Controlling molecular conformation of regenerated wild silk fibroin by aqueous ethanol treatment

Preparation of fibre-reinforced PLA-collagen@PLA-PCL@PCL-gelatin three-layer vascular graft by EDC/NHS cross-linking and its performance study

In this study, a three-layer small diameter artificial vascular graft with a structure similar to that of natural blood vessels was first constructed by triple-step electrospinning technology, in which polylactic acid (PLA) and collagen (COL) were used for the inner layer, polylactic acid and polycaprolactone (PCL) was used for the middle layer and polycaprolactone and gelatin was used for the outer layer. The properties of the artificial vascular graft were adjusted by the EDC/NHS cross-linking agent through the reaction between the collagen or gelatine and EDC/NHS. The mechanical and hydrophilic properties of the cross-linked artificial vessels were substantially enhanced, with a maximum stress of 9.56 MPa in the axial direction and 9.31 MPa in the radial direction for the P/C (4:1) vascular graft, which exceeded that of many textile-based and natural vascular grafts. The increased hydrophilicity of the inner layer of the vessel before crosslinking was due to the addition of COL, and the inner layer of the artificial vessel after crosslinking had a substantial increase in hydrophilicity due to the production of a more hydrophilic urea derivative. The increased hydrophilicity led to easier cell adhesion to the inner layer of the artificial vessel, especially for the P/C (2:1) vascular graft, where the cell proliferation rate and adhesion were high due to COL incorporation and cross-linking. The three-layer vascular grafts studied did not lead to haemolysis. Therefore, the EDC/NHS cross-linked three-layer vascular graft had good mechanical properties, hydrophilicity, anticoagulation and could enhance cell adhesion and proliferation.

Wound Dressing Based on Cassava Silk-Chitosan

The application prospects of composite sponges with antibacterial and drug-carrying functions in the field of medical tissue engineering are extensive. A solution of cassava silk fibroin (CSF) was prepared with Ca(NO3)2 as a solvent, which was then combined with chitosan (CS) to create a sponge-porous material by freeze-drying. The CSF-CS composite sponge with a mesh structure was successfully fabricated through hydrogen bonding. Scanning electron microscopy (SEM), Fourier transform infrared absorption (FTIR) and X-ray diffraction (XRD) were employed to investigate the appearance and structure of the cassava silk's fibroin materials, specifically examining the impact of different mass percentages of CS on the sponge's structure. The swelling rate and mechanical properties of the CSF-CS sponge were analyzed, along with its antibacterial properties. Furthermore, by incorporating ibuprofen as a model drug into these loaded sponges, their potential efficacy as efficient drug delivery systems was demonstrated. The results indicate that the CSF-CS sponge possesses a three-dimensional porous structure with over 70% porosity and an expansion rate exceeding 400% while also exhibiting good resistance against pressure. Moreover, it exhibits excellent drug-carrying ability and exerts significant bacteriostatic effects on Escherichia coli. Overall, these findings support considering the CSF-CS composite sponge as a viable candidate for use in drug delivery systems or wound dressings.

A multifunctional composite nanoparticle with antibacterial activities, anti-inflammatory, and angiogenesis for diabetic wound healing

The treatment of chronic diabetic wounds remains challenging due to the rapid bacterial infection, severe inflammation, and insufficient angiogenesis. To address these challenges, a novel multifunctional composite nanoparticle is developed by co-assembling antisolvent-induced co-assembling silk-fibroin ε-poly-l-Lysine nanoparticles (nSF-EPL) and further assembling nSF-EPL with polydeoxyribonucleotide (PDRN) and exosome derived from human umbilical mesenchymal stem cells (Exo). Owing to the modification of EPL, PDRN and Exo, composite nanoparticles exhibited synergistic antibacterial action, anti-inflammatory and angiogenesis, which can significantly benefit for promoting wound healing. Release results show that the composite nanoparticles exhibit long-term sustained PDRN and Exo release profiles as well as outstanding release efficiency. Furthermore, in vitro studies show that the composite nanoparticles exhibit effective antibacterial activity, thus inducing an anti-inflammatory M2 macrophages phenotype and promoting angiogenesis. In vivo research results of investigations pertaining to diabetic wound healing show that the composite nanoparticles have good anti-inflammatory and angiogenesis capabilities, which can promote granulation tissue formation, collagen deposition, wound tissue epithelialization, and significantly accelerate skin healing. This study presents a promising strategy for the clinical treatment of chronic diabetic wounds.

