Nanofibrillar networks enable universal assembly of superstructured particle constructs

Building respirable powder architectures: utilizing polysaccharides for precise control of particle morphology for enhanced pulmonary drug delivery

INTRODUCTION

Dry powder inhaler (DPI) formulations are gaining attention as universal formulations with applications in a diverse range of drug formulations. The practical application of DPIs to pulmonary drugs requires enhancing their delivery efficiency to the target sites for various treatment modalities. Previous reviews have not explored the relation between particle morphology and delivery to different pulmonary regions. This review introduces new approaches to improve targeted DPI delivery using novel particle design such as supraparticles and metal-organic frameworks based on cyclodextrin.

AREAS COVERED

This review focuses on the design of DPI formulations using polysaccharides, promising excipients not yet approved by regulatory agencies. These excipients can be used to design various particle morphologies by controlling their physicochemical properties and manufacturing methods.

EXPERT OPINION

Challenges associated with DPI formulations include poor access to the lungs and low delivery efficiency to target sites in the lung. The restricted applicability of typical excipients contributes to their limited use. However, new formulations based on polysaccharides are expected to establish a technological foundation for the development of DPIs capable of delivering modalities specific to different lung target sites, thereby enhancing drug delivery.

Multiphase Under-Liquid Biofabrication With Living Soft Matter: A Route to Customize Functional Architectures With Microbial Nanocellulose

The growth of aerobic microbes at air-water interfaces typically leads to biofilm formation. Herein, a fermentative alternative that relies on oil-water interfaces to support bacterial activity and aerotaxis is introduced. The process uses under-liquid biofabrication by structuring bacterial nanocellulose (BNC) to achieve tailorable architectures. Cellulose productivity in static conditions is first evaluated using sets of oil homologues, classified in order of polarity. The oils are shown for their ability to sustain bacterial growth and BNC production according to air transfer and solubilization, both of which impact the physiochemical properties of the produced biofilms. The latter are investigated in terms of their morphological (fibril size and network density), structural (crystallinity) and physical-mechanical (surface area and strength) features. The introduced under-liquid biofabrication is demonstrated for the generation of BNC-based macroscale architectures and compartmentalized soft matter. This can be accomplished following three different routes, namely, 3D under-liquid networking (multi-layer hydrogels/composites), emulsion templating (capsules, emulgels, porous materials), and anisotropic layering (Janus membranes). Overall, the proposed platform combines living matter and multi-phase systems as a robust option for material development with relevance in biomedicine, soft robotics, and bioremediation, among others.

Magnetic superhydrophobic cellulose nanofibril based aerogel with rope-ladder like structure incorporating both superelasticity and excellent oil absorption

Achieving an equilibrium between exceptional oil absorption and remarkable elasticity has emerged as a formidable challenge for magnetic porous materials designed for oil absorption. Here, we propose an original, magnetic and superhydrophobic cellulose nanofibril (CNF) based aerogel system with a rope-ladder like skeleton by to greatly improve the issue. Within this system, CNF as the skeleton was combined with multiwalled carbon nanotubes (MWCNT)@Fe3O4 as the magnetic and enhanced component, both methyltrimethoxysilane (MTMS) and acetonitrile-extracted lignin (AEL) as the soft-hard associating constituents. The resultant CNF based aerogel shows a rope-ladder like pore structure to contribute to high elasticity and excellent oil absorption (28.34-61.09 g/g for various oils and organic solvents) under the synergistic effect of Fe3O4@MWCNT, AEL and MTMS, as well as good specific surface area (27.97 m2/g), low density (26.4 mg/cm3). Notably, despite the introduced considerable proportion (0.5 times of mass-CNF) of Fe3O4@MWCNT, the aerogel retained an impressive compression-decompression rate (88%) and the oil absorption efficiency of above 87% for various oils due to the soft-hard associating structure supported by both MTMS and AEL. This study provides a prospective strategy to balance between high elasticity and excellent oil absorption of CNF based aerogel doping inorganic particles.

