Silk-based Materials Research Articles

Progress in Multiscale Modeling of Silk Materials.

As a result of their hierarchical structure and biological processing, silk fibers rank among nature's most remarkable materials. The biocompatibility of silk-based materials and the exceptional mechanical properties of certain fibers has inspired the use of silk in numerous technical and medical applications. In recent years, computational modeling has clarified the relationship between the molecular architecture and emergent properties of silk fibers and has demonstrated predictive power in studies on novel biomaterials. Here, we review advances in modeling the structure and properties of natural and synthetic silk-based materials, from early structural studies of silkworm cocoon fibers to cutting-edge atomistic simulations of spider silk nanofibrils and the recent use of machine learning models. We explore applications of modeling across length scales: from quantum mechanical studies on model peptides, to atomistic and coarse-grained molecular dynamics simulations of silk proteins, to finite element analysis of spider webs. As computational power and algorithmic efficiency continue to advance, we expect multiscale modeling to become an indispensable tool for understanding nature's most impressive fibers and developing bioinspired functional materials.

Fine Structural Analysis of Degummed Fibroin Fibers Reveals Its Superior Mechanical Capabilities.

Bombyx mori silk fibroin fibers constitute a class of protein building blocks capable of functionalization and reprocessing into various material formats. The properties of these fibers are typically affected by the intense thermal treatments needed to remove the sericin gum coating layer. Additionally, their mechanical characteristics are often misinterpreted by assuming the asymmetrical cross-sectional area (CSA) as a perfect circle. The thermal treatments impact not only the mechanics of the degummed fibroin fibers, but also the structural configuration of the resolubilized protein, thereby limiting the performance of the resulting silk-based materials. To mitigate these limitations, we explored varying alkali conditions at low temperatures for surface treatment, effectively removing the sericin gum layer while preserving the molecular structure of the fibroin protein, thus, maintaining the hierarchical integrity of the exposed fibroin microfiber core. The precise determination of the initial CSA of the asymmetrical silk fibers led to a comprehensive analysis of their mechanical properties. Our findings indicate that the alkali surface treatment raised the Young's modulus and tensile strength, by increasing the extent of the fibers' crystallinity, by approximately 40 % and 50 %, respectively, without compromising their strain. Furthermore, we have shown that this treatment facilitated further production of high-purity soluble silk protein with rheological and self-assembly characteristics comparable to those of native silk feedstock, initially stored in the animal's silk gland. The developed approaches benefits both the development of silk-based materials with tailored properties and the proper mechanical characterization of asymmetrical fibrous biological materials made of natural building blocks.

Silk Revolution: Redefining Sericulture through Application of Precise Nanotechnologies

Human civilization has been intertwined with sericulture—the art and science of producing silk for centuries. The application of nanotechnology to sericulture techniques has created new opportunities to improve the quantity, quality and use of silk in recent decades. This abstract examines the numerous applications of nanotechnology in sericulture, with particular attention on how it affects the quality of silk fibers, the procedures involved in producing silk and the creation of cutting-edge materials derived from silk. By providing comprehensive control over the properties of silk at the molecular and atomic levels, nanotechnology, defined as the manipulation of matter at the nano scale, has completely transformed the silk industry. Improving the health and growth of silkworms is one of the main application areas. Silver nanoparticles, for example have been used to fight illnesses and strengthen silkworm’s immune systems, boosting the insect’s resilience against illness and optimizing silk yield. Furthermore, silk fiber quality has increased largely in substantial measure by nanotechnology. The mechanical, thermal and optical characteristics of silk fibers have been altered by researchers by adding nanoparticles during the spinning process. For example, adding nanoparticles to silk can increase its tensile strength, making it more durable and appropriate for a variety of industrial uses. Similarly, silk can be given antibacterial qualities by adding nanoscale compounds, increasing its shelf life and possible uses in medical textiles. Furthermore, the production of sophisticated silk-based materials with distinctive functions has been made easier by nanotechnology. Nanocomposites, which consist of nanoparticles embedded in silk matrices, have unique characteristics like improved electrical conductivity, controlled drug release, and greater biocompatibility. Silk-based materials have emerged as a result of these developments, finding use both in wearable electronics and biomedical devices.

