Porous 3-D scaffolds from regeneratedAntheraea pernyi silk fibroin

Silk Fibroin and Its Nanocomposites for Wound Care: A Comprehensive Review

For most individuals, wound healing is a highly organized, straightforward process, wherein the body transitions through different phases in a timely manner. However, there are instances where external intervention becomes necessary to support and facilitate different phases of the body's innate healing mechanism. Furthermore, in developing countries, the cost of the intervention significantly impacts access to treatment options as affordability becomes a determining factor. This is particularly true in cases of long-term wound treatment and management, such as chronic wounds and infections. Silk fibroin (SF) and its nanocomposites have emerged as promising biomaterials with potent wound-healing activity. Driven by this motivation, this Review presents a critical overview of the recent advancements in different aspects of wound care using SF and SF-based nanocomposites. In this context, we explore various formats of hemostats and assess their suitability for different bleeding situations. The subsequent sections discuss the primary causes of nonhealing wounds, i.e., prolonged inflammation and infections. Herein, different treatment strategies to achieve immunomodulatory and antibacterial properties in a wound dressing were reviewed. Despite exhibiting excellent pro-healing properties, few silk-based products reach the market. This Review concludes by highlighting the bottlenecks in translating silk-based products into the market and the prospects for the future.

Therapeutic Agent-Loaded Fibrous Scaffolds for Biomedical Applications

Tissue engineering is a sophisticated field that involves the integration of various disciplines, such as clinical medicine, material science, and life science, to repair or regenerate damaged tissues and organs. To achieve the successful regeneration of damaged or diseased tissues, it is necessary to fabricate biomimetic scaffolds that provide structural support to the surrounding cells and tissues. Fibrous scaffolds loaded with therapeutic agents have shown considerable potential in tissue engineering. In this comprehensive review, we examine various methods for fabricating bioactive molecule-loaded fibrous scaffolds, including preparation methods for fibrous scaffolds and drug-loading techniques. Additionally, we delved into the recent biomedical applications of these scaffolds, such as tissue regeneration, inhibition of tumor recurrence, and immunomodulation. The aim of this review is to discuss the latest research trends in fibrous scaffold manufacturing methods, materials, drug-loading methods with parameter information, and therapeutic applications with the goal of contributing to the development of new technologies or improvements to existing ones.

Nonmulberry silk fibroin-based biomaterials: Impact on cell behavior regulation and tissue regeneration

Silk fibroin (SF) is a promising biomaterial due to its good biocompatibility, easy availability, and high mechanical properties. Compared with mulberry silk fibroin (MSF), nonmulberry silk fibroin (NSF) isolated from typical nonmulberry silkworm silk exhibits unique arginine-glycine-aspartic acid (RGD) sequences with favorable cell adhesion enhancing effect. This inherent property probably makes the NSF more suitable for cell culture and tissue regeneration-related applications. Accordingly, various types of NSF-based biomaterials, such as particles, films, fiber mats, and 3D scaffolds, are constructed and their application potential in different biomedical fields is extensively investigated. Based on these promising NSF biomaterials, this review firstly makes a systematical comparison between the molecular structure and properties of MSF and typical NSF and highlights the unique properties of NSF. In addition, we summarize the effective fabrication strategies from degummed nonmulberry silk fibers to regenerated NSF-based biomaterials with controllable formats and their recent application progresses in cell behavior regulation and tissue regeneration. Finally, current challenges and future perspectives for the fabrication and application of NSF-based biomaterials are discussed. Related research and perspectives may provide valuable references for designing and modifying effective NSF-based and other natural biomaterials. STATEMENT OF SIGNIFICANCE: There exist many reviews about mulberry silk fibroin (MSF) biomaterials and their biomedical applications, while that about nonmulberry silk fibroin (NSF) biomaterials is scarce. Compared with MSF, NSF exhibits unique arginine-glycine-aspartic acid sequences with promising cell adhesion enhancing effect, which makes NSF more suitable for cell culture and tissue regeneration related applications. Focusing on these advanced NSF biomaterials, this review has systematically compared the structure and properties of MSF and NSF, and emphasized the unique properties of NSF. Following that, the effective construction strategies for NSF-based biomaterials are summarized, and their recent applications in cell behavior regulations and tissue regenerations are highlighted. Furthermore, current challenges and future perspectives for the fabrication and application of NSF-based biomaterials were discussed.