Benchmarking the Humidity-Dependent Mechanical Response of (Nano)fibrillated Cellulose and Dissolved Polysaccharides as Sustainable Sand Amendments

Soil quality is one of the main limiting factor in the development of the food sector in arid areas, mainly due to its poor mechanics and lack of water retention. Soil's organic carbon is nearly absent in arid soils, though it is important for water and nutrient transport, to soil mechanics, to prevent erosion, and as a long-term carbon sink. In this study, we evaluate the potential benefits that are brought to inert sand by the incorporation of a range of, mainly, cellulosic networks in their polymeric or structured (fiber) forms, analogously to those found in healthy soils. We explore the impact of a wide range of nonfood polysaccharide-based amendments, including pulp fibers, nanocellulose, cellulose derivatives, and other readily available polysaccharide structures derived from arthropods (chitosan) or fruit peels (pectin) residues. A practical methodology is presented to form sand-polymer composites, which are evaluated for their soil mechanics as a function of humidity and the dynamics of their response to water. The mechanics are correlated to the network of polymers formed within the pores of the sandy soil, as observed by electron microscopy. The response to water is correlated to both the features of the network and the individual polysaccharides' physicochemical features. We expect this work to provide a rapid and reproducible methodology to benchmark sustainable organic amendments for arid soils.

Recent advances and biomedical application of 3D printed nanocellulose-based adhesive hydrogels: A review

Nanocellulose-based tissue adhesives show promise for achieving rapid hemostasis and effective wound healing. Conventional methods, such as sutures and staples, have limitations, prompting the exploration of bioadhesives for direct wound adhesion and minimal tissue damage. Nanocellulose, a hydrolysis product of cellulose, exhibits superior biocompatibility and multifunctional properties, gaining interest as a base material for bioadhesive development. This study explores the potential of nanocellulose-based adhesives for hemostasis and wound healing using 3D printing techniques. Nanocellulose enables the creation of biodegradable adhesives with minimal adverse effects and opens avenues for advanced wound healing and complex tissue regeneration, such as skin, blood vessels, lungs, cartilage, and muscle. This study reviews recent trends in various nanocellulose-based 3D printed hydrogel patches for tissue engineering applications. The review also introduces various types of nanocellulose and their synthesis, surface modification, and bioadhesive fabrication techniques via 3D printing for smart wound healing.

Multiscale Design for Robust, Thermal Insulating, and Flame Self-Extinguishing Cellulose Foam

Cellulose foams are in high demand in an era of prioritizing environmental consciousness. Yet, transferring the exceptional mechanical properties of cellulose fibers into a cellulose network remains a significant challenge. To address this challenge, an innovative multiscale design is developed for producing cellulose foam with exceptional network integrity. Specifically, this design relies on a combination of physical cross-linking of the microfibrillated cellulose (MFC) networks by cellulose nanofibril (CNF) and aluminum ion (Al3+), as well as self-densification of the cellulose induced by ice-crystal templating, physical cross-linking, solvent exchange, and evaporation. The resultant cellulose foam demonstrates a low density of 40.7 mg cm-3, a high porosity of 97.3%, and a robust network with high compressive modulus of 1211.5 ± 60.6 kPa and energy absorption of 77.8 ± 1.9 kJ m-3. The introduction of CNF network and Al3+ cross-linking into foam also confers excellent wet stability and flame self-extinguish ability. Furthermore, the foam can be easily biodegraded in natural environments , re-entering the ecosystem's carbon cycle. This strategy yields a cellulose foam with a robust network and outstanding environmental durability, opening new possibilities for the advancement of high-performance foam materials.

A Versatile Shaping Method of Very-High Loading Porous Solids Paper Adsorbent Composites

Owing to their high porosity and tunability, porous solids such as metal-organic frameworks (MOFs), zeolites, or activated carbons (ACs) are of great interest in the fields of air purification, gas separation, and catalysis, among others. Nonetheless, these materials are usually synthetized as powders and need to be shaped in a more practical way that does not modify their intrinsic property (i.e., porosity). Elaborating porous, freestanding and flexible sheets is a relevant shaping strategy. However, when high loadings (>70 wt.%) are achieved the mechanical properties are challenged. A new straightforward and green method involving the combination softwood bleached kraft pulp fibers (S) and nano-fibrillated cellulose (NFC) is reported, where S provides flexibility while NFC acts as a micro-structuring and mechanical reinforcement agent to form high loadings porous solids paper sheets (>70 wt.%). The composite has unobstructed porosity and good mechanical strength. The sheets prepared with various fillers (MOFs, ACs, and zeolites) can be rolled, handled, and adapted to different uses, such as air purification. As an example of potential application, a MOF paper composite has been considered for the capture of polar volatile organic compounds exhibiting better performance than beads and granules.

