Protein glycosylation is an important post-translational modification that plays a crucial role in many biological processes. Because of the low abundance of glycoproteins and high complexity of clinical samples, the development of methods to selectively capture glycoproteins/glycopeptides is crucial to glycoproteomics study. In this work, a kind of highly cross-linked chitosan microspheres (CSMs) was prepared using epichlorhydrine as a cross-linker from chitosan solution in an alkaline/urea aqueous system. The results showed that CSMs had high amino groups content, large surface area, mesoporous structure, good acidic resistance, and high strength by various tests. On the basis of hydrophilic interaction between the polar groups (amino groups and hydroxyl groups) on CSMs and glycan moieties on glycopeptides, the prepared CSMs were applied to specific capture of N-glycopeptides from standard protein digests and complex biological samples (body fluids and tissues). The CSMs exhibited high selectivity (HRP/BSA = 1:100), good sensitivity (4.5 × 10–10 M of HRP), good recovery yield (74.9–106.4%), and high binding capacity (100 mg g–1) in glycopeptides enrichment. Because of the excellent performance in glycopeptides enrichment, CSMs were applied to selectively enrich N-glycopeptides from tryptic digests of human serum and rat brain followed by nanoLC–MS/MS analysis. We identified 194 and 947 unique N-glycosylation sites from 2 μL of human serum and 0.1 mg of rat brain, respectively. Additionally, the extraction time of our method was much shorter than the previously reported methods. Therefore, the fabricated CSMs with desirable properties will find broad application in large-scale and in-depth N-glycoproteome analysis.

Biodegradable plastics are urgently needed in the biomedical field to avoid the secondary surgery for implants after completing the repair of nonload bearing bone defects. Herein, novel chitin based plastics were successfully fabricated by changing the shape and aggregation state structure of chitin hydrogels through drying under a negative pressure, which led to a plastic deformation. The chitin hydrogels were prepared by using an environmentally friendly aqueous NaOH/urea solvent, and then radially oriented under the negative pressure to form chitin bioplastics (CP) on the basis of the removability of the chitin molecular bundles in the hydrogels. Moreover, hydroxyapatite (HAP) was in situ synthesized to obtain the chitin/HAP composite plastics (CHP). Their structure and properties were characterized by SEM, FTIR, 13C NMR, X-ray diffraction and mechanical testing. The results indicated that the bioplastic preparation was a “green” physical process, and the incorporation of HAP reinforced significantly the tensile strength of CHP. The viability, biocompatibility, hemocompatibility and in vivo histocompatibility of the bioplastics were evaluated systematically. The introduction of HAP could improve the cell adhesion, proliferation and differentiation of the osteoblast cells. Moreover, CHP exhibited good histocompatibility, hemocompatibility and in vivo biodegradability, showing potential application in the bone tissue engineering field.Keywords: Biocompatibility; Chitin bioplastic; Hydroxyapatite; In vivo biodegradability; Orientation structure;

Developing eco-friendly and low-cost electronics is an effective strategy to address the electronic waste issue. In this study, transparent cellulose nanopaper (T-paper) and polylactic acid (PLA) electret were used to construct a biodegradable and transparent paper-based electret nanogenerator. The nanogenerator could be assembled with paper products to form a self-powered smart packaging system without impairing the appearance, due to the high transparency and desirable output performance. Furthermore, the self-degradation property in the natural soil of the nanogenerator is demonstrated, indicating that the nanogenerator is recycled and will not pollute the environment. We anticipate that this study will provide new insights to develop eco-friendly power source and paper-based electronics.Keywords: biodegradable; electret nanogenerators; paper-based; self-powered; transparent;

Chitosan has biocompatibility and biodegradability; however, the practical use of the bulk chitosan materials is hampered by its poor strength, which can not satisfy the mechanical property requirement of organs. Thus, the construction of highly strong chitosan-based materials has attracted much attention. Herein, the high strength nanofibrous hydrogels and films (CS-E) were fabricated from the chitosan solution in LiOH/KOH/urea aqueous system via a mild regenerating process. Under the mild condition (ethanol at low temperature) without the severe fluctuation in the system, the alkaline-urea shell around the chitosan chains was destroyed, and the naked chitosan molecules had sufficient time for the orderly arrangement in parallel manner to form relatively perfect nanofibers. The nanofibers physically cross-linked to form CS-E hydrogels, which could be easily oriented by drawing to achieve a maximum orientation index of 84%, supported by the scanning electron microscopy and two-dimensional wide-angle X-ray diffraction. The dried CS-E films could be bent and folded arbitrarily to various complex patterns and shapes. The oriented CS-E films displayed even ultrahigh tensile strength (282 MPa), which was 5.6× higher than the chitosan films prepared by the traditional acid dissolving method. The CS-E hydrogels possessed hierarchically porous structure, beneficial to the cell adhesion, transportation of nutrients, and removal of metabolic byproducts. The cell assay results demonstrated that the CS-E hydrogels were no cytotoxicity, and osteoblastic cells could adhere, spread, and proliferate well on their surface. Furthermore, the oriented CS-E hydrogels could regulate the directional growth of osteoblastic cells along the orientation direction, on the basis of the filopodia of the cells to extend and adhere on the nanofibers. This work provided a novel approach to construct the oriented high strength chitosan hydrogels and films.

•The TCNC membranes were produced via a facile vacuum-assisted method.•The superhydrophilic and underwater superoleophobic TCNC membranes could separate oil/water efficiently.•The cholesteric TCNC membranes weaved with fibrous TCNCs had homogeneous pore size and no pore wall, leading to the high flux of water.•The TCNC membranes could separate not only oil-in-water nanoemulsions, but also oil-in-water and water-in-oil microemulsions.•The TCNC membranes exhibited high mechanical strength, excellent pH- and temperature-stability, and good cycling performance.Faced on the threat of oil-contaminated wastewater to the environment and health of human body, we demonstrated, for the first time, a facile method for fabrication of novel nanoporous cellulose membranes derived from renewable marine resources (shell of tunicate). The fibrous tunicate cellulose nanocrystals (TCNCs) were prepared by acid hydrolysis, and exhibited high degree of crystallinity and distinct cholesteric liquid crystal behavior. Thus, the TCNC membranes were constructed by vacuum-assisted filtration of TCNCs suspensions, showing hierarchical structure, and superhydrophilic/underwater superoleophobic characters. The experimental results confirmed that the TCNC membranes were beneficial for highly efficient separation of oily water, which not only could separate various oil-in-water nanoemulsions, but also were applicable for oil-in-water microemulsions and water-in-oil emulsions. The thickness, pore size, water flux, and oil rejection of the TCNC membranes could be controlled by the dosage of TCNCs. Moreover, they exhibited high mechanical strength, excellent pH- and temperature-stability, and good cycling performance. On the basis of the combining of cholesteric liquid crystal structure and superhydrophilicity of fibrous tunicate cellulose nanocrystals, a new strategy to construct novel filter membranes for the highly effective oil/water separation was provided here.

Chitin and chitosan are enticing natural polymers derived from seafood wastes, and their applications mostly depend on the degree of acetylation (DA). For their efficient utilization, a series of universal solvents for the direct dissolution from chitin to chitosan with various DA ranged from 5 to 94% were designed, and robust hydrogels were constructed from their solution via a physical regeneration, for the first time. The NMR results demonstrated that K+ of KOH interacted easily with C═O group to break the NH...O═C intermolecular hydrogen bonds of chitin, whereas Li+ of LiOH could bound with NH2 group to promote the destruction of NH...O6 hydrogen bonds of chitosan. Thus, a series of LiOH/KOH/urea aqueous solutions with weight ratios of LiOH to KOH from 0 to 2.5 were developed to directly dissolve these biomacromolecules with DAs ranging from 5 to 94%. Subsequently, a series of coagulants were also exploited for the regeneration of these chitin/chitosan solutions to construct the robust hydrogels with different DAs. These chitin/chitosan hydrogels exhibited homogeneous network structure consisting of nanofibers with a mean diameter of ∼30 nm as well as excellent mechanical properties and high transparency. By adding a fluorescent agent with strong affinity with only the -NH2 group, the resulting fluorescent hydrogels with different DAs could be visually recognized because the intensity reflected the different contents of the active amino group. Furthermore, the wastewater after regeneration could be easily recycled via reduced pressure distillation to reuse without consuming any chemicals or producing byproducts, leading to a thoroughly green process. This work opens a new avenue for dissolving biomacromolecules from chitin to chitosan via universal solvents and to construct new materials via green transformation, which would be beneficial for global sustainable development.Keywords: Chitin; Chitosan; Green transformation; Recycling of wastewater; Universal solvents;

According to the principles of green chemistry and co-efficiency, natural polysaccharides with biological activities, particularly immunoregulation and antitumor activities, have attracted increasing attention. However, the lack of information concerning the pharmacokinetics of polysaccharides is one of the major obstacles limiting their rational clinical use. In this study, triple helical β-glucan (THG), a β-1,6-branched β-1,3-glucan isolated from Lentinus edodes, was studied to clarify its cellular uptake after parenteral (e.g. intraperitoneal) administration and to determine its effect on immune cells in murine tumor models. The results obtained from size exclusion chromatography with static light scattering, differential refractometry and viscometry (SEC-LLS–RI–Vis) and atomic force microscopy (AFM) confirmed that all three THG samples displayed an extended stiff chain conformation with apparent average contour lengths of 598 nm, 510 nm and 117 nm, respectively. The ex vivo results indicated that THG directly promoted cell proliferation of peritoneal macrophages, whole spleen cells and lymphocytes, and activated peritoneal macrophages with TNF-α production. In our findings, the intraperitoneally (i.p.) administrated THG was initially ingested by peritoneal resident macrophages, which transported it to lymph nodes, thymus and even tumor. Simultaneously, THG in macrophages was biodegraded into fragments with granular shapes and small size, which were sufficiently active to be easily ingested by neutrophils. Furthermore, THG fragments could promote the infiltration of macrophages, neutrophils and DCs into tumors, and also activate these cells to enhance their cytotoxicity toward tumor cells, leading to their apoptosis. This study provides important information concerning the ingestion and processing in vivo of triple helical β-glucan from natural products, leading to a better understanding of its antitumor mechanism through activating immune cells in murine tumor models.

