Protein-based Fibers Research Articles

Uric Acid Ingluviolith in a Budgerigar (Melopsittacus undulatus).

This clinical report describes an adult, female budgerigar (Melopsittacus undulatus) diagnosed with an ingluviolith. The patient presented for intermittent regurgitation, and a palpable foreign body was present in the crop. Radiographs showed a radiopaque foreign body, and computed tomography showed an approximately 16 × 12 mm (length 3 width) structure in the crop with a soft tissue and focally mineralized center and a 2-3 mm-thick mineral-attenuating shell. An ingluviotomy was performed. The stone was first analyzed using polarized optical crystallography, a method that cannot analyze uric acid salts, and was incorrectly deemed a cystine calculus. The calculus was then analyzed using infrared spectroscopy and x-ray diffractometry and was confirmed to be a shell of subcrystalline to monoclinic crystals of anhydrous uric acid (C5H4N4O3) encrusting aggregates of numerous, threadlike, protein-based fibers. This case presents new information regarding avian ingluviolithiasis. The large size of the calculus indicates formation in the crop, and coprophagia linked to stress is thought to be the potential reason for urate and feather ingestion.

Dynamic mechanism and structural property analysis of microfluidic-obtained pea protein fiber

Although protein-based fibers have been developed, the preparation of inexpensive, safe and environmentally friendly plant protein fibers is still a hot topic. Herein, we constructed the microfluidic chip to produce protein fiber using pea protein and a small amount of cellulose nanofibers. The results demonstrated that compared to pea protein alone, the pea protein-based fiber produced through microfluidic spinning exhibited a smooth and dense surface structure, good thermal stability, higher Zeta potential and antioxidant activity, and lower surface hydrophobicity and sensitization. Furthermore, we comprehensively revealed the dynamic formation mechanism of pea protein-based fiber. During the fiber preparation process, hydrodynamics led the protein and cellulose nanofibers to align gradually along the flow direction, enhancing their molecular orientation. Additionally, strong hydrodynamic shear force altered the protein structure, transitioning its spatial structure from random coil and α-helix to β-sheet, and promoting a binding of protein to cellulose nanofibers. This research may offer theoretical guidance for the application of pea protein-based fiber in the preparation of hypoallergenic protein-based fibers and the construction of foodborne delivery materials.

Plant protein fibers obtained by microfluidic spinning technology: An insight into the fabrication, characterization, and digestive characteristics

Although protein-based biomimetic fibers are available, green and inexpensive protein-based fibers remain a challenge to develop. Herein, a microfluidic chip was designed to prepare protein-based fibers using cellulose nanofibers and various plant-derived proteins, including wheat gluten, zein, soy protein, pea protein, and rice bran protein. Furthermore, a comprehensive elucidation of the plant protein fiber formation mechanism was conducted. The results showed that plant protein fibers prepared by microfluidic spinning had smooth surfaces, strong mechanical properties, high thermal stability and antioxidative activity, good digestibility, and low sensitization. Additionally, the strong hydrodynamic shear force produced during microfluidic spinning changed the secondary structure of the protein, which promoted the binding of protein molecules to cellulose nanofibers, thus enhancing the molecular orientation of both protein and nanofiber. Consequently, this study may facilitate the development of natural, environmentally friendly, and functional protein-based fibers.

Nucleotide-based regenerated fiber production using salmon (Oncorhynchus keta) milt waste by solution spinning

The use of nucleic acid-derived fibers has not been developed in contrast to the traditional use of polysaccharide- and protein-based fibers in daily life. Salmon, Oncorhynchus keta, is an abundant fishery resource, and its milt contains a huge amount of DNA. Most of the milt is discarded because it degrades easily and is unsuitable for food consumption. DNA-based fibers are expected to possess functionality and mechanical strength because DNA is a polyanion with a high molecular weight. Here, using DNA extracted from the salmon milt, we produced nucleotide-based fibers. A solution spinning system was applied using ethanol as a coagulant. Adding the salt to the dope solution reduced the solubility of DNA, which was essential for the successful spinning of DNA-based fibers. The obtained fibers became insoluble in water by ultraviolet (UV) exposure. Fibril-like structures were detected on the fracture surface, and humidity influenced the conformational structure. This study focuses on the bulk-scale production of biodegradable DNA-based fibers. Therefore, it can be used not only for clothing and filters but also as a functional material to remove harmful pollutants released into the ocean, such as heavy metal ions and aromatic derivatives.

