Structure-properties correlations in low-methylated pectin hydrogels and aerogels crosslinked by divalent ions.

In this paper, structure-properties relationship between ionically crosslinked pectin hydrogels and aerogels is drawn, by focusing the study on the small amount of added cationic crosslinkers. Through this strategy and by coupling results from rheology and nanostructure of the gels provided by small-angle X-ray scattering, the early stages of the formation of ionic crosslinking junction zones are observed. Furthermore, as a major predictor of the samples' ability to resist linear shrinkage upon solvent exchange and supercritical drying processes, the gel-state (and thus rheological properties) emerges as a key element.

'Click' hydrogels from renewable polysaccharide resources: Bioorthogonal chemistry for the preparation of alginate, cellulose and other plant-based networks with biomedical applications.

Click chemistry refers to a class of highly selective reactions that occur in one pot, are not disturbed by water or oxygen, proceed quickly to high yield and generate only inoffensive byproducts. Since its first definition by Barry Sharpless in 2001, click chemistry has increasingly been used for the preparation of hydrogels, which are water-swollen polymer networks with numerous biomedical applications. Polysaccharides, which can be obtained from renewable resources including plants, have drawn growing attention for use in hydrogels due to the recent focus on the development of a sustainable society and the reduction of the environmental impact of the chemical industry.

From Cellulose Solutions to Aerogels and Xerogels: Controlling Properties for Drug Delivery.

A cheap and easy-to-recycle solvent, namely, aqueous NaOH with no additives, was used to dissolve cellulose and make cross-linker-free materials with varying porosity, testing them as drug delivery devices. Cellulose solutions were gelled, coagulated in a nonsolvent (water, ethanol), and dried either using supercritical CO (aerogels) or low-vacuum evaporation (named "xerogels"). Aerogels had densities of around 0.

Tuning bio-aerogel properties. Part 3: Exploring silica-pectin composite aerogels for drug delivery.

The release of the model drug theophylline from silica-pectin aerogels was investigated. The composite aerogels were prepared via impregnation of pectin alcogels with silica sol, followed by in situ silica gelation and drying with supercritical CO. The structural and physico-chemical properties of the aerogels were tuned via the preparation conditions (type of silica sol, calcium crosslinking of pectin or not).

Creating and exploring carboxymethyl cellulose aerogels as drug delivery devices.

Carboxymethyl cellulose (CMC) is a well-known cellulose derivative used in biomedical applications due to its biocompatibility and biodegradability. In this work, novel porous CMC materials, aerogels, were prepared and tested as a drug delivery device. CMC aerogels were made from CMC solutions, followed by non-solvent induced phase separation and drying with supercritical CO.

Montmorillonite Exfoliation in LLDPE and Factors Affecting Its Orientation: From Monolayer to Multi-Nano-Layer Polymer Films.

The motivations of the present work are to investigate the exfoliation of montmorillonite within a linear low-density polyethylene matrix and to control its orientation during the cast extrusion process. The first part is focused on the exfoliation of the montmorillonite through the melt extrusion process. The accuracy and relevance of each method used to determine the exfoliation state of montmorillonite have been examined, thanks to X-ray diffraction, transmission electronic microscopy, and rheology.

Roadmap on multifunctional materials for drug delivery.

This Roadmap on drug delivery aims to cover some of the most recent advances in the field of materials for drug delivery systems (DDSs) and emphasizes the role that multifunctional materials play in advancing the performance of modern DDS in the context of the most current challenges presented. The Roadmap is comprised of multiple sections, each of which introduces the status of the field, the current and future challenges faced, and a perspective of the required advances necessary for biomaterial science to tackle these challenges. It is our hope that this collective vision will contribute to the initiation of conversation and collaboration across all areas of multifunctional materials for DDSs.

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.

Advanced Functional Polymers for Unmet Medical Challenges.