Mushrooms are known as a delicacy due to their delicious taste and rich nutrition, and their β-glucans have antitumor activity. Here, a triple helical β-glucan (THG) isolated from Lentinus edodes was successfully fractionated into nine fractions with different weight-average molecular weights (Mw) through ultrasonic irradiation. The Mw, radius of gyration (〈Rg〉z), hydrodynamic radius (〈Rh〉z), structure-sensitive parameters (ρ), contour length (L), persistence length (q) and molar mass per contour length (ML) were characterized by static light scattering (SLS), dynamic light scattering (DLS), and atomic force microscopy (AFM). The results indicated that THG displayed an extended chain conformation with ρ values of 2.1 ± 0.1 for the nine fractions, as well as ML and q values of 2160 nm−1 and 110 nm in water, which were consistent with the data for triple helical polysaccharides. In combination with the apparent length (Lap) values visualized with AFM and Mw, the molar mass per apparent contour length (MLap) was calculated to be 2242 nm−1, which was similar to that obtained from SLS according to the wormlike cylinder model. Thus, we established a novel method using AFM for characterizing the chain stiffness of polysaccharides. The results from an animal assay demonstrated that THG significantly inhibited H22 tumor growth without damage to organisms, and the THG fractions with relatively low molecular weight and/or higher stiffness showed stronger antitumor activity, revealing the significant molecular weight- and chain conformation-dependences of antitumor activity. Moreover, a schematic model to describe the interaction between THG and receptors on the immune cell membrane was proposed to illustrate these results. This work provides important information for characterizing the chain conformation of polysaccharides and understanding the relationship between structure and antitumor activity, which is relevant for the treatment of hepatocellular carcinoma in clinic.

Excess bilirubin often evokes hepatobiliary system dysfunction. In the present work, we developed an efficient, safe and blood compatible adsorbent for bilirubin removal from human blood. In view of the highly effective adsorption of carbon nanotubes (CNTs) on bilirubin but with many side effects, and good biocompatibility of chitin but with low efficiency for bilirubin removal, new chitin/carbon nanotube (Ch/CNT) nanofibrous microspheres were constructed from chitin solution in NaOH/urea aqueous system by blending with CNTs. The results of AFM, SEM, and TEM demonstrated that the CNTs were dispersed well in the chitin matrix, and the chitin nanofibers intertwined with CNTs to form hybrid chitin/CNT nanofibers and then weaved into a 3D interconnected network architecture. Moreover, lysine (Lys), a highly specific ligand for bilirubin, was immobilized tightly to the hybrid microspheres to obtain Ch/CNT/Lys. The resultant microspheres possessed large surface area and hierarchical pores including mesopores and micropores, which could allow bilirubin to enter easily and store, leading to highly efficient adsorption. The Ch/CNT/Lys microspheres exhibited excellent bilirubin adsorption property (107.2 mg g−1) and efficient bilirubin clearance rate from real hyperbilirubinemia plasma competing with protein, as well as good cell affinity and blood compatibility, as a result of the combination of the high adsorption of CNTs and inherent biocompatibility of chitin and lysine. Therefore, an effective strategy to develop a novel biocompatible and blood compatible bilirubin adsorbent is provided, showing potential applications for hemoperfusion in blood purified therapy.

Smart hydrogel actuators with excellent biocompatibility and biodegradation are extremely desired for biomedical applications. Herein, we have constructed bio-hydrogel actuators inspired by the bilayer structures of plant organs from chitosan and cellulose/carboxymethylcellulose (CMC) solution in an alkali/urea aqueous system containing epichlorohydrin (ECH) as a crosslinker, and demonstrated tight adhesion between two layers through strong electrostatic attraction and chemical crosslinking. The bilayer hydrogels with excellent mechanical properties could carry out rapid, reversible, and repeated self-rolling deformation actuated by pH-triggered swelling/deswelling, and transformed into rings, tubules, and flower-, helix-, bamboo-, and wave-like shapes by effectively designing the geometric shape and size. The significant difference in the swelling behavior between the positively charged chitosan and the negatively charged cellulose/CMC layers generated enough force to actuate the performance of the hydrogels as soft grippers, smart encapsulators, and bioinspired lenses, showing potential applications in a wide range of fields including biomedicine, biomimetic machines, etc.

•Chitin/carbon nanotubes (Ch/CNT) composite hydrogels were prepared from chitin/NaOH/urea aqueous solution by blending with modified CNTs.•The Ch/CNT composite hydrogels exhibited nanofibrillar network structure, excellent mechanical properties and biodegradability in vitro.•The Ch/CNT composite hydrogels with good biocompatibility could enhance the proliferation of neuronal cells and Schwann cells in vitro.•The incorporation of CNTs could significantly enhance cell adhesion, proliferation and neurite outgrowth of neuronal cells.In the past decades, extensive studies have demonstrated that carbon nanotubes (CNTs) could promote cell adhesion, proliferation and differentiation of neuronal cells. However, the potential cytotoxicity in biological systems severely restricted the utilization of CNTs as substrates for neural growth. In this study, biocompatible chitin/carbon nanotubes (Ch/CNT) composite hydrogels were developed via blending modified CNTs with chitin solution in 11 wt% NaOH/4 wt% urea aqueous system, and subsequently regenerating in ethanol. As the CNTs were dispersed homogeneously in chitin matrix and combined with chitin nanofibers to form a compact and neat Ch/CNT nanofibrous network through intermolecular interactions, such as electrostatic interactions, hydrogen bonding and amphiphilic interaction, etc. The tensile strength and elongation at break of the Ch/CNT composite hydrogels were obviously enhanced, and the swelling ratio decreased. In addition, the Ch/CNT hydrogels exhibited good hemocompatibility, biodegradation in vitro and biocompatibility without cytotoxicity and neurotoxicity nature to neuronal and Schwann cells (PC12 cells and RSC96 cells). Especially, the Ch/CNT3 composite hydrogels exhibited significant enhancement of the neuronal cell adhesion, proliferation and neurite outgrowth of neuronal cells with a great increase in both the percentage and the length of neurites. Therefore, we provide a simple and efficient approach to construct the novel Ch/CNT hydrogels as neuronal growth substrates for the potential application in nerve regeneration.Download high-res image (342KB)Download full-size image

•A facile route to fabricate ampholytic microspheres was provided.•The ampholytic microspheres showed homogeneous structure and magnetic responsiveness.•The microspheres exhibited highly efficient adsorption towards dyes and metal ions.•The microspheres were used as column packing for dye wastewater purification.•The adsorbents could be recycled, reused, and biodegraded in soil.Natural polymers as abundant resource are excellent candidates of adsorbents for wastewater purification due to their inherent advantages such as strong affinity, biodegradability, and non-toxic. In this work, ampholytic polyelectrolyte microspheres were fabricated successfully via emulsification procedure from the homogeneous chitosan/carrageenan solution in LiOH/KOH/urea aqueous system, showing good compatibility and homogeneous network structure. In the chitosan/carrageenan blend solution, chitosan displayed the neutral feature, as a result of the dissolution caused by destruction of the native intermolecular hydrogen bonds rather than protonation of the amino groups, thus no flocculation occurred here. The experimental results demonstrated that the ampholytic microspheres were composed of positively charged chitosan and negatively charged carrageenan, and the magnetic Fe3O4 nanoparticles with a mean diameter of 180 nm were embedded in the composite matrix, showing a sensitive magnetic responsiveness. The ampholytic microspheres exhibited highly efficient adsorption capacity towards both cationic and anionic dyes and heavy metal ions in wastewater, as a result of their strong electrostatic and chelating affinity. The ampholytic chitosan/carrageenan composite matrix in microspheres played a dominant role in the adsorption of pollutants, and the Fe3O4 nanoparticles were mainly contributed to magnetic separation. The effects of ionic strength and pH value on adsorption behaviors indicated that the microspheres were available to be used in a harsh environment. The ampholytic microspheres could also be used as column packing for rapid and efficient dye wastewater purification. Furthermore, the microspheres could be recycled, reused, and biodegraded in soil, showing great potentials in the field of the water decontamination.

Carbonaceous electrode materials for potassium-ion batteries (KIBs) are attractive due to the abundant resource of potassium and their rational capability. However, their rate capability and cycle life are mainly hindered by the intercalation chemistry involving repeated potassium insertion/extraction that are difficult to maintain within a short time or long-term cycling. Here, for the first time, a seafood waste (chitin)-derived hierarchically porous nitrogen-doped carbon microsphere (NCS) electrode with a surface-driven potassium storage mechanism is developed. The NCS electrode demonstrates a record high rate capability of 154 mA h g−1 at 72 C and ultralong cycle life of 4000 cycles without obvious capacity decay (180 mA h g−1 at 1.8 C), representing the best rate capability and longest cycle life among all electrodes in KIBs and even supassing most electrodes in sodium-ion batteries (NIBs). Further kinetic analysis and first-principle calculations reveal the dominated capacitive surface-driven mechanism of potassium storage in NCS, which is attributed to the hierarchically porous microstructure and nitrogen-doped carbon structure with enhanced potassium adsorption capability and electronic/ionic conductivities.N-doped carbon microspheres derived from reconstructed chitin microspheres demonstrate ultrahigh rate capability and ultralong cycle life as anode for potassium-ion batteries.Download high-res image (310KB)Download full-size image

This review summarizes recent progress of the robust and smart hydrogels prepared from natural polymers including polysaccharides, proteins, etc. These hydrogels exhibit outstanding mechanical properties due to their nanofibrous aggregated microstructures and special crosslinking networks. Furthermore, these hydrogels show some smart stimuli-responsive behaviors triggered by pH, temperature, light, electricity and magnetism. Hopefully, these hydrogels derived from natural polymers with inherent biodegradation and biocompatibility have great application potential in the fields of biomedicine, tissue engineering, soft robots and bio-machine.

