Innovative production of lignin nanoparticles using deep eutectic solvents for multifunctional nanocomposites

Excellent facile fabrication of PVA and lignin nanoparticles from wheat straw after novel DES-THF pretreatment

The utilization of environmental friendly and renewable materials has received increasing attention recently. Lignin nanospheres (LNPs) prepared from recovered lignin and residual lignin after DESs and DESs-THF pretreatment were obtained by self-assembly in the present research. Then, films were prepared by incorporating them into polyvinyl alcohol (PVA) solution. The properties of various films were characterized and compared. Results showed that as the LNPs content increased, the UV blocking capacity of the films was gradually enhanced than PVA film. The DES-THF films showed better antioxidant properties up to 69 % due to higher phenolic hydroxyl content. The hydrophobicity of films incorporated with DESs-THF pretreated lignin was consistently better than that of DES pretreated. DES-THF-M films showed a higher Tmax than that of DES-M films, resulting in better thermal stability. Moreover, DES-THF-L films are lighter in color due to a lower degree of condensation, which is favorable to subsequent applications. The incorporation of LNPs improved mechanical and antioxidant properties, thermal stability, and UV shielding ability of PVA films, especially lignin after DES-THF pretreatment. In conclusion, the prepared PVA/LNPs composite films possessed good functional properties that make them potential for packaging materials.

Biodegradable, Strong, and Hydrophobic Regenerated Cellulose Films Enriched with Esterified Lignin Nanoparticles

The scientific community is pursuing significant efforts worldwide to develop environmentally viable film materials from biomass, particularly transparent, high-performance regenerated cellulose (RC) films, to replace traditional plastics. However, the inferior mechanical performance and hydrophilic nature of RC films are generally not suitable for use as a substitute for plastics in practical applications. Herein, lignin homogenization is used to synthesize high-performance composite films. The esterified lignin nanoparticles (ELNPs) with dispersible and binding advantages are prepared through esterification and nanometrization. In the presence of ELNPs, RC films exhibit a higher tensile strength (110.4 MPa), hydrophobic nature (103.6° water contact angle, 36.6% water absorption at 120 min, and 1.127 × 10-12 g cm cm-2 s-1 Pa-1 water vapor permeability), and exciting optical properties (high visible and low ultraviolet transmittance). The films further display antioxidant activity, oxygen barrier ability, and thermostability. The films completely biodegrade at 12 and 30% soil moisture. Overall, this study offers new insights into lignin valorization and regenerated cellulose composite films as novel bioplastic materials.

Monte Carlo, molecular dynamic, and experimental studies of the removal of malachite green using g-C3N4/ZnO/Chitosan nanocomposite in the presence of a deep eutectic solvent

Deep-eutectic solvents (DES) have emerged as promising candidates for preparing nanocomposites. In this study, a DES-based graphitic carbon nitride (g-C3N4)/ZnO/Chitosan (Ch) nanocomposite was synthesized to remove malachite green (MG) dye from water. The DES was prepared by mixing and heating citric acid as a hydrogen bond acceptor and lactic acid as a hydrogen bond donor. This is the first report of the removal of MG using DES-based nanocomposites. Experiments on kinetics and isothermal adsorption were conducted to systematically explore the adsorption performances of nanocomposite toward dye. At 25 °C, the highest adsorption performance was obtained with alkaline media (>90 % removal). The greatest adsorption capacity (qm) was 59.52 mg g-1 at conditions (30 mg L-1 MG solution, pH 9, 3 mg nanocomposite per 10 mL of MG solution, 25 °C, 150 rpm, and 150 min) based on the calculation from the best-fitting isotherm model (Langmuir). The adsorption process was most appropriately kinetically described by the PSO model. The Monte Carlo (MC) and molecular dynamic (MC) results are correlated with experimental findings to validate the theoretical predictions and enhance the overall understanding of the adsorption process. Electronic structure calculations reveal the nature of interactions, including hydrogen bonding and electrostatic forces, between the nanocomposite and MG molecules.

