Catalytic activity of Cu2O nanoparticles supported on cellulose beads prepared by emulsion-gelation using cellulose/LiBr solution and vegetable oil.

Nanocatalysts tend to aggregate and are difficult to recycle, limiting their practical applications. In this study, an environmentally friendly method was developed to produce cellulose beads for use as supporting materials for Cu-based nanocatalysts. Cellulose beads were synthesized from a water-in-oil emulsion using cellulose dissolved in an LiBr solution as the water phase and vegetable oil as the oil phase. Upon cooling, the gelation of the cellulose solution produced spherical cellulose beads, which were then oxidized to introduce surface carboxyl groups. These beads (diameter: 95-105 µm; specific surface area: 165-225 m2 g-1) have a three-dimensional network of nanofibers (width: 20-30 nm). Furthermore, the Cu2O nanoparticles were loaded onto oxidized cellulose beads before testing their catalytic activity in the reduction of 4-nitrophenol using NaBH4. The apparent reaction rate constant increased with increasing loading of Cu2O nanoparticles and the conversion efficiency was >90 %. The turnover frequency was 376.2 h-1 for the oxidized cellulose beads with the lowest Cu2O loading, indicating a higher catalytic activity compared to those of other Cu-based nanoparticle-loaded materials. In addition to their high catalytic activity, the cellulose beads are reusable and exhibit excellent stability.

Multiscale Porous Carbon Materials by In Situ Growth of Metal-Organic Framework in the Micro-Channel of Delignified Wood for High-Performance Water Purification.

Porous carbon materials are suitable as highly efficient adsorbents for the treatment of organic pollutants in wastewater. In this study, we developed multiscale porous and heteroatom (O, N)-doped activated carbon aerogels (CAs) based on mesoporous zeolitic imidazolate framework-8 (ZIF-8) nanocrystals and wood using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation, in situ synthesis, and carbonization/activation. The surface carboxyl groups in a TEMPO-oxidized wood (TW) can provide considerably large nucleation sites for ZIF-8. Consequently, ZIF-8, with excellent porosity, was successfully loaded into the TW via in situ growth to enhance the specific surface area and enable heteroatom doping. Thereafter, the ZIF-8-loaded TW was subjected to a direct carbonization/activation process, and the obtained activated CA, denoted as ZIF-8/TW-CA, exhibited a highly interconnected porous structure containing multiscale (micro, meso, and macro) pores. Additionally, the resultant ZIF-8/TW-CA exhibited a low density, high specific surface area, and excellent organic dye adsorption capacity of 56.0 mg cm-3, 785.8 m2 g-1, and 169.4 mg g-1, respectively. Given its sustainable, scalable, and low-cost wood platform, the proposed high-performance CA is expected to enable the substantial expansion of strategies for environmental protection, energy storage, and catalysis.

Detection of nanoplastics based on surface-enhanced Raman scattering with silver nanowire arrays on regenerated cellulose films.

Plastic pollution has steadily become a global issue due to its ubiquity and degradation into micro and nanoparticles. Herein, we report the construction of surface-enhanced Raman scattering (SERS)-active array substrates with regenerated cellulose (RC) and plasmonic nanoparticles (AuNRs and AgNWs) via a simple vacuum-assisted filtration method using a silicon mask for rapid nanoplastic detection. The AgNWs/RC film exhibited a SERS intensity of crystal violet approximately six times higher than that of the AuNRs/RC film with a high enhancement factor of 1.8 × 107. Moreover, the AgNWs/RC film exhibits a better SERS activity for polystyrene nanoplastic detection than the AuNRs/RC film because the dense AgNW network structures are well suited for nanoplastic detection. The AgNWs/RC film can detect PS nanoplastics down to 0.1 mg/mL with a good reproducibility of the SERS signal. The low-cost, flexible, and highly sensitive AgNWs/RC films could provide an efficient and rapid SERS-based method for nanoplastic detection.

Double-crosslinked cellulose nanofiber based bioplastic films for practical applications.

