Sulfated Cellulose Nanocrystals Research Articles

Properties of APTES-Modified CNC Films.

Sulfated cellulose nanocrystals' (CNCs') facile aqueous dispersibility enables producing films, fibers, and other materials using only water as a solvent but prevents using sulfated CNCs in applications that require water immersion. We report that modifying CNCs with 3-aminopropyl-triethoxysilane (APTES) via a simple, single-pot reaction scheme dramatically improves the hydrolytic stability of CNC films. The effects of APTES modification on CNCs' properties were studied using attenuated total reflectance Fourier transform infrared spectroscopy, atomic force and optical microscopy, thermogravimetric analysis, dynamic light scattering, and ultimate analysis. Substituting a mere 12.6% of the CNCs' available hydroxyl groups with APTES dramatically increased the hydrolytic stability of shear cast films while only having minor impacts on their mechanical properties. In addition, quartz crystal microbalance with dissipation monitoring (QCMD) and multiparametric surface plasmon resonance (MP-SPR) studies showed that the CNC-APTES films also had a greater irreversible binding with carbofuran, a pesticide and emerging contaminant. These results highlight that APTES modification is a promising method for increasing the utility of sulfated CNCs in sensors, adsorbents, and other applications requiring water immersion.

Cellulose nanocrystal stabilized pickering nanoemulsions and their coalescence stability studied by fluorescence microscopy

Cellulose nanocrystals (CNCs) have been used as Pickering emulsifiers by forming rigid interfacial layer coated around oil droplets. Sulfated and desulfated CNCs were used to emulsify squalane oil to produce Pickering nanoemulsions. The formation of CNCs-Pickering nanoemulsions was investigated and their stability against mechanical stresses was studied using fluorescence microscopy with a lab-made image analysis program. The formation of Pickering nanoemulsions using CNC particles was tuned by screening their surface charges with cations. Sulfated and desulfated CNC nanoemulsions showed submicron droplet size of 619 and 555 nm, respectively. The mechanical stresses could induce droplet encounter leading to physical instability. The sulfated CNCs displayed superior stability than the desulfated CNCs in terms of droplet aggregation after treatment with mechanical stresses. Fluorescence microscopy image analysis revealed the physical instability of Pickering nanoemulsions at the microscopic level, which is a useful tool for studying the destabilization mechanisms.

Carboxylation of sulfated cellulose nanocrystals by family AA9 lytic polysaccharide monooxygenases

Lytic polysaccharide monooxygenases (LPMOs) from the auxiliary activity 9 (AA9) family act on cellulose through an oxidative mechanism that improves cellulose saccharification in concert with other cellulolytic enzymes. Degradation and solubilization of cellulose chains are known to take place when various cellulose hierarchies, fibers, nanofibers, and cellulose nanocrystals (CNCs) are subjected to LPMOs, either alone or in combination with other cellulose acting enzymes. The use of LPMOs to modify and prepare CNCs has been proposed mostly in top-down synthesis from larger hierarchies. Here, we attempted a direct surface modification of CNCs with LPMOs with the aim of investigating the role played by the charged sulfate groups on CNCs. Sulfate half-ester groups are introduced during the preparation of CNCs from cellulose using sulfuric acid. It has been proposed that the charged sulfate groups hinder the binding of enzymes or affinity of charged reactants on the surface and hence reduce enzymatic and chemical reaction efficiency. We demonstrate the modification of commercial sulfated CNCs using a family AA9 LPMO. Conductometric titration and spectrometric characterization of the oxidized particles indicate that carboxylation of up to 10% was possible without degradation of the crystals. Unexpectedly, the carboxyl groups could only be introduced to the crystals containing sulfate groups, while desulfated crystals remained unfunctionalized. This was deemed to be due to that the sulfate groups limit the adsorption of the enzymes and hence modulate the cuts facilitated by the enzymes on the surface. This limits the release of chains from the surface and enables the carboxylation of the insoluble substrate rather than the release of the solubilized chains. This study highlights the importance of analyzing both the solid and soluble reaction products to gain insights into the oxidation mechanism. We demonstrated that 10% functionalization suffices for the use of CNCs in coupling chemistry.

