Efficient heterogeneous synthesis of nucleophilic carboxymethyl hydrazides of polysaccharides.

Nucleophilic moieties in polysaccharides (PS) with distinct higher reactivity compared with the hydroxy group are interesting for sustainable applications in chemistry, medicine, and pharmacy. An efficient heterogeneous method for the formation of such nucleophilic PS is described. Employing alcohols as slurry medium, protonated carboxymethyl (CM) PS and hydrazine hydrate are allowed to react at elevated temperatures. The CM derivatives of starch and pullulan can be transformed almost quantitatively to the corresponding hydrazides. The reaction is less efficient for CM dextrans and CM xylans. As slurry media, 2-propanol and ethanol were probed, and the results are compared with a homogeneous procedure performed in water. Overall, the heterogeneous procedure is superior compared with the homogeneous route. 2-Propanol is the best slurry medium investigated yielding PS hydrazides with the highest nitrogen content.

Direct Functionalization of Polysaccharide-Based Xylan Phenyl Carbonate Nanoparticles with Tumor Cell Specific Antibodies.

An efficient and easy-to-use approach is presented for obtaining biocompatible polysaccharide-based nanoparticles (NP) that can act as tumor-specific drug delivery agents. Two antibodies are directly immobilized onto reactive xylan phenyl carbonate (XPC) NP; namely Cetuximab (CTX) that binds to human epidermal growth factor receptor (EGFR) and Atezolizumab (ATZ) that binds to programmed death-ligand 1 (PD-L1). High coupling efficiency (up to 100 %) are achieved without any pre-activation and no aggregation occurs during antibody immobilization. By quartz crystal microbalance experiments with dissipation monitoring (QCM-D), flow cytometry assays, and confocal laser scanning microscopy imaging it is demonstrated that the functionalized XPC-NP specifically bind to cells carrying the corresponding antigens. Moreover, the NP retain the antibody specific bioactivities (growth inhibition for CTX and induction of T-cell cytotoxicity for ATZ).

Synthesis and characterization of nucleophilic polysaccharide carbazates.

A simple synthesis of amino polysaccharides (PS) could be developed. Phenyl carbonates (PC) of xylan, dextran, and cellulose were easily transferred into PS carbazates by conversion with hydrazine hydrate. The degree of substitution could be adjusted by varying the molar ratio of hydrazine to PS repeating unit, enabling the preparation of both pure PS carbazates and derivatives with bifunctional reactivity containing the reactive PC and the amino group of the carbazate moiety. Further functionalization of the derivatives is feasible with carbonyl compounds like aldehydes at the carbazate groups. The reactivity of carbazate groups is shown by the reaction with 4-fluorobenzaldehyde, resulting in the formation of Schiff base conjugates.

The European Polysaccharide Network of Excellence (EPNOE) research roadmap 2040: Advanced strategies for exploiting the vast potential of polysaccharides as renewable bioresources.

Polysaccharides are among the most abundant bioresources on earth and consequently need to play a pivotal role when addressing existential scientific challenges like climate change and the shift from fossil-based to sustainable biobased materials. The Research Roadmap 2040 of the European Polysaccharide Network of Excellence (EPNOE) provides an expert's view on how future research and development strategies need to evolve to fully exploit the vast potential of polysaccharides as renewable bioresources. It is addressed to academic researchers, companies, as well as policymakers and covers five strategic areas that are of great importance in the context of polysaccharide related research: (I) Materials & Engineering, (II) Food & Nutrition, (III) Biomedical Applications, (IV) Chemistry, Biology & Physics, and (V) Skills & Education. Each section summarizes the state of research, identifies challenges that are currently faced, project achievements and developments that are expected in the upcoming 20 years, and finally provides outlines on how future research activities need to evolve.

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.].

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.

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.

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.

Dextran thioparaconate - Evaluation of the multifunctional thiolactone linker for easily adaptable polysaccharide modification.

