With the development of tissue engineering, a variety of forms of silk fibroin (SF) scaffolds has been applied to research of constructing variety of organization based on cells, which has become scientific focus in recent years. In this paper we introduced the source and structure of SF and the fabrication method of the scaffold, and also address the SF application progress in several relevant fields of tissue engineering, such as bone, cartilage, skin, blood vessel and nerves. Finally, we discuss the future leading prospect of the SF in order to provide reference for subsequent research.
For a long period of time, silk fibroin has been applied in biomedical areas. Along with the development of biotechnology, new functions of silk fibroin are being found and developed. From the suture of surgery to the therapeutic drug and the ordinary tissue engineering frame to high grade frame with drug buffer system, exploitation of silk fibroin is constantly introduced with something new from the old ones. In our review, we summarize the applications of silk fibroin in tissue engineering, drug buffer system and medical care.
With silk fibroin and vancomycin (VCM) as carrier and drug model, respectively, we prepared silk fibroin microspheres (SFM) with different concentration using the water-in-oil emulsion solvent diffusion method. We further developed VCM loaded calcium sulfate hemihydrates (CSH)/SFM artificial bone composites. In this study, surface morphology of the materials was observed using scanning electron microscope (SEM). Structure of the materials was studied with Fourier transform infrared spectroscopy (FTIR). Antibacterial activity of the materials was validated with the inhibition zone test. Drug release property of materials was evaluated using ultraviolet/visible spectrophotometry. Mechanical property of the materials was tested using computer-controlled electronic universal testing machine. The results showed that silk fibroin concentration had no significant effect on molecular conformation and antibacterial property of the SFM. The average diameter of SFM increased and the release rate decreased gradually as the silk fibroin concentration increased. The release rate decreased and the compressive fracture work increased as the silk fibroin concentration increased when adding SFM to CSH. This composite had partly corrected the disadvantages of CSH including the high brittleness and initial burst release. The research would have a good application foreground in the clinical treatment of infectious bone defect.
Objective To review the research progress on silk fibroin (SF)-nerve guidance conduits (NGCs) for peripheral nerve injury (PNI) repair. Methods To review the recent literature on PNI and SF-NGCs, expound the concepts and treatment strategies of PNI, and summarize the construction of SF-NGCs and its application in PNI repair. Results Autologous nerve transplantation remains the “gold standard” for treating severe PNI. However, it’s clinical applications are constrained by the limitations of limited donors and donor area damage. Natural SF exhibits good biocompatibility, low immunogenicity, and excellent physicochemical properties, making it an ideal candidate for the construction of NGCs. SF-NGCs constructed using different technologies have been found to have better biocompatibility and bioactivity. Their configurations can facilitate nerve regeneration by enhancing regenerative guidance and axonal extension. Besides, the adhesion, proliferation and differentiation of neurons and Schwann cells related to PNI repair can be effectively promote by NGCs. This accelerates the speed of nerve regeneration and improves the efficiency of repair. In addition, SF-NGCs can be used as regenerative scaffolds to provide biological templates for nerve repair. Conclusion The biodegradable natural SF has been extensively studied and demonstrated promising application prospects in the field of NGCs. It might be an effective and viable alternative to the “gold standard” for PNI treatment.
Objective To investigate the cellular compatibil ity of polyvinyl alcohol (PVA)/wild antheraea pernyisilk fibroin (WSF), and to explore the feasibil ity for tendon tissue engineering scaffold in vitro. Methods The solutions of WSF (11%), PVA (11%), and PVA/WSF (11%) were prepared with 98% formic acid (mass fraction) at a mass ratio of 9 : 1. The electrospinning membranes of WSF, PVA, and PVA/WSF were prepared by electrostatic spinning apparatus. The morphologies of scaffolds were evaluated using scanning electronic microscope (SEM). The tendon cells were isolated from tail tendon of 3-dayold Sprague Dawley rats in vitro. The experiment was performed using the 3rd generation cells. The tendon cells (1 × 106/mL) were cocultured with PVA and PVA/WSF electrospinning film, respectively, and MTT test was used to assess the cell adhesion rate 4, 12 hours after coculture. The tendon cells were cultured in PVA and PVA/WSF extraction medium of different concentration (1, 1/2, and 1/4), respectively; and the absorbance (A) values were detected at 1, 3, 5, and 7 days to evaluate the cytotoxicity. The composite of tendon cells and the PVA or PVA/WSF scaffold were observed by HE staining at 7 days and characterized by SEM at 1,3, 5, and 7 days. Results The solution of WSF could not be used to electrospin; and the solution of PVA and PVA/WSF could be electrospun. After coculture of tendon and PVA or PVA/WSF electrospinning membranes, the cell adhesion rates were 26.9% ±0.4% and 87.0% ± 1.0%, respectively for 4 hours, showing significant difference (t=100.400, P=0.000); the cell adhesion rates were 35.2% ± 0.6% and 110.0% ± 1.7%, respectively for 12 hours, showing significant difference (t=42.500, P=0.000). The cytotoxicity of PVA/WSF was less significantly than that of PVA (P lt; 0.05) and significant difference was observed between 1/2 PVA and 1/4PVA (P lt; 0.05). HE staining and SEM images showed that the tendon cells could adhere to PVA and PVA/WSF scaffolds, but that the cells grew better in PVA/WSF scaffold than in PVA scaffold in vitro. Conclusion PVA/WSF electrospinning membrane scaffold has good cell compatibility, and it is expected to be an ideal scaffold of tendon tissue engineering.
