Porous Silk Fibroin Films Research Articles

Construction and electrochemical properties determination of carbon nanotubes/porous-network carbon micron tubes/silk fibroin composite film neural electrode

A novel carbon nanotubes/porous-network carbon micron tubes/silk fibroin (CPS) composite film neural electrode was presented and characterized. This electrode was fabricated through assembling dispersed carbon nanotubes (CNTs) by phytic acid onto the porous silk fibroin film. Afterward, the silk fibroin around the CNTs was carbonized by laser irradiation, producing porous-network carbon microtubes with good conductivity and biological compatibility. The structure of the CPS composite film was characterized by scanning electron microscopy and Raman spectroscopy. Cyclic voltammetry, electrochemical impedance spectroscopy, and safe charge injection limit (Qinj) of the CPS electrode were also measured by the three-electrode system, and the results exhibited outstanding electrochemical properties with the achieved Qinj of 5.7 mC/cm2. This work provides a promising approach for the preparation of a long-term implanted neural electrode with high charge injection ability and good biocompatibility.

Observation of co-culturing cells on porous silk fibroin films

Porous silk fibroin films (PSFFs) are widely used in skin regeneration. Prevascularization of PSFFs is a successful strategy for enhancing the survival of engineered tissues in vivo. The adhesion and migration of human umbilical vein endothelial cells (HUVECs) and fibroblasts on PSFFs were observed by scanning electron microscopy and confocal laser scanning microscopy after vital staining of the cells. PSFFs could attract a large number of HUVECs and fibroblasts to pores in an interesting alignment and support them to spread well from the outside of pores to the center of PSFFs to form cell layers. PSFFs showed minor structural changes due to less degradation for 12 d culture, and cell layers overlapped from pores to the center in PSFFs. The total DNA assay indicated excellent cell proliferation on PSFFs on days 1 and 6 and no difference between co-culturing HUVECs and mono-HUVECs and monofibroblasts. PSFFs could guide cell migration and arrangement to form pore-centered and vessel-like structures without additional coating of proteins. The authors’ aim was to study the potential prevascularization of porous silk fibroin scaffolds by co-culturing HUVECs and fibroblasts. This model has potential application for angiogenesis in dermis regeneration in the future and provides a suitable microenvironment for the development of capillary-like structures.

Development Model of Micro vascular Network in Porous Silk Fibroin Film

Development Model of Micro vascular Network in Porous Silk Fibroin Film

Observation of vascularization and protein after implanting porous silk fibroin films in rat.

Porous silk fibroin films can provide an optimal microenvironment for angiogenesis in vivo. Adhesion and migration of human umbilical vein endothelial cells (HUVEC) on porous silk films were observed by confocal laser scanning microscopy. The expression of fibronectin (FN), laminins (LN), intercellular adhesion molecule-l (ICAM-1) and vascular cell adhesion molecule-l (VCAM-1) after implanting Porous Silk Fibroin Films (PSFFs) as grafts for dermis regeneration in rat were studied. FN, LN, ICAM and VCAM may have direct relationships with angiogenesis. The result will help to design excellent PSFFs and study the process and mechanism of angiogenesis.

In vivo biodegradation of porous silk fibroin films implanted beneath the skin and muscle of the rat

Since the bioresorption process has a strong impact not only on the mechanical properties of the biomaterial but also on the extent of tissue regeneration, in vivo biodegradation of absorbable porous biomaterials plays a key role in tissue repair and wound healing. In the present work, porous silk fibroin films (PSFFs) were prepared by a freeze-drying method and then implanted beneath the dorsal skin and the femoral skeletal muscle of the rat. The objective was to study the rate of biodegradation of the PSFFs in different tissues, each with its distinct metabolic rate. In addition we examined the relationship between the biodegradation rate and tissue-regeneration rate semi-quantitatively by incorporating histology, microscopy and image analysis methods. Furthermore, based on our previous findings, we also explored the relationship between in vitro and in vivo rates of biodegradation. The results suggest that the PSFFs experience a similar biodegradation process regardless of the type of tissue in which they are implanted, in spite of the higher metabolic rate of the skeletal muscle. In addition, the in vitro biodegradation rate of the PSFFs was comparable to that of both skin and skeletal muscle, suggesting that an in vitro biodegradation test could be used to predict in vivo performance.

