Comparative Studies on Regioselectivity of α- and ß-Linked Glucan Tosylation.

Alpha- and beta-linked 1,3-glucans have been subjected to conversion with p-toluenesulfonic acid (tosyl) chloride and triethylamine under homogeneous reaction conditions in N,N-dimethyl acetamide/LiCl. Samples with a degree of substitution of tosyl groups (DSTs) of up to 1.91 were prepared by applying 5 mol reagent per mole repeating unit. Hence, the reactivity of α-1,3-glucan is comparable with cellulose and starch, while the ß-1,3-linked glucan curdlan is less reactive. The samples dissolve in aprotic dipolar media independent of the DSTs and possess a solubility in less polar solvents that depends on the DSTs. NMR studies on the tosyl glucans and of the peracylated derivatives showed a preferred tosylation of position 2 of the repeating unit. However, the selectivity is less pronounced compared with starch. It could be concluded that the α-configurated glycosidic bond directs tosyl groups towards position 2.

Development and validation of a capillary electrophoresis method for the characterization of sulfoethyl cellulose.

To characterize sulfoethyl cellulose el samples, a capillary electrophoresis method was developed and validated sulfoethyl cellulose el was hydrolyzed, and the resulting d-glucose derivatives were analyzed after reductive amination with 4-aminobenzoic acid using 150 mM boric acid, pH 9.5, as background electrolyte at 20°C and a voltage of 28 kV. Peak identification was derived from capillary electrophoresis with mass spectrometry using 25 mM ammonia adjusted to pH 6.2 by acetic acid as electrolyte. Besides mono-, di-, and trisulfoethyl d-glucose small amounts of disaccharides could be identified resulting from incomplete hydrolysis. The linearity of the borate buffer-based capillary electrophoresis method was evaluated using d-glucose in the concentration range of 3.9-97.5 µg/mL, while limits of detection and quantification derived from the signal-to-noise ratio of 3 and 10 were 0.4 ± 0.1 and 1.2 ± 0.3 µg/mL, respectively. Reproducibility and intermediate precision were determined using a hydrolyzed sulfoethyl cellulose el sample and ranged between 0.2 and 8.8% for migration times and between 0.3 and 10.4% for peak area. The method was applied to the analysis of the degree of substitution of synthetic sulfoethyl cellulose el samples obtained by variation of the synthetic process and compared to data obtained by elemental analysis.

HDACi Delivery Systems Based on Cellulose Valproate Nanoparticles.

The ability of histone deacetylase inhibitors (HDACi) like valproic acid (VPA) as a therapeutic for inflammatory diseases or cancer has increased the interest in HDACi and their targeted transport to diseased tissues. Administration of VPA immobilized on polymeric carriers was found to be a suitable approach to circumvent drawbacks such as rapid metabolization, short serum half-life, or side effects. Polysaccharides are convenient biopolymeric carriers due to their biocompatibility and biodegradability. Furthermore, the hydroxy-, amino-, or carboxylic groups are predestinated for functionalization. The esterification of three hydroxy groups of cellulose with VPA leads to products having a high amount of VPA loading. Subsequent shaping yielded uniform nanoparticles (NPs) of around 150 nm in size capable of releasing VPA in a controlled way under physiological conditions.

Investigation of cellulose dissolution in morpholinium-based solvents: impact of solvent structural features on cellulose dissolution.

A series of N-methylmorpholinium salts with varying N-alkyl chains and Cl-, OAc- and OH- as counter ions have been synthesized and investigated for their ability to dissolve cellulose, aiming at elucidating solvent structural features affecting cellulose dissolution. Synthesis procedures have been developed to, to a high extent, rely on conversions in water and microwave-assisted reactions employing a reduced number of work-up steps and ion-exchange resins that can be regenerated. Water solutions of morpholinium hydroxides proved capable of dissolving cellulose, with those of them possessing alkyl chains longer than ethyl showing surprising dissolution ability at room-temperature. Morpholinium acetates behaved as ionic liquids, and were also capable of dissolving cellulose when combined with DMSO. The obtained cellulose solutions were characterized according to their chemical and colloidal stability using 13C NMR spectroscopy, size exclusion chromatography and flow sweep measurements, while the ethanol coagulates were investigated in terms of crystallinity using solid state NMR. In contrast, the morpholinium chlorides obtained were hygroscopic with high melting points and low solubility in common organic solvents e.g., acetone, DMSO and DMAc, thus lacking the ability to swell or dissolve cellulose.