Colloidal Stability Window for Carboxylated Cellulose Nanocrystals: Considerations for Handling, Characterization, and Formulation.

The scale of production of cellulose nanocrystals (CNCs) has increased dramatically to meet the growing demand for sustainably sourced materials. This work defines the colloidal stability window for commercially produced carboxylated CNCs (DextraCel) compared to the more traditional sulfated CNCs. Phase diagrams showing the stable, reversibly agglomerated, irreversibly aggregated/sedimented, and colloidal glass "zones" as a function of suspension pH, ionic strength, CNC surface charge content, counterion, and concentration are presented. The pKa of carboxylated CNCs was measured to be 5.1, and suspensions of carboxylated CNCs (0.5-1.5 wt %) were visually stable from pH 3 to 11 (without salt). Carboxylated CNCs were highly sensitive to ionic strength, demonstrating some agglomeration with as little as 5 mM NaCl, supporting that weak acid surface groups and lower charge contents make CNCs more sensitive to solution conditions. Surface charge content had the greatest influence on colloidal stability followed by the counterion; carboxylated CNCs were more stable in the "as-received" sodium form, whereas sulfated CNCs had improved stability in acid form after ion exchange. The stability of carboxylated CNCs with industrially relevant additives (ionic and nonionic surfactants and initiators) was also investigated. Less concentrated suspensions were more colloidally stable, emphasizing that characterization and processing of CNCs favor dilute conditions. If carboxylated CNCs are subjected to conditions outside of their colloidal stability window, simple dilution or pH adjustment does not return them to colloidally stable discrete nanoparticles; however, ultrasonication can redisperse agglomerates. This study offers guidelines for handling carboxylated CNCs to broaden the range of products that can be improved by their incorporation.

Protein Adsorption and Its Effects on Electroanalytical Performance of Nanocellulose/Carbon Nanotube Composite Electrodes.

Protein fouling is a critical issue in the development of electrochemical sensors for medical applications, as it can significantly impact their sensitivity, stability, and reliability. Modifying planar electrodes with conductive nanomaterials that possess a high surface area, such as carbon nanotubes (CNTs), has been shown to significantly improve fouling resistance and sensitivity. However, the inherent hydrophobicity of CNTs and their poor dispersibility in solvents pose challenges in optimizing such electrode architectures for maximum sensitivity. Fortunately, nanocellulosic materials offer an efficient and sustainable approach to achieving effective functional and hybrid nanoscale architectures by enabling stable aqueous dispersions of carbon nanomaterials. Additionally, the inherent hygroscopicity and fouling-resistant nature of nanocellulosic materials can provide superior functionalities in such composites. In this study, we evaluate the fouling behavior of two nanocellulose (NC)/multiwalled carbon nanotube (MWCNT) composite electrode systems: one using sulfated cellulose nanofibers and another using sulfated cellulose nanocrystals. We compare these composites to commercial MWCNT electrodes without nanocellulose and analyze their behavior in physiologically relevant fouling environments of varying complexity using common outer- and inner-sphere redox probes. Additionally, we use quartz crystal microgravimetry with dissipation monitoring (QCM-D) to investigate the behavior of amorphous carbon surfaces and nanocellulosic materials in fouling environments. Our results demonstrate that the NC/MWCNT composite electrodes provide significant advantages for measurement reliability, sensitivity, and selectivity over only MWCNT-based electrodes, even in complex physiological monitoring environments such as human plasma.

Dispersion of Sonicated Sulfated Cellulose Nanocrystals and Their Effect on the Mechanical Properties of Cement Mortars

Dispersion of Sonicated Sulfated Cellulose Nanocrystals and Their Effect on the Mechanical Properties of Cement Mortars

Large-Scale Preparation of Carboxylated Cellulose Nanocrystals and Their Application for Stabilizing Pickering Emulsions.