Observations of Skin Tissue Regenerations in Biomaterial Scaffolds with Different Biodegradability

Objective: To explore the effects of the biodegradability of biomaterial scaffolds on skin tissue regeneration and its neovascularization by the animal experiments. Methods: A piece of porous silk fibroin film (SF) of easy biodegradation and a piece of porous polyvinyl alcohol film (PVA) of hard biodegradation were implanted into a same skin wound of adult rat, and the differences in the regenerative blood vessel and tissue at 5, 10, 16, 41 days after surgery were observed by histological methods. Results: (1) at 10 days after surgery, the SF started to degrade, the closed areas without cell infiltration were opened up and the entire material was filled with the regenerative tissue, and there were still the closed areas in the PVA, (2) the new vascular network remodeling in the SF and PVA appeared at 10 days and 41 days after surgery, respectively, and (3) at 16 days after surgery, most of the SF material had degraded and substantially been replaced with the regenerative tissue, and the visible degradation of the PVA appeared at 41 days after surgery. Conclusion: The good biodegradability of the SF was helpful both to all vascularization of the material and to the regenerative blood vessels remodeling, and the regenerative tissue was closer to the normal dermal tissue than in the PVA.

Exploring the Mechanism of Microarteriogenesis in Porous Silk Fibroin Film

Purpose. Based on the experiment of the microarteriogenesis that is associated with angiogenesis during tissue repair process in porous silk fibroin films (PSFFs), we investigate the characteristics of micro-arteriogenesis and explore its mechanism. Methods. After the porous silk fibroin materials are implanted into the back hypodermal tissue of SD rats, the arteriole development and the morphogenesis of smooth muscle cell are histologically monitored and the micro-arteriogenesis is quantitatively analyzed. Results. 10 days after implantation, the arteriole density reaches the highest level in the junction of silk fibroin materials with tissues. Three weeks later, the arteriolar density in the materials reaches the maximum, and the arterioles in the junction of materials with tissues appear to be in a mature and upgrading state. Modeling of Microarteriogenesis. The arterioles in materials are generated after capillary angiogenesis. It is inferred that arteriolar development does not start until the network of the capillaries is formed. At first, the arterioles grow in the conjunct area of precapillaries with arterioles. Then with the extension of the arterioles, the upgrade of arterioles in connecting area is observed at a later stage. Based on the observation, the conditions and the mechanism of microarterializations as well as the upgrade of arterioles are analyzed.

On model of angiogenesis and the mechanism in porous silk fibroin films

The purpose of this paper is to explore the mechanism of the angiogenesis modes in the biomaterials implanted in vivo. By means of experimental observation and analysis of the capillary growing state in the porous silk fibroin film implanted into rats, we intended to develop a modeling expression on the growth mode of the capillaries in the biomaterials. Additionally, we proposed the response model of endothelial cells (ECs) resulting from vascular endothelial growth factor's concentrations at different stages after the implantation. With the implantation experiment, it was identified that angiogenesis developed in the way of capillary sprouting at the early stage of implantation and of intussusception at the late stage. Based on the response model of ECs, experimental results are explained.

Observation of Capillaries after Implanting Porous Silk Fibroin Films in Rats

Porous Silk Fibroin Films(PSFFs) as dermis implant were used widely in biomaterials. To investigate angiogenesis in rat at different time after PSFFs implanting, CD34 was observed. Immunohistochemistry showed new blood vessels were mainly formed by sprouting next to PSFFs after 7 days operation. Microvessel Density (MVD) in PSFFs was 0, 3.54, 11.6, 24.5 after 1day, 7days, 15 days and 25days implantation respectively.

Analysis of neovascularization after implanting porous silk fibroin films in rats

The purpose of this paper is to explore neovascularization in the biomaterials implanted in vivo. Capillaries formation of dermis defect filled with porous silk fibroin films (PSFFs) implant were investigated in rat at different times. Vascular endothelial growth factor (VEGF), CD34 and hypoxia inducible factor-1 (HIF) were observed in inflammatory cells and fibroblast in PSFFs by day 1, but expression in HIF and VEGF decreased by day 7, otherwise VEGF expressed in vascular endothelial cell increased by day 15 and 25, respectively. VEGF, angiopoietin 1 (Ang-1) and integrins αv and integrins β3 in PSFFs were observed by Reverse transcription-polymerase chain reaction (RT-PCR). Polyvinyl alcohol (PVA) sponge was control. PSFFs have better neovascularization than that of PVA expression of VEGF, HIF and angiogenesis in immunohistochemical and mRNA level.

Porous Silk Fibroin Film as a Transparent Carrier for Cultivated Corneal Epithelial Sheets

Biological carriers, such as the amniotic membrane and serum-derived fibrin, are currently used to deliver cultivated corneal epithelial sheets to the ocular surface. Such carriers require being transparent and allowing the diffusion of metabolites in order to maintain a healthy ocular surface. However, safety issues concerning biological agents encouraged the development of safer, biocompatible materials as cell carriers. We examined the application of porous silk fibroin films with high molecular permeability prepared by mixing silk fibroin and poly(ethylene glycol) (PEG), and then removal of PEG from the silk-PEG films. Molecular permeability of porous silk fibroin film is higher than untreated silk fibroin film. Epithelial cells were isolated from rabbit limbal epithelium, and seeded onto silk fibroin coated wells and co-cultured with mitomycin C-treated 3T3 fibroblasts. Stratified epithelial sheets successfully engineered on porous silk fibroin film expressed the cornea-specific cytokeratins K3 and K12, as well as the corneal epithelial marker pax6. Basement membrane components such as type-IV collagen and integrin β1 were expressed in the stratified epithelial sheets. Further more, colony-forming efficiency of dissociated cells was similar to primary corneal epithelial cells showing that progenitor cells were preserved. The biocompatibility of fibroin films was confirmed in rabbit corneas for up to 6 months. Porous silk fibroin film is a highly transparent, biocompatible material that may be useful as a carrier of cultivated epithelial sheets in the regeneration of corneal epithelium.

