Raman and surface enhanced Raman scattering of a black dyed silk

The Raman and surface enhanced Raman scattering (SERS) spectra of a black dyed silk sample (BDS) were registered. The spectral analysis was performed on the basis of Raman and SERS spectral data of isolated samples of Bombyx mori silk fibroin, its motif peptide component (GAGAGS) and the synthetic reactive black 5 dye (RB5). The macro FT‐Raman spectrum of the silk sample is consistent with a silk II‐Cp crystalline fraction of Bombyx mori silk fibroin; the SERS spectrum is highly consistent with conformational modifications of the fibroin due to the interactions with the Ag nanoparticles. The GAGAGS peptide sequence dominates the Raman spectrum of the silk. The SERS spectrum of the peptide suggests a random coil conformation imposed by the surface interaction; the serine residue in the new conformation is exposed to the surface. Quantum chemical calculations for a model of the GAGAGS–Ag surface predict a nearly extended conformation at the Ag surface. The Raman spectrum of the dye was analysed, and a complete band assignment was proposed; it was not possible to propose a preferential orientation or organization of the molecule on the metal surface. Quantum chemical calculations for a model of the dye interacting with a silver surface predict a rather coplanar orientation of the RB5 on the Ag metal surface. The Raman spectrum of the BDS sample is dominated by signals from the dye; the general spectral behaviour indicates that the dye mainly interacts with the silk through the sulphone (–SO₂–) and sulphonate (–SO₂–O–) groups. Besides the presence of dye signals, mainly ascribed to the sulphone and sulphonate bands, the SERS spectrum of the BDS sample also displays bands belonging to the amino acids alanine, glycine, serine and particularly tyrosine. Copyright © 2013 John Wiley & Sons, Ltd.     

Origin of the variability of the mechanical properties of silk fibres: 1 ‐ The relationship between disorder,hydration and stress/strain behaviour

The causes of the variability in mechanical behaviour of various silks obtained from silkworms (Bombyx mori, Antheraea/Tussah) and spiders (Nephila madagascarensis) have been studied by tensile uniaxial tests, differential scanning calorimetry and Raman microspectrometry. Analyses of tensile stress–strain curves recorded for different silkworm and spider baves and single fibres, undergoing different histories (age, degumming, thermal/chemical treatments), allow the behaviour to be classified into five groups and correlated with the fibroin/spidroin structural status: (1) Type I exhibits linear elastic behaviour and then a quasi plateau, (2) Type II has a two‐step linear elastic behaviour with kinks then a quasi plateau, (3) Type III exhibits a smooth transition from a linear behaviour to a plateau, (4) Type IV has a behaviour rather similar to that of Type I but above ~8–12% hardening occurs, and (5) Type V results in the breakage of fibres during the first elastic stage. Unambiguously, Type IV is more frequent for degummed, very dried fibres and Type III for water‐saturated fibres. The most striking Raman signature differences are observed in the Raman intensity of the amorphous/‘ordered’ νN–H and H₂O band components and correlated to the water content and disorder degree according to the calorimetry study. Types I and II are frequently observed for fresh (largely amorphous) spun fibres/baves. Type V is characteristic of degraded fibres. Type IV represents the most ordered state. The similar stress–strain types for dried silkworm and spider fibres show that the general difference in amino acid contents is not the most pertinent parameter for the mechanical behaviour. Copyright © 2011 John Wiley & Sons, Ltd.     

Patterned Silk Film Scaffolds for Aligned Lamellar Bone Tissue Engineering

The alignment and osteogenic differentiation of MSCs on patterned silk films (PF) is investigated as a bottom‐up approach toward engineering bone lamellae. Screening PF with various groove dimensions shows that cell alignment is mediated by both the pattern width and depth. MSCs are differentiated in osteogenic medium for four weeks on flat films and on the PF that produce the best alignment. The PF support osteogenic differentiation while also inducing lamellar alignment of cells and matrix deposition. A secondary alignment effect is noted on the PF where a new layer of aligned cells grows over the first layer, but rotated obliquely to the underlying pattern. This layering and rotation of the MSCs resembles the cellular organization observed in native lamellar bone.