Cellulose nanocrystals (CNCs) with varied unique properties have been widely used in emulsions, nanocomposites, and membranes. However, conventional CNCs for industrial use were usually prepared through acid hydrolysis or heat-controlled methods with sulfuric acid. This most commonly used acid method generally suffers from low yields, poor thermal stability, and potential environmental pollution. Herein, we developed a high-efficiency and large-scale preparation strategy to produce carboxylated cellulose nanocrystals (Car-CNCs) via carboxymethylation-enhanced ammonium persulfate (APS) oxidation. After carboxymethylation, the wood fibers could form unique "balloon-like" structures with abundant exposed hydroxy groups, which facilitated exfoliating fibril bundles into individual nanocrystals during the APS oxidation process. The production process under controlled temperature, time period, and APS concentrations was optimized and the resultant Car-CNCs exhibited a typical structure with narrow diameter distributions. In particular, the final Car-CNCs exhibited excellent thermal stability (≈346.6 °C) and reached a maximum yield of 60.6%, superior to that of sulfated cellulose nanocrystals (Sul-CNCs) prepared by conventional acid hydrolysis. More importantly, compared to the common APS oxidation, our two-step collaborative process shortened the oxidation time from more than 16 h to only 30 min. Therefore, our high-efficiency method may pave the way for the up-scaled production of carboxylated nanocrystals. More importantly, Car-CNCs show potential for stabilizing Pickering emulsions that can withstand changeable environments, including heating, storage, and centrifugation, which is better than the conventional Sul-CNC-based emulsions.

Antibody Immobilization on Sulfated Cellulose Nanocrystals.

Exploiting cellulose nanocrystals' high aspect ratio and tailorable surface for immunological biosensors has been hindered by the relatively limited research on using commonly available sulfated cellulose nanocrystals (CNCs) for antibody immobilization and by the low hydrolytic stability of dried assemblies produced from sulfated CNCs. Herein, we report a reaction scheme that enables both hydrolytic stability and antibody immobilization through 3-aminopropyl-triethoxysilane and glutaric anhydride chemistry. Immobilization was demonstrated using three model antibodies used in the detection of the cancer biomarkers: alpha-fetoprotein, prostate-specific antigen, and carcinoembryonic antigen. Thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy provided evidence of CNC modification. Quartz crystal microbalance with dissipation monitoring was used to monitor binding during each step of the immobilization scheme as well as binding of the corresponding antigens. The general reaction scheme was tested using both aqueous CNC dispersions and CNC films. Film modification is slightly simpler as it avoids centrifugation and washing steps. However, modifying the dispersed CNCs provides access to their entire surface area and results in a greater capacity for antigen binding.

Preparation, properties, and mechanism of anionic and cationic cellulose nanocrystals/waterborne polyurethane composite films

Three kinds of cellulose nanocrystals (CNCs) were added into waterborne polyurethane (WPU) and nanocomposite films that were prepared by solution casting. The influence of different ionic function groups on microstructure and properties of composite films was investigated. Compared with sulfated CNCs (SCNCs) and TEMPO oxidized CNCs (TOCNCs), FE-SEM images showed that cationized CNCs (CaCNCs) had better dispersion in composite films. The thermal decomposition of these composite films was delayed by 15 °C compared with pure WPU film. The tensile strength and fracture work of CaCNC/WPU composite film increased by 11.9% and 8.4%, respectively. The light transmittance of CaCNC/WPU composite film was highest among the 3 composite films, but its oxygen permeability was the lowest. In sum, the composite film with CaCNCs had optimal strength, toughness, light transmittance, and oxygen barrier properties, which is consistent with good compatibility of the two components and densest structure observed in SEM. There may be an ionic attraction and hydrogen bonds of CaCNCs and WPU in the composite film. The composite films are expected to have applications in food packaging, furniture coatings, and biomedical fields.

