Lignin nanoparticles enter the scene: A promising versatile green tool for multiple applications

Lignin from aldehyde-assisted fractionation can provide light-colored Pickering emulsions through colloidal particles formed using alkaline antisolvent

Colloidal lignin particles (CLPs) are gaining attention as eco-friendly stabilizers for Pickering emulsions. Still, conventional lignin sources, like kraft lignin, are often limited by their dark color and strong odor. This study explores, for the first time, the use of a light-colored lignin derived from an aldehyde-assisted fractionation with glyoxylic acid (GA-lignin) for producing CLPs and derived Pickering emulsions. CLPs were produced by antisolvent precipitation with water (CLPs-W, pH 6) and alkaline buffer (CLPs-B, pH 8) as the antisolvents. The results revealed that the selected antisolvent significantly influenced the CLPs' properties. CLPs-W were larger, uniform in size, and hydrophobic, whereas CLPs-B were smaller, agglomerated into clusters, and exhibited greater hydrophilicity. Despite both CLPs' effectiveness in stabilizing oil-in-water emulsions, the stabilization mechanisms differed markedly; CLPs-W formed a robust membrane barrier at the oil-water interface, while CLPs-B facilitated oil droplet bridging. Overall, this work demonstrates that GA-lignin's light color nature offers advantages for Pickering emulsions design, surpassing a lignin typical limitation. This advancement highlights the versatility of GA-lignin-derived CLPs and supports the development of sustainable lignin-based products with significant commercial prospects.

Bioactive lignin from maleic acid hydrotropic fractionation: Revealing the structural-bioactivity relationship

Lignin possesses diverse bioactivities due to its unique physicochemical structure. This study investigates the structural-bioactivity relationships of lignin derived from maleic acid hydrotropic fractionation (MAHF) of two types of herbaceous biomass. The results indicated that lignin with higher phenolic hydroxyl (-OH) content (up to 2.0 mmol/g) and carboxyl (-COOH) groups (up to 0.89 mmol/g) exhibited significantly enhanced antioxidant activity. The highest antioxidant of MAHF lignin (MAHL) reached 98 % for scavenging DPPH (2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl) at 0.56 mg/mL. Antibacterial tests revealed that MAHLs demonstrated inhibition rates of 66 % against E. coli and 54 % against S. aureus at 10 mg/mL. MAHLs at 1 mg/mL concentration blocked >98 % of UV radiation. Furthermore, the study demonstrated that lignin with higher phenolic hydroxyl (-OH), carboxyl (-COOH), and syringyl (S) units and conjugated double bonds exhibit enhanced bioactive properties. Lignin with lower Mw and PDI also tends to possess good bioactivities. The findings from the study can facilitate the application of lignin as an efficient, cost-effective, and renewable biopolymer additive in various industries.

From waste to wonder: Biomass-derived nanocellulose and lignin-based nanomaterials in biomedical applications

Cellulose and lignin, as the most abundant biomass resources in nature, have been widely utilized in conventional industry. While their high-value potential remained underexplored for decades, recent advancements in nanotechnology and processing techniques have revealed their unique physicochemical properties, biocompatibility, and optical characteristics at the nanoscale, sparking significant interest in biomedical applications. Nanocellulose (NC), characterized by its high surface area, superior mechanical strength, and excellent biocompatibility, holds great promise in drug delivery, wound dressing, and tissue engineering. Similarly, lignin nanoparticles (LNPs) and lignin-based carbon quantum dots (L-CQDs), known for their multi-functionality, low toxicity, and outstanding fluorescence properties, emerge as sustainable alternatives for bio-imaging and bioanalytical detection. This review provides an overview of the hierarchical structure of biomass resources, details the preparation methods of cellulose- and lignin-based nanomaterials, and highlights their advancements in biomedical applications. Furthermore, it addresses the challenges and limitations associated with the clinical applications of these nanomaterials, offering insights and guidance for future research and development.

Lignin nanoparticle-stabilized pickering emulsion: Mechanism, influencing parameter, and emerging application

Pickering emulsions using solid particles as stabilizers have attracted considerable interest due to their unique properties, environmental protection, high stability, and cost-effectiveness. However, the current solid particles used as stabilizers have been unable to meet the demands for sustainable development. Lignin nanoparticles (LNPs) are nanoscale particles derived from lignin, a complex biopolymer found in the cell walls of woods and plants. In recent years, LNPs have been widely used to stabilize Pickering emulsions due to its abundance, nanometer size, large specific surface area, good wettability, non-toxicity, and biodegradability. In this review, we overview the recent advances in the LNP-stabilized Pickering emulsion and their applications in a wide spectrum of emerging fields. The structure, preparation, and safety of LNPs are briefly overviewed. Then, the stabilization mechanism of LNP-stabilized Pickering emulsion is introduced. Next, two types of LNP-stabilized Pickering emulsion (i.e., unmodified and modified LNPs), their influencing factors, and physiochemical properties are comprehensively discussed. The recent advances in the application of LNP-stabilized Pickering emulsions in five areas are subsequently outlined, i.e., i) nanocomposites, ii) two-phase catalysis, iii) biomedicine, iv) daily skincare products, and v) enhanced oil recovery. Finally, the prospects of LNP-stabilized Pickering emulsion in the aforementioned fields are proposed.

Metal Ion Cross-Linked Cellulose/Lignin Nanocomposite Films: A Pathbreaking Approach toward High-Performance Sustainable Biomaterials

Inspired by the reinforcement mechanisms observed in biomaterials, cellulose/lignin composite membranes are prepared successfully by mixing nanolignin and nanocellulose and impregnating them with metal ion solution. Metal ion cross-linking and hydrogen bonds between cellulose and lignin create a robust cross-linking network. The composite films achieve a tensile strength of 223.8 MPa, more than twice that of pure nanocellulose films (104 MPa), and surpass commonly used commercial petroleum-based plastics. Through investigation utilizing dynamic rheological experiments and density functional theory, the interactions between cellulose fibers and lignin are elucidated, showcasing the synergistic effects of Ca2+ cross-linked oxygen-containing functional groups and hydrogen bonding. These interactions enhance the strength and toughness of the composite films. Capitalizing on the hydrophobic nature of nanolignin and the strong interactions between metal ions and oxygen-containing functional groups, the wet strength of the composite films reached 33.3 MPa. Moreover, the composite material demonstrates optical properties, electromechanical stability, and thermal stability, including the UV blocking rate. Compared to petroleum-based plastics such as polyethylene and poly(vinyl chloride), cellulose-based films completely degrade within 30 days. With its inherent biodegradability, the composite films have the potential to replace conventional plastics in various applications, advancing sustainable and environmentally friendly materials.

Formation of Homogeneous Lignin Nanoparticles from Industrial Kraft Lignin via Fractionation Combined with Antisolvent Precipitation

Processing lignin into nanoparticles (LNPs) offers a promising utilization strategy; however, its structural and molecular weight heterogeneity poses challenges in the formation of uniform LNPs. In this study, industrial kraft lignin was fractionated in stepwise molecular weight (Mw) from low to high and from which LNPs were fabricated via antisolvent precipitation. The results showed that lignin with high Mw benefits the formation of uniform and smaller-sized LNPs. Particularly, the lignin fraction with Mw of 2016 g·mol-1 fails to form LNPs. The main mechanism is that the higher content of hydrophilic groups (mainly phenolic hydroxyl groups) on the lower molecular weight lignin hinders the formation of LNPs. This hypothesis is supported by the successful formation of homogeneous LNPs after low molecular weight lignin acetylation. Fractionation effectively reduces lignin heterogeneity and promotes the formation of LNPs, which would favor the chemical reactivity and properties, enhancing the utilization of industrial lignin.

Tunning antisolvent precipitation for the synthesis of lignin nanoparticles using lignin extracted from different agro-industrial wastes

Lignin nanoparticles (LNPs) show great potential in UV-protectants, drugs carriers, encapsulation, supercapacitors, and others. This study proposes the development of an optimised LNP synthesis method by antisolvent precipitation, using lignin from persimmon tree pruning waste, green coconut waste, and sugarcane bagasse. The best synthesis conditions were determined evaluating the chemical composition and the physicochemical properties of the LNPs, by varying the antisolvent addition rate, initial lignin concentration and antisolvent pH. Optimal precipitation conditions - 250 μL·s-1, 5 mg·mL-1 of lignin, pH 7.0 (antisolvent), 250 μL·s-1 adding antisolvent - converted the persimmon, coconut, and the sugarcane lignin into nanometric structures (Ø = 130-192 nm), with a spherical morphology, which were stable during storage at 5 °C for 90 days. Particle formation did not cause significant changes in the chemical composition of the lignins, and regardless of the plant origin, the LNPs showed higher UV absorption and thermal stability than the original corresponding lignins.

