Silk I structure formation through silk fibroin self-assembly

Regenerated silk fibroin films are normally produced by increasing the Silk II structure (β-sheet content). In the present study, silk fibroin films were prepared by controlling the environmental temperature and humidity, resulting in the formation of silk films with a predominant Silk I structure instead of Silk II structure. Wide angle X-ray diffraction indicated that when the relative humidity was 55%, the silk films prepared were mainly composed of Silk I structure, whereas silk films formed on other relative humidity had a higher Silk II structure. Fourier transform infrared analysis (FTIR) results also conformed that the secondary structure of silk fibroin can be controlled by changing the humidity of the films formed process. Thermal analysis results revealed Silk I structure was a stable crystal, and the degradation peak increased to 320°C, indicating a greater thermal stability of these films formed under the 55% relative humidity conditions. Atomic force microscopy (AFM) results depicted silk fibroin in the fresh solution had many nanospheres existing with 20–50 nm diameters and mainly maintained a random coil structure without specific nanostructures. At the same time, it also illustrated the self-assembly process of silk fibroin in the aqueous solution without any human intervention. In addition, this present study also provided additional support for self-assembly mechanism of silk fibroin films formation. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

蚕丝蛋白水解工艺及作为化妆品添加剂的应用研究

蚕丝蛋白是一种新型化妆品添加剂,含有多种氨基酸和蛋白质,无毒、副作用,具有很广泛的应用价值。研究了蚕丝水解液的制备工艺及水解过程中pH、温度、反应时间对水解程度的影响。结果表明,pH越高,蚕丝蛋白水解程度越大,收率越高。较高的温度可使蚕丝蛋白水解速度加快,但水解液颜色较深,较低的温度,水解速度较慢。反应时间越长,蚕丝蛋白水解程度越大。并介绍蚕丝水解液在化妆品中的添加方法及如何解决试验过程中存在的实际问题。     

Physical properties and structure of silk: 4. Spherulites grown from aqueous solution of silk fibroin

Spherulite formation in silk fibroin films cast from aqueous solution has been studied for crystallization conditions such as drying temperature, drying rate and pretreatment (freezing). Negatively birefringent spherulites in the α-form are observed in films cast between 0° and 40°C, and with a high drying rate at 20°C; positive β-form spherulites appear at higher temperatures up to 80°C and with a low drying rate at 20°C. Positive β-form spherulites are also obtained by freezing fibroin solution at ?2° to ?18°C and then drying at 20°C. It is found that positive β-form spherulites grow at 20°C on the surface of well-oriented β-form silk fibroin filaments (degummed silk) immersed in fibroin solution.     

Self‐Expansion Behavior of Silk Fibroin Film

Summary: Silk fibroin cast film was prepared using a ternary solvent system of CaCl₂/CH₃CH₂OH/H₂O (1/2/8 in mole ratio). A drying temperature at casting influenced crystal structure of fibroin. When a drying temperature was set lower than 9 °C, the cast film became amorphous. When a drying temperature was set higher than 40 °C, a fibroin film of silk‐II structure was obtained. In order to produce a fibroin film of silk‐I structure, a preferable temperature range was from 20 to 26 °C. The crystal transformation from random coil structure into silk‐I could be made through exposure of an amorphous film to water vapor. As for the crystal transformation from silk‐I into silk‐II, the treatment with a glycerin solution was effective. In the course of the treatment a film showed self‐thinning and self‐expanding. The expansion ratio exceeded 40% at maximum. The film produced accompanying self‐expansion was ductile in nature.

The apparent self‐expansion percentage as a function of initial thickness of the film. The ductility of the film was classified into four stages from the observation of recovery behavior after folding: ?, very soft; ?, soft; ?, middle; ?, hard (see Figure 5 ).     

Biodegradation of Silk Biomaterials

Silk fibroin from the silkworm, Bombyx mori, has excellent properties such as biocompatibility, biodegradation, non-toxicity, adsorption properties, etc. As a kind of ideal biomaterial, silk fibroin has been widely used since it was first utilized for sutures a long time ago. The degradation behavior of silk biomaterials is obviously important for medical applications. This article will focus on silk-based biomaterials and review the degradation behaviors of silk materials.     