Invasive mussels fashion silk-like byssus via mechanical processing of massive horizontally acquired coiled coils.

Zebra and quagga mussels (Dreissena spp.) are invasive freshwater biofoulers that perpetrate devastating economic and ecological impact. Their success depends on their ability to anchor onto substrates with protein-based fibers known as byssal threads. Yet, compared to other mussel lineages, little is understood about the proteins comprising their fibers or their evolutionary history. Here, we investigated the hierarchical protein structure of Dreissenid byssal threads and the process by which they are fabricated. Unique among bivalves, we found that threads possess a predominantly β-sheet crystalline structure reminiscent of spider silk. Further analysis revealed unexpectedly that the Dreissenid thread protein precursors are mechanoresponsive α-helical proteins that are mechanically processed into β-crystallites during thread formation. Proteomic analysis of the byssus secretory organ and byssus fibers revealed a family of ultrahigh molecular weight (354 to 467 kDa) asparagine-rich (19 to 20%) protein precursors predicted to form α-helical coiled coils. Moreover, several independent lines of evidence indicate that the ancestral predecessor of these proteins was likely acquired via horizontal gene transfer. This chance evolutionary event that transpired at least 12 Mya has endowed Dreissenids with a distinctive and effective fiber formation mechanism, contributing significantly to their success as invasive species and possibly, inspiring new materials design.

Effect of Coagulant Concentration on Soy Protein-Based Fiber for Meat Substitute by Wet Spinning Combined with Ionic Cross-Linking of Alginate

Effect of Coagulant Concentration on Soy Protein-Based Fiber for Meat Substitute by Wet Spinning Combined with Ionic Cross-Linking of Alginate

Advancements in bio-polymeric composite materials for active and intelligent food packaging: A comprehensive review

The current review focuses on the role of bio-composites, natural fibres, and clays in active and intelligent food packaging. Because of their biodegradability, sustainability, and regenerative nature, these materials present a potential solution to increasing environmental problems. Natural fibres, clays, and bio-composites considerably enhance packaging material’s mechanical characteristics, thermal stability, and barrier performance, allowing for improved food preservation. Natural fibres, such as starch-based, wool-based, silk-based, and protein-based fibres, actively interact with packed food, improving shelf life and quality. Moreover, their incorporation into intelligent packaging systems aids in monitoringfood safety factors in real-time. Natural clays aid in the controlled release of active chemicals such as antibacterial agents and antioxidants due to their layered structure and high absorption capability. The ongoing research in this field hints at the significant potential of these materials, moving towards a more sustainable and environmentally conscious future for food packaging.

Kinetic Analysis Reveals the Role of Secondary Nucleation in Regenerated Silk Fibroin Self-Assembly.

Silk proteins obtained from the Bombyx mori silkworm have been extensively studied due to their remarkable mechanical properties. One of the major structural components of this complex material is silk fibroin, which can be isolated and processed further in vitro to form artificial functional materials. Due to the excellent biocompatibility and rich self-assembly behavior, there has been sustained interest in such materials formed through the assembly of regenerated silk fibroin feedstocks. The molecular mechanisms by which the soluble regenerated fibroin molecules self-assemble into protein nanofibrils remain, however, largely unknown. Here, we use the framework of chemical kinetics to connect macroscopic measurements of regenerated silk fibroin self-assembly to the underlying microscopic mechanisms. Our results reveal that the aggregation of regenerated silk fibroin is dominated by a nonclassical secondary nucleation processes, where the formation of new fibrils is catalyzed by the existing aggregates in an autocatalytic manner. Such secondary nucleation pathways were originally discovered in the context of polymerization of disease-associated proteins, but the present results demonstrate that this pathway can also occur in functional assembly. Furthermore, our results show that shear flow induces the formation of nuclei, which subsequently accelerate the process of aggregation through an autocatalytic amplification driven by the secondary nucleation pathway. Taken together, these results allow us to identify the parameters governing the kinetics of regenerated silk fibroin self-assembly and expand our current understanding of the spinning of bioinspired protein-based fibers, which have a wide range of applications in materials science.