While green bioplastic based on carbohydrate polymers have showed considerable promise, the methods typically used to prepare them in a single material have remained a significant challenge. In this study, a simple approach is proposed to fabricate high performance cellulose films composed of chemically and physically dual-crosslinked 2,2,6,6-tetramethylpiperidine-1-oxy-oxidized cellulose nanofibers (DC TEMPO-CNFs). The hydroxyl groups of TEMPO-CNF suspensions were firstly crosslinked chemically with epichlorohydrin (ECH), and subsequently TEMPO-CNF matrices were crosslinked physically via the strong electrostatic interaction between carboxylate and Ca2+ ions. It was found that the optimized DC TEMPO-CNF films exhibit a good transmittance (90 %) and a high tensile strength (303 MPa). Furthermore, these DC TEMPO-CNF films revealed superior thermal stability and excellent water resistance compared to neat TEMPO-CNF films without crosslinked domains. We believe that these results will pave the way to preparing practical polysaccharide bioplastics with simple, environmentally-friendly manufacturing processes.

Surface-enhanced Raman scattering-active AuNR array cellulose films for multi-hazard detection.

In this study, we report a surface-enhanced Raman scattering (SERS)-active array film, which is based on regenerated cellulose hydrogels and gold nanorods (AuNRs), by combining a silicon rubber mask with a vacuum filtration method. This strategy enables the direct AuNR array formation on hydrogel surface with a precisely controlled number density. Moreover, the control of interparticle nanogap has been realized by the spatial deformation of hydrogels. A decrease in gaps between AuNRs deposited on hydrogels can result in SERS enhancement because 3D porous hydrogel structures turned into 2D closely packed hydrogel films during drying. In our experiments, SERS sensor arrays show excellent SERS activity to detect rhodamine 6 G and thiram down to 10 pM and 100 fM with competitive enhancement factors of 3.9 × 108 and 9.5 × 109, respectively. Importantly, the resultant SERS-active arrays with nine sensor units can efficiently detect nine different analytes on a single substrates at a time. Moreover, we demonstrate that physical bending has little effect on the SERS activity of flexible AuNR array hydrogel films, which indicates the high reproducibility of SERS measurement. This SERS array film has great potential to simultaneously detect multiple hazards for the practical application of SERS analysis.

In Vitro Synthesis of Branchless Linear (1 → 6)-α-d-Glucan by Glucosyltransferase K: Mechanical and Swelling Properties of Its Hydrogels Crosslinked with Diglycidyl Ethers.

A hydrogel was prepared from a polysaccharide, enzymatically synthesized through a one-pot reaction in aqueous solution, and its properties as a functional material were evaluated. Enzymatic synthesis using glucosyltransferase K obtained from Streptococcus salivarius ATCC 25975 was performed with sucrose as a substrate. The synthetic product was unbranched linear (1 → 6)-α-d-glucan with a high molecular weight, M w: 1.0-3.0 × 105. The synthesized (1 → 6)-α-d-glucan was insoluble in water and crystallized in a monoclinic unit cell, which is consistent with the hydrated form of dextran. Transparent and highly swellable (1 → 6)-α-d-glucan hydrogels were obtained by crosslinking with diglycidyl ethers. The hydrogels showed no syneresis and no volume change during compression, resulting in the retention of shape under repeated compression. The elastic moduli of these hydrogels (<60 kPa) are smaller than those of other polysaccharide-based hydrogels having the same solid contents. The oven-dried gels could be restored to the hydrogel state with the original transparency and a recovery ratio greater than 98%. The mechanism of water diffusion into the hydrogel was investigated using the kinetic equation of Peppas. The properties of the hydrogel are impressive relative to those of other polysaccharide-based hydrogels, suggesting its potential as a functional biomaterial.

Cellulose nanocrystal-coated TEMPO-oxidized cellulose nanofiber films for high performance all-cellulose nanocomposites.

