Production and properties of nanocellulose-reinforced methylcellulose-based biodegradable films

Cellulose nanocrystals reinforced chitosan/titanium dioxide bionanocomposite with enhanced interfacial compatibility: Fabrication, characterization, and application in fresh-cut apple slices

This research aimed to investigate the feasibility of using a bionanocomposite made of chitosan, CNC, and TiO2 nanoparticles to package freshly sliced apples. At the outset, the effect of varying concentrations of CNC (1, 5, and 10 %) and TiO2 (1, 3, and 5 %) on the mechanical, thermal, and water sensitivity characteristics of the chitosan bionanocomposite was studied. Among different combinations, the bionanocomposite containing 10 % CNC and 3 % TiO2 displayed significant enhancements compared to neat chitosan film. Notably, it exhibited a substantial increase in tensile strength (78.2 %), glass transition temperature (26.7 %), and melting temperature (30.0 %) compared to neat chitosan film. Additionally, it demonstrated reduced WVP (27.8 %), FWS (44.4 %), and SR (50.7 %). These improvements were attributed to the synergistic interactions among chitosan, CNC, and TiO2 nanoparticles through hydrogen and oxygen bonding, corroborated by spectral changes in the material. The photocatalytic degradation of ethylene and microbes by UV-A (intermittent) activated TiO2 contained in the developed bionanocomposite was confirmed by the retention of acceptable quality and radical scavenging activity (70 % retention) of fresh-cut apple slices up to 11 days. The developed bionanocomposite can thus preserve the quality of ethylene-producing horticultural produce.

Modified Cellulose Proton-Exchange Membranes for Direct Methanol Fuel Cells

A direct methanol fuel cell (DMFC) is an excellent energy device in which direct conversion of methanol to energy occurs, resulting in a high energy conversion rate. For DMFCs, fluoropolymer copolymers are considered excellent proton-exchange membranes (PEMs). However, the high cost and high methanol permeability of commercial membranes are major obstacles to overcome in achieving higher performance in DMFCs. Novel developments have focused on various reliable materials to decrease costs and enhance DMFC performance. From this perspective, cellulose-based materials have been effectively considered as polymers and additives with multiple concepts to develop PEMs for DMFCs. In this review, we have extensively discussed the advances and utilization of cost-effective cellulose materials (microcrystalline cellulose, nanocrystalline cellulose, cellulose whiskers, cellulose nanofibers, and cellulose acetate) as PEMs for DMFCs. By adding cellulose or cellulose derivatives alone or into the PEM matrix, the performance of DMFCs is attained progressively. To understand the impact of different structures and compositions of cellulose-containing PEMs, they have been classified as functionalized cellulose, grafted cellulose, acid-doped cellulose, cellulose blended with different polymers, and composites with inorganic additives.

Mucoadhesive chitosan-methylcellulose oral patches for the treatment of local mouth bacterial infections

Mucoadhesive buccal patches are dosage forms promising for successful drug delivery. They show the distinctive advantages of long residence time on the oral mucosa and increased in situ drug bioavailability. In this context, electrophoretic deposition (EPD) of chitosan (CS) has been demonstrated as a simple and easily tunable technique to produce mucoadhesive buccal patches. However, CS-based buccal patches may suffer from weak mucoadhesion, which can impair their therapeutic effect. In this work, methylcellulose (MC), a widely investigated biopolymer in the biomedical area, was exploited to increase the mucoadhesive characteristic of pristine CS patches. CS-MC patches were obtained in a one-pot process via EPD, and the possibility of incorporating gentamicin sulfate (GS) as a model of a broad-spectrum antibiotic in the so-obtained patches was investigated. The resulting CS-MC patches showed high stability in a water environment and superior mucoadhesive characteristic (σ_adh = 0.85 ± 0.26 kPa, W_adh = 1192.28 ± 602.36 Pa mm) when compared with the CS control samples (σ_adh = 0.42 ± 0.22 kPa, W_adh = 343.13 ± 268.89 Pa mm), due to both the control of the patch porosity and the bioadhesive nature of MC. Furthermore, GS-loaded patches showed no in vitro cytotoxic effects by challenging L929 cells with material extracts and noteworthy antibacterial activity on both Gram-positive and Gram-negative bacterial strains.

