Comparative antioxidant and cytotoxic effects of lignins from different sources

Fractionation, characterization, and economic evaluation of alkali lignin from saw industry waste

The present work was focused on the investigation of lignin isolation from saw industry biomass (sawdust (SD)) using alkali solution, and to perform economic analysis for 2000 kg/batch hypothetical plant using techno-economic analysis. The isolated lignin was fractionated using organic solvent to obtain purified lignin. FTIR and ¹H NMR analysis were performed to examine the structural characteristics of lignin. Lignin nanoparticles (LN) showed higher total phenolic content (TPC) (244.1 ± 2 µg of GAE per mg) and antioxidant activity (63.2 ± 1.7%) compared with crude lignin (CL), ethanol fractionated lignin (EL), and acetone fractionated lignin (AL). SuperPro designer was exposed to design and simulated 2000 kg/batch of sawdust fractionation process. The techno-economic analysis estimated that the lignin production cost is about $ 487,000 per year, and the annual revenue could be $ 1,850,000 per year. The techno-economic analysis and sensitivity analysis could be useful for the industrial level sawdust fractionation process.

The role of lignin and lignin-based materials in sustainable construction - A comprehensive review

The construction industry in the 21st century faces numerous global challenges associated with growing concerns for the environment. Therefore, this review focuses on the role of lignin and its derivatives in sustainable construction. Lignin's properties are defined in terms of their structure/property relationships and how structural differences arising from lignin extraction methods influence its application within the construction sector. Lignin and lignin composites allow the partial replacement of petroleum products, making the final materials and the entire construction sector more sustainable. The latest technological developments associated with cement composites, rigid polyurethane foams, paints and coatings, phenolic or epoxy resins, and bitumen replacements are discussed in terms of key engineering parameters. The application of life cycle assessment in construction, which is important from the point of view of estimating the environmental impact of various solutions and materials, is also discussed.

Microfluidic Synthesis of Lignin/Chitosan Nanoparticles for the pH-Responsive Delivery of Anticancer Drugs

In this work, lignin/chitosan nanoparticles (Lig/Chi NPs) with controlled structures were synthesized in a simple and scalable microfluidic system. When the positively charged chitosan and the negatively charged lignin solution were blended in a microreactor, Lig/Chi NPs were rapidly formed via the electrostatic coassembly between the amino groups of chitosan and the carboxyl groups of lignin. The ζ potential changes from negative (-13 mV) to positive (+54.5 mV) for Lig NPs and Lig/Chi NPs, respectively. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results demonstrated that Lig/Chi NPs have an average particle size of about 180 nm, which can be used as nanocarriers for drug delivery. The anticancer drug nanoparticles with docetaxel (DTX) and curcumin (CCM) were prepared by coassembly with Lig/Chi NPs in a microreactor, which had good drug loading efficiency, biocompatibility, and can release drugs in response to pH in the weakly acidic environment of the tumor. The drug release amounts in acidic solutions that simulated the tumor microenvironment were 51% (DTX@Lig/Chi NPs) and 50% (CCM@Lig/Chi NPs), respectively, which were better than the release amounts at pH 7.4, and have an obvious killing effect on HeLa cells.

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

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

Fungal melanin as a biocompatible broad-spectrum sunscreen with high antioxidant activity

Melanin is considered a bio-inspired dermo-cosmetic component due to its high UV absorption and antioxidant activity. Among various melanin sources, fungal melanin is a promising candidate for sunscreen because of its sustainability and scalability; however, quantitative assessment of its function has not yet been sufficiently explored. In this study, melanin samples derived from Amorphotheca resinae were prepared, followed by the evaluation of their sunscreen performance, antioxidant activity, and cytotoxicity. Melanin-blended cream was prepared by blending a melanin suspension and a pure cream. The cream showed an in vitro sun protection factor value of 2.5 when the pigment content was 5%. The cream showed a critical wavelength of approximately 388 nm and a UVA/UVB ratio of more than 0.81, satisfying the broad-spectrum sunscreen requirement. Oxygen radical absorbance capacity assays indicated that fungal melanin had antioxidant activity similar to ascorbic acid but higher than reduced glutathione. Fungal melanin had no statistically significant cytotoxicity to human keratinocyte cell lines until 72 h of exposure, even at a concentration of 4 mg mL-1. Consequently, melanin pigment can be used as a biocompatible broad-spectrum sunscreen with high antioxidant activity and as a practical alternative in dermo-cosmetic formulations.

Self-Assembly Preparation of Nano-Lignin/Cationic Polyacrylamide Complexes

The present work describes the preparation of nano-lignin particles from calcium lignosulfonate (CL). The nano-lignin was fabricated from colloidal lignin-polyacrylamide complexes via self-assembly. The sizes of the nano-lignin particles were examined by dynamic light scattering (DLS) and scanning electron microscopy (SEM). The results indicated that the average particle size of the prepared nano-lignin was approximately 100 nm. In addition, the obtained nano-lignin exhibited enhanced fluorescence intensity when compared with the original lignin, which might represent a potential application of this nano-particle product.

