Pickering Emulsions and Hydrophobized Films of Amphiphilic Cellulose Nanofibers Synthesized in Deep Eutectic Solvent

Herein, a dual-functioning deep eutectic solvent system based on triethylmethylammonium chloride and imidazole was harnessed as a swelling agent and a reaction medium for the esterification of cellulose with n-octyl succinic anhydride (OSA). The modified or amphiphilic cellulose nanofibers (ACNFs), synthesized using three different OSA-to-anhydroglucose unit molar ratios (0.5:1, ACNF-1; 1:1, ACNF-2; and 1.5:1, ACNF-3), were further converted into nanofibers with degree of substitution (DS) values of 0.24-0.66. The ACNFs possessed a lateral dimension of 4.24-9.22 nm and displayed surface activity due to the balance of hydrophobic and hydrophilic characteristics. The ACNFs made stable aqueous dispersions; however, the instability index of ACNF-3 (0.51) was higher than those of ACNF-1 (0.29) and ACNF-2 (0.33), which was attributed to the high DS-induced hydrophobicity, causing the instability in water. The amphiphilic nature of ACNFs promoted their performance as stabilizers in oil-in-water Pickering emulsions with average droplet sizes of 4.85 μm (ACNF-1) and 5.48 μm (ACNF-2). Self-standing films of ACNFs showed high contact angles for all the tested DS variants (97.48-114.12°), while their tensile strength was inversely related to DS values (ACNF-1: 115 MPa and ACNF-3: 49.5 MPa). Aqueous dispersions of ACNFs were also tested for coating fruits to increase their shelf life. Coatings improved their shelf life by decreasing oxygen contact and moisture loss.

Role of silica-based porous cellulose nanocrystals in improving water absorption and mechanical properties

Epoxy resins are important thermosetting polymers. They are widely used in many applications i.e., adhesives, plastics, coatings and sealers. Epoxy molding compounds have attained dominance among common materials due to their excellent mechanical properties. The sol-gel simple method was applied to distinguish the impact on the colloidal time. The properties were obtained with silica-based fillers to enable their mechanical and thermal improvement. The work which we have done here on epoxy-based nanocomposites was successfully modified. The purpose of this research was to look into the effects of cellulose nanocrystals (CNCs) on various properties and applications. CNCs have recently attracted a lot of interest in a variety of industries due to their high aspect ratio, and low density which makes them perfect candidates. Adding different amounts of silica-based nanocomposites to the epoxy system. Analyzed with different techniques such as Fourier-transformed infrared spectroscope (FTIR), thermogravimetric analysis (TGA) and scanning electronic microscopic (SEM) to investigate the morphological properties of modified composites. The various %-age of silica composite was prepared in the epoxy system. The 20% of silica was shown greater enhancement and improvement. They show a better result than D-400 epoxy. Increasing the silica, the transparency of the films decreased, because clustering appears. This shows that the broad use of CNCs in environmental engineering applications is possible, particularly for surface modification, which was evaluated for qualities such as absorption and chemical resistant behavior.

Fast Response and Visual Transparency Switching Hydrochromic Film Based on the Rational Structure of Cellulose/Poloxamer Copolymers Design for Smart Window

The authors are motivated to develop a series of hydrochromic copolymers with fast response, reversibility, repeatability, and visual transparency transition. The hydrochromic block copolymers are based on the rational ratio of hydrophilic segments of poloxamer block and hydrophobic segments of ethyl cellulose according to the preparation method of polyurethane. By tuning the ratio of hydrophilic segments or adding hygroscopic salts, the hydrochromic polymer is endowed with the ability to visualize the transparency in response to the relative humidity. Especially, the response time of the polymer is extremely shortened, up to 1 s for the optimized sample. Within the moisture stimulation, the hygroscopic swelling increases the film thickness, leading to a reversible transparency switching from a highly transparent state (82%) to an opaque white state (20.5%).

SCOBY Cellulose Modified with Apple Powder-Biomaterial with Functional Characteristics

The need for new non-animal and non-petroleum-based materials is strongly emphasized in the sustainable and green economy. Waste materials have proven a valuable resource in this regard. In fact, there have been quite a large number of goods obtained from wastes called "Vegan leather" that have gained the clothing market's attention in recent years. In practice, they are mostly composites of waste materials like cactus, pineapples, or, eventually, apples with polymers like polyurethane or polyvinyl chloride. The article presents the results of work aimed at obtaining a material based entirely on natural, biodegradable raw materials. Bacterial cellulose produced as a byproduct of the fermentation carried out by SCOBY was modified with glycerol and then altered by the entrapment of apple powder. The effect of introducing apple powder into the SCOBY culture media on the mechanical properties of the obtained bacterial cellulose was also evaluated The resulting material acquired new mechanical characteristics that are advantageous in terms of strength. Microscopic observation of the apple powder layer showed that the coverage was uniform. Different amounts of apple powder were used to cover the cellulose surface from 10 to 60%, and it was found that the variant with 40% of this powder was the most favorable in terms of mechanical strength. Also, the application of the created material as a card folder showed that it is durable in use and retains its functional characteristics for at least 1 month. The mechanical properties of modified bacterial cellulose were favorably affected by the entrapment of apple powder on its surface, and as a result, a novel material with functional characteristics was obtained.

Highly efficient microencapsulation of phytonutrients by fractioned cellulose using biopolymer complexation technology

A poorly water soluble polar and non-polar bioactive complexes encapsulated in a nanocellulose-based polymeric network are the focus of this research. Ascorbic acid, resveratrol, holy basil extract, pomegranate extract, and niacin are all microencapsulated bioactive complexes that make up Zetalife^®, a nutritional ingredient. It uses an interpenetrating polymeric network (IPN) with more dispersed nanocellulose and phospholipids to increase Zetalife^® s bioavailability. Field Emission Scanning Electron Microscopic (FESEM) images were used in studying the morphology of encapsulated bioactive molecules. The average microbead size was determined to be 244.2 nm. After each month of storage, the sample's microbial content was measured to assess stability. In vitro release followed a first-order kinetic model with high R².

Synthesis and Characterization of Cellulose Triacetate Obtained from Date Palm (Phoenix dactylifera L.) Trunk Mesh-Derived Cellulose

Cellulosic polysaccharides have increasingly been recognized as a viable substitute for the depleting petro-based feedstock due to numerous modification options for obtaining a plethora of bio-based materials. In this study, cellulose triacetate was synthesized from pure cellulose obtained from the waste lignocellulosic part of date palm (Phoenix dactylifera L.). To achieve a degree of substitution (DS) of the hydroxyl group of 2.9, a heterogeneous acetylation reaction was carried out with acetic anhydride as an acetyl donor. The obtained cellulose ester was compared with a commercially available derivative and characterized using various analytical methods. This cellulose triacetate contains approximately 43.9% acetyl and has a molecular weight of 205,102 g·mol⁻¹. The maximum thermal decomposition temperature of acetate was found to be 380 °C, similar to that of a reference sample. Thus, the synthesized ester derivate can be suitable for fabricating biodegradable and “all cellulose” biocomposite systems.

Surface Modification of Bacterial Cellulose for Biomedical Applications

Bacterial cellulose is a naturally occurring polysaccharide with numerous biomedical applications that range from drug delivery platforms to tissue engineering strategies. BC possesses remarkable biocompatibility, microstructure, and mechanical properties that resemble native human tissues, making it suitable for the replacement of damaged or injured tissues. In this review, we will discuss the structure and mechanical properties of the BC and summarize the techniques used to characterize these properties. We will also discuss the functionalization of BC to yield nanocomposites and the surface modification of BC by plasma and irradiation-based methods to fabricate materials with improved functionalities such as bactericidal capabilities.