Hydrophobicity and Biodegradability of Silane-Treated Nanocellulose in Biopolymer for High-Grade Packaging Applications

The growing concern about pollution produced by plastic waste and the consequent environmental dangers has led to increased interest in replacing plastics with sustainable and biodegradable alternatives. Biopolymers such as seaweed have been examined for their film-forming characteristics to make edible films for packaging applications. This study aimed to prepare biopolymeric packaging films through a solvent-casting process using natural red seaweed (Kappaphycus alvarezii) and kenaf cellulose nanofiber (CNF), followed by film surface treatment using silane. The hydrophobic properties of the seaweed/CNF biopolymer were examined through water solubility (WS), moisture absorption capacity (MAC), water vapor permeability (WVP), and contact angle (CA) measurements. Fourier transform infra-red (FT-IR) film spectra clearly showed successful modification of the seaweed film (SF) by silane and the incorporation of kenaf CNF over the surface of the seaweed film. The wettability-related analysis showed positive results in determining the modified film's hydrophobicity properties. Film degradation analysis using the soil burial method showed a lower degradation rate for films with a higher CNF loading. Overall, the characterization results of the seaweed/CNF biopolymer film predicted hydrophobicity properties. The slow degradation rate was improved with surface modification using silane treatment and the incorporation of kenaf CNF filler with the seaweed matrix. As a result, we found that the seaweed/CNF biopolymer film could be used as high-grade packaging material in many potential applications.

Human gelatin-based composite hydrogels for osteochondral tissue engineering and their adaptation into bioinks for extrusion, inkjet, and digital light processing bioprinting

The investigation of novel hydrogel systems allows for the study of relationships between biomaterials, cells, and other factors within osteochondral tissue engineering. Three-dimensional (3D) printing is a popular research method that can allow for further interrogation of these questions via the fabrication of 3D hydrogel environments that mimic tissue-specific, complex architectures. However, the adaptation of promising hydrogel biomaterial systems into 3D-printable bioinks remains a challenge. Here, we delineated an approach to that process. First, we characterized a novel methacryloylated gelatin composite hydrogel system and assessed how calcium phosphate and glycosaminoglycan additives upregulated bone- and cartilage-like matrix deposition and certain genetic markers of differentiation within human mesenchymal stem cells (hMSCs), such as RUNX2 and SOX9. Then, new assays were developed and utilized to study the effects of xanthan gum and nanofibrillated cellulose, which allowed for cohesive fiber deposition, reliable droplet formation, and non-fracturing digital light processing (DLP)-printed constructs within extrusion, inkjet, and DLP techniques, respectively. Finally, these bioinks were used to 3D print constructs containing viable encapsulated hMSCs over a 7 d period, where DLP printed constructs facilitated the highest observed increase in cell number over 7 d (∼2.4×). The results presented here describe the promotion of osteochondral phenotypes via these novel composite hydrogel formulations, establish their ability to bioprint viable, cell-encapsulating constructs using three different 3D printing methods on multiple bioprinters, and document how a library of modular bioink additives affected those physicochemical properties important to printability.

Development of a calcium alginate-cellulose nanocrystal-based coating to reduce the impact of oil spills on shorelines

It is well known that oil stranded on shoreline substrates can be difficult to remove and cause serious environmental effects. To address this issue, a calcium alginate-cellulose nanocrystal (CA-CNC)-based coating with a unique surface structure and superhydrophobic properties was developed to reduce the extent of shoreline oiling. The results of batch washing test showed that not only did the introduction of CNC not reduce the oil removal efficiency; it also improved the environmental stability of the coating to resist the effects associated with seawater immersion and erosion (especially in the case of 0.4 wt% of CNC). The oil-repellent performance of the coated gravels implied that both oscillation time and oil concentration had almost no effects on the amount of adhered oil. Assessment of oiling prevention based on the laboratory shoreline tank simulator proved the coated gravel performed very well as more oil floated and less oil remained on substrates and penetrated into the subsurface. Biotoxicity analysis showed that the coating powders reduced impacts on the toxicity of the oil to algae at low doses. There is a good potential for the use of this CA-CNC based coating technique to improve shoreline oil spill response.

The Interactions and Release Kinetics of Sodium Hyaluronate Implemented in Nonionic and Anionic Polymeric Hydrogels, Studied by Immunoenzymatic ELISA Test

Hyaluronan is a natural polymer that was introduced to wound therapy. Formulations based on synthetic polymers such as methylcellulose (MC) and polyacrylic acid (PA) containing hyaluronan (HA) were proposed for the development of prospective wound-healing preparations. The formulations of different carrier concentrations containing a fixed amount of HA were prepared, and their viscosity was measured. The HA release was evaluated by employing the apparatus paddle over a disc. The hydrogels were introduced to the donor chamber, and HA was released to the pH = 7.4 buffer. The amount of HA released was obtained using the ELISA test. The release was analyzed on the basis of different kinetic models: zero-, first-, and second-order kinetics, as well as Higuchi and Korsmeyer–Peppas equations. The release rate constants and the half release time were calculated from these equations. According to the value of the coefficient of the determination, the best model describing the observed process was selected. The comparison between the dissolution profiles was carried out by calculating the difference factor f₁ and the similarity factor f₂. The interaction between the hydrogel components was investigated by Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) measurements. The study revealed that the zero-order equation best described the release of HA from the formulations studied. The FTIR research and the DSC study showed the intermolecular interaction between HA chains in MC-based compositions, as well as between HA and the synthetic polymer in the PA-based formulations. The study revealed that the formulation with a higher concentration of synthetic polymer may prolong the release of HA. The obtained results indicated that the proposed hydrogels have potential for wound healing and may accelerate skin regeneration.