Harnessing Lignin Nanoparticles for Sustainable Enzyme Immobilization: Current Paradigms and Future Innovations

Lignin, a vital plant component, is key in providing structural integrity and is the second most abundant biopolymer in nature. The growing interest in sustainable and efficient biocatalysis has driven the exploration of lignin nanoparticles (LNPs) as a promising platform for enzyme immobilization. Given lignin's abundance and structural role in plants, converting it into nanoparticles offers a potential eco-friendly alternative to traditional supports. This comprehensive review explores recent advancements in using LNPs for enzyme immobilization, focusing on loading techniques, immobilization efficiency, enzyme activity levels, and various factors that affect the performance of enzymes immobilized on LNPs. The review also addresses the primary challenges associated with enzyme immobilization on LNPs and discusses future innovations in this field. Adopting eco-friendly immobilization platforms based on LNPs is expected to have broad applications in industries like food, pharmaceuticals, animal feed, and detergents. However, there is still potential to customize LNPs further and develop novel immobilization techniques to leverage their benefits fully. By understanding the properties and advantages of these nanostructured lignin supports, researchers can design and create innovative nanocatalysts for various industrial applications.

Hydrophobic Nanostructured Coatings of Colloidal Lignin Particles Reduce Nutrient Leaching and Enhance Wheat Agronomic Performance and Nutritional Quality

Traditional farming practices are increasingly being replaced with more sustainable approaches, including the development of slow-release fertilizers (SRFs), to mitigate environmental stress and ensure food security for the ever-growing global population. Despite the rising focus on eco-friendly materials like biopolymers for fertilizer coatings, optimizing their hydrophobicity remains a significant challenge. In this context, nanotechnology offers a promising route toward achieving hydrophobicity and sustainability. In this study, hydrophobic colloidal lignin particles (20-50 nm) were synthesized using a straightforward acid precipitation method involving the coprecipitation of lignin (LGe) and sodium dodecyl sulfate (SDS). This strategy aimed to reduce particle size, enhance stability, and increase hydrophobicity by incorporating the nonpolar SDS alkyl chains onto the surface of the nanomicelles. TEM and STEM microscopy confirmed the formation of core-shell hybrid micelles, which were incorporated into a cross-linked carboxymethyl cellulose (CMC) matrix at various ratios to produce a series of waterborne coating formulations and films. The spherical morphology and new surface features, along with their integration into an interpenetrating cross-linked network, led to the formation of nanostructured coating films with good hydrophobicity (WCA ∼ 106.1°) and slow biodegradability in soil. When applied to diammonium phosphate (DAP) granular fertilizer, the coatings revealed good interfacial adhesion, enhanced hardness (2.5-fold), and improved water-holding capacity in soil (18%). Most importantly, a 100 day nutrient leaching study revealed an impressive nutrient-release longevity, showing a 75% reduction in N-P leaching. Subsequently, these SRFs were evaluated in a 6 month wheat (Triticum aestivum)) cultivation trial across different soil textures, demonstrating substantial enhancements in leaf area (150-200%), total root length (160%), biomass production (575%), grain yield (115-264%), and quality-related parameters. These findings highlight a robust solution for addressing nutrient deficiencies and promoting sustainable agricultural practices, especially for crops with extended growth cycles, while inspiring novel nanostructured coatings for broader applications.

Lignin-Based Functional Materials in Agricultural Application: A Review

The demand for biodegradable, sustainable, and eco-friendly alternatives is growing in crop production and protection, which forces an urgent need for society to shift toward more sustainable agricultural development. In recent years, the development and research of lignin-based functional materials have gained increasing attention and impetus, and their use has become more widespread in sustainable agriculture. This review covers the latest research on the potential applications of lignin-based functional materials in plant protectants, sensors for pollutant detection, toxic element removal in soil and water, enzyme immobilization, plant growth regulators/biostimulants, hydrogels, and mulching films. Finally, future challenges and perspectives of lignin-based functional materials are discussed to provide a new strategy for the promotion of sustainable agriculture.

Lignin and Nanolignin: Next-Generation Sustainable Materials for Water Treatment

Water scarcity, contamination, and lack of sanitation are global issues that require innovations in chemistry, engineering, and materials science. To tackle the challenge of providing high-quality drinking water for a growing population, we need to develop high-performance and multifunctional materials to treat water on both small and large scales. As modern society and science prioritize more sustainable engineering practices, water treatment processes will need to use materials produced from sustainable resources via green chemical routes, combining multiple advanced properties such as high surface area and great affinity for contaminants. Lignin, one of the major components of plants and an abundant byproduct of the cellulose and bioethanol industries, offers a cost-effective and scalable platform for developing such materials, with a wide range of physicochemical properties that can be tailored to improve their performance for target water treatment applications. This review aims to bridge the current gap in the literature by exploring the use of lignin, both as solid bulk or solubilized macromolecules and nanolignin as multifunctional (nano)materials for sustainable water treatment processes. We address the application of lignin-based macro-, micro-, and nanostructured materials in adsorption, catalysis, flocculation, membrane filtration processes, and antimicrobial coatings and composites. Throughout the exploration of recent progress and trends in this field, we emphasize the importance of integrating principles of green chemistry and materials sustainability to advance sustainable water treatment technologies.

Study on Highly Sensitive Capacitive Pressure Sensor Based on Silk Fibroin-Lignin Nanoparticles Hydrogel

Silk fibroin (SF) hydrogel has been proven to have excellent applications in the field of pressure sensors, but its sensing performance still needs improvement. A flexible hydrogel prepared from natural macromolecular materials was developed, and lignin nanoparticles (LNPs) were introduced during the preparation of the SF hydrogel. When LNPs account for 3% of SF, the sensing unit of the SF-LNPs3% hydrogel exhibits high stress sensitivity (1.32 kPa-1), fast response speed (<0.1 s), and superior cycle stability (≥8000 cycles). The sensor can detect human motion information, such as finger bending, elbow bending, and pulse signals. When worn at the vocal cord position, it can detect the peak value of the characteristic signal during the wearer speaks. This work demonstrates that the SF-LNPs3% hydrogel has high sensitivity and shows great potential in the field of pressure sensors.

Lignin and copper nanocomposite coating for antibacterial mask

Lignin is a natural phenolic polymer characterized with renewable, sustainable and biocompatible, but yet remain underutilized. In the post-pandemic era, people are conventionally reusing mask but without any disinfections to prevent infection of virus in public places, which could lead to accumulation of bacteria and secondary infections. The development of antibacterial mask from lignin would simultaneously address the hygiene issues of used mask due to microbe accumulation and provide novel approach for lignin valorization. Herein, lignin/copper nanoparticle with excellent water dispersibility, antibacterial activity, and non-cytotoxicity was synthesized by in situ reduction of copper ions in lignin nanoparticles. The structure of lignin/copper nanoparticle, and antibacterial performance of the mask were thoroughly explored to understand the key factors to tune the process. Antibacterial mask was then prepared by simple dip coating of the lignin/copper nanocomposite onto the middle layer of a mask, which could effectively prevent the penetration of bacteria from the outer layer into the inner layer. The results of this study provide a feasible approach to prepare antibacterial mask using plant-derived, sustainable, and cheap raw material, namely lignin, which facilitate the high value valorization of lignin.

A Systematic Study of the Structural Properties of Technical Lignins

Technical lignins are globally available and a sustainable feedstock. The unique properties of technical lignins suggest that these materials should have several industrial applications. The main proposal of this study is to evaluate the relationship between the structure and properties of two technical lignins. Morphological, chemical, physical, and thermal properties of sodium lignosulfonate (LGNa) and magnesium lignosulfonate (LGMg) were investigated. The results showed that a higher formation of intramolecular hydrogen bonds may occur in lignins with a higher content of phenolic hydroxyl groups, such as LGMg. As a result, an increase in the energy of hydrogen bonds in the lignosulfonate structure was observed, without significant change in the hydrogen bond distances. In addition, higher content of phenolic hydroxyl groups might also reduce lignosulfonates thermal stability. The combustion index value was three times higher for LGMg than for LGNa. The characterization study also revealed that phenolic hydroxyl groups influence the main properties of technical lignins and can be a determining factor when these lignosulfonates are used in industrial applications.

