Effects of the Structure and Molecular Weight of Alkali-Oxygen Lignin Isolated from Rice Straw on the Growth of Maize Seedlings.

The abundant and low-cost features of lignin in combination with its natural activities make it a fascinating biopolymer for valorization, especially, in agriculture as an active plant growth regulator. However, the structure-activity relationship of lignin in regulating plant growth and metabolism remains unclear. In this work, rice-straw-based low-molecular-weight (LWM, 1860 Da) and high-molecular-weight (HMW, 6840 Da) alkali-oxygen lignins are structurally and comparatively investigated to understand their effects on the growth and metabolism of maize seedlings. The results indicate that LMW lignin at 150 mg·L-1 displays early growth stimulation in maize. Under the optimal concentration of LMW lignin (25 mg·L-1), the growth of maize shoot is ∼83% higher than that of the control one. Furthermore, LMW lignin also has a positive effect on the upregulation of photosynthetic pigment, carbohydrate, and protein synthesis. In contrast, HMW lignin shows an overall inhibitory effect on the above-mentioned biochemical parameters. Based on the structural characterization, LMW lignin contains a higher syringyl/guaiacyl ratio (0.78) and carboxyl content (1.64 mmol·g-1) than HMW lignin (0.43 and 1.27 mmol·g-1, respectively), which demonstrates that methoxyl and carboxyl content of lignin may play a decisive role in seedling growth.

Enhancing the Radical Scavenging Activity and UV Resistance of Lignin Nanoparticles via Surface Mannich Amination toward a Biobased Antioxidant.

In recent years, lignin specific activities, such as antioxidation and antibacterial and anti-ultraviolet performance, have drawn more and more attention. Nevertheless, the insufficient radical scavenging (antioxidation) activity has become one of the main drawbacks that limits its high-value application. In this study, lignin nanoparticles (LNPs) were prepared via a facile acid treatment strategy. Subsequently, surface amination of LNPs (a-LNPs) was carried out through the Mannich reaction. Specifically, the antioxidant behavior of LNPs and modified LNPs was evaluated by DPPH/DMPO radical scavenging and in vitro HeLa cell reactive oxygen species (ROS) scavenging tests, which demonstrated that the antioxidation activity of a-LNPs was more evident than that of both LNPs and butylated hydroxytoluene (BHT) commercial antioxidant. The mechanism of the radical scavenging ability of aminated LNPs was elucidated and proved to be related to the bond dissociation enthalpy of Ar-O···H, determined by the electron-donating effect of the substituted groups in the ortho-position. Meanwhile, the morphologies, solubilities, and UV-absorbing and antibacterial behavior of LNPs and a-LNPs were also studied, and the results showed that a-LNP sample exhibited higher UV resistance performance than LNPs. We expected that the modified LNPs with high antioxidation activity can serve as a safe and lower-cost biobased antioxidant.

Highly Mineralized Biomimetic Polysaccharide Nanofiber Materials Using Enzymatic Mineralization.

Many biological high-performance composites, such as bone, antler, and crustacean cuticles, are composed of densely mineralized and ordered nanofiber materials. The mimicry of even simplistic bioinspired structures, i.e., of densely and homogeneously mineralized nanofibrillar materials with controllable mechanical performance, continues to be a grand challenge. Here, using alkaline phosphatase as an enzymatic catalyst, we demonstrate the dense, homogeneous, and spatially controlled mineralization of calcium phosphate nanostructures within networks of anionically charged cellulose nanofibrils (CNFs) and cationically charged chitin nanofibrils (ChNFs)-both emerging biobased nanoscale building blocks for sustainable high-performance materials design. Our study reveals that anionic CNFs lead to a more homogeneous nanoscale mineralization with very high mineral contents up to ca. 70 wt % with a transition from amorphous to crystalline deposits, while cationic ChNFs yield rod-like crystalline morphologies. The bone-inspired CNF bulk films exhibit a significantly increased stiffness, maintain good flexibility and translucency, and have a significant gain in wet state mechanical properties. The mechanical properties can be tuned both by the enzyme concentration and the mineralization time. Moreover, we also show a spatial control of the mineralization using kinetically controlled substrate uptake in a dialysis reactor, and by spatially selectively incorporating the enzyme into 2D printed filament patterns. The strategy highlights possibilities for spatial encoding of enzymes in tailored structures and patterns and programmed mineralization processes, promoting the potential application of mineralized CNF biomaterials with complex gradients for bone substitutes and tissue regeneration in general.