Preparation and Characterization of Nanocellulose/Chitosan Aerogel Scaffolds Using Chemical-Free Approach

Biopolymer-based aerogels are open three-dimensional porous materials that are characterized by outstanding properties, such as a low density, high porosity and high surface area, in addition to their biocompatibility and non-cytotoxicity. Here we fabricated pure and binary blended aerogels from cellulose nanofibers (CNFs) and chitosan (CS), using a chemical-free approach that consists of high-pressure homogenization and freeze-drying. The prepared aerogels showed a different porosity and density, depending on the material and mixing ratio. The porosity and density of the aerogels ranged from 99.1 to 90.8% and from 0.0081 to 0.141 g/cm³, respectively. Pure CNFs aerogel had the highest porosity and lightest density, but it showed poor mechanical properties and a high water absorption capacity. Mixing CS with CNFs significantly enhance the mechanical properties and reduce its water uptake. The two investigated ratios of aerogel blends had superior mechanical and thermal properties over the single-material aerogels, in addition to reduced water uptake and 2-log antibacterial activity. This green fabrication and chemical-free approach could have great potential in the preparation of biopolymeric scaffolds for different biomedical applications, such as tissue-engineering scaffolds.

Effects of ingested nanocellulose and nanochitosan materials on carbohydrate digestion and absorption in an in vitro small intestinal epithelium model

Nanoscale materials derived from natural biopolymers like cellulose and chitosan have many potentially useful agri-food and oral drug delivery applications. Because of their large and potentially bioactive surface areas and other unique physico-chemical properties, it is essential when evaluating their toxicological impact to assess potential effects on the digestion and absorption of co-ingested nutrients. Here, the effects of cellulose nanofibers (CNF), cellulose nanocrystals (CNC), and chitosan nanoparticles (Chnp) on the digestion and absorption of carbohydrates were studied. Starch digestion was assessed by measuring maltose released during simulated digestion of starch solutions. Glucose absorption was assessed by measuring translocation from the resulting digestas across an in vitro transwell tri-culture model of the small intestinal epithelium and calculating the area under the curve increase in absorbed glucose, analogous to the glycemic index. At 1% w/w, CNF and Chnp had small but significant effects (11% decrease and 14% increase, respectively) and CNC had no effect on starch hydrolysis during simulated digestion of a 1% w/w rice starch solution. In addition, at 2% w/w CNC had no effect on amylolysis in 1% solutions of either rice, corn, or wheat starch. Similarly, absorption of glucose from digestas of starch solutions (i.e., from maltose), was unaffected by 1% w/w CNF or CNC, but was slightly increased (10%, p<0.05) by 1% Chnp, possibly due to the slightly higher maltose concentration in the Chnp-containing digestas. In contrast, all of the test materials caused sharp increases (~1.2, 1.5, and 1.6 fold for CNC, CNF, and Chnp, respectively) in absorption of glucose from starch-free digestas spiked with free glucose at a concentration corresponding to complete hydrolysis of 1% w/w starch. The potential for ingested cellulose and chitosan nanomaterials to increase glucose absorption could have important health implications. Further studies are needed to elucidate the mechanisms underlying the observed increases and to evaluate the potential glycemic effects in an intact in vivo system.

Fabrication and Characterization of Chitosan/Cellulose Nanocrystal/Glycerol Bio-Composite Films

Cellulose nanocrystal (CNC)-reinforced bio-composite films containing glycerol were produced using the solution casting technique. The influences of the addition of CNC (2, 4, and 8 wt%) and glycerol (10, 20, and 30 wt%) on the properties of the bio-composite films were studied in the present work. The resulting films were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetry analysis (TGA), and according to their tensile, water absorption, and light transmission behavior. The introduction of 4 wt% CNC into the chitosan film did not affect the thermal stability, but the presence of 20 wt% glycerol reduced the thermal stability. The addition of 4 wt% CNC to the chitosan film increased its tensile strength, tensile modulus, and elongation at break by 206%, 138%, and 277%, respectively. However, adding more than 8 wt% CNC resulted in a drastic reduction in the strength and ductility of the chitosan film. The highest strength and stiffness of the chitosan bio-composite film were attained with 4 wt% CNC and 20 wt% glycerol. The water absorption and light transmission of the chitosan film were reduced dramatically by the presence of both CNC and glycerol.

