静电纺丝——从无规纳米纤维膜到取向连续长纱

静电纺丝是通过对聚合物溶液或熔体施加外电场制造纳米纤维的有效方法.电纺过程中,在静电力作用下聚合物射流快速鞭动,形成的纳米纤维无规堆砌,得到无纺布状的无规纳米纤维膜.这种纳米纤维膜具有极大的比表面积,已用于超高效过滤,在刨伤修复、组织工程、水处理等领域有广泛的应用前景.为了进一步拓展纳米纤维在纤维工业、纺织品、微制造等领域的应用,电纺纳米纤维的取向和连续长纱的制备研究受到科学家的重视,文献报道了多种纳米纤维取向方法.本文分析了纳米纤维膜无规堆砌结构的形成机理,总结了纳米纤维取向研究和连续长纱制备研究进展,特别介绍了基于静电作用分析提出的共轭电纺方法,讨论了取向纳米纤维的应用以及纳米纤维未来的研究方向.     

Preparation and characterization of a novel electrospun spider silk fibroin/poly(D,L-lactide) composite fiber

In the paper, we successfully prepared spider silk fibroins (Ss)/poly( d, l-lactide) (PDLLA) composite fibrous nonwoven mats for the first time to the best of our knowledge. The morphology of the fibers was observed by a scanning electron microscope (SEM) and transmission electron microscope (TEM). The secondary structure change of the spidroin before and after electrospinning was characterized using Fourier transform infrared spectroscopy (FT-IR). Herein, a qualitative analysis of the conformational changes of the silk protein was performed by analyzing the FT-IR second-derivative spectra, from which quantitative information was obtained via the deconvolution of the amide I band. A mechanical test was carried out to investigate the tensile strength and the elongation at break. A water contact angle (CA) measurement was also performed to characterize surface properties of the fibers. The cytotoxicity of electrospun PDLLA and Ss-PDLLA nonwoven fibrous mats was evaluated based on a CCL 81(Vero) cells proliferation study. The results showed that the hydrophilic and mechanical property of the composite fiber were improved by introducing spidroin.     

Determination of lead in fine particulates by slurry sampling electrothermal atomic absorption spectrometry

A simple method for determining lead in fine particulates (PM2.5) by using electrothermal atomic absorption spectrometry (ETAAS) has been developed. Particulates collected on Nuclepore filter by using a dichotomous sampler were suspended in diluted nitric acid after ultrasonic agitation. The dislodging efficiency is nearly 100% after agitation for 5 min. In order to study the suspension behavior of PM2.5 in solvents, a Brookhaven ZetaPlus Particle Size Analyzer was used to determine the particle size distribution and suspension behavior of air particulates in the solvent. The pre-digestion and modification effect of nitric acid would be discussed. Palladium was added as a chemical modifier and the temperature program of ETAAS was changed in order to improve the recovery. The slurry was introduced directly into a graphite tube for atomization. The metal content in the sample was determined by the standard addition method. In addition, a conventional acid digestion procedure was applied to verify the efficiency of the slurry sampling method. It offers a quick and efficient alternative method for heavy metal characterization in fine particulates.     

Characterization of Hydrogels Made of a Novel Spider Silk Protein eMaSp1s and Evaluation for 3D Printing

Recombinantly produced spider silk proteins have high potential for bioengineering and various biomedical applications because of their biocompatibility, biodegradability, and low immunogenicity. Here, the recently described small spider silk protein eMaSp1s is assembled into hydrogels, which can be 3D printed into scaffolds. Further, blending with a recombinantly produced MaSp2 derivative eADF4(C16) alters the mechanical properties of the resulting hydrogels. Different spider silk hydrogels also show a distinct recovery after a high shear stress deformation, exhibiting the tunability of their features for selected applications.     

蜘蛛与蚕的人工强制纺丝研究进展

为制备高性能人造蜘蛛丝和蚕丝,人们在蜘蛛丝蛋白的基因重组、再生蜘蛛丝蛋白或蚕丝蛋白的仿生纺丝,以及蜘蛛与蚕的人工强制纺丝方面开展了大量工作.研究了人工强制纺丝,比较了蜘蛛牵引丝和蚕丝在不同纺丝条件下的力学性能.结果表明:在一定范围内增加纺丝速率有利于提高蜘蛛丝和蚕丝的力学性能,此外,环境温度、纺丝状态等条件对丝的性能也...     