Hydrogel from all in all lignocellulosic sisal fibers macromolecular components

The heterogeneous structure of lignocellulosic biomass makes it difficult to dissolve its main components (cellulose, hemicelluloses, and lignin) by solvent action with the aim of further applying the mixture of the biological macromolecules generated in the solvent medium. In the present study, the dissolution efficiency (DE) of lignocellulosic sisal fibers in the lithium chloride/dimethylacetamide solvent system (LiCl/DMAc) was evaluated for further application in the formation of hydrogels. Catalytic amounts of trifluoroacetic acid (TFA) were used in some experiments, which increased the DE from 40% to 90%. The regeneration of the solutions, either previously filtered or not, led to hydrogels based on sisal lignocellulosic biomass. In brief, the properties of the hydrogels were influenced by the content of the lignocellulosic components in the hydrogels, present both in the dissolved fraction and in the incorporated undissolved fraction (when nonfiltered solutions were used). Hydrogels presented water absorption up to 7479% and resorption content in the lyophilized hydrogel up to 2133%. Extracts obtained from preselected hydrogels exhibited cell viability up to 127% compared to the control group when in contact with fibroblast cultures, exhibiting their noncytotoxic properties. This attribute increased the range of possible applications of these hydrogels, ranging from agriculture to biocompatible materials.

Safety aspects of kraft lignin fractions: Discussions on the in chemico antioxidant activity and the induction of oxidative stress on a cell-based in vitro model

Lignin is a complex phenolic biopolymer present in plant cell walls and a by-product of the cellulose pulping industry. Lignin has functional properties, such as antioxidant activity, that make it a potential natural active ingredient for health-care products. However, not all safety aspects of lignin fractions have been adequately investigated. Herein, we evaluated the antioxidant and genotoxic potential of two hardwood kraft lignins (F3 and F5). The chemical characterization of F3 and F5 demonstrated their thermal stability and the presence of different phenolic units, while the DPPH assay confirmed the antioxidant activity of these lignin fractions. Despite being antioxidants in the DPPH assay, F3 and F5 were capable of generating intracellular reactive oxygen species (ROS) and subsequently causing oxidative DNA damage (Comet assay) in HepG2 cells. The biological relevance of the DPPH assay might be uncertain in some cases; therefore, we suggest combining in chemico tests with biological system-based tests to determine efficacy and safety levels of lignins and define appropriate applications of lignins for consumer products. Moreover, kraft lignins obtained by acid precipitation may pose risks to human health; however, as genotoxicity is not the sole endpoint of toxicity required in hazard assessments, additional toxicological evaluations are needed.

Antioxidant and UV-Blocking Properties of a Carboxymethyl Cellulose-Lignin Composite Film Produced from Oil Palm Empty Fruit Bunch

Oil palm empty fruit bunch (EFB) pulp with the highest cellulose content of 83.42% was obtained from an optimized process of acid pretreatment (0.5% v/v H2SO4), alkaline extraction (15% w/w NaOH), and hydrogen peroxide bleaching (10% w/v H2O2), respectively. The EFB cellulose was carboxymethylated, and the obtained carboxymethyl cellulose (CMC) was readily water-soluble (81.32%). The EFB CMC was blended with glycerol and cast into a composite film. Lignin that precipitated from the EFB black liquor was also incorporated into the film at different concentrations, and its effect on the UV-blocking properties of the film was determined. Interestingly, the EFB CMC film without lignin addition completely blocked UV-B transmittance. The incorporation of lignin at all concentrations significantly enhanced the UV-A blocking and other physical properties of the film, including the surface roughness, thickness, and thermal stability, although the tensile strength and water vapor permeability were not significantly affected. Complete UV-A and UV-B blocking were observed when lignin was added at 0.2% (w/v), and the film also exhibited the highest antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals with an half-maximal inhibitory concentration (IC50) value of 3.87 mg mL-1.

Lignin: Drug/Gene Delivery and Tissue Engineering Applications

Lignin is an abundant renewable natural biopolymer. Moreover, a significant development in lignin pretreatment and processing technologies has opened a new window to explore lignin and lignin-based bionanomaterials. In the last decade, lignin has been widely explored in different applications such as drug and gene delivery, tissue engineering, food science, water purification, biofuels, environmental, pharmaceuticals, nutraceutical, catalysis, and other interesting low-value-added energy applications. The complex nature and antioxidant, antimicrobial, and biocompatibility of lignin attracted its use in various biomedical applications because of ease of functionalization, availability of diverse functional sites, tunable physicochemical and mechanical properties. In addition to it, its diverse properties such as reactivity towards oxygen radical, metal chelation, renewable nature, biodegradability, favorable interaction with cells, nature to mimic the extracellular environment, and ease of nanoparticles preparation make it a very interesting material for biomedical use. Tremendous progress has been made in drug delivery and tissue engineering in recent years. However, still, it remains challenging to identify an ideal and compatible nanomaterial for biomedical applications. In this review, recent progress of lignin towards biomedical applications especially in drug delivery and in tissue engineering along with challenges, future possibilities have been comprehensively reviewed.

Characterization of a lignin from Crataeva tapia leaves and potential applications in medicinal and cosmetic formulations

Lignins are phenolic macromolecules that have several applications. In this work, we examine some biological activities of a lignin-like macromolecule isolated from the Crataeva tapia leaves, not yet studied to evaluate its potential applications in medicinal and cosmetic formulations. Lignin was obtained by alkaline delignification and its physical-chemical characterization was made by means of FT-IR, UV-Vis, NMR spectroscopy, elementary analysis, molecular mass determination and thermal analysis. Lignin is of the GSH type, with levels of hydrogen (5.10%), oxygen (27.18%), carbon (67.60%), nitrogen (0.12%) and phenolic content of 189.6 ± 9.6 mg GAE/g. In addition, it is a thermally stable macromolecule with low antioxidant activity. Cytotoxicity and cytokine production were assessed by flow cytometry. The photoprotective activity was evaluated by adding different concentrations of lignin to a commercial cream. Lignin was not cytotoxic, it stimulated the production of TNF-α, IL-6 and IL-10 and did not promote a significant change in nitric oxide levels. In addition, this macromolecule was able to promote increased absorption of ultraviolet light from a commercial cream. These results reinforce the ethnopharmacological use of C. tapia leaves and suggest the need for further studies to determine the potential medicinal and cosmetic applications (sunscreen) of lignin from C. tapia leaves.

