Silk fibroin (SF) as a natural biopolymer has become a popular material for biomedical applications due to its minimal immunogenicity, tunable biodegradability, and high biocompatibility. Nowadays, various techniques have been developed for the applications of SF in bioengineering. Most of the literature reviews focus on the SF-based biomaterials and their different forms of applications such as films, hydrogels, and scaffolds. SF is also valuable as a coating on other substrate materials for biomedicine; however, there are few reviews related to SF-coated biomaterials. Thus, in this review, we focused on the surface modification of biomaterials using SF coatings, demonstrated their various preparation methods on substrate materials, and introduced the latest procedures. The diverse applications of SF coatings for biomedicine are discussed, including bone, ligament, skin, mucosa, and nerve regeneration, and dental implant surface modification. SF coating is conducive to inducing cell adhesion and migration, promoting hydroxyapatite (HA) deposition and matrix mineralization, and inhibiting the Notch signaling pathway, making it a promising strategy for bone regeneration. In addition, SF-coated composite scaffolds can be considered prospective candidates for ligament regeneration after injury. SF coating has been proven to enhance the mechanical properties of the substrate material, and render integral stability to the dressing material during the regeneration of skin and mucosa. Moreover, SF coating is a potential strategy to accelerate nerve regeneration due to its dielectric properties, mechanical flexibility, and angiogenesis promotion effect. In addition, SF coating is an effective and popular means for dental implant surface modification to promote osteogenesis around implants made of different materials. Thus, this review can be of great benefit for further improvements in SF-coated biomaterials, and will undoubtedly contribute to clinical transformation in the future.
Biocompatible Materials/chemistry* ; Silk/chemistry* ; Fibroins/pharmacology* ; Dental Implants ; Osteogenesis ; Tissue Scaffolds/chemistry* ; Tissue Engineering/methods*

OBJECTIVES: To design and prepare silk fibroin/hyaluronic acid composite hydrogel. METHODS: The thiol modified silk fibroin and the double-bond modified hyaluronic acid were rapidly cured into gels through thiol-ene click polymerization under ultraviolet light condition. The grafting rate of modified silk fibroin and hyaluronic acid was characterized by ¹H NMR spectroscopy; the gel point and the internal microstructure of hydrogels were characterized by rheological test and scanning electron microscopy; the mechanical properties were characterized by compression test; the swelling rate and degradation rate were determined by mass method. The hydrogel was co-cultured with the cells, the cytotoxicity was measured by the lactate dehydrogenase method, the cell adhesion was measured by the float count method, and the cell growth and differentiation on the surface of the gel were observed by scanning electron microscope and fluorescence microscope. RESULTS: The functional group substitution degrees of modified silk fibroin and hyaluronic acid were 17.99% and 48.03%, respectively. The prepared silk fibroin/hyaluronic acid composite hydrogel had a gel point of 40-60 s and had a porous structure inside the gel. The compressive strength was as high as 450 kPa and it would not break after ten cycles. The water absorption capacity of the composite hydrogel was 4-10 times of its own weight. Degradation experiments showed that the hydrogel was biodegradable, and the degradation rate reached 28%-42% after 35 d. The cell biology experiments showed that the cytotoxicity of the composite gel was low, the cell adhesion was good, and the growth and differentiation of the cells on the surface of the gel were good. CONCLUSIONS The photocurable silk fibroin/hyaluronic acid composite hydrogel can form a gel quickly, and has excellent mechanical properties, adjustable swelling rate and degradation degree, good biocompatibility, so it has promising application prospects in biomedicine.
Fibroins/chemistry* ; Hydrogels/chemistry* ; Hyaluronic Acid/chemistry* ; Biocompatible Materials/chemistry* ; Click Chemistry ; Sulfhydryl Compounds ; Silk/chemistry*

Tendon/ligament injury is one of the most common impairments in sports medicine. The traditional treatments of damaged tissue repair are unsatisfactory, especially for athletes, due to lack of donor and immune rejection. The strategy of tissue engineering may break through these limitations, and bring new hopes to tendon/ligament repair, even regeneration. Silk is a kind of natural biomaterials, which has good biocompatibility, wide range of mechanical properties and tunable physical structures; so it could be applied as tendon/ligament tissue engineering scaffolds. The silk-based scaffold has robust mechanical properties; combined with other biological ingredients, it could increase the surface area, promote more cell adhesion and improve the biocompatibility. The potential clinical application of silk-based scaffold has been confirmed by in vivo studies on tendon/ligament repairing, such as anterior cruciate ligament, medial collateral ligament, achilles tendon and rotator cuff. To develop novel biomechanically stable and host integrated tissue engineered tendon/ligament needs more further micro and macro studies, combined with product development and clinical application, which will give new hope to patients with tendon/ligament injury.
Biocompatible Materials ; Humans ; Ligaments ; growth & development ; Regeneration ; Silk ; chemistry ; Tendons ; growth & development ; Tissue Engineering ; Tissue Scaffolds ; chemistry

