 84% at 600 nm due to the nanometer-sized fillers and chitosan matrix, which were embedded in the cavities and on the rough surface of the nanofiber networks. Due to the extended crystalline structure, the nanofibers worked effectively as reinforcement filler to improve the Young's modulus and the tensile strength of the chitosan film. After 10% blending of nanofiber, these properties were increased by 65% and 94%, respectively. Moreover, thermal expansion was also significantly decreased from 35.3 to 26.1 ppm K(-1) after 10% addition of nanofibers. Surface-deacetylated chitin nanofiber and the nano-composite films showed antifungal activity against A. alternata.

Chitosan nanofibers were easily prepared from dry chitosan powder using the Star Burst system, which employs a high-pressure water jet system. Although the chitosan nanofibers became thinner as the number of Star Burst passes increased, the fiber thickness did not change significantly above 10 passes. Crystallinity and the chitosan nanofiber length decreased after extensive treatment due to the strong collision forces breaking the fibers. The mechanical properties and thermal expansion of the chitosan nanofiber sheets were improved by increasing the number of passes up to 10, but further treatment resulted in a deterioration of these properties.

In this study, we investigated the suppressive effects of cellulose nanofibers made from adlay (A-CNF) and seaweed (S-CNF) on colon inflammation using the mouse model of inflammatory bowel disease (IBD). A-CNF and S-CNF suppressed shortening of the colon length and improved the histological tissue injury in mice. A-CNF and S-CNF also suppressed the activation of nuclear factor-kappa B in the colon. Furthermore, A-CNF and S-CNF suppressed the myeloperoxidase activities of inflammatory cells such as leukocytes. On the other hand, cellulose nanofibers made from wood did not improve the histological tissue injury or suppress the shortening of the colon length and colon inflammation in mice. These results revealed that A-CNF and S-CNF have suppressive effects on colon inflammation in an experimental IBD mouse model. Furthermore, our results indicate that A-CNF and S-CNF may be a potential source of dietary fiber for patients with IBD.

Polylactic acid (PLA) reinforced with chitin nanofibers was produced from a mixture of a colloidal suspension of PLA particles with chitin nanofiber suspension. The dispersion medium was solely water, which was removed by filtration and drying. Nanocomposites were obtained by compression molding of the filtrates. Static tensile test and dynamic mechanical analysis were performed to evaluate the reinforcement as a function of nanofiber content. Chitin nanofibers delivered reinforcement similar to cellulose nanofibers, being especially effective at up to 70 wt% fiber load. The ultimate tensile modulus and strength reached 7.7 GPa and 110 MPa, respectively, at a nanofiber content of 70 wt%.

A protein/CaCO3/chitin nanofiber complex was prepared from crab shells by a simple mechanical treatment with a high-pressure water-jet (HPWJ) system. The preparation process did not involve chemical treatments, such as removal of protein and calcium carbonate with sodium hydroxide and hydrochloric acid, respectively. Thus, it was economically and environmentally friendly. The nanofibers obtained had uniform width and dispersed homogeneously in water. Nanofibers were characterized in morphology, transparency, and viscosity. Results indicated that the shell was mostly disintegrated into nanofibers at above five cycles of the HPWJ system. The chemical structure of the nanofiber was maintained even after extensive mechanical treatments. Subsequently, the nanofiber complex was found to improve the growth of tomatoes in a hydroponics system, suggesting the mechanical treatments efficiently released minerals into the system. The homogeneous dispersion of the nanofiber complex enabled easier application as a fertilizer compared to the crab shell flakes.

Esterification with maleic anhydride significantly improved the mechanical disintegration of chitin into uniform 10-nm nanofibers. Nanofibers with 0.25 ° of esterification were homogeneously dispersed in basic water due to the carboxylate salt on the surface. Esterification proceeded on the surface and did not affect the relative crystallinity. A cast film of the esterified chitin nanofibers was highly transparent, since the film was free from light scattering.

Chitin nanofibers (CNFs) processed from second most abundant biomolecule chitin were loaded with gold metallic nanoparticles (Au NPs) to obtained hybrid organic-inorganic composite which was molded in different forms dispersion, flakes, powder, and transparent thin film. First pre-organized Au NPs were prepared in soluble triblock copolymer poly (methyl vinyl ether) (PMVE) by reduction of gold precursor salt (HAuCl43H2O) by NaBH4 then NPs were mixed with diluted CNFs suspension to obtain CNFs-Au NPs composite. CNFs of width 25 - 40 nm were prepared by combination of chemical and mechanical processing in wet acidic condition from 1 wt% crab shell chitin slurry. When polymer stabilized Au NPs blended with CNF suspension, all Au NPs and 56% polymer were found mass transferred from water phase to entangle with more polar moieties of chitin. Composite’s suspension and compressed dried film were characterized by recording digital images, UV-vis, TEM, SEM, and XRD spectroscopies. When 70 m thin non transparent composite film was impregnated with tricyclodecane dimethanol dimethacrylate (TCDDMA) resin and subsequent polymerized with photoinitiator 2-hydroxy-2-methylpropiophenone, the film became transparent due to filling of nanosized CNFs in the cages of the resin.

Chitin nanofibers were isolated from the cell walls of five different types of mushrooms by the removal of glucans, minerals, and proteins, followed by a simple grinding treatment under acidic conditions. The Chitin nanofibers thus obtained have a uniform structure and a long fiber length. The width of the nanofibers depended on the type of mushrooms and varied in the range 20 to 28 nm. The Chitin nanofibers were characterized by elemental analyses, FT-IR spectra, and X-ray diffraction profiles. The results showed that the α-chitin crystal structure was maintained and glucans remained on the nanofiber surface.

This paper demonstrates the preparation of chitin nanofibers from crab shells using a simple mechanical treatment. The nanofibers are small enough to retain the transparency of neat acrylic resin. Possessing hydroxyl and amine/N-acetyl functionalities, water suspension of chitin nanofibers was vacuum-filtered 9 times faster than cellulose nanofibers to prepare a nanofiber sheet of 90 mm in diameter. This is a prominent advantage of chitin nanofibers over cellulose nanofibers in terms of commercial application. Interestingly, chitin acrylic resin films exhibited much higher transparency than cellulose acrylic resin films owing to the close affinity between less hydrophilic chitin and hydrophobic resin. Furthermore, the incorporation of chitin nanofibers contributes to the significant improvement of the thermal expansion and mechanical properties of the neat acrylic resin. The properties of high light transmittance and low thermal expansion make chitin nanocomposites promising candidates for the substrate in a continuous roll-to-roll process in the manufacturing of various optoelectronic devices such as flat panel displays, bendable displays, and solar cells.