Effects of pretreatment, NaOH concentration, and extraction temperature on the cellulose from Lophatherum gracile Brongn

Lophatherum gracile Brongn. (LGB), a homology material of medicine and food, has plentiful cellulose. Aiming to investigate the physiochemical characteristic differences of LGB cellulose extracted by various pretreatment methods and extraction conditions, the effect of dry crushing and wet beating, and the alkaline solution concentration and temperature were compared. Results showed that the extracted cellulose after dry crushing pretreatment had higher purity and lower non-cellulosic components such as hemicellulose, lignin and ash than those obtained by wet beating pretreatment. Furthermore, the impurities were more thoroughly removed by the alkaline solution at high concentration and temperature. Structural characterization revealed that the cellulose obtained by wet beating pretreatment had more fibrillation and smaller particle size, while destroyed crystallinity resulting in bad thermal stability. The alkaline solution temperature had no effect on the morphology and particle size, but high alkaline solution temperature (90 °C) improved crystallinity and thermal stability. Furtherly, the cellulose II produced by at high alkaline solution concentration (18 wt%) exhibited denser surface, smaller particle size and higher thermal stability than the cellulose I extracted at low alkaline solution concentration (4 wt%). Especially, the crystallinity of cellulose II was higher than that of cellulose I with dry crushing pretreatment, while the cellulose obtained by wet beating displayed an opposite trend. Hydration properties indicated that the water holding capacity, oil binding capacity and swelling capacity of the cellulose pretreated by dry crushing were higher than those of the cellulose pretreated by wet beating, and the cellulose I exhibited higher hydration properties compared to the cellulose II, which may depend on its loose network structure. This study suggested that dry crushing pretreatment and high alkaline solution temperature could effectively improve functional properties of LGB cellulose I and II, which promoted its use in food applications.

Production of bacterial cellulose tubes for biomedical applications: Analysis of the effect of fermentation time on selected properties

Biosynthesis of bacterial cellulose (BC) in cylindrical oxygen permeable molds allows the production of hollow tubular structures of increasing interest for biomedical applications (artificial blood vessels, ureters, urethra, trachea, esophagus, etc.). In the current contribution a simple set-up is used to obtain BC tubes of predefined dimensions; and the effects of fermentation time on the water holding capacity, nanofibrils network architecture, specific surface area, chemical purity, thermal stability, mechanical properties, and cell adhesion, proliferation and migration of BC tubes are systematically analysed for the first time. The results reported highlight the role of culture time on key properties of the BC tubes produced, with significant differences arising from the denser and more compact fibril arrangements generated at longer fermentation intervals.

Valorization of Byproducts of Hemp Multipurpose Crop: Short Non-Aligned Bast Fibers as a Source of Nanocellulose

Nanocellulose was extracted from short bast fibers, from hemp (Cannabis sativa L.) plants harvested at seed maturity, non-retted, and mechanically decorticated in a defibering apparatus, giving non-aligned fibers. A chemical pretreatment with NaOH and HCl allowed the removal of most of the non-cellulosic components of the fibers. No bleaching was performed. The chemically pretreated fibers were then refined in a beater and treated with a cellulase enzyme, followed by mechanical defibrillation in an ultrafine friction grinder. The fibers were characterized by microscopy, infrared spectroscopy, thermogravimetric analysis and X-ray diffraction after each step of the process to understand the evolution of their morphology and composition. The obtained nanocellulose suspension was composed of short nanofibrils with widths of 5-12 nm, stacks of nanofibrils with widths of 20-200 nm, and some larger fibers. The crystallinity index was found to increase from 74% for the raw fibers to 80% for the nanocellulose. The nanocellulose retained a yellowish color, indicating the presence of some residual lignin. The properties of the nanopaper prepared with the hemp nanocellulose were similar to those of nanopapers prepared with wood pulp-derived rod-like nanofibrils.

Fabrication of Paper Sheets Coatings Based on Chitosan/Bacterial Nanocellulose/ZnO with Enhanced Antibacterial and Mechanical Properties

Here, we designed paper sheets coated with chitosan, bacterial cellulose (nanofibers), and ZnO with boosted antibacterial and mechanical activity. We investigated the compositions, with ZnO exhibiting two different sizes/shapes: (1) rods and (2) irregular sphere-like particles. The proposed processing of bacterial cellulose resulted in the formation of nanofibers. Antimicrobial behavior was tested using E. coli ATCC® 25922™ following the ASTM E2149-13a standard. The mechanical properties of the paper sheets were measured by comparing tearing resistance, tensile strength, and bursting strength according to the ISO 5270 standard. The results showed an increased antibacterial response (assigned to the combination of chitosan and ZnO, independent of its shape and size) and boosted mechanical properties. Therefore, the proposed composition is an interesting multifunctional mixture for coatings in food packaging applications.

Cytocompatible cellulose nanofibers from invasive plant species Agave americana L. and Ricinus communis L.: a renewable green source of highly crystalline nanocellulose

In this study, the fibers of invasive species Agave americana L. and Ricinus communis L. were successfully used for the first time as new sources to produce cytocompatible and highly crystalline cellulose nanofibers. Cellulose nanofibers were obtained by two methods, based on either alkaline or acid hydrolysis. The morphology, chemical composition, and crystallinity of the obtained materials were characterized by scanning electron microscopy (SEM) together with energy-dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. The crystallinity indexes (CIs) of the cellulose nanofibers extracted from A. americana and R. communis were very high (94.1% and 92.7%, respectively). Biological studies evaluating the cytotoxic effects of the prepared cellulose nanofibers on human embryonic kidney 293T (HEK293T) cells were also performed. The nanofibers obtained using the two different extraction methods were all shown to be cytocompatible in the concentration range assayed (i.e., 0‍‒‍500 µg/mL). Our results showed that the nanocellulose extracted from A. americana and R. communis fibers has high potential as a new renewable green source of highly crystalline cellulose-based cytocompatible nanomaterials for biomedical applications.

Preparation of cellulose nanospheres via combining ZnCl2·3H2O pretreatment and p-toluenesulfonic hydrolysis as a two-step method

Spherical nanocelluloses, also known as cellulose nanospheres (CNS), have controllable morphology and have shown advantages as green template material, emulsion stabilizer. Herein, CNS were prepared via a new two-step method, first pretreatment of microcrystalline cellulose (MCC) using ZnCl₂·3H₂O and then acid hydrolysis of regenerated cellulose (RC) via p-toluenesulfonic acid (p-TsOH). The shape, size, crystallinity of MCC were changed, and nubbly RC with smallest size (942 nm) was obtained after 2 h pretreatment by ZnCl₂·3H₂O. CNS with high 61.3% yield were produced after acid hydrolysis (67 wt% p-TsOH) of RC at 80 °C, 6 h. The analysis of Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM) showed that CNS had an average diameter of 347 nm. CNS were present in precipitate after high-speed centrifugation, due to the high Zeta potential of -12 mV and large size. The structure of CNS was tested by Fourier Transfer Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Nuclear Magnetic Resonance (NMR), CNS had high crystallinity (cellulose II) of 61%. Thermal Gravimetric Analysis (TGA) indicated that CNS had high thermal stability (T_onset 303.3 °C, T_max 332 °C). CNS showed poor re-dispersibility in water/ethanol/THF, 1 wt% CNS could be dissolved in ZnCl₂·3H₂O. 7.37% rod-like CNC were obtained after 6 h hydrolysis. FTIR proved that p-TsOH was recovered by re-crystallization. This study provided a novel, sustainable two-step method for the preparation of spherical CNS.