Evaluating bio-physicochemical properties of raw powder prepared from whole larvae containing liquid silk of the domestic silkworm.

The domestic silkworm, Bombyx mori, has been widely used in silk production for centuries. It is also used as a bioreactor by the textile and pharmaceutical industries to mass produce recombinant bioactive proteins containing silk-based materials. Furthermore, silkworms are well-known as a source of food and have also been orally administered to prevent and treat several human disorders. In this study, we aimed to investigate the inherent bio-physicochemical properties of edible silkworms to accurately evaluate their clinical and nutritional potential. We prepared raw powder from whole larvae of silkworm. The yield rate of the powder derived from dried larvae was almost 100% (98.1-99.1% in replicates). As "percentage yield" translates to "Budomari" in Japanese, this raw powder was named "B100rw." We further prepared B100dn that was denatured through autoclaving. Thereafter, we examined whether B100rw sustained the original bio-physicochemical properties by comparing it with B100dn. There was no significant difference in nutritional content between B100rw and B100dn. B100rw contained proteins derived from silkworm larvae and mulberry leaves, whereas the proteins of B100dn were mostly degraded. On measuring the enzymatic activity of both powders using trehalase as an indicator enzyme, B100rw was found to maintain trehalase activity. B100rw also maintained a random coil conformation, similar to that of liquid silk. This suggested that B100rw sustained the unique bio-physicochemical properties of living larvae. These findings may facilitate the development of novel food products or orally administered vaccines.

Utilization of deep eutectic solvent as a degumming protocol for raw silk: Towards performance and mechanism elucidation

Degumming is the most critical step for the silk textile industry and the process of silk-based advanced materials. However, current common degumming techniques are largely limited because of insufficient efficiency, obvious hydrolysis damage and difficulty in long-term storage. Here, deep eutectic solvent (DES) constituted of choline chloride (ChCl) and urea was explored to Bombyx mori silk fibers degumming without combining any further treatment. Compared to traditional alkali methods, DES could quickly remove about 26.5 % of sericin in just 40 min, and its degumming efficiency hardly decrease after seven cycles. Owing to the “tear off” degumming mechanism of DES molecules with "large volume", the resulted sericin has a large molecular weight of 250 kDa. In addition, because of antibacterial activity and stabilizing effect, no aggregation occurred and strong bacterial growth inhibition was triggered in the obtained sericin/DES solution. Furthermore, thanks to the good retention of crystalline region and slight swelling of amorphous area, the sericin-free fibroin showed significant increases in moisture absorption and dye uptake, while maintaining good mechanical properties. Featured with high efficiency, reduction in water pollution, easy storage of sericin as well as high quality fibers, this approach is of great potential for silk wet processing.

Surfactant-assisted photo-crosslinked silk fibroin sponges: A versatile platform for the design of bone scaffolds

Critical size bone defects cannot heal without aid and current clinical approaches exhibit some limitations, underling the need for novel solutions. Silk fibroin, derived from silkworms, is widely utilized in tissue engineering and regenerative medicine due to its remarkable properties, making it a promising candidate for bone tissue regeneration in vitro and in vivo. However, the clinical translation of silk-based materials requires refinements in 3D architecture, stability, and biomechanical properties.In earlier research, improved mechanical resistance and stability of chemically crosslinked methacrylate silk fibroin (Sil-Ma) sponges over physically crosslinked counterparts were highlighted. Furthermore, the influence of photo-initiator and surfactant concentrations on silk properties was investigated. However, the characterization of sponges with Sil-Ma solution concentrations above 10 % (w/V) was hindered by production optimization challenges, with only cell viability assessed.This study focuses on the evaluation of methacrylate sponges' suitability as temporal bone tissue regeneration scaffolds. Sil-Ma sponge fabrication at a fixed concentration of 20 % (w/V) was optimized and the impact of photo-initiator (LAP) concentrations and surfactant (Tween 80) presence/absence was studied. Their effects on pore formation, silk secondary structure, mechanical properties, and osteogenic differentiation of hBM-MSCs were investigated. We demonstrated that, by tuning silk sponges' composition, the optimal combination boosted osteogenic gene expression, offering a strategy to tailor biomechanical properties for effective bone regeneration. Utilizing Design of Experiment (DoE), correlations between sponge composition, porosity, and mechanical properties are established, guiding tailored material outcomes. Additionally, correlation matrices elucidate the microstructure's influence on gene expressions, providing insights for personalized approaches in bone tissue regeneration.

