Integrating Cellulose Microfibrils and Ellagitannins from Rambutan Peel with Gelatin for Production of Synergistic Biobased Hydrogels.

The pursuit of renewable and eco-friendly raw materials for biobased materials is a growing field. This study utilized ellagitannin and cellulose microfibrils derived from rambutan peel waste alongside gelatin to develop eco-conscious hydrogels. The cellulose/gelatin hydrogels were formulated in two weight ratios (0.5:1 to 1:1), and the influence of gelatin on the chemical composition and rheology was studied. Composite hydrogels, functionalized with an ellagitannin-rich extract, exhibited a remarkable enhancement of up to 14-fold in compressive strength. The hydrogels also demonstrated antimicrobial properties, reducing the Staphylococcus aureus colony count within 24 h. The hydrogel, derived from rambutan peel waste, is biocompatible and could potentially be explored for biomedical applications such as drug delivery systems, and wound dressings. This suggests that it might offer significant value for sustainable materials science, although specific applications have yet to be tested.

Template-Directed Polymerization of Binary Acrylate Monomers on Surface-Activated Lignin Nanoparticles in Toughening of Bio-Latex Films.

Fabricating bio-latex colloids with core-shell nanostructure is an effective method for obtaining films with enhanced mechanical characteristics. Nano-sized lignin is rising as a class of sustainable nanomaterials that can be incorporated into latex colloids. Fundamental knowledge of the correlation between surface chemistry of lignin nanoparticles (LNPs) and integration efficiency in latex colloids and from it thermally processed latex films are scarce. Here, an approach to integrate self-assembled nanospheres of allylated lignin as the surface-activated cores in a seeded free-radical emulsion copolymerization of butyl acrylate and methyl methacrylate is proposed. The interfacial-modulating function on allylated LNPs regulates the emulsion polymerization and it successfully produces a multi-energy dissipative latex film structure containing a lignin-dominated core (16% dry weight basis). At an optimized allyl-terminated surface functionality of 1.04 mmol g-1 , the LNPs-integrated latex film exhibits extremely high toughness value above 57.7 MJ m-3 . With multiple morphological and microstructural characterizations, the well-ordered packing of latex colloids under the nanoconfinement of LNPs in the latex films is revealed. It is concluded that the surface chemistry metrics of colloidal cores in terms of the abundance of polymerization-modulating anchors and their accessibility have a delicate control over the structural evolution of core-shell latex colloids.

Flavonoids naringenin chalcone, naringenin, dihydrotricin, and tricin are lignin monomers in papyrus.

Recent studies demonstrate that several polyphenolic compounds produced from beyond the canonical monolignol biosynthetic pathways can behave as lignin monomers, participating in radical coupling reactions and being incorporated into lignin polymers. Here, we show various classes of flavonoids, the chalconoid naringenin chalcone, the flavanones naringenin and dihydrotricin, and the flavone tricin, incorporated into the lignin polymer of papyrus (Cyperus papyrus L.) rind. These flavonoids were released from the rind lignin by Derivatization Followed by Reductive Cleavage (DFRC), a chemical degradative method that cleaves the ß-ether linkages, indicating that at least a fraction of each was integrated into the lignin as ß-ether-linked structures. Due to the particular structure of tricin and dihydrotricin, whose C-3' and C-5' positions at their B-rings are occupied by methoxy groups, these compounds can only be incorporated into the lignin through 4'-O-ß bonds. However, naringenin chalcone and naringenin have no substituents at these positions and can therefore form additional carbon-carbon linkages, including 3'- or 5'-ß linkages that form phenylcoumaran structures not susceptible to cleavage by DFRC. Furthermore, Nuclear Magnetic Resonance analysis indicated that naringenin chalcone can also form additional linkages through its conjugated double bond. The discovery expands the range of flavonoids incorporated into natural lignins, further broadens the traditional definition of lignin, and enhances the premise that any phenolic compound present at the cell wall during lignification could be oxidized and potentially integrated into the lignin structure, depending only on its chemical compatibility. This study indicates that papyrus lignin has a unique structure, as it is the only lignin known to date that integrates such a diversity of phenolic compounds from different classes of flavonoids. This discovery will open up new ways to engineer and design lignins with specific properties and for enhanced value.