To provide technical support for spider silk functional modification, we developed a simple and efficient functional platform via intein trans-splicing. Small ubiquitin-related modifier protein (SUMO) was fused to the recombinant spider silk protein (W2CT) by peptide bond via S0 split intein Ssp DnaB trans-splicing, resulting in a protein SUMOW2CT. However, incorporation of exogenous protein led to mechanical property defect and lower fiber yield, and also slowed down the fiber assembly velocity but no obvious differences in supercontraction and chemical resistance when compared with fibers from W2CT (W). SUMO protease digestion showed positive results on the fibers, indicating that the SUMO protein kept its native conformation and bioactive. Above all, this work provides a technical support for spider silk high simply and efficient functionalized modification.
Animals ; Inteins ; Protein Splicing ; Recombinant Proteins ; chemistry ; Silk ; chemistry ; Small Ubiquitin-Related Modifier Proteins ; chemistry ; Spiders ; Trans-Splicing

Due to its special sequence structure, spider silk protein has unique physical and chemical properties, mechanical properties and excellent biological properties. With the expansion of the application value of spider silk in many fields as a functional material, progress has been made in the studies on the expression of recombinant spider silk proteins through many host systems by gene recombinant techniques. Recombinant spider silk proteins can be processed into high performance fibers, and a wide range of nonfibrous morphologies. Moreover, for their excellent biocompatibility and low immune response they are ideal for biomedical applications. Here we review the process and mechanism of preparation in vitro, chemistry and genetic engineering modification on recombinant spider silk protein.
Animals ; Arthropod Proteins ; chemistry ; Protein Engineering ; Recombinant Proteins ; chemistry ; Silk ; chemistry ; Spiders

Functional designing of natural amino acids (NAA) has received considerable attention in recent years due to its excellent biocompatibility. A novel self-assembling NAA, peptide RAG-16, was designed by hybridizing the characteristic silk fibroin motif (Gly-Ala) with an ionic complementary peptide sequence (Arg-Ala-Asp-Ala) in our study. The self-assembly structure, viscoelastic property, and cyto compatibility of the peptide were investigated by atomic force microscopy, rheometer, Fourier transform infrared spectrum, and inverted fluorescence microscope. RAG-16 was able to form a three-dimensional compact network structure in water. High mechanical performance of the peptide hydrogel was found due to the increase of the silk I structure from inserted fibroin motif segment. Fluorescence staining showed that vast majority of MC3T3-E1 cells in the RAG-16 hydrogel could adhere to, survive, and distribute on different planes. To sum up, in this experiment, the functional designing of the NAA has exhibited its potential application in biomedical field.
Amino Acids ; chemistry ; Biocompatible Materials ; chemistry ; Fibroins ; chemistry ; Hydrogels ; chemistry ; Models, Molecular ; Nanostructures ; chemistry ; ultrastructure ; Peptides ; chemistry ; Silk ; chemistry

Three-dimensional poly (epsilon-caprolactone)/silk sericin (PCL/SS) porous nanofibrous scaffolds were prepared by electrospinning. The structure and properties of the scaffolds were characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Fourier Transform Infrared Spectroscopy (FTIR) and water contact angle instrument. Studies on cell adhension and proliferation were carried out by culturing human primary skin fibroblast cells (FEK4) on these scaffolds using SEM and MTS. The experimental results showed that the PCL/SS nanofibrous scaffolds with SS nanoparticles had porous non-woven mesh structure with nanofibrous cross-linked with each other. Fiber diameter was very uniform and precise, and the secondary structure of SS protein had not been changed. Furthermore, the capability of hydrophile increased with the SS addition, which improved FEK4 cells adhesion and proliferation on the scaffolds.
Biocompatible Materials ; chemistry ; Cell Adhesion ; drug effects ; Cells, Cultured ; Fibroblasts ; cytology ; Microscopy, Electron ; Nanofibers ; chemistry ; Polyesters ; chemistry ; Sericins ; chemistry ; Silk ; chemistry ; Spectroscopy, Fourier Transform Infrared ; Tissue Scaffolds ; chemistry