Controlled Release of H2S from Biomimetic Silk Fibroin-PLGA Multilayer Electrospun Scaffolds

The possibility of incorporating H₂S slow-release donors inside biomimetic scaffolds can pave the way to new approaches in the field of tissue regeneration and anti-inflammatory treatment. In the present work, GYY4137, an easy-to-handle commercially available Lawesson's reagent derivative, has been successfully incorporated inside biomimetic silk fibroin-based electrospun scaffolds. Due to the instability of GYY4137 in the solvent needed to prepare silk fibroin solutions (formic acid), the electrospinning of the donor together with the silk fibroin turned out to be impossible. Therefore, a multilayer structure was realized, consisting of a PLGA mat containing GYY4137 sandwiched between two silk fibroin nanofibrous layers. Before their use in the multilayer scaffold, the silk fibroin mats were treated in ethanol to induce crystalline phase formation, which conferred water-resistance and biomimetic properties. The morphological, thermal, and chemical properties of the obtained scaffolds were thoroughly characterized by SEM, TGA, DSC, FTIR, and WAXD. Multilayer devices showing two different concentrations of the H₂S donor, i.e., 2 and 5% w/w with respect to the weight of PLGA, were analyzed to study their H₂S release and biological properties, and the results were compared with those of the sample not containing GYY4137. The H₂S release analysis was carried out according to an "ad-hoc" designed procedure based on a validated high-performance liquid chromatography method. The proposed analytical approach demonstrated the slow-release kinetics of H₂S from the multilayer scaffolds and its tunability by acting on the donor's concentration inside the PLGA nanofibers. Finally, the devices were tested in biological assays using bone marrow-derived mesenchymal stromal cells showing the capacity to support cell spreading throughout the scaffold and prevent cytotoxicity effects in serum starvation conditions. The resulting devices can be exploited for applications in the tissue engineering field since they combine the advantages of controlled H₂S release kinetics and the biomimetic properties of silk fibroin nanofibers.

Methods to Characterize Electrospun Scaffold Morphology: A Critical Review

Electrospun scaffolds can imitate the hierarchical structures present in the extracellular matrix, representing one of the main concerns of modern tissue engineering. They are characterized in order to evaluate their capability to support cells or to provide guidelines for reproducibility. The issues with widely used methods for morphological characterization are discussed in order to provide insight into a desirable methodology for electrospun scaffold characterization. Reported methods include imaging and physical measurements. Characterization methods harbor inherent limitations and benefits, and these are discussed and presented in a comprehensive selection matrix to provide researchers with the adequate tools and insights required to characterize their electrospun scaffolds. It is shown that imaging methods present the most benefits, with drawbacks being limited to required costs and expertise. By making use of more appropriate characterization, researchers will avoid measurements that do not represent their scaffolds and perhaps might discover that they can extract more characteristics from their scaffold at no further cost.

Study on the Effect of Stretching on the Strength of Natural Silk Based on Different Feeding Methods

Silk is an important biological protein fiber, which has been widely developed and used in textile and biomedical fields due to its excellent mechanical properties and good biocompatibility. Strength is an important indicator that determines the value and use of silk. Although investigations have been made on the mechanical properties of silkworm silks and their dependence relationship with the microstructures, the variation of silk strength formed in the process of silkworm spinning has not been reported. By feeding the same strain of silkworms with mulberry leaves, mulberry leaves + artificial feed, and artificial feed, silks with three filament sizes were obtained, respectively. The tensile test results showed that the strength and filament size of silk are inversely proportional. The structure and fibrosis process of different-strength silks were analyzed. The results showed that, compared with ordinary silk, the β-sheet and crystallinity content of high-strength silk is higher, indicating that its fibrosis process is more sufficient. We proposed that the stretched degree of silk protein determines its structure and properties. During the spinning process of individual silkworms, the secretion of silk protein is not stable, which will cause changes in the stretched degree. The measurement results of the intraindividual stretched degree and strength verified that the degree of stretch determines the strength of the silk. This study not only provides a deeper understanding of the properties of silk protein but also is of interest for the design and development of advanced biomimetic silk materials.