Soft, strong, tough, and durable protein-based fiber hydrogels

Load-bearing soft tissues normally show J-shaped stress-strain behaviors with high compliance at low strains yet high strength at high strains. They have high water content but are still tough and durable. By contrast, naturally derived hydrogels are weak and brittle. Although hydrogels prepared from synthetic polymers can be strong and tough, they do not have the desired bioactivity for emerging biomedical applications. Here, we present a thermomechanical approach to replicate the combinational properties of soft tissues in protein-based photocrosslinkable hydrogels. As a demonstration, we create a gelatin methacryloyl fiber hydrogel with soft tissue-like mechanical properties, such as low Young's modulus (0.1 to 0.3 MPa), high strength (1.1 ± 0.2 MPa), high toughness (9,100 ± 2,200 J/m3), and high fatigue resistance (2,300 ± 500 J/m2). This hydrogel also resembles the biochemical and architectural properties of native extracellular matrix, which enables a fast formation of 3D interconnected cell meshwork inside hydrogels. The fiber architecture also regulates cellular mechanoresponse and supports cell remodeling inside hydrogels. The integration of tissue-like mechanical properties and bioactivity is highly desirable for the next-generation biomaterials and could advance emerging fields such as tissue engineering and regenerative medicine.

Egg shell membrane based electrolyte gated oxide neuromorphic transistor

In recent years, the study of neuromorphic devices has received extensive attention. It is becoming an important branch of the development of artificial intelligence technology. At the same time, natural biomaterials have several priorities, such as biodegradability, good biocompatibility, and non-toxicity, and have important value in novel portable intelligent systems. The egg shell membrane (ESM) is a fiber scaffold composed of highly crosslinked collagen, glycoprotein and cysteine-rich eggshell membrane proteins. It has porous morphology, thermal stability, mechanical strength, etc. Therefore, these protein-based fiber membranes have several potential applications, including nanocatalysts, microbial fuel cells, and adsorption of toxic dyes. This study adopts ESM as electrolyte, exhibiting extremely high proton conductivity of about 6.4×10<sup>–3</sup> S/cm and extremely high electric-double-layer (EDL) capacitance of about 2.8 µF/cm<sup>2</sup> at room temperature. Thus, it has extremely strong interfacial EDL electrostatic modulation capability. Then, indium tin oxide EDL transistor is fabricated by using a single step masking processing and magnetron sputtering deposition technology. The device exhibits typical n-type output curves and transfer curves at low operating voltage. In addition, transfer curves are scanned twice. It is observed that the curves approach to each other quite well, indicating the good stabilities. Owing to the extremely strong proton gating effects, the device exhibits excellent electrical performances. Specifically, ON/OFF ratio, mobility and sub-threshold swing are estimated to be about 2.5×10<sup>6</sup>, about 3.2 cm<sup>2</sup>/(V·s), and about 213 mV/dec, respectively. With the unique interfacial EDL modulation activities of ESM, the transistor can mimic some important synaptic plasticity behaviors, such as excitatory postsynaptic current (EPSC) and paired pulse facilitation (PPF). With the increase of pre-synaptic spike amplitude, the EPSC value increases correspondingly. With the increase of pre-synaptic spike frequency, the EPSC grain increases, indicating the potentials in high-pass synaptic filtering. By loading 64 potentiation spikes and 64 depression spikes, multi-level synaptic weight can be updated, demonstrating potentiation activity and depression activity. Again, with the same potentiation spikes and depression spikes, synaptic weight value curves approach to each other quite well, indicating that the present ESM gated oxide neuromorphic transistor has good stability. Then, an artificial neural network is adopted to perform supervised learning with Modified National Institute of Standards and Technology (MNIST) database. For simulation, a two-layer multilayer perceptron (MLP) neural network with 400 input neurons, 100 hidden neurons and 10 output neurons is adopted. The best recognition accuracy is as high as 92.59%. The proposed ESM gated oxide neuromorphic transistors have certain potentials in low-cost biodegradable neuromorphic systems.