A significant part of medicine relies on biomaterials, which are designed to interact with biological tissues for therapeutic or diagnostic purposes. A number of major trends can be distinguished in the multidisciplinary field of biomaterials science, including the precise synthesis of biomaterial building blocks, elucidation of biomaterial processing-structure-property correlations, as well as clarification of the interactions between living tissues and biomaterials. Moreover, advances in biofabrication facilitate the development of tailored implants with improved functionality, whereas recent achievements in medical imaging allow for a detailed evaluation of the performance and spatiotemporal behavior of medical devices and nanomedicine formulations.

Release Kinetics of Dexamethasone Phosphate from Porous Chitosan: Comparison of Aerogels and Cryogels.

Porous chitosan materials as potential wound dressings were prepared via dissolution of chitosan, nonsolvent-induced phase separation in NaOH-water, formation of a hydrogel, and either freeze-drying or supercritical CO drying, leading to "cryogels" and "aerogels", respectively. The hydrophilic drug dexamethasone sodium phosphate was loaded by impregnation of chitosan hydrogel, and the release from cryogel or aerogel was monitored at two pH values relevant for wound healing. The goal was to compare the drug-loading efficiency and release behavior from aerogels and cryogels as a function of the drying method, the materials' physicochemical properties (density, morphology), and the pH of the release medium.

Thermo-Hydro-Glycol Ageing of Polyamide 6,6: Microstructure-Properties Relationships.

The microstructural evolutions occurring during the thermo-hydro-glycol ageing of an injection molded PA66 were studied. They were correlated to the evolutions of its mechanical properties. The aged samples were immersed in an antifreeze fluid-mainly composed of water and ethylene glycol-at varying times and temperatures.

Tuning bio-aerogel properties for controlling drug delivery. Part 2: Cellulose-pectin composite aerogels.

The release of the model drug theophylline from cellulose-pectin composite aerogels was investigated. Cellulose and pectin formed an interpenetrated network, and the goal was to study and understand the influence of each component and its solubility in simulated gastric and intestinal fluids on the kinetics of release. Cellulose was dissolved, coagulated in water, followed by impregnation with pectin solution, crosslinking of pectin with calcium (in some cases this step was omitted), solvent exchange and supercritical CO drying.

Crosslinker-Free Hyaluronic Acid Aerogels.

Aerogels based on hyaluronic acid (HA) were prepared without any chemical crosslinking by polymer dissolution, network formation via nonsolvent-induced phase separation, and supercritical CO drying. The influence of solution pH, concentration of HA, and type of nonsolvent on network volume shrinkage, aerogel density, morphology, and specific surface area was investigated. A marked dependence of aerogel properties on solution pH was observed: aerogels with the highest specific surface area, 510 m/g, and the lowest density, 0.

Tuning the properties of porous chitosan: Aerogels and cryogels.

Highly porous chitosan-based materials were prepared via dissolution, non-solvent induced phase separation and drying using different methods. The goal was to tune the morphology and properties of chitosan porous materials by varying process parameters. Chitosan concentration, concentration of sodium hydroxide in the coagulation bath and aging time were varied.

Tuning bio-aerogel properties for controlling theophylline delivery. Part 1: Pectin aerogels.

A comprehensive study of release kinetics of a hydrophilic drug from bio-aerogels based on pectin was performed. Pectin aerogels were made by polymer dissolution, gelation (in some cases this step was omitted), solvent exchange and drying with supercritical CO. Theophylline was loaded and its release was studied in the simulated gastric fluid during 1 h followed by the release in the simulated intestinal fluid.

Polysaccharide-based aerogels for thermal insulation and superinsulation: An overview.

To reduce energy losses due to the insufficient thermal insulation is one of the current "hot" topics. Various commercial porous materials are used with the best conductivity around 0.03-0.

Tailoring the morphology and properties of starch aerogels and cryogels via starch source and process parameter.