Fabricating Antibacterial and Antioxidant Electrospun Hydrophilic Polyacrylonitrile Nanofibers Loaded with AgNPs by Lignin-Induced In-Situ Method

Concerning the environmental hazards owing to the chemical-based synthesis of silver nanoparticles (AgNPs), this study aimed to investigate the possibility of synthesizing AgNPs on the surface of polyacrylonitrile (PAN) nanofibers utilizing biomacromolecule lignin. SEM observations revealed that the average diameters of the produced nanofibers were slightly increased from ~512 nm to ~673 nm due to several factors like-swellings that happened during the salt treatment process, surface-bound lignin, and the presence of AgNPs. The presence of AgNPs was validated by transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) analysis. The amount of synthesized AgNPs on PAN nanofibers was found to be dependent on both precursor silver salt and reductant lignin concentration. Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectra confirm the presence of lignin on PAN nanofibers. Although the X-ray diffraction pattern did not show any AgNPs band, the reduced intensity of the stabilized PAN characteristics bands at 2θ = 17.28° and 29.38° demonstrated some misalignment of PAN polymeric chains. The water contact angle (WCA) of hydrophobic PAN nanofibers was reduced from 112.6 ± 4.16° to 21.4 ± 5.03° for the maximum AgNPs coated specimen. The prepared membranes exhibited low thermal stability and good swelling capacity up to 20.1 ± 0.92 g/g and 18.05 ± 0.68 g/g in distilled water and 0.9 wt% NaCl solution, respectively. Coated lignin imparts antioxidant activity up to 78.37 ± 0.12% at 12 h of incubation. The resultant nanofibrous membranes showed a proportional increase in antibacterial efficacy with the rise in AgNPs loading against both Gram-positive S. aureus and Gram-negative E. coli bacterial strains by disc diffusion test (AATCC 147-1998). Halos for maximum AgNPs loading was calculated to 18.89 ± 0.15 mm for S. aureus and 21.38 ± 0.17 mm for E. coli. An initial burst release of silver elements within 24 h was observed in the inductively coupled plasma-atomic emission spectrometry (ICP-AES) test, and the release amounts were proportionally expansive with the increase in Ag contents. Our results demonstrated that such types of composite nanofibers have a strong potential to be used in biomedicine.

Delignification of Cistus ladanifer Biomass by Organosolv and Alkali Processes

Residues of Cistus ladanifer obtained after commercial steam distillation for essential oil production were evaluated to produce cellulose enriched solids and added-value lignin-derived compounds. The delignification of extracted (CLRext) and extracted and hydrothermally pretreated biomass (CLRtreat) was studied using two organosolv processes, ethanol/water mixtures (EO), and alkali-catalyzed glycerol (AGO), and by an alkali (sodium hydroxide) process (ASP) under different reaction conditions. The phenolic composition of soluble lignin was determined by capillary zone electrophoresis and by Py-GC/MS, which was also used to establish the monomeric composition of both the delignified solids and isolated lignin. The enzymatic saccharification of the delignified solids was also evaluated. The ASP (4% NaOH, 2 h) lead to both the highest delignification and enzymatic saccharification (87% and 79%, respectively). A delignification of 76% and enzymatic hydrolysis yields of 72% were obtained for AGO (4% NaOH) while EO processes led to lower delignification (maximum lignin removal 29%). The residual lignin in the delignified solids were enriched in G- and H-units, with S-units being preferentially removed. The main phenolics present in the ASP and AGO liquors were vanillic acid and epicatechin, while gallic acid was the main phenolic in the EO liquors. The results showed that C. ladanifer residues can be a biomass source for the production of lignin-derivatives and glucan-rich solids to be further used in bioconversion processes.

Sustainable production of lignin micro-/nano-particles (LMNPs) from biomass: Influence of the type of biomass on their self-assembly capability and physicochemical properties

The production of lignin micro-/nano-particles (LMNPs) has gained growing interest due to their eco-friendly feature and biological compatibility with negligible hazardous impacts. Herein, this work carefully addresses the preparation of LMNPs from different types of biomass, including pine wood, birch wood, pubescens, vinasse, corncob and corncob residue. Firstly, ligno-oligomers were produced from each biomass through a H₂O-THF co-solvent system. Then, LMNPs were generated from these effluents. Uniform and spherical LMNPs, consisting of benzene ring-stacked cores and hydrophilic shells, were obtained only from the liquids yielded by the treatment of the corncob residue and pine wood. The characterization of the ligno-oligomers and the LMNPs revealed that the molecular weights of the ligno-oligomers did not exert a significant effect on their self-assembly capability. The presence of guaiacyl units connected by β-O-4 and β-β linkages was beneficial for the π-π stacking of the benzene rings into compact cores, while the existence of β-5 linkages and C_α-oxidized side-chains exerted a negative effect. Stable and spherical LMNPs with an appropriate negative zeta potential and a relatively high thermal stability were obtained from the corncob residue and pine wood, which can serve as functional materials in various application areas.

Fabrication and Characterization of Lignin/Dendrimer Electrospun Blended Fiber Mats

Blending lignin as the second most abundant polymer in Nature with nanostructured compounds such as dendritic polymers can not only add value to lignin, but also increase its application in various fields. In this study, softwood Kraft lignin/polyamidoamine dendritic polymer (PAMAM) blends were fabricated by the solution electrospinning to produce bead-free nanofiber mats for the first time. The mats were characterized through scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, zeta potential, and thermogravimetry analyses. The chemical intermolecular interactions between the lignin functional groups and abundant amino groups in the PAMAM were verified by FTIR and viscosity measurements. These interactions proved to enhance the mechanical and thermal characteristics of the lignin/PAMAM mats, suggesting their potential applications e.g. in membranes, filtration, controlled release drug delivery, among others.