Robust Assembly of Cross-Linked Protein Nanofibrils into Hierarchically Structured Microfibers.

Natural, high-performance fibers generally have hierarchically organized nanosized building blocks. Inspired by this, whey protein nanofibrils (PNFs) are assembled into microfibers, using flow-focusing. By adding genipin as a nontoxic cross-linker to the PNF suspension before spinning, significantly improved mechanical properties of the final fiber are obtained. For curved PNFs, with a low content of cross-linker (2%) the fiber is almost 3 times stronger and 4 times stiffer than the fiber without a cross-linker. At higher content of genipin (10%), the elongation at break increases by a factor of 2 and the energy at break increases by a factor of 5. The cross-linking also enables the spinning of microfibers from long straight PNFs, which has not been achieved before. These microfibers have higher stiffness and strength but lower ductility and toughness than those made from curved PNFs. The fibers spun from the two classes of nanofibrils show clear morphological differences. The study demonstrates the production of protein-based microfibers with mechanical properties similar to natural protein-based fibers and provides insights about the role of the nanostructure in the assembly process.

Extensible and self-recoverable proteinaceous materials derived from scallop byssal thread

Biologically derived and biologically inspired fibers with outstanding mechanical properties have found attractive technical applications across diverse fields. Despite recent advances, few fibers can simultaneously possess high-extensibility and self-recovery properties especially under wet conditions. Here, we report protein-based fibers made from recombinant scallop byssal proteins with outstanding extensibility and self-recovery properties. We initially investigated the mechanical properties of the native byssal thread taken from scallop Chlamys farreri and reveal its high extensibility (327 ± 32%) that outperforms most natural biological fibers. Combining transcriptome and proteomics, we select the most abundant scallop byssal protein type 5-2 (Sbp5-2) in the thread region, and produce a recombinant protein consisting of 7 tandem repeat motifs (rTRM7) of the Sbp5-2 protein. Applying an organic solvent-enabled drawing process, we produce bio-inspired extensible rTRM7 fiber with high-extensibility (234 ± 35%) and self-recovery capability in wet condition, recapitulating the hierarchical structure and mechanical properties of the native scallop byssal thread. We further show that the mechanical properties of rTRM7 fiber are highly regulated by hydrogen bonding and intermolecular crosslinking formed through disulfide bond and metal-carboxyl coordination. With its outstanding mechanical properties, rTRM7 fiber can also be seamlessly integrated with graphene to create motion sensors and electrophysiological signal transmission electrode.

Silk Fibroin Scaffolds as Biomaterials for 3D Mesenchymal Stromal Cells Cultures

Silk fibroin (SF), a protein-based fiber extracted from Bombyx mori cocoons, has recently emerged with great potential for the biomedical field to be used as a biomaterial processable in a variety of formats and applications, due to its natural characteristics. The aims of the present study were to characterize the structural properties of the SF scaffolds, in the format of porous sponges, and to investigate their feasibility to support the adhesion of mesenchymal stromal/stem cells isolated from human Wharton’s jelly of the umbilical cord (WJ-MSC). Adhesion is a prerequisite for using the SF scaffold as biomaterial for supporting three-dimensional (3D) WJ-MSC cultures for several applications. The integration among micro-computed tomography, confocal analysis, and field emission scanning electron microscopy allowed carrying out a deep investigation based on quantitative morphological parameters and qualitative observations at high resolution. High levels of porosity, interconnection, and contact surface–volume ratio confirmed the appropriateness of the designed SF porous scaffolds as supports for cell cultures. WJ-MSC was demonstrated to be capable of adhering to and colonizing the SF scaffold applicable as a 3D cell culture system, of conducting in vitro experiments in a more controlled environment, and possibly of being used in tissue engineering, regenerative medicine, and applications in oncology.