Reductive Amination of Dialdehyde Cellulose: Access to Renewable Thermoplastics.

The reductive amination of dialdehyde cellulose (DAC) with 2-picoline borane was investigated for its applicability in the generation of bioderived thermoplastics. Five primary amines, both aliphatic and aromatic, were introduced to the cellulose backbone. The influences of the side chains on the course of the reaction were examined by various analytical techniques with microcrystalline cellulose as a model compound. The obtained insights were transferred to a 39%-oxidized softwood kraft pulp to study the thermal properties of thereby generated high-molecular-weight thermoplastics. The number-average molecular weights (Mn) of the diamine celluloses, ranging from 60 to 82 kD, were investigated by gel permeation chromatography. The diamine celluloses exhibited glass transition temperatures (Tg) from 71 to 112 °C and were stable at high temperatures. Diamine cellulose generated from aniline and DAC showed the highest conversion, the highest Tg (112 °C), and a narrow molecular weight distribution (D̵ of 1.30).

Assessing Fire-Damage in Historical Papers and Alleviating Damage with Soft Cellulose Nanofibers.

The conservation of historical paper objects with high cultural value is an important societal task. Papers that have been severely damaged by fire, heat, and extinguishing water, are a particularly challenging case, because of the complexity and severity of damage patterns. In-depth analysis of fire-damaged papers, by means of examples from the catastrophic fire in a 17th-century German library, shows the changes, which proceeded from the margin to the center, to go beyond surface charring and formation of hydrophobic carbon-rich layers. The charred paper exhibits structural changes in the nano- and micro-range, with increased porosity and water sorption. In less charred areas, cellulose is affected by both chain cleavage and cross-linking. Based on these results and conclusions with regard to adhesion of auxiliaries, a stabilization method is developed, which coats the damaged paper with a thin layer of cellulose nanofibers. It enables the reliable preservation of the paper and-most importantly-retrieval of the contained historical information: the nanofibers form a flexible, transparent film on the surface and adhere strongly to the damaged matrix, greatly reducing its fragility, giving it stability, and enabling digitization and further handling.

High-Resolution Profiling of the Functional Heterogeneity of Technical Lignins.

In technical lignins, functionality is strongly related to molar mass. Hence, any technical lignin exhibits concurrent functionality-type distribution (FTD) along its molar mass distribution (MMD). This study combined preparative size-exclusion chromatography with offline characterizations to acquire highly resolved profiles of the functional heterogeneity of technical lignins, which represent crucial information for their material use. The shape of these profiles showed considerable dissimilarity between different technical lignins and followed sigmoid trends. Determining the dispersity in functionality (DF) of lignins via their FTD revealed a rather homogeneous distribution of their functionalities (DF of 1.00-1.21). The high resolution of the acquired profiles of functional heterogeneity facilitated the development of a robust calculation method for the estimation of functional group contents of lignin fractions based simply on their MMD, an invaluable tool to simulate the effects of intended purification processes. Moreover, a more thorough evaluation of separations based on functionality becomes accessible.

Synthesis of Polyanionic Cellulose Carbamates by Homogeneous Aminolysis in an Ionic Liquid/DMF Medium.

