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Most of the series of nanochitins have been produced by the break-down process. In this study, chitin nanoparticles were prepared by a bottom-up process. Chitin was treated with sodium hydroxide to obtain an alkaline chitin aqueous solution. The alkaline chitin was regenerated by neutralization and then vigorously stirred to obtain chitin nanoparticles. The average particle size of the chitin nanoparticles was 7 nm. The individual particles were stably dispersed in water. Chitin nanoparticles had lower crystallinity than the raw material chitin and the surface of the chitin nanoparticles regenerated in water were presumed to be hydrophilic. The low crystallinity and the high hydrophilicity of the surface contributed to the high dispersibility of the chitin nanoparticles in water. Chitin nanoparticles had higher heat resistance than the raw material chitin, suggesting a large change in the higher-order structure associated with dissolution and subsequent regeneration of chitin. Since chitin nanoparticles interact with each other less than chitin nanofibers produced by mechanical treatment, the viscosity of nanoparticles was smaller than that of nanofibers. Therefore, it can be prepared at a high concentration. In addition, the chitin nanoparticles can be easily redispersed in water after being concentrated by centrifugation.

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.

Oriented chitosan films, prepared by elongation, are applied to a surface wrinkling system via a horseradish peroxidase-catalyzed surface reaction of ferulic acid and drying. The wrinkle morphologi...

Chitin, an N-acetyl-D-glucosamine polymer, has been known to enhance plant growth. However, this polysaccharide has not been used extensively in experimental work or agriculture practices because its hydrophobic nature makes it difficult to handle. Chitin nanofiber (CNF), which disperses well in water, can feasibly be used to evaluate the effect of chitin on the promotion of plant growth. In this study, we analysed the contents of inorganic elements and global gene expression to obtain an overview of the growth-promoting action of chitins in plants. Significant increases in the biomass of aerial parts and concentration of chlorophyll following treatment with CNF or short-chain chitin oligomers were observed in tomatoes that were hydroponically cultivated under ultralow nutrient concentrations. The results of the quantification of inorganic elements demonstrated that concentrations of nitrogen and carbon significantly increased in whole tomato plant under chitin treatment. Transcriptome analysis of CNF-treated tomatoes by RNA sequencing showed that the expression levels of genes related to nitrogen acquisition and assimilation, nutrient allocation and photosynthesis were altered. These results indicate that the growth-promoting action of chitin treatment is caused by an improvement in nitrogen uptake efficiency and that CNF could be a useful material for nutrient management in tomato production.

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.

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.

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.

Honeycomb-like porous chitosan (CS) films are attractive tools for developing functional materials for filters, catalyses, adsorbents, biomaterials, etc. A simple method for fabricating honeycomb-like porous CS films without special reagents, facilities, and techniques would make them accessible. Here we introduce an easily available method for fabricating honeycomb-like CS films without a strong acid/base, toxic reagents, or special facilities/techniques. An aqueous solution containing CS and poly(N-isopropylacrylamide) (PNIPAm) was allowed to stand at 25 °C to evaporate water. After 3 days, CS–PNIPAm composite films with homogenously phase-separated PNIPAm particles were obtained. The PNIPAm particles were removed by immersion in methanol, and the resulting films dried under reduced pressure to become honeycomb-like porous CS films. The pore size could be varied in the range of 0.5–3.0 μm by altering the CS concentration and the molecular weight of CS where the pore size was reduced under conditions with stronger interaction between CS molecules. We reveal that the key to success with this system is the decrease of lower critical solution temperature (LCST) of PNIPAm with water evaporation. In addition, we confirmed the removed PNIPAm was recyclable in this system. Furthermore, we found this method was also applicable to alginate. The proposed facile method for fabricating honeycomb-like porous polymeric films could provide various functional porous materials.

In this study, the effects of chitosan and surface-deacetylated chitin nanofibrils (SDACNFs) on hair growth were evaluated. In human follicle dermal papilla cells in vitro, chitosan and SDACNFs were shown to increase cell growth on day 3 after the initiation of treatment, together with an increase in the production of fibroblast growth factor-7 (FGF-7) by these cells on day 3. Furthermore, in an in vivo study in mice, chitosan and SDACNF application promoted hair growth. The number of anagen follicles significantly increased compared with that in the control group, whereas the number of telogen follicles significantly decreased in the chitosan and SDACNF groups. In the chitosan and SDACNFs groups, moreover, the expression levels of FGF-7 and Sonic hedgehog were significantly upregulated in hair follicles. Overall, our results demonstrated that chitosan and SDACNFs promoted hair growth and therefore may have applications as novel therapeutic agents for the treatment of hair loss in patients.