Vitrimer Chemistry Meets Cellulose Nanofibrils: Bioinspired Nanopapers with High Water Resistance and Strong Adhesion.

Nanopapers containing cellulose nanofibrils (CNFs) are an emerging and sustainable class of high performance materials. The diversification and improvement of the mechanical and functional property space critically depend on integration of CNFs with rationally designed, tailor-made polymers following bioinspired nanocomposite designs. Here we combine for the first time CNFs with colloidal dispersions of vitrimer nanoparticles (VP) into mechanically coherent nanopaper materials. Vitrimers are permanently cross-linked polymer networks that undergo temperature-induced bond shuffling through an associative mechanism and which allow welding and reshaping on the macroscale. The choice of low glass transition, hydrophobic vitrimers derived from fatty acids and polydimethylsiloxane (PDMS), and achieving dynamic reshuffling of cross-links through transesterification reactions enables excellent compatibility and covalent attachment onto the CNF surfaces. Moreover, the resulting films are ductile, stretchable and offer high water resistance. The success of imparting the vitrimeric polymeric behavior into the nanocomposite, as well as the curing mechanism of the vitrimer, is highlighted through thorough analysis of structural and mechanical properties. The dynamic exchange chemistry of the vitrimers enables efficient welding of two nanocomposite parts as characterized by good bonding strength during single lap shear tests. In the future, we expect that the dynamic character of vitrimers becomes a promising option for the design of mechanically adaptive bioinspired nanocomposites and for shaping and reshaping such materials.

Sustainable Chitin Nanofibrils Provide Outstanding Flame-Retardant Nanopapers.

Sustainable polysaccharide nanofibrils formed from chitin or cellulose are emerging biobased nanomaterials for advanced materials requiring high mechanical performance, barrier properties, for bioactive materials, or other functionalities. Here, we demonstrate a single-step, waterborne approach to prepare additive-free flame-retardant and self-extinguishing, mechanical high-performance nanopapers based purely on surface-deacetylated chitin nanofibrils (ChNFs). We show that the flammability can be critically reduced by exchanging the counterions, e.g. to the phosphate type, using the respective acid providing electrostatic stabilization in the preparation of the ChNFs. This exchange renders beneficial elemental combinations of high contents of N/P (nitrogen/phosphorus) in the final nanopapers, known to provide outstanding performance in halogen- and heavy metal-free flame-retardant materials. Full fire barrier nanopapers can even be obtained by hybridizing the ChNF with nanoclay. Comprehensive fire retardancy tests, including vertical and horizontal flame tests and microscale cone combustion calorimetry, as well as fire breakthrough tests elucidate excellent flame-retardant properties and high structural integrity when being burned. The intrinsic elemental composition of chitin, containing nitrogen, and the simple modification of the counterions to include phosphorus provides key advantages over related, but flammable nanocellulose materials that often require significant chemical modifications and additives to become fire-retardant. By activating a global food waste, this study presents a critical advance for bioinspired, green, and mechanical high-performance materials with extraordinary flame-retardant and fire barrier properties based on sustainable feedstock, using benign water-based room temperature processing, and by avoiding heavy metals and halogen atoms in their composition.

Photoluminescent Hybrids of Cellulose Nanocrystals and Carbon Quantum Dots as Cytocompatible Probes for in Vitro Bioimaging.

We present an approach to construct biocompatible and photoluminescent hybrid materials comprised of carbon quantum dots (CQDs) and TEMPO-oxidized cellulose nanocrystals (TO-CNCs). First, the amino-functionalized carbon quantum dots (NH2-CQDs) were synthesized using a simple microwave method, and the TO-CNCs were prepared by hydrochloric acid (HCl) hydrolysis followed by TEMPO-mediated oxidation. The conjugation of NH2-CQDs and TO-CNCs was conducted via carbodiimide-assisted coupling chemistry. The synthesized TO-CNC@CQD hybrid nanomaterials were characterized using X-ray photoelectron spectroscopy, cryo-transmittance electron microscopy, confocal microscopy, and fluorescence spectroscopy. Finally, the interactions of TO-CNC@CQD hybrids with HeLa and RAW 264.7 macrophage cells were investigated in vitro. Cell viability tests suggest the surface conjugation with NH2-CQDs not only improved the cytocompatibility of TO-CNCs, but also enhanced their cellular association and internalization on both HeLa and RAW 264.7 cells after 4 and 24 h incubation.

