Silk proteins in reconstructive surgery: Do they possess an inherent antibacterial activity? A systematic review

Bioactive silk fibroin hydrogels: Unraveling the potential for biomedical engineering

Silk fibroin (SF) has received special attention from the scientific community due to its noteworthy properties. Its unique chemical structure results in an uncommon combination of macroscopically useful properties, yielding a strong, fine and flexible material which, in addition, presents good biodegradability and better biocompatibility. Therefore, silk fibroin in various formats, appears as an ideal candidate for supporting biomedical applications. In this review, we will focus on the hydrogels obtained from silk fibroin or in combination with it, paying special attention to the synthesis procedures, characterization methodologies and biomedical applications. Tissue engineering and drug-delivery systems are, undoubtedly, the two main areas where silk fibroin hydrogels find their place.

Advancements in silk fibroin and silk sericin-based biomaterial applications for cancer therapy and wound dressing formulation: A comprehensive review

Silks are a class of proteins generated naturally by different arthropods, including silkworms, spiders, scorpions, mites, wasps, and bees. This review discusses the silk fibroin and silk sericin fabricated by Bombyx mori silkworm as versatile fibers. This silk fiber is predominantly composed of hydrophobic silk fibroin and hydrophilic silk sericin. Fibroin is defined as a structural protein that bestows silk with strength, while sericin is characterized as a gum-like protein, tying the two fibrous proteins together and endowing silk proteins with elasticity. Due to their versatile structures, biocompatibility, and biodegradability, they could be tailored into intricate structures to warrant particular demands. The intrinsic functional groups of both proteins enable their functionalization and cross-linking with various biomaterials to endow the matrix with favorable antioxidant and antibacterial properties. Depending on the target applications, they can be integrated with other materials to formulate nanofibrous, hydrogels, films, and micro-nanoparticles. Given the outstanding biological and controllable physicochemical features of fibroin and sericin, they could be exploited in pharmaceutical applications involving tissue engineering, wound repair, drug delivery, and cancer therapy. This review comprehensively discusses the advancements in the implementation of different formulations of silk fibroin and sericin in wound healing and drug delivery systems, particularly for cancer treatment.

Exploring the mechanistic role of silk sericin biological and chemical conjugates for effective acute and chronic wound repair and related complications

OBJECTIVE

The current review is designed to elaborate and reveal the underlying mechanism of sericin and its conjugates of drug delivery during wounds and wound-related issues.

SIGNIFICANCE

Wound healing is a combination of different humoral, molecular, and cellular mechanisms. Various natural products exhibit potential in wound healing but among them, sericin, catches much attention of researchers due to its bio-functional properties such as being biodegradable, biocompatible, anti-oxidant, anti-bacterial, photo-protector, anti-inflammatory and moisturizing agent.

METHODS AND RESULTS

Sericin triggers the activity of anti-inflammatory cytokines which decrease cell adhesion and promote epithelial cell formation. Moreover, sericin enhances the anti-oxidant enzymes in the wounded area which scavenge the toxic consequences of reactive species (ROS).

CONCLUSIONS

This article highlights the mechanisms of how topical administration of sericin formulations along with 4-hexylresorcinol,\Chitosan\Ag@MOF-GO, polyvinyl alcohol (PVA), platelet lysate and UV photo cross-linked hydrogel sericin methacrylate which recruits a large number of cytokines on wounded area that stimulate fibroblasts and keratinocyte production as well as collagen deposition that led to early wound contraction. It also reviews the different sericin-based nanoparticles that play a significant role in rapid wound healing.

Silk Sericin and Its Composite Materials with Antibacterial Properties to Enhance Wound Healing: A Review

Wound infections may disrupt the normal wound-healing process. Large amounts of antibiotics are frequently used to prevent pathogenic infections; however, this can lead to resistance development. Biomaterials possessing antimicrobial properties have promising applications for reducing antibiotic usage and promoting wound healing. Silk sericin (SS) has been increasingly explored for skin wound healing applications owing to its excellent biocompatibility and antioxidant, antimicrobial, and ultraviolet-resistant properties. In recent years, SS-based composite biomaterials with a broader antimicrobial spectrum have been extensively investigated and demonstrated favorable efficacy in promoting wound healing. This review summarizes various antimicrobial agents, including metal nanoparticles, natural extracts, and antibiotics, that have been incorporated into SS composites for wound healing and elucidates their mechanisms of action. It has been revealed that SS-based biomaterials can achieve sustained antimicrobial activity by slow-release-loaded antimicrobial agents. The antimicrobial-loaded SS composites may promote wound healing through anti-infection, anti-inflammation, hemostasis, angiogenesis, and collagen deposition. The manufacturing methods, benefits, and limitations of antimicrobial-loaded SS materials are briefly discussed. This review aims to enhance the understanding of new advances and directions in SS-based antimicrobial composites and guide future biomedical research.