Nanocellulose as template to prepare rough-hydroxy rich hollow silicon mesoporous nanospheres (R-nCHMSNs) for drug delivery

Drug-delivery technology is an effective way to promote drug absorption and efficacy. Mesoporous hollow silica material and small-molecule drug ibuprofen were used as a carrier model and as model drug, respectively. By quantum chemical calculation (density functional theory and frontier orbital theory), it was found that the content of geminal silanols on the material surface played a decisive role in the release of the different drugs. The rough hollow materials are easily adsorbed and have a large loading capacity, and so we fabricated a mesoporous hollow silica material (R-nCHMSNs) with a rough surface and rich geminal silanols by using hydroxyl-rich nanocellulose as a template. The content and types of hydroxyl groups on the material surface were studied by ²⁹Si NMR. The loading and delivery of ibuprofen and lysozyme were studied in detail. Materials with rich geminal silanols exhibited excellent delivery properties for different drugs, which shows great potential and research value for drug delivery.

Morphology and transport properties of membranes obtained by coagulation of cellulose solutions in isobutanol

The evolution of structural-morphological transformations of cellulose membranes obtained from solutions in N-methylmorpholine-N-oxide through various temperature isobutanol coagulation baths and subsequent treatment with water and their transport properties were studied. Using SEM, it was found that during coagulation in water and drying of the membranes, a uniform monolithic microheterogeneous texture was formed. The replacement of an aqueous precipitation bath with an isobutanol one leads to the formation of a porous structure with wide pore size and shape distributions. With an increase in precipitant temperature in the as-formed membrane, transverse tunnel cavities are formed with respect to the membrane-forming axis, which collapses when the membrane is washed with water, forming a dense texture with a non-uniform membrane volume. The mechanical properties of the obtained membranes were determined and a mechanism is proposed that allows their values to be correlated with structural-morphological and transport properties.

Direct determination of the degree of fibrillation of wood pulps by distribution analysis of pixel-resolved optical retardation

We propose a new methodology for direct evaluation of the degree of fibrillation of fibrillating pulp suspensions through the pixel-resolved retardation distribution. Through simple normalization by just injecting a pulp suspension with a certain concentration into a quartz flow channel with a constant cross-sectional shape, the degree of fibrillation (i.e., the degree of bundling of cellulose molecular chains) can be directly mapped by the retardation gradation, reflecting locally high retardation (pulp fibers), smaller retardation (balloons on fibrillating pulps), and much smaller retardation close to water (dispersed nanofibers). Both the average retardation and standard deviation are found to be the direct indicators of the degree of fibrillation. We envision that the proposed methodology will become the future standard for determining the degree of fibrillation by the retardation distribution, and it will pave the way for more precise control of pulp fibrillation and more sophisticated applications of cellulose nanofiber suspensions.

One-step electrochemically induced counterion exchange to construct free-standing carboxylated cellulose nanofiber/metal composite hydrogels

The fabrication of polymeric composite hydrogel with hierarchical structure in a simple, controllable, and straightforward process poses great importance for manufacturing nanomaterials and subsequent applications. Herein, we report a one-step and template-free counterion exchange method to construct free-standing carboxylated cellulose nanofiber composite hydrogels. Metal ions were electrochemically and locally released from the electrode and chelated with carboxylated cellulose nanofibers, leading to the in-situ formation of composite hydrogels. The properties of composite hydrogels can be easily programmed by the type of electrode, current density, and electrodeposited suspension. Significantly, the composited hydrogels exhibited interconnected nanoporous structure, enhanced thermal degradation, improved mechanical strength and antibacterial activity. The results suggest great potential of anodic electrodeposition to fabricate nanofiber/metal composite hydrogels.

Nanostructured Cellulose-Gellan-Xyloglucan-Lysozyme Dressing Seeded with Mesenchymal Stem Cells for Deep Second-Degree Burn Treatment

PURPOSE

In deep burns, wound contraction and hypertrophic scar formation can generate functional derangement and debilitation of the affected part. In order to improve the quality of healing in deep second-degree burns, we developed a new treatment in a preclinical model using nanostructured membranes seeded with mesenchymal stem cells (MSCs).

METHODS

Membranes were obtained by reconstitution of bacterial cellulose (reconstituted membrane [RM]) and produced by a dry-cast process, then RM was incorporated with 10% tamarind xyloglucan plus gellan gum 1:1 and 10% lysozyme (RMGT-LZ) and with 10% gellan gum and 10% lysozyme (RMG-LZ). Membrane hydrophobic/hydrophilic characteristics were investigated by static/dynamic contact-angle measurements. They were cultivated with MSCs, and cell adhesion, proliferation, and migration capacity was analyzed with MTT assays. Morphological and topographic characteristics were analyzed by scanning electron microscopy. MSC patterns in flow cytometry and differentiation into adipocytes and osteocytes were checked. In vivo assays used RMG-LZ and RMGT-LZ (with and without MSCs) in Rattus norvegicus rats submitted to burn protocol, and histological sections and collagen deposits were analyzed and immunocytochemistry assay performed.

RESULTS

In vitro results demonstrated carboxyl and amine groups made the membranes moderately hydrophobic and xyloglucan inclusion decreased wettability, favoring MSC adhesion, proliferation, and differentiation. In vivo, we obtained 40% and 60% reduction in acute/chronic inflammatory infiltrates, 96% decrease in injury area, increased vascular proliferation and collagen deposition, and complete epithelialization after 30 days. MSCs were detected in burned tissue, confirming they had homed and proliferated in vivo.

CONCLUSION

Nanostructured cellulose-gellan-xyloglucan-lysozyme dressings, especially when seeded with MSCs, improved deep second-degree burn regeneration.

Pure cellulose lithium-ion battery separator with tunable pore size and improved working stability by cellulose nanofibrils

Separator is a vital component of lithium-ion batteries (LIBs) due to its important roles in the safety and electrochemical performance of the batteries. Herein, we reported a cellulose nanofibrils (CNFs) reinforced pure cellulose paper (CCP) as a LIBs separator fabricated by a facile filtration process. The nanosized CNFs played crucial roles as a tuner to optimize the pore size of the as-prepared CCP, and also as a reinforcer to improve the mechanical strength of the resultant CCP. Results showed that the tensile strength of the CCP with 20 wt.% CNFs was 227 % higher compared to the commercial cellulose separator. In addition, the lithium cobalt oxide/lithium metal battery assembled with CCP separator displayed better cycle performance and working stability (capacity retention ratio of 91 % after 100 cycles) compared to the batteries with cellulose separator (52 %) and polypropylene separator (84 %) owing to the multiple synergies between CCP separator and electrolytes.

Antibacterial Activity of Bacterial Cellulose Loaded with Bacitracin and Amoxicillin: In Vitro Studies

The use of bacterial cellulose (BC) in skin wound treatment is very attractive due to its unique characteristics. These dressings’ wet environment is an important feature that ensures efficient healing. In order to enhance the antimicrobial performances, bacterial-cellulose dressings were loaded with amoxicillin and bacitracin as antibacterial agents. Infrared characterization and thermal analysis confirmed bacterial-cellulose binding to the drug. Hydration capacity showed good hydrophilicity, an efficient dressing’s property. The results confirmed the drugs’ presence in the bacterial-cellulose dressing’s structure as well as the antimicrobial efficiency against Staphylococcus aureus and Escherichia coli. The antimicrobial assessments were evaluated by contacting these dressings with the above-mentioned bacterial strains and evaluating the growth inhibition of these microorganisms.

