Nanofibrillar Cellulose Research Articles

Fabrication and properties of low crystallinity nanofibrillar cellulose and a nanofibrillar cellulose–graphene oxide composite

Nanofibrillar cellulose of low crystallinity and a nanofibrillar cellulose–graphene oxide composite with excellent properties were fabricated in a facile way.

TEMPO oxidized cellulose thin films analysed by QCM-D and AFM

2,2,6,6-Tetramethylpiperidine 1-oxyl (TEMPO) oxidized cellulose has quickly become a highly utilized material in the production of nanofibrillar cellulose (NFC) and a functionalization strategy for cellulosic materials. In this study we have prepared oxidized cellulose films by TEMPO oxidation and used a quartz crystal microbalance with dissipation monitoring to analyse changes in the film properties. Oxidation was performed at different pH values and reaction times for amorphous and NFC surfaces were also varied. By varying TEMPO oxidation conditions the carboxylation efficiency, stability, and topographical sensitivity of TEMPO oxidation can be optimized for production of a required functionalization level without causing unwanted damage to the cellulosic material. The topographical changes on oxidized cellulose films were further characterized by AFM. Although both surfaces reacted in a similar manner to oxidation, the NFC film was found to be more stable during the oxidation than amorphous cellulose film. The results in this article can be utilized for the functionalization of cellulosic materials in a more controlled manner and for tuning the required carboxylation levels without causing permanent changes to the functionalized cellulosic material.

Analysis of the compressive response of Nano Fibrillar Cellulose foams

Nano Fibrillar Cellulose (NFC) is fast emerging as a biomaterial with promising applications, one of which is cellular foam. The inner structure of the foam can take various shapes and hierarchical micro-structures depending on the manufacturing parameters. The compressive response of foams developed from these materials is currently a primary criterion for the material development. In this work, we focus on the connection between the non-linear part of the response and the inner structure of the material. We study the effect of internal contact and its contribution to gradual stiffening in the energy absorbing region and accelerated stiffening in the densification region of the large strain compressive response. We use the finite element method in this study and discuss the applicability and efficiency of different modelling techniques by considering well defined geometries and available experimental data. The relative contribution of internal contact is singled out and mapped onto the overall compressive response of the material. The effect of initial non-straightness of the cell walls is studied through superposing differing percentages of the buckling modes on the initial geometry. The initial non-straightness is seen to have a significant effect for only strains up to 1%. The secant modulus measured at slightly higher strains of 4%, demonstrates lesser effect from the non-straightness of cell walls. The simulations capture the compressive response well into the densification regime and there is an order of magnitude agreement in between simulations and experiments. We observed that internal contact is crucial for capturing the trend of compressive response.

Technetium-99m-labeled nanofibrillar cellulose hydrogel for in vivo drug release

Nanoscale celluloses have recently gained an increasing interest in modern medicine. In this study, we investigated the properties of plant derived nanofibrillar cellulose (NFC) as an injectable drug releasing hydrogel in vivo. We demonstrated a reliable and efficient method of technetium-99m-NFC labeling, which enables us to trace the in vivo localization of the hydrogel. The release and distribution of study compounds from the NFC hydrogel after subcutaneous injection in the pelvic region of BALB/c mice were examined with a multimodality imaging device SPECT/CT. The drug release profiles were simulated by 1-compartmental models of Phoenix® WinNonlin®. The NFC hydrogel remained intact at the injection site during the study. The study compounds are more concentrated at the injection site when administered with the NFC hydrogel compared with saline solutions. In addition, the NFC hydrogel reduced the elimination rate of a large compound, technetium-99m-labeled human serum albumin by 2 folds, but did not alter the release rate of a small compound 123I-β-CIT (a cocaine analogue). In conclusion, the NFC hydrogels is easily prepared and readily injected, and it has potential use as a matrix for controlled release or local delivery of large compounds. The interactions between NFC and specific therapeutic compounds are possible and should be investigated further.

Extraordinary reinforcement effect of three-dimensionally nanoporous cellulose gels in poly(ε-caprolactone) bionanocomposites.