Green synthesis of cellulose nanocrystal/ZnO bio-nanocomposites exerting antibacterial activity and downregulating virulence toxigenic genes of food-poisoning bacteria

Recently, cellulose nanocrystals (CNs) have attracted wide attention owing to their superior properties compared to their bulk materials. For example, they represent an outstanding model for fabricating green metallic/metal oxide nanoparticles (NPs). In this study, two CNs (carboxylated CNs and sulfated CNs) extracted from agro-wastes of palm sheath fibers were used as templates for the facile and green synthesis of ZnO NPs by employing the sono-co-precipitation method. The obtained nanomaterials were characterized using TEM, EDX, UV–visible, DLS, FT-IR, and XRD analysis. As a result, the size and concentration of synthesized ZnO NPs were inversely proportional to one another and were affected by the CNs utilized and the reaction temperature used. Contagious diseases incited by multifarious toxigenic bacteria present severe threats to human health. The fabricated bio-nanocomposites were evaluated in terms of their antimicrobial efficacy by agar well diffusion method and broth microdilution assay, showing that CN–ZnO bio-nanocomposites were effective against the tested Gram-negative (Escherichia coli and Salmonella) and Gram-positive (Listeria monocytogenes and Staphylococcus aureus) bacteria. The influence of the subinhibitory concentrations of these suspensions on the expression of the most critical virulence toxin genes of the tested strains was effective. Significant downregulation levels were observed through toxigenic operons to both fabricated CN–ZnO bio-nanocomposites with a fold change ranging from 0.004 to 0.510, revealing a decline in the capacity and virulence of microorganisms to pose infections. Therefore, these newly fabricated CNS–ZnO bio-nanocomposites could be employed rationally in food systems as a novel preservative to inhibit microbial growth and repress the synthesis of exotoxins.

Role of nanocellulose in tailoring electroanalytical performance of hybrid nanocellulose/multiwalled carbon nanotube electrodes

Nanocellulose has emerged as a promising green dispersant for carbon nanotubes (CNTs), and there is an increasing trend in developing nanocellulose/CNT hybrid materials for electrochemical detection of various small molecules. However, there have been very few comprehensive studies investigating the role of nanocellulosic material properties upon the electroanalytical performance of the resultant hybrid electrodes. In this work, we demonstrate the influence of both nanocellulose functionalization and geometry, utilizing sulfated cellulose nanocrystals, sulfated cellulose nanofibers, and TEMPO-oxidized cellulose nanofibers. Transmission electron microscopy tomography enables direct visualization of the effect of nanocellulosic materials on the hybrid architectures. High resolution X-ray absorption spectroscopy verifies that the chemical nature of CNTs in the different hybrids is unmodified. Electroanalytical performances of the different nanocellulose/CNT hybrid electrodes are critically evaluated using physiologically relevant biomolecules with different charge such as, dopamine (cationic), paracetamol (neutral), and uric acid (anionic). The hybrid electrode containing fibrillar nanocellulose geometry with a high degree of sulfate group functionalization provides the highest electroanalytical sensitivity and strongest enrichment towards all studied analytes. These results clearly demonstrate for the first time, the extent of tailorability upon the electroanalytical response of nanocellulose/CNT hybrid electrodes towards different biomolecules, offered simply by the choice of nanocellulosic materials.

Dynamic and Static Assembly of Sulfated Cellulose Nanocrystals with Alkali Metal Counter Cations.

Sulfate groups on cellulose particles such as cellulose nanocrystals (CNCs) provide colloidal stability credit to electrostatic repulsion between the like-charged particles. The introduction of sodium counter cations on the sulfate groups enables drying of the CNC suspensions without irreversible aggregation. Less is known about the effect of other counter cations than sodium on extending the properties of the CNC particles. Here, we introduce the alkali metal counter cations, Li+, Na+, K+, Rb+, and Cs+, on sulfated CNCs without an ion exchange resin, which, so far, has been a common practice. We demonstrate that the facile ion exchange is an efficient method to exchange to any alkali metal cation of sulfate half esters, with exchange rates between 76 and 89%. The ability to form liquid crystalline order in rest was observed by the presence of birefringence patterns and followed the Hofmeister series prediction of a decreasing ability to form anisotropy with an increasing element number. However, we observed the K-CNC rheology and birefringence as a stand-out case within the series of alkali metal modifications, with dynamic moduli and loss tangent indicating a network disruptive effect compared to the other counter cations, whereas observation of the development of birefringence patterns in flow showed the absence of self- or dynamically-assembled liquid crystalline order.