丝素蛋白/聚丙烯酸共混膜仿生合成羟基磷灰石

将丝素蛋白(SF)与聚丙烯酸(PAA)共混,制备丝素蛋白/聚丙烯酸(SF/PAA)共混膜;然后将此共混膜进行改性及矿化处理后,放置于(37±0.5)℃人体仿生液中24h,诱导合成丝素蛋白/羟基磷灰石(SF/HA)复合材料.利用傅里叶红外(FTIR)、X-射线衍射(XRD)、环境扫描电镜(ESEM)以及X射线能谱(EDX...     

Molecular weight and secondary structure change in eri silk during alkali degumming and powdering

Changes in molecular weight and secondary structure of eri silk during alkali degumming and silk powdering were studied. An increase in silk degumming intensity, through increased alkali concentration, treatment temperature, and time, reduced the fibroin molecular weight and, therefore, the fiber tenacity, but at the same time, increased the β‐sheet fraction. These changes reduced the time required to mill the degummed silk fibers into fine powders. Mechanical forces used in wet attritor and air jet milling disturbed intermolecular packing along the direction of side chains, but the conformation remained essentially β‐sheet even in the sub‐micron silk particles. Dry milling drastically reduced molecular weight and changed the conformation of the fibroin chains. The rate of the spontaneous conformation transition in regenerated fibroin solution prepared from fibers and powders increased with a decrease in fibroin molecular weight, affecting the time fibroin solutions could be stored before gelling. Overall, the study showed that molecular weight and secondary structure of silk powders could be manipulated by suitably changing the degumming and milling conditions. It also suggests that wet media milling and air jet milling are better than dry media milling to prepare less degraded and more crystalline ultrafine silk particles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Chemical,Thermal, Time,and Enzymatic Stability of Silk Materials with Silk I Structure

The crystalline structure of silk fibroin Silk I is generally considered to be a metastable structure; however, there is no definite conclusion under what circumstances this crystalline structure is stable or the crystal form will change. In this study, silk fibroin solution was prepared from B. Mori silkworm cocoons, and a combined method of freeze-crystallization and freeze-drying at different temperatures was used to obtain stable Silk I crystalline material and uncrystallized silk material, respectively. Different concentrations of methanol and ethanol were used to soak the two materials with different time periods to investigate the effect of immersion treatments on the crystalline structure of silk fibroin materials. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman scattering spectroscopy (Raman), Scanning electron microscope (SEM), and Thermogravimetric analysis (TGA) were used to characterize the structure of silk fibroin before and after the treatments. The results showed that, after immersion treatments, uncrystallized silk fibroin material with random coil structure was transformed into Silk II crystal structure, while the silk material with dominated Silk I crystal structure showed good long-term stability without obvious transition to Silk II crystal structure. α-chymotrypsin biodegradation study showed that the crystalline structure of silk fibroin Silk I materials is enzymatically degradable with a much lower rate compared to uncrystallized silk materials. The crystalline structure of Silk I materials demonstrate a good long-term stability, endurance to alcohol sterilization without structural changes, and can be applied to many emerging fields, such as biomedical materials, sustainable materials, and biosensors.     

再生丝素蛋白/羟基磷灰石多孔复合材料的制备

再生丝素蛋白具有良好的生物相容性,羟基磷灰石同时还具有成骨诱导性。通过将再生丝素蛋白制备形成丝素蛋白多孔材料,并在37℃下将其浸渍于模拟体液中可以制备再生丝素蛋白/羟基磷灰石多孔复合材料。扫描电镜研究发现在再生丝素蛋白多孔材料的孔隙中羟基磷灰石由针状晶体聚集而成,红外光谱和XRD等表征表明复合材料中羟基磷灰石以羰基取代的羟基磷灰石存在。制备的再生丝素蛋白/羟基磷灰石多孔材料有望作为骨组织修复材料使用。     