Three-dimensionally nanoporous cellulose gels (NCG) were prepared by dissolution and coagulation of cellulose from aqueous alkali hydroxide-urea solution, and used to fabricate NCG/poly(ε-caprolactone) (PCL) nanocomposites by in situ ring-opening polymerization of ε-CL monomer in the NCG. The NCG content of the NCG/PCL nanocomposite could be controlled between 7 and 38% v/v by changing water content of starting hydrogel by compression dewatering. FT-IR and solid-state (13)C NMR showed that the grafting of PCL onto cellulose are most likely occurred at the C6-OH groups and the grafting percentage of PCL is 25 wt % for the nanocomposite with 7% v/v NCG. (1)H NMR, XRD, and DSC results indicate that the number-average molecular weight and crystal formation of PCL in the nanocomposites are remarkably restricted by the presence of NCG. AFM images confirm that the interconnected nanofibrillar cellulose network structure of NCG are finely distributed and preserved well in the PCL matrix after polymerization. DMA results show remarkable increase in tensile storage modulus of the nanocomposites above glass transition and melting temperatures of the PCL matrix. The percolation model was used to evaluate the mechanical properties of the nanocomposites, in which stress transfer among the interconnected nanofibrillar network is facilitated through strong intermolecular hydrogen bonding and entanglement of cellulose nanofibers.

Green Catalytic Approach for the Synthesis of Functionalized Nanocellulose from Palm Tree Biomass

Oil palm is a major agricultural product in Malaysia and it covers approximately 5 million hectares of land. Palm tree biomass is a by-product of oil palm cultivation. Biomass is a complex structure composed of cellulose, hemicelluloses and lignin. Cellulose, which gives the mechanical properties to the natural fiber, is organized in micro-fibrils enclosed by the other two main components: hemicellulose and lignin. Cellulose microfibrils can be found as intertwined microfibrils in the cell wall (220 μm in diameter and 100 40,000 nm in length). Cellulose microfibrils are in turn exist in cellulose nanofibers having diameter of 550 nm and length several millimeters conformed by nanocrystalline domains and amorphous regions. Nanocellulose, which is a degradation product of cellulose, has recently come to public attention because of its great mechanical properties combined with low molecular weight, renewability and biodegradability. Another advantage of nanofibrillar cellulose is that their production does not interfere with the food chain, therefore, they can be considered as socially sustainable raw materials. However, before the nanocellulose can be fully utilized to fabricate smart and environmentally friendly new high-tech products. Most common applications of nanocellulose are for polymer composite, bioplastics, films, foams, gels, cosmetics, dimensionally stable thickener and emulsion, implant material, biodegradable tissue scaffold, suture, drug delivery vehicle, filter paper, speaker membrane, battery membrane, concrete, drilling muds & enhanced oil recovery, water treatment, etc. Several methods have been proposed for the extraction/preparations of nanocellulose which involve extensive chemical and mechanical treatments which are not environmentally friendly. This paper reviewed various methods along with their limitations for the controlled structure synthesis of functionalized nanocellulose from palm tree biomass. The green catalytic approaches are schematically outlined.

Differentiation of liver progenitor cell line to functional organotypic cultures in 3D nanofibrillar cellulose and hyaluronan-gelatin hydrogels

Physiologically relevant hepatic cell culture models must be based on three-dimensional (3D) culture of human cells. However, liver cells are generally cultured in two-dimensional (2D) format that deviates from the normal in vivo morphology. We generated 3D culture environment for HepaRG liver progenitor cells using wood-derived nanofibrillar cellulose (NFC) and hyaluronan-gelatin (HG) hydrogels. Culture of undifferentiated HepaRG cells in NFC and HG hydrogels induced formation of 3D multicellular spheroids with apicobasal polarity and functional bile canaliculi-like structures, structural hallmarks of the liver tissue. Furthermore, hepatobiliary drug transporters, MRP2 and MDR1, were localized on the canalicular membranes of the spheroids and vectorial transport of fluorescent probes towards the biliary compartment was demonstrated. Cell culture in 3D hydrogel supported the mRNA expression of hepatocyte markers (albumin and CYP3A4), and metabolic activity of CYP3A4 in the HepaRG cell cultures. On the contrary, the 3D hydrogel cultures with pre-differentiated HepaRG cells showed decreasing expression of albumin and CYP3A4 transcripts as well as CYP3A4 activity. It is concluded that NFC and HG hydrogels expedite the hepatic differentiation of HepaRG liver progenitor cells better than the standard 2D culture environment. This was shown as improved cell morphology, expression and localization of hepatic markers, metabolic activity and vectorial transport. The NFC and HG hydrogels are promising materials for hepatic cell culture and tissue engineering.