Preparation and Biological Activity of Lignin-Silver Hybrid Nanoparticles

Silver nanoparticles (AgNPs) are excellent antimicrobial agents and promising candidates for preventing or treating bacterial infections caused by antibiotic resistant strains. However, their increasing use in commercial products raises concerns about their environmental impact. In addition, traditional physicochemical approaches often involve harmful agents and excessive energy consumption, resulting in AgNPs with short-term colloidal stability and silver ion leaching. To address these issues, we designed stable hybrid lignin-silver nanoparticles (AgLigNPs) intended to effectively hit bacterial envelopes as a main antimicrobial target. The lignin nanoparticles (LigNPs), serving as a reducing and stabilizing agent for AgNPs, have a median size of 256 nm and a circularity of 0.985. These LigNPs were prepared using the dialysis solvent exchange method, producing spherical particles stable under alkaline conditions and featuring reducing groups oriented toward a wrinkled surface, facilitating AgNPs synthesis and attachment. Maximum accumulation of silver on the LigNP surface was observed at a mass reaction ratio mAg:mLig of 0.25, at pH 11. The AgLigNPs completely inhibited suspension growth and reduced biofilm development by 50% in three tested strains of Pseudomonas aeruginosa at a concentration of 80/9.5 (lignin/silver) mg L-1. Compared to unattached AgNPs, AgLigNPs required two to eight times lower silver concentrations to achieve complete inhibition. Additionally, our silver-containing nanosystems were effective against bacteria at safe concentrations in HEK-293 and HaCaT tissue cultures. Stability experiments revealed that the nanosystems tend to aggregate in media used for bacterial cell cultures but remain stable in media used for tissue cultures. In all tested media, the nanoparticles retained their integrity, and the presence of lignin facilitated the prevention of silver ions from leaching. Overall, our data demonstrate the suitability of AgLigNPs for further valorization in the biomedical sector.

Minimizing food oxidation using aromatic polymer: From lignin into nano-lignin

Food loss and waste caused by oxidation result in environmental and economic losses and health threats. Lignin is an abundant aromatic polymer with varied antioxidant capacity, which can reduce food oxidation caused by radical species exposure. The lignin antioxidant strength can be influenced by source, type, structure, processing, degradation products, chemical modifications, and particle size. Lignin in micro- or nano-particles has high reactivity and is associated with increased surface area to improve antioxidant capacity. Lignin can be used as a food additive to suppress lipid and protein oxidation, although its effect on fruit/vegetable oxidation needs to be discussed. The lignin antioxidant properties are promising to be applied in food industries, such as food additives, animal feed supplements, and antioxidant packaging designs. However, there are challenges and limitations to consider, such as the potential for toxicity reactions in some individuals and the need for further research to understand its effects on different food products fully. As a feed nutrition, lignin can improve meat quality. Meanwhile, loading lignin in the packaging matrix can extend the food shelf life through antioxidant and antimicrobial activities, and UV-block. Lignin also improves packaging properties (conventional and 3D-printing fabrication) to maintain food quality, e.g., changes in mechanical properties, hydrophobicity, water vapor permeability, and other influences. This article reviews lignin's role as a natural antioxidant in the food industry. Future directions and discussions relate to prooxidative mechanisms, toxicity, fruit and vegetable preservation mechanisms, inhibition of protein oxidation, activity to food enzymes (fruit ripening enzyme activators and inhibitors of cellulase and β-glucosidase enzyme), dispersity in packaging matrices, and material diversification for 3D printing.

Lignin nanoparticles enable and improve multiple functions of photonic films derived from cellulose nanocrystals

Flexible photonic materials derived from cellulose nanocrystals (CNCs) have attracted significant attention, particularly in multifunctional sensors, intelligent detection, and anti-counterfeiting applications. However, the major bottleneck with traditional CNC photonic materials is the provision of flexibility and multifunctional properties which often comes with compromises in optical properties. To address these challenges, we incorporated organosolv lignin nanoparticles (LNPs) and polyethylene glycol (PEG) into CNC films. LNPs were produced from sugarcane bagasse using various solvents, resulting in nanoparticles with distinct structural and chemical properties, such as different sizes and surface chemistries. The addition of LNPs and PEG to CNC films led to enhanced flexibility, strong iridescence, improved thermal stability and superior UV-blocking performance. Interestingly, the intercalation of LNPs significantly improved the strain at break by 89.6 % with slight increase of 7.7 % and 23.1 % in tensile strength and young's modulus respectively. Additionally, distinguished UV-blockage performance of up to 99.9 % in the UVB region and 94 % in the UVA region was also achieved in CNC-LNP-PEG films. The films exhibited varying responses to several organic solvents and HCl gas with reversible color changes. These responses were attributed to the distinct surface chemistries of the LNPs, which influenced their interactions with the CNC matrix through mechanisms such as hydrogen bonding and hydrophobic interactions. This study highlights the potential of CNC-LNP-PEG composite films for advanced applications in chemical safety and anti-counterfeiting measures, demonstrating the importance of composite formulation and processing conditions in achieving desirable properties.

Lignin nanoparticles from Ayurvedic industry spent materials: Applications in Pickering emulsions for curcumin and vitamin D3 encapsulation

Lignin nanoparticles (LNP), extracted from spent materials of Dashamoola Arishta (Ayurvedic formulation), shared a molecular weight of 14.42 kDa with commercial lignin. Processed into LNPs (496.43 ± 0.54 nm) via planetary ball milling, they demonstrated stability at pH 8.0 with a zeta potential of -32 ± 0.27 mV. Operating as Pickering particles, LNP encapsulated curcumin and vitamin D3 in sunflower oil, forming LnE + Cu + vD3 nanoemulsions (particle size: 347.40 ± 0.71 nm, zeta potential: -42.27 ± 0.72 mV) with high encapsulation efficiencies (curcumin: 87.95 ± 0.21%, vitamin D3: 72.66 ± 0.11%). The LnE + Cu + vD3 emulsion exhibited stability without phase separation over 90 days at room (27 ± 2 °C) and refrigeration (4 ± 1 °C) temperatures. Remarkably, LnE + Cu + vD3 exhibited reduced toxicity, causing 29.32% and 34.99% cell death in L6 and RAW264.7 cells respectively, at the highest concentration (50 μg/mL). This underscores the potential valorization of Ayurvedic industry spent materials for diverse industrial applications.

Modeling the Production Process of Lignin Nanoparticles Through Anti-Solvent Precipitation for Properties Prediction

Global warming has recently intensified research interest in renewable polymer chemistry, with significant attention directed towards lignin nanoparticle (LNP) synthesis. Despite progress, LNP industrial application faces challenges: (1) reliance on kraft lignin from declining raw biomass processes, (2) sulfur-rich and condensed lignin use, (3) complex lignin macroparticles to LNP conversion, using harmful and toxic solvents, and, above all, (4) lack of control over the LNP production process (i.e., anti-solvent precipitation parameters), resulting in excessive variability in properties. In this work, eco-friendly LNPs with tailored properties were produced from a semi-industrial organosolv process by studying anti-solvent precipitation variables. Using first a parametric and then a Fractional Factorial Design, predictions of LNP sizes and size distribution, as well as zeta-potential, were derived from a model over beech by-products organosolv lignin, depending on initial lignin concentration (x1, g/L), solvent flow rate (x2, mL/min), antisolvent composition (x3, H2O/EtOH v/v), antisolvent ratio (x4, solvent/antisolvent v/v), and antisolvent stirring speed (x5, rpm). This novel chemical engineering approach holds promise for overcoming the challenges inherent in industrial lignin nanoparticle production, thereby accelerating the valorization of lignin biopolymers for high value-added applications such as cosmetics (sunscreen or emulsion) and medicine (encapsulation, nanocarriers), a process currently constrained by significant limitations.