Porous starch materials with various morphology and properties were made via starch dissolution, retrogradation and drying either with supercritical CO ("aerogels") or lyophilisation ("cryogels"). Their properties were correlated with the rheological response of retrograded starch gels and crystallinity of aerogels and cryogels. All starch cryogels possess very low density (0.

Biorefinery Approach for Aerogels.

According to the International Energy Agency, biorefinery is "the sustainable processing of biomass into a spectrum of marketable bio-based products (chemicals, materials) and bioenergy (fuels, power, heat)". In this review, we survey how the biorefinery approach can be applied to highly porous and nanostructured materials, namely aerogels. Historically, aerogels were first developed using inorganic matter.

Enzymically attaching oligosaccharide-linked 'cargoes' to cellulose and other commercial polysaccharides via stable covalent bonds.

The Equisetum enzyme hetero-trans-β-glucanase (HTG) covalently grafts native plant cellulose (donor-substrate) to xyloglucan (acceptor-substrate), potentially offering a novel 'green' method of cellulose functionalisation. However, the range of cellulosic and non-cellulosic donor substrates that can be utilised by HTG is unknown, limiting our insight into its biotechnological potential. Here we show that HTG binds all celluloses tested (papers, tissues, hydrogels, bacterial cellulose) to radioactively- or fluorescently-labelled xyloglucan-heptasaccharide (XXXGol; acceptor-substrate).

Exploring Large Ductility in Cellulose Nanopaper Combining High Toughness and Strength.

Cellulose nanopaper is a strong lightweight material made from renewable resources with a wide range of potential applications, from membranes to electronic displays. Most studies on nanopaper target high mechanical strength, which compromises ductility and toughness. Herein, we demonstrate the fabrication of highly ductile and tough cellulose nanopaper via mechanical fibrillation of hemicellulose-rich wood fibers and dispersion of the obtained cellulose nanofibrils (CNFs) in an ionic liquid (IL)-water mixture.

Unidirectional All-Cellulose Composites from Flax via Controlled Impregnation with Ionic Liquid.

Mechanically strong all-cellulose composites are very attractive in the terms of fully bio-based and bio-degradable materials. Unidirectional flax-based all-cellulose composites are prepared via facile room-temperature impregnation with an ionic liquid, 1-ethyl-3-methyl imidazolium acetate. To determine the optimal processing conditions, the kinetics of flax dissolution in this solvent is first studied using optical microscopy.

Bismaleimide bridged silsesquioxane aerogels with excellent heat resistance: effect of sol-gel solvent polarity.

Due to the poor heat-resistance and intrinsic weakness of the bridging moieties in aerogel matrixes, it remains greatly challenging to fabricate highly thermostable and toughened silsesquioxane aerogels. By utilizing bismaleimide as the bridging part and optimizing the solvent polarity, lightweight (ρ < 0.09 g cm-3), compressible (80% strain) and superhydrophobic (CA ≈ 150°) bismaleimide bridged silsesquioxane aerogels (BMIT-BSAs) are constructed.

Cellulose Aerogel Microparticles via Emulsion-Coagulation Technique.

Cellulose aerogel microparticles were made via emulsification/nonsolvent induced phase separation/drying with supercritical CO. Cellulose was dissolved in NaOH-based solvent with and without additives in order to control solution gelation. Two emulsions, cellulose solution/oil and cellulose nonsolvent/oil, were mixed to start nonsolvent induced phase separation (or coagulation) of cellulose inside each cellulose droplet leading to the formation of so-called microgels.

Gelation of cellulose-NaOH solutions in the presence of cellulose fibers.

It is well known that when cellulose is dissolved in aqueous NaOH-based solvent, solutions are gelling with increasing time and temperature. The goal of this work was to understand if the presence of non-dissolved cellulose fibers influences gelation behavior of the whole system. One of the motivations is to control gelation when making all-cellulose composites with short fibers dispersed in cellulose-NaOH-water solutions.