Synergistic Toughening of Bioinspired Poly(vinyl alcohol)–Clay–Nanofibrillar Cellulose Artificial Nacre

Inspired by the layered aragonite platelet/nanofibrillar chitin/protein ternary structure and integration of extraordinary strength and toughness of natural nacre, artificial nacre based on clay platelet/nanofibrillar cellulose/poly(vinyl alcohol) is constructed through an evaporation-induced self-assembly technique. The synergistic toughening effect from clay platelets and nanofibrillar cellulose is successfully demonstrated. The artificial nacre achieves an excellent balance of strength and toughness and a fatigue-resistant property, superior to natural nacre and other conventional layered clay/polymer binary composites.

Mechanical behavior of transparent nanofibrillar cellulose–chitosan nanocomposite films in dry and wet conditions

Transparent, biocompatible and biodegradable chitosan (CS) nanocomposite films reinforced with nanofibrillar cellulose (NFC) were prepared by solution casting. The effects of NFC content on the mechanical properties in dry and wet conditions were investigated. The incorporation of NFC significantly enhanced the mechanical properties, especially in wet conditions. The ultimate tensile strength and Young׳s modulus of chitosan were improved by 12 times and 30 times, respectively, for the nanocomposite containing 32wt% of NFC in wet conditions. The mechanism of the remarkable reinforcements was studied by analyzing the swelling behavior of NFC–CS nanocomposites. The mechanical properties of wet NFC–CS nanocomposite films matched well with those of human skin, which demonstrate potential for uses as artificial skin and wound dressings.

Highly tough and transparent layered composites of nanocellulose and synthetic silicate

A highly tough and transparent film material was prepared from synthetic saponite (SPN) nanoplatelets of low aspect ratios and nanofibrillar cellulose. The nanofibrillar cellulose was chemically modified by topological surface oxidation using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) as a catalyst. Both synthetic SPN nanoplatelets and TEMPO-oxidized cellulose nanofibrils (TOCNs) have abundant negative charges in high densities on their surfaces and are dispersed in water at the individual nanoelement level. Layered nanocomposite structures of the SPN nanoplatelets and TOCNs were formed through a simple cast-drying process of the mixed aqueous dispersions. The TOCN/SPN composites with 0-50% w/w SPN content were optically transparent. Mechanical properties of the TOCN/SPN composites varied depending on the SPN content. The composite with 10% w/w SPN content (5.6% volume fraction) exhibited characteristic mechanical properties: Young's modulus of 14 GPa, tensile strength of 420 MPa, and strain-to-failure of 10%. The work of fracture of the composites increased from 4 to 30 MJ m(-3)- or by more than 700%--as the SPN content was increased from 0 to 10% w/w. This surprising improvement in toughness was interpreted based on a model for fracture of polymer composites reinforced with low-aspect-ratio platelets.

Deriving a process viscosity for complex particulate nanofibrillar cellulose gel-containing suspensions

Deriving a process viscosity for complex particulate nanofibrillar cellulose gel-containing suspensions

The Use of Nanofibrillar Cellulose Hydrogel As a Flexible Three-Dimensional Model to Culture Human Pluripotent Stem Cells

Human embryonic stem cells and induced pluripotent stem cells have great potential in research and therapies. The current in vitro culture systems for human pluripotent stem cells (hPSCs) do not mimic the three-dimensional (3D) in vivo stem cell niche that transiently supports stem cell proliferation and is subject to changes which facilitate subsequent differentiation during development. Here, we demonstrate, for the first time, that a novel plant-derived nanofibrillar cellulose (NFC) hydrogel creates a flexible 3D environment for hPSC culture. The pluripotency of hPSCs cultured in the NFC hydrogel was maintained for 26 days as evidenced by the expression of OCT4, NANOG, and SSEA-4, in vitro embryoid body formation and in vivo teratoma formation. The use of a cellulose enzyme, cellulase, enables easy cell propagation in 3D culture as well as a shift between 3D and two-dimensional cultures. More importantly, the removal of the NFC hydrogel facilitates differentiation while retaining 3D cell organization. Thus, the NFC hydrogel represents a flexible, xeno-free 3D culture system that supports pluripotency and will be useful in hPSC-based drug research and regenerative medicine.

