1H and 13C chemical shift assignment of the monomers that comprise carboxymethyl cellulose

Super foldable transparent paper by regulating the multi-scale structure of cellulose fibers

Transparent cellulose papers have emerged as a promising substrate and/or functional component for next-generation sustainable flexible electronics. However, obtaining transparent paper with folding endurance comparable to that of plastic films such as polyethylene terephthalate (PET) remains a major challenge, which was addressed in this study by modulating the multiscale structure (from molecular structure, aggregation structure to fibrous morphology) of wood fibers. Compared to the natural wood fibers, the modified fibers not only retained their length and cellulose degree of polymerization (DP) to a large extent, but also had lower crystallinity and improved swelling capability, which well preserved the fiber strength and dense intertwined fiber network, and led to stronger inter-fiber interactions in the final transparent paper. The obtained paper (CM-paper) exhibits an optical transparency of 91 % and a folding endurance of 37,466 times, comparable to that of commercial PET (39,955 folds). Furthermore, the underlying mechanism for the superior foldability of the transparent paper was unveiled at three scales is explored. Finally, the potential application of CM-paper in electromagnetic induction electrodes was demonstrated, where the CM-paper electrodes exhibit satisfactory conductivity after repeated rubbing. This work offers an innovative approach to produce transparent papers with outstanding foldability, which is expected to plastic replacement.

Carboxymethylcellulose production from sugarcane bagasse: A new approach in biorefinery concept

Although the production of carboxymethylcellulose from different raw materials is commercial, its preparation from agro-industrial residues has still been poorly explored in terms of performance, cost-effectiveness, and sustainability. Here, sugarcane bagasse was used as raw material for the carboxymethylcellulose (CMCb) synthesis within the biorefinery context. Sequential treatments were used for the removal of hemicellulose and lignin and the isolation of cellulose, whose conversion into CMCb was carried out through treatments with NaOH and monochloroacetic acid (MCA). The chemical modifications led to a CMCb with a substitution degree of 0.44, purity of 71.3 %, and 32 % crystallinity. Our residue-based CMCb was adequate for microorganism encapsulation, a high-value application, promoting viable conidia after 5 months of storage in equivalent conditions of high-purity, commercial CMC. Our findings show a route for the preparation of valuable polysaccharides from waste in future biorefineries, which, depending on their characteristics, can be applied in different processes. Here we use them for the encapsulation of a bioagent, although they can easily be used in other applications such as packaging and coating.

NIR-responsive carboxymethyl-cellulose hydrogels containing thioketal-linkages for on-demand drug delivery system

Near-infrared (NIR) light-responsive hydrogels have emerged as a highly promising strategy for effective anticancer therapy owing to the remotely controlled release of chemotherapeutic molecules with minimal invasive manner. In this study, novel NIR-responsive hydrogels were developed from reactive oxygen species (ROS)-cleavable thioketal cross-linkers which possessed terminal tetrazine groups to undergo a bio-orthogonal inverse electron demand Diels Alder click reaction with norbornene modified carboxymethyl cellulose. The hydrogels were rapidly formed under physiological conditions and generated N2 gas as a by-product, which led to the formation of porous structures within the hydrogel networks. A NIR dye, indocyanine green (ICG) and chemotherapeutic doxorubicin (DOX) were co-encapsulated in the porous network of the hydrogels. Upon NIR-irradiation, the hydrogels showed spatiotemporal release of encapsulated DOX (>96 %) owing to the cleavage of thioketal bonds by interacting with ROS generated from ICG, whereas minimal release of encapsulated DOX (<25 %) was observed in the absence of NIR-light. The in vitro cytotoxicity results revealed that the hydrogels were highly cytocompatible and did not induce any toxic effect on the HEK-293 cells. In contrast, the DOX + ICG-encapsulated hydrogels enhanced the chemotherapeutic effect and effectively inhibited the proliferation of Hela cancer cells when irradiated with NIR-light.