Hydrogels based on recombinant spidroin stimulate proliferation and migration of human cornea cells

This article presents the results of studying the impact of recombinant spidroin hydrogel on posterior epithelial cells and human corneal keratocytes in an in vitro experiment. The World Health Organization in its studies has established a high prevalence of corneal injuries among the population of developing countries. In recent years, various technologies have been proposed to restore the damaged surface of the cornea. The use of biodegradable silk-based materials, such as spidroins is one of the main parts of scientific research of corneal regeneration. Spidroinsare well known for their optimal balance of strength and elasticity, which, given their biological compatibility, non-immunogenicity and biodegradability, allows them to be used as a biomaterial for tissue engineering and regenerative medicine. In this reason a detailed assessment of the cytotoxicity of hydrogels based on recombinant rS2/12-RGDS spidroinon the epithelial cells and keratocytes was performed here, taking into attention possible changes of the phenotype and migratory activity of these cells. This study demonstrates the promise and therapeutic potential of hydrogels based on recombinant spidroin.

Review of Spider Silk Applications in Biomedical and Tissue Engineering.

This review will present the latest research related to the production and application of spider silk and silk-based materials in reconstructive and regenerative medicine and tissue engineering, with a focus on musculoskeletal tissues, and including skin regeneration and tissue repair of bone and cartilage, ligaments, muscle tissue, peripheral nerves, and artificial blood vessels. Natural spider silk synthesis is reviewed, and the further recombinant production of spider silk proteins. Research insights into possible spider silk structures, like fibers (1D), coatings (2D), and 3D constructs, including porous structures, hydrogels, and organ-on-chip designs, have been reviewed considering a design of bioactive materials for smart medical implants and drug delivery systems. Silk is one of the toughest natural materials, with high strain at failure and mechanical strength. Novel biomaterials with silk fibroin can mimic the tissue structure and promote regeneration and new tissue growth. Silk proteins are important in designing tissue-on-chip or organ-on-chip technologies and micro devices for the precise engineering of artificial tissues and organs, disease modeling, and the further selection of adequate medical treatments. Recent research indicates that silk (films, hydrogels, capsules, or liposomes coated with silk proteins) has the potential to provide controlled drug release at the target destination. However, even with clear advantages, there are still challenges that need further research, including clinical trials.

Thick silk fibroin vascular graft: A promising tissue-engineered scaffold material for abdominal vein grafts in middle-sized mammals.

Abdominal vein replacement with synthetic tissue-engineered vascular grafts constructed from silk-based scaffold material has not been reported in middle-sized mammals. Fourteen canines that underwent caudal vena cava replacement with a silk fibroin (SF) vascular graft (15 mm long and 8 mm diameter) prepared with natural silk biocompatible thread were allocated to two groups, thin and thick SF groups, based on the graft wall thickness. The short-term patency rate and histologic reactions were compared. The patency rate at 2 weeks after replacement in the thin and thick SF groups was 50% and 88%, respectively (p = 0.04). CD31-positive endothelial cells covered the luminal surface of both groups at 4 weeks. The elastic modulus of the thick SF graft was significantly better than that of the thin SF graft (0.0210 and 0.0007 N/m2, p < 0.01). Roundness of thick SF groups (o = 0.8 mm) was better than thin SF (o = 2.0 mm). There was significant difference between the groups (p = 0.01). SF vascular grafts are a promising tissue-engineered scaffold material for abdominal venous system replacement in middle-sized mammals, with thick-walled grafts being superior to thin-walled grafts.