Efficient Preconstruction of Three-Dimensional Graphene Networks for Thermally Conductive Polymer Composites

Electronic devices generate heat during operation and require efficient thermal management to extend the lifetime and prevent performance degradation. Featured by its exceptional thermal conductivity, graphene is an ideal functional filler for fabricating thermally conductive polymer composites to provide efficient thermal management. Extensive studies have been focusing on constructing graphene networks in polymer composites to achieve high thermal conductivities. Compared with conventional composite fabrications by directly mixing graphene with polymers, preconstruction of three-dimensional graphene networks followed by backfilling polymers represents a promising way to produce composites with higher performances, enabling high manufacturing flexibility and controllability. In this review, we first summarize the factors that affect thermal conductivity of graphene composites and strategies for fabricating highly thermally conductive graphene/polymer composites. Subsequently, we give the reasoning behind using preconstructed three-dimensional graphene networks for fabricating thermally conductive polymer composites and highlight their potential applications. Finally, our insight into the existing bottlenecks and opportunities is provided for developing preconstructed porous architectures of graphene and their thermally conductive composites.

The antigenicity of silk-based biomaterials: sources, influential factors and applications

Silk is an ancient material with essential roles in numerous biomedical applications, such as tissue regeneration and drug delivery, because of its excellent tunable mechanical properties and diverse physical structures. In addition to the necessary functionalities for biomedical applications, another critical factor for materials applied in biology is the appropriate immune interactions with the body. This review focuses on the immune responses of silk-based materials applied in biomedical applications, specifically antigenicity. The factors affecting the antigenicity of silk-based materials are complicated and are related to the composition and structural characteristics of the materials. At the same time, the composition of silk-based materials varies with its species sources, such as silkworms, spiders, honey bees, or engineered recombinant silk. Additionally, different processing methods are used to fabricate different material formats, such as films, hydrogels, scaffolds, particles, and fibers, resulting in different structural characteristics. Furthermore, the resulting body reactions are also different with different degrees of the immune response. Silk protein typically induces a mild immune response, and immunogenicity can play active roles in osteogenesis, angiogenesis, and protection from inflammation. However, there are some rare reports of severe immune responses caused by silk, which can result in an allergic response or tissue necrosis. The source of allergenicity in silk-based materials is currently under-studied and how to regulate and eliminate the overreaction of the immune system is essential for further applications. Overall, the diverse characteristics of silk-based materials mostly show beneficial bioresponses with mild immunogenicity, and the tunable properties make it applicable in immune-related biomedical applications.

Cleavable poly(ethylene glycol) branched chain-modified Antheraea pernyi silk fibroin as a gene delivery carrier

Aim: To obtain a gene carrier that can effectively deliver loaded therapeutic genes to tumor cells, avoid toxic effects on normal cells and reduce nonspecific adsorption of plasma proteins. Methods: The conjugate of poly(ethylene glycol) (PEG) and MMP2SSP (PEG-MMP2SSP) was covalently coupled to cationized Antheraea pernyi silk fibroin (CASF) through disulfide bond exchange reaction to obtain a PEG-MMP2SSP-modified CASF (CASFMP). Results: The PEG chains were effectively cleaved from the CASFMP by MMP2. CASFMP/pDNA complexes inhibited human fibrosarcoma cell proliferation, and its cytotoxicity to human normal embryonic kidney cells was significantly lower than that of poly(ethylenimine)/pDNA after coculturing with cells for 24 h. Conclusion: CASFMP is a promising compound for use in gene therapy.

Three-dimensional silk fibroin scaffolds incorporated with graphene for bone regeneration

Porous three-dimensional (3D) silk fibroin (SF) scaffolds were widely applied for bone regeneration and showed excellent biocompatibility and biodegradability. Recently graphene was developed for bone scaffolds due to its osteogenic properties. Thus, we combine the SF and graphene to improve the osteogenic properties of SF scaffolds. In our study, we explored the incorporation of SF scaffolds with graphene to develop osteogenic scaffolds capable of accelerating bone formation. The 3D SF scaffolds were fabricated with different contents of graphene (0, 0.5, and 2%). Fluorescence images showed that the graphene nanosheets were homogeneously dispersed in the SF scaffolds. The addition of graphene affected the microarchitecture of the scaffolds. The G/SF scaffolds were cocultured with rat bone marrow-derived mesenchymal stem cells (rBMSCs) for 21 days. The cell morphology and cell proliferation study suggested that 0 and 0.5% G/SF scaffolds displayed good cell proliferation. In addition, immunofluorescent staining (e.g., osteonectin, osteopontin, and osteocalcin) and ALP activities indicated that the osteogenic properties was more actively exhibited on 0.5% G/SF scaffolds compared with the other groups. Our results indicated that SF scaffolds incorporated with graphene could be an appropriate scaffold for bone tissue engineering.