     

Collagen‐Reinforced Electrospun Silk Fibroin Tubular Construct as Small Calibre Vascular Graft

None of the replacements proposed in the literature for small‐calibre blood vessels (SCBV) fully satisfies the stringent requirements that these grafts have to fulfil. Here, an electrospun silk fibroin tubular construct is hybridized with type I collagen gel to produce a biomimetic SCBV graft with physiologically relevant compliance and burst pressure and optimal cytocompatibility. The hybridization of the two polymers results in the formation of a nanofibrillar hydrated matrix, where the collagen gel enhances the mechanical properties of the SF tubular construct and improves the early response of the material to in vitro cell adhesion and proliferation.

     

The Influence of Silkworm Species on Cellular Interactions with Novel PVA/Silk Sericin Hydrogels

Sericin peptides and PVA are chemically modified with methacrylate groups to produce a covalent PVA/sericin hydrogel. Preservation of the sericin bioactivity following methacrylation is confirmed, and PVA/sericin hydrogels are fabricated for both B. mori and A. mylitta sericin. Cell adhesion studies confirm the preservation of sericin bioactivity post incorporation in PVA gels. PVA/A. mylitta gels are observed to facilitate cell adhesion to a significantly greater degree than PVA/B. mori gels. Overall, the incorporation of sericin does not alter the physical properties of the PVA hydrogels but does result in significantly improved cellular interaction, particularly from A. mylitta gels.

     

再生丝素/NMMO·H2O溶液的流变性能

使用N-甲基吗啉-N-氧化物的水合物(NMMO·H2O)作为再生丝素的溶剂.可以得到w=0.10～0.25的再生丝素/NMMO·H2O溶液.研究了再生丝素/NMMO·H2O溶液流变性能,讨论了剪切速率、温度和溶液中的再生丝素的含量对再生丝素/NMMO·H2O溶液流变性能的影响.     

Characterization of a Water-Dispersed Biodegradable Polyurethane-Silk Composite Sponge Using 13C Solid-State Nuclear Magnetic Resonance as Coating Material for Silk Vascular Grafts with Small Diameters

Recently, Bombyx mori silk fibroin (SF) has been shown to be a suitable material for vascular prostheses for small arteries. In this study, we developed a softer SF graft by coating water-dispersed biodegradable polyurethane (PU) based on polycaprolactone and an SF composite sponge on the knitted SF vascular graft. Three kinds of ¹³C solid-state nuclear magnetic resonance (NMR), namely carbon-13 (¹³C) cross-polarization/magic angle spinning (MAS), ¹³C dipolar decoupled MAS, and ¹³C refocused insensitive nuclei enhanced by polarization transfer (r-INEPT) NMR, were used to characterize the PU-SF coating sponge. Especially the ¹³C r-INEPT NMR spectrum of water-dispersed biodegradable PU showed that both main components of the non-crystalline domain of PU and amorphous domain of SF were highly mobile in the hydrated state. Then, the small-diameter SF artificial vascular grafts coated with this sponge were evaluated through implantation experiments with rats. The implanted PU-SF-coated SF grafts showed a high patency rate. It was confirmed that the inside of the SF grafts was covered with vascular endothelial cells 4 weeks after implantation. These results showed that the water-dispersed biodegradable PU-SF-coated SF graft created in this study could be a strong candidate for small-diameter artificial vascular graft.     

类牙釉状丝胶蛋白/羟基磷灰石复合材料的合成及表征

采用化学沉淀法合成了丝胶蛋白(SS)/羟基磷灰石(HAP)复合材料, 并研究了矿化时间对复合材料的影响. X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、透射电镜(TEM/HRTEM)和扫描电镜(SEM)表征结果表明: 在较短的矿化时间内, 合成的SS/HAP为直径约20 nm的复合颗粒; 随着矿化时间的延长, 这些复合颗粒能够沿轴方向组装并融合成类牙釉结构的较大晶体. 文章讨论了其可能的组装机制.     

丝绸制作工艺中的化学知识

丝绸制作中的精炼、染色和保存与蚕丝的化学组成和结构密切相关。从蚕丝化学组成和结构出发介绍了丝绸精炼、染色和保存中的化学知识。