Green, Low-carbon Silk-based Materials in Water Treatment: Current State and Future Trends.

The improper and inadequate treatment of industrial, agricultural, and household wastewater exerts substantial pressure on the existing ecosystem and poses a serious threat to the health of both humans and animals. To address these issues, different types of materials have been employed to eradicate detrimental pollutants from wastewater and facilitate the reuse of water resources. Nevertheless, owing to the challenges associated with the degradation of these traditional materials post-use and their incompatibility with the environment, natural biopolymers have garnered considerable interest. Silk protein, as a biomacromolecule, exhibits advantageous characteristics including environmental friendliness, low carbon emissions, biodegradability, sustainability, and biocompatibility. Considering recent research findings, this comprehensive review outlines the structure and properties of silk proteins and offers a detailed overview of the manufacturing techniques employed in the production of silk-based materials (SBMs) spanning different forms. Furthermore, it conducts an in-depth analysis of the state-of-the-art SBMs for water treatment purposes, encompassing adsorption, catalysis, water disinfection, desalination, and biosensing. The review highlights the potential of SBMs in addressing the challenges of wastewater treatment and provides valuable insights into prospective avenues for further research.

Shape memory and hemostatic silk-laponite scaffold for alveolar bone regeneration after tooth extraction trauma

Persistent bleeding and the absence of alveolar bone stress following tooth loss can hinder socket healing, complicating future dental implant procedures, and potentially leading to neighboring tooth instability. Therefore, developing materials that promote alveolar bone regeneration and possess both hemostatic and osteogenic properties is crucial for preserving the extraction sites. This study introduces a silk-based laponite composite scaffold material with proficient hemostatic and osteogenic functions, and excellent shape-memory properties for efficient extraction- site filling. In vitro studies research demonstrated that the scaffold's inherent negative charge of the scaffold significantly enhanced blood coagulation and thrombin generation. Moreover, its porous structure and slightly rough inner surface promoted blood cell adhesion and, improved the hemostatic performance. Furthermore, the scaffold facilitated stem cell osteogenic differentiation by activating the TRPM7 channel through the released of magnesium ions. In vivo tests using rat models confirmed its effectiveness in promoting coagulation and mandibular regeneration. Thus, this study proposes a promising approach for post-extraction alveolar bone regenerative repair. The composite scaffold material, with its hemostatic and osteogenic capabilities and shape-memory features, can potentially enhance dental implant success and overall oral health.

Hydrogels Based on Recombinant Spidroin Stimulate Proliferation and Migration of Human Corneal Cells.

The effect of recombinant spidroin (RS) hydrogel (HG) on anterior epithelial cells and keratocytes of the human cornea was studied in vitro. Corneal injuries are highly prevalent in developing countries according to the World Health Organization. Various technologies have recently been proposed to restore the damaged surface of the cornea. Use of biodegradable silk-based materials, including recombinant analogs of the spider silk protein spidroin, is an important avenue of research in the field of wound healing and corneal regeneration. Spidroins are well known for their optimal balance of strength and elasticity. Given their biological compatibility, lack of immunogenicity, and biodegradability, spidroins provide a biomaterial for tissue engineering and regenerative medicine. HGs based on RS rS2/12-RGDS were therefore tested for cytotoxicity toward isolated corneal epithelial cells and keratocytes with regard to possible changes in cell phenotype and migratory activity. A promising outlook and therapeutic potential were demonstrated for RS-based HGs.

Bimodal Gating Mechanism in Hybrid Thin-Film Transistors Based on Dynamically Reconfigurable Nanoscale Biopolymer Interfaces.