Rapid regeneration of enamel-like-oriented inorganic crystals by using rotary evaporation

Enamel, the hardest tissue in the human body, has excellent mechanical properties, mainly due to its highly ordered spatial structure. Fabricating enamel-like structure is still a challenge today. In this work, a simple and highly efficient method was introduced, using the silk fibroin as a template to regulate calcium- and phosphate- supersaturated solution to regenerate enamel-like hydroxyapatite crystals on various substrates (enamel, dentin, titanium, and polyethylene) under rotary evaporation. The enamel-like zinc oxide nanorod array structure was also successfully synthesized using the aforementioned method. This strategy provides a new approach to design and fabricate mineral crystals with particular orientation coatings for materials.

Preparation and biological properties of silk fibroin/nano-hydroxyapatite/graphene oxide scaffolds with an oriented channel-like structure

A novel SF/nHAp/GO hybrid scaffold with oriented channel-like structure in bone tissue engineering.

Silk Fibroin-Based Biomaterials for Biomedical Applications: A Review

Since it was first discovered, thousands of years ago, silkworm silk has been known to be an abundant biopolymer with a vast range of attractive properties. The utilization of silk fibroin (SF), the main protein of silkworm silk, has not been limited to the textile industry but has been further extended to various high-tech application areas, including biomaterials for drug delivery systems and tissue engineering. The outstanding mechanical properties of SF, including its facile processability, superior biocompatibility, controllable biodegradation, and versatile functionalization have allowed its use for innovative applications. In this review, we describe the structure, composition, general properties, and structure-properties relationship of SF. In addition, the methods used for the fabrication and modification of various materials are briefly addressed. Lastly, recent applications of SF-based materials for small molecule drug delivery, biological drug delivery, gene therapy, wound healing, and bone regeneration are reviewed and our perspectives on future development of these favorable materials are also shared.

Green fabrication of porous silk fibroin/graphene oxide hybrid scaffolds for bone tissue engineering

The porous SF/GO scaffolds with moderate GO content could promote the proliferation of osteoblasts.

Antheraea pernyi silk fibroin-coated PEI/DNA complexes for targeted gene delivery in HEK 293 and HCT 116 cells

Polyethylenimine (PEI) has attracted much attention as a DNA condenser, but its toxicity and non-specific targeting limit its potential. To overcome these limitations, Antheraea pernyi silk fibroin (ASF), a natural protein rich in arginyl-glycyl-aspartic acid (RGD) peptides that contains negative surface charges in a neutral aqueous solution, was used to coat PEI/DNA complexes to form ASF/PEI/DNA ternary complexes. Coating these complexes with ASF caused fewer surface charges and greater size compared with the PEI/DNA complexes alone. In vitro transfection studies revealed that incorporation of ASF led to greater transfection efficiencies in both HEK (human embryonic kidney) 293 and HCT (human colorectal carcinoma) 116 cells, albeit with less electrostatic binding affinity for the cells. Moreover, the transfection efficiency in the HCT 116 cells was higher than that in the HEK 293 cells under the same conditions, which may be due to the target bonding affinity of the RGD peptides in ASF for integrins on the HCT 116 cell surface. This result indicated that the RGD binding affinity in ASF for integrins can enhance the specific targeting affinity to compensate for the reduction in electrostatic binding between ASF-coated PEI carriers and cells. Cell viability measurements showed higher cell viability after transfection of ASF/PEI/DNA ternary complexes than after transfection of PEI/DNA binary complexes alone. Lactate dehydrogenase (LDH) release studies further confirmed the improvement in the targeting effect of ASF/PEI/DNA ternary complexes to cells. These results suggest that ASF-coated PEI is a preferred transfection reagent and useful for improving both the transfection efficiency and cell viability of PEI-based nonviral vectors.

Silk fibroin biomaterials for tissue regenerations

Regeneration of tissues using cells, scaffolds and appropriate growth factors is a key approach in the treatments of tissue or organ failure. Silk protein fibroin can be effectively used as a scaffolding material in these treatments. Silk fibers are obtained from diverse sources such as spiders, silkworms, scorpions, mites and flies. Among them, silk of silkworms is a good source for the development of biomedical device. It possesses good biocompatibility, suitable mechanical properties and is produced in bulk in the textile sector. The unique combination of elasticity and strength along with mammalian cell compatibility makes silk fibroin an attractive material for tissue engineering. The present article discusses the processing of silk fibroin into different forms of biomaterials followed by their uses in regeneration of different tissues. Applications of silk for engineering of bone, vascular, neural, skin, cartilage, ligaments, tendons, cardiac, ocular, and bladder tissues are discussed. The advantages and limitations of silk systems as scaffolding materials in the context of biocompatibility, biodegradability and tissue specific requirements are also critically reviewed.