In bone tissue engineering, fabrication of scaffold materials that are biodegradable with regenerative functions is one of the most important research fields. Silk fibroin exhibits many favorable characteristics used as scaffold materials. Among them, hybrid silk fibroin/inorganic composites prepared by biomimetic mineralization have better biocompatibility, biomechanical properties, and biodegradability. At the same time, the hybrid silk fibroin/inorganic materials have much better osteoinduction and conduction properties than silk fibroin. Here, the recent advances in the preparation of silk fibroin/silica hybrid materials by combination or biomimetic silicification are reviewed, and the future research prospects of silicification of silk fibroin are discussed.
ObjectiveTo explore the effect of silk fibroin/poly(L-lactic acid-co-e-caprolactone) [SF/P(LLA-CL)] nanofibrous scaffold on tendon-bone healing of rabbits.MethodsSF/P(LLA-CL) nanofibrous scaffold was fabricated by electrospinning methods. The morphology of the scaffold was observed by scanning electron microscope (SEM). Pre-osteoblasts MC3T3-E1 cells were seeded on the scaffold and cultured for 1, 3, and 5 days. Cell adhesion and proliferation were also observed by SEM. Meanwhile, twenty-four New Zealand white rabbits were randomly divided into the autogenous tendon group (control group) and the autogenous tendon wrapped with SF/P(LLA-CL) scaffold group (experimental group), with twelve rabbits in each group. An extra-articular model was established, the effect was evaluated by histological examination and mechanical testing.ResultsThe morphology of SF/P(LLA-CL) nanofibrous scaffold was random, with a diameter of (219.4±66.5) nm. SEM showed that the MC3T3-E1 cells seeded on the scaffold were in the normal shape, growing well, and proliferating with time course. The results of histological examination showed that inflammatory cells infltrated into the graft-host bone interface at 6 weeks after operation in both groups. Besides, the width of interface showed no significant difference between groups. At 12 weeks after operation, protruding new bone tissue could be observed at the interface in the experimental group, while scar tissue but no new bone tissue could be seen at the interface in the control group. Mechanical testing showed that there was no significant difference in the failure load and the stiffness between groups at 6 weeks after operation (P>0.05). The failure load and the stiffness in the experimental group were significantly higher than those in the control group at 12 weeks after operation (P<0.05).ConclusionThe SF/P(LLA-CL) nanofibrous scaffold has good cell biocompatibility and can effectively promote tendon-bone healing, thus providing new method for modifying graft for ACL reconstruction in the clinical practice.
Objective To prepare the silk fibroin microcarrier loaded with clematis total saponins (CTS) (CTS-silk fibroin microcarrier), and to investigate the effect of microcarrier combined with chondrocytes on promoting rabbit knee articular cartilage defects repair. Methods CTS-silk fibroin microcarrier was prepared by high voltage electrostatic combined with freeze drying method using the mixture of 5% silk fibroin solution, 10 mg/mL CTS solution, and glycerin. The samples were characterized by scanning electron microscope and the cumulative release amount of CTS was detected. Meanwhile, unloaded silk fibroin microcarrier was also prepared. Chondrocytes were isolated from knee cartilage of 4-week-old New Zealand rabbits and cultured. The 3rd generation of chondrocytes were co-cultured with the two microcarriers respectively for 7 days in microgravity environment. During this period, the adhesion of chondrocytes to microcarriers was observed by inverted phase contrast microscope and scanning electron microscope, and the proliferation activity of cells was detected by cell counting kit 8 (CCK-8), and compared with normal cells. Thirty 3-month-old New Zealand rabbits were selected to make bilateral knee cartilage defects models and randomly divided into 3 groups (n=20). Knee cartilage defects in group A were not treated, and in groups B and C were filled with the unloaded silk fibroin microcarrier-chondrocyte complexes and CTS-silk fibroin microcarrier-chondrocyte complexes, respectively. At 12 weeks after operation, the levels of matrix metalloproteinase 9 (MMP-9), MMP-13, and tissue inhibitor of MMP 1 (TIMP-1) in articular fluid were detected by ELISA. The cartilage defects were collected for gross observation and histological observation (HE staining and toluidine blue staining). Western blot was used to detect the expressions of collagen type Ⅱ and proteoglycan. The inflammatory of joint synovium was observed by histological staining and inducible nitric oxide synthase (iNOS) immunohistochemical staining. Results The CTS-silk fibroin microcarrier was spherical, with a diameter between 300 and 500 μm, a porous surface, and a porosity of 35.63%±3.51%. CTS could be released slowly