Polyanionic cellulose carbamates were synthesized by rapid and efficient homogeneous aminolysis of cellulose carbonate half-esters in an ionic liquid/DMF medium. Cellulose bis-2,3-O-(3,5-dimethylphenyl carbamate), as a model compound, reacted with different chloroformates to cellulose carbonates. These intermediates were subjected to aminolysis, for which both the reactivity of different chloroformates towards C6-OH and the reactivity/suitability of the respective carbonate half-ester in the aminolysis were comprehensively studied. Phenyl chloroformate and 4-chlorophenyl chloroformate readily reacted with C6-OH of the model cellulose derivative, while 4-nitrophenyl chloroformate did not. The intermediate 4-chlorophenyl carbonate derivative with the highest DS (1.05) was then used to evaluate different aminolysis pathways, applying three different amines (propargyl amine, ß-alanine, and taurine) as reactants. The latter two zwitterionic compounds are only sparingly soluble in pure DMF as the typical reaction medium for aminolysis; therefore, several alternative procedures were suggested, carefully evaluated, and critically compared. Solubility problems with ß-alanine and taurine were overcome by the binary solvent system DMF/[EMIM]OAc (1:1, v/v), which was shown to be a promising medium for rapid and efficient homogeneous aminolysis and for the preparation of the corresponding cellulose carbamate derivatives or other compounds that are not accessible by conventional isocyanate chemistry. The zwitterionic cellulose carbamate derivatives presented in this work could be promising chiral cation exchangers for HPLC enantiomer separations.

Silviridoside: A New Triterpene Glycoside from Silene viridiflora with Promising Antioxidant and Enzyme Inhibitory Potential.

A new triterpene glycoside, silviridoside, was isolated from the aerial parts of Silene viridiflora (Caryophyllaceae) using different chromatographic techniques. The structure of silviridoside was comprehensively elucidated as 3-O-ß-D-galacturonopyranosyl-quillaic acid 28-O-ß-D-glucopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→3)]-ß-D-fucopyranosyl ester by one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HR-MS). Silviridoside showed promising antioxidant activity in different antioxidant assays such as 2,2-diphenyl-1-picrylhydrazyl (DPPH) (2.32 mg TE/g), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (1.24 mg TE/g), cupric-reducing antioxidant capacity (CUPRAC) (9.59 mg TE/g), ferric-reducing antioxidant power (FRAP) (5.13 mg TE/g), phosphomolybdenum (PHD) (0.28 mmol TE/g), and metal-chelating (MCA) (6.62 mg EDTA/g) assays. It exhibited a good inhibitory potential on acetylcholinesterase (AChE) (2.52 mg GALAE/g), butyrylcholinesterase (BChE) (7.16 mg GALAE/g), α-amylase (0.19 mmol ACAE/g), α-glucosidase (1.21 mmol ACAE/g), and tyrosinase (38.83 mg KAE/g). An in silico evaluation of the pharmacodynamic, pharmacokinetic, and toxicity properties of silviridoside showed that the new compound exhibited reasonable pharmacodynamic and pharmacokinetic properties without any mutagenic effect, but slight toxicity. Thus, it could be concluded that silviridoside could act as a promising lead drug for pharmaceutical and nutraceutical developments to combat oxidative stress and various disorders, but a future optimization is necessary.

Assembling Native Elementary Cellulose Nanofibrils via a Reversible and Regioselective Surface Functionalization.

Selective surface modification of biobased fibers affords effective individualization and functionalization into nanomaterials, as exemplified by the TEMPO-mediated oxidation. However, such a route leads to changes of the native surface chemistry, affecting interparticle interactions and limiting the development of potential supermaterials. Here we introduce a methodology to extract elementary cellulose fibrils by treatment of biomass with N-succinylimidazole, achieving regioselective surface modification of C6-OH, which can be reverted using mild post-treatments. No polymer degradation, cross-linking, nor changes in crystallinity occur under the mild processing conditions, yielding cellulose nanofibrils bearing carboxyl moieties, which can be removed by saponification. The latter offers a significant opportunity in the reconstitution of the chemical and structural interfaces associated with the native states. Consequently, 3D structuring of native elementary cellulose nanofibrils is made possible with the same supramolecular features as the biosynthesized fibers, which is required to unlock the full potential of cellulose as a sustainable building block.

Comparative hydrolysis analysis of cellulose samples and aspects of its application in conservation science.