Study on porous silk fibroin materials. I. Fine structure of freeze dried silk fibroin

Silk fibroin solution was prepared by dissolving the silk fibroin in triad solvent CaCl₂ · CH₃CH₂OH · H₂O. In this article we tested and analyzed the state of frozen silk fibroin solution and fine structure of freeze dried porous silk fibroin materials. The results indicated that the glass transition temperature of frozen silk fibroin solution ranges from −34 to −20°C, and the initial melting temperature of ice in frozen solution is about −8.5°C. When porous silk fibroin materials are prepared by means of freeze drying, if freezing temperature is below −20°C, the structure of silk fibroin is mainly amorphous with a little silk II crystal structure, and if freezing temperature is above −20°C, quite a lot of silk I crystal structure forms. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2185–2191, 2001     

Silk fibroin/cellulose blend films: Preparation,structure, and physical properties

This article deals with the preparation and characterization of silk fibroin (Bombyx mori)/cellulose blend films. Following dissolution with a metal complex solution, the average molecular weight of silk fibroin slightly decreased. While cellulose was almost unaffected. After coagulation and washing, transparent films were obtained by blending fibroin and cellulose in all proportions. The crystalline structures of regenerated fibroin and cellulose were β-form and cellulose II, respectively, as shown by the characteristic x-ray diffraction profiles. Density values increased with cellulose content, though less than expected from a pure additive behavior. Moisture regain increased following the addition of a small amount of cellulose to silk fibroin. The mechanical properties showed that both strength and elongation at break of silk fibroin films were improved by blending with cellulose. IR spectra exhibited changes in the skeletal frequences of silk fibroin, suggesting the occurrence of intermolecular interactions between fibroin and cellulose through hydrogen bond formation. © 1995 John Wiley & Sons, Inc.     

再生蚕丝蛋白纤维的染色性能研究

主要研究染料种类、染料质量分数、氯化钠质量浓度、染色时间、染色温度等5个因素对再生蚕丝蛋白纤维上染率的影响,分析了再生蚕丝蛋白纤维的染色性能.结果表明:对纤维素纤维染色性能较好的染料对再生蚕丝蛋白纤维也有很好的染色性能.运用直接染料对再生蚕丝蛋白纤维进行染色,得到的最佳工艺为:染料质量分数1％ (omf)、氯化钠质量浓度12 g/L、染色温度85℃、染色时间50 min.     

棉织物丝素/TiO_2生态功能整理

用丝素蛋白整理棉织物,研究丝素蛋白降解时间及浓度对整理后棉织物性能的影响,确定最佳的丝素降解时间和浓度。在此基础上与TiO2复配,研究整理剂中TiO2含量对棉织物性能和结构的影响。结果表明:最佳丝素蛋白降解时间为120min,丝素浓度(质量分数)为1.63%;此时将丝素与TiO2复配,当TiO2质量分数为0.35%时,可使织物折皱回复角比纯丝素整理提高8.68%,紫外防护系数达到42.9,抗紫外性能达到二级。X射线衍射分析表明,丝素蛋白整理可降低棉纤维的结晶度,并使棉纤维由纤维素Ⅰ向纤维素Ⅱ转变,而TiO2整理可提高棉纤维的结晶度。     

废蚕丝中丝素蛋白的琥珀酰化改性研究

文章研究采用琥珀酰酐对废蚕丝丝素蛋白进行化学改性,研究丝素蛋白浓度、琥珀酰酐用量、反应温度、反应时间对丝素蛋白琥珀酰化程度的影响。通过正交实验确定丝素蛋白琥珀酰化的适宜条件为:丝素蛋白浓度2%、琥珀酰酐用量15%、温度40℃、反应时间30 min。丝素蛋白经琥珀酰化修饰后,起泡特性与乳化特性与原来相比均有不同程度的改善。     

腐植酸作柞蚕丝漂白稳定剂的效果观察

柞蚕丝用双氧水漂白时，漂液中必须加入一定量的稳定剂，以控制双氧水分解率，使其均匀有效地分解，使织物避免遭受剧烈损伤。选用腐植酸作双氧水漂白稳定剂漂白柞蚕丝，结果发现，丝质柔软光滑，无锅垢产生，具有经济适用价值。     

