Properties Of Silk Fibroin Films Research Articles

Construction and performance study of double-layer periosteal material for repairing bone tissue damage

Microscopic observation is necessary for the treatment of bone tissue microloss. To observe the process of bone tissue maturation is an essential research content in the field of orthopaedics. In many cases, people have to distinguish between new bone and mature bone, sometimes involving software calculation, and conventional HE staining obviously cannot fully meet the requirements. The quality of imaging directly affects the therapeutic effect of medical staff. In order to prove the effect of laser scanning confocal microscope (LSCM) on the observation of bone tissue micro damage, a piece of pig iliac bone and a piece of human femoral head were selected. The two kinds of bone tissue were divided into three small pieces respectively, and then stained with calcein green and alizarin red, or added with 5 ml of 1000 ml/L ethanol, and then placed under the LSCM and fluorescein Scanning under light microscope. This article uses silk fibroin as the raw material to prepare high-strength bilayer membranes using rotary evaporation method. Through relevant performance experiments, the results show that the mechanical properties of the double-layer silk fibroin film are about 12.48 MPa, and the tensile strength at break is about 13.66%. With the addition of hydroxyapatite, the mechanical properties of the silk fibroin film are improved. The addition of VEGF has little effect on the mechanical properties, and the addition of growth factor has little effect on the tensile strength of the material. The double-layer silk fibroin membrane was degraded in protease for 2 weeks, with a mass loss of about 19.3%. There was almost no degradation phenomenon in PBS solution; The release of VEGF from the double-layer silk fibroin membrane was about 17.3% after 2 weeks, with a relatively fast release rate in the early stage, and then the rate slowed down. The total release of VEGF decreased compared to the pure SF/VEGF membrane. Through the analysis of the scanning image, it is found that the image signal-to-noise ratio of alizarin red stained human femoral head is 6.956 higher than that of fluorescence microscope. In terms of image error rate, fluorescence microscope is 4.228 higher than laser scanning confocal microscope. The edge definition of laser scanning confocal microscope was 22.17 higher than that of fluorescence microscope, and the image clarity of stained bone tissue was higher than that of bone tissue only added ethanol. Therefore, the imaging effect of bone tissue staining is better, and the image generated by LSCM is higher than that generated by fluorescence microscope.

Optically Clear Silk Fibroin Films with Tunable Properties for Potential Corneal Tissue Engineering Applications: A Process-Property-Function Relationship Study.

Owing to the shortage of donor corneas and issues associated with conventional corneal transplantation, corneal tissue engineering has emerged as a promising therapeutic alternative. Biocompatibility and other attractive features make silk fibroin a biomaterial of choice for corneal tissue engineering applications. The current study presents three modes of silk fibroin film fabrication by solvent casting with popular solvents, viz. aqueous (aq), formic acid (FA), and hexafluoroisopropanol (HFIP), followed by three standard modes of postfabrication annealing with water vapor, methanol vapor, and steam, and systematic characterization studies including corneal cell culture in vitro. The results indicated that silk fibroin films made from aq, FA, and HFIP solvents had surface roughness (Rq) of 1.39, 0.32, and 0.13, contact angles of 73°, 85°, and 89°, water uptake% of 58, 29, and 27%, swelling ratios of 1.58, 1.3, and 1.28, and water vapor transmission% of 39, 26, and 22%, respectively. The degradation rate was in the order of aq > HF > FA, whereas the tensile strength was in the order of aq < HF < FA. Further, the results of the annealing process indicated notable changes in morpho-topographical, physical, degradation, and tensile properties. However, the films showed no detectable changes in chemical composition and remained optically clear with >90% transmission in the visible range, irrespective of fabrication and postfabrication processing conditions. The films were noncytotoxic against L929 cells and were cytocompatible with rabbit cornea-derived SIRC cells in vitro. The study demonstrated the potential of fine-tuning various properties of silk fibroin films by varying the fabrication and postfabrication processing conditions.