Silk fibroin directs the formation of monetite nanocrystals and their assembly into hierarchical composites

Natural biominerals are usually composite materials produced through mineralization of inorganic crystals within an organic matrix. Silk fibroin is known to be capable of directing the nucleation and growth of hydroxyapatite crystals. Here, we used silk films as the substrate to induce the mineralization of calcium phosphate. We show that the silk fibroin in solution could induce the formation of monetite crystals with a hierarchical structure, which are assembled by well aligned single crystals of monetite. In addition, we show that silk fibroins are incorporated inside the crystals. Therefore, the self-assembly of silk fibroin during the crystallization process is critical for the formation of such hierarchical structures.

A Comparative Study on the Dissolution of Argema mimosae Silk Fibroin and Fabrication of Films and Nanofibers

Limited studies have been done on silk fibroins of wild silkworm species owing to their relative insolubility in many solvents. In this study, the solubility of Argema mimosae wild silk fibroin in different salts (LiBr, LiCl, Ca(NO₃)₂, and CaCl₂) dissolved in formic acid under varying temperatures was investigated. The dissolution conditions under which the solubility was optimum were optimized using a central composite design approach. The optimum range for solvation of the fibroin were visualized using contour plots. The influence of temperature and salt concentration were found to significantly influence the solvation of the fibroin. Following the successful dissolution of the fibroin, the regenerated silk fibroin solutions were cast to obtain water insoluble films which were used in investigating optimum electrospinning conditions. Average nanofiber diameters in the 110–141 nm range were obtained under optimum electrospinning conditions. The silk forms were characterized using the FTIR, TGA, XRD, and SEM to understand their properties. The investigations revealed that formic acid—salt solvents were effective in the solvation of the wild silk fibroin. Some of the dissolution conditions induced mild effects on the silk fibroin while others were harsh. Furthermore, processing to nanofibers resulted in the degradation of the β-sheets producing nanofibers rich in α-helices. However, post-treatment using methanol and water vapor were effective in restoring β-sheet crystallinity.

Nanoporous silk films with capillary action and size-exclusion capacity for sensitive glucose determination in whole blood

In optical biosensing, silk fibroin (SF) appears as a promising alternative where other materials, such as paper, find limitations. Besides its excellent optical properties and unmet capacity to stabilize biomacromolecules, SF in test strips exhibits additional functions, i.e. capillary pumping activity of 1.5 mm s^-1, capacity to filter blood cells thanks to its small, but tuneable, porosity and enhanced biosensing sensitivity. The bulk functionalization of SF with the enzymes glucose oxidase and peroxidase and the mediator ABTS produces colourless and transparent SF films that respond to blood glucose increasing 2.5 times the sensitivity of conventional ABTS-based assays. This enhanced sensitivity results from the formation of SF-ABTS complexes, where SF becomes part of the bioassay. Additionally, SF films triple the durability of most stable cellulose-based sensors. Although demonstrated for glucose, SF microfluidic test strips may incorporate other optical bioassays, e.g. immunoassays, with the aim of transferring them from central laboratories to the place of patient's care.

Processing Strategies to Obtain Highly Porous Silk Fibroin Structures with Tailored Microstructure and Molecular Characteristics and Their Applicability in Water Remediation

The present work reports on the control of silk fibroin (SF) porous structures performance through various processing methods. The study includes the analysis of two dissolving techniques (CaCl₂/H₂O/EtOH ternary and LiBr/H₂O binary solutions), three regeneration methods (gelation, lyophilization and gas foaming) and one post-processing (EtOH). In all the cases, followed steps lead to SF structures with porosity values above 94% and large surface areas. Also, results about samples microstructure, secondary organization, crystallinity and water behavior, reveal a direct correlation between processing and SF properties. Thanks to the achieved progress, the SF varying porous structures were evaluated for metalloids (As⁵⁺ and As³⁺) and heavy metals (Cr⁶⁺ and Cr³⁺) adsorption, observing a direct relationship between samples processing and ionic species adsorption ability. Thus, it is shown that the control of the properties of SF based porous structures through processing, represents a suitable and ecofriendly approach for the development of bio-based materials for environmental applications.