Nanocellulose Hybrids with Metal Oxides Nanoparticles for Biomedical Applications

Cellulose is one of the most affordable, sustainable and renewable resources, and has attracted much attention especially in the form of nanocellulose. Bacterial cellulose, cellulose nanocrystals or nanofibers may serve as a polymer support to enhance the effectiveness of metal nanoparticles. The resultant hybrids are valuable materials for biomedical applications due to the novel optical, electronic, magnetic and antibacterial properties. In the present review, the preparation methods, properties and application of nanocellulose hybrids with different metal oxides nanoparticles such as zinc oxide, titanium dioxide, copper oxide, magnesium oxide or magnetite are thoroughly discussed. Nanocellulose-metal oxides antibacterial formulations are preferred to antibiotics due to the lack of microbial resistance, which is the main cause for the antibiotics failure to cure infections. Metal oxide nanoparticles may be separately synthesized and added to nanocellulose (ex situ processes) or they can be synthesized using nanocellulose as a template (in situ processes). In the latter case, the precursor is trapped inside the nanocellulose network and then reduced to the metal oxide. The influence of the synthesis methods and conditions on the thermal and mechanical properties, along with the bactericidal and cytotoxicity responses of nanocellulose-metal oxides hybrids were mainly analyzed in this review. The current status of research in the field and future perspectives were also signaled.

Novel research on nanocellulose production by a marine Bacillus velezensis strain SMR: a comparative study

Bacterial nanocellulose (BNC) is a nanofibrillar polymer that possesses unique characteristics such as high chemical purity, mechanical strength, flexibility, and absorbency. In addition, different bacterial strains can form nanocellulose (NC) in multiple shapes and sizes. This study describes the first report of a marine Bacillus strain that is able to synthesize NC. The strain identified as B. velezensis SMR based on 16S rDNA sequencing, produced highly structured NC, as confirmed by X-ray diffraction (XRD) and Scanning Electron Microscopic Analysis (SEM). In Hestrin-Schramm (HS) medium, B. velezensis SMR produced twice the quantity of BNC in comparison to the reference strain, G. xylinus ATCC 10245. The ability of B. velezensis SMR to produce NC using different industrial waste materials as growth media was tested. Growth in Ulva seaweed extract supported a 2.5-fold increase of NC production by B. velezensis SMR and a threefold increase in NC production by G. xylinus ATCC 10245. As proof of principle for the usability of NC from B. velezensis SMR, we successfully fabricated a BNC-based polyvinyl alcohol hydrogel (BNC-PVA) system, a promising material used in different fields of application such as medicine, food, and agriculture.

In vitro hemo- and cytocompatibility of bacterial nanocelluose small diameter vascular grafts: Impact of fabrication and surface characteristics

Objective

There is an increasing need for small diameter vascular grafts with superior host hemo- and cytocompatibilities, such as low activation of platelets and leukocytes. Therefore, we aimed to investigate whether the preparation of bacterial nanocellulose grafts with different inner surfaces has an impact on in vitro host cytocompatibility.

Methods

We have synthesized five different grafts in a bioreactor, namely open interface surface (OIS), inverted (INV), partially air dried (PAD), surface formed in air contact (SAC) and standard (STD) that were characterized by a different surface roughness. The grafts (length 55 mm, inner diameter 5 mm) were attached to heparinized polyvinyl chloride tubes, loaded with human blood and rotated at 37°C for 4 hours. Then, blood was analyzed for frequencies of cellular fractions, oxidative products, soluble complement and thrombin factors. The results were compared to clinically approved grafts made of polyethylene terephthalate and expanded polytetrafluoroethylene. Additionally, blood platelets were labelled with ¹¹¹Indium-oxine to visualize the distribution of adherent platelets in the loop by scintigraphy.

Results

SAC nanocellulose grafts with the lowest surface roughness exhibited superior performance with <10% leukocyte and <50% thrombocyte loss in contrast to other grafts that exhibited >65% leukocyte and >90% thrombocyte loss. Of note, SAC nanocellulose grafts showed lowest radioactivity with scintigraphy analyses, indicating reduced platelet adhesion. Although the levels of reactive oxygen species and cell free DNA did not differ significantly, the levels of thrombin-antithrombin complexes were lowest in SAC grafts. However, all nanocellulose grafts exhibited enhanced complement activation.

Conclusion

The systematic variation of the inner surfaces of BNC vascular grafts significantly improves biocompatibility. Especially, SAC grafts exhibited the lowest loss of platelets as well as leukocytes and additionally significantly diminished activation of the coagulation system. Further animal studies are needed to study in vivo biocompatibilities.

Artificially lignified cell wall catalyzed by peroxidase selectively localized on a network of microfibrils from cultured cells

An artificial lignified cell wall was synthesized in three steps: (1) isolation of microfibrillar network; (2) localization of peroxidase through immunoreaction; and (3) polymerization of DHP to lignify the cell wall. Artificial woody cell wall synthesis was performed following the three steps along with the actual formation in nature using cellulose microfibrils extracted from callus derived from Cryptomeria japonica. First, we constructed a polysaccharide network on a transmission electron microscopy (TEM) grid. The preparation method was optimized by chemical treatment, followed by mechanical fibrillation to create a microfibrillated network. Morphology was examined by TEM, and chemical characterization was by Fourier transform infrared (FTIR) spectroscopy. Second, we optimized the process to place peroxidase on the microfibrils via an immunoreaction technique. Using a xyloglucan antibody, we could ensure that gold particles attached to the secondary antibodies were widely and uniformly localized along with the microfibril network. Third, we applied the peroxidase attached to secondary antibodies and started to polymerize the lignin on the grid by simultaneously adding coniferyl alcohol and hydrogen peroxide. After 30 min of artificial lignification, TEM observation showed that lignin-like substances were deposited on the polysaccharide network. In addition, FTIR spectra revealed that the bands specific for lignin had increased, demonstrating the successful artificial formation of woody cell walls. This approach may be useful for studying woody cell wall formation and for producing made-to-order biomaterials.

A mutation in the catalytic domain of cellulose synthase 6 halts its transport to the Golgi apparatus

Cellulose microfibrils, which form the mechanical framework of the plant cell wall, are synthesized by the cellulose synthase complex in the plasma membrane. Here, we introduced point mutations into the catalytic domain of cellulose synthase 6 (CESA6) in Arabidopsis to produce enhanced yellow fluorescent protein (EYFP)-tagged CESA6D395N, CESA6Q823E, and CESA6D395N+Q823E, which were exogenously produced in a cesa6 null mutant, prc1-1. Comparison of these mutants in terms of plant phenotype, cellulose content, cellulose synthase complex dynamics, and organization of cellulose microfibrils showed that prc1-1 expressing EYFP:CESA6D395N or CESA6D395N+Q823E was nearly the same as prc1-1, whereas prc1-1 expressing EYFP:CESA6Q823E was almost identical to wild type and prc1-1 expressing EYFP:WT CESA6, indicating that CESA6D395N and CESA6D395N+Q823E do not function in cellulose synthesis, while CESA6Q823E is still functionally active. Total internal reflection fluorescence microscopy and confocal microscopy were used to monitor the subcellular localization of these proteins. We found that EYFP:CESA6D395N and EYFP:CESA6D395N+Q823E were absent from subcellular regions containing the Golgi and the plasma membrane, and they appeared to be retained in the endoplasmic reticulum. By contrast, EYFP:CESA6Q823E had a normal localization pattern, like that of wild-type EYFP:CESA6. Our results demonstrate that the D395N mutation in CESA6 interrupts its normal transport to the Golgi and its eventual participation in cellulose synthase complex assembly.