High performance biopolymer films are of great interest as effective alternatives to non-biodegradable and petroleum-based polymer films. However, most natural biopolymer films possess weak mechanical and poor gas barrier properties, limiting their applicability. In this work, we developed all-cellulose nanocomposite films through a simple vacuum filtration process, using cellulose nanocrystals (CNCs) and 2,2,6,6-tetramethylpiperidine-1-oxy-oxidized cellulose nanofibers (TEMPO-CNFs). The TEMPO-CNFs were employed to construct a transparent, free-standing substrate matrix and the CNCs were used as a coating material to improve the mechanical and water vapor barrier properties of the final material. We have demonstrated that the top and bottom CNCs-coated TEMPO-CNF substrates (CNC/TEMPO-CNF/CNC) have excellent mechanical and good water vapor barrier properties. The resulting CNC/TEMPO-CNF/CNC films revealed a high tensile strength of 114 MPa and a low specific water vapor transmission rate (SWVTR) of 19 g∙mm/m2∙day. In addition, the CNC/TEMPO-CNF/CNC films were resistant to various solvents including water, ethanol, tetrahydrofuran (THF), and acetone. This type of high performance cellulose nanocomposite can be used as a renewable material for a broad range of potential applications.

Cationic hydrogels prepared from regioselectively azidated (1→3)-α-d-glucan via crosslinking and amination: Physical and adsorption properties.

Cationic hydrogels with amino groups were successfully prepared using (1→3)-α-d-glucan synthesized by glucosyltransferase J (GtfJ) cloned from Streptococcus salivarius through a three-step reaction: (i) Azido groups were regioselectively introduced at the C6 position of (1→3)-α-d-glucan by a bromination-azidation process (degree of substitution 0.94), (ii) Azido groups were partially crosslinked with 1,8-nonadiyne via a copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction, (iii) Azido groups that were unused for crosslinking were reduced to amino groups by sodium borohydride (NaBH4). The introduction of amino groups was confirmed quantitatively and qualitatively by elemental, Fourier transform infrared (FT-IR), and nuclear magnetic resonance (NMR) analyses. These cationic hydrogels showed a specific adsorption ability for bovine serum albumin (BSA) over a wide pH range of 4.5-8.0 due to their high pH values at the point of zero charge (pHpzc 8.80-8.92).

Highly swellable hydrogel of regioselectively aminated (1→3)-α-d-glucan crosslinked with ethylene glycol diglycidyl ether.

(1→3)-α-d-glucan synthesized by glucosyltransferase J (GtfJ) cloned from Streptococcus salivarius was regioselectively aminated as 6-amino-6-deoxy-(1→3)-α-d-glucan (aminoglucan) through three steps: bromination, azidation, and reduction. The degree of substitution of the amino group was determined by elemental analysis to be 0.97 and the molecular weight was 3.74×104 as measured by size exclusion chromatography. The regioselective amination at the C6 position of every pyranose ring was confirmed by 1H/13C NMR and solid state 15N cross polarization/magic angle spinning NMR spectroscopy. Aminoglucan was characterized by FT-IR, X-ray diffraction and thermogravimetric analysis. Solubility of aminoglucan in various solvents was investigated and confirmed in aqueous solution at pH ≤ 11. Therefore, aminoglucan was crosslinked with ethylene glycol diglycidyl ether (EGDE) by an epoxy-ring opening reaction under alkaline conditions. The obtained EGDE-crosslinked aminoglucan hydrogels were highly swellable in water owing to a strong water-holding ability and no water was released on compression and breaking of the gels.

In Vivo Bioreactor Using Cellulose Membrane Benefit Engineering Cartilage by Improving the Chondrogenesis and Modulating the Immune Response.

BACKGROUND: To regenerate tissue-engineered cartilage as a source of material for the restoration of cartilage defects, we used a human fetal cartilage progenitor cell pellet to improve chondrogenesis and modulation of the immune response in an in vivo bioreactor (IVB) system. METHODS: IVB was buried subcutaneously in the host and then implanted into a cartilage defect. The IVB was composed of a silicone tube and a cellulose nano pore-sized membrane. First, fetal cartilage progenitor cell pellets were cultured in vitro for 3 days, then cultured in vitro, subcutaneously, and in an IVB for 3 weeks. First, the components and liquidity of IVB fluid were evaluated, then the chondrogenesis and immunogenicity of the pellets were evaluated using gross observation, cell viability assays, histology, biochemical analysis, RT-PCR, and Western blots. Finally, cartilage repair and synovial inflammation were evaluated histologically. RESULTS: The fluid color and transparency of the IVB were similar to synovial fluid (SF) and the components were closer to SF than serum. The IVB system not only promoted the synthesis of cartilage matrix and maintained the cartilage phenotype, it also delayed calcification compared to the subcutaneously implanted pellets. CONCLUSION: The IVB adopted to study cell differentiation was effective in preventing host immune rejection.