AbstractTo face the increasing demand of self-healing hydrogels with biocompatibility and high performances, a new class of cellulose-based self-healing hydrogels are constructed through dynamic covalent acylhydrazone linkages. The carboxyethyl cellulose-graft-dithiodipropionate dihydrazide and dibenzaldehyde-terminated poly(ethylene glycol) are synthesized, and then the hydrogels are formed from their mixed solutions under 4-amino-DL-phenylalanine (4a-Phe) catalysis. The chemical structure, as well as microscopic morphologies, gelation times, mechanical and self-healing performances of the hydrogels are investigated with 1H NMR, Fourier transform infrared spectroscopy, atomic force microscopy, rheological and compression measurements. Their gelation times can be controlled by varying the total polymer concentration or 4a-Phe content. The resulted hydrogels exhibit excellent self-healing ability with a high healing efficiency (≈96%) and good mechanical properties. Moreover, the hydrogels display pH/redox dual responsive sol-gel transition behaviors, and are applied successfully to the controlled release of doxorubicin. Importantly, benefitting from the excellent biocompatibility and the reversibly cross-linked networks, the hydrogels can function as suitable 3D culture scaffolds for L929 cells, leading to the encapsulated cells maintaining a high viability and proliferative capacity. Therefore, the cellulose-based self-healing hydrogels show potential applications in drug delivery and 3D cell culture for tissue engineering.

To develop a facile approach for the dissolution of cellulose, a novel solvent (9.3 wt % NaOH/7.4 wt % thiourea aqueous solution) was used, for the first time, to dissolve cellulose within 5 min at 8 °C. The results of NMR and Raman spectra demonstrated that stable thiourea···OH– complexes were formed through strong hydrogen bonds in NaOH/thiourea at room temperature. Moreover, the strength of the hydrogen bonds in thiourea···OH– complexes was much higher than that in urea···OH– complexes, and the number of thiourea···OH– complexes increased significantly in 9.3 wt % NaOH/7.4 wt % thiourea compared to that in 9.5 wt % NaOH/4.5 wt % thiourea, which dissolved cellulose at −5 °C, leading to the dissolution of cellulose at a relatively high temperature (8 °C). The cellulose that dissolved at such a high temperature was metastable. The results of dynamic light scattering and transmission electron microscope experiments confirmed that the extended cellulose chains and their aggregates coexisted in the dilute cellulose solution. Interestingly, stiff cellulose chains could be self-assembled in parallel to form nanofibers in the metastable cellulose solution, from which cellulose microspheres consisting of nanofibers could be easily produced by inducing heating. This work not only proposed a novel method for the dissolution of cellulose in aqueous system at temperatures over 0 °C but also opened up a new pathway for the construction of nanofibrous cellulose materials.

TiO2/cellulose composite aerogels were easily fabricated by the in situ synthesis of TiO2 nanoparticles in a cellulose matrix at a mild temperature (≤80 °C). The TiO2/cellulose aerogel structure and morphology were analyzed with scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermal gravimetric analysis, and nitrogen adsorption–desorption tests as well as tensile testing. The results revealed that the TiO2 content in the composite aerogels increased dramatically with an increase of the treating times in tetrabutyl titanate to achieve a value of 65 wt%, which was much higher than that in literatures. Depending on the number of hydrolysis cycles, the mean diameter of the TiO2 nanoparticles was controlled to be approximately from 1.5 ± 1.0 to 3.5 ± 2.0 nm. The TiO2/cellulose nanocomposite aerogel exhibited excellent mechanical strength, good UV screening ability as well as highly efficient photo-catalytic activity under weak UV light irradiation. This work opens a new avenue to construct TiO2/cellulose aerogels with a high content and small size of TiO2 nanoparticles, thus demonstrating potential applications in the fields of UV screening and catalyst.

•CNFs was used as reductant and stabilizer in synthesizing AuNPs for the first time.•AuNPs were firmly immobilized along CNFs with high stability.•Size and morphology of AuNPs were tunable by the reaction parameters.•CNFs-AuNPs exhibited peroxide mimic catalytic performance.•CNF-AuNPs were applied in glucose detection with LOD as low as 94.5 nM.Chitin is the second most abundant natural biopolymer on earth after cellulose with vast application potential. In the present work, the chitin nanofibrils (CNFs) fabricated through a simple physical method were validated, for the first time, to be capable of simultaneously generating and immobilizing gold nanoparticles (AuNPs) via a one-step synthesis. In our findings, CNFs acted as both reductant for the in-situ synthesis of AuNPs and stabilizer for the generated AuNPs, due to the reducibility and chelation capacity of the amino groups on chitin. When the CNFs concentration varied from 2.0 to 7.1 mg/mL, well dispersed AuNPs with controllable diameters (7–30 nm) were synthesized and immobilized along the chitin nanofibrils, showing high stability for at least three months. This new pathway was an environmentally friendly process, and even generated small AuNPs with diameters of less than 10 nm. Moreover, the CNF-AuNPs displayed peroxidase mimic behavior and catalyzed the oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 to produce a blue solution. When combined with glucose oxidase, the CNF-AuNPs could sensitively detect glucose with a limit of 94.5 nM, which was highly specific, safe, cheap, and visible with low contamination. This work has put forward a facile “green” pathway for the heterogeneous synthesis of the size controllable and stable AuNPs immobilized on the biocompatible chitin nanofibrils and their potential in biosensing were evaluated.(a) Chitin nanofibrils (CNFs) were used as both reductant and stabilizer in the synthesis of gold nanoparticles (AuNPs) for the first time. (b) The size and morphology of the AuNPs were tunable by adjusting the reaction parameters. (c) Size and morphology of AuNPs were tunable by adjusting the reaction parameters. (d) The CNF-AuNPs were applied in glucose detection with a limit of detection as low as 94.5 nM.Download high-res image (122KB)Download full-size image

Dendritic nanotubes (DNTs) with hydrophobic cavities were constructed directly from rigid branched β-1,3-D-glucan (AF1) in aqueous solution, and the AF1 sample was isolated from the fruiting bodies of Auricularia auricula-judae, a household nutritional food. The structure of AF1 dendritic nanotubes was demonstrated with a transmission electron microscope (TEM) and a scanning electron microscope (SEM), and a schematic diagram was proposed to describe the formation process, which was supported by the results of static/dynamic light scattering (SLS/DLS) and atomic force microscopy (AFM). In solution, a sequential self-assembly of the AF1 chains in a parallel manner occurred to form lamellas followed by self-curling into nanotubes with the mean diameters from 20 to 80 nm, depending on the concentration and molecular weight of AF1, through hydrogen bonding and hydrophilic/hydrophobic interaction. As a result of the dendritic structure, the AF1 aggregates exhibited highly condensed hydrophobic regions, which could be used as carriers to achieve a high concentration of the target molecules. In our findings, the anticancer drug DOX and the fluorescent probe TPA-BMO could be loaded into the hydrophobic region of DNTs. Interestingly, DOX-loaded DNTs of AF1 exhibited high drug loading capacity and pH-triggered sustained release behaviors (>23 days) with reduced cytotoxicity in vitro. Moreover, the bioimaging experiment demonstrated that TPA-BMO-loaded DNTs of AF1 induced stronger fluorescence intensity than TPA-BMO alone, and maintained a longer duration time (18 days) in vivo. Therefore, the DNTs of AF1 have promising applications as bioactive carriers, especially in the fields of drug delivery and bioimaging.

As a breakthrough to the traditional 1H diffusometry, the interaction of cations with cellulose is investigated via7Li and 23Na PFG-SE NMR. The diffusion coefficient of Li+ decreases more than that of Na+ with the addition of cellulose, which indicates a stronger binding of LiOH with the macromolecule. Therefore, a new, facile, accurate and repeatable method to characterize ion/polymer interactions is established.

Biocompatible hydrogels with high strength, high precision patterns, and arbitrary 3D shapes are extremely desired soft platforms in the biomedicine fields. On the basis of the thermal-reversible sol–gel transition of agarose and the formation of nanofibers below 35 °C, a robust and thermoplastic hydrogel (TPG) was fabricated by in situ polymerization of acrylamide in the agarose matrix. The tensile fracture stress/strain values of the TPG were unexpectedly higher than those of both agarose and polyacrylamide hydrogels as a result of the double networks reinforced with nanofibers. The TPG could reversibly soften and harden by heating and cooling treatment, respectively, leading to an excellent mechanical recoverability and reprocessing ability. Thus, arbitrary 3D-shaped hydrogels and micro-patterns embossed on the TPG surface with a high resolution of 1 μm were constructed. The rigid TPG exhibited a remarkable affinity for the adhesion and proliferation of cells. In particular, the TPGs with microgrooves could highly guide the oriented growth of osteoblasts, showing potential applications in the field of tissue engineering.