Effect of post-treatment methods and nanoparticles on the conformation of silk fibroin and their impact on electrical properties

ABSTRACT This paper investigates the effect of different plasticizers (glycerol and dextrose), post-treatment methods, and metal oxide nanoparticles, i.e. zinc oxide and copper oxide on the structural properties of silk fibroin films and their effect on electrical properties, i.e. dielectric strength. Structural properties of the silk fibroin films have been evaluated using Fourier transform infrared spectroscopy and X-ray diffraction technique. It was found that plasticizers and post-treatment applied on the regenerated silk fibroin films have impacted the β-sheet conformation significantly. The dielectric strength of the silk fibroin films was measured using the parallel plate capacitor method and an interrelation with structural properties was observed. Nanoparticles have been introduced into the silk fibroin films as a progressive method to impart substantial effect on the dielectric strength of the silk fibroin films. However, an unexpected change in dielectric strength has been obtained. The mechanism behind the change in dielectric strength has been explored in this work.

The post-processing temperature or humidity can importantly control the secondary structure and characteristics of silk fibroin films.

Temperature and humidity (TH) are highly important factors that can control the secondary structure and characterization of silk fibroin (SF) biomaterials. In this study, the water stability, secondary structure, mechanical properties, surface morphology, and degradation of silk fibroin films (SFFs) with post-processing in different TH were investigated. Fourier transform infrared indicated that the SFF secondary structure did not change under low-relative humidity (RH) despite temperatures up to 180°C, while it transformed at 40°C with 100% RH in 10min. A film with a higher tensile strength (42.1 ± 8.2MPa) could be obtained after post-processing at 90°C/100% RH for 10min. While a film with higher ductility (elongation at break: 198.8 ± 31.8%) was generated after post-processing at 40°C/100% RH for 10min. Scanning electron microscope showed that the film presented a network structure of nanoparticles in series under certain TH post-treatment. Enzymatic hydrolysis proved that the SFFs containing a higher content of silk II structure degraded more slowly. Therefore, TH post-treatment is a relatively mild way to change the secondary structure and properties of SFFs, which can be widely used in loading drugs and maintaining the activity of drugs in SF biomaterials.

Получение нерастворимых в воде пленок из фиброина шелка, исследование их структуры и свойств

Silk fibroin is one of the promising natural polymers that already being used in medicine to forming of suture materials. The possibility of forming scaffolds in the form of films, sponges or gels for cell cultivation and transplantation will significantly expand the scope of application of this material in tissue engineering. The conditions for obtaining silk fibroin insoluble in water in the form of films were worked out. The structural transition on the surface of the films to a coarsely fragmented state after treatment of the films with methanol was demonstrated using optical microscopy. Using FTIR spectroscopy, the conformational transition of silk fibroin from the disordered structure of the untreated film to the β-folded structure was confirmed. Using the method of differential scanning calorimetry, the glass transition temperature of the native film was determined as 216 °C. The study of the mechanical properties of silk fibroin films in a liquid medium showed that their strength decreases and their elasticity increases by almost 15 times compared to tests of the same films in a dry state.

Effects of Chemical Post-treatments on Structural and Physicochemical Properties of Silk Fibroin Films Obtained From Silk Fibrous Waste.

Silk fibroin (SF) is a protein polymer claimed to have outstanding potential for medical applications. However, because of the manufacturing process, materials from regenerated SF exhibit a higher percentage of amorphous structures. The amorphous structures cause the material to be water soluble and can significantly limit its applications in wet biological environments. In order to increase the amount of crystalline structures and decrease the water solubility of SF materials, post-treatment with alcohols is usually employed. SF can be obtained from silk fibrous wastes (SFW), usually discarded in silk textile processes. This represents an opportunity to produce materials with high added value from low-cost natural sources. In this study, SF was obtained from SFW, and films were made thereof followed by a post-treatment by immersion or in a saturated atmosphere of methanol (MeOH) or ethanol (EtOH), using different exposure times. The resulting films were analyzed according to crystallinity, the percentage of crystalline and amorphous structures, and thermal stability. Also, water absorption and weight loss in aqueous media were determined. The results showed a significant increase in crystalline structures in all treated samples, varying according to the type and time of exposure to post-treatment conducted. The highest increase was shown in the case of the post-treatment by immersion in MeOH for 1 h, with a 23% increase over the untreated sample. This increase in crystallinity was reflected in an increase in the degradation temperature and a degradation rate of 5.3% on day 7. The possibility of tuning the degree of crystallinity, as well as thermal stability and aqueous integrity of thin films of SFW, can be applied to adjust these materials to the requirements of specific biomedical applications.

