Synthesis of soy protein–lignin nanofibers by solution electrospinning

Facile one-pot synthesis of fluorescent aminoclay and the applications for fluorescence sensing Cr2 O7 2

Here, we developed a facile one-pot strategy for the fabrication of fluorescent aminoclay (F-AC) through in situ solvothermal treatment of 3-aminopropyltrimethoxysilane, MgCl2 , and sodium ascorbate at 180°C for 6 h. The obtained F-AC exhibited blue emission, good water solubility, and satisfactory photostability. It was observed that Cr2 O7 2- could selectively quench the fluorescence of F-AC through the inner filter effect and static quenching process. As a result, a novel fluorescent F-AC-based nanosensor was constructed with good linearity in the range 0.1-75 μM. The nanosensor was successfully applied in real water samples with satisfactory results. This work not only provides a novel nanosensor for Cr2 O7 2- , but also highlights the F-AC's promising applications in wider fields due to the versatility and simplicity of the preparation strategy.

Recent advances in lignin-based carbon materials and their applications: A review

As the most abundant natural aromatic polymer, tens of million of tons of lignin produced in paper-making or biorefinery industry are used as fuel annually, which is a low-value utilization. Moreover, burning lignin results in large amounts of carbon dioxide and pollutants in the air. The potential of lignin is far from being fully exploited and the search for high value-added application of lignin is highly pursued. Because of the high carbon content of lignin, converting lignin into advanced carbon-based structural or functional materials is regarded as one of the most promising solutions for both environmental protection and utilization of renewable resources. Significant progresses in lignin-based carbon materials (LCMs) including porous carbon, activated carbon, carbon fiber, carbon aerogel, nanostructured carbon, etc., for various valued applications have been witnessed in recent years. Here, this review summarized the recent advances in LCMs from the perspectives of preparation, structure, and applications. In particular, this review attempts to figure out the intrinsic relationship between the structure and functionalities of LCMs from their recent applications. Hopefully, some thoughts and discussions on the structure-property relationship of LCMs can inspire researchers to stride over the present barriers in the preparation and applications of LCMs.

All-biodegradable soy protein isolate/lignin composite cross-linked by oxidized sucrose as agricultural mulch films for green farming

Microplastics produced from the discarded traditional non-degradable mulch film deteriorate the ecological environment and pose a great threat to human health. Developing eco-friendly and biodegradable materials to substitute traditional plastic mulch film highly contributed to the progress of green agriculture. Herein, a category of eco-friendly and all-biodegradable soy protein isolate (SPI)/oxidized sucrose (OS)/Lignin mulch film was innovatively proposed by employing OS as green cross-linker and lignin as nanofiller under chemical/physical interaction. The cross-linking effect and hydrogen bonds between biopolymers act as sacrificial bonds for energy dissipation and effectively reinforced the intermolecular interactions as well as tensile strength from 6.67 MPa of pristine SPI film to 8.45 MPa of SPI/OS/Lignin film. Moreover, the SPI/OS/Lignin mulch film also presented excellent UV-shielding, moisture retention, heat preservation effect and sustained urea release properties. Benefitting from the above-mentioned merits, higher germination rate of cabbage seed was achieved when the natural soil was covered by such multifunctional mulch film compared to traditional low-density PE film. Our findings paved a solid way in rational designing and fabricating eco-friendly, low-cost and all-biodegradable mulch film to facilitate the crops growth, boosting the development of green farming.

Multifunctional lignin-based nanocomposites and nanohybrids

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

Tuning the Adhesive Properties of Soy Protein Wood Adhesives with Different Coadjutant Polymers, Nanocellulose and Lignin