Superparamagnetic composites of lignin regenerated from ionic liquid solutions for the efficient and selective removal of cationic dyes

Magnetic lignin nanoparticles (MLNs) were prepared by inducing their self-assembly through lignin regeneration in the [N-methyl-2-pyrrolidone][C1-C4 carboxylic acid] ionic liquids ([NMP]ILs), which are low-cost protic ionic liquid. [NMP]ILs are self-assembling solvent that can enhance the adsorption capacity of MLNs to a greater degree than tetrahydrofuran or H2O. Additionally, the anion types of [NMP]IL greatly influence the physiochemical properties of MLNs. The MLNs prepared through self-assembly with [NMP][formate] (MLN/[NMP][For]) exhibited a higher maximum adsorption capacity (134.53 mg/g) than the [NMP]ILs of C2-C4 carboxylate anions. MLN/[NMP][For] demonstrated stable adsorption within a pH range of 6-10 or at high salt concentrations (0.01-0.5 mol/L), retaining over 80 % of its regeneration efficiency after 5 cycles. In addition, MLN/[NMP][For] selectively removed cationic dyes in mixed binary anionic-cationic dye solutions. This work demonstrated the feasibility of preparing magnetic biosorbents with good selectivity and stability though regeneration and by adjusting the anions of ionic liquids.

A high-efficiency strategy for fruit preservation using green, natural raw materials

Straw is an abundant renewable biomass resource material. Lignin contained in straw is a unique natural aromatic compound in nature. At present, it is urgent to find ways to realize the higher value of natural lignin resources. In this study, alkali lignin was separated from rice straw by hydrothermal method in NaOH solution, which was prepared lignin nanoparticles by a simple green anti-solvent method. The obtained lignin nanoparticles had excellent anti-tyrosinase activity (IC50 = 0.329 mg mL-1) and anti-oxidation performance (IC50 = 0.0451 mg mL-1). Meanwhile, through the analysis of tyrosinase inhibition kinetics, it is concluded that the tyrosinase inhibition by lignin nanoparticles belongs to mixed inhibition. The affinity of lignin nanoparticles to the free enzyme is greater than that of enzyme and substrate complex. In addition, lignin nanoparticles were added to chitosan solution for compounding, then the composite films for fruit preservation were prepared by casting method. The experimental results show that the composite membrane can effectively extend the shelf life of fruits, which is expected to achieve a broader application in the field of fruit preservation and food packaging.

Lignin-based flame retardant via sequential purification-nanoparticle formation, and NP coupled chemical modification

A nonhalogenated and ecofriendly flame-retarding material was developed using lignin, one of the main components of lignocellulosic biopolymers. Lignin was purified, dissolved, and formulated as nanoparticles and implemented after processing in an ecofriendly water-based γ-valerolactone (GVL) system at different concentrations. Nitrogen‑phosphorus sequential chemical modification was performed using polyethyleneimine (PEI) and phytic acid (PA), The char residue increased by ≥10 % compared with lignin nanoparticles (LNPs). A 10 wt% lignin-based flame retardant (L-FR) based on the weight of cotton fabric was introduced using a simple dipping method. Compared to existing cotton fabrics, the combustion time of L-FR treated cotton fabrics was reduced by 6.8 s. The maximum flame height was reduced by 5.4 cm, and the charcoal residue increased by 25 %. The flame-retarding mechanism of L-FR involved low-temperature dehydration, thermal decomposition of cellulose by the phosphorus component of PA and generation of expansive gas by the nitrogen component of PEI. These results showed that lignin-based raw material processing, polymer processing, and chemical modification were biomass-based, suggesting that lignin could be converted into an ecofriendly flame retardant, highlighting the feasibility of high-value-added lignin.

Sustainable Nanofluids Constructed from Size-Controlled Lignin Nanoparticles: Application Prospects in Enhanced Oil Recovery

Lignin, a widely available, cost-effective, and structurally stable natural polymer, has recently attracted significant attention due to its diverse potential applications. A promising approach is to prepare lignin nanoparticles (LNPs) as a substitute for conventional nanoparticles to fulfill a variety of functions. In this study, LNPs with controlled size, regular morphology, and excellent dispersibility were synthesized by using industrial alkali lignin. The antisolvent method was employed, utilizing an aqueous solution of the anionic surfactant sodium apolyolefin sulfonate (AOS) as the antisolvent. Subsequently, the prepared LNPs were used to formulate nanofluids in combination with AOS and nonionic surfactant coconut diethanolamide (CDEA). The incorporation of LNPs has significantly enhanced the interfacial activity of the resulting nanofluids, thereby improving their emulsion stabilization, spreading on quartz surfaces, and oil droplet removal capabilities, which establish a strong foundation for the AOS/CDEA/LNPs nanofluid to achieve high performance in enhanced oil recovery (EOR), which was validated through microscopic visual physical model experiments. The quartz crystal microbalance with the dissipation monitoring (QCM-D) technique was employed to investigate the adsorption of surfactants onto quartz surfaces. It was found that the incorporation of LNPs significantly reduces the adsorption loss of surfactants, presenting a potential solution to overcome the challenges associated with surfactant adsorption in chemically enhanced oil recovery (EOR) processes, such as high cost and unreliable efficiency. This study reveals the good performance of LNPs/surfactant nanofluids and provides a potential approach to the advancement of green, sustainable, and intelligent EOR technologies.

Se-incorporated polycaprolactone spherical polyhedron enhanced vitamin B2 loading and prolonged release for potential application in proliferative skin disorders

Development of novel drug vehicles for vitamin B2 (VitB2) delivery is very important for designing controllable release system to improve epidermal growth and bone metabolism. In this work, selenium (Se)-incorporated polycaprolactone (PCL) spherical polyhedrons are successfully synthesized via a single emulsion solvent evaporation method which is utilized to load VitB2 to fabricate cell-responsive Se-PCL@VitB2 delivery systems. Their physicochemical properties are characterized by DLS, SEM, XRD, FTIR, and TGA-DSC. The release kinetics of VitB2 or Se from the samples are investigated in PBS solution (pH = 2.0, 5.0, 7.4, 8.0 and 12.0). The cytocompatibilities are also evaluated with normal BMSC and epidermal HaCat cells. Results exhibit that Se-PCL@VitB2 particles presents spherical polyhedral morphology (approximately (3.25 ± 0.46) μm), negative surface charge (-(54.03 ± 2.94) mV), reduced crystallinity and good degradability. Stability experiments imply that both VitB2 and Se might be uniformly dispersed in PCL matrix. And the incorporation of Se facilely promotes the loading of VitB2. The encapsulation efficiency and loading capacity are (98.42 ± 1.06)% and (76.25 ± 1.27) for Se-PCL@VitB2 sample. Importantly, it exhibits more prolonged release of both VitB2 and Se in neutral PBS solution (pH = 7.4) than other pH conditions. Presumably, the electrostatic interaction between Se, VitB2 and PCL contribute to its release mode. Cell experiments show that Se-PCL@VitB2 presents strong cytotoxicity to HaCat cells mainly due to the cytotoxic effect of Se anions and PCL degradation products. However, it exhibits weak inhibitory effect on BMSC cells. These note that the synthesized Se-PCL@VitB2 particles can be promising drug vehicles for potential application in epidermal proliferative disorders.

Renewable symmetric supercapacitors assembled with lignin nanoparticles-based thin film electrolyte and carbon aerogel electrodes

Lignin as a natural biopolymer is becoming increasingly in demand due to its eco-friendly properties, while lignin-based electrolyte with high conductivity and reliable durability for applications in supercapacitors is still challenging. Herein, a facile method to prepare lignin nanoparticles (LNPs)-based solid electrolyte thin film (LF) was proposed through chemical cross-linking reaction. The fabricated LF exhibited a distinctive spongy porous structure with the ionic conductivity of 3.26 mS cm-1, demonstrating the exceptional flexibility and favorable mechanical properties. Moreover, the assembly of all-LNPs-based symmetric supercapacitor (SSC) devices was achieved using LF electrolyte and LCA electrodes for the first time, confirming the LF3 electrolyte superior to commercial cellulose separator in capacitive behaviour. This SSC device exhibited a specific capacitance of 122.7 F g-1 at 0.5 A g-1 and the maximum energy density of 17.04 W h kg-1. Furthermore, the incorporation of sodium alginate (SA) significantly enhanced the ionic conductivity of SA/LF3 electrolyte, and the resulting SSC device delivered a higher specific capacitance of 174.5 F g-1 at 0.5 A g-1 and the maximum energy and power densities of 24.24 W h kg-1 and 5023 W kg-1, respectively. This study proposes a promising approach for sustainable utilization of lignin in energy storage applications.