In recent years, increased control over naturally-derived structural protein formulations and their self-assembly has enabled the application of high-resolution manufacturing techniques to silk-based materials, leading to bioactive interfaces with unprecedented miniaturized formats and functionalities. We present here a hybrid biopolymer-semiconductor device obtained by integrating nanoscale silk layers in a well-established class of inorganic field-effect transistors (silk-FETs). The devices offer two distinct modes of operation - either traditional field-effect or electrolyte-gated - enabled by the precisely controlled thickness, morphology and biochemistry of the integrated silk layers. The different operational modes are selectively accessed by dynamically modulating the free-water content within the nanoscale protein layer from the vapor phase. The utility of these hybrid devices is illustrated in a highly sensitive and ultrafast breath sensor, highlighting the opportunities offered by the integration of nanoscale biomaterial interfaces in conjunction with traditional semiconductor devices, enabling functional outcomes at the intersection between the worlds of microelectronics and biology. This article is protected by copyright. All rights reserved.

Silk wastes and autoclaved degumming as an alternative for a sustainable silk process

Silk degumming is considered the first point in the preparation of silk-based materials since this process could modify the silk fiber and the properties of its related products. This study evaluated the differences in morphology, secondary structure, amino acid content, thermal stability, and mechanical properties of two types of raw materials, defective cocoons (DC) and silk fibrous waste (SW), degummed by chemical (C) and autoclaving (A) methods. Subsequently, silk fibroin films were prepared by dissolving each type of degummed fibers, and thermal and structural films properties were determined. The findings demonstrated that autoclaving is an efficient alternative to remove silk sericin, as the resulting fibers presented improved structural, thermal, and mechanical properties compared to those obtained by the chemical method. For films preparation, autoclave resulted in a good option, but dissolution parameters need to be adjusted for defective cocoons. Furthermore, similarities between the physicochemical properties of fibers and films from both fibrous wastes suggest that SW is a promising raw material for producing fibrous resources and regenerated silk fibroin materials. Overall, these findings suggest new recycling methods for fibrous waste and by-products generated in the silk textile production process.

Unique Material Properties of Bombyx mori Silk Fiber Incorporated with 3-Azidotyrosine.

Silk fiber produced by the silkworm Bombyx mori is a nature-derived proteinous fiber with excellent mechanical strength and broad biocompatibility. To alter its material properties and make it more suitable for textile, biomedical, and electronics applications, chemical modifications and genetic engineering methods have been extensively studied. Here, we report that the translational incorporation of a synthetic amino acid, 3-azidotyrosine (3-AzTyr), into B. mori silk fiber can improve its material properties. Such an incorporation considerably increased the fiber's mechanical strength and remarkably changed its solubility, whereas its crystalline hierarchical structure was not perturbed, as shown by X-ray analyses. These changes were probably caused by the intra- and/or intermolecular crosslinkings involving the azido group of 3-AzTyr during the degumming process to remove a coating protein. These findings indicate that the incorporation of synthetic amino acids could be an efficient method to improve the properties of silk-based materials.

Utilization of Bioactive Silk Protein in the Development of Optical Devices: Recent Advancements and Applications.

Typically, materials used to create optical devices have chemical and physical properties that have been precisely designed for a narrowly defined purpose, allowing for changes in design to account for device variability. There is a growing need for devices built of materials with changeable optical responses, as optical systems are incorporated into platforms with much functionality. Regenerated silk fibroin is described in this article as an enabling gadget with an active optical response as a result of the inherent characteristics of proteins. Silk's capacity for controlled movement, to swell and shrink reversibly, alter conformation and degradation that is customizable, impacts both the shape and the response of the optical structure-representative silk-based gadgets. The diversity of silk material is shown and discussed in this paper, concentrating on architectures that show reconfigurable behavior, an optical waveguide that is physically temporary and provides reversible responses. Finally, innovative research directions for silk-based materials and optical devices are presented in this paper. Since ancient times, silk, a natural biopolymer, has been used as a repair material in medicine. In the past 20 years, it has attracted a lot of interest to be used in several biomedical applications. Various healthcare items with silk as their substrate have been developed thanks to significant advancements in silk biomaterial research. Silk is a fabric created from spider and silkworm cocoons. Hierarchical structures and conventional structural elements are present in them. Different silk types can be produced using certain methods, such as films, fibers, microspheres, sponges, and hydrogels. The structural characteristics of secondary proteins present in silk can also be modified. This paper investigates the use of silk in biomedical and optical applications, and examines the technical trend in electronic fields.

