Biomimetic Spinning of Recombinant Silk Proteins
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1239-VV07-20
Biomimetic spinning of recombinant silk proteins David Keerl1, John G. Hardy1 and Thomas Scheibel1 1 Lehrstuhl Biomaterialien, Universitaet Bayreuth, Universitaetsstr. 30, 95447 Bayreuth, Germany
ABSTRACT
In the past, we have successfully designed and produced a variety of engineered spider silk-like proteins (eADF3 and eADF4) based upon the primary sequence of the natural dragline proteins ADF3 and ADF4 from the spider Araneus diadematus [1]. Genetically engineered spider silk proteins can be modified at the molecular level to optimize the biochemical and mechanical properties of the final product. Although engineered spider silk proteins can be processed into fibers using different spinning methods, our group is interested in the technical realization of a biomimetic approach. Here, we present an overview over our biomimetic fiber production process.
INTRODUCTION
Spider silk has been widely used as a material, long before it came in focus of scientists, for wound dressing (in Ancient Greece), for fishing (Australasia) and later on, for military purposes, e.g. the construction of crosshairs [2, 3]. The variety of applications of spider silk is based on its mechanical stability, biocompatibility, smoothness and thinness in comparison to other available materials [2]. Female orb weaving spiders produce up to 5 different silks with different properties to construct their orb webs [4, 5]. The frame and radii of an orb-web are constructed from dragline silk, whose main constituents are mainly two Major Ampullate Spidroins (MAS). Among all types of silk, dragline silk shows the greatest toughness [2], being five times tougher than steel (on a weight basis) and even three times tougher than man-made synthetic fibers such as Kevlar 49™ [6-8].
crystalline
amorphous
Figure 1. Scheme showing the crystalline and amorphous segments in a dragline silk thread The MAS are mainly composed of repetitive motifs that are responsible for the formation of amorphous and crystalline regions within the fibers (see Figure 1), which define the fiber’s mechanical properties. During fiber formation, the proteins self-assemble in a complex process involving several physico-chemical steps (see below). In order to employ spider silk for technological applications, our group, amongst others, investigates the various processes accounting for the formation of silk fibers.
SPINNING OF RECOMBINANT SPIDER SILK PROTEINS
Production of recombinant spider silk proteins
The aforementioned fascinating properties of spider silk, and thus its high potential for novel technical applications, has aroused increasing interest in the production of large quantities of spider silk proteins. However, the production of spider silk has experienced numerous problems in the past. Unlike silk producing insects, such as the silkworm Bombyx mori, spiders are cannibalistic and territorial, strictly limiting farming and, therefore, the availability of their silk [9]. Therefore, recombinant production of spider silk proteins is considered to be a promis
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