Complexes of Magnetic Nanoparticles with Cellulose Nanocrystals as Regenerable, Highly Efficient, and Selective Platform for Protein Separation.

We present an efficient approach to develop cellulose nanocrystal (CNC) hybrids with magnetically responsive Fe3O4 nanoparticles that were synthesized using the (Fe3+/Fe2+) coprecipitation. After 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-catalyzed oxidation of CNC, carbodiimide (EDC/NHS) was used for coupling amine-containing iron oxide nanoparticles that were achieved by dopamine ligand exchange (NH2-Fe3O4 NPs). The as-prepared hybrids (Fe3O4@CNC) were further complexed with Cu(II) ions to produce specific protein binding sites. The performance of magnetically responsive Cu-Fe3O4@CNC hybrids was assessed by selectively separating lysozyme from aqueous media. The hybrid system displayed a remarkable binding capacity with lysozyme of 860.6 ± 14.6 mg/g while near full protein recovery (∼98%) was achieved by simple elution. Moreover, the regeneration of Fe3O4@CNC hybrids and efficient reutilization for protein separation was demonstrated. Finally, lysozyme separation from matrices containing egg white was achieved, thus revealing the specificity and potential of the presented method.

Modification of cellulose nanofibrils with luminescent carbon dots.

Films and hydrogels consisting of cellulose nanofibrils (CNF) were modified by covalent EDC/NHS coupling of luminescent, water-dispersible carbon dots (CDs). Quartz crystal microgravimetry with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR) were used to investigate the attachment of CDs on carboxymethylated CNF (CM-CNF). As the first reported use of CD in nanocellulose products, we provide proof-of-concept for the synthesis of transparent and fluorescent nanopaper and for its tunable luminescence as confirmed by confocal microscopy imaging.

Polyethylene glycol regulates the pitch and liquid crystal behavior of cellulose nanocrystal-based photonic crystals.

Inspired by iridescent color in natural creations, cellulose nanocrystal (CNC) photonic crystals artificially created by nanotechnology have great application prospects due to their potential to control light propagation in the linear and nonlinear regimes. One of the most important development directions of photonic crystals is the diversification of colors, usually by adjusting the pitch. However, few researchers notice the effect of polymer molecular weight and content on pitch regulation and the interaction between polymer and CNC liquid crystals. Polyethylene glycol (PEG) were used as polymers to regulate the pitch of CNC photonic crystals and investigate the changes in microstructure, crystal structure, thermal properties, and liquid crystal texture of the composites by changing the PEG content and molecular weight. Different photonic crystal construction systems show that when the molecular weight of PEG is 0.4 k, it can be filled between CNCs to regulate the pitch of photonic crystals, while when the molecular weight of PEG is 20 k, it cannot always be filled between CNCs in evaporation-induced self-assembly (EISA) process due to the depletion interaction, which cannot effectively regulate the pitch. This study reveals the relationship between PEG and CNC liquid crystals, which supports the development of photonic crystals and the pitch regulation.

Plasmonic filter paper for preconcentration, separation and SERS detection harmful chemicals in chili product by fluid flow.

We proposed a triple functional SERS substrate by immobilized Ag nanoparticles on the surface of filter paper. The high dense Ag nanoparticles were distributed on the SERS substrate via in-situ growth process. By optimizing the parameter in preparation process, the optimal filter paper SERS substrate was fabricated by using 30 mM of AgNO3 with 20 S growth time. Due to capillary-effect wicking of cellulose fiber, the paper SERS substrate provide simple, fast and pump-free function for transferring analyte onto sharp tip through development of fluid. The fluid flow also brings target concentrate effect within the tip area. Furthermore, the separation feasibility was obtained during the development process of fluid. The preconcentrated effects not only enhanced the SERS signal of analyte, but also improve the fluorescence visible effect. The filter paper SERS substrate was successfully used for separating, concentrating and detecting Sudan dye from chili product, the detection limit could achieve 10-6 M. This study developed a portable, cost-effective and eco-friendly SERS substrate for separating and detecting trace chemical in food.