Ultrafine and High-Strength Silk Fibers Secreted by Bimolter Silkworms

Ultrafine fibers are widely employed because of their lightness, softness, and warmth retention. Although silkworm silk is one of the most applied natural silks, it is coarse and difficult to transform into ultrafine fibers. Thus, to obtain ultrafine high-performance silk fibers, we employed anti-juvenile hormones in this study to induce bimolter silkworms. We found that the bimolter cocoons were composed of densely packed thin fibers and small apertures, wherein the silk diameter was 54.9% less than that of trimolter silk. Further analysis revealed that the bimolter silk was cleaner and lighter than the control silk. In addition, it was stronger (739 MPa versus 497 MPa) and more stiffness (i.e., a higher Young's modulus) than the trimolter silk. FTIR and X-ray diffraction results revealed that the excellent mechanical properties of bimolter silk can be attributed to the higher β-sheet content and crystallinity. Chitin staining of the anterior silk gland suggested that the lumen is narrower in bimolters, which may lead to the formation of greater numbers of β-sheet structures in the silk. Therefore, this study reveals the relationship between the structures and mechanical properties of bimolter silk and provides a valuable reference for producing high-strength and ultrafine silk fibers.

H. Mohammed A, Akioka S, Ngo Trinh T. Fabrication of Silk Resin with High Bending Properties by Hot-Pressing and Subsequent Hot-Rolling

This research reports the processability and mechanical properties of silk resins prepared by hot-pressing followed by hot-rolling and then analyzes their thermal and structural properties. The results show that regenerated silk (RS) resins are better suited for hot-rolling than Eri and Bombyx mori silk resins (untreated silk). When hot-rolling at 160 °C with a 50% of reduction ratio, maximum bending strength and Young’s modulus of RS resin reaches 192 MPa and 10.2 GPa, respectively, after pretreatment by immersion in 40 vol% ethanol, and 229 MPa and 12.5 GPa, respectively, after pretreatment by immersion in boiling water. Increased strength of the material is attributed to the increased content of aggregated strands and intramolecular linking of β sheets (attenuated total reflectance Fourier-transform infrared spectroscopy) and higher crystallinity (X-ray diffraction analysis). After hot-pressing and hot-rolling, RS resins have a stable decomposition temperature (297 °C).

Silk Fibroin as a Coating Polymer for Sirolimus-Eluting Magnesium Alloy Stents

Magnesium (Mg) alloy-based, bioresorbable scaffolding is a promising candidate for next-generation stents. Rapid corrosion of Mg alloy in the physiological environment, however, hinders its clinical application. Hydrofluoric acid (HF) treatment and biodegradable polymer coating have been widely reported to enhance corrosion resistance of the Mg alloy. Poor biocompatibility of biodegradable polymers, however, is known to promote adverse events such as intimal hyperplasia and thrombosis. We selected silk fibroin (SF) as the polymer for stent coating and evaluated drug release from the SF layer, corrosion resistance of the Mg alloy, and biocompatibility. After the stent was coated with SF, ethanol treatment of the SF layer enriched the β-sheet content. Release of sirolimus (SRL), a drug that prevents intimal hyperplasia, from the SF layer was slower than that with a poly(ε-caprolactone), the conventional biodegradable polymer used on medical devices. Ethanol treatment of the SF-coated stent further slowed SRL release from the SF layer. Crystalline domains in SF formed by the β-sheet structure could contribute to the slow release of SRL. The SF coating suppressed local and deep corrosion of the Mg alloy stent, although total corrosion remained unaffected. Uniform corrosion without local or deep corrosion prolongs the stent's radial strength. The SF coating showed excellent biocompatibility with human umbilical vein endothelial cells and minimal platelet adhesion. SF is expected to replace traditional biodegradable polymers for use on bioresorbable stents.