Evaluating the bio-application of biomacromolecule of lignin-carbohydrate complexes (LCC) from wheat straw in bone metabolism via ROS scavenging

Lignin-carbohydrate complexes (LCC) arebiomacromolecules that can be obtained from different biomass. Even some works have shown the LCC can efficiently scavenge the intracellular and endogenous reactive oxygen species (ROS), while little work has been carried out to investigate the potential application of LCC for ROS-related treatment in biological filed, especially for the treatment of periprosthetic osteolysis in vivo. In this work, Lignin-rich (LCC-A) and carbohydrate-rich (LCC-B) fractions in wheat straw are isolated and used as the ROS scavenger to promote osteoblast differentiation and inhibit osteoclast differentiation. The chemical composition and structures are characterized by high performance anion exchange chromatography (HPAEC) and nuclear magnetic resonance (NMR) technologies (quantitative ¹³C NMR and 2D-HSQC NMR), respectively. The results showed LCC-A possesses higher in vitro ROS-scavenging ability than LCC-B (89.8% vs 57.8%) and to inhibit osteoclast differentiation, whereas LCC-B more significantly activates cellular antioxidant activities via the KEAP1-NRF2-ARE pathway (218.5% vs 438.0% in the level of HO-1), thus promoting osteoblast differentiation in an inflammatory environment. Moreover, the therapeutic administration of LCC-A and LCC-B for Ti-particle-induced osteolytic murine calvariae showed both of them positively regulate and restore the bone metabolism, while preventing calvaria impairment. Hence, LCC from wheat straw exhibits efficient bone protective effects, suggesting it may be used as the promising ROS scavenger for clinical treatment of periprosthetic osteolysis.

The Study of Antibacterial Properties of Anbarnasara Smoke on Multi-Drug Resistant Bacteria Isolated From Urinary Infection in Pregnant Women

Background: Using smoke from burning donkey dung has been popular in the treatment of many diseases in Iran. Objective: This study aimed to investigating the antimicrobial properties of donkey dung smoke on multi-drug resistant (MDR) bacteria isolated from urinary infection. Materials and Methods: First, 300 and 200 urine samples were collected from pregnant and non-pregnant women in Isfahan, Iran. Then in each group, 100 bacterial isolates including Escherichia coli, Klebsiella pneumonia, Proteus vulgaris, Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, and Staphylococcus saprophyticus were isolated. Antibiotic resistant protocol was determined by antibiogram test. Donkey dung was sterilized, disintegrated, and heated. The smokes were concentrated in n-hexane solvent (65%) and were collected after evaporation of the solvent. Finally, the antibacterial activities of the concentrations of 0.25, 0.5 and 1 mg/mL of the smokes were detected using disk diffusion and macrodilution methods. Results: The most abundant MDR isolates causing urinary infections in pregnant and non-pregnant women was Escherichia coli. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of donkey dung smoke on MDR isolates from pregnant women were 0.25 mg/mL and 0.5 mg/mL, respectively. In the case of MDR isolates in non-pregnant women, the MIC of the smoke on Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus was 0.25 mg/mL, and the MBC on these isolates was 0.5 mg/mL. Conclusion: The smokes from donkey dung investigated in the present study have suitable potentials for controlling the infections after In vivo analysis.

Acetylated lignin nanoparticles as a possible vehicle for photosensitizing molecules

Lignins are underused and abundant bio-sourced polymers with various potential applications. An attractive one is the development of nanoparticles for bioactive compound delivery. Here, we optimized the synthesis of hydrodispersible nanoparticles of acetylated lignin by comparing different lignin sources, degrees of acetylation and preparation methods. The formation of acetylated lignin nanoparticles in various solvents was probed by both experiments and, for the first time, a molecular dynamics simulation. We showed that dialysis is more suitable to obtain these nanoparticles than anti-solvent addition. The encapsulation of hydrophobic photosensitizing porphyrin in these nanoparticles was also demonstrated and rationalized at the molecular level, together with experiments, docking and molecular dynamics simulations. As acetylated lignin has been demonstrated to exhibit photosensitizing activity, the encapsulation of bioactive compounds in lignin nanoparticles opens the doors to a broad range of potential applications.

Lignin-based fluorescence hollow nanoparticles: Their preparation, characterization, and encapsulation properties for doxorubicin

Lignin shows strong adsorption, biodegradability and non-toxicity, and has opened a research hotspot in the design and manufacture of controllable nanomaterials for drug delivery. However, lignin-based materials, with both diagnostic and therapeutic functions, have yet to be developed. In this work, enzymatically hydrolysable lignin (EHL) was used to prepare blue fluorescent lignin copolymer by grafting 1-Pyrenebutyric acid onto lignin via amidation reaction and then formed self-assembled nanoparticles. The results show that such lignin-based hollow nanoparticles exhibit characteristics of fluorescent functions, size controlled and stable structure within 15 days. For anticancer drug Doxorubicin, the encapsulation efficiency and drug loading reached, respectively, 50% and 10%. This encapsulation had no cytotoxicity, and sustained-release effect on the drug. The aim of this study was to develop the multifunctional bio-nanomaterials for medical applications, through simple, environmentally friendly, low-cost methods.