A comprehensive review on polylactic acid/lignin composites - Structure, synthesis, performance, compatibilization, and applications

Today, the world is facing a great problem of plastic pollution due to its non-degradable nature. Alternatively, polylactic acid (PLA), a bio-based and biodegradable polymer, is emerging as a promising substitute for conventional, non-biodegradable plastics. However, its high cost, limited properties, and single functionality hinder its wide application. Lignin, a natural and sustainable biomass derived from plant cell walls, has become a promising filler for PLA. The integration of lignin into PLA composites holds the potential to realize the trifecta of low cost, high performance, and multifunctional properties while maintaining the principles of biodegradation and sustainability. However, the poor compatibility between PLA and lignin severely affects their overall performance, which creates a major challenge for the development of PLA/lignin composites. In recent years, a significant of advancements have been achieved in addressing this challenge. In this review, we provide a systematic insight into PLA/lignin composites, focusing on numerous compatibilization strategies including physical addition and chemical modification, and the progress on the structural characteristics, synthesis methods, performance improvements brought by lignin, and multiple applications. Finally, the existing problems and developmental direction of PLA/lignin composites are discussed. We believe that this review can be useful for future research prospects and industrial applications.

Lignin Nanoparticles: Transforming Environmental Remediation

In the face of escalating environmental challenges driven by human activities, the quest for innovative solutions to counter pollution, contamination, and ecological degradation has gained paramount importance. Traditional approaches to environmental remediation often fall short in addressing the complexity and scale of modern-day environmental problems. As industries transition towards sustainable paradigms, the exploration of novel materials and technologies becomes crucial. Lignin nanoparticles have emerged as a promising avenue of exploration in this context. Once considered a mere byproduct, lignin's unique properties and versatile functional groups have propelled it to the forefront of environmental remediation research. This review paper delves into the resurgence of lignin from an environmental perspective, examining its pivotal role in carbon cycling and its potential to address various environmental challenges. The paper extensively discusses the synthesis, properties, and applications of lignin nanoparticles in diverse fields such as water purification and soil remediation. Moreover, it highlights the challenges associated with nanoparticle deployment, ranging from Eco toxicological assessments to scalability issues. Multidisciplinary collaboration and integration of research findings with real-world applications are emphasized as critical factors for unlocking the transformative potential of lignin nanoparticles. Ultimately, this review underscores lignin nanoparticles as beacons of hope in the pursuit of cleaner, healthier, and more harmonious coexistence between humanity and nature through innovative environmental remediation strategies.

Sprayed water-based lignin colloidal nanoparticle-cellulose nanofibril hybrid films with UV-blocking ability

In the context of global climate change, the demand for new functional materials that are sustainable and environmentally friendly is rapidly increasing. Cellulose and lignin are the two most abundant raw materials in nature, and are ideal components for functional materials. The hydrophilic interface and easy film-forming properties of cellulose nanofibrils make them excellent candidates for natural biopolymer templates and network structures. Lignin is a natural UV-shielding material, as it contains a large number of phenolic groups. In this work, we have applied two routes for spray deposition of hybrid films with different laminar structures using surface-charged cellulose nanofibrils and water-based colloidal lignin particles. As the first route, we prepare stacked colloidal lignin particles and cellulose nanofibrils hybrid film through a layer-by-layer deposition. As the second route, we spray-deposite premixed colloidal lignin particles and cellulose nanofibrils dispersion to prepare a mixed hybrid film. We find that cellulose nanofibrils act as a directing agent to dominate the arrangement of the colloidal lignin particles in a mixed system. Additionally, cellulose nanofibrils eliminate the agglomerations and thus increase the visible light transparency while retaining the UV shielding ability. Our research on these colloidal lignin and cellulose nanofibril hybrid films provides a fundamental understanding of using colloidal lignin nanoparticles as functional material on porous cellulose-based materials, for example on fabrics.

Sodium-Alginate-Doped Lignin Nanoparticles for PBAT Composite Films to Dually Enhance Tensile Strength and Elongation Performance with Functionality

It is a formidable challenge in thermoplastic/lignin composites to simultaneously boost tensile strength and elongation performance due to the rigidity of lignin. To address this issue, sodium-alginate-doped lignin nanoparticles (SLNPs) were prepared by combining solvent exchange and a coprecipitation method and used as an eco-friendly filler for poly(butylene adipate-co-terephthalate) (PBAT). The results indicated that the 1% polyanionic sodium alginate solution contributed to the formation of SLNP in lignin/THF solution. SLNP with a mean hydrodynamic diameter of ~500 nm and a Zeta potential value of -19.2 mV was obtained, indicating more hydrophobic lignin nanoparticles and a smaller number of agglomerates in SLNP suspension. Only 0.5 wt% SLNP addition improved the yield strength, tensile strength, and elongation at break by 32.4%, 31.8%, and 35.1% of the PBAT/SLNP composite films, respectively. The reinforcing effect resulted from the rigid aromatic structure of SLNP, whereas the enhanced elongation was attributed to the nanostructural feature of SLNP, which may promote boundary cracking. Additionally, the PBAT/SLNP composite films displayed excellent ultraviolet (UV) resistance with a UV shielding percentage near 100% for UVB and more than 75% for UVA, respectively. The addition of SLNP hindered water vapor, enhancing the moisture barrier properties. Overall, this study provides an effective strategy to eliminate the decrement in elongation performance for PBAT/lignin composites and suggest they are good candidates to be extensively utilized.

Natural lignin nanoparticles target tumor by saturating the phagocytic capacity of Kupffer cells in the liver

Ligand-receptor recognition serves as the fundamental driving force for active targeting, yet it is still constrained by off-target effects. Herein, we demonstrate that circumventing or blocking the mononuclear phagocyte system (MPS) are both viable strategies to address off-target effects. Naturally derived lignin nanoparticles (LNPs) show great potential to block MPS due to its good stability, low toxicity, and degradability. We further demonstrate the impact of LNPs dosage on in vivo tumor targeting and antitumor efficacy. Our results show that a high dose of LNPs (300 mg/kg) leads to significant accumulation at the tumor site for a duration of 14 days after intravenous administration. In contrast, the low-dose counterparts (e.g., 50, 150 mg/kg) result in almost all LNPs accumulating in the liver. This discovery indicates that the liver is the primary site of LNP capture, leaving only the surplus LNPs the chance to reach the tumor. In addition, although cell membrane-engineered LNPs can rapidly penetrate tumors, they are still prone to capture by the liver during subsequent circulation in the bloodstream. Excitingly, comparable therapeutic efficacy is obtained for the above two strategies. Our findings may offer valuable insights into the targeted delivery of drugs for disease treatment.

Recent updates on green synthesis of lignin nanoparticle and its potential applications in modern biotechnology

Lignin is a complex of organic polymers that are abundantly present in the plant cell wall which considered of emerging substrates for various kinds of value-added industrial products. Lignin has potential use for the production of green nanomaterials, which exhibit improved or different properties corresponding to their parent polymers. Nano lignin has received significant interest in recent years due to its applications in numerous fields. Lignin, the abundant and limited functionality has challenges for its potential uses. Creating advanced functional lignin-derived material like lignin nanoparticles (LNPs) which significantly alter the biological process has great potential for its applications. In the fields of biotechnology, several lignin extraction processes from various raw materials and diverse synthesis techniques, including acid precipitation, dialysis, solvent shifting/solvent exchange, antisolvent precipitation, homogenization, water-in-oil (W/O) microemulsion, ultra-sonication, interfacial crosslinking, polymerization, and biological pathway can be employed to produce LNPs. The scientific community has recently become more concerned about the transformation of lignin to lignin nanomaterials, including nanoparticles, nanocapsules, nanofibers, nanotubes, and nanofilms. Recent research has shown that lignin nanoparticles (LNPs) are: non-toxic at adequate amounts (both in vitro and in vivo), are economical, and can be biodegradable by bacteria and fungi. In promising studies, LNPs have been investigated for their potential applications in gene delivery systems, drug carriers, biocatalysts, tissue engineering, heavy metal absorbers, encapsulation of molecules, supercapacitors, hybrid nanocomposites, and other applications. This current review addresses the recent advances in the synthesis of LNPs, their advanced application in different areas, future perspectives, and challenges associated with lignin-based nanomaterials.

