Regenerated Silk Fibroin Scaffolds Research Articles

Application of an ultrasound semi-quantitative assessment in the degradation of silk fibroin scaffolds in vivo

BackgroundResearch on the degradation of silk fibroin (SF) scaffolds in vivo lacks uniform and effective standards and experimental evaluation methods. This study aims to evaluate the application of ultrasound in assessing the degradation of SF scaffolds.MethodsTwo groups of three-dimensional regenerated SF scaffolds (3D RSFs) were implanted subcutaneously into the backs of Sprague-Dawley rats. B-mode ultrasound and hematoxylin and eosin (HE) staining were performed on days 3, 7, 14, 28, 56, 84, 112, 140, and 196. The cross-sectional areas for two groups of 3D RSFs that were obtained using these methods were semi-quantitatively analyzed and compared to evaluate the biodegradation of the implanted RSFs.ResultsThe 3D RSFs in the SF-A group were wholly degraded at the 28th week after implantation. In contrast, the 3D RSFs in the SF-B group were completely degraded at the 16th week. Ultrasonic examination showed that the echoes of 3D RSFs in both groups gradually decreased with the increase of the implantation time. In the early stages of degradation, the echoes of the samples were higher than the echo of the muscle. In the middle of degeneration, the echoes were equal to the echo of the muscle. In the later stage, the echoes of the samples were lower than that of the muscle. The above changes in the SF-B group were earlier than those in the SF-A group. Semi-quantitative analysis of the cross-sectional areas detected using B-mode ultrasound revealed that the degradations of the two 3D RSF groups were significantly different. The degradation rate of the SF-B group was found to be higher than that of the SF-A group. This was consistent with the semi-quantitative detection results for HE staining. Regression analysis showed that the results of the B-mode ultrasound and HE staining were correlated in both groups, indicating that B-mode ultrasound is a reliable method to evaluate the SF scaffold degradation in vivo.ConclusionsThis study suggests that B-mode ultrasound can clearly display the implanted SF scaffolds non-invasively and monitor the degradation of the different SF scaffolds after implantation in living organisms in real-time.

Graphene trapped silk scaffolds integrate high conductivity and stability

Incorporation of highly conducting graphene into electrospun biodegradable polymer mats is very promising for the fabrication of electroactive flexible scaffolds toward neural tissue engineering. However, the direct assembly of graphene onto electrospun polymer fibers for preparing stable conducting scaffolds remains a critical challenge due to the inertness of graphene. To overcome this issue, a one-pot assembly approach was developed to trap graphene inside electrospun mats of regenerated silk fibroin (RSF) by applying its ethanol-treatment driven supercontract. This approach is simple, direct, and controllable, loads only a small amount of graphene, and achieves high conductivity for scaffolds (a minimum resistance of (54.9 ± 20.3) Ω/sq). This ensures weak interference on the softness and biodegradability of graphene trapped RSF scaffolds. Thus, the prepared graphene functionalized RSF scaffold remains highly conductive and stable even with ultrasonic washing. It promotes cell spreading and differentiation, and significantly stimulates the neurite outgrowth by 74.5%, while applying an optimized constant electrical potential, thus indicating it as an ideal candidate as electroactive scaffold for tissue engineering. The application of graphene trapped electrospun polymer mats can be extended to electro-tuned tissue engineering, skin electronics, wearable sensors, and e-textiles due to its combination of flexibility, portability, and electrical conductivity.

A simple semi-quantitative approach studying the in vivo degradation of regenerated silk fibroin scaffolds with different pore sizes