For the preparation of tailored polymers based on polysaccharides, an easy adaptable modification method was developed by introduction of a multifunctional linker into the polymer backbone. Dextran was functionalized with a thiolactone compound that can be further treated with amine resulting in ring opening and formation of a thiol. The functional thiol group emerging can be used for crosslinking or introduction of a further functional compound by disulfide formation. Here, the efficient esterification of thioparaconic acid after in-situ activation and studies about reactivity of the dextran thioparaconate obtained are discussed. The derivative was converted by aminolysis with model compound hexylamin and the thiol generated therefrom was subsequently converted with an activated functional thiol to the corresponding disulfide. The thiolactone, which protects the thiol, enables efficient esterification without side reactions and allows storage of the polysaccharide derivative at ambient conditions for years. Not only the multifunctional reactivity of the derivative but also the end product with a balanced ratio of hydrophobic and cationic moiety is appealing for biomedical application.

Velocity-dependent heat transfer controls temperature in fracture networks.

Heat transfer between a fluid and the surrounding rock in the subsurface is a crucial process not only, but most obviously, in geothermal systems. Heat transfer is described by Newton's law of cooling, relating the heat transferred to a coefficient, the specific surface area, and the temperature difference between rock and fluid. However, parameterizing the heat transfer coefficient in fracture networks poses a major challenge. Here we show that within a fracture network the heat transfer coefficient is strongly heterogeneous but that laboratory single fracture experiments can provide a reasonable estimate in dependence of flow rate. We investigate the distribution of the heat transfer coefficient experimentally as well as numerically and analyze the heat transfer at individual fractures. Our results improve the prediction of temperatures in engineered and natural geothermal systems and allow sustainable management and design of reservoirs considering the role of individual fractures.

Reactive xylan derivatives for azid-/alkyne-click-chemistry approaches - From modular synthesis to gel-formation.

A modular synthesis was developed to obtain reactive xylan derivatives that are accessible for further functionalization and chemical crosslinking by click-chemistry approaches. Xylan phenylcarbonates (XPCs) with degrees of substitution (DS) from 0.62 to 1.94 were converted with propargyl amine (PA) or 6-azidohexan-1-amine (AA) to introduce either alkynyl- or azido moieties into the polymer backbone. Quantitative conversion of the XPC derivatives into functional xylan carbamates (XCs) with well-defined DS values was achieved. The molecular structure of the compounds was confirmed by FTIR- and NMR spectroscopy. Covalent crosslinking of alkynyl-functionalized XCs with bisazide linkers was achieved by copper-catalyzed 1,3-dipolar cycloaddition in an organic medium and the gelation process was studied by rheological experiments. Finally, it was demonstrated that mixed XCs with a reactive moiety and another functional group, which induce water solubility, are accessible. The corresponding products are suitable for the preparation of xylan-based hydrogels.

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.

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.

[Innovation Crisis in Public Theatre? A Longitudinal Study of Theaters in North Rhine-Westphalia, 1995-2018]. / Innovationskrise im staatlichen Theatersektor? Eine Längsschnitt-Analyse für Theater in Nordrhein-Westfalen, 1995­2018.

This paper examines cultural innovations in German public theaters, using North Rhine-Westphalia (NRW) as the most populated region as an example. While existing analyses, including social structure-centered audience research, have focused on the demand side, diagnosing in particular the steady decline and aging of the cultural audience, our analysis addresses the supply side, especially the number of premieres and new productions as well as their adoption into the repertoire. The paper shows that recent efforts by public theaters on the municipal or regional level to increase both the number of venues and the number of plays have not been sufficient to stabilize the declining audience. Too few new plays are scheduled, of which even fewer make it into the long-term repertoire. Our results suggest that theaters can retain their capability for renewal only by staging significantly more new plays, thus attracting new audiences. With regard to such renewal, decentralized competition as a characteristic of the NRW theater landscape seems a favorable institutional context.

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.

Starch Formates: Synthesis and Modification.

Starch can be efficiently converted into the corresponding formates homogeneously using N-formyl imidazole obtained by the reaction of 1,1'-carbonyldiimidazole and formic acid in dimethyl sulfoxide as a solvent. Starch formates are soluble in polar aprotic solvents, not susceptible against hydrolysis, and not meltable. Thermoplastics could be generated by conversion of starch formates with long-chain fatty acids exemplified by the conversion with lauroyl chloride in N,N-dimethylacetamide, leading to mixed starch laurate formates. The mixed esters show melting temperatures mainly dependent on the amount of laurate ester moieties.

Reactive Nanoparticles Derived from Polysaccharide Phenyl Carbonates.