A novel seawater hydrothermal-deep eutectic solvent pretreatment enhances the production of fermentable sugars and tailored lignin nanospheres from Pinus massoniana

Lignocellulose biorefinery depended on effective pretreatment strategies is of great significance for solving the current global crisis of ecosystem and energy security. This study proposes a novel approach combining seawater hydrothermal pretreatment (SHP) and microwave-assisted deep eutectic solvent (MD) pretreatment to achieve an effective fractionation of Pinus massoniana into high value-added products. The results indicated that complex ions (Mg2+, Ca2+, and Cl-) in natural seawater served as Lewis acids and dramatically promoted the depolymerization of mannose and xylan into oligosaccharides with 40.17 % and 75.43 % yields, respectively. Subsequent MD treatment realized a rapid and effective lignin fractionation (~90 %) while retaining cellulose. As a result, the integrated pretreatment yielded ~85 % of enzymatic glucose, indicating an eightfold increase compared with untreated pine. Because of the increased hydrophobicity induced by the formation of acyl groups during MD treatment, uniform lignin nanospheres were successfully recovered from the DES. It exhibited low dispersibility (PDI = 2.23), small molecular weight (1889 g/mol), and excellent oxidation resistance (RSI = 5.94), demonstrating promising applications in functional materials. The mechanism of lignin depolymerization was comprehensively elucidated via FTIR, 2D-HSQC NMR, and GPC analyses. Overall, this study provides a novel and environmentally friendly strategy for lignocellulose biorefinery and lignin valorization.

Integrated acetic acid and deep eutectic solvent pretreatment on poplar for co-production of xylo-oligosaccharides, fermentable sugars and lignin antioxidants/adsorbents

Efficient fractionation of lignocellulosic biomass in usable forms of hemicellulose, cellulose and lignin is very important for the sustainable lignocellulosic biorefinery. Herein, poplar sawdust was pretreated with an integrated process composed of acetic acid pre-hydrolysis (170 °C, 60 min) for xylo-oligosaccharides (XOS) production and mild deep eutectic solvent (90-130 °C, 60 min) post-delignification for recovering lignin fractions, resulting in easily hydrolyzed cellulose fraction. Results showed that, after integrated pretreatment and enzymatic hydrolysis, 51 % of xylan and 92 % of glucan in raw biomass could be converted to XOS (DP 2-6) and glucose, respectively, while 71 % of the original lignin could be recovered in DES solvent. The resulting XOS were proven to ensure the growth of probiotics, Bifidobacterium adolescentis. Besides, the lignin macromolecules recovered from DES solvent showed high-purity (around 95 %), low-molecular weight (Mw around 2000), small particle size (270-170 nm) and high-PhOH (3.08 mmol/g) content, which were likely relevant to the excellent antioxidant activity (RSI = 15.16) and adsorbent activity (Pb(II) 461.89 mg/g lignin). Finally, mass balance and energy analysis revealed that the integrated pretreatment could be used as a promising approach for the production of bio-based chemicals and materials from woody biomass.

Lignin beyond the status quo: recent and emerging composite applications

The demand for biodegradable materials across various industries has recently surged due to environmental concerns and the need for the adoption of renewable materials. In this context, lignin has emerged as a promising alternative, garnering significant attention as a biogenic resource that endows functional properties. This is primarily ascribed to its remarkable origin and structure that explains lignin's capacity to bind other molecules, reinforce composites, act as an antioxidant, and endow antimicrobial effects. This review summarizes recent advances in lignin-based composites, with particular emphasis on innovative methods for modifying lignin into micro and nanostructures and evaluating their functional contribution. Indeed, lignin-based composites can be tailored to have superior physicomechanical characteristics, biodegradability, and surface properties, thereby making them suitable for applications beyond the typical, for instance, in ecofriendly adhesives and advanced barrier technologies. Herein, we provide a comprehensive overview of the latest progress in the field of lignin utilization in emerging composite materials.