Electrospun eri silk fibroin scaffold coated with hydroxyapatite for bone tissue engineering applications

Natural biomaterials such as collagen, silk fibroin, and chitosan, and synthetic biopolymers such as polylactic acid, polycaprolactone, polyglycolic acid, and their copolymers are being used as scaffold for tissue engineering applications. In the present work, a fibrous mat was electrospun from eri silk fibroin (ESF). A composite of hydroxyapatite (Hap) and the ESF scaffold was prepared by soaking the ESF scaffold in a solution of calcium chloride and then in sodium diammonium phosphate. The average tensile stress of the pure ESF and hydroxyapatite-coated ESF scaffold (ESF-Hap) was found to be 1.84 and 0.378 MPa, respectively. Pure ESF and ESF-Hap scaffolds were evaluated for their characteristics by a themogravimetric analyzer and Fourier transform infrared spectroscope. The crystallinity and thermal stability of the ESF-Hap scaffold were found to be more than that of uncoated eri silk nanofiber scaffold. The water uptake of the pure ESF and ESF-Hap scaffolds was found to be 69% and 340%, respectively, in distilled water as well as phosphate buffer saline. The hemolysis percentage of both scaffolds was less than 5%, which indicate their good blood compatibility. The cytocompatibility studied by 3-(4,5-dimethyl) thiazol-2-yl-2,5-dimethyl tetrazolium bromide assay showed that the scaffold is biocompatible. To assess cell attachment and growth on the scaffold, human mesenchymal stem cells were cultured on the scaffolds. The results from scanning electron microscopy and fluorescent microscopy showed a notable cellular growth and favorable morphological features. Hence, the ESF-Hap scaffold is better suited for cell growth than the pure ESF scaffold.

Electrospun fibrous mats on lithographically micropatterned collectors to control cellular behaviors

Spatial arrangement of multiple cell types plays a critical role in maintaining the viability of cells and functionality of tissues. Micropatterning has been used to fabricate scaffolds to modulate cell distribution, growth, and functions for reconstructing the anisotropy in native tissues. In the current study, a glass substrate patterned with an electrically conductive circuit was prepared by lithography as a collector for electrospinning. Densely packed fibers were deposited on the top of silver strips and patterned fibrous mats were obtained with distinct ridge and groove areas. Orthogonal alignment was shown for fibers in the ridge and groove areas, and the pattern feature and fiber alignment were well maintained in the ridge during incubation of cells with patterned fibrous mats. Sequential confocal laser scanning from the top of cell-loaded fibrous mats indicated that a larger number of cells were spread in the ridge than that in the groove areas, and cells penetrated into the fibrous mats in the ridge. Microscopic observation and immunofluorescent staining indicated that cells and collagen deposition appeared to have distinct patterns on the fibrous scaffold and aligned along the directionality of fibers with an elongated morphology. It is concluded that lithography can provide the design flexibility of collectors with micrometer-scale precision patterning, and cells can be confined to precise locations, sizes, and shapes by the use of micropatterned fibrous scaffolds without any adverse effect on the cell viability and function. The results suggest the potential of patterned electrospun fibrous mats to construct complex tissues of well organized multiple cell types and with spatially distributed extracellular matrices.

Antheraea pernyi silk fiber: a potential resource for artificially biospinning spider dragline silk

The outstanding properties of spider dragline silk are likely to be determined by a combination of the primary sequences and the secondary structure of the silk proteins. Antheraea pernyi silk has more similar sequences to spider dragline silk than the silk from its domestic counterpart, Bombyx mori. This makes it much potential as a resource for biospinning spider dragline silk. This paper further verified its possibility as the resource from the mechanical properties and the structures of the A. pernyi silks prepared by forcible reeling. It is surprising that the stress-strain curves of the A. pernyi fibers show similar sigmoidal shape to those of spider dragline silk. Under a controlled reeling speed of 95 mm/s, the breaking energy was 1.04 x 10(5) J/kg, the tensile strength was 639 MPa and the initial modulus was 9.9 GPa. It should be noted that this breaking energy of the A. pernyi silk approaches that of spider dragline silk. The tensile properties, the optical orientation and the beta-sheet structure contents of the silk fibers are remarkably increased by raising the spinning speeds up to 95 mm/s.