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True stress-true strain curves of naturally spun viscid line fibres retrieved directly from the spiral of orb-webs built by Argiope trifasciata spiders were measured using a novel methodology. This new procedure combines a method for removing the aqueous coating of the fibres and a technique that allows the accurate measurement of their cross-sectional area. Comparison of the tensile behaviour of different samples indicated that naturally spun viscid lines show a large variability, comparable to that of other silks, such as major ampullate gland silk and silkworm silk. Nevertheless, application of a statistical analysis allowed the identification of two independent parameters that underlie the variability and characterize the observed range of true stress-true strain curves. The combination of this result with previous mechanical and microstructural data suggested the assignment of these two independent effects to the degree of alignment of the protein chains and to the local relative humidity, which, in turn, depends on the composition of the viscous coating and on the external environmental conditions. [ABSTRACT FROM AUTHOR]

Silk refers to a family of natural fibers spun by several species of invertebrates such as spiders and silkworms. In particular, silkworm silk, the silk spun by Bombyx mori larvae, has been primarily used in the textile industry and in clinical settings as a main component of sutures for tissue repairing and wound ligation. The biocompatibility, remarkable mechanical performance, controllable degradation, and the possibility of producing silk-based materials in several formats, have laid the basic principles that have triggered and extended the use of this material in regenerative medicine. The field of neural soft tissue engineering is not an exception, as it has taken advantage of the properties of silk to promote neuronal growth and nerve guidance. In addition, silk has notable intrinsic properties and the by-products derived from its degradation show anti-inflammatory and antioxidant properties. Finally, this material can be employed for the controlled release of factors and drugs, as well as for the encapsulation and implantation of exogenous stem and progenitor cells with therapeutic capacity. In this article, we review the state of the art on manufacturing methodologies and properties of fiber-based and non-fiber-based formats, as well as the application of silk-based biomaterials to neuroprotect and regenerate the damaged nervous system. We review previous studies that strategically have used silk to enhance therapeutics dealing with highly prevalent central and peripheral disorders such as stroke, Alzheimer's disease, Parkinson's disease, and peripheral trauma. Finally, we discuss previous research focused on the modification of this biomaterial, through biofunctionalization techniques and/or the creation of novel composite formulations, that aim to transform silk, beyond its natural performance, into more efficient silk-based-polymers towards the clinical arena of neuroprotection and regeneration in nervous system diseases. [ABSTRACT FROM AUTHOR]

Straining Flow Spinning is a versatile and robust spinning technique for the production of regenerated silkworm silk fibers using mild chemistries. However, reaching high values of tensile strength and strain at breaking requires a step of wet-stretching in water, which limits scalability and the practical usage of the technique. Here, we show that adding a post-spinning drawing step to the procedure improves the performance of the fibers, and allows the development of a scalable process. It is also shown that the properties of the fiber can be tuned by varying the parameters of the post-spinning step. Finally, equivalence is established between the discrete wet-stretching process and the continuous post-spinning drawing step. [ABSTRACT FROM AUTHOR]

As spun silkworm ( Bombyx mori ) silk fibers were compared in terms of their tensile behavior and microstructure with fibers subjected to different degumming treatments. Fibers were initially retrieved by forced silking directly from the worms and, either characterized in the as spun condition, or subjected to one of the following treatments: immersion in water, conventional degumming or degumming under longitudinally constrained conditions. Microstructure was assessed by X-ray diffraction and Raman spectroscopy. In addition, polyacrylamide gel electrophoresis was used to determine the influence of degumming on silk at a molecular level. Our study not only shows that degumming represents a major contribution to the accepted idea of silkworm silk as a highly variable material, but also provides new insights in the relationship between microstructure and tensile behavior in these fibers. In particular, it is shown that the arrangement of the hydrogen bond network in fibers subjected to different treatments plays a critical role in determining the mechanical behavior of silkworm silk. [ABSTRACT FROM AUTHOR]

Spider silk fibers were produced through an alternative processing route that differs widely from natural spinning. The process follows a procedure traditionally used to obtain fibers directly from the glands of silkworms and requires exposure to an acid environment and subsequent stretching. The microstructure and mechanical behavior of the so-called spider silk gut fibers can be tailored to concur with those observed in naturally spun spider silk, except for effects related with the much larger cross-sectional area of the former. In particular spider silk gut has a proper ground state to which the material can revert Independently from its previous loading history by supercontraction. A larger cross-sectional area implies that spider silk gut outperforms the natural material in terms of the loads that the fiber can sustain. This property suggests that it could substitute conventional spider silk fibers in some intended uses, such as sutures and scaffolds in tissue engineering. [ABSTRACT FROM AUTHOR]

Regenerated silk fibroin solutions from Bombyx mori were tested for electrospinning. Simple and reproducible tensile tests were performed on threads of aligned fibers to obtain information about their mechanical performance at the fiber level. The binary solvent formic acid/chloroform (10:1, v/v) rendered unbeaded thinner fibers with increased extensibility before failure when compared with pure formic acid. A remarkable improvement in strength was induced by immersing length-restricted fibers into ethanol for 5 min. Conformational changes of the protein chains were studied by solid-state NMR. [ABSTRACT FROM AUTHOR]

Regenerated silkworm fibers spun through a wet-spinning process followed by an immersion postspinning drawing step show a work to fracture comparable with that of natural silkworm silk fibers in a wide range of spinning conditions. The mechanical behavior and microstructure of these high performance fibers have been characterized, and compared with those fibers produced through conventional spinning conditions. The comparison reveals that both sets of fibers share a common semicrystalline microstructure, but significant differences are apparent in the amorphous region. Besides, high performance fibers show a ground state and the possibility of tuning their tensile behavior. These properties are characteristic of spider silk and not of natural silkworm silk, despite both regenerated and natural silkworm silk share a common composition different from that of spider silk. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 [ABSTRACT FROM AUTHOR]