Knowledge about the carbohydrate composition of pulp and paper samples is essential for their characterization, further processing, and understanding the properties. In this study, we compare sulfuric acid hydrolysis and acidic methanolysis, followed by GC-MS analysis of the corresponding products, by means of 42 cellulose and polysaccharide samples. Results are discussed and compared to solid-state NMR (crystallinity) and gel permeation chromatography (weight-averaged molecular mass) data. The use of the hydrolysis methods in the context of cellulose conservation science is evaluated, using e-beam treated and artificially aged cellulose samples. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10570-021-04048-6.

Polysaccharide- and ß-Cyclodextrin-Based Chiral Selectors for Enantiomer Resolution: Recent Developments and Applications.

Polysaccharides, oligosaccharides, and their derivatives, particularly of amylose, cellulose, chitosan, and ß-cyclodextrin, are well-known chiral selectors (CSs) of chiral stationary phases (CSPs) in chromatography, because they can separate a wide range of enantiomers. Typically, such CSPs are prepared by physically coating, or chemically immobilizing the polysaccharide and ß-cyclodextrin derivatives onto inert silica gel carriers as chromatographic support. Over the past few years, new chiral selectors have been introduced, and progressive methods to prepare CSPs have been exploited. Also, chiral recognition mechanisms, which play a crucial role in the investigation of chiral separations, have been better elucidated. Further insights into the broad functional performance of commercially available chiral column materials and/or the respective newly developed chiral phase materials on enantiomeric separation (ES) have been gained. This review summarizes the recent developments in CSs, CSP preparation, chiral recognition mechanisms, and enantiomeric separation methods, based on polysaccharides and ß-cyclodextrins as CSs, with a focus on the years 2019-2020 of this rapidly developing field.

Lignin Quantification of Papyri by TGA-Not a Good Idea.

Papyri belong to the oldest writing grounds in history. Their conservation is of the highest importance in preserving our cultural heritage, which is best achieved based on an extensive knowledge of the materials' constituents to choose a tailored conservation approach. Thermogravimetric Analysis (TGA) has been widely employed to quantify cellulose and lignin in papyrus sheets, yielding reported lignin contents of 25% to 40%. In this work, the TGA method conventionally used for papyrus samples was repeated and compared to other lignin determination approaches (Klason-lignin and acetyl bromide-soluble lignin). TGA can lead to a large overestimation of the lignin content of commercial papyrus sheets (~27%) compared to the other methods (~5%). A similar overestimation of the lignin content was found for the pith and rind of the native papyrus plant. We concluded that the TGA method should, therefore, not be used for lignin quantification.

Luteapyrone, a Novel Æ´-Pyrone Isolated from the Filamentous Fungus Metapochonia lutea.

In the process of screening for new bioactive microbial metabolites we found a novel Æ´-pyrone derivative for which we propose the trivial name luteapyrone, in a recently described microscopic filamentous fungus, Metapochonia lutea BiMM-F96/DF4. The compound was isolated from the culture extract of the fungus grown on modified yeast extract sucrose medium by means of flash chromatography followed by preparative HPLC. The chemical structure was elucidated by NMR and LC-MS. The new compound was found to be non-cytotoxic against three mammalian cell lines (HEK 263, KB-3.1 and Caco-2). Similarly, no antimicrobial activity was observed in tested microorganisms (gram positive and negative bacteria, yeast and fungi).

A Direct Silanization Protocol for Dialdehyde Cellulose.

Cellulose derivatives have many potential applications in the field of biomaterials and composites, in addition to several ways of modification leading to them. Silanization in aqueous media is one of the most promising routes to create multipurpose and organic-inorganic hybrid materials. Silanization has been widely used for cellulosic and nano-structured celluloses, but was a problem so far if to be applied to the common cellulose derivative "dialdehyde cellulose" (DAC), i.e., highly periodate-oxidized celluloses. In this work, a straightforward silanization protocol for dialdehyde cellulose is proposed, which can be readily modified with (3-aminopropyl)triethoxysilane. After thermal treatment and freeze-drying, the resulting product showed condensation and cross-linking, which was studied with infrared spectroscopy and 13C and 29Si solid-state nuclear magnetic resonance (NMR) spectroscopy. The cross-linking involves both links of the hydroxyl group of the oxidized cellulose with the silanol groups (Si-O-C) and imine-type bonds between the amino group and keto functions of the DAC (-HC=N-). The modification was achieved in aqueous medium under mild reaction conditions. Different treatments cause different levels of hydrolysis of the organosilane compound, which resulted in diverse condensed silica networks in the modified dialdehyde cellulose structure.