Hydrostability, mechanical resilience, and biodegradability of paper straws fabricated through lignin-based polyurethane and chitosan binary emulsion bonding.

This study focuses on enhancing the strength and water stability of paper straws through a novel approach involving a binary emulsion of lignin-based polyurethane and chitosan. Kraft lignin serves as the raw material for synthesizing a blocked waterborne polyurethane, subsequently combined with carboxylated chitosan to form a stable binary emulsion. The resulting emulsion, exhibiting remarkable stability over at least 6 months, is applied to the base paper. Following emulsion application, the paper undergoes torrefaction at 155 °C. This process deblocks isocyanate groups, enabling their reaction with hydroxyl groups on chitosan and fibers, ultimately forming ester bonds. This reaction significantly improves the mechanical strength and hydrophobicity of paper straws. The composite paper straws demonstrate exceptional mechanical properties, including a tensile strength of 47.21 MPa, Young's modulus of 4.33 GPa, and flexural strength of 32.38 MPa. Notably, its water stability is greatly enhanced, with a wet tensile strength of 40.66 MPa, surpassing commercial paper straws by 8 folds. Furthermore, the composite straw achieves complete biodegradability within 120 days, outperforming conventional paper straws in terms of environmental impact. This innovative solution presents a promising and sustainable alternative to plastic straws, addressing the urgent need for eco-friendly products.

Pickering emulsion stabilization with colloidal lignin is enhanced by salt-induced networking in the aqueous phase.

We study the effect of electrolytes on the stability in aqueous media of spherical lignin particles (LP) and its relevance to Pickering emulsion stabilization. Factors considered included the role of ionic strength on morphology development, LP size distribution, surface charge, interfacial adsorption, colloidal and wetting behaviors. Stable emulsions are formed at salt concentrations as low as 50 mM, with the highest stability observed at a critical concentration (400 mM). We show salt-induced destabilization of LP aqueous dispersions at an ionic strength >400 mM. At this critical concentration LP flocculation takes place and particulate networks are formed. This has a profound consequence on the stability of LP-stabilized Pickering emulsions, affecting rheology and long-term stability. The results along with quartz microgravimetry and confocal microscopy observations suggest a possible mechanism for stabilization that considers the interfacial adsorption of LP at oil/water interfaces. The often-unwanted colloidal LP destabilization in water ensues remarkably stable Pickering emulsions by the effect of network formation.

Effects of hydrolysis conditions on the morphology of cellulose II nanocrystals (CNC-II) derived from mercerized microcrystalline cellulose.

The properties of cellulose nanocrystals with allomorph II (CNC-II) vary with the sources and the treatments received. In this work, the influences of hydrolysis time, temperature, and the applied acid concentration on the crystal size of CNC-II were investigated by the surface response experimental design. The results showed that temperature was the most significant factor affecting the crystal size of CNC-II during hydrolysis from mercerized cellulose. Then the morphology and colloidal properties of CNC-II were revealed by dynamic laser scattering (DLS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), etc. XRD results indicated that CNC-II had slightly lower crystallinity (80.89 % vs 82.7 %) and larger crystallite size (5.21 vs. 5.13 nm) than CNC-I. TEM and AFM results showed that the morphology of CNC-II were disc-like and rod-like particles, with an average diameter of 14.6 ± 4.7 nm (TEM) and a thickness of 4- 8 nm (AFM). TG and XPS revealed the reduced thermal stability was due to the introduced sulfate groups in CNC-II during hydrolysis. This investigation has addressed the features of CNC-II derived from mercerized cellulose, and it would be promising in fabricating advanced materials.

A copper-loaded self-assembled nanoparticle for disturbing the tumor redox balance and triple anti-tumor therapy.

