New Opportunities for an Ancient Material

Department of Biomedical Engineering, Tufts University, Medford, MA 02155, USA.
Science (Impact Factor: 33.61). 07/2010; 329(5991):528-31. DOI: 10.1126/science.1188936
Source: PubMed


Spiders and silkworms generate silk protein fibers that embody strength and beauty. Orb webs are fascinating feats of bioengineering in nature, displaying magnificent architectures while providing essential survival utility for spiders. The unusual combination of high strength and extensibility is a characteristic unavailable to date in synthetic materials yet is attained in nature with a relatively simple protein processed from water. This biological template suggests new directions to emulate in the pursuit of new high-performance, multifunctional materials generated with a green chemistry and processing approach. These bio-inspired and high-technology materials can lead to multifunctional material platforms that integrate with living systems for medical materials and a host of other applications.

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    • "Spider dragline silk is a promising and outstanding protein polymer, which exhibits extraordinary mechanical properties of superior strength and toughness that make it outperform most of the natural and other synthetic fibers [1,2]. It is composed almost entirely of two proteins, major ampullate spidroins 1 (MaSp1) and 2 (MaSp2) [3,4]. "
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    ABSTRACT: Spider dragline silk exhibits excellent mechanical properties that make it a promising protein polymer for industrial and biomedical applications. Since farming spiders is not feasible due to their highly territorial nature, recombinant production of dragline silk proteins in a foreign host has received great attention. However, their production titer remains low, because efficient expression of very large, highly repetitive, glycine-rich silk proteins is a challenge. This work demonstrates the design and high-level production of large dragline silk proteins of major ampullate spidroin 2 (MaSp2) in Escherichia coli by synthetic biology approach. The expression levels of MaSp2 with molecular weight of 28.3–256.5 kDa were significantly elevated by down-shifting the induction temperature. The beneficial effect was found to be at least partially attributed to the improved plasmid maintenance in the recombinant cells. Combination of induction temperature downshift with the glycyl-tRNA pool increase in E. coli led to enhanced biosynthesis of glycine-rich silk proteins. A high production titer of about 3.6 g l−1 of a 201.6-kDa MaSp2 protein was achieved in a 3-L fed-batch bioreactor, which was the highest as reported. The developed approach may be useful to cost-effective large-scale production of silk proteins.
    Full-text · Article · Jan 2016
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    • "Silk fibroin (SF), the main constituent of the natural silk, is a natural biopolymer and a fibrous protein produced by silkworms or spiders. SF is the strongest and toughest natural fiber, with unusual high tensile strength and elasticity and proved to be both biocompatible and biodegradable [2] [3] [4] [5] [6] [7] [8] [9] [10]. It is subject to prolonged biological proteolytic degradation into easily absorbed aminoacids and is very slowly resorbed in vivo (around one year or more) [3]. "
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    ABSTRACT: Composite silk fibroin–poly(3-hydroxybutyric-acid-co-3-hydroxyvaleric-acid) (SF–PHBV) biodegradable coatings were grown by Matrix Assisted Pulsed Laser Evaporation on titanium substrates. Their physico-chemical properties and particularly the degradation behavior in simulated body fluid at 37 • C were studied as first step of applicability in local controlled release for tissue regeneration applications. SF and PHBV, natural biopolymers with excellent biocompatibility, but different biodegradability and tensile strength properties, were combined in a composite to improve their properties as coatings for biomedical uses. FTIR analyses showed the stoichiometric transfer from targets to coatings by the presence in the spectra of the main absorption maxima characteristic of both polymers. XRD investigations confirmed the FTIR results showing differences in crystallization behavior with respect to the SF and PHBV content. Contact angle values obtained through wettability measurements indicated the MAPLE deposited coatings were highly hydrophilic; surfaces turning hydrophobic with the increase of the PHBV component. Degradation assays proved that higher PHBV contents resulted in enhanced resistance and a slower degradation rate of composite coatings in SBF. Distinct drug-release schemes could be obtained by adjusting the SF:PHBV ratio to controllably tuning the coatings degradation rate, from rapid-release formulas, where SF predominates, to prolonged sustained ones, for larger PHBV content.
    Full-text · Article · Nov 2015 · Applied Surface Science
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    • "Conversely, many synthetic polymers require harsh processing conditions or result in acidic byproducts that could degrade encapsulated proteins [2]. Moreover, silk, due to its hydrophobic nature and crystallization, is inherently more resilient against changes in temperature, moisture and pH than other natural, synthetic, and biopolymers [3]. Purified silk protein can also be processed into various material formats which are conducive to uses as self-standing storage and stabilization matrices. "
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    ABSTRACT: Silk fibroin is a high molecular weight amphiphilic protein that self-assembles into robust biomaterials with remarkable properties including stabilization of biologicals and tunable release kinetics correlated to processing conditions. Cells, antibiotics, monoclonal antibodies and peptides, among other biologics, have been encapsulated in silk using various processing approaches and material formats. The mechanistic basis for the entrapment and stabilization features, along with insights into the modulation of release of the entrained compounds from silks will be reviewed with a focus on stabilization of bioactive molecules.
    Full-text · Article · Sep 2015 · Journal of Controlled Release
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