Solvent impact on esterification and film formation ability of nanofibrillated cellulose

In this study we have manufactured nanofibrillar cellulose and modified the fibre surface with ester groups in order to hydrophobise the surface. Nanofibrillated cellulose was chosen to demonstrate the phenomena, since due to its high surface area the effects at issue are pronounced. The prepared NFC ester derivatives were butyrate, hexanoate, benzoate, naphtoate, diphenyl acetate, stearate and palmitate. X-ray photoelectron spectroscopy, solid state NMR and contact angle measurements were used to demonstrate the chemical changes taking place on the cellulose surface. NFC ester derivatives can be prepared after a careful solvent exchange to a water-free solvent medium has been carried out. Butyl and palmitoyl esters were chosen for film forming tests due to the difference in their carbon chain lengths, and their contact angles and water vapour and oxygen permeation rates were studied. The prepared nanocellulose esters show increased hydrophobicity even at very low levels of substitution and readily form films when the films are prepared from acetone dispersions. The permeation rates suggest a potential use as barrier materials.

Soy protein–nanocellulose composite aerogels

Organic aerogels based on two important and widely abundant renewable resources, soy proteins (SP) and nanofibrillar cellulose (NFC) are developed from precursor aqueous dispersions and a facile method conducive of channel- and defect-free systems after cooling and freeze-drying cycles that yielded apparent densities on the order of 0.1 g/cm3. NFC loading drives the internal morphology of the composite aerogels to transition from network- to fibrillar-like, with high density of interconnected cells. Composite aerogels with SP loadings as high as ca. 70 % display a compression modulus of 4.4 MPa very close to that obtained from reference, pure NFC aerogels. Thus, the high compression modulus of the composite system is not compromised as long as a relatively low amount of reinforcing NFC is present. The composite materials gain moisture (up to 5 %) in equilibrium with 50 % RH air, independent of SP content. Furthermore, their physical integrity is unchanged upon immersion in polar and non-polar solvents. Fast liquid sorption rates are observed in the case of composite aerogels in contact with hexane. In contrast, water sorption is modulated by the chemical composition of the aerogel, with an important contribution from swelling. The potential functionalities of the newly developed SP–NFC composite green materials can benefit from the reduced material cost and the chemical features brought about the amino acids present in SPs.

Cellulose Nanofibrils

Cellulose nanofi brils (CNF), also known as nanofi brillar cellulose (NFC), are an advanced biomaterial made mainly from renewable forest and agricultural resources that have demonstrated exceptional performance in composites. In addition, they have been utilized in barrier coatings, food, transparent fl exible fi lms and other applications. Research on CNF has advanced rapidly over the last decade and several of the fundamental questions about production and characterization of CNF have been addressed. An interesting shift in focus in the recent reported literature indicates increased efforts aimed at taking advantage of the unique properties of CNF. This includes its nanoscale dimensions, high surface area, unique morphology, low density and mechanical strength. In addition, CNF can be easily (chemically) modified and is readily available, renewable, and biodegradable. These facts are expected to materialize in a more widespread use of CNF. However, there is no clear indication of the most promising avenues for CNF deployment in commercial products. This review attempts to illustrate some exciting opportunities for CNF, specifi cally, in the development of aerogels, composites, bioactive materials and inorganic/organic hybrid materials.

Evaluation of drug interactions with nanofibrillar cellulose

Nanofibrillar cellulose (NFC) (also referred to as cellulose nanofibers, nanocellulose, microfibrillated, or nanofibrillated cellulose) has recently gotten wide attention in various research areas and it has also been studied as excipient in formulation of the pharmaceutical dosage forms. Here, we have evaluated the interactions between NFC and the model drugs of different structural characteristics (size, charge, etc.). The series of permeation studies were utilized to evaluate the ability of the drugs in solution to diffuse through the thin, porous, dry NFC films. An incubation method was used to determine capacity of binding of chosen model drugs to NFC as well as isothermal titration calorimetry (ITC) to study thermodynamics of the binding process. A genetically engineered fusion protein carrying double cellulose binding domain was used as a positive control since its affinity and capacity of binding for NFC have already been reported. The permeation studies revealed the size dependent diffusion rate of the model drugs through the NFC films. The results of both binding and ITC studies showed that the studied drugs bind to the NFC material and indicated the pH dependence of the binding and electrostatic forces as the main mechanism.