The Effect of Electrolytes and Urea on the Ethyl Lauroyl Arginate and Cellulose Nanocrystals Foam Stability

Carboxylated cellulose nanocrystals (cCNC) are highly dispersible particles useful in many industries. In particular, they can be applied to form Pickering emulsions and foams for “green” applications in the cosmetics, pharmaceutical industry or food processing. We demonstrated that carboxylated cellulose nanocrystals enhance foamability and foam stability when mixed with cationic surfactant ethyl lauroyl arginate (LAE), having superior properties over sulfated cellulose nanocrystals (sCNC) concerning surfactant concentration range and foam volume. Mixtures of LAE and cCNC were characterized for their hydrodynamic diameter, zeta potential, surface tension and surface rheological properties. The influence of electrolytes, namely, sodium chloride, guanidine hydrochloride and sodium salicylate, and the addition of concentrated urea to LAE-cCNC mixtures on foamability and foam stability were investigated. Electrolytes in the concentration of 5 mM showed a moderate effect on foam stability. In contrast, spectacular foam collapse was detected after adding concentrated urea. The preliminary rheological data from the pendant drop oscillations revealed low elastic modulus upon urea addition and the loss modulus that increased with the frequency, which suggested a viscous interfacial layer.

Construction of a novel electrochemical sensor based on biomass material nanocellulose and its detection of acetaminophen

In this work, acidic sulfated cellulose nanocrystals (CNCs) were used as green carriers, and a novel composite material was synthesized and used to design sensors for paracetamol (AP) detection. There are negatively charged acidic sulfate groups on the surface of CNCs, which can enhance the electrostatic repulsion between nanoparticles, thereby increasing the stability and dispersibility of AgNPs in the system, making them less prone to agglomeration. Cationic pillar[5]arene (CP5) with a strong host-guest effect was used as a stable ligand for silver nanoparticles (AgNPs). AgNPs have good electrical conductivity and large specific surface area, which can significantly increase the peak current. In addition, CP5 has excellent supramolecular recognition performance, which can specifically recognize the guest molecule AP to form an inclusion complex, so that a large number of AP molecules are attached to the electrode surface, which is beneficial to the amplification of electrochemical signals. The prepared sensor is more attractive in terms of sensitivity and recognition performance; the host-guest binding constant was (3.37 ± 0.26) × 104 M-1, which can be obtained with good linearity (R 2 = 0.996), low detection limit (90 nM, LOD = 3σ/k, S/N = 3) and a wide linear range (0.5-500 μM). The electrochemical sensor showed good performance in quantitative analysis, stability, selectivity, reproducibility, and actual sample detection, providing high feasibility for real-time monitoring of paracetamol; it also provides a new idea for a green sensor.

Effect of ultrasonication on the size distribution and stability of cellulose nanocrystals in suspension: an asymmetrical flow field-flow fractionation study