Commercial wood adhesives are based on products that contain formaldehyde; however, environmental and health concerns about formaldehyde emissions from wood products have influenced research and development efforts in order to find alternative, formaldehyde-free products for wood adhesives. In this work, different soy protein-based wood adhesives are proposed, and their performance is compared to commercial urea formaldehyde (UF) adhesive. Soy protein-based wood adhesives were prepared using either soy protein isolate (SPI) or soy protein flour (SF) with different coadjutant polymers: polyethylene oxide (PEO), hydroxypropyl methylcellulose (HPMC), cellulose nanofibrils (CNF) or polyvinyl alcohol (PVA) with and without addition of kraft lignin. The effects of the type of soy protein, solids content, coadjutant polymer and lignin addition were investigated. The wood adhesive formulations were tested on the bonding of hardwood (white maple) and softwood (southern yellow pine) and the dry shear strength of test specimens was measured according to method ASTM D905-08. The adhesive formulations with SPI achieved significantly higher values than those with SF. The dry shear strength of the adhesives varies depending on the coadjutant polymer, the wood species and the addition of lignin.

Advances in Fabricating the Electrospun Biopolymer-Based Biomaterials

Biopolymers formed into a fibrous morphology through electrospinning are of increasing interest in the field of biomedicine due to their intrinsic biocompatibility and biodegradability and their ability to be biomimetic to various fibrous structures present in animal tissues. However, their mechanical properties are often unsatisfactory and their processing may be troublesome. Thus, extensive research interest is focused on improving these qualities. This review article presents the selection of the recent advances in techniques aimed to improve the electrospinnability of various biopolymers (polysaccharides, polynucleotides, peptides, and phospholipids). The electrospinning of single materials, and the variety of co-polymers, with and without additives, is covered. Additionally, various crosslinking strategies are presented. Examples of cytocompatibility, biocompatibility, and antimicrobial properties are analyzed. Special attention is given to whey protein isolate as an example of a novel, promising, green material with good potential in the field of biomedicine. This review ends with a brief summary and outlook for the biomedical applicability of electrospinnable biopolymers.

Electrospinning Proteins for Wound Healing Purposes: Opportunities and Challenges

With the growth of the aging population worldwide, chronic wounds represent an increasing burden to healthcare systems. Wound healing is complex and not only affected by the patient's physiological conditions, but also by bacterial infections and inflammation, which delay wound closure and re-epithelialization. In recent years, there has been a growing interest for electrospun polymeric wound dressings with fiber diameters in the nano- and micrometer range. Such wound dressings display a number of properties, which support and accelerate wound healing. For instance, they provide physical and mechanical protection, exhibit a high surface area, allow gas exchange, are cytocompatible and biodegradable, resemble the structure of the native extracellular matrix, and deliver antibacterial agents locally into the wound. This review paper gives an overview on cytocompatible and biodegradable fibrous wound dressings obtained by electrospinning proteins and peptides of animal and plant origin in recent years. Focus is placed on the requirements for the fabrication of such drug delivery systems by electrospinning as well as their wound healing properties and therapeutic potential. Moreover, the incorporation of antimicrobial agents into the fibers or their attachment onto the fiber surface as well as their antimicrobial activity are discussed.

Soy protein isolate supplemented silk fibroin nanofibers for skin tissue regeneration: Fabrication and characterization

Biocompatible soy protein isolate/silk fibroin (SPI/SF) nanofibrous scaffolds were successfully fabricated through electrospinning a novel protein blend SPI/SF. Prepared nanofibers were treated with ethanol vapor to obtain an improved water-stable structure. Fabricated scaffolds were characterized through scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), UV-VIS spectrophotometry and image analysis. The mean diameters of SPI/SF electrospun fibers were observed ranging between 71 and 160 nm. The scaffolds were found significantly stable for a prolong duration at the room temperature as well as at 37 °C, when placed in phosphate buffered saline, nutrient medium, and lysozyme-containing solution. The potential of fabricated scaffolds for skin tissue regeneration was evaluated by in vitro culturing of standard cell lines i.e., fibroblast cells (L929-RFP (red fluorescent protein) and NIH-3T3) and melanocytes (B16F10). The outcomes revealed that all the fabricated nanofibrous scaffolds were non-toxic towards normal mammalian cells. In addition, healing of full-thickness wound in rats within 14 days after treatment with a nanofibrous scaffold demonstrated its suitability as a potential wound dressing material. Interestingly, we found that nanofibers induced a noticeable reduction in the proliferation rate of B16F10 melanoma cells.