Cellulose nanocrystals incorporated β-chitosan nanoparticles to enhance the stability and in vitro release of β-galactosidase

Beta-galactosidase (β-gal), catalyzing the transformation of lactose to glucose and galactose, had been encapsulated in β-chitosan nanoparticles (β-CS NPs) in previous work, but they were prone to aggregation and disscociation, resulting in poor bioavailability of β-gal. Herein, we developed cellulose nanocrystals (CNC, as stabilizers and fillers) stabilized β-gal loaded low molecular weight (LMW) β-CS NPs through ionic gelation technology to enhance enzyme activity and further control in vitro release of β-gal. Results showed that particle size and Zeta potential (ZP) of CNCs stabilized β-gal loaded CS NPs were 143.20 nm and -34.70 mV under the optimal conditions, respectively. Structural analysis were employed to study the incorporation of β-gal and CNC into β-CS NPs. In vitro release study conducted at pH 4.5 and 7.4 showed that both β-gal loaded β-CS NPs and CNC stabilized ones retained the release of β-gal for over 12 h. Moreover, CNC stabilized β-gal loaded β-CS NPs retained higher β-gal activity (81.23%) than that of controls (30%) within 2 h. Therefore, it was indicated that CNC incorporated β-CS NPs could serve as non-toxic and effective carriers of β-gal for the treatment of lactose intolerance.

Eco-Friendly High-Performance Poly(methyl methacrylate) Film Reinforced with Methylcellulose

Poly(methyl methacrylate) (PMMA) is a thermoplastic polyester with excellent properties such as lightweight, low price, biocompatibility, and so on. However, its extensive utilization is restricted by the deficiencies of brittleness and poor mechanical properties. In this study, high-performance PMMA films enhanced by methylcellulose (MC) were fabricated by a simple procedure at ambient temperatures. The effects of PMMA/MC mass ratio and thermal compression treatment on mechanical properties (tensile strength and elongation) were systematically investigated. The PMMA/MC films showed remarkably enhanced mechanical properties compared with neat PMMA. The tensile strengths of the PMMA/MC (3:97) and PMMA/MC (1:1) films are higher than that of the PMMA/MC (9:1) film by about 471 and 83%, respectively. The mechanical properties were also improved after thermal compression treatment. Importantly, the PMMA/MC films could be recovered and reused. In addition, the morphologies, crystalline state, and chemical structures of the films were investigated by scanning electron microscopy, X-ray diffraction, and ¹³C NMR spectroscopy. The films are expected to be used as sustainable and potential alternatives to petroleum-based polymer film products because of their simple preparation procedure, high-performance mechanical properties, excellent recycling, eco-friendly features, and scale manufacture.

Facile Fabrication of Methylcellulose/PLA Membrane with Improved Properties

With the rapid exhaustion of fossil resources, and environmental pollution relative to the use of fossil-based products, developing eco-friendly products using biomass and/or biodegradable resources is becoming increasingly conspicuous. In this study, ecofriendly and biodegradable composite membranes containing varying MC/PLA (methylcellulose/polylactic acid) mass ratios were prepared. The properties and structures of the MC/PLA membranes were studied by mechanical testing, 13C NMR techniques, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and hot compression. The MC/PLA membranes displayed markedly improved tensile strength and elongation at the MC/PLA mass ratio range of 99:1 to 9:1. The tensile strength and elongation of the MC/PLA (97:3) membrane was found to be the optimum, at 30% and 35% higher than the neat MC, respectively. It was also found that hot compression could improve the tensile strength and elongation of the membranes. At the same time, the membranes showed enough good thermal stability. In addition, the effect of MC/PLA mass ratio on morphologies of the membranes were studied by microscopy technique.

Modification of Chitosan Membranes via Methane Ion Beam

Chitosan has been used for biomedical applications in recent years, primarily because of its biocompatibility. A chitosan membrane with a 30 μm thickness was prepared and investigated for its surface modification using methane ions. Methane ions were implanted into the chitosan membrane using a Kaufman ion source; bombardment was accomplished using three accelerating voltages of ion beams—30, 55, and 80 kV. The influence of the ion bombardment on morphology, crystallinity, and hydrophilicity was investigated. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy analysis showed that a triplet bond appeared after the implantation of methane ions (acceleration voltage: 80 kV), culminating in the creation of a more amorphous membrane structure. The analyses of atomic force microscopy (AFM) images showed that, with the increase in bombardment energy, the roughness of the surface changed. These results revealed that ion bombardment improved the hydrophilicity of the membranes and the water fluxes of chitosan membranes altered after methane ion bombardment.