Cellulose nanocrystals (CNCs) are bio-based building blocks for sustainable advanced materials with prospective applications in polymer composites, emulsions, electronics, sensors, and biomedical devices. However, their high surface area-to-volume ratio promotes agglomeration, which restrains their performance in size-driven applications, thereby hindering commercial CNC utilization. In this regard, ultrasonication is commonly applied to disperse CNCs in colloidal suspensions; however, ultrasonication methodology is not yet standardized and knowledge of the effects of ultrasound treatments on CNC size distribution is scarce. The major goals of this study were attributed to targeted breakage of CNC agglomerates and clusters by ultrasound. The evolution of particle size distribution and potential de-sulfation by ultrasonication as well as the long-term stability of ultrasonicated CNC suspensions were investigated. Colloidal suspensions of sulfated CNCs were isolated from cotton α-cellulose. Effects of ultrasonication on particle size distribution were determined by asymmetrical flow field-flow fractionation (AF4) coupled with on-line multi-angle light scattering and ultraviolet spectroscopy. These results were complemented with off-line dynamic light scattering. High ultrasound energy densities facilitated cumulative dispersion of CNC clusters. Consequently, the mean rod length decreased logarithmically from 178.1 nm at an ultrasound energy input of 2 kJ g−1 CNC to 141.7 nm (− 20%) at 40 kJ g−1 CNC. Likewise, the hydrodynamic diameter of the particle collective decreased logarithmically from 94.5 to 73.5 nm (− 22%) in the same processing window. While the rod length, below which 95 wt% of the CNCs were found, decreased from 306.5 to 231.8 nm (− 24%) from 2 to 40 kJ g−1 CNC, the shape factor of the main particle fraction ranged from 1.0 to 1.1, which indicated a decreasing number of dimers and clusters in the particle collective. In summary, progressing ultrasonication caused a shift of the particle length distribution to shorter particle lengths and simultaneously induced narrowing of the distribution. The suspension’s electrical conductivity concurrently increased, which has been attributed to faster diffusion of smaller particles and exposure of previously obscured surface charges. Colloidal stability, investigated through electrical AF4 and electrophoretic light scattering, was not affected by ultrasonication and, therefore, indicates no de-sulfation by the applied ultrasound treatment. Occurrence of minor CNC agglomeration at low ultrasound energy densities over the course of 6 months suggest the effect was not unmitigatedly permanent.

Benchmarking Cellulose Nanocrystals Part II: New Industrially Produced Materials.

The demand for industrially produced cellulose nanocrystals (CNCs) has been growing since 2012, when CelluForce Inc. opened its inaugural demonstration plant with a production capacity of 1 tonne per day. Currently, there are 10 industrial CNC producers worldwide, each producing a unique material. Thus, academic researchers and commercial users alike must consider the properties of all available CNCs and carefully select the material which will optimize the performance of their desired application. To support these efforts, this article presents a thorough characterization of four new industrially produced CNCs including sulfated CNCs from NORAM Engineering and Constructors Ltd. (in cooperation with InnoTech Alberta and Alberta-Pacific Forest Industries Inc.) and Melodea Ltd., as well as carboxylated CNCs from Anomera Inc. and Blue Goose Biorefineries Inc. These materials were benchmarked against typical lab-made, sulfated CNCs. While all CNCs were similar in size, shape, crystallinity, and suspension quality, the sulfated CNCs had a higher surface charge density than their carboxylated counterparts, leading to higher colloidal stability. Additionally, significant differences in the rheological profiles of aqueous CNC suspensions, as well as CNC thermal stability and self-assembly behavior, were observed. As such, this article highlights both the subtle and significant differences between five CNC types and acts as a guide for end-users looking to optimize the performance of CNC-based materials.

Preparation and Surface Functionalization of Carboxylated Cellulose Nanocrystals.

In recent years, cellulose nanocrystals (CNCs) have emerged as a leading biomass-based nanomaterial owing to their unique functional properties and sustainable resourcing. Sulfated cellulose nanocrystals (sCNCs), produced by sulfuric acid-assisted hydrolysis of cellulose, is currently the predominant form of this class of nanomaterial; its utilization leads the way in terms of CNC commercialization activities and industrial applications. The functional properties, including high crystallinity, colloidal stability, and uniform nanoscale dimensions, can also be attained through carboxylated cellulose nanocrystals (cCNCs). Herein, we review recent progress in methods and feedstock materials for producing cCNCs, describe their functional properties, and discuss the initial successes in their applications. Comparisons are made to sCNCs to highlight some of the inherent advantages that cCNCs may possess in similar applications.