Correction: Investigation of cellulose dissolution in morpholinium-based solvents: impact of solvent structural features on cellulose dissolution.

[This corrects the article DOI: 10.1039/D3RA03370H.].

Structural and chemical insights into the prebiotic property of hemicellulosic polysaccharide from Santalum album L.

Hemicellulose was extracted by alkali treatment of de-pectinated cell wall material of Santalum album L. (sandalwood) suspension culture cells. The physicochemical properties and prebiotic activities of a purified major fraction of Hemicellulose-B, termed as HB-I, were investigated. GC analysis of hydrolyzed and derivatized HB-I showed the presence of arabinose (~64 %), galactose (~16 %) and glucose (~16 %) as major monosaccharide units along with minor amount of rhamnose. Methylation and NMR studies on the purified polysaccharide revealed the presence of 6-ß-d-Glcp, ß-d-Galp, 3,5-α-l-Araf, α-l-Araf, 5-α-l-Araf, 2,3-α-l-Araf and, α-l-Rhap residues, from which a proposed structure of repeating units was established. The growth of probiotic Lactobacillus spp. strains L. acidophilus, L. casei, L. plantarum and L. rhamnosus was promoted while that of Escherichia coli was suppressed significantly in presence of HB-I. Our results highlight valorization of sandalwood biomass and explore the role of mixed α, ß-linked heteroglycan as a potential prebiotic molecule thus indicating the possibility of development of low-cost bioprocesses for production of functional food ingredients.

Dually Modified Cellulose as a Non-Viral Vector for the Delivery and Uptake of HDAC3 siRNA.

RNA interference can be applied to different target genes for treating a variety of diseases, but an appropriate delivery system is necessary to ensure the transport of intact siRNAs to the site of action. In this study, cellulose was dually modified to create a non-viral vector for HDAC3 short interfering RNA (siRNA) transfer into cells. A guanidinium group introduced positive charges into the cellulose to allow complexation of negatively charged genetic material. Furthermore, a biotin group fixed by a polyethylene glycol (PEG) spacer was attached to the polymer to allow, if required, the binding of targeting ligands. The resulting polyplexes with HDAC3 siRNA had a size below 200 nm and a positive zeta potential of up to 15 mV. For N/P ratio 2 and higher, the polymer could efficiently complex siRNA. Nanoparticles, based on this dually modified derivative, revealed a low cytotoxicity. Only minor effects on the endothelial barrier integrity and a transfection efficiency in HEK293 cells higher than Lipofectamine 2000TM were found. The uptake and release of the polyplexes were confirmed by immunofluorescence imaging. This study indicates that the modified biopolymer is an auspicious biocompatible non-viral vector with biotin as a promising moiety.

Analysis of HDACi-Coupled Nanoparticles: Opportunities and Challenges.

Systemic administration of histone deacetylase inhibitors (HDACi), like valproic acid (VPA), is often associated with rapid drug metabolization and untargeted tissue distribution. This requires high-dose application that can lead to unintended side effects. Hence, drug carrier systems such as nanoparticles (NPs) are developed to circumvent these disadvantages by enhancing serum half-life as well as organ specificity.This chapter gives a summary of the biological characterization of HDACi-coupled NPs in vitro, including investigation of cellular uptake, biocompatibility, as well as intracellular drug release and activity. Suitable methods, opportunities, and challenges will be discussed to provide general guidelines for the analysis of HDACi drug carrier systems with a special focus on recently developed cellulose-based VPA-coupled NPs.

Thermoresponsive hydrogel of diblock methylcellulose: formation of ribbonlike supramolecular nanostructures by self-assembly.