Overcoming Challenges of Lignin Nanoparticles: Expanding Opportunities for Scalable and Multifunctional Nanomaterials

ConspectusThe increasing demand for polymeric materials derived from petroleum resources, along with rising concerns about climate change and global plastic pollution, has driven the development of biobased polymeric materials. Lignin, which is the second most abundant biomacromolecule after cellulose, represents a promising renewable raw material source for the preparation of advanced materials. The lucrative properties of lignin include its high carbon content (>60 atom %), high thermal stability, biodegradability, antioxidant activity, absorbance of ultraviolet radiation, and slower biodegradability compared to other wood components. Moreover, the advent of lignin nanoparticles (LNPs) over the last ten years has circumvented many well-known shortcomings of technical lignins, such as heterogeneity and poor compatibility with polymers, thereby unlocking the great potential of lignin for the development of advanced functional materials.LNPs stand out owing to their well-defined spherical shape and excellent colloidal stability, which is due to the electrostatic repulsion forces of carboxylic acid and phenolic hydroxyl groups enriched on their surface. These forces prevent their aggregation in aqueous dispersions (pH 3-9) and provide a high surface area to mass ratio that has been exploited to adsorb positively charged compounds such as enzymes or polymers. Consequently, it is not surprising that LNPs have become a prominent player in applied research in areas such as biocatalysis and polymeric composites, among others. However, like all ventures of life, LNPs also face certain challenges that limit their potential end-uses. Solvent instability remains the most challenging aspect due to the tendency of these particles to dissolve or aggregate in organic solvents and basic or acidic pH, thus limiting the window for their chemical functionalization and applications. In addition, the need for organic solvent during their preparation, the poor miscibility with hydrophobic polymeric matrices, and the nascent phase regarding their use in smart materials have been identified as important challenges that need to be addressed.In this Account, we recapitulate our efforts over the past years to overcome the main limitations mentioned above. We begin with a brief introduction to the fundamentals of LNPs and a detailed discussion of their associated challenges. We then highlight our work on: (i) Preparation of lignin-based nanocomposites with improved properties through a controlled dispersion of LNPs within a hydrophobic polymeric matrix, (ii) Stabilization of LNPs via covalent (intraparticle cross-linking) and noncovalent (hydration barrier) approaches, (iii) The development of an organic-solvent-free method for the production of LNPs, and (iv) The development of LNPs toward smart materials with high lignin content. Finally, we also offer our perspectives on this rapidly growing field.

The Impact of Lignin Biopolymer Sources, Isolation, and Size Reduction from the Macro- to Nanoscale on the Performances of Next-Generation Sunscreen

In recent years, concerns about the harmful effects of synthetic UV filters on the environment have highlighted the need for natural sun blockers. Lignin, the most abundant aromatic renewable biopolymer on Earth, is a promising candidate for next-generation sunscreen due to its inherent UV absorbance and its green, biodegradable, and biocompatible properties. Lignin's limitations, such as its dark color and poor dispersity, can be overcome by reducing particle size to the nanoscale, enhancing UV protection and formulation. In this study, 100-200 nm lignin nanoparticles (LNPs) were prepared from various biomass by-products (hardwood, softwood, and herbaceous material) using an eco-friendly anti-solvent precipitation method. Pure lignin macroparticles (LMPs) were extracted from beech, spruce, and wheat straw using an ethanol-organosolv treatment and compared with sulfur-rich kraft lignin (KL). Sunscreen lotions made from these LMPs and LNPs at various concentrations demonstrated novel UV-shielding properties based on biomass source and particle size. The results showed that transitioning from the macro- to nanoscale increased the sun protection factor (SPF) by at least 2.5 times, with the best results improving the SPF from 7.5 to 42 for wheat straw LMPs and LNPs at 5 wt%. This study underscores lignin's potential in developing high-quality green sunscreens, aligning with green chemistry principles.

Nano-enabled smart and functional materials toward human well-being and sustainable developments

Fabrication and operation on increasingly smaller dimensions have been highly integrated with the development of smart and functional materials, which are key to many technological innovations to meet economic and societal needs. Along with researchers worldwide, the Waterloo Institute for Nanotechnology (WIN) has long realized the synergetic interplays between nanotechnology and functional materials and designated 'Smart & Functional Materials' as one of its four major research themes. Thus far, WIN researchers have utilized the properties of smart polymers, nanoparticles, and nanocomposites to develop active materials, membranes, films, adhesives, coatings, and devices with novel and improved properties and capabilities. In this review article, we aim to highlight some of the recent developments on the subject, including our own research and key research literature, in the context of the UN Sustainability development goals.

Self-Formation of Lignin Particles Through Melt-Extrusion for Active Biodegradable Food Packaging

This study presents a method for the self-formation of lignin particles within a polylactic acid (PLA) matrix during melt-extrusion, eliminating the need for separation and drying steps typically associated with submicro-size lignin particles. This method effectively mitigates the problem of agglomeration often associated with the drying step. Softwood kraft lignin, guaiacyl lignin (GL-lignin), was dissolved in low-molecular-weight poly(ethylene glycol) (PEG) and was introduced into a twin-screw extruder using a liquid feeder. Lignin particles within a particle size range of 200-500 nm were observed in the extrudate of the PLA/PEG/GL-lignin composites. PLA/PEG/GL-lignin composite films were produced through blown film extrusion. These composite films demonstrated superior ultraviolet (UV)-barrier and antioxidant properties compared to neat PLA films, with optical and mechanical characteristics comparable to those of neat PLA. Moreover, migration values of the composite films in various food simulants were below regulatory limits, suggesting their potential for food packaging applications. This self-formation process offers a promising approach for utilizing lignin for PLA applications.

Preparation and Characterization of Lignin Nanoparticles from Different Plant Sources

This article presents new research on producing lignin nanoparticles (LNPs) using the antisolvent nanoprecipitation method. Acetone (90%) served as the lignin solvent and water (100%) as the antisolvent, using five types of lignins from various sources. Comprehensive characterization techniques, including NMR, GPC, FTIR, TEM, and DLS, were employed to assess both lignin and LNP properties. The antioxidant activity of the LNPs was evaluated as well. The results demonstrated the successful formation of spherical nanoparticles below 100 nm with initial lignin concentrations of 1 and 2%w/v. The study highlighted the crucial role of lignin purity in LNP formation and colloidal stability, noting that residual carbohydrates adversely affect efficiency. This method offers a straightforward, environmentally friendly approach using cost-effective solvents, applicable to diverse lignin sources. The innovation of this study lies in its demonstration of a cost-effective and eco-friendly method to produce stable, nanometric-sized spherical LNPs. These LNPs have significant potential as reinforcement materials due to their reinforcing capability, hydrophilicity, and UV absorption. This work underscores the importance of starting material purity for optimizing the process and achieving the desired nanometric dimensions, marking a pioneering advancement in lignin-based nanomaterials.

Lipase-Responsive Lignin Composite Nanoparticles for the Delivery of Insoluble Bioactives

Low solubility and chemical instability are the main problems with insoluble bioactives. Lignin, with its exceptional biological properties and amphiphilicity, holds promise as a delivery system material. In this study, glycerol esters were incorporated into alkali lignin (AL) through ether and ester bonds, resulting in the successful synthesis of three hydrophobically modified alkali lignins (AL-OA, AL-OGL, and AL-SAN-OGL). Subsequently, lignin composite nanoparticles (LNPs@BC) encapsulating β-carotene were prepared using antisolvent and sonication techniques. The encapsulation rates were determined to be 37.69 ± 2.21%, 84.01 ± 5.55%, 83.82 ± 5.23%, and 83.11 ± 5.85% for LNP@BC-1, LNP@BC-2, LNP@BC-3, and LNP@BC-4, respectively, with AL, AL-OA, AL-OGL, and AL-SAN-OGL serving as the wall materials under optimized preparation conditions. The antioxidant properties and UV-absorbing capacity of the four lignins were characterized, demonstrating their efficacy in enhancing the oxygen and photostability of β-carotene. Following 6 h of UV irradiation, LNP@BC-4 exhibited a retention rate of 83.03 ± 2.85% for β-carotene, while storage under light-protected conditions at 25 °C for 7 days retained 73.33 ± 7.62% of β-carotene. Furthermore, the encapsulated β-carotene demonstrated enhanced thermal and storage stability. In vitro release experiments revealed superior stability of LNPs@BC in simulated gastric fluid (SGF), with β-carotene retention exceeding 77% in both LNP@BC-3 and LNP@BC-4. LNP@BC-4 exhibited the highest bioaccessibility in simulated intestinal fluid (SIF) at 46.96 ± 0.80%, that LNP@BC-1 only achieved 10.87 ± 0.90%. The enzymatic responsiveness of AL-OGL and AL-SAN-OGL was confirmed. Moreover, LNPs@BC exhibited no cytotoxicity toward L929 cells and demonstrated excellent hemocompatibility. In summary, this study introduces a novel enzyme-responsive modified lignin that has promising applications in the fields of food, biomedicine, and animal feed.