Self-Assembled Chitosan/Dialdehyde Carboxymethyl Cellulose Hydrogels: Preparation and Application in the Removal of Complex Fungicide Formulations from Aqueous Media

Environmental contamination with pesticides occurs at a global scale as a result of prolonged usage and, therefore, their removal by low-cost and environmentally friendly systems is actively demanded. In this context, our study was directed to investigate the feasibility of using some self-assembled hydrogels, comprising chitosan (CS) and carboxymethylcellulose (CMC) or dialdehyde (DA)-CMC, for the removal of four complex fungicide formulations, namely Melody Compact (MC), Dithane (Dt), Curzate Manox (CM), and Cabrio®Top (CT). Porous CS/CMC and CS/DA-CMC hydrogels were prepared as discs by combining the semi-dissolution acidification sol-gel transition method with a freeze-drying approach. The obtained CS/CMC and CS/DA-CMC hydrogels were characterized by gel fraction yield, FTIR, SEM, swelling kinetics, and uniaxial compression tests. The batch-sorption studies indicated that the fungicides' removal efficiency (RE%) by the CS/CMC hydrogels was increased significantly with increasing sorbent doses reaching 94%, 93%, 66% and 48% for MC, Dt, CM and CT, respectively, at 0.2 g sorbent dose. The RE values were higher for the hydrogels prepared using DA-CMC than for those prepared using non-oxidized CMC when initial fungicide concentrations of 300 mg/L or 400 mg/L were used. Our results indicated that CS/DA-CMC hydrogels could be promising biosorbents for mitigating pesticide contamination of aqueous environments.

A high-efficient nano pesticide-fertilizer combination fabricated by amino acid-modified cellulose based carriers

BACKGROUND

As the global population grows, large quantities of agrochemicals are used to secure food demand and there is an urgent need to develop efficient and environmentally friendly pesticides and fertilizers. Compared with traditional pesticides, nanopesticide formulations can achieve better foliar wettability, chemical stability, and water dispersibility without or with the minimal use of organic solvents, in line with the development of sustainable agriculture.

RESULTS

In this research, glycidyl methacrylate (GMA) was used as an intermediate and glycine methyl ester (GLY) was used as an organic nitrogen source to modify carboxymethyl cellulose (CMC) to synthesize a pesticide nanocarrier CMC-PGMA-GLY. A nanopesticide EB@CMC-PGMA-GLY (EB@CPG) was formed by the hydrophobic and electrostatic interactions of emamectin benzoate (EB), which had good water dispersion. The good affinity of the composite towards leaves led to the effective moistening of the leaf surface by the pesticide and through the pH control pesticide release. Biological experiments show that nanopesticides can maintain high insecticidal activity and have no toxicity to seed germination. The results of pot experiment showed that the nanocarriers could be used as an organic nitrogen fertilizer to increase the fresh weight of plants by 39.77%.

CONCLUSIONS

This environmentally friendly pesticide carrier can be used as a fertilizer to provide sufficient nutrients for crops, opening a new method for the development of sustainable agriculture. © 2021 Society of Chemical Industry.

Facile Post-Carboxymethylation of Cellulose Nanofiber Surfaces for Enhanced Water Dispersibility

To improve the water dispersibility of cellulose nanofibers without deteriorating the physical properties, it is necessary to develop methods that can selectively modify fiber surfaces. Herein, the reaction conditions for carboxymethylation of the surface of nanofibrillated bacterial cellulose were optimized using chloroacetic acid as an etherification agent. Carboxymethylation in a high-concentration alkaline solution (>5 wt %) in the presence of isopropanol caused the mercerization and carboxymethylation of not only the nanofiber surface but also the cellulose crystals within the nanofiber, resulting in nanofiber swelling and an increase in fiber width. In contrast, with a dilute alkaline aqueous solution (3 wt %), the nanofiber surface was successfully carboxymethylated without changing the inner structure. Furthermore, the morphology was not affected by the carboxymethylation reaction, and no fiber swelling occurred under these reaction conditions. When the substitution reaction proceeded only on the nanofiber surface, the maximum degree of substitution (i.e., the average number of carboxymethyl groups substituted per anhydroglucose residue in cellulose) was 0.091. After surface modification, the nanofibers became more negatively charged, which improved the dispersibility in water through electrostatic repulsion, resulting in a drastic increase in the transparency of the nanofiber dispersion. This method provides a general approach for the surface modification of cellulose nanofibers to increase water dispersibility.