Facile preparation of cellulose-SiO2 composite aerogels with high SiO2 contents using a LiBr aqueous solution.

Cellulose-SiO2 composite aerogels (CSGs) with high SiO2 content up to 90% were successfully developed via the mixing of SiO2 particles and a cellulose solution dissolved in a LiBr aqueous solution. The characteristic properties resulting from the direct gelation of a dissolved cellulose solution could facilitate the preparation of a variety of forms of SiO2-embedded gels. The introduction of SiO2 particles reduced the pore sizes while maintaining the three-dimensional porous structure of the regenerated cellulose matrix, resulting in increased density and decreased porosity. CSGs exhibited excellent mechanical properties, large surface areas, and thermal stability up to 250 °C in an air atmosphere. Furthermore, CSGs showed low thermal conductivity ranging from 0.038 to 0.048 W/m K despite the influence of higher density and lower porosity with increased SiO2 contents. These results suggested that CSGs could provide a new option with regard to advanced porous organic-inorganic composite materials.

Highly enhanced adsorption of Congo red onto dialdehyde cellulose-crosslinked cellulose-chitosan foam.

The adsorption of Congo red (CR) was evaluated using cellulose-chitosan foam crosslinked via dialdehyde cellulose (DAC). DAC-crosslinked cellulose-chitosan foam (CCLBD) was obtained by dissolution/regeneration using a LiBr aqueous solution, followed by crosslinking between chitosan and DAC. CCLBD possessed a three-dimensional structure with 40-200 nm wide pores composed of nanofibrils with a width of 10-20 nm, resulting in a high specific surface area of 230 m2/g. CCLBD was highly stable even acidic conditions in spite of a low crosslinking degree of 10.3%, which induced a slight reduction in the amino groups that interact with CR. CCLBD showed a CR adsorption capacity of 1548.2 mg/g and the adsorption process followed the Sips isotherm and pseudo-second-order models.

Micropatterning Silver Nanowire Networks on Cellulose Nanopaper for Transparent Paper Electronics.

Transparent microelectrodes with high bendability are necessary to develop lightweight, small electronic devices that are highly portable. Here, we report a reliable fabrication method for transparent and highly bendable microelectrodes based on conductive silver nanowires (AgNWs) and 2,2,6,6-tetramethylpiperidine-1-oxy (TEMPO)-oxidized cellulose nanofibers (CNFs). The AgNW-based micropatterns were simply fabricated on glass via poly(ethylene glycol) photolithography and then completely transferred to transparent TEMPO-CNF nanopaper with high bendability via vacuum-assisted microcontact printing (µCP). The AgNW micropatterns were embedded in the surface layer of TEMPO-CNF nanopaper, enabling strong adhesion to the nanopaper substrate. The resulting AgNW micropatterns on the TEMPO-CNF nanopaper showed an optical transparency of 82% at 550 nm and a sheet resistance of 54 Ω/sq when the surface density of AgNWs was as low as 12.9 µg/cm2. They exhibited good adhesion stability and excellent bending durability. After 12 peeling test cycles and 60 s sonication time, the sheet resistance of the AgNW networks embedded on TEMPO-CNF nanopaper increased by only ∼0.12 and ∼0.07 times, respectively. Furthermore, no significant change in electrical resistance was observed even after 3 bending cycles to nearly 90° and 500 cycles of 80% bending strain. Moreover, the AgNW patterns on TEMPO-CNF paper were successfully applied for constructing a transparent electric circuit as well as a solid-state electrochromic device. Overall, we proposed an effective way to fabricate AgNW micropatterns on transparent nanopaper, which can be expanded to various conductive materials for high-performance paper-based electronics.