A new method to prepare porous silk fibroin membranes suitable for tissue scaffolding applications

A new method to prepare porous silk fibroin (SF) membranes without dialysis is proposed. Silk fibers were degummed to remove sericin and the resultant fibroin was dissolved in a CaCl₂‐CH₃CH₂OH‐H₂O ternary solvent. Rather than undergoing dialysis, a fibroin salty solution was diluted in water and then submitted to a mechanical agitation that led to a phase separation through foam formation on the solution surface. This foam was continually collected and then compacted between plates to remove the excess of water. The membranes presented large pores with diameters of greater than 100 μm (as shown by scanning electron microscopy ‐ SEM), porosity of 68% and water content of 91% w/w. X‐ray diffraction (XRD) and infrared spectroscopy (FTIR‐ATR) indicated that the membranes present SF in a β‐sheet structure even before the ethanol treatment. A typical elastic deformation profile and degradation under temperature were observed using calorimetric analysis (DSC), thermal gravimetric analysis (TGA) and mechanical tests. As indicated by the in vitro cytotoxicity tests, these membranes present potential for use as scaffolds. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Self-assembled silk fibroin particles: Tunable size and appearance

Silk fibroin had various applications especially outstanding for drug delivery due to its protein component, biocompatibility and biodegradability. In this paper, silk fibroin particles were prepared via self-assembly. Their sizes and appearances could be modified by adjusting of volume ratios among poly vinyl alcohol (PVA), silk fibroin and ethanol. Regular silk particles were formed in PVA solution when the volume ratio of silk to ethanol ranged from 2 to 20. Preparation pathways could be concluded as 1) mixing ethanol with silk fibroin solution, 2) blending the silk fibroin/ethanol solution with PVA, 3) freezing the ternary solution for 48 h and collection of silk fibroin particles via thaw and centrifugation. Silk particles with various appearances were also obtained by addition of concentrated PVA solution. Silk particles reported have potential as drug delivery carriers in a variety of biomedical applications.     

硫酸法水解家蚕丝及其光谱性质研究

文章用一定质量分数的硫酸溶液对家蚕丝进行水解,并利用傅里叶红外光谱仪、紫外可见分光光度计、X-射线衍射仪和扫描电镜等先进测试方法对硫酸水解家蚕丝制取丝素肽进行测试,分析家蚕丝丝素多肽的结构,为以后在食品、药品、化妆品等领域的应用提供理论数据。     

丝素蛋白/聚氨酯涂层PBT过滤材料的研究

以丝素蛋白/聚氨酯共混水溶液为涂层改性剂,对熔喷非织造过滤材料进行表面涂层改性。结果表明,丝素蛋白/聚氨酯涂层具有较好的热水稳定性,涂层改性后PBT熔喷非织造材料的表面润湿性能得以提高、其平均孔径变小、孔径中小于5μm的孔径比率大大增加。因此聚氨酯/丝素蛋白涂层改性提高了PBT熔喷非织造材料的白细胞过滤性能,可以作为新的血液过滤材料应用于血液过滤领域。     

Study on porous silk fibroin materials. II. Preparation and characteristics of spongy porous silk fibroin materials

Porous silk fibroin materials, with average pore size 10 ∼ 300 μm, pore density 1 ∼ 2000/mm², and porosity 35 ∼ 70%, were prepared by freeze drying aqueous solution of silk fibroin obtained by dissolving silk fibroin in ternary solvent CaCl₂ · CH₃CH₂OH · H₂O. Pore size distribution of such materials mostly accorded with logarithmic normal distribution. It is possible to control the aforementioned structural parameters and the physical properties of moisture permeability, compressibility, strength, elongation, etc., by adjusting freezing temperature and concentration of silk fibroin solution. Above glass transition zone (−34 ∼ −20°C) of silk fibroin, the freezing temperature has more significant effect on the structure and properties of porous silk fibroin materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2192–2199, 2001