The biocompatibility and in vivo degradation rate of biomaterials represent critical control points in the long-term success of scaffolds for tissue restoration. In this study, new three-dimensional (3D) regenerated silk fibroin scaffolds (RSFs) were prepared by the freezing-defrosting procedure, and then were implanted beneath the dorsal skin of rats. This study aims to develop a kinetic semi-quantitative approach to assess in vivo degradation rate and biocompatibility of this kind of RSFs with different pore sizes for the first time, and to evaluate the relationship between the biodegradation and tissue responses by measuring the thickness of residual scaffolds, fibrous capsules and infiltrated tissues through integrated techniques of histology, optical imaging and image analysis. Our results showed that scaffolds with both pore sizes (74.35±10.84μm and 139.23±44.93μm, respectively) were well tolerated by host animals and pore size was found to be the rate limiting factor to the biodegradation in the subcutaneous implantation model. In addition, the biodegradation of RSFs was inflammation-mediated to a certain degree and fibroblasts may play a critical role in this process. Overall, such semi-quantitative approach was demonstrated to be a simple and effective method to assess the in vivo degradation rate, and the prepared RSFs were presented to have promising potential in tissue engineering applications.

Mesenchymal Stem Cell-Seeded Regenerated Silk Fibroin Complex Matrices for Liver Regeneration in an Animal Model of Acute Liver Failure.

The main limitation of liver transplantation as a treatment for end-stage liver disease or acute liver failure is the scarcity of liver organ donors. To develop an alternative therapy for acute liver failure, mesenchymal stem cell (MSC)-seeded regenerated silk fibroin (RSF) matrices were evaluated in vitro and in vivo. Adipose-derived mesenchymal stem cells (ADSCs) and bone marrow-derived mesenchymal stem cells (BMSCs) were planted and grown on RSF scaffolds to form a scaffold complex. The RSF-MSC scaffold complex (the experimental group) and neat RSF scaffolds (the control group) were then placed onto the liver surface of mice induced by CCl4 and detected after 5, 7, 14, 28, and 60 days. The growth and distribution of MSCs were tracked using fluorescence microscopy and live small animal fluorescence. Liver functions were tested using an automatic biochemistry analyzer. The histological kinetics of RSF complex and liver tissues were observed using hematoxylin & eosin staining. We found that MSCs exhibited good biocompatibility with RSF and differentiated to hepatocyte-like cells in vitro. Liver functions of the mice in the experimental group were significantly improved than that in the control group. Moreover, angiogenesis and hepatocyte-like cells were discovered in the RSF scaffolds in an animal model of acute liver failure on the fifth day and in the second month, respectively. The MSCs-RSF matrices show an obvious therapeutic ability for injured liver function of mice, which is more efficient than the neat RSF scaffolds.

Facile fabrication of the porous three-dimensional regenerated silk fibroin scaffolds

In the present work, we report a new facile method to fabricate porous three-dimensional regenerated silk fibroin (RSF) scaffolds through n-butanol- and freezing-induced conformation transition and phase separation. The effects of RSF concentration, freezing temperature and n-butanol addition on the microstructure, the secondary structures of silk fibroin and apparent mechanical properties of the RSF scaffolds were investigated by SEM, 13C CP-MAS NMR spectra and mechanical testing, respectively. By adjusting the RSF concentration and n-butanol addition, the pore size of the scaffold could be controlled in the range from of 10μm to 350μm with 84%–98% of porosity. The tensile strength of the wet scaffold reached the maximum of 755.2±33.6kPa when the concentration of RSF solution was increased to 15% w/w. Moreover, post-treatment with ethanol further induced conformation transition of RSF from random coil or helix to β-sheet. The porous scaffolds prepared by this facile and energy-saving method with good biocompatibility will have great potential for application in tissue engineering.

Preparation of 3D Fibroin/Chitosan Blend Porous Scaffold for Tissue Engineering Via a Simplified Method

In this work, we developed a simple and flexible method to manufacture a 3D porous scaffold based on the blend of regenerated silk fibroin (RSF) and chitosan (CS). No crosslinker or other toxic reagents were used in this method. The pores of resulted 3D scaffolds were connected with each other, and their sizes could be easily controlled by the concentration of the mixed solution. Compared with pure RSF scaffolds, the water absorptivities of these RSF/CS blend scaffolds with significantly enhanced mechanical properties were greatly increased. The results of MTT and RT-PCR tests indicated that the chondrocytes grew very well in these blend RSF/CS porous scaffolds. This suggested that the RSF/CS blend scaffold prepared by this new method could be a promising candidate for applications in tissue engineering.