Optimization of lignin precipitation from black liquor using organic acids and its valorization by preparing lignin nanoparticles

This work focuses on the precipitation of lignin from kraft black liquor (BL) along with its valorization into lignin nanoparticles (LNP). Two organic acids namely, acetic acid, and lactic acid were used for the precipitation of lignin as an alternative to sulfuric acid. An optimization study was carried out to determine the effect of three key variables, namely acid type, temperature, and pH, on the isolation yield and purity of lignin. The study showed that all factors primarily influenced the lignin yield, while the purity of precipitated lignin varied only around 1 % between minimum to maximum purity. Further, the acid precipitation method was selected for the preparation of LNP. The study aimed to observe the effect of pH, lignin concentration, and surfactant concentration over the properties of the prepared nanoparticles. The results showed that a smaller nanoparticle size and maximization of phenolic content was achieved with a lignin concentration of 35 mg/mL, a surfactant concentration of 10 % (w/w lignin), and a pH of 5. Additionally, the antibacterial activity of LNPs against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa bacteria was evaluated. The results showed only minor activity against Staphylococcus aureus. Overall, the study demonstrates the potential method for precipitation and valorization of lignin through the production of LNP with desirable properties.

High performance polyvinyl alcohol/lignin fibers with excellent mechanical and water resistance properties

To address the shortcoming of Polyvinyl alcohol (PVA) fibers for food or medical packaging materials including low mechanical strength and poor water resistance, lignin (LN) was used as raw material, acetone/H2O as solvent to self-assemble into lignin nanoparticles (LNP) by adverse solvent precipitation approach, and then PVA/LNP composite fibers with different LNP contents were fabricated successfully by wet and dry spinning. Herein, vast hydrophilic hydroxyl groups in PVA decreased owing to the hydrogen bond between LN and PVA, Especially, with only 0.5 wt% loading of LNP into the PVA/LNP fibers, the diameter was 94.4 dtex, tensile strength was 10.1 cN/dtex (1279.8 MPa), initial modulus was 94.7 cN/dtex (12.0 GPa), the crystallinity was 56.7 %, the orientation was 97.1 %, and water contact angle was 103.1°. Compared with pure PVA fibers, the tensile strength of PVA/LNP-0.5 fibers was increased by 44.2 % and the contact angle was increased 37°. This work provides novel insights into obtaining lignin-reinforced PVA composite fibers with strong mechanical properties and excellent water resistance properties, indicating the potential of the PVA/LNP fibers for food or medical packaging application.

IPN based hydrogels for in-vivo wound dressings; catalytic wound healing dynamics and isothermal adsorption models

Interpenetrating network (IPN) methacrylated chitosan or methacrylated flaxseed gum based hydrogels have been utilized to make outstanding in-vivo wound dressings. The photopolymerization process was accomplished in presence of Eosin-Y photoinitiator with average exposure time of 13-14 s for gelation. Spectroscopic structural investigations of 1H NMR. ATR-FTIR, TGA, and AFM techniques were used. In-vitro hemolysis test provided evidence of no cytotoxicity in both hydrogels observed. The in-vivo wound dressings were monitored for five mice coated with each hydrogel and another uncoated five mice for control (self-healing). All measurements were performed in quintuplicate (n = 5) and expressed as mean ± SD values. In wound healing dynamics, our data confirmed that wound healing pass through two stages; hemostasis and inflammation for stage 1, and proliferation and remodeling for stage 2. It also provided evidence of 1st order kinetics with descending rate of healing. Consequently, catalytic role of hydrogels in wound healing was checked via half-life (δ) and negative change of activation energy values (ΔEa). Various isothermal adsorption models demonstrated spontaneous and high binding affinities of hydrogels. It also confirmed the two-stage healing process in presence of hydrogels. Conclusively, the outstanding properties of the two hydrogels suggest their potential applications in treating venous ulcers and diabetic wound healing dressings.

Synthesis of novel nonsteroidal anti-inflammatory galloyl β-sitosterol-loaded lignin-capped Ag-based drug

Biocompatible anti-inflammatory lignin-capped Ag (LCAg) nanoparticles (NPs) were synthesized for the delivery of galloyl β-sitosterol (Galloyl-BS). β-Sitosterol (BS) is effective against inflammatory responses, like cancer-induced inflammations. BS was modified via gallic acid esterification to enhance its anti-inflammatory potential. LCAg NPs were synthesized by a green method and loaded with galloyl-BS. For comparison, pure BS was also loaded onto LCAg NPs in a separate assembly. The antioxidant potential of Galloyl-BS was greater (IC50 177 µM) than pure BS. Materials were characterized by FT-IR, SEM, XRD, and Zeta potential. Using UV-Vis spectroscopy, drug release experiments were performed by varying pH, time, concentration, and temperature. Maximum drug release was observed after 18 h at pH 6 and 40 °C. Galloyl-BS showed improved drug loading efficiency, release %age, and antioxidant activity compared to pure BS when loaded onto LCAg NPs. DLCAg exhibited excellent anti-inflammatory activity in rat models. These findings indicate that galloyl-BS (drug)-loaded LCAg (DLCAg) NPs have the potential as an anti-inflammatory agent without any prior release and scavenging in normal cells.

Lignin-xylan nanospheres prepared by green and quick method from lignocellulose and used as additive in PVA films

Lignin, as an amorphous three-dimensional aromatic polymer, was able to self-assemble into lignin nanoparticles (LNPs) to realize valorization of lignin. Here, lignin-xylan extractives were extracted from grape seed (GS) and poplar by acidic THF at room temperature, and effectively produced lignin-xylan nanospheres via spin evaporation. The morphology and chemical properties of nanospheres were determined by its natural origins, consequently influencing its application. For the lignin-xylan extractive from grape seed, the lignin was composed of guaiacyl (G) and p-hydroxylphenyl (H) units and the hollowed nanospheres (GS-LNPs) with 362.72 nm diameter was produced. The extractive from poplar was composed of G-syringyl (S) typed lignin (80.30 %) and xylan (12.33 %), that can assemble into LNPs with smaller size (229.87 nm), better PDI (0.1), and light color. The hybrid particles showed the qualities of lignin and xylan, that properties led to the LNPs@PVA composite films with UV-blocking capability, strong mechanical strength and hydrophobicity, and transparency ability of visible light. P-LNPs showed better performance as the film additives, due to its lower particles size and high content of unconjugated -OH from xylan. Xylan was significant in the composite films, and lowering the xylan content resulted in the decrease of the composite film's mechanical properties and hydrophobicity.

Understanding Lignin Dissolution with Urea and the Formation of a Lignin Nano-Aggregate: A Multiscale Approach

This study employs a combined computational and experimental approach to elucidate the mechanisms governing the interaction between lignin and urea, impacting lignin dissolution and subsequent aggregation behavior. Molecular dynamics (MD) simulations reveal how the urea concentration and temperature influence lignin conformation and interactions. Higher urea concentrations and temperatures promote lignin dispersion by disrupting intramolecular interactions and enhancing solvation. Density functional theory (DFT) calculations quantitatively assess the interaction energy between lignin and urea, supporting the findings from MD simulations. Anti-solvent precipitation demonstrates that increasing the urea concentration hinders the self-assembly of lignin nanoclusters. The findings provide valuable insights for optimizing lignin biorefinery processes by tailoring the urea concentration and temperature for efficient extraction and dispersion. Understanding the influence of urea on lignin behavior opens up avenues for designing novel lignin-based materials with tailored properties. This study highlights the potential for the synergetic application of MD simulations and DFT calculations to unravel complex material interactions at the atomic level.