This article provides detailed insight into the thermoresponsive gelation mechanism of industrially produced methylcellulose (MC), highlighting the importance of diblock structure with a hydrophobic sequence of 2,3,6-tri-O-methyl-glucopyranosyl units for this physicochemical property. We show herein, for the first time, that well-defined diblock MC self-assembles thermoresponsively into ribbonlike nanostructures in water. A cryogenic transmission electron microscopy (cryo-TEM) technique was used to detect the ribbonlike nanostructures formed by the diblock copolymers consisting of hydrophilic glucosyl or cellobiosyl and hydrophobic 2,3,6-tri-O-methyl-cellulosyl blocks, methyl ß-D-glucopyranosyl-(1→4)-2,3,6-tri-O-methyl-celluloside 1 (G-236MC, DP(n) = 10.7, DS = 2.65), and methyl ß-D-glucopyranosyl-(1→4)-ß-D-glucopyranosyl-(1→4)-2,3,6-tri-O-methyl-celluloside 2 (GG-236MC, DP(n) = 28.2, DS = 2.75). Rheological measurements revealed that the gel strength of a dispersion of GG-236MC (2, 2.0 wt %) in water at 70 °C was 3.0 times stronger than that of commercial MC SM-8000, although the molecular weight of GG-236MC (2) having M(w) = 8 × 10(3) g/mol was 50 times smaller than that of SM-8000 having M(w) = 4 × 10(5) g/mol. Cryo-TEM observation suggested that the hydrogel formation of the diblock copolymers could be attributed to the entanglement of ribbonlike nanostructures self-assembled by the diblock copolymers in water. The cryo-TEM micrograph of GG-236MC (2) at 5 °C showed rectangularly shaped nanostructures having a thickness from 11 to 24 nm, although G-236MC (1) at 20 °C showed no distinct self-assembled nanostructures. The ribbonlike nanostructures of GG-236MC (2) having a length ranging from 91 to 864 nm and a thickness from 8.5 to 27.1 nm were detected above 20 °C. Small-angle X-ray scattering measurements suggested that the ribbonlike nanostructures of GG-236MC (2) consisted of a bilayer structure with a width of ca. 40 nm. It was likely that GG-236MC (2) molecules were oriented perpendicularly to the long axis of the ribbonlike nanostructure. In addition, wide-angle X-ray scattering measurements revealed that GG-236MC (2) in its hydrogel formed the same crystalline regions as 2,3,6-tri-O-methylcellulose. The influence of the DP of diblock MC with a DS of around 2.7 on the gelation behavior will be discussed.

2-O-Methyl- and 3,6-di-O-methyl-cellulose from natural cellulose: synthesis and structure characterization.

For the first time, 2-O-methyl- (2MC) and 3,6-di-O-methyl-cellulose (36MC) were synthesized via 3-O-allyl- and 3-O-methyl-cellulose, respectively. Position 6 of 3-O-allyl- and 3-O-methyl-cellulose was protected with the 4-methoxytrityl groups. The reaction time and temperature were optimized to achieve a high regioselectivity at C-6 and to prevent the introduction of the 4-methoxytrityl group at C-2 of the polymer. It was found that the substituent at C-3 of 3-O-functionalized celluloses influenced the reactivity of the hydroxyl group at C-6. The structure was characterized by means of (1)H and (13)C NMR spectroscopy of the acetates of 2MC and 36MC. 2MC and 36MC were soluble in water and did not show thermoreversible gelation.

Mixed 3-mono-O-alkyl cellulose: synthesis, structure characterization and thermal properties.

The 3-mono-O-alkyl cellulose samples bearing two different ether moieties, namely methyl/ethyl, methyl/n-propyl, and ethyl/n-propyl were synthesized applying protecting group technique. The NMR spectra of the peracetylated products revealed the regioselectivity of the alkylation as well as the degree of substitution of both alkyl moieties. The number average degree of polymerization (DPn) monitored by size exclusion chromatography decreases from DPn 117 (Avicel PH-101, starting material) to DPn 34 (sample 4f) due to the multi-step synthesis. It could be demonstrated that the lower critical solution temperature (LCST) is influenced by the degree of substitution of both alkyl groups. For example, LCST values between 33 and 58 °C were measured for aqueous solutions of 3-mono-O-ethyl/n-propyl cellulose. On the contrary, the thermal behavior of a physical mixture of 3-mono-O-ethyl- and 3-mono-O-n-propyl cellulose, e.g., was controlled by the derivative with the lowest LCST.

Waterproof-breathable films from multi-branched fluorinated cellulose esters.

Cellulose ester films were prepared by esterification of cellulose with a multibranched fluorinated carboxylic acid, "BRFA" (BRanched Fluorinated Acid), at different anhydroglucose unit:BRFA molar ratios (i.e., 1:0, 10:1, 5:1, and 1:1). Morphological and optical analyses showed that cellulose-BRFA materials at molar ratios 10:1 and 5:1 formed flat and transparent films, while the one at 1:1 M ratio formed rough and translucent films. Degrees of substitution (DS) of 0.06, 0.09, and 0.23 were calculated by NMR for the samples at molar ratios 10:1, 5:1, and 1:1, respectively. ATR-FTIR spectroscopy confirmed the esterification. DSC thermograms showed a single glass transition, typical of amorphous polymers, at -11 °C. The presence of BRFA groups shifted the mechanical behavior from rigid to ductile and soft with increasing DS. Wettability was similar to standard fluoropolymers such as PTFE and PVDF. Finally, breathability and water uptake were characterized and found comparable to materials typically used in textiles.

