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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    • "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.
    Applied Surface Science 11/2015; 355:1123-1131. DOI:10.1016/j.apsusc.2015.07.120 · 2.71 Impact Factor
    • "Commercially, SF has been used for surgical sutures for decades and has biomedical applications because of its permeability to oxygen and water and protease susceptibility (Yan et al., 2010). The US Food and Drug Administration (FDA) has approved the use of SF for a few medical devices, such as blood vessels, peripheral nerve regeneration, femur defects and bone tissue engineering (Omenetto and Kaplan, 2010; Wang et al., 2008; Garcia-Fuentes et al., 2009). Hydroxyapatite (HaP) is a major mineral component of calcified tissues (bones and teeth). "
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    ABSTRACT: Advances in tissue engineering have enabled the development of bioactive composite materials to generate biomimetic nanofibrous scaffolds for bone replacement therapies. Polymeric biocomposite nanofibrous scaffolds architecturally mimic the native extracellular matrix (ECM), delivering tremendous regenerative potential for bone tissue engineering. In the present study, biocompatible poly(l-lactic acid)-co-poly(ε-caprolactone)–silk fibroin–hydroxyapatite–hyaluronic acid (PLACL–SF–HaP–HA) nanofibrous scaffolds were fabricated by electrospinning to mimic the native ECM. The developed nanofibrous scaffolds were characterized in terms of fibre morphology, functional group, hydrophilicity and mechanical strength, using SEM, FTIR, contact angle and tabletop tensile-tester, respectively. The nanofibrous scaffolds showed a higher level of pore size and increased porosity of up to 95% for the exchange of nutrients and metabolic wastes. The fibre diameters obtained were in the range of around 255 ± 13.4–789 ± 22.41 nm. Osteoblasts cultured on PLACL–SF–HaP–HA showed a significantly (p < 0.001) higher level of proliferation (53%) and increased osteogenic differentiation and mineralization (63%) for the inclusion of bioactive molecules SF–HA. Energy-dispersive X-ray analysis (EDX) data proved that the presence of calcium and phosphorous in PLACL–SF–HaP–HA nanofibrous scaffolds was greater than in the other nanofibrous scaffolds with cultured osteoblasts. The obtained results for functionalized PLACL–SF–HaP–HA nanofibrous scaffolds proved them to be a potential biocomposite for bone tissue engineering. Copyright © 2015 John Wiley & Sons, Ltd.
    Journal of Tissue Engineering and Regenerative Medicine 09/2015; DOI:10.1002/term.2083 · 5.20 Impact Factor
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    • "Significant progress has been made in the silkworm research because of the accomplishment of genome sequencing (Xia et al., 2014, 2004). Silkworm is the major source of natural silk fibers and an economically valuable insect worldwide (Omenetto and Kaplan, 2010). Sericulture is threatened by various entomopathogens . "
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    ABSTRACT: C-type lectins (CTLs) represent a large family of proteins that can bind carbohydrate moieties normally in a calcium-dependent manner. CTLs play important roles in mediating cell adhesion and the recognition of pathogens in the immune system. In the present study, we have identified 23 CTL genes in domestic silkworm B. mori. CTL-domain proteins (CTLDPs) are classified into three groups based on the number of carbohydrate-recognition domains (CRDs) and the domain architectures. These include twelve CTL-S (Single-CRD), six immulectins (Dual-CRD) and five CTL-X (CRD with other domains). We studied their phylogenetic features, analyzed the conserved residues, predicted tertiary structures, and examined the tissue expression profile and immune inducibility. Through bioinformatics analysis, we have putatively identified ten secretory and two cytoplasmic CTL-S; four secretory and two cytoplasmic immulectins; one secretory, one cytoplasmic and three transmembrane forms of CTL-X. Most B. mori CTLDPs form monophyletic groups with orthologs from Lepidoptera, Diptera, Coleoptera and Hymenoptera species. Immulectins of B. mori and M. sexta evolved from common ancestor genes perhaps due to gene duplication events of CTL-S ancestor genes. Homology modeling revealed that the overall structures of B. mori CTL domains are analogous to those of humans with a variable loop region. We examined the expression profile of CTLDP genes in naïve and immune-stimulated tissues. The expression and induction of CTLDP genes were related to the tissues and microorganisms. Together, our gene identification, sequence comparison, phylogenetic analysis, homology modeling and expression analysis laid a good foundation for the further studies of B. mori CTLDPs and comparative genomics. Copyright © 2015. Published by Elsevier Ltd.
    Developmental and comparative immunology 07/2015; 53(2). DOI:10.1016/j.dci.2015.07.005 · 2.82 Impact Factor
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