Role of different lignin systems in polymers: mechanical properties and thermal stability

Lignin was used to study the mechanical properties and thermal stability of polymers. The lignin was blended with three kinds of polymers, and the addition of lignin was 0.5 wt%. Under the condition of thermal oxidation, the thermal stability of lignin/polymer samples varies with the structure of lignin. The effects of lignin on the mechanical properties and thermal stability of the polymers were investigated by oxidation induction time (OIT), rheological properties, mechanical properties and differential scanning calorimetry (DSC). The results show that the effect of lignin on the thermal properties of polymer samples is 2~3°C. It can be inferred that lignin can effectively improve the interaction between polymer molecular chain segments, and improve the crystallization rate and rigidity to a certain extent, so it can be seen that lignin has good compatibility and thermal stability.

Lignin-Based Sunscreens—State-of-the-Art, Prospects and Challenges

This review covers the latest developments and challenges in the field of broad-spectrum sunscreens and how sunscreens based on lignin address their requirements in terms of sunlight protection, antioxidants, and preservatives.

Isolation and Identification of a Novel Anti-protein Aggregation Activity of Lignin-Carbohydrate Complex From Chionanthus retusus Leaves

Lignin-carbohydrate complex (LCC) is the biological macromolecule that has been demonstrated to exert multiple biological functions, including antioxidant, anti-inflammation and anti-tumorigenesis, which support its broad application in the bioengineering field. However, it remains elusive the involvements of LCC in human neurological disorders, especially those with the overproduction of reactive oxygen species (ROS), such as spinocerebellar ataxias (SCAs). In this study, we found a previously undetermined anti-protein aggregation activity of LCC. Initially, two individual LCC preparations and carbohydrate-free lignin were isolated from the water-extracted waste residues of Chionanthus retusus (C. retusus) tender leaves. The chemical compositional analysis revealed that lignin (61.5%) is the predominant constituent in the lignin-rich LCC (LCC-L-CR), whereas the carbohydrate-rich LCC (LCC-C-CR) is mainly composed of carbohydrate (60.9%) with the xylan as the major constituent (42.1%). The NMR structural characterization showed that LCC-L-CR preparation is enriched in benzyl ether linkage, while phenyl glycoside is the predominant type of linkage in LCC-C-CR. Both LCC and lignin preparations showed antioxidant activities as exemplified by their abilities to scavenge free radicals in cultured mammalian cells and ROS in zebrafish. We further demonstrated a pronounced capability of LCC-L-CR in inhibiting the aggregation of expanded Ataxin-3, disease protein of SCA type 3, in human neuronal cells. Taken together, our study highlights the antioxidant and novel anti-protein aggregation activities of the C. retusus tender leaves-derived LCC.

Structural features and antioxidant activities of Chinese quince (Chaenomeles sinensis) fruits lignin during auto-catalyzed ethanol organosolv pretreatment

Chinese quince fruits (Chaenomeles sinensis) have an abundance of lignins with antioxidant activities. To facilitate the utilization of Chinese quince fruits, lignin was isolated from it by auto-catalyzed ethanol organosolv pretreatment. The effects of three processing conditions (temperature, time, and ethanol concentration) on yield, structural features and antioxidant activities of the auto-catalyzed ethanol organosolv lignin samples were assessed individually. Results showed the pretreatment temperature was the most significant factor; it affected the molecular weight, S/G ratio, number of β-O-4' linkages, thermal stability, and antioxidant activities of lignin samples. According to the GPC analyses, the molecular weight of lignin samples had a negative correlation with pretreatment temperature. 2D-HSQC NMR and Py-GC/MS results revealed that the S/G ratios of lignin samples increased with temperature, while total phenolic hydroxyl content of lignin samples decreased. The structural characterization clearly indicated that the various pretreatment conditions affected the structures of organosolv lignin, which further resulted in differences in the antioxidant activities of the lignin samples. These results can be helpful for controlling and optimizing delignification during auto-catalyzed ethanol organosolv pretreatment, and they provide theoretical support for the potential applications of Chinese quince fruits lignin as a natural antioxidant in the food industry.

Lignin-Based Micro- and Nanomaterials and their Composites in Biomedical Applications

Lignin, as the most abundant aromatic renewable biopolymer in nature, has long been regarded as waste and simply discarded from the pulp and paper industry. In recent years, with many breakthroughs in lignin chemistry, pretreatment, and processing techniques, a lot of the inherent bioactivities of lignin, including antioxidant activities, antimicrobial activities, biocompatibilities, optical properties, and metal-ion chelating and redox activities, have been discovered and this has opened a new field not only for lignin-based materials but also for biomaterials. In this Review, the biological activities of lignin and drug/gene delivery and bioimaging applications of various types of lignin-based material are summarized. In addition, the challenges and limitations of lignin-based materials encountered during the development of biomedical applications are also discussed.

Natural Sunscreens Based on Nanoparticles of Modified Kraft Lignin (CatLignin)

Commercial chemical sunscreens have a high content of synthetic ultraviolet (UV) actives that have caused widespread damage to marine ecosystems and may have adverse health effects in humans. In the present work, safer bio-based sunscreens with lignin UV absorbers were developed to address this issue. Partly demethylated and otherwise altered kraft lignins, the so-called CatLignins with abundant phenolic hydroxyl auxochromes and catechol units, outperformed regular kraft lignins as sunscreen UV absorbers in terms of sun protection factor (UVB-SPF) and UVA-UVB transmittance. Converting lignins to nanoparticles significantly enhanced sunscreen performance. The best lignin sunscreen, containing nanoparticles of hardwood CatLignin, had a UV transmittance of only 0.5-3.8% over the entire UVA-UVB region compared to 2.7-51.1% of a commercial SPF 15 sunscreen. Lignin-based sunscreens are particularly suitable for dark-tinted SPF cosmetics.