Weak interactions, though sometimes easily ignored, play an important role in macromolecule dissolution. In this work, the characterization of weak interactions between urea and cellulose in a LiOH/urea aqueous solution was accomplished and confirmed in situ, for the first time, using PFG-SE NMR, FT-IR and solvatochromic methods, etc. The NMR results indicated the binding of urea with cellulose in the solution, demonstrating the existence of the weak interactions between them. Subsequently, the solvatochromic methods revealed that urea hardly affected the hydrogen bond donor (HBD acidity) and hydrogen bond acceptor (HBA basicity) properties of the solvent, but was related to its dipolarity and polarizability, indicating that dispersion forces existed therein, but not likely hydrogen bonding, which was also supported by the FT-IR. Furthermore, the impact of weak interactions between urea and cellulose was demonstrated to facilitate the dissolving process. The fine dispersion and good stability of cellulose in the solution were maintained by mitigating the effect of the hydrophobic portions from all the dilute, semi-dilute and concentrated regimes, supported by the results of dynamic light scattering (DLS), rheology, NMR, etc. Therefore, the transmittance and mechanical properties of the regenerated cellulose materials prepared from the cellulose solution in the alkali/urea aqueous system were enhanced, compared with those in the alkali only system. This work provided significant and new experimental insights into the non-covalent weak interactions between urea and macromolecules from the viewpoints of polymer physics and physical chemistry, which could never be ignored and underestimated. The indispensable weak interactions in the system are also important for the green conversion of natural biomass into new materials via physical processes.

The dual threats of the depletion of nonrenewable energy and environmental pollution caused by petroleum-based polymers motivate utilization of naturally occurring polymers to create new materials. Cellulose, as the most abundant natural polymer on earth, has attracted attention due to its renewability, wide availability, low-cost, biocompatibility and biodegradability, etc. Regenerated cellulose may be constructed simply via physical dissolution and regeneration, an environmentally friendly process avoiding the consuming of chemicals since most of the reagents (solvents, coagulant, etc.) may be recycled and reused. “Green” solvents and techniques for the preparation of the environmentally friendly regenerated cellulose materials have been developed successfully, showing great potentials in the fields of polymer science and technology.In this article, the widely used non-derivatizing cellulose solvents are summarized, including their dissolution mechanisms. Regenerated cellulose materials with different functions and properties have been designed and fabricated in different forms, such as filaments, films/membranes, microspheres/beads, hydrogels/aerogels and bioplastics, etc., to meet various demands. The concept of regeneration through a physical process is illustrated, and a number of novel regenerated cellulose materials are introduced for wide applications in textiles, packaging, biomedicine, water treatment, optical/electrical devices, agriculture and food, etc. The methodology of material processing and the resultant properties and functions are also covered in this review, with emphasis on the neat regenerated cellulose materials and the composite materials. The 277 references cited concerning the direct preparation of cellulose materials via physical dissolution and regeneration are representative of the wide impact and benefits of the regenerated cellulose materials to society.

The water soluble β-(1 → 3)-D-glucan with short branches (AF1) isolated from Auricularia auricula-judae was successfully fractionated by ultrasonication into three fractions with different weight-average molecular weights (Mws). The results of static and dynamic laser light scattering, viscometry and atomic force microscopy confirmed that the AF1 samples adopted a stiff chain conformation in water, and the coexistence of individuals and aggregates occurred gradually with increasing concentration. The AF1 sample with the highest Mw easily self-entangled, and exhibited a strong shear rate-dependence of viscosity in water. The glucans displayed anti-hepatoma activity and significantly inhibited H22 tumour growth without cytotoxicity towards normal tissues. They displayed both molecular weight- and dosage-dependencies of anti-tumour activity, and the sample with an Mw of 7.7 × 105 at the dosage of 5 mg kg−1 exhibited the highest inhibition ratio of ∼77% against H22 tumour, even significantly higher than the positive control of cytoxan. The immunohistochemical and western blot analyses revealed that the AF1 glucans triggered cell apoptosis, indicated by the activation of caspase 3/9 and down-regulated tumour angiogenesis factors of VEGF and CD31. The underlying antitumor mechanism was suggested to induce tumour cell apoptosis and to inhibit angiogenesis in tumour tissues via enhancement of the immune-response. Taken together, the AF1 β-glucan was a potent natural drug candidate with high anti-cancer activities and less cytotoxicity, and the AF1 sample with a moderate molecular weight existed in aqueous solution as a more extended chain conformation, which plays an important role in activating immune responses.

Conducting polymers have emerged as frontrunners to be alternatives for nerve regeneration, showing a possibility of the application of polyaniline (PANI) as the nerve guidance conduit. In the present work, the cellulose hydrogel was used as template to in situ synthesize PANI via the limited interfacial polymerization method, leading to one conductive side in the polymer. PANI sub-micrometer dendritic particles with mean diameter of ∼300 nm consisting of the PANI nanofibers and nanoparticles were uniformly assembled into the cellulose matrix. The hydrophobic PANI nanoparticles were immobilized in the hydrophilic cellulose via the phytic acid as “bridge” at presence of water through hydrogen bonding interaction. The PANI/cellulose composite hydrogels exhibited good mechanical properties and biocompatibility as well as excellent guiding capacity for the sciatic nerve regeneration of adult Sprague–Dawley rats without any extra treatment. On the basis of the fact that the pure cellulose hydrogel was an inert material for the neural repair, PANI played an indispensable role on the peripheral nerve regeneration. The hierarchical micro-nanostructure and electrical conductivity of PANI could remarkably induce the adhesion and guiding extension of neurons, showing its great potential in biomedical materials.

A readily available ruthenium(II) catalyst was developed for the catalytic hydrogenation of aldehydes with a TON (turnover number) up to 340000. It can be performed without base and solvent, showing highly industrial potential. High chemoselectivity can be achieved in the presence of alkenyl and ketone groups. Further application of this protocol in glucose reduction showed good efficiency. Theoretical studies revealed that the rate-determining step is the hydrogenation step, not the carboxylate-assisted H2 activation step.

•PR-CA was characterized to be a β-(1→3)-d-glucan with multiple branches.•The chain stiffness of PR-CA in water was directly visualized by AFM and TEM.•The aggregation behavior of PR-CA was studied in water/DMSO solutions.•The branched PR-CA chains took parallel aggregation to form hollow nanofibers.A polysaccharide coded as PR-CA was extracted from Polyporus rhinoceros and determined to be a β-(1→3)-d-glucan with multiple branches. The weight-average molecular weights (Mw) of PR-CA in dimethylsulfoxide (DMSO) and in water were determined with static light scattering (SLS) to be 3.57 × 105 and 1.79 × 107, indicating existence of the single chains in DMSO and co-existence of single chains and aggregates in water. Moreover, the stiffness of single chains of PR-CA in water was directly visualized by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The hollow structure of PR-CA nanofibers with width of 30–40 nm and length of ∼350 nm formed in the water/DMSO (9:1, v:v) was demonstrated by a fluorescent probe tetraphenylethylene (TPE) via aggregation-induced emission (AIE). The formation of PR-CA nanofibers was ascribed to the parallel aggregation of the extended PR-CA chains due to the hydrogen bonding and hydrophobic interaction. This work offered valuable results for promising applications of natural branched β-glucans in the biological fields of drug inclusion, delivery and disease diagnosis.

•Stiff branched β-glucan in water transformed into flexible chain in DMSO.•The viscosity and chain size of AF1 drop abruptly for vDMSO >0.8.•Breaking of multiple hydrogen bonds led to the conformation transition of AF1.The conformation transition of the short branched β-glucan AF1 isolated from Auricularia auricula-judae in DMSO/water solutions was investigated with viscometry and static/dynamic light scattering (SLS/DLS). AF1 in the mixed solution exhibited a sharp decrease in viscosity and molecular size in a narrow DMSO volume fraction (vDMSO) range of 0.80–1.0. It indicated that the stiff AF1 transformed into flexible chains probably, resulting from the destruction of intra- and inter-molecular hydrogen bonds of the polysaccharides. AF1 solutions with dialyzed treatment gave a more narrow transition range of 0.90–1.0. The conformation transition of AF1 was further conformed by transition electron microscopy (TEM) and atomic force microscopy (AFM). The multiple hydrogen bonds of polysaccharides affect the chain conformation, which in turn affect the application in food and pharmaceutical fields.

The catalytic transformation of the most abundant cellulose to valuable platform chemicals is one of the significant issues to overcome the shortage of fossil fuels. Herein, we reported the first example of Ru-based homogeneous catalyst for the highly selective conversion of cellobiose and ball-milled cellulose to hexitols (including sorbitol, mannitol, and 1,4-sorbitan) under an acidic condition with the yield of 94.5% and 56.4%, respectively. The main features of this catalytic system were the high conversion efficiency of biomass, mild reaction condition (100 °C), and low catalyst loading, which was 1/20 of the related Ru/C heterogeneous catalyst. This work opened up a new avenue for the transformation of cellulose to hexitols under mild conditions.

