Electrospun core–sheath fibers for integrating the biocompatibility of silk fibroin and the mechanical properties of PLCL

In the process of preparing core–sheath fibers via coaxial electrospinning, the relative evaporation rates of core and sheath solvents play a key role in the formation of the core–sheath structure of the fiber. Both silk fibroin (SF) and poly(lactide‐co‐ε‐caprolactone) (PLCL) have good biocompatibility and biodegradability. SF has better cell affinity than PLCL, whereas PLCL has higher breaking strength and elongation than SF. In this work, hexafluoroisopropanol (HFIP)‐formic acid (volume ratio 8:2), HFIP and HFIP–dichloromethane (volume ratio 8:2) were used to dissolve PLCL as the core solutions, and HFIP was used to dissolve SF as the sheath solution. Then, core–sheath structured SF/PLCL (C‐SF/PLCL) fibers were prepared by coaxial electrospinning with the core and sheath solutions. Transmission electron microscopy images indicated the existence of the core–shell structure of the fibers, and energy dispersive X‐ray analysis results revealed that the fiber mat with the greatest content of core–shell structure fibers was obtained when the core solvent was HFIP–dichloromethane (volume ratio 8:2). Tensile tests showed that the C‐SF/PLCL fiber mat displayed improved tensile properties, with strength and elongation that were significantly higher than those of the pure SF mat. The C‐SF/PLCL fiber mat was further investigated as a scaffold for culturing EA.hy926 cells, and the results showed that the fiber mat permitted cellular adhesion, proliferation and spreading in a manner similar to that of the pure SF fiber mat. These results indicated that the coaxial electrospun SF/PLCL fiber mat could be considered a promising candidate for tissue engineering scaffolds for blood vessels. Copyright © 2014 John Wiley & Sons, Ltd.     

仿生定向液体输送的功能材料表面设计与应用

无外界能量输入及设备辅助的情况下,在基底表面上控制液体自发输送在微流控和流体低能耗运输中具有重要意义。然而,液体的自发输送会被接触角滞后效应及摩擦阻力所阻碍。自然界中的生物(如蝴蝶翅膀、仙人掌、猪笼草、蜘蛛丝和沙漠甲虫)特殊的表面形貌结构能够将收集到的水分自发输送。受此启发,通过表面调控等方法人工合成材料的仿生表界面也可以自发运输液体。近十余年,仿生表面的液体定向输送得到了广泛关注和深入研究,预期在定向集水、宏观液体输送、油水分离、微流控系统等领域具有广泛的应用前景。本综述系统地介绍了定向运输液体功能材料的原理、合成方法及其应用,深入解析了制约其应用的主要因素,并总结和展望了定向运输液体的功能材料在未来发展中所面对的机遇与挑战。     

蜘蛛吐丝过程中钾的作用

用电感耦合等离子体质谱(ICP-MS)对蜘蛛Nephila丝腺体和丝进行测定,结果表明,钾在丝中的含量明显高于在丝腺体中的含量.同时,在蜘蛛丝蛋白溶液中加入氯化钾,溶液出现乳白色浑浊,表明有呈β-折叠构象的微纤产生.浊度测试发现,丝蛋白微纤会逐渐聚集成较大颗粒而在溶液中形成沉淀.另外,红外光谱和拉曼光谱亦证明钾能够使蜘蛛丝蛋白膜发生从无规线团/螺旋到β-折叠的构象转变.有理由认为钾在蜘蛛吐丝过程中起重要作用,它的存在有利于丝蛋白形成β-折叠结构.     

基于动物丝蛋白的人工纺丝

动物丝,特别是蜘蛛丝近年来由于其优异的综合力学性能而备受关注。但是天然动物丝的应用由于种种原因而受到各种限制,因此人们期望通过人工纺丝获得性能与天然动物丝相近的人工丝纤维。本文就采用动物丝蛋白进行人工纺丝的历史和现状,从再生蜘蛛丝蛋白、重组蜘蛛丝蛋白和再生蚕丝蛋白等方面进行综述,比较了天然动物丝和人工丝纤维的力学性能,并且探讨了人工生物模拟纺丝制备高性能人工丝纤维(超级纤维)的前景。     

Study by Raman spectromicroscopy of the effect of tensile deformation on the molecular structure of Bombyx mori silk