Experimental investigations on PVA/chitosan and PVA/chitin films for active food packaging using Oxytenanthera abyssinica lignin nanoparticles and its UV-shielding, antimicrobial, and antiradical effects

This study investigated the effect of adding lignin nanoparticles (LNPs) derived from Oxytenanthera abyssinica via alkali-acid nanoprecipitation method to polyvinyl alcohol/chitosan (PVA/CI) and polyvinyl alcohol/chitin (PVA/CH) films for the active food packaging applications. Adding LNPs at concentrations of 1 % and 3 % improved the films' thermal stability and mechanical properties. The lowest water solubility and moisture content were observed in PVA/CI/LNPs films. LNPs exhibited effective 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities, with the highest values observed in PVA/CH/LNPS and PVA/CI/LNPS films with values of 87.47 and 88.74 % respectively. The addition of LNPs also improved the UV-blocking abilities of the films. PVA/CH/LNP3 and PVA/CI/LNP3 have the smallest percentage transmission values of 3.34 % and 0.86 % in the UV range. The overall migration of dietary stimulants was lower in PVA/CI/LNPS and PVA/CH/LNPS films compared to PVA film. Antibacterial tests demonstrated the inhibitory capacity of the synthesized biofilms against both gram-positive and negative bacterial species, with the highest inhibitory value of 26 mm. The study suggests that PVA/CH/LNPS and PVA/CI/LNPS films have potential applications as active food packaging materials and can be explored in other potential applications such as drug delivery, tissue engineering, wound healing, and slow-release urea fertilizer development.

Sustainable Starch/Lignin Nanoparticle Composites Biofilms for Food Packaging Applications

Construction of sustainable composite biofilms from natural biopolymers are greatly promising for advanced packaging applications due to their biodegradable, biocompatible, and renewable properties. In this work, sustainable advanced food packaging films are developed by incorporating lignin nanoparticles (LNPs) as green nanofillers to starch films. This seamless combination of bio-nanofiller with biopolymer matrix is enabled by the uniform size of nanofillers and the strong interfacial hydrogen bonding. As a result, the as-prepared biocomposites exhibit enhanced mechanical properties, thermal stability, and antioxidant activity. Moreover, they also present outstanding ultraviolet (UV) irradiation shielding performance. As a proof of concept in the application of food packaging, we evaluate the effect of composite films on delaying oxidative deterioration of soybean oil. The results indicate our composite film could significantly decrease peroxide value (POV), saponification value (SV), and acid value (AV) to delay oxidation of soybean oil during storage. Overall, this work provides a simple and effective method for the preparation of starch-based films with enhanced antioxidant and barrier properties for advanced food packaging applications.

Design Strategy and Application of Deep Eutectic Solvents for Green Synthesis of Nanomaterials

The first report of deep eutectic solvents (DESs) was released in 2003 and was identified as a new member of ionic liquid (IL), involving innovative chemical and physical characteristics. Using green solvent technology concerning economical, practical, and environmental aspects, DESs open the window for sustainable development of nanomaterial fabrication. The DESs assist in different fabrication processes and design nanostructures with specific morphology and properties by tunable reaction conditions. Using DESs in synthesis reactions can reduce the required high temperature and pressure conditions for decreasing energy consumption and the risk of environmental contamination. This review paper provides the recent applications and advances in the design strategy of DESs for the green synthesis of nanomaterials. The strategy and application of DESs in wet-chemical processes, nanosize reticular material fabrication, electrodeposition/electrochemical synthesis of nanostructures, electroless deposition, DESs based nano-catalytic and nanofluidic systems are discussed and highlighted in this review.

Nanogrinding/ethanol activation facilitating lignin fractionation for preparation of monodispersed lignin nanoparticles

Lignin nanoparticles (LNPs), as one of green and sustainable biological macromolecules, have attracted great attention owing to their promising potentials in many valorized fields. However, the lignin heterogeneity seriously restricts the controllable preparation of LNPs. Herein, a facile nanogrinding activation combining anhydrous ethanol dissolution process was developed to efficiently homogenize lignin prior to gradient ethanol fractionation. Two lignin fractions were obtained from nanogrinding activation/ethanol dissolution followed by gradient ethanol fractionation: L-fractions and S-fractions. Therefore, monodispersed LNPs with unique concave hollow nanostructure and large particle size, and monodispersed LNPs with solid core nanostructure and small particle size were successfully prepared from L-fractions and S-fractions, respectively, via a GVL/water anti-solvent method. The proposed LNPs formation mechanisms facilitated by nanogrinding activation/ethanol dissolution treatment were demonstrated. This study put forwards a facile and green integrated approach for monodispersed LNPs preparation with controllable morphology and particle size.