Assembly of lignin-based colloidal particles: effects of cationic surfactants, molecular weight, and solvent on morphology

Sodium lignosulfonate (LS) is a lignin derivative, which has abundant resources and is an environmentally friendly raw material. In this study, cetyltrimethylammonium bromide (CTAB) and stearyltrimethylammonium bromide (STAB) were combined with LS at the isoelectric point for hydrophobic self-assembly. Transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and static contact angle data proved that LS/CTAB could form colloidal spheres, while LS/STAB could not form such spheres. The impact of the molecular weight of LS on the self-assembly of LS/CTAB was investigated by using the TEM, FTIR, and static contact angle data. The obtained results showed that LS/CTAB with 10 000–50 000 Da of LS could form colloidal spheres, while LS/CTAB with 3000–5000 Da of LS could not. In addition, the TEM images revealed that the solvent plays an important role in the morphology of LS/CTAB colloidal spheres. Finally, LS/CTAB colloidal spheres were used for the encapsulation of ibuprofen (IBU). The in vitro release behavior of IBU was proven to be pH-sensitive and exhibited controlled release properties. More than 85% IBU could be preserved in simulated gastric fluid, and over 75% could be released in simulated intestinal fluid. This work provides a theoretical basis for the preparation of LS/CTAB colloidal spheres and facilitates the expansion of its applications as a drug carrier.

Effect of cationic surfactants, molecular weight and solvent on the morphology of lignin based particles and in vitro release behavior.

Application of electrospun polycaprolactone fibers embedding lignin nanoparticle for peripheral nerve regeneration: In vitro and in vivo study

Lignin displays attractive properties in peripheral nerve applications. Here, aligned polycaprolactone (PCL) fibers with various percentages of lignin nanoparticles were fabricated using the electrospinning method. The morphologies, contact angles, mechanical properties, in vitro degradation, and water uptake of the PCL/lignin fibers were characterized. Cell viability and adhesion of PC12 and human adipose-derived stem cells (hADSCs) were studied employing MTT assay and SEM, respectively. SEM, immunocytochemistry, and Real-Time PCR were utilized to characterize neural differentiation and neurite length of PC12 and hADSCs. To further study on lignin effect on nerve regeneration, in vivo studies were performed. The results indicated that all nanocomposite fibers were smooth and bead-free. With increasing the lignin content, the water contact angle decreased while in vitro degradation, water uptake, and Young's modulus increased compared to the PCL fibers. Cell viability, and differentiation along with neurite length extension were promoted by increasing lignin content. The neural markers expression for differentiated cells were upregulated by the increase of lignin percent. In vivo investigation also demonstrates that sample groups incorporating 15% lignin nanoparticles showed better regeneration among others. Therefore, PCL with 15% of lignin nanoparticles shows great potential to be applied for nerve regeneration.

Cosmetic potential of lignin extracts from alkaline-treated sugarcane bagasse: Optimization of extraction conditions using response surface methodology

Each year, sugarcane bagasse, a low-priced by-product of the sugar industry, is generated in large quantities. The aim of this study was to optimize the alkaline hydrolysis condition for the extraction of lignin from sugarcane bagasse using response surface methodology combined with Box-Behnken design, and to evaluate functional properties of lignin extracts for cosmetic applications. Three process parameters were varied (NaOH solution concentrations (3-7% w/v), temperatures (115-135 °C), and times (30-60 min)). The second-order polynomial model developed and the subsequent ANOVA test showed that the optimal conditions providing the highest total phenolic content (69.41 ± 0.32 mg gallic acid equivalent/g extract), antioxidant activity (262.30 ± 2.98 mg Trolox equivalent/g extract), and sun protection factor (8.65 ± 0.21) were as follows: NaOH solution concentration of 7% w/v, temperature of 135 °C, and time of 47.92 min. Fourier-transform infrared spectroscopy analysis revealed the functional groups present in the lignin extract that affected its activities. The extract showed both UVA and UVB-absorbing properties and tyrosinase-inhibitory properties. The results suggested that the lignin extract obtained from alkaline hydrolysis of sugarcane bagasse has great potential as a bioactive multi-functional ingredient that can offer anti-ageing, sun-protection, and skin-whitening properties for sun care formulations.

Enhanced permeability, mechanical and antibacterial properties of cellulose acetate ultrafiltration membranes incorporated with lignocellulose nanofibrils

Cellulose acetate (CA) ultrafiltration membranes are attracting more attention in wastewater purification due to its biodegradability and eco-friendly. The application of CA membranes, however, is limited by high susceptibility to bacterial corrosion and lack of mechanical tolerance that results in loss of life. To solve the above problems, we first fabricated the CA-based composite membranes incorporated with bamboo-based lignocellulose nanofibrils (LCNFs) by a strategy of phase inversion. LCNFs was prepared by using a combined method of one-step chemical pretreatment and acid hydrolysis coupled with high-pressure homogenization. The as-prepared CA/LCNFs composite membranes with 4 wt% lignin in the LCNFs exhibited high tensile strength of 7.08 MPa and strain-at-break of 12.21%, and high filtration permeability of 188.23 L·m^-2·h^-1 as ultrafiltration membranes for wastewater treatment, which could obviously inhibit the growth of Escherichia coli.