Porous Silk Fibroin/Cellulose Hydrogels for Bone Tissue Engineering via a Novel Combined Process Based on Sequential Regeneration and Porogen Leaching.

Scaffolds used for bone tissue engineering need to have a variety of features to accommodate bone cells. The scaffold should mimic natural bone, it should have appropriate mechanical strength, support cell differentiation to the osteogenic lineage, and offer adequate porosity to allow vascularization and bone in-growth. In this work, we aim at developing a new process to fabricate such materials by creating a porous composite material made of silk fibroin and cellulose as a suitable scaffold of bone tissue engineering. Silk fibroin and cellulose are both dissolved together in N,N-dimethylacetamide/LiCl and molded to a porous structure using NaCl powder. The hydrogels are prepared by a sequential regeneration process: cellulose is solidified by water vapor treatment, while the remaining silk fibroin in the hydrogel is insolubilized by methanol, which leads to a cellulose framework structure embedded in a silk fibroin matrix. Finally, the hydrogels are soaked in water to dissolve the NaCl for making a porous structure. The cellulose composition results in improving the mechanical properties for the hydrogels in comparison to the silk fibroin control material. The pore size and porosity are estimated at around 350 µm and 70%, respectively. The hydrogels support the differentiation of MC3T3 cells to osteoblasts and are expected to be a good scaffold for bone tissue engineering.

Aerogels from Cellulose Phosphates of Low Degree of Substitution: A TBAF·H2O/DMSO Based Approach.

Biopolymer aerogels of appropriate open-porous morphology, nanotopology, surface chemistry, and mechanical properties can be promising cell scaffolding materials. Here, we report a facile approach towards the preparation of cellulose phosphate aerogels from two types of cellulosic source materials. Since high degrees of phosphorylation would afford water-soluble products inappropriate for cell scaffolding, products of low DSP (ca. 0.2) were prepared by a heterogeneous approach. Aiming at both i) full preservation of chemical integrity of cellulose during dissolution and ii) utilization of specific phase separation mechanisms upon coagulation of cellulose, TBAF·H2O/DMSO was employed as a non-derivatizing solvent. Sequential dissolution of cellulose phosphates, casting, coagulation, solvent exchange, and scCO2 drying afforded lightweight, nano-porous aerogels. Compared to their non-derivatized counterparts, cellulose phosphate aerogels are less sensitive towards shrinking during solvent exchange. This is presumably due to electrostatic repulsion and translates into faster scCO2 drying. The low DSP values have no negative impact on pore size distribution, specific surface (SBET ≤ 310 m2 g-1), porosity (Π 95.5-97 vol.%), or stiffness (Eρ ≤ 211 MPa cm3 g-1). Considering the sterilization capabilities of scCO2, existing templating opportunities to afford dual-porous scaffolds and the good hemocompatibility of phosphorylated cellulose, TBAF·H2O/DMSO can be regarded a promising solvent system for the manufacture of cell scaffolding materials.

How Alkaline Solvents in Viscosity Measurements Affect Data for Oxidatively Damaged Celluloses: Cupri-Ethylenediamine.