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.

Crickets are gaining worldwide attention as a nutrient source with a low environmental impact. We considered crickets as a new source of chitin raw material. Chitin isolated from crickets was successfully converted to nanochitin by pulverization. First, chitin was obtained from cricket powder in a 2.6% yield through a series of chemical treatments. Chitin identification was confirmed by FT-IR and 13C NMR. The chitin had an α-type crystal structure and a deacetylation degree of 12%. Next, it was pulverized in a disk mill to obtain nanochitin. Cricket nanochitin was of a whisker shape, with an average fiber width of 10.1 nm. It was larger than that of crab shells, while the hydrodynamic diameter and crystal size were smaller. Such differences in shape affected the physical properties of the dispersion. The transmittance was higher than that of crab nanochitin due to the size effect, and the viscosity was smaller. Moreover, the dry non-woven cricket nanochitin sheets were more densely packed, and their modulus and breaking strength were greater.

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.

The development of anion sensors for selective detection of a specific anion is a crucial research topic. We previously reported a selective photo-induced colorimetric reaction of 1-methyl-3-(N-(1,8-naphthalimidyl)ethyl)imidazolium (MNEI) having a cationic receptor in the presence of molecules having multiple carboxy groups, such as succinate, citrate, and polyacrylate. However, the mechanism underlying this reaction was not clarified. Here, we investigate the photo-induced colorimetric reaction of N-[2-(trimethylammonium)ethyl]-1,8-naphthalimide (TENI), which has a different cationic receptor from MNEI and undergoes the photo-induced colorimetric reaction, and its analogues to clarify the reaction mechanism. The TENI analogues having substituents on the naphthalene ring provide important evidence, suggesting that the colorimetric chemical species were radical anions generated via photo-induced electron transfer from carboxylate to the naphthalimide derivative. The generation of the naphthalimide-based radical anion is verified by 1H NMR and cyclic voltammetry analyses, and photo-reduction of methylene blue is mediated by TENI. In addition, the role of the cationic receptor for the photo-induced colorimetric reaction is investigated with TENI analogues having different hydrophilic groups instead of the trimethylammonium group. Interestingly, the photo-induced colorimetric reaction is observed in a nonionic analogue having a polyethylene glycol group, indicating that the colorimetric reaction does not require a cationic receptor. On the other hand, we reveal that the trimethylammonium group stabilizes the radical anion species. These generation and stabilization phenomena of naphthalimide-based radical anion species will contribute to the development of sophisticated detection systems specific for carboxylate.

Chitin nanofiber is a nanomaterial produced by pulverizing chitin, the main component of crab shells. Since it has excellent mechanical properties, it is expected to be used as a reinforcing material to strengthen materials. Chitin was mechanically ground in water using a ball mill to prepare nanofibers. The ball size, total ball weight, and milling time were varied, and the resulting water dispersion and the cast film were analyzed to optimize the conditions for efficient preparation. The length and width of the nanofibers were also measured by SEM and AFM observations. The size of the balls affected the level of grinding and the intensity of impact energy on the chitin. The most efficient crushing was achieved when the diameter was 1 mm. The total ball weight directly affects the milling frequency, and milling proceeds as the total weight increases. However, if too many balls occupy the container, the grinding efficiency decreases. Therefore, a total ball weight of 300 g was optimal. Regarding the milling time, the chitin becomes finer depending on the increase of that time. However, after a specific time, the shape did not change much. Therefore, a milling time of approximately 150 min was appropriate.