Sulfated endospermic nanocellulose crystals prevent the transmission of SARS-CoV-2 and HIV-1

Biomaterials with antimicrobial activity are gaining attention due to their biodegradability and efficacy in interacting with a wide range of microorganisms. A new cellulose nano-biomaterial, endospermic nanocellulose crystals (ENC) obtained from parenchymal tissue of ivory nut endosperm, has a natural capacity as a universal binder. This feature is enhanced when it is chemically functionalized, and can be exploited in the fight against microbes. We tested the ability of sulfated ENC in aqueous suspension to encapsulate viruses through a crosslinking reaction mediated by cations. 0.25% w/v ENC suspensions efficiently encapsulated spike (S) protein, preventing its interaction with ACE2 receptor. ENC was further able to encapsulate SARS-CoV-2 pseudoviruses and prevent infection of 293T-hsACE2 cells. ENC also suppressed infection of MT-4 cells with HIV-1LAI.04. This antiviral activity of sulfated ENC is due to the irreversible interaction of ENC with viral particles mediated by crosslinking, as antiviral activity was less effective in the absence of cations. Additionally, ENC was used as a matrix to immobilize recombinant ACE2 receptors and anti-S IgG, creating molecular lures that efficiently inhibited SARS-CoV-2 infections in vitro. These results show that sulfated ENC from ivory nuts can be used as an efficient antiviral material.

Negative magnetostrictive paper formed by dispersing CoFe2O4 particles in cellulose nanofibrils

Polymers are often combined with magnetostrictive materials to enhance their toughness. This study reports a cellulose nanofibril (CNF)-based composite paper containing dispersed CoFe₂O₄ particles (CNF-CoFe₂O₄). Besides imparting magnetization and magnetostriction, the incorporation of CoFe₂O₄ particles decreased the ultimate tensile strength and increased the fracture elongation of the CNF-CoFe₂O₄ composite paper. CNF was responsible for the tensile properties of CNF-CoFe₂O₄ composite paper. Consequently, the magnetic and magnetostrictive properties and tensile properties of CNF-CoFe₂O₄ composite paper can be controlled by changing the mixture ratio of CNF and CoFe₂O₄ particles.

The Influence of Cellulose Nanocrystal Characteristics on Regenerative Silk Composite Fiber Properties

Cellulose nanocrystals (CNCs), obtained from natural resources, possess great potential as a bioderived reinforcement for natural-fiber-reinforced composites (NFRPs) due to their superior crystallinity and high aspect ratio. To elucidate the specific parameters of CNCs that significantly affect their mechanical performance, various CNCs were investigated to fabricate high-performance nanocomposite fibers together with regenerated silk fibroin (RSF). We confirmed that the high aspect ratio (~9) of the CNCs was the critical factor to increase the tensile strength and stiffness rather than the crystallinity. At a 1 vol% of CNCs, the strength and stiffness reached ~300 MPa and 10.5 GPa, respectively, which was attributed not only to a stable dispersion but also to alignment. This approach has the potential to evaluate the parameters of natural reinforcement and may also be useful in constructing high-performance NFRPs.

Cellulose: A Review of Water Interactions, Applications in Composites, and Water Treatment

Cellulose is known to interact well with water, but is insoluble in it. Many polysaccharides such as cellulose are known to have significant hydrogen bond networks joining the molecular chains, and yet they are recalcitrant to aqueous solvents. This review charts the interaction of cellulose with water but with emphasis on the formation of both natural and synthetic fiber composites. Covering studies concerning the interaction of water with wood, the biosynthesis of cellulose in the cell wall, to its dispersion in aqueous suspensions and ultimately in water filtration and fiber-based composite materials this review explores water-cellulose interactions and how they can be exploited for synthetic and natural composites. The suggestion that cellulose is amphiphilic is critically reviewed, with relevance to its processing. Building on this, progress made in using various charged and modified forms of nanocellulose to stabilize oil-water emulsions is addressed. The role of water in the aqueous formation of chiral nematic liquid crystals, and subsequently when dried into composite films is covered. The review will also address the use of cellulose as an aid to water filtration as one area where interactions can be used effectively to prosper human life.