Effect of crystallinity on acoustic behaviors of biocompatible silk studied by Brillouin spectroscopy

Temperature dependences of thermal, thermogravimetric, and acoustic properties were investigated for the crystalline silk fibroin films crystallized by methanol exposure. The crystallization peak in the thermal flow at ~ 225 ◦ C, which was prominent in the amorphous silk film, disappeared in the crystalline silk film. The heat-treatment at ~ 100 ◦ C for 1 h reduced the weight by ~5.5% due to the release of water molecules. The formation of beta-sheets in the film did not have any substantial effect on the acoustic properties of the longitudinal acoustic mode in the crystalline film. However, the heat treatment of the methanol-exposed silk film induced clear anomalies in the acoustic mode behaviors in a specific temperature range between −20 ~ 30 ◦ C. The existence of water molecules has more profound effect than the crystallinity does on the acoustic properties of silk fibroin films.

Structural and thermal properties of silk fibroin films obtained from cocoon and waste silk fibers as raw materials

This study compares the structural and thermal properties of silk fibroin (SF) films obtained from different raw materials: silk coccons (SC) and silk fibrous wastes (SW). Samples were processed by solution casting (SFC and SFW), and casting with a subsequent water annealing treatment (WA-SFC and WA-SFW). The presence of crystalline (silk I and silk II) and amorphous structures was evaluated using X-ray diffraction (XRD) and Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy. Thermal properties of SF films were studied by DSC measurements. Accordingly, to FTIR and XRD results, the presence of silk I structure is greater in SFW that in SFC. Differences in enthalpy of crystallization peaks in DSC curves reveals that SFC presents a higher content of amorphous structures than SFW. The analysis also point that water annealing treatment induces conformational changes in secondary structures of SF films. It can be concluded that the presence of crystalline structures in SF films varies with the raw material and water annealing treatment. This fact represents a progress in the development of processing alternatives to control SF materials structure and properties.

Effects of addition of condensed tannin on the structure and properties of silk fibroin film

Effects of addition of condensed tannin on the structure and properties of silk fibroin film

Effect of different fabrication methods on the chemo-physical properties of silk fibroin films and on their interaction with neural cells

In this study, we investigated the influence of processing methods on the chemo-physical properties of silk fibroin (SF) film and on their interaction with neural cells.

The outermost surface properties of silk fibroin films reflect ethanol-treatment conditions used in biomaterial preparation.

Silk fibroin has attracted interest as a biomaterial, given its many excellent properties. Cell attachment to silk substrates is usually weaker than to standard culture dishes, and cells cultured on silk films or hydrogels typically form spheroids and micro-aggregates. However, too little is known about the higher order structures and behavior of fibroin under different conditions to explain the features of silk fibroin as a culture substrate. For instance, different biomaterial surfaces, with distinct effects on cell culture, can be achieved by varying the conditions of crystallization by alcohol immersion. Here, we show that treatment of fibroin film with <80% ethanol results in a jelly-like, hydrated hydrogel as the outermost surface layer; fibroblasts preferably aggregate, rather than attach individually to such a hydrogel surface, and therefore aggregate into spheroids. In contrast, a fibroin film treated with >90% ethanol has a harder surface than the <80% ethanol-treated fibroin, to which individual cells prefer to attach (and then expand on the surface), rather than to aggregate. We discuss the influence of alcohol concentration on the surface properties, based on surface analysis of the films. The surface analysis involved assessment of static and dynamic contact angles, zeta potential, changes in crystallinity and microscopic morphology of electrospun fibers, and texture changes of the outermost surface at a nanometer-scale captured by a scanning probe microscope.