Amphoteric Soy Protein-Rich Fibers for Rapid and Selective Adsorption and Desorption of Ionic Dyes

Uniquely amphoteric soy protein (SP)-rich ultra-fine fibers (231 nm average diameter) have been facilely electrospun from aq. colloids and rendered water-insoluble by heating (150 °C, 12 h) to be highly stable over 14 d (pH 7) as well as under extremely acidic to basic (pH 0-10, 2 d) or at boil (2 h) conditions. The SP-rich fibrous membranes are easily tuned to be charged either negatively by deprotonation above or positively by protonation below the 4.5 PI of SPs. This pH-responsive amphoterism has been demonstrated for rapid adsorption of either cationic or anionic dyes, selective adsorption of either dye from their mixtures, and repetitive adsorption/desorption to recover and reuse both dyes and membranes. Chemisorption and heterogeneous adsorption of ionic dyes was confirmed by close fitting to the pseudo-second-order kinetic model (R 2 = 0.9977-0.9999) and Freundlich adsorption isotherm (R 2 = 0.9879). This is the first report of water-resilient and pH-robust ultrafine fibrous membranes fabricated from aqueous colloids of neat globular SPs, the major byproducts of under-utilized edible oil and biodiesel. The natural polyampholyte origin, amphoterism, and green processing make these fibrous materials unique and versatile for many potential applications involving both anionic and cationic species.

Electrospinning and electrospraying technologies for food applications

Electrospinning and electrospraying are versatile techniques for the production of nano- to micro-scale fibers and particles. Over the past 2 decades, significant progresses have been made to advance the fundamental understandings of these electrohydrodynamic processes. Researchers have investigated different polymeric and non-polymeric substrates for producing submicron electrospun/electrosprayed materials of unique morphologies and physicochemical properties. This chapter provides an overview on the basic principles of electrospinning and electrospraying, highlighting the effects of key processing and solution parameters. Electrohydrodynamic phenomena of edible substrates, including polysaccharides (xanthan, alginate, starch, cyclodextrin, pullulan, dextran, modified celluloses, and chitosan), proteins (zein, what gluten, whey protein, soy protein, gelatin, etc.), and phospholipids are reviewed. Selected examples are presented on how ultrafine fibers and particles derived from these substrates are being exploited for food and nutraceutical applications. Finally, the challenges and opportunities of the electrostatic methods are discussed.

Nano-scale polysaccharide materials in food and agricultural applications

Potential applications of nanotechnology in food and agriculture include: (1) the encapsulation of functional compounds; (2) production of reinforcing materials; (3) delivery of nutraceuticals in foods; (4) food safety, for detection and control of chemical and microbiological risks; (5) active and intelligent food packaging; (6) incorporation of protective substances of seeds; (7) addition of nutrients in the soil; (8) use of controlled release pesticides. Natural polysaccharides and their derivatives are widely used in the production of nano-scale materials. This chapter examines, the use of polysaccharides, such as starch, cellulose, lignin, pectin, gums, and cyclodextrins for the production of nano-scale materials, including nanocrystals, nanoemulsions, nanocomplexes, nanocapsules, and nanofibers.

Synthesis and characterization of silver nanoparticles loaded poly(vinyl alcohol)-lignin electrospun nanofibers and their antimicrobial activity

In the present study, poly(vinyl alcohol) (PVA) - Acacia lignin (PL) nanofiber mats loaded with silver nanoparticles were prepared and characterized. In-situ synthesis of silver nanoparticles was accomplished using alkali lignin extracted from Acacia wood as a reducing agent. Ultrafine nanofiber mats of PL incorporated with silver nanoparticles were fabricated using the electrospinning technique. The fiber morphology of the resultant nanofiber was characterized using scanning electron microscopy. The average diameter of the nanofiber was in the range of 100 to 300 nm. The existence of silver nanoparticles was confirmed by X-ray diffraction analysis. The influence of silver nanoparticles on the polymer structure was investigated by mechanical and thermal properties analysis. The antimicrobial activity of the PL nanofibers containing silver nanoparticles was tested against Bacillus circulans (MTCC 7906) and Escherichia coli (MTCC 739) and showed significant results against both microorganisms. The results revealed that PL nanofiber containing silver nanoparticles may have potential applications as membrane filtration, antimicrobial fabrics and wound dressing material.