Advanced X-ray Shielding Materials Enabled by the Coordination of Well-Dispersed High Atomic Number Elements in Natural Leather

Nowadays, X-rays are playing increasingly important roles in daily life and industrial manufacture, which calls for effective and mobile shielding materials. However, it seems to be a paradox to prepare shielding materials simultaneously achieving excellent X-ray attenuation properties and superior mechanical strength. Here, an advanced leather-based X-ray shielding material containing bismuth and iodine (BiINP-LM) is prepared, and the stable and well-dispersed loading of high-Z element components is enabled by favorable interactions between bismuth iodide and leather, i.e., coordination, hydrogen bonds, and electrostatic attractions. A piece of BiINP-LM with 1.00 mm thickness displays an excellent X-ray attenuation efficiency of more than 90% in the photon energy range below 50 keV and 65% at 83 keV, which averagely exceeds ∼3% than that of the 0.25 mm lead plate and ∼5% than that of the 0.65 mm commercial lead apron. Additionally, the coordination between bismuth and leather provides an enhanced tensile and tear strength of ∼10-fold and 3-fold compared with the lead apron. It is worth mentioning that BiINP-LM also displays extra high water-vapor permeability, which is ∼50-fold more than the lead apron. Overall, this work opens up a new prospect for preparing advanced X-ray shielding materials with both excellent X-ray attenuation and outstanding physiomechanical performances.

Effects of ingested nanocellulose on intestinal microbiota and homeostasis in Wistar Han rats

Micron scale cellulose materials are "generally regarded as safe" (GRAS) as binders and thickeners in food products. However, nanocellulose materials, which have unique properties that can improve food quality and safety, have not received US-Food and Drug Administration (FDA) approval as food ingredients. In vitro and in vivo toxicological studies of ingested nanocellulose revealed minimal cytotoxicity, and no subacute in vivo toxicity. However, ingested materials may modulate gut microbial populations, or alter aspects of intestinal function not elucidated by toxicity testing, which could have important health implications. Here, we report the results of studies conducted in a rat gavage model to assess the effects of ingested cellulose nanofibrils (CNF) on the fecal microbiome and metabolome, intestinal epithelial expression of cell junction genes, and ileal cytokine production. Feces, plasma, and ilea were collected from Wistar Han rats before and after five weeks of biweekly gavages with water or cream, with or without 1% CNF. CNF altered microbial diversity, and diminished specific species that produce short chain fatty acids, and that are associated with increased serum insulin and IgA production. CNF had few effects on the fecal metabolome, with significant changes in only ten metabolites of 366 measured. Exposure to CNF also altered expression of epithelial cell junction genes, and increased production of cytokines that modulate proliferation of CD8 T cells. These perturbations likely represent initiation of an adaptive immune response, however, no associated pathology was seen within the duration of the study. Additional studies are needed to better understand the health implications of these changes in long term.

Cellulose Nanocrystal Reinforced Chitosan Based UV Barrier Composite Films for Sustainable Packaging

In this study, green composite films based on cellulose nanocrystal/chitosan (CNC/CS) were fabricated by solution casting. FTIR, XRD, SEM, and TEM characterizations were conducted to determine the structure and morphology of the prepared films. The addition of only 4 wt.% CNC in the CS film improved the tensile strength and Young's modulus by up to 39% and 78%, respectively. Depending on CNC content, the moisture absorption decreased by 34.1-24.2% and the water solubility decreased by 35.7-26.5% for the composite films compared with neat CS film. The water vapor permeation decreased from 3.83 × 10-11 to 2.41 × 10-11 gm-1 s-1Pa-1 in the CS-based films loaded with (0-8 wt.%) CNC. The water and UV barrier properties of the composite films showed better performance than those of neat CS film. Results suggested that CNC/CS nanocomposite films can be used as a sustainable packaging material in the food industry.

Toxicological effects of ingested nanocellulose in in vitro intestinal epithelium and in vivo rat models

Cellulose is widely used as a thickener and filler in foods and drugs. It has been designated "generally regarded as safe" (GRAS). Nanocellulose (NC) has many additional potential applications designed to improve food quality and safety, but has not yet been designated as GRAS. Here we present results of toxicological studies of ingested NC in physiologically relevant in vitro and in vivo systems. In vitro studies employed a gastrointestinal tract simulator to digest two widely-used forms of NC, nanocellulose fibrils (CNF) and cellulose nanocrystals (CNC), at 0.75 and 1.5% w/w, in a fasting diet as well as in a standardized food model based on the average American diet. A triculture model of small intestinal epithelium was used to assess effects of a 24-hour incubation with the digested products (digesta) on cell layer integrity, cytotoxicity and oxidative stress. Other than a 10% increase over controls in reactive oxygen species (ROS) production with 1.5% w/w CNC, no significant changes in cytotoxicity, ROS or monolayer integrity were observed. In vivo toxicity was evaluated in rats gavaged twice weekly for five weeks with 1% w/w suspensions of CNF in either water or cream. Blood, serum, lung, liver, kidney, and small intestine were collected for analysis. No significant differences in hematology, serum markers or histology were observed between controls and rats given CNF suspensions. These findings suggest that ingested NC has little acute toxicity, and is likely non-hazardous when ingested in small quantities. Additional chronic feeding studies are required to assess long term effects, and potential detrimental effects on the gut microbiome and absorbance of essential micronutrients. These studies are underway, and their outcome will be reported in the near future.