The impact of degumming conditions on the properties of silk films for biomedical applications

The degumming process to remove sericin decreases silk fiber strength; however, the impact of degumming on the mechanical properties of regenerated silk biomaterials has not been established. This study investigated the effect of degumming temperature, time, alkaline component and alkaline concentration on the mechanical properties of silk fibroin films. Sericin removal was estimated using weight loss; 10 samples with 12.2–29.4% weight loss were then further characterized in terms of fiber mechanical properties, fiber surface morphology, molecular weight distribution and film tensile strength. A negative correlation was found between weight loss and fiber tensile strength. This loss of fiber strength under harsher degumming conditions had a direct impact on the tensile strength of regenerated films. Mild degumming conditions (weight loss of 12.2%) led to higher film strength (8.9 MPa), whereas aggressive degumming conditions (with 29.4% weight loss) resulted in significantly weaker films (4.3 MPa). The presence of some residual sericin, after mild degumming, is likely to affect the mechanical properties of the regenerated silk films. These results will assist in the development of materials with mechanical and biocompatibility properties tuned to specific biomedical applications.

Preparation and Mechanical and Optical Properties of SF/Pyrrolidone Blend Film

To improve the properties of silk fibroin film, the silk fibroin/pyrrolidone blend films were prepared by mixing silk fibroin and pyrrolidone solution at different ratios. The structure and mechanical properties of blend films were characterized. X-ray diffraction was used to investigate structure of the SF/PYR films, and the results indicated that the blend films were composed of the β-sheet form. Tensile strength and elongation at break of blend films were measured using an instron tensile tester. The results showed that tensile strength and elongation at break of blend films were high enough for application. Furthermore, the films’ flexibility was significantly improved. The optical clarity of blend film was tested by Microplate system. It can be seen from the results that optical clarity is not stable, but in some particular ratios we also can get high light transmittance blend films. At last, biocompatibility of blend films (the rate of the blend film is 30%) was accessed with L929 cell. The results showed that all types of blend films were able to support cell adhesion and proliferation. In addition, the cellular morphology of the cells cultured on blend films was better than that on silk fibroin films. In view of the mechanical properties and optical clarity, combined with their ability to support L929 proliferation suggests that this blend films will offer new options in many different biomedical applications.

The Progress in Research on Silk Fibroin Blend Membranes

Silk fibroin film, which has good biological compatibility, is suitable for use as biomaterials and medical materials. However, silk fibroin film in dry state is too brittle to be used by itself. Blending with other natural or synthetic polymers could improve the poor mechanical properties of silk fibroin film. In this paper, recent researches in blend film of silk fibroin and their application were summarized.

Enzymatic Degradation Properties of Silk Fibroin Film

Enzymatic Degradation Properties of Silk Fibroin Film

Evaluation of the Properties of Silk Fibroin Films from the Non-mulberry Silkworm Samia cynthia ricini for Biomaterial Design

Silk fibroin from a domesticated mulberry silkworm, Bombyx mori, is the most widely used in biomaterial design. We report for the first time the preparation of a relatively smooth (granule free) film of the nonmulberry Samia cynthia ricini fibroin for comparative evaluation of its cell-supporting properties against those of the B. mori fibroin film. The granule formation on the S. c. ricini fibroin film was successfully prevented by facilitating proper rearrangement of the protein molecules, as monitored by FT-IR, by dialysis through a stepwise decrease in the urea concentration in the dialysis media. The lower contact angle of the S. c. ricini fibroin film, compared to the B. mori fibroin film, corresponds well to its lower hydrophobic/hydrophilic amino-acid ratio and grand average of hydropathicity (GRAVY). L929 murine fibroblast cells on the granule-free S. c. ricini fibroin films exhibited greater proliferation and spreading rates than those on the B. mori fibroin films, possibly attributable to its higher content of hydrophilic and positively charged amino acids. It further suggests that fabrication, modification and/or engineering of S. c. ricini fibroin may provide a better biomaterial scaffold design than the more commonly used B. mori fibroin.