Neutral fabrication of UV-blocking and antioxidation lignin-stabilized high internal phase emulsion encapsulates for high efficient antibacterium of natural curcumin

By adjusting the polarity and conformation via the sulfomethylation modification, the bio-renewable enzymatic hydrolysis lignin (EHL) combined with alkyl polyglucoside (APG) was used as an emulsifier to stabilize the oil-in-water (O/W) high internal phase emulsions (HIPEs) for the first time under neutral conditions. The structure and sulfonation degree of the sulfomethylated lignin (EHL-XS) were characterized using gel permeation chromatography (GPC), Fourier transform infrared (FT-IR) spectroscopy, dynamic light scattering (DLS) and an automatic potentiometric titrator. The effects of the EHL-XS concentration, sulfonation degree and oil/water ratio on the microstructure and stability of HIPEs were investigated using an optical microscope and a rheometer. The results suggest that commercial lignosulfonates (LS) could not to stabilize HIPEs due to their high hydrophilicity. However, by using EHL-XS with sulfonation degree between 0.89 and 1.05 mmol g-1, up to 2.0 wt% of EHL-XS with the assistance of 3.5 wt% APG could stabilize HIPEs containing 80 vol% of internal oil phase, which were super stable and displayed no significant microstructure changes over one month. Rheological investigation indicated that HIPEs with smaller droplet size and higher oil/water ratio exhibited higher surface elasticity and stability due to the tighter overall droplet packing. In addition, the EHL-XS stabilized O/W HIPEs could be used as encapsulates for the protection and delivery of the environmentally sensitive curcumin. It was found that such HIPEs encapsulation system exhibited superior UV protection of at least 30% higher than curcumin dispersed in bulk oil after 72 h of UV irradiation or 30 days at room temperature, respectively. Meanwhile, such HIPEs within curcumin also demonstrated good inhibitory activity against S. aureus.

Modulating Mechanical Properties of Collagen-Lignin Composites

Three-dimensional matrices of collagen type I (Col I) are widely used in tissue engineering applications for its abundance in many tissues, bioactivity with many cell types, and excellent biocompatibility. Inspired by the structural role of lignin in a plant tissue, we found that sodium lignosulfonate (SLS) and an alkali-extracted lignin from switchgrass (SG) increased the stiffness of Col I gels. SLS and SG enhanced the stiffness of Col I gels from 52 to 670 Pa and 52 to 320 Pa, respectively, and attenuated shear-thinning properties, with the formulation of 1.8 mg/mL Col I and 5.0 mg/mL SLS or SG. In 2D cultures, the cytotoxicity of collagen-SLS to adipose-derived stromal cells was not observed and the cell viability was maintained over 7 days in 3D cultures. Collagen-SLS composites did not elicit immunogenicity when compared to SLS-only groups. Our collagen-SLS composites present a case that exploits lignins as an enhancer of mechanical properties of Col I without adverse cytotoxicity and immunogenicity for in vitro scaffolds or in vivo tissue repairs.

Lignin - An underutilized, renewable and valuable material for food industry

Lignin is the second most abundant biorenewable polymers only next to cellulose and is ubiquitous in various plant foods. In food industry, lignin often presented as a major component of by-products from plant foods. In the last decade, the food and nutritional interests of lignin attracted more and more attentions and great progresses have been accomplished. In the present review, the structure, physicochemical properties, dietary occurrence and preparation methods of lignin from food resources were summarized. Then, the versatile activities of food lignin were introduced under the subtitles of antioxidant, antimicrobial, antiviral, antidiabetic and other activities. Finally, the potential applications of food lignin were proposed as a food bioactive ingredient, an improver of food package films and a novel material in fabricating drug delivery vehicles and contaminant passivators. Hopefully, this review could bring new insights in exploiting lignin from nutrition- and food-directed views.

Lignin Modification Supported by DFT-Based Theoretical Study as a Way to Produce Competitive Natural Antioxidants

The valorization of lignins as renewable aromatic feedstock is of utmost importance in terms of the use of sustainable resources. This study provides a deductive approach towards market-oriented lignin-derived antioxidants by ascertaining the direct effect of different structural features of lignin on the reactivity of its phenolic OH groups in the radical scavenging reactions. The antioxidant activity of a series of compounds, modeling lignin structural units, was experimentally characterized and rationalized, using thermodynamic descriptors. The calculated O–H bond dissociation enthalpies (BDE) of characteristic lignin subunits were used to predict the modification pathways of technical lignins. The last ones were isolated by soda delignification from different biomass sources and their oligomeric fractions were studied as a raw material for modification and production of optimized antioxidants. These were characterized in terms of chemical structure, molecular weight distribution, content of the functional groups, and the antioxidant activity. The developed approach for the targeted modification of lignins allowed the products competitive with two commercial synthetic phenolic antioxidants in both free radical scavenging and stabilization of thermooxidative destruction of polyurethane films.

Enzyme-Lignin Nanocapsules Are Sustainable Catalysts and Vehicles for the Preparation of Unique Polyvalent Bioinks

Reactive lignin nanocapsules catalyze a pigmentation reaction to furnish an innovative type of sustainable polyvalent bioink. In this nanodevice, the pigment, vehicle, binder, and additive are included in a single confined spherical space. Bioinks with different shades of color, black, gray, yellow-like, pink-like, and red/brown hues, have been prepared by selecting the reactants and the pigmentation process. Lignin nanocapsules play multiple functions in the support and activation of the enzyme necessary for the synthesis of pigments. Lignin nanocapsules protected the melanin pigment from alkaline and UV-degradation treatment.