Direct CO2 Capture by Alkali-Dissolved Cellulose and Sequestration in Building Materials and Artificial Reef Structures

Current carbon capture and utilization (CCU) technologies require high energy input and costly catalysts. Here, an effective pathway is offered that addresses climate action by atmospheric CO₂ sequestration. Industrially relevant highly reactive alkali cellulose solutions are used as CO₂ absorption media. The latter lead to mineralized cellulose materials (MCM) at a tailorable cellulose-to-mineral ratio, forming organic-inorganic viscous systems (viscosity from 10² to 10⁷  mPa s and storage modulus from 10 to 10⁵  Pa). CO₂ absorption and conversion into calcium carbonate and associated minerals translate to maximum absorption of 6.5 gCO₂ g_cellulose ^-1 , tracking inversely with cellulose loading. Cellulose lean gels are easily converted into dry powders, shown as a functional component of ceramic glazes and cementitious composites. Meanwhile, cellulose-rich gels are moldable and extrudable, yielding stone-like structures tested as artificial substrates for coral reef restoration. Life Cycle Assessment (LCA) suggests new CCU opportunities for building materials, as demonstrated in underwater deployment for coral reef ecosystem restoration.

Sulfated endospermic nanocellulose crystals prevent the transmission of SARS-CoV-2 and HIV-1

Biomaterials with antimicrobial activity are gaining attention due to their biodegradability and efficacy in interacting with a wide range of microorganisms. A new cellulose nano-biomaterial, endospermic nanocellulose crystals (ENC) obtained from parenchymal tissue of ivory nut endosperm, has a natural capacity as a universal binder. This feature is enhanced when it is chemically functionalized, and can be exploited in the fight against microbes. We tested the ability of sulfated ENC in aqueous suspension to encapsulate viruses through a crosslinking reaction mediated by cations. 0.25% w/v ENC suspensions efficiently encapsulated spike (S) protein, preventing its interaction with ACE2 receptor. ENC was further able to encapsulate SARS-CoV-2 pseudoviruses and prevent infection of 293T-ACE2 cells. ENC also suppressed infection of MT-4 cells with HIV-1 _LAI.04 . This antiviral activity of sulfated ENC is due to the irreversible interaction of ENC with viral particles mediated by crosslinking, as antiviral activity was less effective in the absence of cations. Additionally, ENC was used as a matrix to immobilize recombinant ACE2 receptors and anti-S IgG, creating molecular lures that efficiently inhibited SARS-CoV-2 infections in vitro . These results show that sulfated ENC from ivory nuts can be used as an efficient antiviral material.

A supraparticle-based biomimetic cascade catalyst for continuous flow reaction

Robust millimeter-sized spherical particles with controlled compositions and microstructures hold promises of important practical applications especially in relation to continuous flow cascade catalysis. However, the efficient fabrication methods for producing such particles remain scare. Here, we demonstrate a liquid marble approach to fabricate robust mm-sized porous supraparticles (SPs) through the bottom-up assembly of silica nanoparticles in the presence of strength additive or surface interactions, without the need for the specific liquid-repellent surfaces used by the existing methods. As the proof of the concept, our method was exemplified by fabricating biomimetic cascade catalysts through assembly of two types of well-defined catalytically active nanoparticles. The obtained SP-based cascade catalysts work well in industrially preferred fixed-bed reactors, exhibiting excellent catalysis efficiency, controlled reaction kinetics, high enantioselectivity (99% ee) and outstanding stability (200~500 h) in the cascades of ketone hydrogenation-kinetic resolution and amine racemization-kinetic resolution. The excellent catalytic performances are attributed to the structural features, reconciling close proximity of different catalytic sites and their sufficient spatial isolation.

Robust millimeter-sized spherical particles with controlled compositions and microstructures hold promises of important practical applications. Here the authors develop a liquid marble method to facilely fabricate robust millimeter-sized supraparticles with controlled microstructures through the bottom-up assembly of silica nanoparticles.