Both chemodynamic therapy and photodynamic therapy, based on the production of reactive oxygen (ROS), have excellent potential in cancer therapy. However, the abnormal redox homeostasis in tumor cells, especially the overexpressed glutathione (GSH) could scavenge ROS and reduce the anti-tumor efficiency. Therefore, it is essential to develop a simple and effective tumor-specific drug delivery system for modulating the tumor microenvironment (TME) and achieving synergistic therapy at the tumor site. In this study, self-assembled nanoparticles (named CDZP NPs) were developed using copper ion (Cu2+), doxorubicin (Dox), zinc phthalocyanine (ZnPc) and a trace amount of poly(2-(di-methylamino)ethylmethacrylate)-poly[(R)-3-hydroxybutyrate]-poly(2-(dimethylamino)ethylmethacrylate) (PDMAEMA-PHB-PDMAEMA) through chelation, π-π stacking and hydrophobic interaction. These triple factor-responsive (pH, laser and GSH) nanoparticles demonstrated unique advantages through the synergistic effect. Highly controllable drug release ensured its effectiveness at the tumor site, Dox-induced chemotherapy and ZnPc-mediated fluorescence (FL) imaging exhibited the distribution of nanoparticles. Meanwhile, Cu2+-mediated GSH-consumption not only reduced the intracellular ROS elimination but also produced Cu+ to catalyze hydrogen peroxide (H2O2) and generated hydroxyl radicals (˙OH), thereby enhancing the chemodynamic and photodynamic therapy. Herein, this study provides a green and relatively simple method for preparing multifunctional nanoparticles that can effectively modulate the TME and improve synergetic cancer therapy.

Biosafety consideration of nanocellulose in biomedical applications: A review.

Nanocellulose-based biomaterials have gained significant attention in various fields, especially in medical and pharmaceutical areas, due to their unique properties, including non-toxicity, high specific surface area, biodegradability, biocompatibility, and abundant feasible and sophisticated strategies for functional modification. The biosafety of nanocellulose itself is a prerequisite to ensure the safe and effective application of biomaterials as they interact with living cells, tissues, and organs at the nanoscale. Potential residual endogenous impurities and exogenous contaminants could lead to the failure of the intended functionalities or even serious health complications if they are not adequately removed and assessed before use. This review summarizes the sources of impurities in nanocellulose that may pose potential hazards to their biosafety, including endogenous impurities that co-exist in the cellulosic raw materials themselves and exogenous contaminants caused by external exposure. Strategies to reduce or completely remove these impurities are outlined and classified as chemical, physical, biological, and combined methods. Additionally, key points that require careful consideration in the interpretation of the biosafety evaluation outcomes were discussed to ensure the safety and effectiveness of the nanocellulose-based biomaterials in medical applications.

Comparison of hydrophobic cellulose nanofibrils modified with different diisocyanates for circulating oil absorption.

A large number of polluting substances, including chlorinated organic substances that were highly stable and hazardous, has been emitted due to the rapidly developing chemical industry, which will affect the ecological environment. Nanocellulose aerogels are effective carriers for adsorption of oil substances and organic solvents, however, the extremely strong hydrophilicity and poor mechanical properties limited their widespread applications. In this study, TEMPO-oxidized cellulose nanofibrils was modified with 2, 4-toluene diisocyanate (TDI) and 4,4'-diphenylmethane diisocyanate (MDI) to prepare strong and hydrophobic aerogels for oil adsorption. The main purpose was to evaluate and compare the effects of two diisocyanates on various properties of modified aerogels. It was found that the modified aerogel had better hydrophobic properties, mechanical properties and adsorption properties. In particular, the modified aerogel with TDI as crosslinker showed a better performance, with a maximum chloroform adsorption capacity of 99.3 g/g, a maximum water contact angle of 131.3°, and a maximum compression stress of 36.3 kPa. This study provides further evidence of the potential of functional nanocellulose aerogel in addressing environmental pollution caused by industrial emissions.

Fabrication of bio-inspired anisotropic structures from biopolymers for biomedical applications: A review.