Cellulose-based biomaterials integrated with copper-cystine hybrid structures as catalysts for nitric oxide generation

Bionanocomposite materials were developed from the assembly of polymer-coated copper-cystine high-aspect ratio structures (CuHARS) and cellulose fibers. The coating of the metal-organic materials with polyallylamine hydrochloride (PAH) allows their covalent linkage to TEMPO-oxidized cellulose by means of EDC/NHS. The resulting materials can be processed as films or macroporous foams by solvent casting and lyophilization, respectively. The films show good mechanical behavior with Young's moduli around 1.5 GPa as well as resistance in water, while the obtained foams show an open network of interconnected macropores with average diameters around 130 μm, depending on the concentration of the initial suspension, and compression modulus values around 450 kPa, similar to other reported freeze-dried nanocellulose-based aerogels. Based on these characteristics, the cellulose/PAH-CuHARS composites are promising for potential biomedical applications as implants or wound dressing materials. They have proved to be effective in the decomposition of low molecular weight S-nitrosothiols (RSNOs), similar to those existing in blood, releasing nitric oxide (NO). This effect is attributed to the presence of copper in the crystalline structure of the CuHARS building unit, which can be gradually released in the presence of redox species like ascorbic acid, typically found in blood. The resulting biomaterials can offer the interesting properties associated with NO, like antimicrobial activity as preliminary tests showed here with Escherichia coli and Staphylococcus epidermidis. In the presence of physiological concentration of RSNOs the amount of generated NO (around 360 nM) is not enough to show bactericidal effect on the studied bacteria, but it could provide other properties inherent to NO even at low concentration in the nM range like anti-inflammatory and anti-thrombotic effects. The cytotoxic effect recorded of the films on rat brain endothelial cells (BMVECs) is least significant and proves them to be friendly enough for further biological studies.

Flexible Anti-Biofouling MXene/Cellulose Fibrous Membrane for Sustainable Solar-Driven Water Purification

Solar-driven interfacial water evaporation is regarded as an effective, renewable, and environment-friendly technology for clean water production. However, biofouling caused by the nonspecific interaction between the steam generator and biofoulants generally hinders the efficient application of wastewater treatment. Herein, this work reports a facile strategy to fabricate flexible anti-biofouling fibrous photothermal membrane consisting of a MXene-coated cellulose membrane for highly efficient solar-driven water steam evaporation toward water purification applications. The as-prepared MXene/cellulose photothermal membrane exhibits light absorption efficiency as high as ∼94% in a wide solar spectrum range and a water evaporation rate up to 1.44 kg m^-2 h^-1 under one solar illumination. Also, the MXene/cellulose membrane shows very high antibacterial efficiency (above 99.9%) owing to the MXene coating as a highly effective bacteriostatic agent. Such a flexible, anti-biofouling, and high-efficiency photothermal membrane sheds light on practical applications in long-term wastewater treatments.

The Crystallinity and Aspect Ratio of Cellulose Nanomaterials Determine Their Pro-Inflammatory and Immune Adjuvant Effects In Vitro and In Vivo

Nanocellulose is increasingly considered for applications; however, the fibrillar nature, crystalline phase, and surface reactivity of these high aspect ratio nanomaterials need to be considered for safe biomedical use. Here a comprehensive analysis of the impact of cellulose nanofibrils (CNF) and nanocrystals (CNC) is performed using materials provided by the Nanomaterial Health Implications Research Consortium of the National Institute of Environmental Health Sciences. An intermediary length of nanocrystals is also derived by acid hydrolysis. While all CNFs and CNCs are devoid of cytotoxicity, 210 and 280 nm fluorescein isothiocyanate (FITC)-labeled CNCs show higher cellular uptake than longer and shorter CNCs or CNFs. Moreover, CNCs in the 200-300 nm length scale are more likely to induce lysosomal damage, NLRP3 inflammasome activation, and IL-1β production than CNFs. The pro-inflammatory effects of CNCs are correlated with higher crystallinity index, surface hydroxyl density, and reactive oxygen species generation. In addition, CNFs and CNCs can induce maturation of bone marrow-derived dendritic cells and CNCs (and to a lesser extent CNFs) are found to exert adjuvant effects in ovalbumin (OVA)-injected mice, particularly for 210 and 280 nm CNCs. All considered, the data demonstrate the importance of length scale, crystallinity, and surface reactivity in shaping the innate immune response to nanocellulose.

Nanocellulose-Reinforced Polyurethane for Waterborne Wood Coating

With the enhancement of people’s environmental awareness, waterborne polyurethane (PU) paint—with its advantages of low release of volatile organic compounds (VOCs), low temperature flexibility, acid and alkali resistance, excellent solvent resistance and superior weather resistance—has made its application for wood furniture favored by the industry. However, due to its lower solid content and weak intermolecular force, the mechanical properties of waterborne PU paint are normally less than those of the traditional solvent-based polyurethane paint, which has become the key bottleneck restricting its wide applications. To this end, this study explores nanocellulose derived from biomass resources by the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation method to reinforce and thus improve the mechanical properties of waterborne PU paint. Two methods of adding nanocellulose to waterborne PU—chemical addition and physical blending—are explored. Results show that, compared to the physical blending method, the chemical grafting method at 0.1 wt% nanocellulose addition results in the maximum improvement of the comprehensive properties of the PU coating. With this method, the tensile strength, elongation at break, hardness and abrasion resistance of the waterborne PU paint increase by up to 58.7%, ~55%, 6.9% and 3.45%, respectively, compared to the control PU; while the glossiness and surface drying time were hardly affected. Such exploration provides an effective way for wide applications of water PU in the wood industry and nanocellulose in waterborne wood coating.

Influence of calcium chloride impregnation on the thermal and high-temperature carbonization properties of bamboo fiber

In this study, bamboo fiber was pretreated with calcium chloride (CaCl₂) solution by using an ultrasonic method, and then heat-treated at 250°C and carbonized at 1000°C. The effect of impregnation with CaCl₂ on the thermal and chemical properties and morphology of bamboo fiber was determined using thermogravimetric and differential thermogravimetric analyses, in situ Fourier transform infrared spectroscopy, and scanning electron microscopy. The pore structure of the carbonized bamboo fiber was investigated. The results revealed that bamboo fiber pretreated with 5% CaCl₂ (BFCa₅) showed a downward shift in the temperature of the maximum rate of weight loss253°C and increase in char residue to 31.89%. BFCa₅ was expected to undergo dehydration under the combined effect of oxygen-rich atmosphere and CaCl₂ catalysis from 210°C, and cellulose decomposition would be remarkable at 250°C. Pretreatment with 5% CaCl₂ promoted the formation of porous structure of the carbonized fiber, which exhibited a typical Type-IV isotherm, with the Brunauer–Emmett–Teller specific surface area of 331.32 m²/g and Barrett–Joyner–Halenda adsorption average pore diameter of 13.6440 nm. Thus, CaCl₂ was found to be an effective catalyst for the pyrolysis of bamboo fiber, facilitating the formation of porous carbonized fiber.