The Biologically Active Biopolymer Silk: The Antibacterial Effects of Solubilized Bombyx mori Silk Fibroin with Common Wound Pathogens

Antibacterial properties are desirable in wound dressings. Silks, among many material formats, have been investigated for use in wound care. However, the antibacterial properties of liquid silk are poorly understood. The aim of this study is to investigate the inherent antibacterial properties of a Bombyx mori silk fibroin solution. Silk fibroin solutions containing ≥ 4% w/v silk fibroin do not support the growth of two common wound pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. When liquid silk is added to a wound pad and placed on inoculated culture plates mimicking wound fluid, silk is bacteriostatic. Viability tests of the bacterial cells in the presence of liquid silk show that cells remain intact within the silk but could not be cultured. Liquid silk appears to provide a hostile environment for S. aureus and P. aeruginosa and inhibits growth without disrupting the cell membrane. This effect can be beneficial for wound healing and supports future healthcare applications for silk. This observation also indicates that liquid silk stored prior to processing is unlikely to experience microbial spoilage.

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.

Advances of regenerated and functionalized silk biomaterials and application in skin wound healing

The cocoon silk of silkworms (Bombyx mori) has multiple potential applications in biomedicine due to its good biocompatibility, mechanical properties, degradability, and plasticity. Numerous studies have confirmed that silk material dressings are more effective than traditional ones in the skin wound healing process. Silk material research has recently moved toward functionalized biomaterials and achieved remarkable results. Herein, we summarize the recent advances in functionalized silk materials and their efficacy in skin wound healing. In particular, transgenic technology has realized the specific expression of human growth factors in the silk glands of the silkworms, which lays the foundation for fabricating novel and low-cost functionalized materials. Without a green and safe preparation process, the best raw silk materials cannot be made into medically safe products. Therefore, we provide an overview of green and gentle approaches for silk degumming and silk sericin (SS) extraction. Moreover, we summarize and discuss the processing methods of silk fibroin (SF) and SS materials and their potential applications, such as burns, diabetic wounds, and other wounds. This review aims to enhance our understanding of new advances and directions in silk materials and guide future biomedical research.

Could an Anterior Cruciate Ligament Be Tissue-Engineered from Silk?

Silk has a long history as an exclusive textile, but also as a suture thread in medicine; nowadays, diverse cell carriers are manufactured from silk. Its advantages are manifold, including high biocompatibility, biomechanical strength and processability (approved for nearly all manufacturing techniques). Silk's limitations, such as scarcity and batch to batch variations, are overcome by gene technology, which allows for the upscaled production of recombinant "designed" silk proteins. For processing thin fibroin filaments, the sericin component is generally removed (degumming). In contrast to many synthetic biomaterials, fibroin allows for superior cell adherence and growth. In addition, silk grafts demonstrate superior mechanical performance and long-term stability, making them attractive for anterior cruciate ligament (ACL) tissue engineering. Looking at these promising properties, this review focusses on the responses of cell types to silk variants, as well as their biomechanical properties, which are relevant for ACL tissue engineering. Meanwhile, sericin has also attracted increasing interest and has been proposed as a bioactive biomaterial with antimicrobial properties. But so far, fibroin was exclusively used for experimental ACL tissue engineering approaches, and fibroin from spider silk also seems not to have been applied. To improve the bone integration of ACL grafts, silk scaffolds with osteogenic functionalization, silk-based tunnel fillers and interference screws have been developed. Nevertheless, signaling pathways stimulated by silk components remain barely elucidated, but need to be considered during the development of optimized silk cell carriers for ACL tissue engineering.

Structural Characteristics and Properties of Redissolved Silk Sericin

Silk sericin has garnered the attention of researchers as a promising biomaterial because of its good biocompatibility and high water retention. However, despite its useful properties, the poor storage stability of sericin has restricted its extensive use in biorelated applications. This study extracted sericin from silkworm cocoon, dried and stored it as a solid, and then dissolved it in hot water conditions to improve the storage stability of sericin for its use. The dissolution behavior of the extracted sericin solids was examined in conjunction with the structural characteristics and properties of dissolved sericin. Consequently, the results of solution viscosity, gel strength, crystallinity index, and thermal decomposition temperature indicated that the molecular weight (MW) of the dissolved sericin remained constant until a dissolution time of 5 min, following which deterioration was observed. The optimum condition of dissolution of the extracted sericin solid was 5 min at 90 °C. Conclusively, the extracted sericin could be stored in a dry state and dissolved to prepare redissolved sericin aqueous solution with the same MW as extracted sericin, thereby improving the storage stability of the sericin aqueous solution.

Sustainable Antibacterial Surgical Suture Based on Recycled Silk Resource by an Internal Combination of Inorganic Nanomaterials

The current antibacterial treatment methods of silk sutures can only be finished by surface modification, leading to problems of short antibacterial effects, easy slow-release consumption, prominent toxicity, and susceptibility to drug resistance. Speculatively, surgical sutures combining antibacterial material internally will possess a more promising efficacy. Hence, we extracted recycled regenerated silk fibroin (RRSF) from waste silk resources to make RRSF solutions. Internally combining with inorganic titanium dioxide (TiO₂) nanoparticles, we fabricated antibacterial RRSF-based surgical sutures. The morphologies, mechanical and antibacterial properties, biocompatibility tests, and in vivo experiments were carried out. The results showed that the surgical sutures with 1.25 wt % TiO₂ acquired 2.40 N knot strength (143 μm diameter) and achieved a sustainable antibacterial effect of 93.58%. Surprisingly, the sutures significantly reduced inflammatory reactions and promoted wound healing. Surgical sutures in this paper realize high-value recovery of waste silk fibers and provide a novel approach to preparing multifunctional sutures.