Drug release from nanoparticles embedded in four different nanofibrillar cellulose aerogels

Highly porous nanocellulose aerogels prepared by freeze-drying from various nanofibrillar cellulose (NFC) hydrogels are introduced as nanoparticle reservoirs for oral drug delivery systems. Here we show that beclomethasone dipropionate (BDP) nanoparticles coated with amphiphilic hydrophobin proteins can be well integrated into the NFC aerogels. NFCs from four different origins are introduced and compared to microcrystalline cellulose (MCC). The nanocellulose aerogel scaffolds made from red pepper (RC) and MCC release the drug immediately, while bacterial cellulose (BC), quince seed (QC) and TEMPO-oxidized birch cellulose-based (TC) aerogels show sustained drug release. Since the release of the drug is controlled by the structure and interactions between the nanoparticles and the cellulose matrix, modulation of the matrix formers enable a control of the drug release rate. These nanocomposite structures can be very useful in many pharmaceutical nanoparticle applications and open up new possibilities as carriers for controlled drug delivery.

The structure and mechanics of nanofibrillar cellulose foams

Crystalline nanofibrillar cellulose has remarkable mechanical properties: a Young's modulus of about 130 GPa and a tensile strength in the range of 750–1000 MPa. Recently, there has been increasing interest in exploiting these exceptional properties in engineering composites and foams. Here, we compare measurements of the mechanical properties of nanofibrillar cellulose composites and foams with their potential properties based on models for composites and foams. We find that current NFC foams do not yet reach their potential and suggest modifications to their microstructure for improved mechanical performance.

Copper–copper oxide coated nanofibrillar cellulose: a promising biomaterial

Nanocellulose is gaining impetus as a hierarchical material in many advanced applications. The isolation of nanocellulose from easily available bio-resources is an area to be delved into thoroughly. This article highlights the isolation of nanofibrillar cellulose from an abundant natural source, Colocasia esculenta, by a chemical method. The nanofibrils were coated with copper–copper oxide nanoparticles through a ‘green’ reductive technique using the alcoholic extract of Terminalia chebula fruit. The prepared fibrils and the nanohybrid were characterized by Fourier transformed infrared spectroscopy, X-ray diffraction and transmission electron microscopic studies. The coated nanofibrils showed promising antimicrobial activity against Staphyllococcus aureus, Escherichia coli and Candida albicans. The nanohybrid was quite compatible with peripheral blood mononuclear cells (PBMC) as well as mammalian red blood cells (RBCs). The structural integrity of bovine serum albumin (BSA) was unaltered upon interaction with the nanohybrid. The biocompatible and antimicrobial nanohybrid presented here possesses high potential to be used as a biomaterial in a suitable niche of modern biomedical fields.

Specific water uptake of thin films from nanofibrillar cellulose

Swelling of NFC films was surveyed by quartz crystal microbalance with dissipation monitoring coupled with H2O/D2O exchange and surface plasmon resonance. The influence of charged groups on swelling was investigated by neutralizing the charge of NFC with cationic polyelectrolytes or increasing the charge with carboxymethyl cellulose (CMC). The solid content of the porous NFC film was <50%. In the swollen state, a film contained only ∼15–30% cellulose. Adsorption of cationic polyelectrolytes decreased the ability of the film to bind water by a maximum of 20% indicating that the contribution of charge to the swelling of NFC is moderate. Annealing of the film also caused a 20% reduction in its water uptake. Yet annealing after adsorption of cationic polyelectrolytes decreased the water-binding ability of the film by ∼50%. Charge increase by CMC adsorption caused additional swelling of the NFC film while subsequent charge neutralization by cationic polyelectrolytes reduced the water content below the control reference.