Benchmarking supramolecular adhesive behavior of nanocelluloses, cellulose derivatives and proteins

One of the key steps towards a broader implementation of renewable materials is the development of biodegradable adhesives that can be attained at scale and utilized safely. Recently, cellulose nanocrystals (CNCs) were demonstrated to have remarkable adhesive properties. Herein, we study three classes of naturally synthesized biopolymers as adhesives, namely nanocelluloses (CNFs), cellulose derivatives, and proteins by themselves and when used as additives with CNCs. Among the samples evaluated, the adhesion strength was the highest for bovine serum albumin and hydroxypropyl cellulose (beyond 10 MPa). These were followed by carboxymethylcellulose and CNCs (ca. 5 MPa) and mechanically fibrillated CNFs (ca. 2 MPa), and finally by tempo-oxidized CNFs (0.2 MPa) and lysozyme (1.5 MPa). Remarkably, we find that the anisotropy of adhesion (in plane vs out of plane) falls within a narrow range across the bio-based adhesives studied. Collectively, this study benchmarks bio-based non-covalent adhesives aiming towards their improvement and implementation.

Nanocellulose Removes the Need for Chemical Crosslinking in Tannin-Based Rigid Foams and Enhances Their Strength and Fire Retardancy

Thermal insulation and fire protection are two of the most critical features affecting energy efficiency and safety in built environments. Together with the associated environmental footprint, there is a strong need to consider new insulation materials. Tannin rigid foams have been proposed as viable and sustainable alternatives to expanded polyurethanes, traditionally used in building enveloping. Tannin foams structure result from polymerization with furfuryl alcohol via self-expanding. We further introduce cellulose nanofibrils (CNFs) as a reinforcing agent that eliminates the need for chemical crosslinking during foam formation. CNF forms highly entangled and interconnected nanonetworks, at solid fractions as low as 0.1 wt %, enabling the formation of foams that are ca. 30% stronger and ca. 25% lighter compared to those produced with formaldehyde, currently known as one of the best performers in chemically coupling tannin and furfuryl alcohol. Compared to the those chemically crosslinked, our CNF-reinforced tannin foams display higher thermal degradation temperature (peak shifted upward, by 30-50 °C) and fire resistance (40% decrease in mass loss). Furthermore, we demonstrate partially hydrophobized CNF to tailor the foam microstructure and derived physical-mechanical properties. In sum, green and sustainable foams, stronger, lighter, and more resistant to fire are demonstrated compared to those produced by formaldehyde crosslinking.

Regulating Dendrite-Free Zinc Deposition by Red Phosphorous-Derived Artificial Protective Layer for Zinc Metal Batteries

Rational architecture design of the artificial protective layer on the zinc (Zn) anode surface is a promising strategy to achieve uniform Zn deposition and inhibit the uncontrolled growth of Zn dendrites. Herein, a red phosphorous-derived artificial protective layer combined with a conductive N-doped carbon framework is designed to achieve dendrite-free Zn deposition. The Zn-phosphorus (ZnP) solid solution alloy artificial protective layer is formed during Zn plating. Meanwhile, the dynamic evolution mechanism of the ZnP on the Zn anode is successfully revealed. The concentration gradient of the electrolyte on the electrode surface can be redistributed by this protective layer, thereby achieving a uniform Zn-ion flux. The fabricated Zn symmetrical battery delivers a dendrite-free plating/stripping for 1100 h at the current density of 2.0 mA cm-2 . Furthermore, aqueous Zn//MnO2 full cell exhibits a reversible capacity of 200 mAh g-1 after 350 cycles at 1.0 A g-1 . This study suggests an effective solution for the suppression of Zn dendrites in Zn metal batteries, which is expected to provide a deep insight into the design of high-performance rechargeable aqueous Zn-ion batteries.

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.