Formic Acid Regenerated Mori, Tussah, Eri, Thai, and Muga Silk Materials: Mechanism of Self-Assembly

Flexible and water-insoluble regenerated silk materials have caught considerable interest due to their mechanical properties and numerous potential applications in medical fields. In this study, regenerated Mori (China), Thai, Eri, Muga, and Tussah silk films were prepared by a formic acid-calcium chloride (FA) method, and their structures, morphologies, and other physical properties were comparatively studied through Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray scattering (WAXS), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). FTIR results demonstrated that the secondary structures of those five types of silk films are different from those of their respective natural silk fibers, whose structures are dominated by stacked rigid intermolecular β-sheet crystals. Instead, intramolecular β-sheet structures were found to dominate these silk films made by FA method, as confirmed by WAXS. We propose that silk I-like structures with intramolecular β-sheets lead to water insolubility and mechanical flexibility. This comparative study offers a new pathway to understanding the tunable properties of silk-based biomaterials.

Structural and Mechanical Properties of Silk from Different Instars of Bombyx mori

Silkworm silk has excellent mechanical properties, biocompatibility, and promising applications in the biomedical sector. Silkworms spin silk at the beginning and end of each of their five instar stages, as well as spinning mature silk after the fifth instar. We evaluated the mechanical properties and structure of 10 kinds of silk fibers from different stages. A tensile test showed that instar beginning silk, instar end silk, and mature silk possess distinct properties. Attenuated total reflectance Fourier-transform infrared spectroscopy and X-ray diffraction results showed that the excellent mechanical properties of instar end silk are attributed to higher β-sheet content and suitable crystallinity. Liquid chromatography-tandem mass spectrometry showed that P25 protein content in IV-E silk is 2.9× higher than that of cocoon silk. This study can offer guidelines for further biomimetic investigations into the design and manufacture of artificial silk protein fibers with novel function.

Multilateral characterization of recombinant spider silk in thermal degradation

Elucidating the complex mechanism of thermo-oxidative degradation of recombinant spider silk by systematic characterization and correlation coefficient approach.

Characterization of Bombyx mori and Antheraea pernyi silk fibroins and their blends as potential biomaterials

Fibroin proteins isolated from the cocoons of certain silk-producing insects have been widely investigated as biomaterials for tissue engineering applications. In this study, fibroins were isolated from cocoons of domesticated Bombyx mori (BM) and wild Antheraea pernyi (AP) silkworms following a degumming process. The object of this study was to obtain an assessment on certain properties of these fibroins in order that a concept might be had regarding the feasibility of using their blends as biomaterials. Membranes, 10–20 μm thick, which are water-insoluble, flexible and transparent, were prepared from pure fibroins and from their blends, and subjected to water vapor annealing in vacuum, with the aim of providing materials sufficiently strong for manipulation. The resulting materials were characterized by electrophoretic analysis and infrared spectrometry. The tensile properties of the membranes were measured and correlated with the results of infrared analysis. At low concentrations of any of the two fibroins, the mechanical characteristics of the membranes appeared to be adequate for surgical manipulation, as the modulus and strength surpassed those of BM silk fibroin alone. It was noticed that high concentrations of AP silk fibroin led to a significant reduction in the elasticity of membranes.

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.

Self-assembly of monolayered lipid membranes for surface-coating of a nanoconfined Bombyx mori silk fibroin film

A self-assembled lipid membrane provides a smooth, hydrophilic and biocompatible surface coating film for materials.

Understanding the variability of properties in Antheraea pernyi silk fibres

Variability is a common feature of natural silk fibres, caused by a range of natural processing conditions. Better understanding of variability will not only be favourable for explaining the enviable mechanical properties of animal silks but will provide valuable information for the design of advanced artificial and biomimetic silk-like materials. In this work, we have investigated the origin of variability in forcibly reeled Antheraea pernyi silks from different individuals using dynamic mechanical thermal analysis (DMTA) combined with the effect of polar solvent penetration. Quasi-static tensile curves in different media have been tested to show the considerable variability of tensile properties between samples from different silkworms. The DMTA profiles (as a function of temperature or humidity) through the glass transition region of different silks as well as dynamic mechanical properties after high temperature and water annealing are analysed in detail to identify the origin of silk variability in terms of molecular structures and interactions, which indicate that different hydrogen bonded structures exist in the amorphous regions and they are notably different for silks from different individuals. Solubility parameter effects of solvents are quantitatively correlated with the different glass transitions values. Furthermore, the overall ordered fraction is shown to be a key parameter to quantify the variability in the different silk fibres, which is consistent with DMTA and FTIR observations.

