Mechanical and thermal properties of dragline silk from the spider Nephila clavipes

Abstract

Dragline silk from the spider, Nephila clavipes, was characterized b y thermal analysis (TGA, DSC, DMA), computational modeling, scanning electron microscopy and by quasi-static as well as high rates of strain. Thermal stability to about 230°C was observed by TGA, two transitions by D M A , -75"C, representative of localized motion in the amorphous domain, and a main chain motion associated with partial melt at 210°C. Tensile tests indicated average initial modulus, ultimate tensile strength and ultimate tensile strain of 22 GPa, 1.1 GPa and 9%, respectively. The corresponding properties of the best fibers tested were 60 GPa, 2.9 GPa and 11 %, respectively. High strain rates (>50,000%/ see) indicated similar mechanical properties to the average values indicated above. Microscopy showed compressive and tensile strains to failure of 34%. Computational modeling yielded a cystal modulus of 200 GPa.

Silk based biomaterials to heal critical sized femur defects

“…Silk fibroin, the structural, hydrophobic, and approximately 370 kDa protein isolated from the cocoon of B. mori [43][44][45][46] that has emerged as a novel substrate for engineering biomaterials, has proven to be biocompatible [22,33], offers distinguishing mechanical properties when compared to other naturally derived or degradable polymeric biomaterials [47], and exhibits low inflammatory response [21,22].…”

Silk-based biomaterials

“…The unique organization of the family of silk genes in more advanced spiders provides a fertile area for the exploration of structure-function relationships in protein design. For example, the dragline spider silk from the golden orb weaver N. clavipes displays impressive toughness, and a balance of stiffness, strength and extensibility reflecting the native function of the silk orb web construction [7,13,14]. Transgenic expression of spider silks in plants (tobacco and potato) and mammalian epithelial cells has been reported [15,16] and may point the way toward more substantive production of these proteins in the future.…”

“…The distinguishing features of the spider silks are the very high strength in combination with excellent elasticity in comparison with these other biomaterials. In addition, these fibers display resistance to failure in compression that distinguishes them from other high performance fibers, such as Kevlar [13].…”

“…c Bombyx mori silkworm silk-average calculated from data in Ref. [13]. d Nephila clavipes silk produced naturally and through controlled silking.…”

“…For example, in the case of bone, biomaterials that can provide robust support during compression would be advantageous, and silks are known to function well under compression with little evidence for cracking or crazing under conditions in which synthetic high performance fibers fail [13]. Furthermore, in the case of ligaments, the high tensile strength of silks provides a strong advantage in matching ligament function to immediately restore knee function, a feature difficult to achieve with collagen [61].…”