Biofabrication of Cell‐Loaded 3D Spider Silk Constructs

Biofabrication is an emerging and rapidly expanding field of research in which additive manufacturing techniques in combination with cell printing are exploited to generate hierarchical tissue‐like structures. Materials that combine printability with cytocompatibility, so called bioinks, are currently the biggest bottleneck. Since recombinant spider silk proteins are non‐immunogenic, cytocompatible, and exhibit physical crosslinking, their potential as a new bioink system was evaluated. Cell‐loaded spider silk constructs can be printed by robotic dispensing without the need for crosslinking additives or thickeners for mechanical stabilization. Cells are able to adhere and proliferate with good viability over at least one week in such spider silk scaffolds. Introduction of a cell‐binding motif to the spider silk protein further enables fine‐tuned control over cell–material interactions. Spider silk hydrogels are thus a highly attractive novel bioink for biofabrication.     

Determination of lead in fine particulates by slurry sampling electrothermal atomic absorption spectrometry

A simple method for determining lead in fine particulates (PM_2.5) by using electrothermal atomic absorption spectrometry (ETAAS) has been developed. Particulates collected on Nuclepore filter by using a dichotomous sampler were suspended in diluted nitric acid after ultrasonic agitation. The dislodging efficiency is nearly 100% after agitation for 5 min. In order to study the suspension behavior of PM_2.5 in solvents, a Brookhaven ZetaPlus Particle Size Analyzer was used to determine the particle size distribution and suspension behavior of air particulates in the solvent. The pre-digestion and modification effect of nitric acid would be discussed. Palladium was added as a chemical modifier and the temperature program of ETAAS was changed in order to improve the recovery. The slurry was introduced directly into a graphite tube for atomization. The metal content in the sample was determined by the standard addition method. In addition, a conventional acid digestion procedure was applied to verify the efficiency of the slurry sampling method. It offers a quick and efficient alternative method for heavy metal characterization in fine particulates. Received: 2 August 2000 / Revised: 25 October 2000 / Accepted: 28 October 2000     

Production and processing of spider silk proteins

Natural spider silk fibers have impressive mechanical properties (outperforming many man‐made fibers) and are, moreover, biocompatible, biodegradable, and produced under benign conditions (using water as a solvent at ambient temperature). The problems associated with harvesting natural spider silks inspired us to devise a method to produce spider silk‐like proteins biotechnologically (the first subject tackled in this highlight); we subsequently discuss their processing into various materials morphologies, and some potential technical and biomedical applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3957–3963, 2009     

从天然动物丝到丝蛋白基材料的研究

作为具有优异综合力学性能的天然蛋白质纤维,丰产的动物丝特别是蚕丝长期伴随着人们的日常生活,近十余年来,各种具有特色的功能性丝蛋白基材料更是层出不穷.但在探索动物丝和丝蛋白基材料的过程中,动物丝纤维是经由蚕或蜘蛛等动物的纺器而纺制得到的简单事实往往被忽视;换言之,动物丝实际上是动物对丝蛋白进行体内“加工”后的产物,也是丝蛋白基材料中的一种.因此,天然动物丝中独特的各等级间构效关系与丝蛋白基材料的构效关系之间并不存在着必然的传承效应.本文着重介绍了我们在对动物丝和丝蛋白基材料探索中的经验和体会,即在强调以丝蛋白分子链结构与性能及其之间的关系为研究重点的基础上,从比较和发掘各种天然动物丝的特性入手,进而了解丝蛋白分子链在本体和溶液中的行为,并通过对动物丝蛋白分子链聚集态结构的调控,以达到设计制备一系列多形貌和多功能的动物丝蛋白基材料的目的.     

Spider silk and amyloid fibrils: a structural comparison

Although spider silks have been studied for decades, the assembly properties of the underlying silk proteins have still not been unravelled. Previously, the detection of amyloid-like nanofibrils in the spider's silk gland suggested their involvement in the assembly process.Recombinantly produced spider silk also self-assembles into nanofibrils. In order to investigate the structural properties of such silk nanofibrils in more detail, they have been compared to amyloid-like fibrils to highlight structural similarities.     

Semicontinuous production of lipase by Acinetobacter radioresistens in presence of nonwoven fabric

The effect of a hydrophobic nonwoven fabric on the lipase production by Acinetobacter radioresistens was investigated with semicontinuous culture. The fermentation medium contained n-hexadecane as the carbon source. The nonwoven fabric was made from nylon 6 and coated with an acrylic resin. Equipping the nonwoven fabric around the baffles of a 2.5-L agitated fermentor could provide a fine dispersion of n-hexadecane, thus enhancing lipase production. The improvement on lipase yield by using the nonwoven fabric was found to be comparable to that of using an emulsifier (gum arabic). Compared with the corresponding culture in the absence of nonwoven fabric, the employment of the nonwoven fabric could significantly enhance both lipase yield and volumetric productivity.     

