Silk-based intelligent fibers and textiles: structures, properties, and applications

Multifunctional fibers represent a cornerstone of human civilization, playing a pivotal role in numerous aspects of societal development. Natural biomaterials, in contrast to synthetic alternatives, offer environmental sustainability, biocompatibility, and biodegradability. Among these biomaterials, natural silk is favored in biomedical applications and smart fiber technology due to its accessibility, superior mechanical properties, diverse functional groups, controllable structure, and exceptional biocompatibility. This review delves into the intricate structure and properties of natural silk fibers and their extensive applications in biomedicine and smart fiber technology. It highlights the critical significance of silk fibers in the development of multifunctional materials, emphasizing their mechanical strength, biocompatibility, and biodegradability. A detailed analysis of the hierarchical structure of silk fibers elucidates how these structural features contribute to their unique properties. The review also encompasses the biomedical applications of silk fibers, including surgical sutures, tissue engineering, and drug delivery systems, along with recent advancements in smart fiber applications such as sensing, optical technologies, and energy storage. The enhancement of functional properties of silk fibers through chemical or physical modifications is discussed, suggesting broader high-end applications. Additionally, the review addresses current challenges and future directions in the application of silk fibers in biomedicine and smart fiber technologies, underscoring silk's potential in driving contemporary technological innovations. The versatility and sustainability of silk fibers position them as pivotal elements in contemporary materials science and technology, fostering the development of next-generation smart materials.

Recent advances in sustainable nature-based functional materials for biomedical sensor technologies

The lightweight, low-density, and low-cost natural polymers like cellulose, chitosan, and silk have good chemical and biodegradable properties due to their individually unique structural and functional elements. However, the mechanical properties of these polymers differ from each other. In this scenario, chitosan lacks good mechanical properties than cellulose and silk. The synthesis of nano natural polymer and reinforcement with suitable chemical compounds as the development of nanocomposite gives them promising multidisciplinary applications. Many kinds of research are already published with innovative bio-derived polymeric functional materials (Bd-PFM) applications. Most research interest is carried out on health concerns. Lots of attention has been paid to biomedical applications of Bd-PFM as biosensors. This review aims to provide a glimpse of the nanostructures Bd-PFM biosensors.

Graphene oxide reinforced silk fibroin nanocomposite as an electroactive interface for the estimation of dopamine

The fabrication of 2D materials and polymer-based nanocomposites deposited on flexible conductive interfaces has unblocked new horizons to expedite reaction kinetics for developing highly selective and sensitive electrochemical biosensors. Herein, we developed a novel biosensing platform, comprising graphene oxide and a silk fibroin-based nanocomposite, drop-cast on a carbon cloth electrode. The fabricated interface was expected to be a robust and miniaturized sensing platform for precise detection of dopamine (DA). Characterization was performed by SEM, EDX, FTIR, XRD, UV-visible spectroscopy, contact angle measurement, fluorescence spectroscopy, particle size, and zeta potential analysis. CV, EIS, DPV, and chronoamperometry demonstrated the superior electrochemical properties of the working interface and revealed its enhanced active surface area, increased conductivity, and accelerated electron transfer rate. The designed interface exhibited low LoD (0.41 μM), admirable stability, good sensitivity (2.46 μA μM^-1 cm^-2), wide linearity ranging from 100-900 μM, excellent reproducibility, and superb selectivity against dopamine even in the presence of possible interfering analytes. These findings endorse the feasibility of the practical execution of such an integrated system in real sample analysis.

Study on a Natural Silk Cocoon Membrane-Based Versatile and Stable Immunosensing Platform via Directional Immunoaffinity Recognition

The development of immunosensing assays for in vitro diagnostics has attracted great attention in recent years. Various substrate materials and immobilization methods of biomolecules were exploited for immunosensors, but their bioactivity and longevity have been facing serious challenges. To address this limitation, we investigated a natural silk cocoon membrane as immunosensing substrate material. By using its intrinsic properties, the target biomolecules were immobilized on the membrane through directional immunoaffinity recognition. The silk cocoon membrane-based immunosensor showed great potential for both qualitative and quantitative immunoassays, through naked-eye observation or analyzing the change in red color intensity, respectively. The immunosensor exhibited significant detection capability for anti-D (titer 1:1024) sensitized red blood cells. The colorimetric responses of concentrations ranged from 1 μg/mL to 1 ng/mL, and the detection limit for anti-D was 3.4 ng/mL. The immunosensor also showed excellent stability for the immobilized antibodies when stored at 4 and 25 °C; the bioactivity remained unchanged or slightly declined within 40 weeks. Even at 37 °C, the bioactivity began to decline after 12 weeks. This current work highlights the potential of using the natural silk cocoon membrane as a substrate for a versatile and thermally stable immunosensing platform for application in immunoassays.