Mechanically Strong Proteinaceous Fibers: Engineered Fabrication by Microfluidics

Lightweight and mechanically strong natural silk fibers have been extensively investigated over the past decades. Inspired by this research, many artificial spinning techniques (wet spinning, dry spinning, electrospinning, etc.) have been developed to fabricate robust protein fibers. As the traditional spinning methods provide poor control over the as-spun fibers, microfluidics has been integrated with these techniques to allow the fabrication of biological fibers in a well-designed manner, with simplicity and cost efficiency. The mechanical behavior of the developed fibers can be precisely modulated by controlling the type iop and size of microfluidic channel, flow rate, and shear force. This technique has been successfully used to manufacture a broad range of protein fibers, and can accelerate the production and application of protein fibers in various fields. This review outlines recent progress in the design and fabrication of protein-based fibers based on microfluidics. We first briefly discuss the natural spider silk-spinning process and the microfluidics spinning process. Next, the fabrication and mechanical properties of regenerated protein fibers via microfluidics are discussed, followed by a discussion of recombinant protein fibers. Other sourced protein fibers are also reviewed in detail. Finally, a brief outlook on the development of microfluidic technology for producing protein fibers is presented.

MutS protein-based fiber optic particle plasmon resonance biosensor for detecting single nucleotide polymorphisms.

A new biosensing method is presented to detect gene mutation by integrating the MutS protein from bacteria with a fiber optic particle plasmon resonance (FOPPR) sensing system. In this method, the MutS protein is conjugated with gold nanoparticles (AuNPs) deposited on an optical fiber core surface. The target double-stranded DNA containing an A and C mismatched base pair in a sample can be captured by the MutS protein, causing increased absorption of green light launching into the fiber and hence a decrease in transmitted light intensity through the fiber. As the signal change is enhanced through consecutive total internal reflections along the fiber, the limit of detection for an AC mismatch heteroduplex DNA can be as low as 0.49nM. Because a microfluidic chip is used to contain the optical fiber, the narrow channel width allows an analysis time as short as 15min. Furthermore, the label-free and real-time nature of the FOPPR sensing system enables determination of binding affinity and kinetics between MutS and single-base mismatched DNA. The method has been validated using a heterozygous PCR sample from a patient to determine the allelic fraction. The obtained allelic fraction of 0.474 reasonably agrees with the expected allelic fraction of 0.5. Therefore, the MutS-functionalized FOPPR sensor may potentially provide a convenient quantitative tool to detect single nucleotide polymorphisms in biological samples with a short analysis time at the point-of-care sites.

From fabric to tissue: Recovered wool keratin/polyvinylpyrrolidone biocomposite fibers as artificial scaffold platform.

Keratin extracted from wool fibers has recently gained attention as an abundant source of renewable, biocompatible material for tissue engineering and drug delivery applications. However, keratin extraction and processing generally require a copious use of chemicals, not only bearing consequences for the environment but also possibly compromising the envisioned biological outcome. In this study, we present, for the first time, keratin-PVP biocomposite fibers obtained via an all-water co-electrospinning process and explored their properties modulation as a result of different thermal crosslinking treatments. The protein-based fibers featured homogenous morphologies and average diameters in the range of 170-290nm. The thermomechanical stability and response to a wet environment can be tuned by acting on the curing time; this can be achieved without affecting the 3D fibrous network nor the intrinsic hydrophilic behavior of the material. More interestingly, our protein-based membranes treated at 170°C for 18h successfully sustained the attachment and growth of primary human dermal fibroblasts, a cellular model which can recapitulate more faithfully the physiological human tissue conditions. Our proposed approach can be viewed as pivotal in designing tunable protein-based scaffolds for the next generation of skin tissue growth devices.

Fabrication and Mechanical Properties of Engineered Protein-Based Adhesives and Fibers.