Correlation between processing conditions,microstructure and mechanical behavior in regenerated silkworm silk fibers

Regenerated silkworm fibers spun through a wet‐spinning process followed by an immersion postspinning drawing step show a work to fracture comparable with that of natural silkworm silk fibers in a wide range of spinning conditions. The mechanical behavior and microstructure of these high performance fibers have been characterized, and compared with those fibers produced through conventional spinning conditions. The comparison reveals that both sets of fibers share a common semicrystalline microstructure, but significant differences are apparent in the amorphous region. Besides, high performance fibers show a ground state and the possibility of tuning their tensile behavior. These properties are characteristic of spider silk and not of natural silkworm silk, despite both regenerated and natural silkworm silk share a common composition different from that of spider silk. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Hydrophobic and Hofmeister effects on the adhesion of spider silk proteins onto solid substrates: an AFM-based single-molecule study

AFM-based single-molecule force spectroscopy has been used to study the effect of Hofmeister salts and protein hydrophobicity on the adhesion of recombinant spider silk proteins onto solid substrates. Therefore, a molecular probe consisting of a spider silk protein and an AFM tip has been developed, which (i) is a well-defined, small system that can be simulated by molecular dynamics simulations, (ii) allows access to the whole soluble concentration range for ions, and (iii) provides the distribution of desorption forces rather than just ensemble-averaged mean values. The measured desorption forces follow the Hofmeister series for anions (H2PO4-, Cl-, I-) with a stabilizing energy of more than 15 kBT for 5 M NaH2PO4. Moreover, this effect is influenced by the hydrophobicity of the spider silk protein, indicating that hydrophobic and Hofmeister effects are closely related.     

Nephila clavipes spider dragline silk microstructure studied by scanning transmission X-ray microscopy

Nephila clavipes dragline silk microstructure has been investigated by scanning transmission X-ray microscopy (STXM), a technique that allows quantitative mapping of the level of orientation of the peptide groups at high spatial resolution (<50 nm). Maps of the orientation parameter P2 have been derived for spider silk for the first time. Dragline silk presents a very fine microstructure in which small, highly oriented domains (average area of 1800 nm2, thus clearly bigger than individual beta-sheet crystallites) are dispersed in a dominant, moderately oriented matrix with several small unoriented domains. Our results also highlight the orientation of the noncrystalline fraction in silk, which has been underestimated in numerous structural models. No evidence of either a regular lamellar structure or any periodicity along the fiber was observed at this spatial resolution. The surface of fresh spider silk sections consists of a approximately 30-120 nm thick layer of highly oriented protein chains, which was found to vary with the reeling speed, where web building (0.5 cm/s) and lifeline (10 cm/s) spinning speeds were investigated. While the average level of orientation of the protein chains is unaffected by the spinning speed, STXM measurements clearly highlight microstructure differences. The slowpull fiber contains a larger fraction of highly oriented domains, while the protein chains are more homogeneously oriented in the fastpull fiber. In comparison, cocoon silk from the silkworm Bombyx mori presents a narrower orientation distribution. The strength-extensibility combination found in spider dragline silk is associated with its broad orientation distribution of highly interdigitated and unoriented domains.     

燃烧源PM2.5凝结洗涤脱除实验研究

利用蒸汽在燃烧源PM2.5表面凝结,促使PM2.5凝结长大,建立一套燃烧源PM2.5凝结洗涤的实验台;考察了颗粒粒径分布、蒸汽添加量、液气比等对两种燃烧源PM2.5凝结洗涤脱除效果的影响。采用电称低压冲击器 (ELPI)在线测试分析燃煤和燃油PM2.5凝结洗涤前后的数浓度和粒径分布特性,并用SEM和XPS对两种不同燃烧源的颗粒进行了形貌和元素组分分析。结果表明,燃煤和燃油产生的PM2.5形貌和组分具有较大的差别,燃煤PM2.5主要为硅铝矿物质,而燃油PM2.5主要为含炭物质;相同条件下,燃煤PM2.5相变脱除效果优于燃油PM2.5;随着蒸汽添加量的增加,两者的脱除效率均升高;随粒径的增大,脱除效率提高;蒸汽添加量为0.08kg/m3时,粒径为0.4μm的燃煤和燃油细颗粒的脱除效率分别81％和72％;此外,适当增加液气比有利于凝结长大含尘液滴的脱除。     