Superstable Wet Foams and Lightweight Solid Composites from Nanocellulose and Hydrophobic Particles

Colloids are suitable options to replace surfactants in the formation of multiphase systems while simultaneously achieving performance benefits. We introduce synergetic combination of colloids for the interfacial stabilization of complex fluids that can be converted into lightweight materials. The strong interactions between high aspect ratio and hydrophilic fibrillated cellulose (CNF) with low aspect ratio hydrophobic particles afford superstable Pickering foams. The foams were used as a scaffolding precursor of porous, solid materials. Compared to foams stabilized by the hydrophobic particles alone, the introduction of CNF significantly increased the foamability (by up to 350%) and foam lifetime. These effects are ascribed to the fibrillar network formed by CNF. The CNF solid fraction regulated the interparticle interactions in the wet foam, delaying or preventing drainage, coarsening, and bubble coalescence. Upon drying, such a complex fluid was transformed into lightweight and strong architectures, which displayed properties that depended on the surface energy of the CNF precursor. We show that CNF combined with hydrophobic particles universally forms superstable complex fluids that can be used as a processing route to synthesize strong composites and lightweight structures.

Deconstruction and Reassembly of Renewable Polymers and Biocolloids into Next Generation Structured Materials

This review considers the most recent developments in supramolecular and supraparticle structures obtained from natural, renewable biopolymers as well as their disassembly and reassembly into engineered materials. We introduce the main interactions that control bottom-up synthesis and top-down design at different length scales, highlighting the promise of natural biopolymers and associated building blocks. The latter have become main actors in the recent surge of the scientific and patent literature related to the subject. Such developments make prominent use of multicomponent and hierarchical polymeric assemblies and structures that contain polysaccharides (cellulose, chitin, and others), polyphenols (lignins, tannins), and proteins (soy, whey, silk, and other proteins). We offer a comprehensive discussion about the interactions that exist in their native architectures (including multicomponent and composite forms), the chemical modification of polysaccharides and their deconstruction into high axial aspect nanofibers and nanorods. We reflect on the availability and suitability of the latter types of building blocks to enable superstructures and colloidal associations. As far as processing, we describe the most relevant transitions, from the solution to the gel state and the routes that can be used to arrive to consolidated materials with prescribed properties. We highlight the implementation of supramolecular and superstructures in different technological fields that exploit the synergies exhibited by renewable polymers and biocolloids integrated in structured materials.

The Food-Materials Nexus: Next Generation Bioplastics and Advanced Materials from Agri-Food Residues

The most recent strategies available for upcycling agri-food losses and waste (FLW) into functional bioplastics and advanced materials are reviewed and the valorization of food residuals are put in perspective, adding to the water-food-energy nexus. Low value or underutilized biomass, biocolloids, water-soluble biopolymers, polymerizable monomers, and nutrients are introduced as feasible building blocks for biotechnological conversion into bioplastics. The latter are demonstrated for their incorporation in multifunctional packaging, biomedical devices, sensors, actuators, and energy conversion and storage devices, contributing to the valorization efforts within the future circular bioeconomy. Strategies are introduced to effectively synthesize, deconstruct and reassemble or engineer FLW-derived monomeric, polymeric, and colloidal building blocks. Multifunctional bioplastics are introduced considering the structural, chemical, physical as well as the accessibility of FLW precursors. Processing techniques are analyzed within the fields of polymer chemistry and physics. The prospects of FLW streams and biomass surplus, considering their availability, interactions with water and thermal stability, are critically discussed in a near-future scenario that is expected to lead to next-generation bioplastics and advanced materials.

Regioselective and water-assisted surface esterification of never-dried cellulose: nanofibers with adjustable surface energy

A new regioselective route is introduced for surface modification of biological colloids in the presence of water. Taking the case of cellulose nanofibers (CNFs), we demonstrate a site-specific (93% selective) reaction between the primary surface hydroxyl groups (C6-OH) of cellulose and acyl imidazoles. CNFs bearing C6-acetyl and C6-isobutyryl groups, with a degree of substitution of up to 1 mmol g-1 are obtained upon surface esterification, affording CNFs of adjustable surface energy. The morphological and structural features of the nanofibers remain largely unaffected, but the regioselective surface reactions enable tailoring of their interfacial interactions, as demonstrated in oil/water Pickering emulsions. Our method precludes the need for drying or exchange with organic solvents for surface esterification, otherwise needed in the synthesis of esterified colloids and polysaccharides. Moreover, the method is well suited for application at high-solid content, opening the possibility for implementation in reactive extrusion and compounding. The proposed acylation is introduced as a sustainable approach that benefits from the presence of water and affords a high chemical substitution selectivity.