Biocompatible sulfated valproic acid-coupled polysaccharide-based nanocarriers with HDAC inhibitory activity.

The development of bio-based nanoparticles (NPs) as drug containers is of increasing interest to circumvent several obstacles in drug therapy such as rapid drug metabolization, short serum half-life, and unspecific side effects. The histone deacetylase inhibitor valproic acid (VPA) is known for its anti-inflammatory as well as for its anti-cancer activity. Here, recently developed VPA-loaded NPs based on cellulose- and dextran VPA esters were modified with sulfuric acid half ester moieties to improve intracellular drug release. The NPs show rapid cellular uptake, are non-toxic in vitro and in vivo, and able to induce histone H3 hyperacetylation. Thus, they represent a potent drug delivery system for the application in a variety of treatment settings, such as inflammation, sepsis and defined cancer types. In addition, the flexible NP-system offers a broad range of further options for modification, e.g. for targeting strategies and multi-drug approaches.

Sulfoethylation of polysaccharides-A comparative study.

The heterogeneous sulfoethylation of cellulose, xylan, α-1,3-glucan, glucomannan, pullulan, curdlan, galactoglucomannan, and agarose was studied using sodium vinylsulfonate (NaVS) as reagent in presence of sodium hydroxide and iso-propanol (i-PrOH) as slurry medium. The influence of the concentration of polymer, water, and NaOH (solid or aqueous solution) on the degree of substitution (DS) was investigated. The sulfoethylation rendered the polysaccharides studied water-soluble. Sulfoethylation of heteropolysaccharides yielded products with higher DS compared to the conversion of homopolysaccharides. Structure characterization was carried out by means of 13C-NMR spectroscopy.

Polysaccharide Nanoparticles Bearing HDAC Inhibitor as Nontoxic Nanocarrier for Drug Delivery.

The histone deacetylase inhibitors (HDACi) are potent drugs in the treatment of inflammatory diseases and defined cancer types. However, major drawbacks of HDACi, such as valproic acid (VPA), are limited serum half-life, side effects and the short circulation time. Thus, the immobilization of VPA in a polysaccharide matrix is used to circumvent these problems and to design a suitable nanocarrier system. Therefore, VPA is covalently attached to cellulose and dextran via esterification with degree of substitution (DS) values of up to 2.20. The resulting hydrophobic polymers are shaped to spherical nanoparticles (NPs) with hydrodynamic diameter between 138 to 221 nm and polydispersity indices from 0.064 to 0.094 by nanoprecipitation and emulsification technique. Lipase treatment of the NPs leads to in vitro release of VPA and hence to an inhibition of HDAC2 activity in a HDAC2 assay. NPs are rapidly taken up by HeLa cells and mainly localize in the cytoplasm. The NPs are hemocompatible and nontoxic as revealed by the shell-less hen's egg model.

Structural elucidation of a heteropolysaccharide from the wild mushroom Marasmiellus palmivorus and its immune-assisted anticancer activity.

The biological activity of macrofungal polysaccharides (MFPS) depends on their structural features and is a topic of keen interest for researchers since long time. In this communication, we report a water soluble macrofungal heteropolysaccharide (MFPS1) with a molar weight of ˜145,000 g/mol, obtained through alkali extraction, of the wild mushroom, Marasmiellus palmivorus, with significant immunomodulatory properties. In cancer, after the induction of metastasis, the anticancer immune system becomes unresponsive. By studying cytokine secretion and immune phenotyping, it was observed that MFPS1 reactivated the anticancer immune surveillance system. MFPS1 executed T-cell maturation and activation via M1Φ; and also stimulated natural killer (NK) cell and B-cell population. The entire immune activation pathway corroborates its anticancer activity. The RP-HPLC analysis of hydrolyzed MFPS1 showed arabinose, glucose, galactose and mannose as monosaccharide units. The proposed structure of repeating unit was established from methylation analysis, 1D- and 2D NMR study, HR-MS and MALDI-TOF MS analysis.

Neutral Polysaccharide from the Leaves of Pseuderanthemum carruthersii: Presence of 3-O-Methyl Galactose and Anti-Inflammatory Activity in LPS-Stimulated RAW 264.7 Cells.

