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Fluorescent silk fibroin (SF) fibers have great potential in biomedical application and special functions for marking and tracking. How to fabricate fluorescent SF fibers with good fluorescence stability by a simple and environmentally-friendly method has yet to be explored. Here we successfully produced fluorescent SF fibers by using silkworms as bioreactors to introduce rare-earth upconverting phosphors (UCPs) into silk fibroin. The modified silk exhibited bright green colors under 980 nm laser. Additionally, intrinsically fluorescent silk with reinforced mechanical properties were also fabricated via feeding silkworms with carbon nanodots (CNDs). The addition of CNDs hindered the conformation transformation, confined crystallization, and induced orientation of mesophase, resulting in reinforced silk fibers with breaking strength of 521.9 ± 82.7 MPa and breaking elongation of 19.2 ± 4.3%, 55.1% and 53.6% improvement in comparison to that of normal silk, respectively. The CNDs reinforced silk intrinsically exhibited blue fluorescence under 405 nm laser and good biocompatibility. This directly feeding method to produce fluorescent and reinforced SF fibers is green and environmentally friendly, and easy to use for mass production. Moreover, it provides an idea that SF fibers can be cooperated with more fluorescent materials which could exhibit different colors with certain wavelength of light for bioimaging and other applications. [ABSTRACT FROM AUTHOR]

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 grapheme-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 grapheme-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. KEYWORDS: silk fibroin; graphene; electroactive flexible scaffold; [ABSTRACT FROM AUTHOR]

As the perfect combination of strength and luster, silkworm silks have been widely used in many fields. Numerous researches have been conducted to improve its properties for years. This paper demonstrates an in vivo uptake of titanium dioxide (TiO2) nanoparticles by the silkworms, leading to the direct production of intrinsically modified silk. The method easily incorporated the nanoparticles into the inner structure of silks. Results suggest that both the strength and the anti-UV ability of the modified silks were well improved at a low additive amount. [ABSTRACT FROM AUTHOR]

Silk fibroin heavy chain is made up of hydrophilic and hydrophobic segments. During the dry-spinning process of silk fibroin aqueous solution, the interactions between the hydrophilic segments and water diminished gradually while those among the hydrophobic segments were improved for the silk fibroin assembly. However, the effect of water removal and Ca2+ concentration was not well understood. In this paper, we constructed a dry-spinning apparatus mimicking the spinning duct of Bombyx mori to investigate how relative humidity and Ca2+ concentration affect RSF assembly. The results of FTIR, WAXD and tensile test suggest that low relative humidity and higher Ca2+ concentration promote RSF assembly. [ABSTRACT FROM AUTHOR]

Time-resolved synchrotron radiation small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) measurements were performed to study structure evolution of poly(ethylene terephthalate) (PET) industrial yarns during tensile deformation at 125 ºC. We found that both crystalline and amorphous phase were involved during the tensile process. WAXD data indicated that the crystallinity of the PET yarns decreased with increasing strain up to the fracture. The estimated crystallite size associated with the (010) reflection remained unchanged at strains under 15% and decreased quickly at strains from 15% to 32% (breaking point). The crystallite size associated with (-110) reflection decreased, while the crystallite size of (100) reflection nearly remained unchanged during the whole tensile process. SAXS data showed that the long period, crystalline and amorphous thickness increased with the increasing strain during tensile deformation. The enlargement of long period indicated that the lamellar structures of the yarns became loosely packed during the tensile deformation. [ABSTRACT FROM AUTHOR]

Tissue engineering aims at developing functional substitutes for damaged or diseased tissues and organs. Electrospinning has emerged to be a simple and effective technique to fabricate tissue engineering scaffolds, which were widely used in tissue engineering. Silk fibroin (SF) from Bombyx mori has been investigated widely by electrospinning to fabricate tissue engineering scaffolds. The mechanical properties of most electrospun SF scaffolds are still poor, although people have tried many ways to reinforce the scaffolds, such as using organic solvents, adding some reinforcing agents, post-treated with different methods, or using the cylinder to collect alighed SF fibers instead of the random fibers. Bladder acellular matrix graft (BAMG), a tough natural material, was already used in urethral reconstruction, penile reconstruction, myocardial repair, esophageal repair and fascial tissue reconstruction. In this study, we used BAMG to toughen the electrospun SF scaffolds with random or aligned fibers. Considering the essential role of vascularization in the success of tissue regenerating, we fabricate SF scaffolds loaded VEGF (Vascular endothelial growth factor), which is essential for tissue vasculogenesis and angiogenesis, by blend and coaxial electrospinning. Compared with the conventional SF mats, the SF/BAMG composite scaffolds were significantly reinforced. The morphology, microstructure and biocompatibility of the prepared scaffolds were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Wide angle X-ray diffraction (WAXD), Capillary Flow Porometer, Instron 5969 material testing machine and Laser Scanning Confocal Microscope (LSCM). An Elisa kit was adopted to investigate the release behaviors of VEGF loaded in the scaffolds. [ABSTRACT FROM AUTHOR]