•A large-scale and efficient strategy was developed to fabricate carbon microsphere.•The carbon microspheres were consisted of robust cross-linked nanofibers.•The carbon microspheres displayed unique elasticity behaviors.•An outstanding rate capability carbon supercapacitors were readily fabricated.Chitin derived from discarded seafood waste (crab and shrimp shell) is a naturally abundant resource, but its difficult dissolubility limits the processing and applications. Herein, we prepared nanofibrous microspheres by using chitin solution dissolved in NaOH/urea aqueous solvent at low temperature, and subsequently fabricated the novel elastic nitrogen-doped carbon microspheres by pyrolyzing the chitin microspheres. Interestingly, the carbon microspheres were consisted of robust cross-linked nanofibers and displayed interconnected nanofibrous framework architecture, named as CNFF. The CNFF microspheres showed unique elasticity, excellent compression behaviors, and the morphology recovered completely over 5 cyclic compression at strain 75%. Moreover, the carbon microspheres exhibited an outstanding rate capability with a capacitance retention of ~50% when increase the scan rate from 5 mV/s to 10,000 mV/s as well as good cycling stability for supercapacitor applications, as a result of their hierarchical porosity, stable 3D interconnected mesh structure and ultrahigh specific surface area (over 1000 m2/g). Particularly, in the organic electrolyte, the highest deliverable energy density reached up to 58.7 Wh/kg. This work opened up a completely new and green avenue for constructing high performance carbon-based material with elasticity from biomass waste, showing promising application in the energy storage field.

To solve the problem of high temperature or long reaction time in hydrothermal synthesis of carbon dots (CDs), a novel method based on the promoting carbonization by hydrochloric acid as catalysis was developed in present work. The acid catalyzed carbon dots (ACDs) were prepared facilely from tryptophan and phenylalanine at 200 °C for 2 h. In our findings, the acids could promote significantly the formation of the ACDs’ carbon core, as a result of the accelerating of the carbonization due to the easy deoxidation. The ACDs showed an average size of 4.8 nm, and consisted of high carbon crystalline core and various surface groups. The ACDs exhibited good optical properties and pH-dependent photoluminescence (PL) intensities. Furthermore, the ACDs were safe and biocompatible. The experimental results demonstrated that such new ACDs were connected with DNA-aptamer by EDC/NHS reaction maintaining both the bright fluorescence and recognizing ability on the cancer cells, which so could be served as an effective PL sensing platform. The resultant DNA-aptamer with ACDs (DNA-ACDs) could stick to human breast cancer cells (MCF-7) specifically, and exhibited high sensitivity and selectivity, indicating the potential applications in the cancer cells targeted imaging fields.

High strength cellulose composite films with antibacterial activities were prepared by dispersing montmorillonites (MMT) into cellulose solution in LiOH/urea aqueous solvent followed by regeneration in ethanol coagulation bath, and then by soaking in 5 wt% hexadecylpyridine bromide ethanol solutions to induce the antibacterial action. The cellulose/MMT composite films were characterized by field emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, FTIR, UV-spectra, wide angle X-ray diffraction and mechanical test. The results revealed that MMT was dispersed well in the cellulose matrix to form layer structure with a thickness of approximately 3 nm. The mechanical properties of the cellulose/MMT composite films were significantly improved to achieve 132 MP for tensile strength as a result of the MMT delamination. The hexadecylpyridine bromide was fixed well in the cellulose/MMT matrix through cation exchange, leading to the excellent antibacterial activities against Staphylococcus aureus and Escherichia coli, which is important in their practical applications.

Wound dressing is of critical importance for wound repair, and the traditional cotton gauze derived from cellulose has commonly been used in clinical practice for a long time. However, cotton gauze does not possess active healing ability. To search for new wound dressings, in this work, a cellulose sponge was fabricated directly from a cellulose solution in a NaOH/urea aqueous system with cooling, and then cellulose/gelatin composite sponges were constructed successfully via a green and cost-effective pathway. The structure and physical properties of the sponges were characterized, and their cytocompatibility and in vivo wound healing ability were evaluated. The results indicated that, compared with cotton gauze, the cellulose sponge effectively promoted wound healing, as a result of the presence of macro- and micro-porous architecture. Furthermore, gelatin and basic fibroblast growth factor (bFGF) were immobilized in the cellulose sponge through hydrogen bonding to retain their inherent biocompatibility, leading to excellent repairing efficacy. In particular, for the full-thickness cutaneous wound model, the complete wound healing time for the wounds treated with bFGF-loaded cellulose sponges was 7 days faster than those treated with gauze. The pores with thin walls in the cellulose composite sponges played an important role in achieving the highly effective wound healing, which could fit the requirements of oxygen permeability, controlled water vapor evaporation and wound exudate absorption.

To resolve the problem of the pulverization and rapid capacity fading of polymer electrodes, novel electrode materials were constructed from polyaniline/cellulose microspheres (PANI/CM), which were fabricated via in situ synthesis of PANI on cellulose matrix by using phytic acid (PA) as a “bridge”, for the first time. The constructing of the PANI/PA/CM successfully resolved the problem of the pulverization of PANI to be used as electrode materials. In our findings, the PANI subparticles with nanomesh structure were dispersed homogeneously in the cellulose microspheres from inside to outside, as a result of the firm connection between the hydrophobic PANI and the hydrophilic cellulose through the PA “bridge” to create micro- and nano-porous architecture. Meanwhile, the other parts of PANI deposited on the surface of the microspheres to form a loose coralline structure, leading to the ion channels for the electrolyte penetration. The PANI/PA/CM composite electrodes exhibited excellent cycling stability (over 12000 cycles) and high rate capability, showing great potential for use in energy-storage devices.

Novel magnetic cellulose–TiO2 nanocomposite microspheres with high surface areas and magnetic susceptibility were fabricated, which exhibited remarkably selective enrichment of trace phosphopeptides from peptide mixtures.

•Cellulose/silver nanocomposite fibers were prepared by in situ synthesis of Ag nanoparticles in cellulose fibers through direct hydrothermal reduction.•The cellulose/silver nanocomposite fibers exhibited good mechanical properties and antibacterial properties.•The cellulose/silver nanocomposite fibers would have great potential in antibacterial textile and wound handling due to easy industrialization.We prepared cellulose/silver nanocomposite fibers by soaking the cellulose fibers in AgNO3 aqueous solution, which was heated at 80 °C for 24 h to synthesize Ag nanoparticles in situ. The structure and properties of the composite fibers were characterized by FT-IR, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmitting electron microscopy (TEM), thermo-gravimetric analysis (TGA) and tensile testing. The content and diameter of the Ag nanoparticles (NPs) increased from 0.15% to 2.40% and from 7.2 nm to 12.5 nm, respectively. In our findings, the pores of the cellulose fiber at wet state were used as a microreactor to synthesize Ag nanopariticles. The cellulose/Ag nanocomposite fibers exhibited good mechanical properties and thermal stability. Antibacterial experiment revealed excellent antibacterial activity of the cellulose nanocomposite fibers against Staphylococcus aureus. The cellulose/silver nanocomposite fibers would have great potential in antibacterial textile and wound handling due to easy industrialization.

Novel nanocomposite hydrogels composed of polyelectrolytes alginate and chitin whiskers with biocompatibility were successfully fabricated based on the pH-induced charge shifting behavior of chitin whiskers. The chitin whiskers with mean length and width of 300 and 20 nm were uniformly dispersed in negatively charged sodium alginate aqueous solution, leading to the formation of the homogeneous nanocomposite hydrogels. The experimental results indicated that their mechanical properties were significantly improved compared to alginate hydrogel and the swelling trends were inhibited as a result of the strong electrostatic interactions between the chitin whiskers and alginate. The nanocomposite hydrogels exhibited certain crystallinity and hierarchical structure with nanoscale chitin whiskers, similar to the structure of the native extracellular matrix. Moreover, the nanocomposite hydrogels were successfully applied as bone scaffolds for MC3T3-E1 osteoblast cells, showing their excellent biocompatibility and low cytotoxicity. The results of fluorescent micrographs and scanning electronic microscope (SEM) images revealed that the addition of chitin whiskers into the nanocomposite hydrogels markedly promoted the cell adhesion and proliferation of the osteoblast cells. The biocompatible nanocomposite hydrogels have potential application in bone tissue engineering.

The intra- and intermolecular interactions of chitin in NaOH/urea aqueous system were studied by a combination of NMR measurements (including 13C NMR, 23Na NMR, and 15N NMR) and differential scanning calorimetry. The results revealed that the NaOH and chitin formed a hydrogen-bonded complex that was surrounded by the urea hydrates to form a sheath-like structure, leading to the good dissolution. The optimal concentration range, in which chitin was molecularly dispersed in NaOH/urea aqueous, was found to investigate the chain conformation in the dilute solution with a combination of static and dynamic light scattering. The weight-average molecular weight (Mw), radii of gyration (⟨Rg⟩z), and hydrodynamic radii (⟨Rh⟩z) values of chitin were determined, and the structure-sensitive parameter (ρ) and persistent length (Lp) were calculated to be >2.0 and ∼30 nm, respectively, suggesting an extended wormlike chain conformation. The visualized images from TEM, cryo-TEM, and AFM indicated that, chitin nanofibers were fabricated from the parallel aggregation of chitin chains in NaOH/urea system. This work would provide a theoretical guidance for constructing novel chitin-based nanomaterials via “bottom-up” method at the molecular level.

Breaking the limitation of traditional acid dissolving methods for chitosan by creating an alkali/urea hydrogen-bonded chitosan complex, a new solvent (4.5 wt % LiOH/7 wt % KOH/8 wt % urea aqueous solution) was used to successfully dissolve chitosan via the freezing–thawing process, for the first time. Subsequently, high strength hydrogels with unique nanofibrous architecture were constructed from the chitosan alkaline solution. The results from 13C NMR, laser light scattering, atomic force microscopy, transmission electron microscopy, and scanning electron microscopy confirmed that chitosan easily aggregated in the solution and could self-assemble in parallel to form perfect regenerated nanofibers induced by heating. At elevated temperature and concentration, the regenerated chitosan nanofibers could entangle and cross-link with each other through hydrogen bonds to form hydrogels. The novel chitosan hydrogels exhibited homogeneous architecture and high strength as a result of the strong networks woven with the compact nanofibers. The compression fracture stress of the chitosan hydrogels was nearly 100 times that of the chitosan hydrogels prepared by the traditional acid dissolving method, revealing that the nanofibrous network microstructures contributed greatly to the reinforcement of the hydrogels. Furthermore, the chitosan hydrogels exhibited excellent biocompatibility and safety as well as a smart controlled drug release behavior triggered by acid. Therefore, we opened up a completely new avenue to construct high strength chitosan hydrogels for applications in biomedicine.