Leaf-inspired multiresponsive MXene-based actuator for programmable smart devices

Natural leaves, with elaborate architectures and functional components, harvest and convert solar energy into chemical fuels that can be converted into energy based on photosynthesis. The energy produced leads to work done that inspired many autonomous systems such as light-triggered motion. On the basis of this nature-inspired phenomenon, we report an unprecedented bilayer-structured actuator based on MXene (Ti3C2T x )-cellulose composites (MXCC) and polycarbonate membrane, which mimic not only the sophisticated leaf structure but also the energy-harvesting and conversion capabilities. The bilayer actuator features multiresponsiveness, low-power actuation, fast actuation speed, large-shape deformation, programmable adaptability, robust stability, and low-cost facile fabrication, which are highly desirable for modern soft actuator systems. We believe that these adaptive soft systems are attractive in a wide range of revolutionary technologies such as soft robots, smart switch, information encryption, infrared dynamic display, camouflage, and temperature regulation, as well as human-machine interface such as haptics.

Versatile Application of Nanocellulose: From Industry to Skin Tissue Engineering and Wound Healing

Nanocellulose is cellulose in the form of nanostructures, i.e., features not exceeding 100 nm at least in one dimension. These nanostructures include nanofibrils, found in bacterial cellulose; nanofibers, present particularly in electrospun matrices; and nanowhiskers, nanocrystals, nanorods, and nanoballs. These structures can be further assembled into bigger two-dimensional (2D) and three-dimensional (3D) nano-, micro-, and macro-structures, such as nanoplatelets, membranes, films, microparticles, and porous macroscopic matrices. There are four main sources of nanocellulose: bacteria (Gluconacetobacter), plants (trees, shrubs, herbs), algae (Cladophora), and animals (Tunicata). Nanocellulose has emerged for a wide range of industrial, technology, and biomedical applications, namely for adsorption, ultrafiltration, packaging, conservation of historical artifacts, thermal insulation and fire retardation, energy extraction and storage, acoustics, sensorics, controlled drug delivery, and particularly for tissue engineering. Nanocellulose is promising for use in scaffolds for engineering of blood vessels, neural tissue, bone, cartilage, liver, adipose tissue, urethra and dura mater, for repairing connective tissue and congenital heart defects, and for constructing contact lenses and protective barriers. This review is focused on applications of nanocellulose in skin tissue engineering and wound healing as a scaffold for cell growth, for delivering cells into wounds, and as a material for advanced wound dressings coupled with drug delivery, transparency and sensorics. Potential cytotoxicity and immunogenicity of nanocellulose are also discussed.

Reducing Intestinal Digestion and Absorption of Fat Using a Nature-Derived Biopolymer: Interference of Triglyceride Hydrolysis by Nanocellulose

Engineered nanomaterials are increasingly added to foods to improve quality, safety, or nutrition. Here we report the ability of ingested nanocellulose (NC) materials to reduce digestion and absorption of ingested fat. In the small intestinal phase of an acellular simulated gastrointestinal tract, the hydrolysis of free fatty acids (FFA) from triglycerides (TG) in a high-fat food model was reduced by 48.4% when NC was added at 0.75% w/w to the food, as quantified by pH stat titration, and by 40.1% as assessed by fluorometric FFA assay. Furthermore, translocation of TG and FFA across an in vitro cellular model of the intestinal epithelium was significantly reduced by the presence of 0.75% w/w NC in the food (TG by 52% and FFA by 32%). Finally, in in vivo experiments, the postprandial rise in serum TG 1 h after gavage with the high fat food model was reduced by 36% when 1.0% w/w NC was administered with the food. Scanning electron microscopy and molecular dynamics studies suggest two primary mechanisms for this effect: (1) coalescence of fat droplets on fibrillar NC (CNF) fibers, resulting in a reduction of available surface area for lipase binding and (2) sequestration of bile salts, causing impaired interfacial displacement of proteins at the lipid droplet surface and impaired solubilization of lipid digestion products. Together these findings suggest a potential use for NC, as a food additive or supplement, to reduce absorption of ingested fat and thereby assist in weight loss and the management of obesity.