Evaluation of Mechanical and Interfacial Properties of Bio-Composites Based on Poly(Lactic Acid) with Natural Cellulose Fibers

The circular economy policy and the interest for sustainable material are inducing a constant expansion of the bio-composites market. The opportunity of using natural fibers in bio-based and biodegradable polymeric matrices, derived from industrial and/or agricultural waste, represents a stimulating challenge in the replacement of traditional composites based on fossil sources. The coupling of bioplastics with natural fibers in order to lower costs and promote degradability is one of the primary objectives of research, above all in the packaging and agricultural sectors where large amounts of non-recyclable plastics are generated, inducing a serious problem for plastic disposal and potential accumulation in the environment. Among biopolymers, poly(lactic acid) (PLA) is one of the most used compostable, bio-based polymeric matrices, since it exhibits process ability and mechanical properties compatible with a wide range of applications. In this study, two types of cellulosic fibers were processed with PLA in order to obtain bio-composites with different percentages of microfibers (5%, 10%, 20%). The mechanical properties were evaluated (tensile and impact test), and analytical models were applied in order to estimate the adhesion between matrix and fibers and to predict the material's stiffness. Understanding these properties is of particular importance in order to be able to tune and project the final characteristics of bio-composites.

Surface engineering of spongy bacterial cellulose via constructing crossed groove/column micropattern by low-energy CO2 laser photolithography toward scar-free wound healing

Bacterial cellulose (BC) is a bio-derived polymer, and it has been considered as an excellent candidate material for tissue engineering. In this study, a crossed groove/column micropattern was constructed on spongy, porous BC using low-energy CO₂ laser photolithography. Applying the targeted immobilization of a tetrapeptide consisting of Arginine-Glycine-Aspartic acid-Serine (H-Arg-Gly-Asp-Ser-OH, RGDS) as a fibronectin onto the column platform surface, the resulting micropatterned BC (RGDS-MPBC) exhibited dual affinities to fibroblasts and collagen. Material characterization of RGDS-MPBC revealed that the micropattern was built by the column part with size of ~100 × 100 μm wide and ~100 μm deep, and the groove part with size of ~150 μm wide. Hydrating the MPBC did not result in the collapse of the integrity of the micropattern, suggesting its potential application in a highly hydrated wound environment. Cell culture assays revealed that the RGDS-MPBC exhibited an improved cytotoxicity to mouse fibroblasts L929, as compared to the pristine BC. Meanwhile, it was observed that the RGDS-MPBC was able to guide the ordered aggregation of human skin fibroblast (HSF) cells on the column platform surface, and no HSF cells were found in the groove channels. Over time, it was found that a dense network of collagen was gradually established across the groove channels. Furthermore, the in-vivo animal study preliminarily demonstrated the scar-free healing potential of the micropatterned BC materials. Therefore, this RGDS-MPBC material exhibited its advantages in guiding cell migration and collagen distribution, which could present a prospect in the establishment of "basket-woven" organization of collagen in normal skin tissue against the formation of dense, parallel aggregation of collagen fibers in scar tissue toward scar-free wound healing outcome.

Distribution and dispersal of metals in contaminated fibrous sediments of industrial origin

Industrial emissions can impact aquatic environments and unregulated discharges from pulp and paper factories have resulted in deposits of cellulose fiber along the Swedish coast. These deposits are contaminated by metals, but due to their unique fibrous character the extent of sorption and dispersal of the metals is unclear. Fibrous sediments were sampled at two sites in the Ångermanälven river estuary, Sweden. The partitioning of metals between the sediment, pore water and bottom water was investigated and the degree of bioavailability was evaluated. The levels of metals in the sediment were high in fibrous or offshore samples, depending on the metal, whereas the levels of dissolved metals in pore water were low or below the limit of quantification. Partition coefficients (K_D) showed that sorption to the sediment was stronger at one of the fibrous sites, possibly related to the type and size of organic matter. Undisturbed bottom water samples contained low levels of both dissolved and particle bound metals, but when comparing measured metal concentrations to threshold values of ecological status and ecotoxicological assessment criteria, both sediments and bottom water may be detrimental to living organisms. In-situ re-suspension experiments showed that the concentrations of particle bound metals increased whereas the dissolved concentrations decreased. The analyzed metals are probably retained by the solid phases of the fibrous sediment or adsorbed to particles in the water, reducing their bioavailability.

Cellulose defibrillation and functionalization by plasma in liquid treatment

Submerged liquid plasma (SLP) is a new and promising method to modify powder materials. Up to now, this technique has been mostly applied to carbonaceous materials, however, SLP shows great potential as a low-cost and environmental-friendly method to modify cellulose. In this work we demonstrate the modification of microcrystalline cellulose (MCC) by applying the SLP combined with ultrasonication treatments. The plasma generated either in an inert (argon) or reactive (argon: oxygen or argon:nitrogen) gas was used in MCC dispersions in water or acetonitrile:water mixtures. An enhanced defibrillation of MCC has been observed following the application of SLP. Furthermore, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy have been applied to investigate the surface functionalization of MCC with oxygen or nitrogen moieties. Depending on the plasma treatment applied, poly (3-hydroxybutyrate) composites fabricated with the plasma modified cellulose fibers showed better thermal stability and mechanical properties than pristine PHB. This submerged liquid plasma processing method offers a unique approach for the activation of cellulose for defibrillation and functionalization, aiming towards an improved reinforcing ability of biopolymers.

Resonant soft X-ray scattering reveals cellulose microfibril spacing in plant primary cell walls

Cellulose microfibrils are crucial for many of the remarkable mechanical properties of primary cell walls. Nevertheless, many structural features of cellulose microfibril organization in cell walls are not yet fully described. Microscopy techniques provide direct visualization of cell wall organization, and quantification of some aspects of wall microstructure is possible through image processing. Complementary to microscopy techniques, scattering yields structural information in reciprocal space over large sample areas. Using the onion epidermal wall as a model system, we introduce resonant soft X-ray scattering (RSoXS) to directly quantify the average interfibril spacing. Tuning the X-ray energy to the calcium L-edge enhances the contrast between cellulose and pectin due to the localization of calcium ions to homogalacturonan in the pectin matrix. As a consequence, RSoXS profiles reveal an average center-to-center distance between cellulose microfibrils or microfibril bundles of about 20 nm.

Multiscale Control of Nanocellulose Assembly: Transferring Remarkable Nanoscale Fibril Mechanics to Macroscale Fibers

Nanoscale building blocks of many materials exhibit extraordinary mechanical properties due to their defect-free molecular structure. Translation of these high mechanical properties to macroscopic materials represents a difficult materials engineering challenge due to the necessity to organize these building blocks into multiscale patterns and mitigate defects emerging at larger scales. Cellulose nanofibrils (CNFs), the most abundant structural element in living systems, has impressively high strength and stiffness, but natural or artificial cellulose composites are 3-15 times weaker than the CNFs. Here, we report the flow-assisted organization of CNFs into macroscale fibers with nearly perfect unidirectional alignment. Efficient stress transfer from macroscale to individual CNF due to cross-linking and high degree of order enables their Young's modulus to reach up to 86 GPa and a tensile strength of 1.57 GPa, exceeding the mechanical properties of known natural or synthetic biopolymeric materials. The specific strength of our CNF fibers engineered at multiscale also exceeds that of metals, alloys, and glass fibers, enhancing the potential of sustainable lightweight high-performance materials with multiscale self-organization.