The fabrication of reusable and biodegradable materials from renewable resources such as chitin is essential for a sustainable world. In the present work, chitin was dissolved in 11 wt% NaOH–4 wt% urea aqueous solution via freezing–thawing, and then chitin microspheres (RChS) were prepared by a sol–gel transition method. Subsequently, novel magnetic Ag–Fe3O4@chitin microspheres (MRChS) were constructed successfully by an in situ one-pot synthesis of Ag–Fe3O4 nanoparticles onto the RChS surface. The magnetic chitin microspheres displayed a spherical shape with a 3D-mesh structure, and had a narrow size distribution (150–400 μm). There were many micro- and nano-pores existing in MRChS, and the Ag–Fe3O4 nanoparticles were immobilized through anchoring with the acetyl amine groups of chitin in these pores. The MRChS microspheres were used as a chromatography column packing material for a “catalytic reaction column”, and exhibited highly effective catalytic activity in the rapid transformation from 4-nitrophenol to 4-aminophenol. Moreover, the microspheres displayed a small hysteresis loop and low coercivity, as well as high turnover frequency (at least 10 times) without any loss of catalytic activity. Thus, MRChS could be quickly removed from the water under a magnetic field, leading to easy recycling and reuse. Therefore, this is an environmentally friendly process, and would be highly beneficial to address industrial requirements.

For the first time, novel polyaniline (PANI)–cellulose filament fibers have been successfully spun from hydrophobic PANI and hydrophilic cellulose complex solution dissolved in aqueous containing 7 wt% NaOH/12 wt% urea as the solvent by wet-spinning. The composite fibers had a circular cross-section and homogenous surface structure, as a result of good miscibility between PANI and cellulose associated through hydrogen bonds. Moreover, at low PANI content, the composite fibers realized a transition from an insulator to a semiconductor. This work has provided a simple and eco-friendly avenue for the production of PANI composite fibers that have great potential applications in the antistatic textile and military industries.

For the first time, pure chitin fibers with relatively high strength, lustrous surface and circular cross section were spun directly from chitin solution dissolved in an NaOH–urea aqueous system with freezing. Subsequently, chitin nonwoven fabrics were constructed from the fresh wet fibers by hot pressing, and tested as wound dressings, showing excellent ability to accelerate healing, owing to the retainment of the intrinsic α-chitin structure.

Bioimaging is a key technique for monitoring behavior and activity in vivo and plays an important role in the life science and medical fields. In the present work, for the first time, a new, safe cellulose based hybrid hydrogel was constructed from a cellulose solution containing rare-earth doped phosphor (PP) in an alkali/urea aqueous system using epichlorohydrin as a crosslinker. Its structure and properties were characterized by wide angle X-ray diffraction, FT-IR spectra, solid-state 13C NMR, field emission scanning electron microscopy, UV-vis spectroscopy, fluorescence spectra, and compression tests. The results indicated that the PP particles were tightly embedded in the macroporous cellulose matrix, which not only supplied cavities for PP immobilization through relatively strong intermolecular hydrogen bonding interactions, but also supplied the pore wall as a shell to protect the structure and character of PP. Thus, the cellulose/PP hybrid (CPH) hydrogels emitted relatively strong green fluorescence under a UV lamp, as well as high brightness and long-lasting afterglow. This could avoid harmful radiation in the body and improve signal resolution with lower cell autofluorescence interference. Notably, CPH with strong afterglow could be detected both under the skin and in the stomach with and without excitation light, showing promising prospects as a candidate for bioimaging. Moreover, the hybrid hydrogels exhibited good compressive strength and processability.

A highly hydrophobic and oleophilic chitin sponge was synthesized, for the first time, via a freeze-dried method and then by using a thermal chemical vapor deposition of methyltrichlorosilane (MTCS) at different relative humidity. Fourier-transform infrared, energy-dispersive X-ray spectra, and scanning electron microscopy confirmed that the silanization occurred on the pore wall surface of the chitin sponge. The MTCS-coated chitin sponge had interconnected open-cell structures with the average pore size from 20 to 50 μm, and the MTCS nanofilaments immobilized on the chitin matrix, leading to the high hydrophobicity, as a result of the existence of a solid/air composite rough surface. Cyclic compression test indicated that the hydrophobic chitin sponges exhibited excellent elasticity and high mechanical durability. The sponges could efficiently collect organics both on the surface and bottom from the water with the highest 58 times of their own weight absorption capacities through the combination of the particular wettability and great porosity. Furthermore, the biodegradation kinetics of the chitin sponge forecasted that the chitin could be completely biodegraded within 32 days by the microorganisms in the soil. This work provided a new pathway to prepare the chitin-based materials for highly effective removal of oil from water, showing potential application in the pollutant remediation field.Keywords: biodegradability; chitin sponge; high hydrophobicity; oil absorption and separation; solid/air surface; surface modification

Novel onion-like and multi-layered tubular cellulose hydrogels were constructed, for the first time, from the cellulose solution in a 7% NaOH/12% urea aqueous solvent by changing the shape of the gel cores. In our findings, the contacting of the cellulose solution with the surface of the agarose gel rod or sphere loaded with acetic acid led to the close chain packing to form immediately a gel layer, as a result of the destruction of the cellulose inclusion complex by acid through inducing the cellulose self-aggregation. Subsequently, multi-layered cellulose hydrogels were fabricated via a multi-step interrupted gelation process. The size, layer thickness and inter-layer space of the multi-layered hydrogels could be controlled by adjusting the cellulose concentrations, the gel core diameter and the contacting time of the solid–liquid interface. The multi-layered cellulose hydrogels displayed good architectural stability and solvent resistance. Moreover, the hydrogels exhibited high compressive strength and excellent biocompatibility. L929 cells could adhere and proliferate on the surface of the layers and in interior space, showing great potential as tissue engineering scaffolds and cell culture carrier. This work opens up a new avenue for the construction of the high strength multi-layered cellulose hydrogels formed from inner to outside via a fast contact of solid–liquid interface.Keywords: biocompatibility; high compressive strength; interfacial interaction; multi-layered cellulose hydrogel; scaffold material;

As one of the most ordinary phenomena in nature, numerous pores on animal skins induce the growth of abundant hairs. In this study, cavities of a cellulose matrix were used as hard templates to lead the hair-inspired crystal growth of 12-hydroxyoctadecanoic acid (HOA) through hydrophobic–hydrophilic interface interaction, and short hair-like HOA crystals with a smooth surface were formed on cellulose films. In our findings, by using solvent evaporation induced crystallization, hydrophobic HOA grew along the hydrophilic cellulose pore wall to form regular vertical worm-like and pillar-like crystals with an average diameter of about 200 nm, depending on the experimental conditions and HOA concentration. The formation mechanism of the short hair-like HOA crystals as well as the structure and properties of the cellulose/HOA submicrometer composite films were studied. The pores of the cellulose matrix supplied not only cavities for the HOA crystals fixation but also hydrophilic shells to favor the vertical growth of the relatively hydrophobic HOA crystals. The cellulose/HOA submicrometer composite films exhibited high hydrophobicity, as a result of the formation of the solid/air composite surface. Furthermore, 4-(1,2,2-triphenylethenyl) benzoic acid, an aggregation-induced emission luminogen, was used to aggregate on the cellulose surface with HOA to emit and monitor the HOA crystal growth, showing bifunctional photoluminscence and self-cleaning properties. This work opens up a novel one-step pathway to design bio-inspired submicrometer materials by utilizing natural products, showing potential applications in self-cleaning optical devices.Keywords: aggregation-induced emission (AIE); hair-inspired crystal growth; hydrophobic−hydrophilic interface; porous cellulose matrix;

On the basis of the requirements for both biobased economy and energy storage materials, we are interested in using cellulose-based microporous film as a template for in situ synthesis of polyaniline (PANI). Multifunctional carbon nanotube (CNT)/cellulose composite films were also prepared from a CNT/cellulose suspension in a NaOH/urea aqueous system. Subsequently, PANI was synthesized in situ in the pores of cellulose and CNT/cellulose substrates to construct PANI/cellulose (PC) films and PANI/CNT/cellulose (PCC) films, respectively. Both PC and PCC films were flexible and exhibited a highly specific capacitance and good cycle stability. With the addition of CNTs, the specific capacitance of the PCC films as supercapacitor materials was significantly improved. Moreover, a homogeneous structure intertwined with the cellulose, CNTs and PANI appeared in the composite films, indicating good miscibility. This work has provided a new approach to the fabrication of flexible, lightweight, highly effective, and low-cost energy storage materials, broadening the applications of cellulose.

For the first time, portable visible-light photocatalysts were fabricated by in situ synthesizing Cu2O in the micropores of regenerated cellulose (RC)/graphene oxide (GO) composite films, in which the porous matrix was used as a microreactor for the formation of Cu2O nanoparticles. Cu2O nanoparticles were immobilized and evenly distributed in the RC matrix to excite and generate free photoelectrons and electron holes, leading to the high photodegradation efficiency against methyl orange dye under visible-light irradiation. Moreover, the introduction of GO has dramatically improved the photocatalytic activities of Cu2O nanoparticles in the Cu2O/GO/RC nanocomposite films, leading to a significant enhancement of the photodegradation rate from 2.0 to 6.5 mg h–1 gcat–1. In the Cu2O/GO/RC photocatalysts, Cu2O nanoparticles inside the matrix tended to generate on the GO sheets, which transferred the yielded photoelectrons to prevent local high potential zone generation and to induce the chain degradation reaction at more points, leading to the improvement of the photocatalyst activity. Moreover, the portable photocatalysts could be easily recycled and reused, showing great potential applications for wastewater purification by utilizing solar energy.