Water-based carbodiimide mediated synthesis of polysaccharide-amino acid conjugates: Deprotection, charge and structural analysis

We report here a one-step aqueous method for the synthesis of isolated and purified polysaccharide-amino acid conjugates. Two different types of amino acid esters: glycine methyl ester and L-tryptophan methyl ester, as model compounds for peptides, were conjugated to the polysaccharide carboxymethylcellulose (CMC) in water using carbodiimide at ambient conditions. Detailed and systematic pH-dependent charge titration and spectroscopy (infrared, nuclear magnetic resonance: ¹H, ¹³C- DEPT 135, ¹H- ¹³C HMBC/HSQC correlation), UV-vis, elemental and ninhydrin analysis provided solid and direct evidence for the successful conjugation of the amino acid esters to the CMC backbone via an amide bond. As the concentration of amino acid esters increased, a conjugation efficiency of 20-80% was achieved. Activated charcoal aided base-catalyzed deprotection of the methyl esters improved the solubility of the conjugates in water. The approach proposed in this work should have the potential to tailor the backbone of polysaccharides containing di- or tri-peptides.

Interaction of hairy carboxyalkyl cellulose nanocrystals with cationic surfactant: Effect of carbon spacer

Tuning the surface chemistry of nanocellulose is essential for developing its end-use applications. Herein, different carboxyalkylated cellulose nanocrystals (CNC) with similar charge densities but with tunable hairy structures were produced. The effect of carbon spacer of the grafted groups on the interaction of the CNC and a cationic surfactant, myristyl trimethyl ammonium bromide (MTAB), at different pH and salinity was explored. The CNC with longer grafted chain length was more hydrophobic, adsorbed more MTAB, and formed a more compact MTAB adlayer than did CNC with the shorter chain length. Also, the adsorption was higher at neutral pH, implying a high electrostatic attraction and hydrophobic interaction between substrates. The hydrophobic interaction of MTAB and hairy CNC in saline systems improved its adsorption. Although MTAB adsorbed more when its concentration was higher than its critical micelle concentration (CMC), the adsorbed adlayer had a less compact structure on the CNC surfaces.

Preparation, characterization, and antibacterial property of carboxymethyl cellulose derivatives bearing tetrabutylammonium salt

Carboxymethyl cellulose derivatives bearing tetrabutylammonium moieties (CMC-TBA) were synthesized by the acidification of carboxymethyl cellulose (CMC) followed by acid-base neutralization with tetrabutylammonium hydroxide. The products were identified by Fourier transform infrared (FT-IR), ¹H nuclear magnetic resonance (NMR) spectroscopy and the degrees of substitution (DS) values were also quantified according to the integral area values in ¹H NMR spectra. It was revealed that DS values had a positive relationship with the molar ratios of TBAOH to CMC. The antibacterial behaviors against gram-positive bacteria S. aureus and gram-negative bacteria E. coli were investigated using serial two-fold dilution method (MIC and MBC) and the disc diffusion method (inhibition zone). The results showed that comparison with CMC, all new CMC-TBA derivatives exhibited high antibacterial activity that depends on bacteria type and their degrees of cationization. The antibacterial action was more effective against S. aureus than E. coli, which could be attributed to the fact that the latter has a complicated bilayer structure of cell wall. Besides, an apparent tendency that the antibacterial activity of CMC-TBA derivatives enhanced with an increase in the degrees of cationization was found. This work suggests that these new derivatives can be introduced as efficient antibacterial biomaterials for biomedical purposes.

Natural rosin modified carboxymethyl cellulose delivery system with lowered toxicity for long-term pest control

The increasing world-wide demand for food has prompted the development of efficient and environmentally friendly pesticide formulations. In this article, we have prepared CMC-g-PRSG carrier based on two compounds from natural materials carboxymethyl cellulose (CMC) and rosin (RS). The model pesticide avermectin (AVM) was encapsulated through hydrophobic interaction, and self-assembled to form nanopesticide AVM@CMC-g-PRSG with an average particle size of 167 nm. The prepared nanopesticide displays enhanced dispersibility and stability of AVM in water, and can effectively adhere to the leaves to prevent loss. The release rate of AVM encapsulated in the nanocarrier can be controlled by adjusting pH, and AVM half-life under ultraviolet radiation shows a 3-fold increase allowing control of pests for prolonged periods of time in practical applications. Biological safety tests showed that AVM@CMC-g-PRSG effectively reduces the toxicity of AVM to aquatic animals. Therefore, the cheap and degradable carrier CMC-g-PRSG can improve the effect of hydrophobic pesticides.