Preparation of organic acid lignin submicrometer particle as a natural broad-spectrum photo-protection agent

Valorization of lignin by-product is an urgent issue in the context of biorefinery. Lignin is a natural anti-UV active ingredient with great potential applications. In this study, a natural broad-spectrum photo-protection agent was prepared using lignin from organic acid extraction process. The submicrometer particles were prepared by dialysis lignin recovered from the pretreatments with organic acid extraction processes (formic acid, formic acid/hydrogen peroxide, and acetic acid/hydrogen peroxide/HCl) and they served as active ingredients in sunblock formulation. The structures of the lignin submicrometer particles were characterized by multiple spectroscopies. The submicrometer particles from organic acid lignin showed high capacities to enhance the sun protection factor values of lotion by 2.80-3.53 at the dosage of 5%, and the lotions containing lignin submicrometer particles had good UV-blocking properties. In addition, the UVA/UVB values (i.e., the ratio of absorbance at UVA to that at UVB) were in the range of 0.69-0.72 for the organic acid lignin submicrometer particles, indicating that they exhibited superior properties. The results indicated that the lignin submicrometer-based lotions with excellent antioxidant and UV protection capacities offered a natural source for sunblock cosmetics.

Synthesis of lignin based composites of TiO2 for potential application as radical scavengers in sunscreen formulation

Titanium dioxide (TiO₂) is added in sunscreens due to its ability to absorb ultraviolet (UV) light. However, upon irradiation of UV light, reactive oxygen species particularly hydroxyl radical which can damage human skin will be generated. In this study, lignin/TiO₂ composites were employed to quench the hydroxyl radicals generated by the TiO₂. The lignin was extracted from oil palm empty fruit bunch (OPEFB) via kraft and soda pulping processes. The kraft lignin composite was labelled as KL/TiO₂ whereas the soda lignin composite was labelled as SL/TiO₂. The lignins and the composites were characterized by FTIR, UV spectroscopy, ¹³C NMR, SEM, EDX, and XRD. The relative hydroxyl radical production of composites and TiO₂ were compared through photo-oxidation of coumarin to 7-hydroxycoumarin as a test medium. The effect of types and amounts of lignin used were studied. The KL/TiO₂ composite showed the least radical production due to higher phenolic hydroxyl content of kraft lignin. The activity of the hydroxyl radicals will be quenched when it abstract hydrogen atoms from the phenolic hydroxyl groups.

The use of fractionated Kraft lignin to improve the mechanical and biological properties of PVA-based scaffolds

The mechanical properties of poly(vinyl alcohol) (PVA)-based scaffolds were successfully improved. The improvements in mechanical properties correlated with the amount of Kraft lignin in PVA matrices. The critical property for any scaffold is its capacity to allow cells to ingrow and survive within its internal structure. The ingrowth of cells was tested using bioreactors creating simulated in vivo conditions. In the context of all the mentioned parameters, the most advantageous properties were exhibited by the scaffold containing 99 wt% PVA and 1 wt% Kraft lignin. The composites with 1 wt% Kraft lignin exhibited sufficient mechanical stability, a lack of cytotoxicity, and mainly the ability to allow the ingrowth of cells into the scaffold in a rotation bioreactor.

The mechanical properties of poly(vinyl alcohol) (PVA)-based scaffolds were successfully improved.

Binding of Lignin Nanoparticles at Oil-Water Interfaces: An Ecofriendly Alternative to Oil Spill Recovery

Synthetic amphiphiles used for managing large-scale oil spills have a toxic impact on the environment and marine life. Developing new oil spill recovery technologies is critical to minimize the environmental and ecological impact of such disasters. Here, we show that a mixture of lignin nanoparticles and 1-pentanol forms a biocompatible alternative to nondegradable, synthetic amphiphiles used for oil spill recovery. The pentanol in the mixture generates initial Marangoni flow and confines the spilled oil into a thick slick on the surface of water. While the alcohol solubilizes, lignin nanoparticles irreversibly adsorb onto the oil-water interface. We find that the lignin nanoparticle adsorption to the oil-water interface is governed by a combination of electrostatic, van der Waals, and hydrophobic interactions between the particles and the interface. These interactions, combined with interparticle electrostatic repulsion between nanoparticles adsorbed at the oil-water interface, drive the formation of a submonolayer. The submonolayer transforms into a film of jammed nanoparticles due to compressive stress acting on the interface upon the solubilization of pentanol. This interfacial layer of lignin nanoparticles restricts oil from respreading and locks the oil in its confined state. The herded state of the oil with the interfacial layer of nanoparticles facilitates safe removal of the spilled oil using mechanical methods. The study presents a new principle of using a mixture of heavy alcohol and biocompatible nanoparticles for oil herding applications, thus providing an ecofriendly alternative to oil spill recovery.

Preparation and characterization of thermo-sensitive gel with phenolated alkali lignin

Thermo-sensitive gel exhibits great potential industrial application. It has been widely used in tissue repair, drug release and water purification for its property of phase transition in response to external stimuli, reusability and biocompatibility. In this study, a novel lignin-based thermo-sensitive gel was synthesized with alkali lignin by two steps. Firstly, phenolated lignin (PPAL) was synthesized with purified alkali lignin (PAL) catalyzed by sulfuric acid. Subsequently, thermo-sensitive gel was achieved by thermal polymerization of phenolated alkali lignin and N-isopropylacrylamide (NIPAAm). Furthermore, the prepared hydrogels were characterized in terms of thermal behavior, interior morphology and their swelling behavior. Compared with PAL-based gel, the obtained PPAL-based gel exhibits a higher crosslinking density and lower critical solution temperature (LCST) due to the increase of reaction site and smaller space volume of the hydrophobic side groups grafted on NIPAAm. TGA data revealed that thermal stability of gel was enhanced (50% weight loss at ~380 °C) by using lignin as precursor. SEM images showed that a more regular interior morphology, better compressive strength was also found (PPAL0.05, 11.15 KPa). Furthermore, the swelling ratio of PPAL-based gel was lower than that of PAL-based gel due to its more complex structure.