Silk‐based conductive materials for smart biointerfaces (2/2023)

Silk-based conductive materials are widely used in bio interface applications, such as artificial epidermal sensors, soft and implantable bioelectronics, and tissue/cell scaffolds. In this article, Fu and coworkers reviewed the advanced paradigms of these conductive silk materials, with perspectives on the application challenges.

Silk chemistry and biomedical material designs.

Silk fibroin has applications in different medical fields such as tissue engineering, regenerative medicine, drug delivery and medical devices. Advances in silk chemistry and biomaterial designs have yielded exciting tools for generating new silk-based materials and technologies. Selective chemistries can enhance or tune the features of silk, such as mechanics, biodegradability, processability and biological interactions, to address challenges in medically relevant materials (hydrogels, films, sponges and fibres). This Review details the design and utility of silk biomaterials for different applications, with particular focus on chemistry. This Review consists of three segments: silk protein fundamentals, silk chemistries and functionalization mechanisms. This is followed by a description of different crosslinking chemistries facilitating network formation, including the formation of composite biomaterials. Utility in the fields of tissue engineering, drug delivery, 3D printing, cell coatings, microfluidics and biosensors are highlighted. Looking to the future, we discuss silk biomaterial design strategies to continue to improve medical outcomes.

Application of long fibrous coconut silk-based porous carbon in flexible supercapacitor

All-solid-state flexible supercapacitors are considered to be one of the ideal candidates for energy storage in the next generation of wearable electronic devices due to their high capacitance performance and excellent mechanical flexibility. Biomass-based carbon materials are regarded as the ideal precursors for carbon-based electrode materials due to their wide sources, low cost, natural and abundant biological features. In this work, long-fiber coconut silk with vascular bundle structure was selected as the precursor, the controllable adjustment of the pore structure and conductive characteristics of the electrode material was achieved by changing the KOH activation temperature. The specific surface area of the activated carbon electrode material etched with KOH at 900 °C can reach 2794 m2·g−1. The high specific surface area and reasonable pore size distribution provide abundant active sites for the adsorption of electrolyte ions, which leads to the excellent electrode specific capacitance (2 mV·s−1，634 F·g−1，10.73 Wh·kg−1) of the symmetric flexible supercapacitor combined with PVA (polyvinyl alcohol)/H2SO4 gel electrolyte. At the same time, the long-fiber carbon skeleton has intrinsically high Young's modulus, which enables the flexible all-solid-state supercapacitor to maintain better electrochemical stability and mechanical durability under mechanical deformation, and it's retention rate can reach 101.5 % after 10,000 bending experiments at an inner angle of 140°. It proves the great advantages and potential of coconut silk-based biomass carbon materials in the field of preparing flexible supercapacitors, and promotes the development of energy storage units for next-generation wearable electronic devices.

Emerging Strategies in Stimuli-Responsive Silk Architectures.

The utilization of implantable devices beseeches highly invasive surgeries considering the adversaries in the insertion of large, impliable devices through the body channels, which necessitate the development of implantable devices using biocompatible shape memory polymers. Silk displays prodigious heterogeneity in its genetic structure and physical properties in accordance with the spinning and storage process, where proteins undergo folding and unfolding. The stimuli-responsive nature of silk can be explained with the help of the structural morphology and composition of the material, where the hydrogen bonds in β-sheet domains and amorphous region act as switch points and net points, respectively. This review provides a primary attempt to enswathe all the literature available to date on the stimuli-responsive nature of silk and silk-based materials as a natural and biodegradable alternative for commercially used synthetic shape memory materials taking their elastomeric nature and reduction in glass transition temperature into account. Further constitutive model using the continuum approach has been utilized to explain the anisotropic elasticity damping effect and plastic deformation based on the α-helix chains,β-sheets, and β-spiral structures. The practicability to develop biomedical devices such as patient-specific-injectable scaffolds, drug carriers,and artificial muscles has been encompassed in this article.