The anisotropic features play indispensable roles in regulating various life activities in different organisms. Increasing efforts have been made to learn and mimic various tissues' intrinsic anisotropic structure or functionality for broad applications in different areas, especially in biomedicine and pharmacy. This paper discusses the strategies for fabricating biomaterials using biopolymers for biomedical applications with the case study analysis. Biopolymers, including different polysaccharides, proteins, and their derivates, that have been confirmed with sound biocompatibility for different biomedical applications are summarized, with a special focus on nanocellulose. Advanced analytical techniques for understanding and characterizing the biopolymer-based anisotropic structures for various biomedical applications are also summarized. Challenges still exist in precisely constructing biopolymers-based biomaterials with anisotropic structures from molecular to macroscopic levels and fitting the dynamic processes in native tissue. It is foreseeable that with the advancement of biopolymers' molecular functionalization, biopolymer building block orientation manipulation strategies, and structural characterization techniques, developing anisotropic biopolymer-based biomaterials for different biomedical applications would significantly contribute to a friendly disease-curing and healthcare experience.

In-situ CBM3-modified bacterial cellulose film with improved mechanical properties.

Cellulose materials have poor wet strength and are susceptible to acidic or basic environments. Herein, we developed a facile strategy to modify bacterial cellulose (BC) with a genetically engineered Family 3 Carbohydrate-Binding Module (CBM3). To assess the effect of BC films, water adsorption rate (WAR), water holding capacity (WHC), water contact angle (WCA), and mechanical and barrier properties were determined. The results showed that CBM3-modified BC film exhibited significant strength and ductility improvement, reflecting improved mechanical properties of the film. The excellent wet strength (both in the acidic and basic environment), bursting strength, and folding endurance of CBM3-BC films were due to the strong interaction between CBM3 and fiber. The toughness of CBM3-BC films reached 7.9, 28.0, 13.3, and 13.6 MJ/m3, which were 6.1, 1.3, 1.4, and 3.0 folds over the control for conditions of dry, wet, acidic, and basic, respectively. In addition, its gas permeability was reduced by 74.3 %, and folding times increased by 56.8 % compared with the control. The synthesized CBM3-BC films may hold promise for future applications in food packaging, paper straw, battery separator, and other fields. Finally, the in situ modification strategy used to BC can be successfully applied in other functional modifications for BC materials.

Nature-inspired construction of iridescent CNC/Nano-lignin films for UV resistance and ultra-fast humidity response.

Exploration of functional materials based on sustainable and renewable biomolecules has been of much interest. Herein, nature-inspired photonic films were proposed by incorporation of bio-based lignin nanoparticles (LNPs) into chiral nematic cellulose crystals (CNCs). Evaporation induced self-assembly (EISA) formed oriented and layered structure of the nanocomposites iridescent films with enlarged helix pitches by intercalation of higher amounts of LNPs. Decreased crystallite sizes and expanding layer gaps indicated the homogeneous distribution and hydrophobic interactions between CNCs and LNPs. Distinguished UV absorption capabilities with over 90 % shielding capabilities in UVB region and increased hydrophobicity with the contact angle of 75° were achieved for the composite films due to the presence of hydrophobic lignin. The proposed optical films also showed outstanding cytocompatibility owing to all-natural components introduced into the materials, which may display great potentials in many fields such as stimuli sensing, anti-counterfeiting and wearable devices.

Enzymatic saccharification promotion for bioenergy poplar under green liquor pretreatment by fully sulfonated polystyrene: Effect of molecular weight.

Water-soluble lignin and lignin derivatives are cited to promote the enzymatic saccharification of lignocellulose. Herein, a series of fully sulfonated polystyrene sulfonates (FSPSSs) with various molecular weights (MW) were synthesized through free radical polymerization (FRP) and atom transfer radical polymerization (ATRP) to serve as lignin analogues to boost the enzymatic saccharification of bioenergy poplar under green liquor pretreatment. The FRP-made polymers with MW 944.5 × 103 to 123.6 × 103 g/mol increased the enzymatic hydrolysis digestibility (SED) by 13 % to 18.8 %. On contrary, the ATRP-made polymers with lower MW (3.8 × 103-12.2 × 103 g/mol) showed a weak effect with<8 % improvement in SED. This can be explained the adsorption capacity and the conformation of cellulase-FSPSS complexes, which respond to the reducing nonproductive adsorption correlated to their MWs, due to the strong dependence of molecular conformation on the chain length of strong polyelectrolytes.