Surface wrinkling to fabricate hierarchical surface topographies has attracted much attention because of the potential and multifunctional applications of hierarchical surface wrinkles beyond uniform wrinkles. Although many reports have described the preparation of hierarchical wrinkles induced by mechanical stress and heat, fabrication through drying-induced shrinkage has hardly been reported. Here we introduce hierarchical surface wrinkles and bumps generated on a chitosan film via the preparation of double-skin layers with κ- and ι-carrageenans, respectively, and subsequent drying. Double-skin layers are fabricated on a swollen chitosan film, called a chitosan hydrogel film, that is soaked first in κ- or ι-carrageenan solution and then in water to remove excess adsorbed κ- or ι-carrageenan. After the film is dried, hierarchical microscopic surface architectures are observed. In the case of the κ-carrageenan system, the wrinkles are hierarchical, consisting of wrinkles (6.2 ± 2.8 μm) that have smaller buckles (0.23 ± 0.09 μm). We reveal that the wrinkles or the smaller buckles are caused by plane inhomogeneous shrinkage between the κ-carrageenan layer and the chitosan film or by the aggregation of the κ-carrageenan layer upon drying, respectively. Interestingly, the ι-carrageenan system showed hierarchical bumps consisting of semispherical bumps (5.6 ± 2.1 μm) that have smaller bumps (0.78 ± 0.27 μm). We reveal that the larger bumps are generated during the immersion of the chitosan hydrogel film into ι-carrageenan solution. The smaller bumps are generated by the aggregation of the ι-carrageenan layer that occurs during drying; this process requires the plane compression strain caused by the shrinkage of the chitosan hydrogel film.

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.

Nonalcoholic steatohepatitis (NASH), a more advanced form of nonalcoholic fatty liver disease (NAFLD), is associated with increased cardiovascular and liver-related mortality. Stroke-prone spontaneously hypertensive rats (SHRSP5/Dmcr) that are fed a high-fat and high-cholesterol diet develop hepatic lesions that are similar to those observed in human NASH pathology. We investigated the hepatic protective and antioxidant effects of surface-deacetylated chitin nanofibers (SDACNFs) that were administered to SHRSP5/Dmcr rats for 8 weeks. The administration of SDACNFs (80 mg/kg/day) resulted in a significant decrease in hepatic injury, oxidative stress, compared with the non-treatment. The SDACNFs also caused a reduction in the population of harmful members of the Morganella and Prevotella genus, and increased the abundance of the Blautia genus, a useful bacterium in gut microbiota. We therefore conclude that SDACNF exerts anti-hepatic and antioxidative effects not only by adsorbing lipid substances but also by reforming the community of intestinal microflora in the intestinal tract.

Background/Aim: Chitosan-coated iron oxide nanoparticles (Chi-NP) have gained attention because of their biocompatibility, biodegradability, low toxicity and targetability under magnetic field. In this study, we investigated various biological properties of Chi-NP. Materials and Methods: Chi-NP was prepared by mixing magnetic NP with chitosan FL-80. Particle size was determined by scanning and transmission electron microscopes, cell viability by MTT assay, cell cycle distribution by cell sorter, synergism with anticancer drugs by combination index, PGE(2) production in human gingival fibroblast was assayed by ELISA. Results: The synthetic process of Chi-NP from FL-80 and magnetic NP increased the affinity to cells, up to the level attained by nanofibers. Upon contact with the culture medium, Chi-NP instantly formed aggregates and interfered with intracellular uptake. Aggregated Chi-NP did not show cytotoxicity, synergism with anticancer drugs, induce apoptosis (accumulation of subG1 cell population), protect the cells from X-ray-induced damage, nor affected both basal and IL-1β-induced PGE(2) production. Conclusion: Chi-NP is biologically inert and shows high affinity to cells, further confirming its superiority as a scaffold for drug delivery.

1-Methyl-3-(N-(1,8-naphthalimidyl)ethyl)imidazolium can be a discriminator for anionic polysaccharides via monomer-excimer switching and photo-induced colorimetric reaction. In the system, the exci...

To fabricate robust nanofibrillated cellulose (NFC) hydro/aerogels, benign solution/solvent exchange treatment was developed by adding five different water miscible solutions/solvents into a NFC aqueous suspension. The NFC self-aggregated and formed self-standing gels during the solution/solvent exchange treatment. After a further exchange of solution/solvent inside the gels with water by a thorough water washing followed by freeze-drying, NFC hydrogels and aerogels were obtained. The NaOH-hydrogel demonstrated a decent rheology with a storage modulus of 36.4 kPa and a satisfactory mechanical property with a compressive modulus of 37.6 kPa. On the contrary, the acetone-hydrogel was weak due to disaggregation. The NFC aerogels were lightweight and had a characteristic porous structure. The packing density and structure varied among aerogels with different solution/solvent treatments. The NaOH-aerogel had a 2D sheet-like structure with densely packed micrometer-sized pores uniformly distributed within the a...

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.