Although efficient and inexpensive, conventional viscometry to determine the average degree of polymerization (DP) of cellulose may mislead the final DP because cellulose degradation occurs in the used solvents, which consist of alkaline amino complexes of transition metals, such as cupri-ethylenediamine (CED). For oxidatively damaged pulps or celluloses, viscosity-DP determinations may be more inaccurate because alkali-induced ß-elimination reactions render such oxidized celluloses even more vulnerable. Despite the risk identified in many studies, a systematic investigation of the parameters affecting the viscosity-DP assessed by reliable analytics is still required. Here, a new approach evaluating the effects of CED on oxidized cellulosics was used (i.e., immediate pulp regeneration after dissolution in CED). In-depth molecular feature characterization (e.g., absolute molar masses and oxidized groups' profiling related to molecular weight distribution) by gel permeation chromatography coupled with fluorescence and multiangle laser light scattering clarified the behavior of oxidized celluloses and the influencing parameters upon dissolution in CED.

Fast Approach to the Hydrophobization of Bacterial Cellulose via the Direct Polymerization of Ethyl 2-Cyanoacrylate.

Bacterial cellulose (BC) has a broad range of applications in biomedical fields and cosmetics. Applied as wound dressing, BC tends to stick to the sore especially upon drying, and hydrophobization improves its performance in this regard. This article reports a facile and rapid yet a highly efficient approach for BC hydrophobization through direct polymerization of ethyl 2-cyanoacrylate on the BC fibers. The modified material preserves the favorable porous structure of the matrix material while displaying significantly higher hydrophobicity and significantly decreased stickiness to the wound. The BC surface can be modified in 15 min. Overall, this can be considered a ready-to-apply approach for the fabrication of BC wound dressings with enhanced performance. The modification was demonstrated to improve the material's biocompatibility and to introduce antimicrobial activity (immortalized human fibroblast assay).

Potentially Immunogenic Contaminants in Wood-Based and Bacterial Nanocellulose: Assessment of Endotoxin and (1,3)-ß-d-Glucan Levels.

Knowledge gaps in the biosafety data of the nanocellulose (NC) for biomedical use through various routes of administration call for closer look at health and exposure evaluation. This work evaluated the potentially immunogenic contaminants levels, for example, endotoxin and (1,3)-ß-d-glucan, in four representative NCs, that is, wood-based NCs and bacterial cellulose (BC). The hot-water extracts were analyzed with ELISA assays, HPSEC-MALLS, GC, and NMR analysis. Varying levels of endotoxin and (1,3)-ß-d-glucan contaminats were found in these widely used NCs. Although the ß-(1,3)-d-glucan was not detected from the NMR spectra due to the small extract samples amount (2-7 mg), the anomerics and highly diastereotopic 6-CH2 signals may suggest the presence of ß-(1,4)-linkages with ß-(1,6) branching in the polysaccharides of NCs' hot-water extracts, which were otherwise not detectable in the enzymatic assay. In all, the article highlights the importance of monitoring various water-soluble potentially immunogenic contaminants in NC for biomedical use.

Self-Standing Nanocellulose Janus-Type Films with Aldehyde and Carboxyl Functionalities.

Nanocellulose-based self-standing films are becoming a substrate for flexible electronics, diagnostics, and sensors. Strength and surface chemistry are vital variables for these film-based endeavors, the former is one of the assets of nanocellulose. To contribute to the latter, nanocellulose films are tuned with a side-specific functionalization, having an aldehyde and a carboxyl side. The functionalities were obtained combining premodification of the film components by periodate oxidation with ozone post-treatment. Periodate oxidation of cellulose nanocrystals results in film components that interact through intra- and intermolecular hemiacetals and lead to films with an elastic modulus of 11 GPa. The ozone treatment of one film side induces conversion of the aldehyde into carboxyl functionalities. The ozone treatment on individual crystals was largely destructive. Remarkably, such degradation is not observed for the self-standing film, and the film strength at break is preserved. Preserving a physically intact film despite ozone treatment is a credit to using the dry film structure held together by interparticle covalent linkages. Additionally, gas-phase post-treatment avoids disintegration that could result from immersion into solvents. The crystalline cellulose "Janus" film is suggested as an interfacial component in biomaterial engineering, separation technology, or in layered composite materials for tunable affinity between the layers.