Cellulose hydrogel with tunable shape and mechanical properties: From rigid cylinder to soft scaffold.

Cellulose hydrogel from aqueous solution of lithium bromide demonstrated excellent tunability of mechanical property and shape. A series of compression tests showed that cellulose hydrogel covered a wide range of mechanical property, where the compressive Young's modulus was controllable from 30 kPa to 1.3 MPa by changing the initial concentration of cellulose solution. Meanwhile, the diameter of the building block of gel, namely nano-fibrous cellulose, was constant at 15-20 nm irrelevant of the initial concentration of cellulose solution. Moreover, thanks to the biocompatibility of cellulose, the cultivation of cartilage tissue was successful in the micro-porous sponge-like cellulose hydrogel prepared by salt-leaching process. These findings show that this environmentally-benign versatile gel offers a new substrate for the biomaterial-based nanomaterial in biomedical applications.

Vacuum-assisted bilayer PEDOT:PSS/cellulose nanofiber composite film for self-standing, flexible, conductive electrodes.

Sustainable cellulose nanofiber (CNF)-based composites as functional conductive materials have garnered considerable attention recently for their use in soft electronic devices. In this work, self-standing, highly flexible, and conductive PEDOT:PSS-CNF composite films were developed using a simple vacuum-assisted filtration method. Two different composite films were successfully fabricated and then tested: 1) a single-layer composite composed of a mixture of PEDOT:PSS and CNF phases and 2) a bilayer composite composed of an upper PEDOT:PSS membrane layer and a CNF matrix sub-layer. The latter composite was constructed by electrostatic/hydrogen bonding interactions between PEDOT:PSS and CNFs coupled with sequential vacuum-assisted filtration. Our results demonstrated that the resultant bilayer composite film exhibited a competitive electrical conductivity (ca. 22.6Scm-1) compared to those of previously reported cellulose-based composites. Furthermore, decreases in the electrical properties were not observed in the composite films when they were bent up to 100 times at an angle of 180° and bent multiple times at an angle of 90°, clearly demonstrating their excellent mechanical flexibility. This study provides a straightforward method of fabricating highly flexible, lightweight, and conductive films, which have the potential to be used in high-performance soft electronic systems.

Protein adsorption of dialdehyde cellulose-crosslinked chitosan with high amino group contents.

Crosslinked chitosan was prepared by Schiff base formation between the aldehyde groups of dialdehyde cellulose (DAC) and the amino groups of chitosan and a subsequent reduction. DAC was obtained through periodate oxidation of cellulose and solubilization in hot water at 100°C for 1h. Three grades of DAC-crosslinked chitosan were prepared by adding various amounts DAC. The degrees of crosslinking as determined by amino group content were 3.8, 8.3, and 12.1%, respectively. DAC-crosslinked chitosan showed higher stability in the pH 2-9 range and no cytotoxicity was identified over the course of a 21-day long-term stability test. Also, DAC-crosslinked chitosan showed remarkably high bovine serum albumin (BSA) adsorption capacity at pH 5.5 as a result of the increased amino group content, due to the reaction between DAC and chitosan molecular chains occurring at multiple points even though DAC-crosslinked chitosan showed a lower degree of crosslinking.

Enhanced antidiabetic efficacy and safety of compound K/ß-cyclodextrin inclusion complex in zebrafish.