Characterization of Nanofibrillated Cellulose Produced by Different Methods from Cabbage Outer Leaves

The potential use of cabbage outer leaves as a starting material for the production of nanofibrillated cellulose (NFC) was investigated. Chemical-free pretreatment methods, namely, autoclaving, ultrasonication (US), and high-shear homogenization (HS), were applied to remove noncellulosic components from cabbage cell walls prior to defibrillation, which was conducted by subjecting a pretreated sample to HS and then high-pressure homogenization. The sample undergone autoclaving at 130 °C for 2 hr was noted to contain a significantly higher cellulose content (36.5% dry mass) compared with the fresh leaves (12.48% dry mass). This led to an increase in the crystallinity index (CI) of the autoclaved cabbages from 30.8% to 50.7%. Further increase in the cellulose content (47.0% to 49.2% dry mass) was observed when subjecting the autoclaved sample to either US at 37 kHz for 1 hr, HS at 3800 × g for 15 min or HS followed by US at the aforementioned conditions. After pretreatment and defibrilllation, a suspension of NFC with the diameters of 4 to 50 nm was obtained, with the CI of 59.1% to 66.7%. Such a suspension exhibited a gel-like behavior with tan δ in the range of 0.12 to 0.13; the suspension exhibited a similar behavior to that prepared by the conventional chemical pretreatment method.

PRACTICAL APPLICATION

NFC could be produced from cabbage outer leaves, which are an abundantly available by-product of a vegetable processing plant, via the combined hydrothermal and mechanical pretreatment without the use of any chemicals. This chemical-free preparation process is highly desirable as it leaves no residues in the product and causes no chemical waste that needs to be treated. Cabbage-based NFC also exhibits similar characteristics to that prepared via a chemically treated route.

Covalent Tethering of Temperature Responsive pNIPAm onto TEMPO-Oxidized Cellulose Nanofibrils via Three-Component Passerini Reaction

A critical challenge in the application of functional cellulose fibrils is to perform efficient surface modification without disrupting the original properties. Three-component Passerini reaction (Passerini 3-CR) is regarded as an effective functionalization approach which can be carried out under mild and fast reaction condition. In this study, we investigated the application of Passerini 3-CR for the synthesis of thermoresponsive cellulose fibrils by covalently tethering poly(N-isopropylacrylamide) in aqueous condition at ambient temperature. The three components, a TEMPO-oxidized cellulose nanofiber bearing carboxylic acid moieties (TOCN-COOH), a functionalized polymer with aldehyde group (pNIPAm-COH) and a cyclohexyl isocyanide, were reacted in one pot resulting in 36% of grafting efficiency within 30 min. The chemical coupling was evidenced by improved aqueous dispersibility, which was further confirmed by FT-IR, TGA, UV-vis, and turbidity study. It was observed that the grafting efficiency is strongly dependent on the chain length of the polymer. Furthermore, AFM and X-ray diffraction measurements affirmed the suitability of the proposed method for chemical modification of cellulose nanofibers without significantly compromising the original morphology and structural integrity.

Review of recent research on flexible multifunctional nanopapers

Traditional paper and papermaking have struggled with a declining market during the last few decades. However, the incorporation of nanotechnology into papermaking has brought possibilities to develop low-cost, biocompatible and flexible products with sophisticated functionalities. The functionality of nanopapers emerges from the intrinsic properties of the nanofibrous network, the additional loading of specific nanomaterials (NMs), or the additional deposition and patterning of thin films of nanomaterials on the paper surface. A successful development of functional nanopapers requires understanding how the nanopaper matrix, nanofillers, nanocoating pigments, nanoprinting inks, processing additives and manufacturing processes all interact to provide the intended functionality. This review addresses the emerging area of functional nanopapers. This review discusses flexible and multifunctional nanopapers, NMs being used in nanopaper making, manufacturing techniques, and functional applications that provide new important possibilities to utilize papermaking technology. The interface where NM research meets traditional papermaking has important implications for food packaging, energy harvesting and energy storage, flexible electronics, low-cost devices for medical diagnostics, and numerous other areas.

An integrated methodology for assessing the impact of food matrix and gastrointestinal effects on the biokinetics and cellular toxicity of ingested engineered nanomaterials

BACKGROUND

Engineered nanomaterials (ENMs) are increasingly added to foods to improve their quality, sensory appeal, safety and shelf-life. Human exposure to these ingested ENMs (iENMS) is inevitable, yet little is known of their hazards. To assess potential hazards, efficient in vitro methodologies are needed to evaluate particle biokinetics and toxicity. These methodologies must account for interactions and transformations of iENMs in foods (food matrix effect) and in the gastrointestinal tract (GIT) that are likely to determine nano-biointeractions. Here we report the development and application of an integrated methodology consisting of three interconnected stages: 1) assessment of iENM-food interactions (food matrix effect) using model foods; 2) assessment of gastrointestinal transformations of the nano-enabled model foods using a three-stage GIT simulator; 3) assessment of iENMs biokinetics and cellular toxicity after exposure to simulated GIT conditions using a triculture cell model. As a case study, a model food (corn oil-in-water emulsion) was infused with Fe2O3 (Iron(III) oxide or ferric oxide) ENMs and processed using this three-stage integrated platform to study the impact of food matrix and GIT effects on nanoparticle biokinetics and cytotoxicity .