Protein-based structural biomaterials are of great interest for various applications because the sequence flexibility within the proteins may result in their improved mechanical and structural integrity and tunability. As the two representative examples, protein-based adhesives and fibers have attracted tremendous attention. The typical protein adhesives, which are secreted by mussels, sandcastle worms, barnacles, and caddisfly larvae, exhibit robust underwater adhesion performance. In order to mimic the adhesion performance of these marine organisms, two main biological adhesives are presented, including genetically engineered protein-based adhesives and biomimetic chemically synthetized adhesives. Moreover, various protein-based fibers inspired by spider and silkworm proteins, collagen, elastin, and resilin are studied extensively. The achievements in synthesis and fabrication of structural biomaterials by DNA recombinant technology and chemical regeneration certainly will accelerate the explorations and applications of protein-based adhesives and fibers in wound healing, tissue regeneration, drug delivery, biosensors, and other high-tech applications. However, the mechanical properties of the biological structural materials still do not match those of natural systems. More efforts need to be devoted to the study of the interplay of the protein structure, cohesion and adhesion effects, fiber processing, and mechanical performance.

Modulating the Mechanical Performance of Macroscale Fibers through Shear-Induced Alignment and Assembly of Protein Nanofibrils.

Protein-based fibers are used by nature as high-performance materials in a wide range of applications, including providing structural support, creating thermal insulation, and generating underwater adhesives. Such fibers are commonly generated through a hierarchical self-assembly process, where the molecular building blocks are geometrically confined and aligned along the fiber axis to provide a high level of structural robustness. Here, this approach is mimicked by using a microfluidic spinning method to enable precise control over multiscale order during the assembly process of nanoscale protein nanofibrils into micro- and macroscale fibers. By varying the flow rates on chip, the degree of nanofibril alignment can be tuned, leading to an orientation index comparable to that of native silk. It is found that the Young's modulus of the resulting fibers increases with an increasing level of nanoscale alignment of the building blocks, suggesting that the mechanical properties of macroscopic fibers can be controlled through varying the level of ordering of the nanoscale building blocks. Capitalizing on strategies evolved by nature, the fabrication method allows for the controlled formation of macroscopic fibers and offers the potential to be applied for the generation of further novel bioinspired materials.

Healing through Histidine: Bioinspired Pathways to Self-Healing Polymers via Imidazole⁻Metal Coordination.

Biology offers a valuable inspiration toward the development of self-healing engineering composites and polymers. In particular, chemical level design principles extracted from proteinaceous biopolymers, especially the mussel byssus, provide inspiration for design of autonomous and intrinsic healing in synthetic polymers. The mussel byssus is an acellular tissue comprised of extremely tough protein-based fibers, produced by mussels to secure attachment on rocky surfaces. Threads exhibit self-healing response following an apparent plastic yield event, recovering initial material properties in a time-dependent fashion. Recent biochemical analysis of the structure–function relationships defining this response reveal a key role of sacrificial cross-links based on metal coordination bonds between Zn2+ ions and histidine amino acid residues. Inspired by this example, many research groups have developed self-healing polymeric materials based on histidine (imidazole)–metal chemistry. In this review, we provide a detailed overview of the current understanding of the self-healing mechanism in byssal threads, and an overview of the current state of the art in histidine- and imidazole-based synthetic polymers.

Flammability Characteristics of Animal Fibers: Single Breed Wools, Alpaca/Wool, and Llama/Wool Blends

Animal protein-based fibers used in textiles often are assumed to have uniform properties independent of source, and yet are different when considering texture, structure, and color. Differences between fibers from animal species have been studied in regard to general flammability behavior, but differences between fibers from breeds of the same species have not been studied. Fibers from two sheep breeds (Jacob, CVM/Romeldale) and two camelids (Alpaca, Llama) were studied for flammability effects on fabrics hand knit from yarns made from these different fibers. A total of five different yarns were studied: 100% Jacob, 100% CVM/Romeldale, 100% Alpaca, 50% Llama/Merino wool, and 50% Alpaca/Merino wool. Flammability was studied with cone calorimeter, microcombustion calorimeter, and vertical flame spread techniques. The results from this limited study demonstrate that there are differences between fibers from different breeds and differences between species, but the differences cannot be easily explained on the basis of inherent heat release or chemistry of the fiber. Sometimes yarn density and the tightness of the knit have more of an effect on self-extinguishment in vertical flame spread tests than does fiber heat release/chemistry. Pure Alpaca fiber, however, displays self-extinguishing behavior and low heat release when subjected to combustion conditions. This may be related to the amount of sulfur in its chemical structure, and its ability to be spun into a yarn which yields a tighter hand-knit density.