Advancements and Applications in the Composites of Silk Fibroin and Graphene-Based Materials

Silk fibroin and three kinds of graphene-based materials (graphene, graphene oxide, and reduced graphene oxide) have been widely investigated in biomedical fields. Recently, the hybrid composites of silk fibroin and graphene-based materials have attracted much attention owing to their combined advantages, i.e., presenting outstanding biocompatibility, mechanical properties, and excellent electrical conductivity. However, maintaining bio-toxicity and biodegradability at a proper level remains a challenge for other applications. This report describes the first attempt to summarize the hybrid composites’ preparation methods, properties, and applications to the best of our knowledge. We strongly believe that this review will open new doors for coming researchers.

3D Printing Silk-Based Bioresorbable Piezoelectric Self-Adhesive Holey Structures for In Vivo Monitoring on Soft Tissues

Flexible and biocompatible adhesives with sensing capabilities can be integrated onto human body and organ surfaces, characterized by complex geometries, thus having the potential to sense their physiological stimuli offering monitoring and diagnosis of a wide spectrum of diseases. The challenges in this innovative field are the following: (i) the coupling method between the smart adhesive and the soft human substrates, (ii) the bioresorbable behavior of the material, and (iii) the electrical exchange with the substrate. Here, we introduce a multifunctional composite by mixing silk fibroin, featuring piezoelectric properties, with a soluble plant-derived polyphenol (i.e., chestnut tannin) modified with graphene nanoplatelets. This material behaves as a glue on different substrates and gives rise to high elongation at break, conformability, and adhesive performances to gastrointestinal tissues in a rat model and favors the printability via extrusion-based 3D printing. Exploiting these properties, we designed a bioresorbable 3D printed flexible and self-adhesive piezoelectric device that senses the motility once applied onto a phantom intestine and the hand gesture by signal translation. Experimental results also include the biocompatibility study using gastrointestinal cells. These findings could have applicability in animal model studies, and, thanks to the bioresorbable behavior of the materials, such an adhesive device could be used for monitoring the motility of the gastrointestinal tract and for the diagnosis of motility disorders.

Graphene Oxide–Protein-Based Scaffolds for Tissue Engineering. Recent Advances and Applications

The field of tissue engineering is constantly evolving as it aims to develop bioengineered and functional tissues and organs for repair or replacement. Due to their large surface area and ability to interact with proteins and peptides, graphene oxides offer valuable physiochemical and biological features for biomedical applications and have been successfully employed for optimizing scaffold architectures for a wide range of organs, from the skin to cardiac tissue. This review critically focuses on opportunities to employ protein–graphene oxide structures either as nanocomposites or as biocomplexes and highlights the effects of carbonaceous nanostructures on protein conformation and structural stability for applications in tissue engineering and regenerative medicine. Herein, recent applications and the biological activity of nanocomposite bioconjugates are analyzed with respect to cell viability and proliferation, along with the ability of these constructs to sustain the formation of new and functional tissue. Novel strategies and approaches based on stem cell therapy, as well as the involvement of the extracellular matrix in the design of smart nanoplatforms, are discussed.

Biomedical applications of silkworm (Bombyx Mori) proteins in regenerative medicine (a narrative review)

Silk worm (Bombyx Mori) protein, have been considered as potential materials for a variety of advanced engineering and biomedical applications for decades. Recently, silkworm silk has gained significant importance in research attention mainly because of its remarkable and exceptional mechanical properties. Silk has already been shown to have unique interactions with cells in tissues through bio-recognition units. The natural silk contains fibroin and sericin and has been used in various tissues of the human body (skin, bone, nerve, and so on). Besides, silk also still has anti-cancer, anti-tyrosinase, anti-coagulant, anti-oxidant, anti-bacterial, and anti-diabetic properties. This article is supposed to describe the diverse biomedical capabilities of B. Mori silk as the appropriate biomaterial among the assorted natural and artificial polymers that are presently accessible, and ideal for usage in regenerative medicine fields.