Exploiting CELLULOSE SYNTHASE (CESA) Class Specificity to Probe Cellulose Microfibril Biosynthesis

Cellulose microfibrils are the basic units of cellulose in plants. The structure of these microfibrils is at least partly determined by the structure of the cellulose synthase complex. In higher plants, this complex is composed of 18 to 24 catalytic subunits known as CELLULOSE SYNTHASE A (CESA) proteins. Three different classes of CESA proteins are required for cellulose synthesis and for secondary cell wall cellulose biosynthesis these classes are represented by CESA4, CESA7, and CESA8. To probe the relationship between CESA proteins and microfibril structure, we created mutant cesa proteins that lack catalytic activity but retain sufficient structural integrity to allow assembly of the cellulose synthase complex. Using a series of Arabidopsis (Arabidopsis thaliana) mutants and genetic backgrounds, we found consistent differences in the ability of these mutant cesa proteins to complement the cellulose-deficient phenotype of the cesa null mutants. The best complementation was observed with catalytically inactive cesa4, while the equivalent mutation in cesa8 exhibited significantly lower levels of complementation. Using a variety of biophysical techniques, including solid-state nuclear magnetic resonance and Fourier transform infrared microscopy, to study these mutant plants, we found evidence for changes in cellulose microfibril structure, but these changes largely correlated with cellulose content and reflected differences in the relative proportions of primary and secondary cell walls. Our results suggest that individual CESA classes have similar roles in determining cellulose microfibril structure, and it is likely that the different effects of mutating members of different CESA classes are the consequence of their different catalytic activity and their influence on the overall rate of cellulose synthesis.

Xyloglucan in the primary cell wall: assessment by FESEM, selective enzyme digestions and nanogold affinity tags

Xyloglucan has been hypothesized to bind extensively to cellulose microfibril surfaces and to tether microfibrils into a load-bearing network, thereby playing a central role in wall mechanics and growth, but this view is challenged by newer results. Here we combined high-resolution imaging by field emission scanning electron microscopy (FESEM) with nanogold affinity tags and selective endoglucanase treatments to assess the spatial location and conformation of xyloglucan in onion cell walls. FESEM imaging of xyloglucanase-digested cell walls revealed an altered microfibril organization but did not yield clear evidence of xyloglucan conformations. Backscattered electron detection provided excellent detection of nanogold affinity tags in the context of wall fibrillar organization. Labelling with xyloglucan-specific CBM76 conjugated with nanogold showed that xyloglucans were associated with fibril surfaces in both extended and coiled conformations, but tethered configurations were not observed. Labelling with nanogold-conjugated CBM3, which binds the hydrophobic surface of crystalline cellulose, was infrequent until the wall was predigested with xyloglucanase, whereupon microfibril labelling was extensive. When tamarind xyloglucan was allowed to bind to xyloglucan-depleted onion walls, CBM76 labelling gave positive evidence for xyloglucans in both extended and coiled conformations, yet xyloglucan chains were not directly visible by FESEM. These results indicate that an appreciable, but still small, surface of cellulose microfibrils in the onion wall is tightly bound with extended xyloglucan chains and that some of the xyloglucan has a coiled conformation.

Synthesis and Self-Assembly of Cellulose Microfibrils from Reconstituted Cellulose Synthase

Cellulose, the major component of plant cell walls, can be converted to bioethanol and is thus highly studied. In plants, cellulose is produced by cellulose synthase, a processive family-2 glycosyltransferase. In plant cell walls, individual β-1,4-glucan chains polymerized by CesA are assembled into microfibrils that are frequently bundled into macrofibrils. An in vitro system in which cellulose is synthesized and assembled into fibrils would facilitate detailed study of this process. Here, we report the heterologous expression and partial purification of His-tagged CesA5 from Physcomitrella patens Immunoblot analysis and mass spectrometry confirmed enrichment of PpCesA5. The recombinant protein was functional when reconstituted into liposomes made from yeast total lipid extract. The functional studies included incorporation of radiolabeled Glc, linkage analysis, and imaging of cellulose microfibril formation using transmission electron microscopy. Several microfibrils were observed either inside or on the outer surface of proteoliposomes, and strikingly, several thinner fibrils formed ordered bundles that either covered the surfaces of proteoliposomes or were spawned from liposome surfaces. We also report this arrangement of fibrils made by proteoliposomes bearing CesA8 from hybrid aspen. These observations describe minimal systems of membrane-reconstituted CesAs that polymerize β-1,4-glucan chains that coalesce to form microfibrils and higher-ordered macrofibrils. How these micro- and macrofibrils relate to those found in primary and secondary plant cell walls is uncertain, but their presence enables further study of the mechanisms that govern the formation and assembly of fibrillar cellulosic structures and cell wall composites during or after the polymerization process controlled by CesA proteins.

Tip in-light on: Advantages, challenges, and applications of combining AFM and Raman microscopy on biological samples

Scanning probe microscopies and spectroscopies, especially AFM and Confocal Raman microscopy are powerful tools to characterize biological materials. They are both non-destructive methods and reveal mechanical and chemical properties on the micro and nano-scale. In the last years the interest for increasing the lateral resolution of optical and spectral images has driven the development of new technologies that overcome the diffraction limit of light. The combination of AFM and Raman reaches resolutions of about 50-150 nm in near-field Raman and 1.7-50 nm in tip enhanced Raman spectroscopy (TERS) and both give a molecular information of the sample and the topography of the scanned surface. In this review, the mentioned approaches are introduced, the main advantages and problems for application on biological samples discussed and some examples for successful experiments given. Finally the potential of colocated AFM and Raman measurements is shown on a case study of cellulose-lignin films: the topography structures revealed by AFM can be related to a certain chemistry by the colocated Raman scan and additionally the mechanical properties be revealed by using the digital pulsed force mode. Microsc. Res. Tech. 80:30-40, 2017. © 2016 Wiley Periodicals, Inc.

Effect of polymorphs of cellulose nanocrystal on the thermal properties of poly(lactic acid)/cellulose nanocrystal composites

Cellulose nanocrystals (CNCs) with different polymorphs CNC I and II were fabricated from native and mercerized microcrystalline cellulose (MCC) by sulfuric acid hydrolysis. CNC I and II were successfully acetylated by a "green" method, which was performed in an ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF₄). X-ray diffraction (XRD) proved that the crystal structure of CNC I and II was maintained after acetylation. Transmission electron microscopy (TEM) showed the rod-like structure for acetylated CNC I and spherical crystal morphologies for acetylated CNC II. Thermogravimetric analysis (TGA) revealed that the thermal stability of CNC I and II was enhanced after acetylation. The effect of CNC polymorphs on the crystallization behavior and thermal stability of poly(lactic acid)/acetylated CNC (PLA/ACN) composites was investigated by differential scanning calorimetry (DSC) and TGA, respectively. It was found that compared to ACN I, ACN II was better able to promote the cold crystallization of PLA-based composites, and PLA/ ACN II possessed higher thermal stability.

Mechanical properties of natural rubber nanocomposites reinforced with high aspect ratio cellulose nanocrystals isolated from soy hulls

Cellulose nanocrystals (CNCs) were isolated from soy hulls by acid sulfuric hydrolysis. The resulting CNCs were characterized using TEM, AFM, WAXS, elemental analysis and TGA. The CNCs have a high crystallinity, specific surface area and aspect ratio. The aspect ratio (around 100) is the largest ever reported in the literature for a plant cellulose source. These CNCs were used as a reinforcing phase to prepare nanocomposite films by casting/evaporation using natural rubber as matrix. The mechanical properties were studied in both the linear and non-linear ranges. The reinforcing effect was higher than the one observed for CNCs extracted from other sources. It may be assigned not only to the high aspect ratio of these CNCs but also to the stiffness of the percolating nanoparticle network formed within the polymer matrix. Moreover, the sedimentation of CNCs during the evaporation step was found to play a crucial role on the mechanical properties.