Insight into the structure of single Antheraea pernyi silkworm fibers using synchrotron FTIR microspectroscopy

Synchrotron FTIR (S-FTIR) microspectroscopy was used to monitor both protein secondary structures (conformations) and their orientations in single cocoon silk fibers of the Chinese Tussah silk moth ( Antheraea pernyi ). In addition, to understand further the relationship between structure and properties of single silk fibers, we studied the changes of orientation and content of different secondary structures in single A. pernyi silk fibers when subjected to different strains. The results showed that the content and orientation of β-sheet was almost unchanged for strains from 0 to 0.3. However, the orientation of α-helix and random coil improved progressively with increasing strain, with a parallel decrease in α-helix content and an increase in random coil. This clearly indicates that most of the deformation upon stretching of the single fiber is due to the change of orientation in the amorphous regions coupled with a conversion of some of the α-helix to random coil. These observations provide an explanation for the supercontraction behavior of certain animal silks and are likely to facilitate understanding and optimization of postdrawing used in the conjunction with the wet-spinning of silk fibers from regenerated silk solutions. Thus, our work demonstrates the power of S-FTIR microspectroscopy for studying biopolymers.

Preparation of Silk Fibroin Microspheres

TheBombyx morisilk fibroin microspheres with controllable size were prepared by electrostatic spraying and freeze-drying method. The effects of solution concentration, voltage and flow rate on the sphere size were discussed. The morphology of microspheres was observed by scanning electron microscopy (SEM). The influence of ethanol treatment on the molecular conformation of silk fibroin microspheres was investigated by XRD and FT-IR spectra. The results indicated that the silk fibroin microspheres with diameter in range of 117-363 μm were spherical in shape, and there were plenty of pores both on the surface and in the interior of the microspheres. The sphere size increased with the rising of silk fibroin solution concentration and flow rate, while decreased as the voltage enhanced. The conformation of silk fibroin microspheres changed from random coil to silk II structure after ethanol treatment.

Effects of Gamma Irradiation on the Structure and Mechanical Properties of Wild Silkworms and Bombyx Mori Silk Fibroin Films

The structure and mechanical properties of A. yamamai, A. perny and B. mori silk fibroin films irradiated by gamma ray with various doses of 0, 25, 50, 100 and 200 kGy, respectively were determined by XRD, FT-IR, DSC and Instron 3365 equipment. Results showed that the aggregation structure and molecular conformation of A. yamamai, A. perny and B. mori silk fibroin films irradiated by gamma ray with those doses mentioned above were not significantly changed. However, with the increase of radiation intensity, the thermal stability of silk fibroin films declined slightly, and the breaking strength and extensibility reduced significantly, due to the breakdown of parts of secondary bonds and covalent bonds. These results suggested that, when these silk fibroin materials were sterilized by gamma irradiation, smaller radiation doses should be used, otherwise irreversible damages on these materials would be caused.

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.

EDC-Crosslinked Electrospun Silk-Fibroin Fiber Mats

Electrospun Silk-Fibroin (SF) mats were fabricated by electrospinning with regenerated Bombyx mori silk-fibroin/formic acid solutions. After spinning, the water soluble and mechanical properties of pure fibroin nanofibers were poor. So electrospun SF mats were crosslinked with N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC), a low cell cytotoxicity crosslinking agent, and N-hydroxysuccinimide (NHS), which can increase the reaction rate. The scanning electron microscope images indicated that the diameter of fibers increased with crosslinking reaction. When EDC/NHS reached to 7.5wt.%, the diameter of fibers achieved the maximum. The mechanical test showed that tensile strength enhanced after crosslinking with EDC/ NHS. While EDC/NHS reached to 7.5wt %, the rupture strength reached to (38.31±5.30) Mpa, and the breaking elongation ratio reached to (182.00±31.27) %. FTIR results showed the the proportion of β-sheet increased while random coil and α-helix decreased after treatment.