Ionic liquids-modified cellulose coated magnetic nanoparticles for enzyme immobilization: Improvement of catalytic performance

In this work, ionic liquids-modified magnetic carboxymethyl cellulose nanoparticles (IL-MCMC) were prepared and used as supports for enzyme immobilization. The specific activity of immobilized lipase PPL-IL-MCMC was 1.43 and 2.81 folds higher than that of free PPL and PPL-MCMC, respectively. Water contact angle analysis indicated that the introduction of ionic liquids increased the hydrophobicity of supports, which in tune induced the lid-opening of lipase, allowing its active sites to become more accessible. In addition, the affinity between lipase and substrate immobilized on the prepared supports was enhanced. The same method was also applied to analyze immobilize penicillin G acylase (PGA) to further investigate the general applicability of the method. The results showed that the immobilized PGA exhibited higher stability than many other reported PGAs. The developed composites may be utilized as excellent supports for enzyme immobilization in industrial application.

NMR Spectroscopy for Metabolomics Research

Over the past two decades, nuclear magnetic resonance (NMR) has emerged as one of the three principal analytical techniques used in metabolomics (the other two being gas chromatography coupled to mass spectrometry (GC-MS) and liquid chromatography coupled with single-stage mass spectrometry (LC-MS)). The relative ease of sample preparation, the ability to quantify metabolite levels, the high level of experimental reproducibility, and the inherently nondestructive nature of NMR spectroscopy have made it the preferred platform for long-term or large-scale clinical metabolomic studies. These advantages, however, are often outweighed by the fact that most other analytical techniques, including both LC-MS and GC-MS, are inherently more sensitive than NMR, with lower limits of detection typically being 10 to 100 times better. This review is intended to introduce readers to the field of NMR-based metabolomics and to highlight both the advantages and disadvantages of NMR spectroscopy for metabolomic studies. It will also explore some of the unique strengths of NMR-based metabolomics, particularly with regard to isotope selection/detection, mixture deconvolution via 2D spectroscopy, automation, and the ability to noninvasively analyze native tissue specimens. Finally, this review will highlight a number of emerging NMR techniques and technologies that are being used to strengthen its utility and overcome its inherent limitations in metabolomic applications.

Depolymerization of carboxymethyl cellulose using hydrodynamic cavitation combined with ultraviolet irradiation and potassium persulfate

In the present work, hydrodynamic cavitation (HC) has been used for the depolymerization of sodium salt of carboxymethyl cellulose (CMC) solution. Use of two different cavitating devices as slit and circular venturi has been investigated along with the combination of HC with potassium persulfate (KPS) and ultraviolet (UV) irradiation for understanding the process intensification benefits. The effect of operating parameters as inlet pressure (HC) and power dissipation (UV based treatment) on the degree of polymerization has been studied initially. The combined approaches of HC + UV, HC + KPS and HC + UV + KPS have been then investigated under optimized conditions of pressure and power dissipation. Depolymerization was favored in the case of slit venturi in HC and at higher power dissipation for UV based approach as well as at higher KPS loading for the combined approach of HC + KPS. For the combined approach of HC + UV + KPS, maximum viscosity reduction obtained was 75% under the optimized conditions (slit venturi, 3 bar as the pressure, 8 W as UV power and KPS loading of 0.4 g/L) in 180 min of treatment. The chemical structure of the native CMC and processed CMC using all approaches was analyzed using FTIR spectra and it was clearly established that any significant changes in the chemical structure are not observed.

Determination of mole fractions of ethyl-cellulose-containing monomers by NMR

Three samples of ethyl cellulose (EC) with different degrees of substitution (DS)-0.51, 1.41, and 2.28-were prepared by a slurry method using ethyl bromide as the etherification reagent. ¹H-¹³C HSQC and HSQC-TOCSY NMR spectral analysis allowed for complete assignment of the ¹H and ¹³C chemical shifts, respectively, of eight anhydroglucose units (AGUs) comprising EC chains-un-, 2-mono-, 3-mono-, 6-mono-, 2,3-di-, 2,6-di-, 3,6-di-, and 2,3,6-tri-substituted AGUs. In addition, the lineshape of the quantitative ¹³C NMR spectra of the three EC samples provided change in the mole fractions of these AGUs against DS, making it possible to estimate the reaction mechanism for the production of EC, elucidating reactivities of the hydroxyl groups at the 2, 3, and 6 positions of cellulose and interactions between the substituent groups within the same AGU and vicinal AGUs.