Triple helical polysaccharides (t-polysaccharides) are easily gelated in water, resulting in difficult fractionation, leading to the complex and time-consuming chain conformational characterization. Moreover, the fractionation is not always successful due to the coexistence of individual chains and aggregates. In this work, we developed a facile and reliable method to rapidly and accurately characterize the chain conformation of t-polysaccharide without fractionation needed in traditional conformation characterization. A triple helical β-1,3-glucan (t-β-1,3-glucan), extracted from the fruiting bodies of Lentinus edodes, was identified to consist of a β-1,3-glucan with two β-1,6-d-glucopyranoside branchings for every five β-1,3-glucopyranoside linear linkages by one- and two-dimensional NMR and GC-MS analysis. The chain conformations of the t-β-glucan in aqueous solution and in DMSO were successfully characterized by a combination of size exclusion chromatography (SEC), multiangle static light scattering, a differential refractometer, and a capillary viscosity detector (triple-detector SEC). The results revealed that the predominate species of the t-β-glucan in a 0.15 M NaCl aqueous solution existed as a triple helical conformation with high chain stiffness, and a few aggregates (4%) coexisted here. The Mark–Houwink and ⟨S2⟩1/2 versus Mw equations of individual triple helical chains and aggregates were obtained simultaneously, and the results confirmed again the coexistence of two kinds of chain conformations. The fractal dimension indicated that the aggregate in the aqueous solution was a kind of reversible microgel with a 3D network structure. Furthermore, the chain morphology of the t-β-glucan in aqueous solution was observed directly by transmission electron microscopy and atomic force microscopy to support the worm-like chain for the individuals and 3D network for the aggregates. The triple-detector SEC technology was facile and reliable for the system with two fractions of different chain conformation, and the test time required was only 1/30 of what the traditional method needed.

The dissolution of cellulose in NaOH/urea aqueous solution at low temperature is a key finding in cellulose science and technology. In this paper, 15N and 23Na NMR experiments were carried out to clarify the intermolecular interactions in cellulose/NaOH/urea aqueous solution. It was found that there are direct interactions between OH– anions and amino groups of urea through hydrogen bonds and no direct interaction between urea and cellulose. Moreover, Na+ ions can interact with both cellulose and urea in an aqueous system. These interactions lead to the formation of cellulose–NaOH–urea–H2O inclusion complexes (ICs). 23Na relaxation results confirmed that the formation of urea–OH– clusters can effectively enhance the stability of Na+ ions that attracted to cellulose chains. Low temperature can enhance the hydrogen bonding interaction between OH– ions and urea and improve the binding ability of the NaOH/urea/H2O clusters that attached to cellulose chains. Cryo-TEM observation confirmed the formation of cellulose–NaOH–urea–H2O ICs, which is in extended conformation with mean diameter of about 3.6 nm and mean length of about 300 nm. Possible 3D structure of the ICs was proposed by the M06-2X/6-31+G(d) theoretical calculation, revealing the O3H···O5 intramolecular hydrogen bonds could remain in the ICs. This work clarified the interactions in cellulose/NaOH/urea aqueous solution and the 3D structure of the cellulose chain in dilute cellulose/NaOH/urea aqueous solution.

High strength chitin/poly(vinyl alcohol) (PVA) composite hydrogels (RCP) were constructed by adding PVA into chitin dissolved in a NaOH/urea aqueous solution, and then by cross-linking with epichlorohydrin (ECH) and freezing–thawing process. The RCP hydrogels were characterized by field emission scanning electron microscopy, FTIR, differential scanning calorimetry, solid-state 13C NMR, wide-angle X-ray diffraction, and compressive test. The results revealed that the repeated freezing/thawing cycles induced the bicrosslinked networks consisted of chitin and PVA crystals in the composite gels. Interestingly, a jellyfish gel-like structure occurred in the RCP75 gel with 25 wt % PVA content in which the amorphous and crystalline PVA were immobilized tightly in the chitin matrix through hydrogen bonding interaction. The freezing/thawing cycles played an important role in the formation of the layered porous PVA networks and the tight combining of PVA with the pore wall of chitin. The mechanical properties of RCP75 were much higher than the other RCP gels, and the compressive strength was 20× higher than that of pure chitin gels, as a result of broadly dispersing stress caused by the orderly multilayered networks. Furthermore, the cell culture tests indicated that the chitin/PVA composite hydrogels exhibited excellent biocompatibility and safety, showing potential applications in the field of tissue engineering.

A water soluble β-d-glucan was isolated by 70% ethanol aqueous solution from Auricularia auricula-judae, coded as AAG. AAG exhibited strong inhibition against Acinar cell carcinoma (ACC) proliferation. The in vivo tests showed that AAG significantly inhibited tumor growth in a dose-dependent fashion, but not because of cytotoxicity. All the doses showed certain inhibition ratios against tumor-cell growth, while the dose of 20 mg/kg exhibited highest anti-tumor activities. Moreover, the enhancement ratios of body weight for all the doses were significantly higher than that for 5-fluorouracil (5-Fu). Fluorescence microscopy observed the apoptosis tumor cell induced by AGG sample. The results from TUNEL assay further confirmed the apoptosis in Sarcoma 180 solid tumor. Immunohistochemistry for apoptosis-related proteins Bax and Bcl-2 expression tests revealed that AAG induced S-180 tumor cell apoptosis by up-regulation of Bax and down-regulation of Bcl-2 expression. These findings demonstrated that the AAG has biological activities and could be considered as a candidate for possible anti-tumor drugs.

•Regulated-photoluminescence cellulose gels are prepared with lanthanide elements.•The color of the luminescence can be modulated.•It has potential applications in the fields of bioimaging and fluoroimmunoassay.In this study cellulose hydrogels with lanthanide ions nanoparticles embedded in were prepared via in situ doping using a low-temperature alkali hydroxide/urea aqueous solution as a cellulose solvent. Depending on the type and relative concentrations of the constituent lanthanide ions, the color of light emission were modulated to generate the three primary colors and other adjusted colors by blending red, green and blue at certain ratios. This work has opened new and convenient pathway to create regulated fluorescent cellulose hydrogels for potential applications in the fields of bioimaging and fluoroimmunoassay.

Weak interactions, though sometimes easily ignored, play an important role in macromolecule dissolution. In this work, the characterization of weak interactions between urea and cellulose in a LiOH/urea aqueous solution was accomplished and confirmed in situ, for the first time, using PFG-SE NMR, FT-IR and solvatochromic methods, etc. The NMR results indicated the binding of urea with cellulose in the solution, demonstrating the existence of the weak interactions between them. Subsequently, the solvatochromic methods revealed that urea hardly affected the hydrogen bond donor (HBD acidity) and hydrogen bond acceptor (HBA basicity) properties of the solvent, but was related to its dipolarity and polarizability, indicating that dispersion forces existed therein, but not likely hydrogen bonding, which was also supported by the FT-IR. Furthermore, the impact of weak interactions between urea and cellulose was demonstrated to facilitate the dissolving process. The fine dispersion and good stability of cellulose in the solution were maintained by mitigating the effect of the hydrophobic portions from all the dilute, semi-dilute and concentrated regimes, supported by the results of dynamic light scattering (DLS), rheology, NMR, etc. Therefore, the transmittance and mechanical properties of the regenerated cellulose materials prepared from the cellulose solution in the alkali/urea aqueous system were enhanced, compared with those in the alkali only system. This work provided significant and new experimental insights into the non-covalent weak interactions between urea and macromolecules from the viewpoints of polymer physics and physical chemistry, which could never be ignored and underestimated. The indispensable weak interactions in the system are also important for the green conversion of natural biomass into new materials via physical processes.

As a breakthrough to the traditional 1H diffusometry, the interaction of cations with cellulose is investigated via7Li and 23Na PFG-SE NMR. The diffusion coefficient of Li+ decreases more than that of Na+ with the addition of cellulose, which indicates a stronger binding of LiOH with the macromolecule. Therefore, a new, facile, accurate and repeatable method to characterize ion/polymer interactions is established.

Mushrooms are known as a delicacy due to their delicious taste and rich nutrition, and their β-glucans have antitumor activity. Here, a triple helical β-glucan (THG) isolated from Lentinus edodes was successfully fractionated into nine fractions with different weight-average molecular weights (Mw) through ultrasonic irradiation. The Mw, radius of gyration (〈Rg〉z), hydrodynamic radius (〈Rh〉z), structure-sensitive parameters (ρ), contour length (L), persistence length (q) and molar mass per contour length (ML) were characterized by static light scattering (SLS), dynamic light scattering (DLS), and atomic force microscopy (AFM). The results indicated that THG displayed an extended chain conformation with ρ values of 2.1 ± 0.1 for the nine fractions, as well as ML and q values of 2160 nm−1 and 110 nm in water, which were consistent with the data for triple helical polysaccharides. In combination with the apparent length (Lap) values visualized with AFM and Mw, the molar mass per apparent contour length (MLap) was calculated to be 2242 nm−1, which was similar to that obtained from SLS according to the wormlike cylinder model. Thus, we established a novel method using AFM for characterizing the chain stiffness of polysaccharides. The results from an animal assay demonstrated that THG significantly inhibited H22 tumor growth without damage to organisms, and the THG fractions with relatively low molecular weight and/or higher stiffness showed stronger antitumor activity, revealing the significant molecular weight- and chain conformation-dependences of antitumor activity. Moreover, a schematic model to describe the interaction between THG and receptors on the immune cell membrane was proposed to illustrate these results. This work provides important information for characterizing the chain conformation of polysaccharides and understanding the relationship between structure and antitumor activity, which is relevant for the treatment of hepatocellular carcinoma in clinic.