Modulation of Methoxyfenozide Release from Lignin Nanoparticles Made of Lignin Grafted with PCL by ROP and Acylation Grafting Methods

An efficient and sustainable agriculture calls for the development of novel agrochemical delivery systems able to release agrochemicals in a controlled manner. This study investigated the controlled release of the insecticide methoxyfenozide (MFZ) from lignin (LN) nanoparticles (LNPs). LN-grafted poly(ε-caprolactone) (LN-g-PCL) polymers were synthesized using two grafting methods, ring-opening polymerization (ROP)(LN-g-PCLp) and acylation reaction (LN-g-PCLa), creating polymers capable of self-assembling into nanoparticles of different properties, without surfactants. The LN-g-PCLp polymers exhibited a degree of polymerization (DP) from 22 to 101, demonstrating enhanced thermal stability after LN incorporation. LNPs loaded with MFZ exhibited a spherical core-shell structure with a hydrophilic LN outer layer and hydrophobic PCL core, with sizes affected by grafting methods and DP. LNPs controlled MFZ release, displaying variation in release profiles depending on the grafting methodology used, LN-g-PCLp DP, and temperature variations (23 to 30 °C). LNPs formulated with LN-g-PCLa showed a cumulative release of MFZ of 36.78 ± 1.23% over 196 h. Comparatively, increasing the DP of the LN-g-PCLp polymers, a reduction of the LNPs release rate from 92.39 ± 1.46% to 70.59 ± 2.40% was achieved within the same time frame. These findings contribute to identifying ways to modulate the controlled release of agrochemicals by incorporating them in renewable-based LNPs.

Nanotechnology in wood science: Innovations and applications

Application of nanomaterials is gaining tremendous interest in the field of wood science and technology for value addition and enhancing performance of wood and wood-based composites. This review focuses on the use of nanomaterials in improving the properties of wood and wood-based materials and protecting them from weathering, biodegradation, and other deteriorating agents. UV-resistant, self-cleaning (superhydrophobic) surfaces with anti-microbial properties have been developed using the extraordinary features of nanomaterials. Scratch-resistant nano-coatings also improve durability and aesthetic appeal of wood. Moreover, nanomaterials have been used as wood preservatives for increasing the resistance against wood deteriorating agents such as fungi, termites and borers. Wood can be made more resistant to ignition and slower to burn by introducing nano-clays or nanoparticles of metal-oxides. The use of nanocellulose and lignin nanoparticles in wood-based products has attracted huge interest in developing novel materials with improved properties. Nanocellulose and lignin nanoparticles derived/synthesized from woody biomass can enhance the mechanical properties such as strength and stiffness and impart additional functionalities to wood-based products. Cellulose nano-fibres/crystals find application in wide areas of materials science like reinforcement for composites. Incorporation of nanomaterials in resin has been used to enhance specific properties of wood-based composites. This review paper highlights some of the advancements in the use of nanotechnology in wood science, and its potential impact on the industry.

Lignin derivatives-based hydrogels for biomedical applications

Recently, numerous studies have been conducted on renewable polymers derived from different natural sources, exploring their suitability for diverse biomedical applications. Lignin as one of the main components of lignocellulosic has garnered significant attention as a promising alternative to petroleum-based polymers. This interest is primarily due to its cost-effectiveness, biocompatibility, eco-friendly nature, as well as its antioxidant and antimicrobial properties. These characteristics could be more beneficial when incorporating lignin into the formulation of value-added products. Although lignin has a chemical structure that is suitable for various applications, these characteristics require modifications to guarantee that the resultant materials display the desired biological, chemical, and physical properties when applied in the creation of biodegradable hydrogels, particularly for biomedical purposes. This study delineates the recent modification approaches that have been employed in the creation of lignin-based hydrogels. These strategies encompass both chemical and physical interactions with other polymers. Additionally, this review encompasses an examination of the current applications of lignin hydrogels, spanning their use as scaffolds for tissue engineering, carriers for pharmaceuticals, materials for wound dressings and biosensors, and elements in flexible and wearable electronics. Finally, we delve into the challenges and constraints associated with these materials, discuss the necessary steps required to attain the appropriate properties for the development of innovative lignin-based hydrogels, and derive conclusions based on the presented findings.

Phospholipase D Immobilization on Lignin Nanoparticles for Enzymatic Transformation of Phospholipids

Lignin nanoparticles (LNPs) are promising components for various materials, given their controllable particle size and spherical shape. However, their origin from supramolecular aggregation has limited the applicability of LNPs as recoverable templates for immobilization of enzymes. In this study, we show that stabilized LNPs are highly promising for the immobilization of phospholipase D (PLD), the enzyme involved in the biocatalytic production of high-value polar head modified phospholipids of commercial interest, phosphatidylglycerol, phosphatidylserine and phosphatidylethanolamine. Starting from hydroxymethylated lignin, LNPs were prepared and successively hydrothermally treated to obtain c-HLNPs with high resistance to organic solvents and a wide range of pH values, covering the conditions for enzymatic reactions and enzyme recovery. The immobilization of PLD on c-HLNPs (PLD-c-HLNPs) was achieved through direct adsorption. We then successfully exploited this new enzymatic preparation in the preparation of pure polar head modified phospholipids with high yields (60-90 %). Furthermore, the high stability of PLD-c-HLNPs allows recycling for a number of reactions with appreciable maintenance of its catalytic activity. Thus, PLD-c-HLNPs can be regarded as a new, chemically stable, recyclable and user-friendly biocatalyst, based on a biobased inexpensive scaffold, to be employed in sustainable chemical processes for synthesis of value-added phospholipids.

Preparation of uniform lignin/titanium dioxide nanoparticles by confined assembly: A multifunctional nanofiller for a waterborne polyurethane wood coating

We report a facile synthesis for lignin/titanium dioxide (TiO2) nanoparticles (LT NPs) at room temperature by confining assembly of lignin macromolecules. The LT NPs had a uniform nanosize distribution (average diameter ∼ 68 nm) and were directly employed as multifunctional nanofillers to reinforce a waterborne polyurethane wood coating (WBC). X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy revealed the mechanism by which formed TiO2 confined lignin assembly. The LT NPs considerably increased the tensile strength of a WBC film from 16.3 MPa to 28.1 MPa. The WBC-LT NPs exhibited excellent ultraviolet (UV) A and UVB blocking performances of 87 % and 98 %, respectively, while maintaining 94 % transmittance in the visible region. Incorporating LT NPs into the WBC enhanced the coating performance (the hardness, adhesion, and abrasion resistance) on wood substrates. A quantitative color and texture analysis revealed that the LT NPs increased the decorativeness of actual wooden products. After nearly 1800 h of UV irradiation, wood coated with the WBC-LT NPs exhibited good color stability, where the original color remained unchanged or even became brighter. In this study, value-added valorization of lignin is enabled by using organic-inorganic nanofillers and insights are gained into developing multifunctional WBCs.

A review on the calculation and application of lignin Hansen solubility parameters

Hansen solubility parameters (HSPs) play a critical role in the majority of processes involving lignin depolymerization, separation, fractionation, and polymer blending, which are directly related to dissolution properties. However, the calculation of lignin HSPs is highly complicated due to the diversity of sources and the complexity of lignin structures. Despite their important role, lignin HSPs have been undervalued, attracting insufficient attention. This review summarizes the calculation methods for lignin HSPs and proposes a straightforward method based on lignin subunits. Furthermore, it highlights the crucial applications of lignin HSPs, such as identifying ideal solvents for lignin dissolution, selecting suitable solvents for lignin depolymerization and extraction, designing green solvents for lignin fractionation, and guiding the preparation of lignin-based composites. For instance, leveraging HSPs to design a series of solvents could potentially achieve sequential controllable lignin fractionation, addressing issues of low value-added applications of lignin resulting from poor homogeneity. Notably, HSPs serve as valuable tools for understanding the dissolution behavior of lignin. Consequently, we expect this review to be of great interest to researchers specializing in lignin and other macromolecules.