Structure and properties of nanoparticles: DES-lignin-g-PNVCL coated aspirin by self-assembly

This work was carried out in order to broaden the application field of lignin and improve its additional value. The degraded deep eutectic solvent lignin-grafted poly(N-vinyl caprolactam) (DES-lignin-g-PNVCL) was synthesized by using modified DES-lignin and NVCL via activators regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP). Aspirin was coated with DES-lignin-g-PNVCL through self-assembly by an ethanol/water anti-solvent method to obtain lignin thermosensitive polymer nanoparticle coated aspirin (aspirin@LTNP). X-ray electron spectroscopy (XPS), elemental analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), and ultraviolet visible spectroscopy (UV) were used to characterize the composition, structure and morphology of DES-lignin-g-PNVCL and aspirin@LTNP. The releasing behavior of aspirin@LTNP at different temperatures and pH values was investigated. The safety was evaluated by cytotoxicity tests. The results indicated that aspirin@LTNP was mainly accumulated by the hydrophobic effect and π-π interaction in the process of self-assembly, and its morphology was an ellipsoid stacked layer by layer. The aspirin@LTNP hydrophilic chains were increased and had externally hydrophilic and internally hydrophobic structures. The particle size decreased slightly during the self-assembly process. The red-shift occurred at the π-π interaction wavelength of the lignin aromatic ring, which indicated a physical coating process. The coating rate of aspirin@LTNP was 88.87%. Aspirin@LTNP showed an obvious temperature response; the 96 h cumulative release rate at the LCST was 73.75 ± 1.16%, while the 96 h cumulative release rate above the LCST was 28.10 ± 0.92%. The 96 h cumulative release rate was 63.21 ± 0.57% at pH = 1.5 and 49.56 ± 0.48% at pH = 7.4. The dosage of aspirin@LTNP used in the experiment was safe. This study provided a strategy for drug coating and controlled release.

Green and Efficient Preparation of Tailed Lignin Nanoparticles and UV Shielding Composite Films

Lignin nanoparticles (LNP) with various morphologies could be prepared with solvent-antisolvent methods. However, the employed toxic chemicals limited its large-scale application. In this study, an extremely green method using only ethanol and water as solvent and antisolvent was reported. Besides, with the syringaldehyde (SA) addition and its anchoring action on the lignin particles, a forming process of the tailed structure was observed and resulted. Moreover, the improved electronegativity originating from the phenolic hydroxyl groups enhanced the size distribution uniformity, and the new absorption peaks at 1190 cm-1 demonstrated the involvement of SA in the LNP formation. Lastly, the tailed lignin nanoparticles (T-LNP) composited with, respectively, polyvinyl alcohol, chitosan, cellulose nanofibers, cationic etherified starch, and sodium alginate were successfully prepared. The outstanding UV-shielding and free radical scavenging properties in the above composites showed their great potential in wide applications in packaging materials.

Unveiling the Biocompatible Properties of Date Palm Tree (Phoenix dactylifera L.) Biomass-Derived Lignin Nanoparticles

Searching for sustainable, ecofriendly, and renewable precursors for nanostructured material synthesis is a fascinating area pertaining to feasibility in various applications. Especially, lignin-based material preparation is essential for unraveling the usage of lignin by valorization. Hence, we have synthesized lignin nanoparticles (LNPs) using date palm tree (Phoenix dactylifera L.) biomass as a precursor in this investigation. The LNP's morphological and thermal features were assessed. Moreover, we have evaluated the LNP's cytocompatibility properties by adopting in vitro approach. The P. dactylifera L. (PD) biomass-derived LNP's morphological features show a spherical shape with a 10-100 nm diameter. The LNPs have a decreased cell viability of ∼8% at a high concentration exposure to human mesenchymal stem cells (hMSCs) for 48 h. However, the LNPs do not cause any cellular and nuclear morphology changes in hMSCs. The mitochondrial membrane potential assessment results confirm healthy mitochondria with high mitochondrial membrane potential in LNP-treated cells. The intracellular reactive oxygen species (ROS) generation assay results revealed that LNPs do not trigger ROS generation in hMSCs. We examined the upregulation of GSTM3 and GSR genes and the downregulation of SOD1 genes in LNP-treated hMSCs, but no significant changes were observed. Our study concluded that PD biomass-derived LNPs have a good cytocompatibility and an antioxidant property. Thus, they can be applicable for various biological, cosmetic, and environmental applications.

