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*

Extracellular matrix (ECM) stiffness is closely related to the physiological and pathological states of breast tissue. The current study was aimed to investigate the effect of silk fibroin/collagen composite hydrogels with adjustable matrix stiffness on the growth and phenotype of normal breast epithelial cells. In this study, the enzymatic reaction of horseradish peroxidase (HRP) with hydrogen peroxide (H₂O₂) was used to change the degree of cross-linking of the silk fibroin solution. The rotational rheometer was used to characterize the composite hydrogel's biomechanical properties. Human normal mammary epithelial cell line MCF-10A were inoculated into composite hydrogels with various stiffness (19.10-4 932.36 Pa) to construct a three dimensional (3D) culture system of mammary epithelial cells. The CCK-8 assay was applied to detect the cell proliferation rate and active states in each group. Hematoxylin-Eosin (HE) staining and whole-mount magenta staining were used for histological evaluation of cell morphology and distribution. The results showed that with the increase of matrix stiffness, MCF-10A cells exhibited inhibited proliferation rate, decreased formation of acinus structures and increased branching structures. Meanwhile, with the increase of matrix stiffness, the polarity of MCF-10A cells was impeded. And the increase of matrix stiffness up-regulated the expression levels of mmp-2, mmp-3, and mmp-9 in MCF-10A cells. Among the genes related to epithelial-mesenchymal transition (EMT), the expression level of the epithelial marker gene E-cadherin was significantly down-regulated, while the interstitial cell marker gene Vimentin was up-regulated, and the expression levels of Snail, Wnt5b and Integrin β1 in the Wnt pathway were up-regulated. These results suggest that the silk fibroin/collagen composite hydrogels with adjustable matrix stiffness regulates the proliferation and the phenotype of MCF-10A cells. The effects of increased matrix stiffness may be closely related to the changes of the polar structures and function of MCF-10A cells, as well as the occurrence of ECM-remodeling and EMT.
Collagen/metabolism* ; Epithelial Cells/metabolism* ; Fibroins/pharmacology* ; Humans ; Hydrogels/metabolism* ; Hydrogen Peroxide ; Phenotype

As a biomaterial to be used for reparation in the case of trauma, the silk fibroin, particularly its effect on the transcription and expression of VEGF gene, is a concern. In this study, the ECV304 cell's growth shape and growth curve on the regenerated silk fibroin film were observed, and its VEGF secretion level was measured by ELISA test. It was found that the regenerated silk fibroin film did not interfere with ECV304 cell's growth and function. The L929 cell transfected with human VEGF gene grew on the regenerated silk fibroin film; the real-time quantitative RT-PCR method and ELISA test were used for detecting the transcription and expression of VEGF gene. The results showed the regenerated silk fibroin film did not interfere with the transcription and expression of VEGF gene. Therefore, the regenerated silk fibroin film is a safe biomaterial for inducing vascularization with no untoward effect on the reparation of trauma.
Animals ; Biocompatible Materials ; pharmacology ; Cell Line ; Endothelial Cells ; cytology ; metabolism ; Fibroins ; pharmacology ; Humans ; Silk ; pharmacology ; Transcription, Genetic ; Vascular Endothelial Growth Factor A ; genetics ; metabolism

OBJECTIVETo evaluate the feasibility of using polyporus silk fibroin as a kind of novel material for facial nerve regeneration.

METHODSThe porous silk fibroin conduit was used in the reconstruction of a 5 mm facial nerve gap of SD rat. Chitosan conduit was taken as control group. General observation, electrophysiological study, histological study and image analysis were performed 2, 4, 6 and 8 weeks postoperatively.

RESULTSThe facial nerve of SD rat regenerated successfully as time passed through. Mean CAP percentage of regenerated nerve in SF conduit was 24.94% +/- 5.73% 8 weeks postoperatively, which had no statistical significance with that of chitosan conduit group (P = 1.125). And the average number of myelinated myelinated nerve fibers in SF conduit was 62. 5 +/- 6. 3, which had statistical significance with that in chitosan conduit group (P = 0.016).

CONCLUSIONSThe porous silk fibroin conduit could effectively repair facial nerve defect and improve peripheral nerve functional recovery.

Animals ; Facial Nerve Injuries ; surgery ; Female ; Fibroins ; pharmacology ; therapeutic use ; Materials Testing ; Nerve Regeneration ; drug effects ; Rats ; Rats, Sprague-Dawley ; Wound Healing