This study investigated whether elevated host immune capacity can inhibit T. gondii infection. For this purpose, we used silk protein extracted from Bombyx mori cocoons as a natural supplement to augment immune capacity. After silk protein administration to BALB/c mice for 6 weeks, ratios of T lymphocytes (CD4+ and CD8+ T-cells) and splenocyte proliferative capacities in response to Con A or T. gondii lysate antigen (TLA) were increased. Of various cytokines, which regulate immune systems, Th1 cytokines, such as IFN-gamma, IL-2, and IL-12, were obviously increased in splenocyte primary cell cultures. Furthermore, the survival of T. gondii (RH strain)-infected mice increased from 2 days to 5 or more days. In a state of immunosuppression induced by methylprednisolone acetate, silk protein-administered mice were resistant to reduction in T-lymphocyte (CD4+ and CD8+ T-cells) numbers and the splenocyte proliferative capacity induced by Con A or TLA with a statistical significance. Taken together, our results suggest that silk protein augments immune capacity in mice and the increased cellular immunity by silk protein administration increases host protection against acute T. gondii infection.
Animals ; Bombyx/*chemistry ; CD4-CD8 Ratio ; Cell Proliferation ; Cells, Cultured ; Cytokines/secretion ; Insect Proteins/*immunology ; Leukocytes, Mononuclear/immunology ; Male ; Mice ; Mice, Inbred BALB C ; Silk/immunology ; Spleen/immunology ; Survival Analysis ; Toxoplasma/*immunology/pathogenicity ; Toxoplasmosis, Animal/immunology/*prevention & control

In order to investigate the effect of Arg-Gly-Asp (RGD) peptide-modified silk biomaterial on the adhesion and proliferation of bone marrow-derived mesenchymal stem cells (MSCs), MSCs of third generation were seeded onto the surface of RGD-decorated silk (silk-RGD group), silk alone (silk group) or tissue culture plate (TCP group). After incubation for 4 or 12 h, MSCs were examined quantitatively by using precipitation method for cell attachment. The cell proliferation, which was defined as cell density, was compared among the three groups after culture for 1, 2, 3, and 4 days. Cell skeleton, which was labeled fluorescently, was observed under laser confocal microscope after 24 h of culture. The results showed that cell adhesion rate in silk-RGD group was higher than in silk group (P<0.05), but similar to that in TCP group after incubation for 4 or 12 h (P>0.05). There were no significant differences in the cell proliferation among the three groups at different time points (P>0.05 for all). Laser confocal microscopy revealed that in silk-RGD group, MSCs, strongly fluorescently stained, spread fully, with stress fibers clearly seen, while in silk group, actin filaments were sparsely aligned and less stress fibers were found. It was concluded that RGD peptide could improve the adhesion of MSCs to the silk scaffold, but had no impact on the proliferation of the cells.
Biocompatible Materials/*chemistry ; Bone Marrow Cells/cytology ; Cell Adhesion/drug effects ; Cell Proliferation/drug effects ; Mesenchymal Stem Cells/*cytology ; Oligopeptides/*chemistry ; *Silk/chemistry ; Tissue Scaffolds

OBJECTIVETo evaluate the effect of silk fibroin film for repairing urethral defect in rabbits.

METHODSTwenty-four male New Zealand rabbits were randomized into experimental group, control group I and control group II. In the experimental group, a urethral defect of 1.5 cm was induced in the 12 rabbits and repaired with silk fibroin film. The 6 rabbits in control group I without the surgically induced defect served as the sham operation group, and in control group II consisting of 6 rabbits the urethral defect of 1.5 cm was induced without repair. Histological observation and immunohistochemistry were conducted to examine the regenerative segments of the urethra at regular time points between 2 and 16 weeks postoperatively.

RESULTSThe 12 rabbits in the experimental group did not show signs of urethral stricture following the surgery. The implanted silk fibroin film for defect repair was degraded completely at 16 weeks and the defect was repaired with smooth urethral mucous membrane lining and orderly arranged smooth muscle cells. Immunohistochemistry identified the cells lining the defect area as the urethral epithelial cells.

CONCLUSIONSilk fibroin film can promote the repair of urethral defect by inducing the growth of the urethral epithelial cells and smooth muscle cells.

Animals ; Biocompatible Materials ; chemistry ; Fibroins ; chemistry ; Guided Tissue Regeneration ; methods ; Immunohistochemistry ; Male ; Membranes, Artificial ; Rabbits ; Random Allocation ; Regeneration ; Silk ; chemistry ; Tissue Engineering ; Urethra ; injuries ; physiopathology ; surgery ; Wound Healing