A Review on Graphene Based Materials and Their Antimicrobial Properties

Graphene-based materials are found as excellent resources and employed as efficient anti-microbial agents, and they have been receiving significant attention from scientists and researchers in this regard. By giving special attention to recent applications of graphene-based materials, the current review is dedicated to unveiling the antimicrobial properties of graphene and its hybrid composites and their preparation methods. Different factors like the number of layers, concentration, size, and shape of the antibacterial activity are thoroughly discussed. Graphene-based materials could damage the bacteria physically by directly contacting the cell membrane or wrapping the bacterial cell. It can also chemically react to bacteria through oxidative stress and charge transfer mechanisms. This review explains such mechanisms thoroughly and summarizes the antibacterial applications (wound bandages, coatings, food packaging, etc.) of graphene and its hybrid materials.

Stretchable, Bio-Compatible, Antioxidant and Self-Powering Adhesives from Soluble Silk Fibroin and Vegetal Polyphenols Exfoliated Graphite

The development of bio-glues is still a challenging task, regarding adhesion on wet surfaces; often, high performance and adaption to complex geometries need to be combined in one material. Here, we report biocompatible adhesives obtained by blending regenerated silk (RS) with a soluble plant-derived polyphenol (i.e., chestnut tannin) that was also used to exfoliate graphite to obtain graphene-based RS/tannin (G-RS/T) composites. The resultant G-RS/T hybrid material exhibited outstanding stretchability (i.e., 400%) and high shear strength (i.e., 180 kPa), superior to that of commercial bio-glues, and showed sealant properties for tissue approximation. Moreover, we showed how such nanocomposites exhibit electromechanical properties that could potentially be used for the realization of green and eco-friendly piezoelectric devices. Finally, we demonstrate the in vitro glue’s biocompatibility and anti-oxidant properties that enable their utilization in clinical applications.

The Manufacture of Unbreakable Bionics via Multifunctional and Self-Healing Silk-Graphene Hydrogels

Biomaterials capable of transmitting signals over longer distances than those in rigid electronics can open new opportunities for humanity by mimicking the way tissues propagate information. For seamless mirroring of the human body, they also have to display conformability to its curvilinear architecture, as well as, reproducing native-like mechanical and electrical properties combined with the ability to self-heal on demand like native organs and tissues. Along these lines, a multifunctional composite is developed by mixing silk fibroin and reduced graphene oxide. The material is coined "CareGum" and capitalizes on a phenolic glue to facilitate sacrificial and hierarchical hydrogen bonds. The hierarchal bonding scheme gives rise to high mechanical toughness, record-breaking elongation capacity of ≈25 000%, excellent conformability to arbitrary and complex surfaces, 3D printability, a tenfold increase in electrical conductivity, and a fourfold increase in Young's modulus compared to its pristine counterpart. By taking advantage of these unique properties, a durable and self-healing bionic glove is developed for hand gesture sensing and sign translation. Indeed, CareGum is a new advanced material with promising applications in fields like cyborganics, bionics, soft robotics, human-machine interfaces, 3D-printed electronics, and flexible bioelectronics.

Graphene oxide and electroactive reduced graphene oxide-based composite fibrous scaffolds for engineering excitable nerve tissue

This study systematically investigates the role of graphene oxide (GO) and reduced GO (rGO)/silk-based composite micro/nano-fibrous scaffolds in regulating neuronal cell behavior in vitro, given the limited comparative studies on the effects of graphene family materials on nerve regeneration. Fibrous scaffolds can mimic the architecture of the native extracellular matrix and are potential candidates for tissue engineering peripheral nerves. Silk/GO micro/nano-fibrous scaffolds were electrospun with GO loadings 1 to 10 wt.%, and optionally post-reduced in situ to explore a family of electrically conductive non-woven silk/rGO scaffolds. Conductivities up to 4 × 10^-5 S cm^-1 were recorded in the dry state, which increased up to 3 × 10^-4 S cm^-1 after hydration. Neuronoma NG108-15 cells adhered and were viable on all substrates. Enhanced metabolic activity and proliferation were observed on the GO-containing scaffolds, and these cell responses were further promoted for electroactive silk/rGO. Neurite extensions up to 100 μm were achieved by day 5, with maximum outgrowth up to ~250 μm on some of the conductive substrates. These electroactive composite fibrous scaffolds exhibit potential to enhance the neuronal cell response and could be versatile supportive substrates for neural tissue engineering applications.