BACKGROUND: 20(S)-Protopanaxadiol 20-O-D-glucopyranoside, also called compound K (CK), exerts antidiabetic effects that are mediated by insulin secretion through adenosine triphosphate (ATP)-sensitive potassium (KATP) channels in pancreatic ß-cells. However, the antidiabetic effects of CK may be limited because of its low bioavailability. METHODS: In this study, we aimed to enhance the antidiabetic activity and lower the toxicity of CK by including it with ß-cyclodextrin (CD) (CD-CK), and to determine whether the CD-CK compound enhanced pancreatic islet recovery, compared to CK alone, in an alloxan-induced diabetic zebrafish model. Furthermore, we confirmed the toxicity of CD-CK relative to CK alone by morphological changes, mitochondrial damage, and TdT-UTP nick end labeling (TUNEL) assays, and determined the ratio between the toxic and therapeutic dose for both compounds to verify the relative safety of CK and CD-CK. RESULTS: The CD-CK conjugate (EC50 = 2.158µM) enhanced the recovery of pancreatic islets, compared to CK alone (EC50 = 7.221µM), as assessed in alloxan-induced diabetic zebrafish larvae. In addition, CD-CK (LC50 = 20.68µM) was less toxic than CK alone (LC50 = 14.24µM). The therapeutic index of CK and CD-CK was 1.98 and 9.58, respectively. CONCLUSION: The CD-CK inclusion complex enhanced the recovery of damaged pancreatic islets in diabetic zebrafish. The CD-CK inclusion complex has potential as an effective antidiabetic efficacy with lower toxicity.

Cellulose is not degraded in the tunic of the edible ascidian Halocynthia roretzi contracting soft tunic syndrome.

Soft tunic syndrome is a fatal disease in the edible ascidian Halocynthia roretzi, causing serious damage to ascidian aquaculture in Korea and Japan. In diseased individuals, the tunic, an integumentary extracellular matrix of ascidians, softens and eventually tears. This is an infectious disease caused by the kinetoplastid flagellate Azumiobodo hoyamushi. However, the mechanism of tunic softening remains unknown. Because cellulose fibrils are the main component of the tunic, we compared the contents and structures of cellulose in healthy and diseased tunics by means of biochemical quantification and X-ray diffractometry. Unexpectedly, the cellulose contents and structures of cellulose microfibrils were almost the same regardless of the presence or absence of the disease. Therefore, it is unlikely that thinning of the microfibrils occurred in the softened tunic, because digestion should have resulted in decreases in crystallinity index and crystallite size. Moreover, cellulase was not detected in pure cultures of A. hoyamushi in biochemical and expressed sequence tag analyses. These results indicate that cellulose degradation does not occur in the softened tunic.

Synergistic Potentials of Coffee on Injured Pancreatic Islets and Insulin Action via KATP Channel Blocking in Zebrafish.

Pancreatic islets (PIs) are damaged under diabetic conditions, resulting in decreased PI size. This study examined the regenerative effects of coffee and its components (caffeine, CFI; trigonelline, TRG; chlorogenic acid, CGA) on zebrafish larval PIs and ß-cells damaged by administration of alloxan (AX). In addition, the influence of coffee and its active components on KATP channels was investigated using diazoxide (DZ) as a KATP channel activator. PI size and fluorescence intensity were significantly increased in the coffee-treated group relative to the no-treatment group (P < 0.0001). In addition, coffee exerted significant regenerative effects on pancreatic ß-cells (p = 0.006). Treatment with TRG and CGA rescued PI damage, and the combination of TRG/CGA had a synergistic effect. In conclusion, the results indicate that coffee has beneficial effects on AX-damaged PIs and may also be useful as a blocker of pancreatic ß-cell K(+) channels.

Investigation of structural modification and thermal characteristics of lignin after heat treatment.

Milled wood lignin was subjected to heat treatment between 150 and 300°C to understand the pattern of its structural modification and thermal properties. When the temperature was elevated with interval of 50°C, the color of the lignin became dark brown and the lignin released various forms of phenols from terminal phenolic groups in the lignin, leading to two physical phenomena: (1) gradual weight loss of the lignin, up to 19% based on dry weight and (2) increase in the carbon content and decrease in the oxygen content. Nitrobenzene oxidation and (13)C NMR analyses confirmed a cleavage of ß-O-4 linkage (depolymerization) and reduction of methoxyl as well as phenolic hydroxyl group were also characteristic in the lignin structure during heat treatment. Simultaneously with lignin depolymerization, GPC analysis provided a possibility that condensation between lignin fragments could also occur during heat treatment. TGA/DTG/DSC data revealed that thermal stability of lignin obviously increased after heat treatment, implicating the structural rearrangement of lignin to reduction of ß-O-4 linkage as well as accumulation of CC bonds.