Multifunctional lignin-based nanocomposites and nanohybrids

Significant progress in lignins valorization and development of high-performance sustainable materials have been achieved in recent years. Reports related to lignin utilization indicate excellent prospects considering green chemistry, chemical engineering, energy, materials and polymer science, physical chemistry, biochemistry, among others. To fully realize such potential, one of the most promising routes involves lignin uses in nanocomposites and nanohybrid assemblies, where synergistic interactions are highly beneficial. This review first discusses the interfacial assembly of lignins with polysaccharides, proteins and other biopolymers, for instance, in the synthesis of nanocomposites. To give a wide perspective, we consider the subject of hybridization with metal and metal oxide nanoparticles, as well as uses as precursor of carbon materials and the assembly with other biobased nanoparticles, for instance to form nanohybrids. We provide cues to understand the fundamental aspects related to lignins, their self-assembly and supramolecular organization, all of which are critical in nanocomposites and nanohybrids. We highlight the possibilities of lignin in the fields of flame retardancy, food packaging, plant protection, electroactive materials, energy storage and health sciences. The most recent outcomes are evaluated given the importance of lignin extraction, within established and emerging biorefineries. We consider the benefit of lignin compared to synthetic counterparts. Bridging the gap between fundamental and application-driven research, this account offers critical insights as far as the potential of lignin as one of the frontrunners in the uptake of bioeconomy concepts and its application in value-added products.

Chitin-amyloid synergism and their use as sustainable structural adhesives

Structural adhesives are relevant to many engineering applications, especially those requiring load-bearing joints with high lap shear strength. Typical adhesives are synthesized from acrylics, epoxies, or urethanes, which may pose a burden to sustainability and the environment. In nature, the interfacial interactions between chitin and proteins are used for structural purposes and as a bio-cement, resulting in materials with properties unmatched by their man-made counterparts. Herein, we show that related supramolecular interactions can be harnessed to develop high strength green adhesives based on chitin nanocrystals (ChNCs), isolated from shrimp shells, and hen egg white lysozyme (HEWL) used in its monomeric or amyloid forms. Consolidation of the bicomponent suspensions, placed between glass substrates, results in long-range ordered superstructures. The formation of these structures is evaluated by surface energy considerations, followed by scanning electron, atomic force, and polarized microscopies of the consolidated materials. For 0.8 mg of bio-adhesive (lysozyme, ChNCs or their composites), lap shear loads of over 300 N are reached. Such remarkable adhesion reaches maximum values at protein-to-ChNC ratios below 1 : 4, reflecting the synergy established between the components (ca. 25% higher load compared to ChNCs, the strongest single component). We put the observed adhesive performance in perspective by comparing the lap-shear performance with current research on green supramolecular adhesives using natural biopolymers. The results are discussed in the context of current efforts to standardize the measurement of adhesive strength and bond preparation. The latter is key to formalizing the metrology and materials chemistry of bio-based adhesives. The proposed all-green system is expected to expand current developments in the design of bio-based adhesives.

Lignin-Based Porous Supraparticles for Carbon Capture

Multiscale carbon supraparticles (SPs) are synthesized by soft-templating lignin nano- and microbeads bound with cellulose nanofibrils (CNFs). The interparticle connectivity and nanoscale network in the SPs are studied after oxidative thermostabilization of the lignin/CNF constructs. The carbon SPs are formed by controlled sintering during carbonization and develop high mechanical strength (58 N·mm^-3) and surface area (1152 m²·g^-1). Given their features, the carbon SPs offer hierarchical access to adsorption sites that are well suited for CO₂ capture (77 mg CO₂·g^-1), while presenting a relatively low pressure drop (∼33 kPa·m^-1 calculated for a packed fixed-bed column). The introduced lignin-derived SPs address the limitations associated with mass transport (diffusion of adsorbates within channels) and kinetics of systems that are otherwise based on nanoparticles. Moreover, the carbon SPs do not require doping with heteroatoms (as tested for N) for effective CO₂ uptake (at 1 bar CO₂ and 40 °C) and are suitable for regeneration, following multiple adsorption/desorption cycles. Overall, we demonstrate porous SP carbon systems of low cost (precursor, fabrication, and processing) and superior activity (gas sorption and capture).