We previously developed bio-based wrinkled surfaces induced by wood-mimetic skins upon drying in which microscopic wrinkles were fabricated on a chitosan (CS) film by immersing it in a phenolic acid solution, followed by horseradish peroxidase (HRP)-catalyzed surface reaction and drying. However, the detailed structure of the resulting wood-mimetic skins, including crosslinking mode and thickness, has not been clarified due to the difficulty of the analysis. Here, we prepare wrinkled films using ferulic acid (FE), vanillic acid (VA), and homovanillic acid (HO) and characterize their structures to clarify the unknown characteristics of wood-mimetic skin. Chemical and structural analyses of wood-mimetic skins prepared using VA and HO indicate that the crosslinking structure in the skin is composed of ionic bonds between CS and an oligophenolic residue generated by the HRP-catalyzed reaction on the CS surface. Moreover, the quantity of these ionic bonds is related to the skin hardness and wrinkle size. Finally, SEM and TOF-SIMS analyses indicate that the skin thickness is on the submicron order (

Surface-deacetylated chitin nanofibers (SDACNFs) reinforced with a sulfobutyl ether β-cyclodextrin (SBE-β-CD) (NFs-CDs) gel were developed to obtain a controlled release carrier of prednisolone (PD) for the treatment of colitis. PD was released slowly from the gel at both pH 1.2 and 6.8. The in vitro slow release of PD from the NFs-CDs gel was reflected in the in vivo absorption of the drug after oral administration to rats. These results suggest that a simple gel composed of a mixture of SDACNFs and SBE-β-CD has the potential for use in the controlled release of PD. We also evaluated the therapeutic effects of the NFs-CDs gel containing PD on dextran sulfate sodium (DSS)-induced colitis model mice. The administration of the NFs-CDs gel at intervals of 3days from the beginning of the DSS treatment resulted in a significant improvement, not only in colitis symptoms but also histopathological changes in colon tissue. In addition, the therapeutic effects of the NFs-CDs gel on colitis can be attributed to decreased levels of neutrophil infiltration and the development of oxidative stress. These efficacy profiles of the NFs-CDs gel containing PD suggest that it has the potential for use in the treatment of, not only colitis, but also a variety of other disorders associated with inflammation and oxidative injuries.

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 deproteinization is a major constraint for chitin recovery from crustacean wastes. In this work, high protein removal was achieved through the combination of two-stage solid state culture by Lactobacillus brevis and Rhizopus oligosporus . The first stage was carried out employing a heterofermentative starter ( L. brevis ) using glucose as sole carbon source. For the second stage, the inoculum levels of the food grade fungi were 10 3 , 10 5 or 10 7 spores/ml. The highest deproteinization (96% ± 0.43%) and demineralization (66.45 ± 2.14%) were achieved with 10 7 spores/ml. The protein removal was attributed to acid and neutral proteolytic activities, which highest activity during culture was determined at pH 5. Lactic acid was the main organic acid produced along with acetic, succinic and oxalic acids. The released protein hydrolysates (120.56 mg protein/g) displayed M W range between 25 × 10 3 and 11 × 10 3 Da. The highest concentration of astaxanthin extracted from liquid was 8.78 μg/g. Protein hydrolysates and astaxanthin showed radical scavenging activity with I C50 of 1.13 ± 0.03 mg/g and 2.02 ± 0.01 μg/g, respectively. The purified chitin presented molecular weight of 1313 × 10 3 Da, preserving high crystalline index (I CR of 87.5%) and 93.67% degree of acetylation.

In this study, we report that surface-deacetylated chitin nano-fibers (SDACNFs) are more effective in decreasing renal injury and oxidative stress than deacetylated chitin powder (DAC) in 5/6 nephrectomized rats. An oral administration of low doses of SDACNFs (40mg/kg/day) over a 4 week period resulted in a significant decrease in serum indoxyl sulfate, creatinine and urea nitrogen levels, compared with a similar treatment with DAC or AST-120. The SDACNFs treatment also resulted in an increase in antioxidant potential, compared with that for DAC or AST-120. Immunohistochemical analyses also demonstrated that SDACNFs treated CRF rats showed a decrease in the amount of accumulated 8-OHdG compared with the CRF group. These results suggest that the ingestion of SDCH-NF results in a significant reduction in the levels of pro-oxidants, such as uremic toxins, in the gastrointestinal tract, thereby inhibiting the subsequent development of oxidative stress in the systemic circulation.