Nanocellulose/Fullerene Hybrid Films Assembled at the Air/Water Interface as Promising Functional Materials for Photo-electrocatalysis.

Cellulose nanomaterials have been widely investigated in the last decade, unveiling attractive properties for emerging applications. The ability of sulfated cellulose nanocrystals (CNCs) to guide the supramolecular organization of amphiphilic fullerene derivatives at the air/water interface has been recently highlighted. Here, we further investigated the assembly of Langmuir hybrid films that are based on the electrostatic interaction between cationic fulleropyrrolidines deposited at the air/water interface and anionic CNCs dispersed in the subphase, assessing the influence of additional negatively charged species that are dissolved in the water phase. By means of isotherm acquisition and spectroscopic measurements, we demonstrated that a tetra-sulfonated porphyrin, which was introduced in the subphase as anionic competitor, strongly inhibited the binding of CNCs to the floating fullerene layer. Nevertheless, despite the strong inhibition by anionic molecules, the mutual interaction between fulleropyrrolidines at the interface and the CNCs led to the assembly of robust hybrid films, which could be efficiently transferred onto solid substrates. Interestingly, ITO-electrodes that were modified with five-layer hybrid films exhibited enhanced electrical capacitance and produced anodic photocurrents at 0.4 V vs Ag/AgCl, whose intensity (230 nA/cm2) proved to be four times higher than the one that was observed with the sole fullerene derivative (60 nA/cm2).

Physical, chemical, and toxicological characterization of sulfated cellulose nanocrystals for food-related applications using in vivo and in vitro strategies.

Cellulose nanocrystals (CNCs) are a next-generation cellulose product with many unique properties including applications in the food industry as a food additive, food coating, and in food-contact packaging material. While CNC is anticipated to be safe due to its similarity to the many forms of cellulose currently used as food additives, special consideration is given to it as it is the first manufactured form of cellulose that is nanoscale in both length and width. A proactive approach to safety has been adopted by manufacturers to demonstrate CNC safety toward responsible commercialization. As part of the safety demonstration, in vivo and in vitro testing strategies were commissioned side-by-side with conventional cellulose, which has been safely used in food for decades. Testing included a 90-day rodent feeding study as well as additional physical, chemical, and biological studies in vitro that follow European Food Safety Authority (EFSA) guidance to demonstrate the safe use of novel food ingredients. The strategy includes assessment of neat materials side-by-side with simulated digestion, mimicking conditions that occur along the gastrointestinal tract as well as intracellularly. An intestinal co-culture model examined any potential toxicological effects from exposure to either pristine or digested forms of CNC including cytotoxicity, metabolic activity, membrane permeability, oxidative stress, and proinflammatory responses. None of the studies demonstrated any toxicity via oral or simulated oral exposure. These studies demonstrate that CNC produced by InnoTech Alberta is similarly safe by ingestion as conventional cellulose with a no-observed-adverse-effect level of 2085.3 (males) and 2682.8 (females) mg/kg/day.

Agglomeration of cellulose nanocrystals: the effect of secondary sulfates and their use in product separation

This study was aimed at the development of a better understanding of the agglomeration behavior of sulfated cellulose nanocrystals (CNCs) in the presence of sulfates with monovalent (NH4+, K+, Na+) and divalent (Ca2+) cations, and to demonstrate their potential in simple and efficient product separation. Protonated CNCs were counterion-exchanged and their ionic strength was increased by adding sulfates of the respective cation to trigger agglomeration. The critical concentrations of agglomeration (CAC) and peptization (CPC) were determined. We found that the agglomeration behavior of CNCs could be attributed to matching affinities between the cations and the sulfate half-ester groups on the CNC surfaces. Based on these findings, a facile and efficient downstream process was designed to separate CNCs from neutralized reactant solutions using CAC and CPC. This method provides colloidally stable CNCs at high yield provided by centrifugation. When salt concentrations in the product are maintained below the CAC, as prepared CNCs from neutralized reactant solutions might be used in hydrogels and emulsions.