Lignin as a Natural Carrier for the Efficient Delivery of Bioactive Compounds: From Waste to Health

Lignin is a fascinating aromatic biopolymer with high valorization potentiality. Besides its extensive value in the biorefinery context, as a renewable source of aromatics lignin is currently under evaluation for its huge potential in biomedical applications. Besides the specific antioxidant and antimicrobial activities of lignin, that depend on its source and isolation procedure, remarkable progress has been made, over the last five years, in the isolation, functionalization and modification of lignin and lignin-derived compounds to use as carriers for biologically active substances. The aim of this review is to summarize the current state of the art in the field of lignin-based carrier systems, highlighting the most important results. Furthermore, the possibilities and constraints related to the physico–chemical properties of the lignin source will be reviewed herein as well as the modifications and processing required to make lignin suitable for the loading and release of active compounds.

Ultrafast alkaline deep eutectic solvent pretreatment for enhancing enzymatic saccharification and lignin fractionation from industrial xylose residue

An aspirational pretreatment method for efficient fractionation and tailored valorization of large industrial biomass can ensure the realizability of sustainable biorefinery strategies. In this study, an ultrafast alkaline deep eutectic solvents (DES) pretreatment strategy was developed to efficiently extract the lignin nanoparticles and retain cellulose residues that could be readily enzymatic saccharified to obtain fermentative glucose for the bioenergy production from industrial xylose residue. Results showed that the DES pretreatment had excellent delignification performance and the regenerated DES lignin nanoparticles exhibited well-preserved structures and excellent antioxidant activity, as well as low molecular weights and relatively uniform size distribution, which could facilitate downstream catalytic degradation for production of chemicals and preparation of lignin-based materials. Under the optimal condition (DES pretreatment: 80 °C, 10 min; saccharification: 10 FPU/g, 5 wt%, 100 mg/g Tween 80), the glucose yield of 90.12% could be achieved, which was dramatically increased compared to raw materials.

Recent Advances in the Synthesis of Inorganic Materials Using Environmentally Friendly Media

Deep Eutectic Solvents have gained a lot of attention in the last few years because of their vast applicability in a large number of technological processes, the simplicity of their preparation and their high biocompatibility and harmlessness. One of the fields where DES prove to be particularly valuable is the synthesis and modification of inorganic materials-in particular, nanoparticles. In this field, the inherent structural inhomogeneity of DES results in a marked templating effect, which has led to an increasing number of studies focusing on exploiting these new reaction media to prepare nanomaterials. This review aims to provide a summary of the numerous and most recent achievements made in this area, reporting several examples of the newest mixtures obtained by mixing molecules originating from natural feedstocks, as well as linking them to the more consolidated methods that use "classical" DES, such as reline.

Solid acid facilitated deep eutectic solvents extraction of high-purity and antioxidative lignin production from poplar wood

Pure deep eutectic solvents (DESs) system of choline chloride (ChCl)/Lactic acid (Lac) were demonstrated to be an effective strategy for extraction of lignin. In this study, two kinds of different promising solid acid (SA) with DESs were designed to promote the pretreatment of lignocellulose. The SA of phosphotungstic acid (H₃O₄₀PW₁₂) and iron bromide (FeBr₃) were introduced into DESs to extract poplar wood lignin and evaluate the antioxidant activity. It was found that 82.2% and 80.9% of lignin were obtained from poplar wood under H₃O₄₀PW₁₂-ChCl/Lac acid and FeBr₃-choline ChCl/Lac system with 4 h and 8 h, respectively. The lignin fractions with a high purity (>89%), low molecular weight (Mw 1800-2000 g/mol). Besides, the antioxidant activities of lignin fractions were better than butyl hydroxyanisole (BHA). Therefore, DES lignin has prominent antioxidant activity and could developed a potential natural cosmetics and food packaging.