炉前煤低温干馏工艺中的挥发分除尘

为了寻求优化的炉前煤低温干馏工艺中的挥发分除尘方案,在使用400目金属滤网对间歇式粉煤固体热载体热解装置挥发分除尘研究的基础上,将颗粒床过滤器用于该过程的除尘研究。热态除尘实验表明,颗粒床的使用有效地降低了滤网的过滤负荷。选用2mm石英砂和φ5mm×2mm瓷环作为滤料,通过对比实验发现,两种滤料除尘效率均在90％以上;随着过滤操作的进行,由于颗粒床内粉尘的沉积使其过滤效率有所提高,而对气、液收率的影响很小。结果表明,颗粒床与滤网结合可作为粉煤炉前低温干馏工艺中可供选择的挥发分除尘方案。     

一种天然纳米纤维捕鸟蛛丝的物理化学结构表征

蜘蛛丝作为功能性结构材料, 其独特的纤维成型方法与优良的结构和性能引起许多人的关注. 从20世纪80年代开始有关蜘蛛丝的研究报道日益增加[1]. 与高温高压下或由溶剂纺丝成型的合成纤维相比, 蜘蛛丝在空气中凝固成型, 丝纤维成型安全、无害, 从腹部若干不同吐丝器产生不同种类的丝具有不同的用途[2]. 蜘蛛拖曳丝(dragline silk)的比强度大于钢丝, 且具有较大的断裂伸长率(9%～30%)[3,4], 抗张强度1.1～1.4 GPa. 在相对湿度50%和应变速率100%/min的条件下, 模量值可达10～50 GPa. 在所有已知纤维品种中, 蜘蛛丝的断裂能是最高的. 此外, 蜘蛛丝在许多方面的综合性能优于最优良的人造纤维. 另外, 蜘蛛丝的细度为已知纤度最小的天然有机纤维, 这种高性能丝具有捕捉昆虫甚至鸟类的功能, 因此蜘蛛丝是具有特异功能的天然纤维材料. 目前, 蜘蛛丝结构和性能的研究主要包括其化学组成[5]、结晶结构[6,7]、结构模型[8,9]以及其NMR表征[10]等, 这些研究揭示了蜘蛛丝的氨基酸组成、分子量及其分布、结晶度、晶胞尺寸、链构象以及结构模型等. 这些研究主要集中在少数几种蜘蛛品种上, 如金色圆网织网蛛(Nephila clavipes)、十字圆蛛(A.diadematus)和大腹圆蛛(A.ventrocosus)等. 目前, 已知的蜘蛛种类大于30 000种[11], 以蜘蛛丝为例的生物大分子材料研究是一个挑战性的课题. 国内蜘蛛丝的研究仅有大腹圆蛛拖曳丝蛋白一级结构的研究报道[12,13]. 本文报道了广西捕鸟蛛丝的红外光谱、形貌结构和原子力显微镜的初步研究结果.     

Spinnenseide in der plastischen Chirurgie. Wunderwerkstoff der Natur

The experimental data show that the production of artificial nerve grafts with spider silk is a potential alternative therapy. The biologically favourable properties of the fibres from the spider Nephila clavipes should be used in human nerve reconstruction. The biological fibres promote the proliferation of cells. They are immunologically tolerated and not rejected. The muscle attraction line is kept intact which prevents muscle degeneration to a large extent. The spider fibres accelerate the migration of peripheral schwann cells into the nerve construct and promote the alignment of the nerve cells. For surgical interventions the biomechanical stability of spider silk and the composition from essential amino acids make the spider silk fibres interesting as a matrix for the cellular regeneration and in particular as a guiding structure for nerve regeneration.     

Basic Principles in the Design of Spider Silk Fibers

The prominence of spider silk as a hallmark in biomimetics relies not only on its unrivalled mechanical properties, but also on how these properties are the result of a set of original design principles. In this sense, the study of spider silk summarizes most of the main topics relevant to the field and, consequently, offers a nice example on how these topics could be considered in other biomimetic systems. This review is intended to present a selection of some of the essential design principles that underlie the singular microstructure of major ampullate gland silk, as well as to show how the interplay between them leads to the outstanding tensile behavior of spider silk. Following this rationale, the mechanical behavior of the material is analyzed in detail and connected with its main microstructural features, specifically with those derived from the semicrystalline organization of the fibers. Establishing the relationship between mechanical properties and microstructure in spider silk not only offers a vivid image of the paths explored by nature in the search for high performance materials, but is also a valuable guide for the development of new artificial fibers inspired in their natural counterparts.     

Spinnenseidenproteine: Grundlage für neue Materialien

Spider silk is a biomaterial with extraordinary properties. It is extremely tough and at the same time highly elastic – a combination not found in other polymers. Due to its outstanding potential, spider silk has long been desired as a material for technical applications. This review highlights recent developments in the field of spider silk technology, insights into silk structure, and the natural silk spinning process. Due to the recent progress, spider silk products might be available in the near future, reflecting a new generation of environmentally friendly polymer products.