in microcarrier for a long time. Under microgravity, the chondrocytes attached to the surface of the two microcarriers increased gradually with the extension of culture time, and the proliferation activity of chondrocytes at 24 hours after co-culture was significantly higher than that of normal chondrocytes (P<0.05). There was no significant difference in proliferation activity of chondrocytes between the two microcarriers (P>0.05). In vivo experiment in animals showed that the levels of MMP-9 and MMP-13 in group C were significantly lower than those in groups A and B (P<0.05), and the level of TIMP-1 in group C was significantly higher (P<0.05). Compared with group A, the cartilage defects in groups B and C were filled with repaired tissue, and the repaired surface of group C was more complete and better combined with the surrounding cartilage. Histological observation and Western blot analysis showed that the International Cartilage Repair Scoring (ICRS) and the relative expression levels of collagen type Ⅱ and proteoglycan in groups B and C were significantly better than those in group A, and group C was significantly better than group B (P<0.05). The histological observation showed that the infiltration of synovial inflammatory cells and hyperplasia of small vessels significantly reduced in group C compared with groups A and B. iNOS immunohistochemical staining showed that the expression of iNOS in group C was significantly lower than that in groups A and B (P<0.05).Conclusion CTS-silk fibroin microcarrier has good CTS sustained release effect and biocompatibility, and can promote the repair of rabbit cartilage defect by carrying chondrocyte proliferation in microgravity environment.
Recently, drug delivery materials have become the hotspot of medical study. Suitable delivery material plays an important role in constructing an excellent drug delivery system. Silk fibroin is a naturally occurring protein polymer with excellent biocompatibility, remarkable mechanical properties, biodegradability and outstanding processability. Due to its unique properties, silk fibroin has become a favorable carrier material for the incorporation and delivery of a range of therapeutic agents. Based on the structure and characteristics of silk fibroin, this article provides an overview of the recent research progress of silk fibroin used as drug delivery materials.
Objective To explore the construction and biocompatibility in vitro evaluation of the electrospun-graphene (Gr)/silk fibroin (SF) nanofilms. Methods The electrostatic spinning solution was prepared by dissolving SF and different mass ratio (0, 5%, 10%, 15%, and 20%) of Gr in formic acid solution. The hydrophilia and hydrophobic was analyzed by testing the static contact angle of electrostatic spinning solution of different mass ratio of Gr. Gr-SF nanofilms with different mass ratio (0, 5%, 10%, 15%, and 20%, as groups A, B, C, D, and E, respectively) were constructed by electrospinning technology. The structure of nanofilms were observed by optical microscope and scanning electron microscope; electrochemical performance of nanofilms were detected by cyclic voltammetry at electrochemical workstation; the porosity of nanofilms were measured by n-hexane substitution method, and the permeability were observed; L929 cells were used to evaluate the cytotoxicity of nanofilms in vitro at 1, 4, and 7 days after culture. The primary Sprague Dawley rats’ Schwann cells were co-cultured with different Gr-SF nanofilms of 5 groups for 3 days, the morphology and distribution of Schwann cells were identified by toluidine blue staining, the cell adhesion of Schwann cells were determined by cell counting kit 8 (CCK-8) method, the proliferation of Schwann cells were detected by EdU/Hoechst33342 staining. Results The static contact angle measurement confirmed that the hydrophilia of Gr-SF electrospinning solution was decreased by increasing the mass ratio of Gr. Light microscope and scanning electron microscopy showed that Gr-SF nanofilms had nanofiber structure, Gr particles could be dispersed uniformly in the membrane, and the increasing of mass ratio of Gr could lead to the aggregation of particles. The porosity measurement showed that the Gr-SF nanofilms had high porosity (>65%). With the increasing of mass ratio of Gr, the porosity and conductivity of Gr-SF nanofilm increased gradually, the value in the group A was significantly lower than those in groups C, D, and E (P<0.05). In vitro L929 cells cytotoxicity test showed that all the Gr-SF nanofilms had good biocompatibility. Toluidine blue staining, CCK-8 assay, and EdU/Hoechst33342 staining showed that Gr-SF nanofilms with mass ratio of Gr less than 10% could support the survival and proliferation of co-cultured Schwann cells. Conclusion The Gr-SF nanofilm with mass ratio of Gr less than 10% have proper hydrophilia, conductivity, porosity, and other physical and chemical properties, and have good biocompatibility in vitro. They can be used in tissue engineered nerve preparation.