The effect of mechanical deformation on the polarized Raman spectra of a silk monofilament of the silkworm Bombyx mori has been studied in order to detect tensile stress-induced changes of the fibroin conformation and reorientation up to the breaking point. For this study, a motorized mechanical stretcher has been specifically designed to fit under the Raman microscope, thus allowing the simultaneous recording of the stress, strain and polarized Raman spectra. Due to its twin drive screw design, this stretcher allows to stretch the silk fiber symmetrically and thus to probe the same area of the fiber during the entire elongation procedure. The results obtained have allowed to clarify the assignment of some vibrational bands of silk. They also show that the intensity of some Raman bands is affected by tensile deformation. In particular, the amide III/amide I intensity ratio decreases as the strain increases and the variation is proportional to the stress applied on the fiber. These variations in intensity suggest that the alignment of the protein chains decreases with strain which might be due to the reorganization of the amorphous phase. The Raman spectra also show that several bands shift toward low wavenumbers as the strain applied increases indicating that the force constant and/or dihedral angles of the peptide bonds, in particular those involved in the β-sheets, are affected by drawing. Therefore, a local stress is directly applied on the β-sheets and the wavenumber shift observed is proportional to the stress applied on the fiber.     

Structure and compatibility of poly(vinyl alcohol)-silk fibroin (PVA/SA) blend films

The structure and compatibility of poly(vinyl alcohol)-silk fibroin (PVA/SF) blend films were analyzed by differential scanning calorimetry (DSC), thermomechanical (TMA) and thermogravimetric (TGA) analysis, x-ray diffractometry, and scanning (SEM) and transmission (TEM) electron microscopy. DSC curves of PVA/SF blend films showed a major endothermic peak at 220°C, along with a peak at 280°C. These endotherms were assigned to the thermal decomposition of the ordered PVA elements and to the thermal degradation of silk fibroin, respectively. The PVA/SF blends behaved in a manner intermediate to the pure components, as suggested by both contraction expansion and sample weight retention properties recorded by TMA and TGA measurements. The IR absorption spectra of the blends were identified as purely a composite of the absorption bands characteristic of both PVA and SF pure polymers. The X-ray diffraction patterns of PVA/SF blends showed overlapping spacing due to PVA and SF. A dispersed phase formed by spherical particles of 3–7 μm diameter was observed by SEM and TEM. All these findings suggest that PVA and SF are incompatible. © 1994 John Wiley & Sons, Inc.     

蚕丝蛋白的NMR研究Ⅱ.桑、柞蚕丝及其丝素的13C CP-MAS NMR研究

本文在Bruker AC-250和MSL-400谱仪上,首次测试了河南桑蚕茧、丝素及柞蚕黄茧、人工白茧和丝素的固态¹³C CP MAS NMR谱,归属了¹³C NMR谱线,并揭示了白茧和黄茧二级结构的差异。     

Multiple scattering effect in the Young-like interference pattern of an optical wave scattered by a double cylinder

The plane-polarized laser wave with a wavelength of 441.6 nm collides with two close parallel cylinders, called a double cylinder, each of a diameter about 100 or 200 nm at normal incidence. The measured angular distribution of the scattered light intensity, called a Young-like interference pattern, is compared with the rigorous theoretical calculation over a wide range of scattering angles. We have experimentally confirmed the multiple scattering effect of the wave between cylinders in an exact way.     

羟基磷灰石/丝素蛋白复合纤维的制备及其矿化研究

在以静电纺丝法制备羟基磷灰石(HAP)/丝素蛋白(SF)复合纤维的前提下, 采用同轴共纺法获得了以HAP为“芯”、SF为“皮”的双组分电纺纤维(电纺膜), 并通过扫描和透射电镜、红外光谱以及X射线衍射等手段对电纺纤维进行了表征. 结果表明, HAP均存在于上述两种方法制备的纳米纤维中, 但同轴共纺法不仅可以避免HAP/SF共混电纺时pH值对丝素蛋白结构的影响, 并且能大大提高电纺膜中HAP的含量. 同时, 我们还分别以SF纤维、HAP/SF复合纤维和HAP/SF“皮-芯”纤维作为有机基质, 对羟基磷灰石在其上的矿化过程进行了探索, 结果表明含较多羟基磷灰石的HAP/SF“皮-芯”纤维更有利于矿化的进行.     

Physics of engineered protein hydrogels

Artificially engineered proteins and synthetic polypeptides have attracted widespread interest as building blocks for polymer hydrogels. The biophysical properties of the proteins, such as molecular recognition abilities, folded chain structures, and sequence-dependent thermodynamic behavior, enable advances in functional, responsive, and tunable gels. This review discusses the design of polymer hydrogels that incorporate protein domains, highlighting new challenges in polymer physics that are presented by this emerging class of materials. Five types of engineered protein hydrogels are discussed: (a) physically associating protein polymer gels, (b) amorphous artificially engineered protein networks, (c) engineered proteins with crystalline domains, (d) stretchable protein tertiary structures in gels, and (e) protein gels with biological recognition properties. The physics of the protein component and the physical properties of the resulting hydrogels are summarized, illustrating how advances in understanding these systems are leading to exciting novel biofunctional hydrogels. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013