NMR characterization of sodium carboxymethyl cellulose 2: Chemical shift assignment and conformation analysis of substituent groups

The chemical shifts of the substituent groups of sodium carboxymethyl cellulose (CMC) were assigned by examining a series of CMC samples with different degrees of substitution. Comparative analysis of the (1)H-(13)C heteronuclear single quantum coherence (HSQC) and heteronuclear multiple bond correlation (HMBC) spectra allowed the complete assignment of the substituent groups at the 2-, 3-, and 6-positions of the seven substituted monomers comprising the CMC chains, namely, 2-mono-, 3-mono-, 6-mono-, 2,3-di-, 2,6-di-, 3,6-di-, and 2,3,6-tri-substituted anhydroglucose units (AGUs). In addition, the mole fractions of the monomers were determined by lineshape analysis of the carbonyl carbon resonances. The comparison between the chemical shifts of the substituents revealed strong interactions between 2- and 3-substituents in the same AGU, and showed that the steric hindrance by a substituent at the 2- or 3-position suppresses subsequent substitution at the adjacent position.

The strengths and weaknesses of NMR spectroscopy and mass spectrometry with particular focus on metabolomics research

Mass spectrometry (MS) and nuclear magnetic resonance (NMR) have evolved as the most common techniques in metabolomics studies, and each brings its own advantages and limitations. Unlike MS spectrometry, NMR spectroscopy is quantitative and does not require extra steps for sample preparation, such as separation or derivatization. Although the sensitivity of NMR spectroscopy has increased enormously and improvements continue to emerge steadily, this remains a weak point for NMR compared with MS. MS-based metabolomics provides an excellent approach that can offer a combined sensitivity and selectivity platform for metabolomics research. Moreover, different MS approaches such as different ionization techniques and mass analyzer technology can be used in order to increase the number of metabolites that can be detected. In this chapter, the advantages, limitations, strengths, and weaknesses of NMR and MS as tools applicable to metabolomics research are highlighted.

Synthesis and characterization of carboxymethyl cellulose from office waste paper: a greener approach towards waste management

In the present study, functionalization of mixed office waste (MOW) paper has been carried out to synthesize carboxymethyl cellulose, a most widely used product for various applications. MOW was pulped and deinked prior to carboxymethylation. The deinked pulp yield was 80.62 ± 2.0% with 72.30 ± 1.50% deinkability factor. The deinked pulp was converted to CMC by alkalization followed by etherification using NaOH and ClCH2COONa respectively, in an alcoholic medium. Maximum degree of substitution (DS) (1.07) of prepared CMC was achieved at 50 °C with 0.094 M and 0.108 M concentrations of NaOH and ClCH2COONa respectively for 3h reaction time. The rheological characteristics of 1-3% aqueous solution of optimized CMC product showed the non-Newtonian pseudoplastic behavior. Fourier transform infra red (FTIR), nuclear magnetic resonance (NMR) and scanning electron microscope (SEM) study were used to characterize the CMC product.

Characterization and properties of carboxymethyl cellulose hydrogels crosslinked by polyethylene glycol

Novel hydrogels were prepared from carboxymethyl cellulose (CMC) sodium salt by crosslinking with polyethylene glycol diglycidyl ether (PEGDE). The detailed structures of the hydrogels were determined via FTIR and solid-state NMR spectroscopic analyses. Increasing the feed ratio of PEGDE to CMC in the reaction mixture led to an increase in the crosslinking degree, which enhanced the physical strength of the hydrogels. The hydrogels exhibited enzyme degradability, and after 3 days of incubation with cellulase, 62-28 wt% of the CMC in the hydrogel was degraded under the conditions employed in this study. In addition, the hydrogels exhibited protein adsorption and release abilities, and the amounts of proteins adsorbed on the hydrogels and the release profile of the proteins depended on the protein sizes and crosslinking degree of the hydrogels. These unique properties might enable the use of CMC-based hydrogels as drug delivery system carriers for protein-based drugs if the biological safety of the hydrogel can be verified.