Dendritic nanotubes (DNTs) with hydrophobic cavities were constructed directly from rigid branched β-1,3-D-glucan (AF1) in aqueous solution, and the AF1 sample was isolated from the fruiting bodies of Auricularia auricula-judae, a household nutritional food. The structure of AF1 dendritic nanotubes was demonstrated with a transmission electron microscope (TEM) and a scanning electron microscope (SEM), and a schematic diagram was proposed to describe the formation process, which was supported by the results of static/dynamic light scattering (SLS/DLS) and atomic force microscopy (AFM). In solution, a sequential self-assembly of the AF1 chains in a parallel manner occurred to form lamellas followed by self-curling into nanotubes with the mean diameters from 20 to 80 nm, depending on the concentration and molecular weight of AF1, through hydrogen bonding and hydrophilic/hydrophobic interaction. As a result of the dendritic structure, the AF1 aggregates exhibited highly condensed hydrophobic regions, which could be used as carriers to achieve a high concentration of the target molecules. In our findings, the anticancer drug DOX and the fluorescent probe TPA-BMO could be loaded into the hydrophobic region of DNTs. Interestingly, DOX-loaded DNTs of AF1 exhibited high drug loading capacity and pH-triggered sustained release behaviors (>23 days) with reduced cytotoxicity in vitro. Moreover, the bioimaging experiment demonstrated that TPA-BMO-loaded DNTs of AF1 induced stronger fluorescence intensity than TPA-BMO alone, and maintained a longer duration time (18 days) in vivo. Therefore, the DNTs of AF1 have promising applications as bioactive carriers, especially in the fields of drug delivery and bioimaging.

Excess bilirubin often evokes hepatobiliary system dysfunction. In the present work, we developed an efficient, safe and blood compatible adsorbent for bilirubin removal from human blood. In view of the highly effective adsorption of carbon nanotubes (CNTs) on bilirubin but with many side effects, and good biocompatibility of chitin but with low efficiency for bilirubin removal, new chitin/carbon nanotube (Ch/CNT) nanofibrous microspheres were constructed from chitin solution in NaOH/urea aqueous system by blending with CNTs. The results of AFM, SEM, and TEM demonstrated that the CNTs were dispersed well in the chitin matrix, and the chitin nanofibers intertwined with CNTs to form hybrid chitin/CNT nanofibers and then weaved into a 3D interconnected network architecture. Moreover, lysine (Lys), a highly specific ligand for bilirubin, was immobilized tightly to the hybrid microspheres to obtain Ch/CNT/Lys. The resultant microspheres possessed large surface area and hierarchical pores including mesopores and micropores, which could allow bilirubin to enter easily and store, leading to highly efficient adsorption. The Ch/CNT/Lys microspheres exhibited excellent bilirubin adsorption property (107.2 mg g−1) and efficient bilirubin clearance rate from real hyperbilirubinemia plasma competing with protein, as well as good cell affinity and blood compatibility, as a result of the combination of the high adsorption of CNTs and inherent biocompatibility of chitin and lysine. Therefore, an effective strategy to develop a novel biocompatible and blood compatible bilirubin adsorbent is provided, showing potential applications for hemoperfusion in blood purified therapy.

Novel magnetic cellulose–TiO2 nanocomposite microspheres with high surface areas and magnetic susceptibility were fabricated, which exhibited remarkably selective enrichment of trace phosphopeptides from peptide mixtures.

To resolve the problem of the pulverization and rapid capacity fading of polymer electrodes, novel electrode materials were constructed from polyaniline/cellulose microspheres (PANI/CM), which were fabricated via in situ synthesis of PANI on cellulose matrix by using phytic acid (PA) as a “bridge”, for the first time. The constructing of the PANI/PA/CM successfully resolved the problem of the pulverization of PANI to be used as electrode materials. In our findings, the PANI subparticles with nanomesh structure were dispersed homogeneously in the cellulose microspheres from inside to outside, as a result of the firm connection between the hydrophobic PANI and the hydrophilic cellulose through the PA “bridge” to create micro- and nano-porous architecture. Meanwhile, the other parts of PANI deposited on the surface of the microspheres to form a loose coralline structure, leading to the ion channels for the electrolyte penetration. The PANI/PA/CM composite electrodes exhibited excellent cycling stability (over 12000 cycles) and high rate capability, showing great potential for use in energy-storage devices.

For the first time, novel polyaniline (PANI)–cellulose filament fibers have been successfully spun from hydrophobic PANI and hydrophilic cellulose complex solution dissolved in aqueous containing 7 wt% NaOH/12 wt% urea as the solvent by wet-spinning. The composite fibers had a circular cross-section and homogenous surface structure, as a result of good miscibility between PANI and cellulose associated through hydrogen bonds. Moreover, at low PANI content, the composite fibers realized a transition from an insulator to a semiconductor. This work has provided a simple and eco-friendly avenue for the production of PANI composite fibers that have great potential applications in the antistatic textile and military industries.

The water soluble β-(1 → 3)-D-glucan with short branches (AF1) isolated from Auricularia auricula-judae was successfully fractionated by ultrasonication into three fractions with different weight-average molecular weights (Mws). The results of static and dynamic laser light scattering, viscometry and atomic force microscopy confirmed that the AF1 samples adopted a stiff chain conformation in water, and the coexistence of individuals and aggregates occurred gradually with increasing concentration. The AF1 sample with the highest Mw easily self-entangled, and exhibited a strong shear rate-dependence of viscosity in water. The glucans displayed anti-hepatoma activity and significantly inhibited H22 tumour growth without cytotoxicity towards normal tissues. They displayed both molecular weight- and dosage-dependencies of anti-tumour activity, and the sample with an Mw of 7.7 × 105 at the dosage of 5 mg kg−1 exhibited the highest inhibition ratio of ∼77% against H22 tumour, even significantly higher than the positive control of cytoxan. The immunohistochemical and western blot analyses revealed that the AF1 glucans triggered cell apoptosis, indicated by the activation of caspase 3/9 and down-regulated tumour angiogenesis factors of VEGF and CD31. The underlying antitumor mechanism was suggested to induce tumour cell apoptosis and to inhibit angiogenesis in tumour tissues via enhancement of the immune-response. Taken together, the AF1 β-glucan was a potent natural drug candidate with high anti-cancer activities and less cytotoxicity, and the AF1 sample with a moderate molecular weight existed in aqueous solution as a more extended chain conformation, which plays an important role in activating immune responses.

Wound dressing is of critical importance for wound repair, and the traditional cotton gauze derived from cellulose has commonly been used in clinical practice for a long time. However, cotton gauze does not possess active healing ability. To search for new wound dressings, in this work, a cellulose sponge was fabricated directly from a cellulose solution in a NaOH/urea aqueous system with cooling, and then cellulose/gelatin composite sponges were constructed successfully via a green and cost-effective pathway. The structure and physical properties of the sponges were characterized, and their cytocompatibility and in vivo wound healing ability were evaluated. The results indicated that, compared with cotton gauze, the cellulose sponge effectively promoted wound healing, as a result of the presence of macro- and micro-porous architecture. Furthermore, gelatin and basic fibroblast growth factor (bFGF) were immobilized in the cellulose sponge through hydrogen bonding to retain their inherent biocompatibility, leading to excellent repairing efficacy. In particular, for the full-thickness cutaneous wound model, the complete wound healing time for the wounds treated with bFGF-loaded cellulose sponges was 7 days faster than those treated with gauze. The pores with thin walls in the cellulose composite sponges played an important role in achieving the highly effective wound healing, which could fit the requirements of oxygen permeability, controlled water vapor evaporation and wound exudate absorption.

Bioimaging is a key technique for monitoring behavior and activity in vivo and plays an important role in the life science and medical fields. In the present work, for the first time, a new, safe cellulose based hybrid hydrogel was constructed from a cellulose solution containing rare-earth doped phosphor (PP) in an alkali/urea aqueous system using epichlorohydrin as a crosslinker. Its structure and properties were characterized by wide angle X-ray diffraction, FT-IR spectra, solid-state 13C NMR, field emission scanning electron microscopy, UV-vis spectroscopy, fluorescence spectra, and compression tests. The results indicated that the PP particles were tightly embedded in the macroporous cellulose matrix, which not only supplied cavities for PP immobilization through relatively strong intermolecular hydrogen bonding interactions, but also supplied the pore wall as a shell to protect the structure and character of PP. Thus, the cellulose/PP hybrid (CPH) hydrogels emitted relatively strong green fluorescence under a UV lamp, as well as high brightness and long-lasting afterglow. This could avoid harmful radiation in the body and improve signal resolution with lower cell autofluorescence interference. Notably, CPH with strong afterglow could be detected both under the skin and in the stomach with and without excitation light, showing promising prospects as a candidate for bioimaging. Moreover, the hybrid hydrogels exhibited good compressive strength and processability.

For the first time, pure chitin fibers with relatively high strength, lustrous surface and circular cross section were spun directly from chitin solution dissolved in an NaOH–urea aqueous system with freezing. Subsequently, chitin nonwoven fabrics were constructed from the fresh wet fibers by hot pressing, and tested as wound dressings, showing excellent ability to accelerate healing, owing to the retainment of the intrinsic α-chitin structure.