METHODS

A corn oil in phosphate buffer emulsion was prepared using a high speed blender and high pressure homogenizer. Iron oxide ENM was dispersed in water by sonication and combined with the food model. The resulting nano-enabled food was passed through a three stage (mouth, stomach and small intestine) GIT simulator. Size distributions of nano-enabled food model and digestae at each stage were analyzed by DLS and laser diffraction. TEM and confocal imaging were used to assess morphology of digestae at each phase. Dissolution of Fe2O3 ENM along the GIT was assessed by ICP-MS analysis of supernatants and pellets following centrifugation of digestae. An in vitro transwell triculture epithelial model was used to assess biokinetics and toxicity of ingested Fe2O3 ENM. Translocation of Fe2O3 ENM was determined by ICP-MS analysis of cell lysates and basolateral compartment fluid over time.

RESULTS

It was demonstrated that the interactions of iENMs with food and GIT components influenced nanoparticle fate and transport, biokinetics and toxicological profile. Large differences in particle size, charge, and morphology were observed in the model food with and without Fe2O3 and among digestae from different stages of the simulated GIT (mouth, stomach, and small intestine). Immunoflorescence and TEM imaging of the cell culture model revealed markers and morphology of small intestinal epithelium including enterocytes, goblet cells and M cells. Fe2O3 was not toxic at concentrations tested in the digesta. In biokinetics studies, translocation of Fe2O3 after 4 h was <1% and ~2% for digesta with and without serum, respectively, suggesting that use of serum proteins alters iENMs biokinetics and raises concerns about commonly-used approaches that neglect iENM - food-GIT interactions or dilute digestae in serum-containing media.

CONCLUSIONS

We present a simple integrated methodology for studying the biokinetics and toxicology of iENMs, which takes into consideration nanoparticle-food-GIT interactions. The importance of food matrix and GIT effects on biointeractions was demonstrated, as well as the incorporation of these critical factors into a cellular toxicity screening model. Standardized food models still need to be developed and used to assess the effect of the food matrix effects on the fate and bioactivity of iENMs since commercial foods vary considerably in their compositions and structures.

Utilization of flax (Linum usitatissimum) cellulose nanocrystals as reinforcing material for chitosan films

Use of plastic based packaging tools is causing both health and economic problems. To overcome this situation, researchers are focusing on the use of different biomaterials such as chitosan and cellulose. The current study was conducted to check the effect of flax (Linum usitatissimum) cellulose nanocrystals (CNC) on mechanical and barrier properties of chitosan-based films. CNC was incorporated in different concentrations (5, 10, 20 and 30%). CNC was isolated from flax fiber using acid hydrolysis method. Tensile strength (TS) and young modulus (YM) values increased with the increase of CNC concentration. Chitosan film with 20% CNC revealed the highest YM value as 52.35MPa. No significant improvement was recorded in water vapor permeability due to overall lower film crystallinity. All the films were observed to be transparent up to an acceptable level. SEM and AFM analysis confirmed the homogeneity of films. A gradual enhancement was recorded in the antimicrobial activity of chitosan/CNC composite films. No significant improvement revealed in the thermal stability of composites.

Synthesis and Characterization of Methyl Cellulose/Keratin Hydrolysate Composite Membranes

It is known that aqueous keratin hydrolysate solutions can be produced from feathers using superheated water as solvent. This method is optimized in this study by varying the time and temperature of the heat treatment in order to obtain a high solute content in the solution. With the dissolved polypeptides, films are produced using methyl cellulose as supporting material. Thereby, novel composite membranes are produced from bio-waste. It is expected that these materials exhibit both protein and polysaccharide properties. The influence of the embedded keratin hydrolysates on the methyl cellulose structure is investigated using Fourier transform infrared spectroscopy (FTIR) and wide angle X-ray diffraction (WAXD). Adsorption peaks of both components are present in the spectra of the membranes, while the X-ray analysis shows that the polypeptides are incorporated into the semi-crystalline methyl cellulose structure. This behavior significantly influences the mechanical properties of the composite films as is shown by tensile tests. Since further processing steps, e.g., crosslinking, may involve a heat treatment, thermogravimetric analysis (TGA) is applied to obtain information on the thermal stability of the composite materials.