Nanocellulose: Recent Fundamental Advances and Emerging Biological and Biomimicking Applications

In the effort toward sustainable advanced functional materials, nanocelluloses have attracted extensive recent attention. Nanocelluloses range from rod-like highly crystalline cellulose nanocrystals to longer and more entangled cellulose nanofibers, earlier denoted also as microfibrillated celluloses and bacterial cellulose. In recent years, they have spurred research toward a wide range of applications, ranging from nanocomposites, viscosity modifiers, films, barrier layers, fibers, structural color, gels, aerogels and foams, and energy applications, until filtering membranes, to name a few. Still, nanocelluloses continue to show surprisingly high challenges to master their interactions and tailorability to allow well-controlled assemblies for functional materials. Rather than trying to review the already extensive nanocellulose literature at large, here selected aspects of the recent progress are the focus. Water interactions, which are central for processing for the functional properties, are discussed first. Then advanced hybrid gels toward (multi)stimuli responses, shape-memory materials, self-healing, adhesion and gluing, biological scaffolding, and forensic applications are discussed. Finally, composite fibers are discussed, as well as nanocellulose as a strategy for improvement of photosynthesis-based chemicals production. In summary, selected perspectives toward new directions for sustainable high-tech functional materials science based on nanocelluloses are described.

Lignin Nanoparticle Nucleation and Growth on Cellulose and Chitin Nanofibers

Cellulose (CNF) and chitin (ChNF) nanofibers are known to form materials that are both tough and strong. In this study, we hypothesize that the inertness of networks produced from CNF and ChNF makes them ideal templates for heterogeneous reactions and in situ formation of nanoarchitectures. We expand nanoparticle templating on polysaccharide colloids by introducing a new and facile process that leads to the growth of organic nanoparticles on CNF and ChNF in aqueous media. The process, based on solvent shifting supported on solid interfaces, is demonstrated by direct observation of lignin nanoparticles that are further used for their photocatalytic activity. Importantly, the dynamics of nanoparticle nucleation and growth is correlated with the surface chemistry of the templating nanopolysaccharides. Electrostatic repulsion between the deprotonated lignin molecules and the slightly negative CNF support led to limited adsorption and was effective in producing free (nonbound) lignin nanoparticles (28 ± 7 nm) via precipitation. In contrast, the stronger interfacial interactions between the positively charged ChNF and lignin molecules facilitated instantaneous and extensive lignin adsorption, followed by nucleation and growth into relatively larger nanoparticles (46 ± 17 nm). The latter were homogeneously distributed and strongly coupled to the ChNF support. Overall, we introduce lignin nanoparticle nucleation and growth on renewable nanopolysaccharides, offering an effective route toward in situ synthesis of highly functional fibrils and related cohesive films that offer a great potential in packaging and other applications.

Silver Nanowire-Bacterial Cellulose Composite Fiber-Based Sensor for Highly Sensitive Detection of Pressure and Proximity

Fiber-based sensors are desirable to provide an immersive experience for users in the human-computer interface. We report a hierarchically porous silver nanowire-bacterial cellulose fiber that can be utilized for sensitive detection of both pressure and proximity of human fingers. The conductive fiber was synthesized via continuous wet-spinning at a speed of 20 m/min, with a diameter of 53 μm, the electrical conductivity of 1.3 × 10⁴ S/cm, a tensile strength of 198 MPa, and elongation strain of 3.0% at break. The fibers were coaxially coated with a 10 μm thick poly(dimethylsiloxane) dielectric elastomer to form the fiber sensor element which is thinner than a human hair. Two of the sensor fibers were laid diagonally, and the capacitance changes between the conductive cores were measured in response to pressure and proximity. In the touch mode, a fiber-based sensor experienced monotonic capacitance increase in the pressure range from 0 to 460 kPa, and a linear response with a high sensitivity of 5.49 kPa^-1 was obtained in the low-pressure regime (<0.5 kPa). In touchless mode, the sensor is highly sensitive to objects at a distance of up to 30 cm. Also, the fiber can be easily stitched into garments as comfortable and fashionable sensors to detect heartbeat and vocal pulses. A fiber sensor array is able to serve as a touchless piano to play music and accurately determine the proximity of an object. A 2 × 2 array was further shown for two- and three-dimensional location detection of remote objects.