Pseuderanthemum carruthersii (Seem.) Guillaumin is a native tree in Vietnam. The water extract of the leaves from this tree gives a highly viscous product that has been used to heal wounds and treat inflammations. Our previous studies showed that the leaves of P. carruthersii have a high content of polysaccharides. In this study, the structure and influence of the neutral polysaccharide from Pseuderanthemum carruthersii (PCA1) on lipopolysaccharide (LPS)-stimulated RAW264.7 cells were investigated. The PCA1 isolated from P. carruthersii is a galactan-type polysaccharide, containing galactose (77.0%), 3-O-methyl galactose (20.0%), and arabinose (3.0%). Linkage analysis of PCA1 showed that both the 3-O-methyl galactose and galactose were 1,4-linked. The presence of 3-O-methyl galactose units as part of the polysaccharide is important and can be used as a chemotaxonomic marker. The molecular weight of the PCA1 was 170 kDa. A PCA1 concentration of 30-40 µg/mL strongly inhibited TNFα, IL-1ß, and IL-6 inflammatory cytokine production, and reactive oxygen species (ROS) release. PCA1 had inhibitory activities on pro-inflammatory cytokine and ROS release in LPS-stimulated mouse macrophages in vitro through MAPK signaling.

Mercerization effect on structure and electrical properties of cellulose: Development of a novel fast Na-ionic conductor.

Mercerized cellulose (alkali cellulose C6H10O5* NaOH) was obtained by treatment of cotton linters (cellulose) with aqueous sodium hydroxide. Cellulose and alkali-cellulose samples with relative density of 78% and 79% were obtained after sintering the material in air at optimal sintering temperatures of 423 K and 473 K, respectively. The electrical properties of the samples were studied by impedance spectroscopy in the frequency range from 13 MHz to 50 Hz at temperatures between 393 K and 493 K. The influence of cellulose mercerization on electrical properties of cotton linters was observed. The cellulose behaves like an electrical insulator. Contrariwise, the alkali-cellulose is a fast-ionic conductor with a conductivity value of σ473 K = 3.22 × 10-6 S cm-1 having activation energies of 0.49 eV and 0.68 eV at temperature range of 393 K-458 K and 459 K-500 K, respectively. The change of activation energy value has been discussed in relation to thermal stability.

Water-soluble 3-O-(2-methoxyethyl)cellulose: synthesis and characterization.

The synthesis of novel 3-O-(2-methoxyethyl)cellulose via 2,6-di-O-thexyldimethylsilyl ethers was successfully carried out. Treatments of 3-O-(2-methoxyethyl)-2,6-di-O-thexyldimethylsilylcellulose with tetrabutylammonium fluoride trihydrate led to a complete removal of the protecting groups. Structure characterization carried out by means of 1D and 2D NMR spectroscopy proves a high regioselectivity. The novel cellulose ether is soluble in dimethyl sulfoxide, N,N-dimethylacetamide, N-methylpyrrolidone, and water. Size-exclusion chromatography revealed a distinct aggregation behavior in water.

Hydrogen bond formation in regioselectively functionalized 3-mono-O-methyl cellulose.

The hydrogen bond systems of cellulose and its derivatives are one of the most important factors regarding their physical- and chemical properties such as solubility, crystallinity, gel formation, and resistance to enzymatic degradation. In this paper, it was attempted to clarify the intra- and intermolecular hydrogen bond formation in regioselectively functionalized 3-mono-O-methyl cellulose (3MC). First, the 3MC was synthesized and the cast film thereof was characterized in comparison to 2,3-di-O-methyl cellulose, 6-mono-O-methyl cellulose, and 2,3,6-tri-O-methyl cellulose by means of wide angle X-ray diffraction (WAXD) and (13)C cross polarization/magic angle spinning NMR spectroscopy. Second, the hydrogen bonds in the 3MC film were analyzed by means of FTIR spectroscopy in combination with a curve fitting method. After deconvolution, the resulting two main bands (Fig. 3) indicated that instead of intramolecular hydrogen bonds between position OH-3 and O-5 another intramolecular hydrogen bond between OH-2 and OH-6 may exist. The large deconvoluted band at 3340cm(-1) referred to strong interchain hydrogen bonds involving the hydroxyl groups at C-6. The crystallinity of 54% calculated from the WAXD supports also the dependency of the usually observed crystallization in cellulose of the hydroxyl groups at C-6 to engage in interchain hydrogen bonding.