Characterization of Angiogenesis during Skin Wound Repair by Porous Silk Fibroin Film

Based on our experimental data of neovascularization of porous silk fibroin films (PSFF)，in this study we characterized the formation of new blood vessel system at different periods. Firstly, we regarded a wound as two sections, namely, an interface layer and a material layer. Angiogenesis of the interface layer underwent three periods that were rehabilitation period of primary vascular plexus (postoperative 1st day-3rd day), rapid growth period (postoperative 3rd day - 7th day) and remodeling period (after the 7th day). In addition, angiogenesis of the material layer underwent initiation period (postoperative 5th day - 7th day), rapid growth period (postoperative 7th day - 13th day) and remodeling period (after the 13th day). According to the analysis results for angiogenesis, we realized that the efficacy of PSFF on repairing wound was reflected in coordination between infiltration of cells in the pores and angiogenesis, and in timeliness of the newly formed blood vessels’ extention from the interface layer to the material layer.

Neovascularization of Porous Silk Fibroin Films(PSFFs) as Dermis Substitutes Implanted in Rats

Neovascularization in biomaterials plays a key role in wound healing. In this paper, porous silk fibroin films (PSFFs) whose structure was optimized, as dermis substitutes, were implanted in the back skin of rats for recovery of dermis loss. Results showed that a thin layer of loose connective tissue had formed at the interface between PSFFs and subcutaneous tissues, in which abundant blood vessels could be observed at 24 h after surgery. Whereafter the newly formed connective tissue thickened and the number of microvessels in the tissue increased. Furthermore, a few microvessels could be seen in PSFFs at day 5, most of which were capillaries. By day 10, the density of microvessels in PSFFs increased to a peak while the percentage of capillary decreased. At day 23, both the density of microvessels and the percentage of capillary was almost equal to those of normal tissues. In summary, wound healing with PSFFs as dermis substitutes is the neovascularization process of PSFFs. The process includes three major steps: (1) new formation and growth of loose connective tissue into the pores of PSFFs, (2) proliferation and migration of fibroblasts and endothelial cells, and (3) formation of functional microvessels and their networks.

On the growth morphous of capillaries and tissue in porous silk fibroin films

In this study, the porous silk fibroin film (PSFF) is implanted into the body of a rat. Ten days later, the growing state of the capillaries in the material was observed, and the growing law of the capillaries in porous material is discussed to better understand the growing state of the peripheral tissue and cells around the material. The fact that the PSFF creates a beneficial environment for the growth of the capillaries in the tissue is confirmed, and the good growing states of the new skeleton muscle and the hypodermal tissue are also observed. This provides basic experimental results for the design of the PSFFs, which is a new medical biomaterial.

Research on the Growth Density of the Capillaries and the Configuration of the Porous Silk Fibroin Film

In order to obtain porous silk fibroin films that suit all kinds of different tissue and organs, to design the configuration of the porous silk fibroin films more rationally, this paper made a modeling of the oxygen diffusing system of the capillary, and also solved the model. Moreover the paper gave a method to estimate the density of the capillaries in the tissue; and hereby brought forward the basic requirements in designing the configuration of the porous silk fibroin film.

Density of capillaries and the oxygen diffusion model in the porous silk fibroin film

In order to obtain porous silk fibroin films (PSFFs) fit for the repair of different tissues and organs and design the configuration of the PSFFs more rationally, a model of the oxygen diffusing system of the capillary was built, and also the equations of the model were solved. Moreover, the relationships between the distribution of the oxygen concentration and each affecting factors were discussed, a method was developed to estimate the density of the capillaries in the tissue, and hereby discussed the characteristics of the oxygen diffusion in the tissues around the open capillaries.

On the growth model of the capillaries in the porous silk fibroin films

This paper discussed the random growth model of the capillaries in its growing process, analyzed the relations between the growth of the capillaries, the metabolism of the organism tissue, and micro environmental condition and secretion of the growth factors. Furthermore, the paper discussed the growth law of the capillaries in the porous silk fibroin films (PSFF) in order to provide a theoretical basis for the designing and making of the new biomaterial of the PSFF more suitable for the growth of the cells and capillaries.