Microstructured Multilevel Bacterial Cellulose Allows the Guided Growth of Neural Stem Cells

Repeated photolithographic and etching processes allow the production of multileveled polymer microstructures that can be used as templates to produce bacterial cellulose with defined surfaces on demand. By applying this approach, the bacterial cellulose surface obtains new properties and its use for culturing neural stem cells cellulose substrate topography influences the cell growth in a defined manner.

Strategies for Tailoring the Pore-Size Distribution of Virus Retention Filter Papers

The goal of this work is to demonstrate how the pore-size distribution of the nanocellulose-based virus-retentive filter can be tailored. The filter paper was produced using cellulose nanofibers derived from Cladophora sp. green algae using the hot-press drying at varying drying temperatures. The produced filters were characterized using scanning electron microscopy, atomic force microscopy, and N2 gas sorption analysis. Further, hydraulic permeability and retention efficiency toward surrogate 20 nm model particles (fluorescent carboxylate-modified polystyrene spheres) were assessed. It was shown that by controlling the rate of water evaporation during hot-press drying the pore-size distribution can be precisely tailored in the region between 10 and 25 nm. The mechanism of pore formation and critical parameters are discussed in detail. The results are highly valuable for development of advanced separation media, especially for virus-retentive size-exclusion filtration.

Successive pretreatment and enzymatic saccharification of sugarcane bagasse in a packed bed flow-through column reactor aiming to support biorefineries

A packed bed flow-through column reactor (PBFTCR) was used for pretreatment and subsequent enzymatic hydrolysis of sugarcane bagasse (SCB). Alkaline pretreatment was performed at 70 °C for 4h with fresh 0.3M NaOH solution or with liquor recycled from a previous pretreatment batch. Scheffersomyces stipitis NRRL-Y7124 was used for fermentation of sugars released after enzymatic hydrolysis (20 FPU g(-1) of dry SCB). The highest results for lignin removal were 61% and 52%, respectively, observed when using fresh NaOH or the first reuse of the liquor. About 50% of cellulosic and 57% of hemicellulosic fractions of pretreated SCBs were enzymatically hydrolyzed and the maximum ethanol production was 23.4 g L(-1) (ethanol yield of 0.4 gp gs(-1)), with near complete consumption of both pentoses and hexoses present in the hydrolysate during the fermentation. PBFTCR as a new alternative for SCB-biorefineries is presented, mainly considering its simple configuration and efficiency for operating with a high solid:liquid ratio.

Functional characterization of secondary wall deposition regulating transcription factors MusaVND2 and MusaVND3 in transgenic banana plants

NAM, ATAF, and CUC (NAC) domain-containing proteins are plant-specific transcription factors involved in stress responses and developmental regulation. MusaVND2 and MusaVND3 are vascular-related NAC domain-containing genes encoding for nuclear-localized proteins. The transcript level of MusaVND2 and MusaVND3 are gradually induced after induction of lignification conditions in banana embryogenic cells. Banana embryogenic cells differentiated to tracheary element-like cells after overexpression of MusaVND2 and MusaVND3 with a differentiation frequency of 63.5 and 23.4 %, respectively, after ninth day. Transgenic banana plants overexpressing either of MusaVND2 or MusaVND3 showed ectopic secondary wall deposition as well as transdifferentiation of cells into tracheary elements. Transdifferentiation to tracheary element-like cells was observed in cortical cells of corm and in epidermal and mesophyll cells of leaves of transgenic plants. Elevated levels of lignin and crystalline cellulose were detected in the transgenic banana lines than control plants. The results obtained are useful for understanding the molecular regulation of secondary wall development in banana.

Cellulose Microfibril Formation by Surface-Tethered Cellulose Synthase Enzymes

Cellulose microfibrils are pseudocrystalline arrays of cellulose chains that are synthesized by cellulose synthases. The enzymes are organized into large membrane-embedded complexes in which each enzyme likely synthesizes and secretes a β-(1→4) glucan. The relationship between the organization of the enzymes in these complexes and cellulose crystallization has not been explored. To better understand this relationship, we used atomic force microscopy to visualize cellulose microfibril formation from nickel-film-immobilized bacterial cellulose synthase enzymes (BcsA-Bs), which in standard solution only form amorphous cellulose from monomeric BcsA-B complexes. Fourier transform infrared spectroscopy and X-ray diffraction techniques show that surface-tethered BcsA-Bs synthesize highly crystalline cellulose II in the presence of UDP-Glc, the allosteric activator cyclic-di-GMP, as well as magnesium. The cellulose II cross section/diameter and the crystal size and crystallinity depend on the surface density of tethered enzymes as well as the overall concentration of substrates. Our results provide the correlation between cellulose microfibril formation and the spatial organization of cellulose synthases.

Xyloglucan Deficiency Disrupts Microtubule Stability and Cellulose Biosynthesis in Arabidopsis, Altering Cell Growth and Morphogenesis

Xyloglucan constitutes most of the hemicellulose in eudicot primary cell walls and functions in cell wall structure and mechanics. Although Arabidopsis (Arabidopsis thaliana) xxt1 xxt2 mutants lacking detectable xyloglucan are viable, they display growth defects that are suggestive of alterations in wall integrity. To probe the mechanisms underlying these defects, we analyzed cellulose arrangement, microtubule patterning and dynamics, microtubule- and wall-integrity-related gene expression, and cellulose biosynthesis in xxt1 xxt2 plants. We found that cellulose is highly aligned in xxt1 xxt2 cell walls, that its three-dimensional distribution is altered, and that microtubule patterning and stability are aberrant in etiolated xxt1 xxt2 hypocotyls. We also found that the expression levels of microtubule-associated genes, such as MAP70-5 and CLASP, and receptor genes, such as HERK1 and WAK1, were changed in xxt1 xxt2 plants and that cellulose synthase motility is reduced in xxt1 xxt2 cells, corresponding with a reduction in cellulose content. Our results indicate that loss of xyloglucan affects both the stability of the microtubule cytoskeleton and the production and patterning of cellulose in primary cell walls. These findings establish, to our knowledge, new links between wall integrity, cytoskeletal dynamics, and wall synthesis in the regulation of plant morphogenesis.

Tunable Semicrystalline Thin Film Cellulose Substrate for High-Resolution, In-Situ AFM Characterization of Enzymatic Cellulose Degradation

In the field of enzymatic cellulose degradation, fundamental interactions between different enzymes and polymorphic cellulose materials are of essential importance but still not understood in full detail. One technology with the potential of direct visualization of such bioprocesses is atomic force microscopy (AFM) due to its capability of real-time in situ investigations with spatial resolutions down to the molecular scale. To exploit the full capabilities of this technology and unravel fundamental enzyme-cellulose bioprocesses, appropriate cellulose substrates are decisive. In this study, we introduce a semicrystalline-thin-film-cellulose (SCFTC) substrate which fulfills the strong demands on such ideal cellulose substrates by means of (1) tunable polymorphism via variable contents of homogeneously sized cellulose nanocrystals embedded in an amorphous cellulose matrix; (2) nanoflat surface topology for high-resolution and high-speed AFM; and (3) fast, simple, and reproducible fabrication. The study starts with a detailed description of SCTFC preparation protocols including an in-depth material characterization. In the second part, we demonstrate the suitability of SCTFC substrates for enzymatic degradation studies by combined, individual, and sequential exposure to TrCel6A/TrCel7A cellulases (Trichoderma reesei) to visualize synergistic effects down to the nanoscale.