Facile Preparation of Self-Standing Hierarchical Porous Nitrogen-Doped Carbon Fibers for Supercapacitors from Plant Protein-Lignin Electrospun Fibers

This research aims to develop self-standing nitrogen-doped carbon fiber networks from plant protein-lignin electrospun fibrous mats for supercapacitors. The challenge in preparing carbon fiber from protein is to maintain a fibrous structure during carbonization process. Thus, lignin was incorporated with protein. At protein-to-lignin ratio of 50:50 to 20:80, the electrospun fibers maintained their structure after carbonization and formed self-standing carbon fiber mats. Stacked graphene layer structure was developed in the carbon fibers at a relatively low carbonization temperature (<1000 °C) without the use of catalysts, which might be derived from both lignin and protein. Graphene layer structure conferred the carbon fibers with superior conductivity. The optimized carbon fiber networks possessed excellent capacitance performance in 6 M KOH of 410 F/g at 1 A/g and good cyclic stability. Such good electrochemical properties were due to the well-engineered characteristics of the materials, including a hierarchical porous texture, heteroatoms (nitrogen and oxygen), and the stacked graphene layer structure. This research not only has provided a convenient way to develop carbon fibers from plant protein-lignin for N-doped supercapacitor electrodes, but also opportunity to add value to plant proteins and lignin as by-products of agricultural industry processing.

Stable nisin food-grade electrospun fibers

Most of antimicrobial peptides interact with food components decreasing their activity, which limit their successful incorporation into packaging material, functional foods and edible films. The aim of this work was to develop a nisin carrier. Nanofibers of amaranth protein and pullulan (50:50) loaded with nisin were obtained by electrospinning. The nanofibers morphology was determined by scanning electron microscopy and fluorescent microscopy. The molecular interactions were characterized by infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. The nisin loading efficiency as well as the antimicrobial activity against Leuconostoc mesenteroides were evaluated. The micrographs of the obtained materials exhibited smooth and continuous fibers with no defects characterized by diameters between 124 and 173 nm. The FTIR analysis showed intermolecular interactions mainly by hydrogen bonding. The electrospinning process improved the thermal properties of the polymeric mixture displacing the Tm peak to higher temperatures and increasing crystallinity. The antimicrobial activity of nisin in broth and agar against L. mesenteroides was maintained after incorporation into fibers. The results presented an outlook for the potential use of protein amaranth nanofibers when incorporating antimicrobials as a food preservation strategy.

Preparation of Silk Sericin/Lignin Blend Beads for the Removal of Hexavalent Chromium Ions

In the present study, novel adsorbents having high adsorption capability and reusability were prepared using agricultural by-products: silk sericin and lignin. Silk sericin and lignin blend beads were successfully prepared using simple coagulation methods for the removal of hexavalent chromium (Cr(VI)) from aqueous solution. A 1 M lithium chloride (LiCl)/dimethyl sulfoxide (DMSO) solvent system successfully dissolved both sericin and lignin and had sufficient viscosity for bead preparation. Compared to the conventional sericin bead adsorbent, sericin/lignin blend beads showed higher Cr(VI) adsorption capacity. The amount of lignin added to the adsorbent greatly affected the adsorption capacity of the beads, and a 50:50 sericin/lignin blend ratio was optimal. Adsorption behavior followed the Freundlich isotherm, which means the adsorption of Cr(VI) occurred on the heterogeneous surface. Cr(VI) adsorption capability increased with temperature because of thermodynamic-kinetic effects. In addition, over 90% of Cr(VI) ions were recovered from the Cr(VI) adsorbed sericin/lignin beads in a 1 M NaOH solution. The adsorption-desorption recycling process was stable for more than seven cycles, and the recycling efficiency was 82%. It is expected that the sericin/lignin beads could be successfully applied in wastewater remediation especially for hazardous Cr(VI) ions in industrial wastewater.