Polysaccharide (PS) based nanoparticles (NP) are of great interest for biomedical applications. A key challenge in this regard is the functionalization of these nanomaterials. The aim of the present work was the development of reactive PS-NP that can be coupled with an amino group containing compounds under mild aqueous conditions. A series of cellulose phenyl carbonates (CPC) and xylan phenyl carbonates (XPC) with variable degrees of substitution (DS) was obtained by homogeneous synthesis. The preparation of PS-NP by self-assembling of these hydrophobic derivatives was studied comprehensively. While CPC mostly formed macroscopic aggregates, XPC formed well-defined spherical NP with diameters around 100 to 200 nm that showed a pronounced long-term stability in water against both particle aggregation as well as cleavage of phenyl carbonate moieties. Using an amino group functionalized dye it was demonstrated that the novel XPC-NP are reactive towards amines. A simple coupling procedure was established that enables direct functionalization of the reactive NP in an aqueous dispersion. Finally, it was demonstrated that dye functionalized XPC-NP are non-cytotoxic and can be employed in advanced biomedical applications.

Advanced characterization of regioselectively substituted methylcellulose model compounds by DNP enhanced solid-state NMR spectroscopy.

Dynamic Nuclear Polarization MAS NMR is introduced to characterize model methylcellulose ether compounds at natural isotopic abundance. In particular an approach is provided to determine the position of the methyl ether group within the repeating unit. Specifically, natural abundance 13C-13C correlation experiments are used to characterize model 3-O-methylcellulose and 2,3-O-dimethylcellulose, and identify changes in chemical shifts with respect to native cellulose. We also probe the use of through space connectivity to the closest carbons to the CH3 to identify the substitution site on the cellulose ether. To this end, a series of methylcellulose ethers was prepared by a multistep synthesis approach. Key intermediates in these reactions were 2,6-O-diprotected thexyldimethylsilyl (TDMS) cellulose and 6-O-monoprotected TDMS cellulose methylated under homogeneous conditions. The products had degrees of substitution of 0.99 (3-O-methylcellulose) and 2.03 (2,3-O-dimethylcellulose) with exclusively regioselective substitution. The approaches developed here will allow characterization of the substitution patterns in cellulose ethers.

Biocompatible valproic acid-coupled nanoparticles attenuate lipopolysaccharide-induced inflammation.

Inflammatory diseases like sepsis are associated with dysregulated gene expression, often caused by an imbalance of epigenetic regulators, such as histone acetyltransferases (HATs) and histone deacetylases (HDACs), and consequently, altered epigenetic chromatin signatures or aberrant posttranslational modifications of signalling proteins and transcription factors. Thus, HDAC inhibitors (HDACi) are a promising class of anti-inflammatory drugs. Recently, an efficient drug delivery system carrying the class I/IIa selective HDACi valproic acid (VPA) was developed to circumvent common disadvantages of free drug administration, e.g. short half-life and side effects. The cellulose-based sulphated VPA-coupled (CV-S) nanoparticles (NPs) are rapidly taken up by cells, do not cause any toxic effects and are fully biocompatible. Importantly, VPA is intracellularly cleaved from the NPs and HDACi activity could be proven. Here, we demonstrate that CV-S NPs exhibit overall anti-inflammatory effects in primary human macrophages and are able to attenuate the lipopolysaccharide-induced inflammatory response. CV-S NPs show superior potential to free VPA to suppress the TLR-MyD88-NF-κB signalling axis, leading to decreased TNF-α expression and secretion.

Efficient heterogeneous synthesis of reactive polygalacturonic acid hydrazides.

Low-methoxy ammonium pectinate (APC) and polygalacturonic acid (PG) could be transformed heterogeneously in a catalyst-free system very efficiently to the corresponding polysaccharide (PS) hydrazides. The hydrazide formation proceeds even at room temperature efficiently and is almost independent of the reaction temperature in the range from 25 of up to 80°C. In contrast to a homogeneous reaction, the heterogeneous path is efficient considering the amount of hydrazine hydrate employed. The PS hydrazides obtained show no signs of degradation or side reactions that might occur due to the basicity of the hydrazine reagent used. The polygalacturonic acid hydrazide (PGH) obtained is nontoxic as revealed by a chicken egg test. Furthermore, preliminary studies indicate that the PS hydrazides synthesized possess good metal chelating abilities, especially high amount of lead (II) can be bound from an aqueous solution.