Effect of Different Organic Solvents and Treatment Times on Secondary Structure and Thermal Properties of Silk Fibroin Films

Effect of Different Organic Solvents and Treatment Times on Secondary Structure and Thermal Properties of Silk Fibroin Films

PEG(polyethylene glycol) 농도와 PEG/Gly(glycerol) 흔합비에 따른 견 피브로인 필름의 물성

To study the effects of plasticizer concentration and its ratio on the physical properties of silk fibroin films, polyethylene glycol (PEG) was used at 4 different concentrations; 1, 2, 3, (w/v). Tensile strength (TS) and water vapor permeability (WVP) increased with the increase of PEG concentration, while opposite trend was observed for percent elongation of silk fibroin films. WVP of silk fibroin films increased from for of PEG to for . In addition, a mixture of PEG and glycerol (Gly) as a plasticizer was used at the ratio of 100:0, 75:25, 50:50, 25:75, and 0:100 (w/w). Percent elongation of the films was improved to when the ratio of 75:25 was used. On the contrary, WVP of silk fibroin films increased with the decrease of the ratio of PEG:Gly. Effect of the plasticizer concentration and its ratio on the color of silk fibroin films was negligible. These results suggest that mixture of PEG and Gly as a plasticizer provide more flexible than PEG alone in silk fibroin films, and the best ratio of PEG to Gly was 75:25.

Surface Properties of Silk Fibroin Films and Their Interaction with Fibroblasts

There is a growing interest in the use of silk as a biomaterial for tissue engineering. Silk threads from Bombyx mori have a fibrous core of fibroin, the protein responsible for biocompatibility and bioactivity, which is surrounded by a family of "gummy" proteins, called sericins, which are almost completely removed during silk degumming. Three different methanol treatments on regenerated fibroin films were used to convert viscous solutions of Silk I to an insoluble crystalline form (Silk II), in an attempt to devise new processing protocols for the creation of a cell guiding fibroin surface. Human fibroblasts (MRC5 line) were used as probes of the cell-biomaterial interaction in the early stages of the process (1 h, 3 h, 6 h and 4 d after seeding). The effect of each treatment on cell adhesion, spreading and distribution was monitored by scanning electron microscopy (SEM) and was correlated to superficial properties (like roughness and crystallinity) and fibroin conformation by means of atomic force microscopy (AFM), used in both topographical and acoustic mode, and attenuated total internal reflection infrared spectroscopy (FTIR-ATR). It was found that traditional methanol treatments where fibroin films were soaked in methanol solution produced roughness patterns that affected only the very early stages of fibroblast adhesion (until 3 h from seeding), while the new treatment proposed could really dialogue with the cells. Its non-homogeneous surface can explain the existence of cells spreading in specific directions and the presence of cell repellent areas even 4 d after seeding.

Physical Properties of Silk Fibroin Films Treated with Various Plasticizers

Silk fibroin (SF) films were prepared using various plasticizers and their physical properties were determined. Polyethylene glycol (PEG)-SF and polypropylene glycol (PPG)-SF films had tensile strengths (TS) of 23.71 MPa and 24.51 MPa, respectively, whereas the glycerol (G)-SF film had the lowest TS of 14.24 MPa. G-SF film had the highest % elongation, compared to PPG-SF and PEG-SF films. Water vapor permeability (WVP) of SF films varied with addition of plasticizers, and PEG-SF film had the lowest WVP. There was no significant difference in Hunter L value among treatments, but PEG-SF film had higher Hunter a and b values. These results suggest that SF film could be applied to food packaging and that the addition of plasticizers should improve the physical properties of SF film.