Miscibility and biodegradability of silk fibroin/carboxymethyl chitin blend films

Blend films of silk fibroin and carboxymethyl chitin were prepared by solution casting using water as a cosolvent. The blend films were subjected to post-treatment with an aqueous methanol solution to induce beta-sheet formation of silk fibroin. The miscibility of the blend films both before and after methanol treatments was investigated in terms of chemical interactions, morphologies, thermal properties, and crystal structures by using FTIR spectroscopy, SEM, DSC, and XRD. The results indicate that the blend between silk fibroin and CM-chitin was semi-miscible because only the amorphous parts of the polymers were compatible with each other. The enzymatic degradation showed that the incorporation of CM-chitin enhanced biodegradability and swelling ability of silk fibroin.     

天然蚕丝丝素蛋白的乳化活性

采用不同油相制备了系列丝素蛋白乳液, 研究了丝素蛋白浓度、 油相体积分数和油相极性对丝素蛋白的乳化活性指数、 丝素蛋白乳液的稳定性和类型及乳液液滴的微观形态、 粒径与zeta电位的影响, 探讨了丝素蛋白的乳化活性和乳液稳定机制. 结果表明, 丝素蛋白具有两亲性和表面活性, 可在油水界面富集并形成稳定的黏弹性保护膜; 丝素蛋白的乳化活性随其浓度的增大而减小, 随油相体积分数的增大而增大; 丝素蛋白浓度和油相体积分数的增加可提高稳定乳液体积分数.     

Patterned silk films cast from ionic liquid solubilized fibroin as scaffolds for cell growth

Silk is an attractive biomaterial for use in tissue engineering applications because of its slow degradation, excellent mechanical properties, and biocompatibility. In this report, we demonstrate a simple method to cast patterned films directly from silk fibroin dissolved in an ionic liquid. The films cast from the silk ionic liquid solution were found to support normal cell proliferation and differentiation. The versatility of the silk ionic liquid solutions and the ability to process large amounts of silk into materials with controlled surface topography directly from the dissolved silk ionic liquid solution could enhance the desirability of biomaterials such as silk for a variety of applications.     

纳米TiO_2改性蚕丝丝素蛋白膜的研究

用溶胶凝胶法制备纳米TiO2改性再生蚕丝丝素蛋白膜.该丝素膜机械强度提高,在水中溶失率下降.UV、AFM、SEM测试的结果表明,丝素中纳米TiO2粒径约为80 nm,纳米粒子在丝素膜中分布均匀;XRD、FTIR测试结果表明,纳米TiO2的加入,可使改性丝素膜的结晶结构从SilkⅠ向SilkⅡ转化,其结晶度也随之提高;TGA测试表明改性丝素膜的热转变温度比纯丝素膜有所改变.     

THE PREPARATION AND STUDY ON THE NANO-TiO2/SILK FIBROIN COMPOSITE FILMS BY THE SOL-GEL METHOD

Based on the sol-gel technique using butyl titanate as oxide precursor, the regenerated SF (silk fibroin)/nano-TiO2 composite films were synthesized. Different amounts of butyl titanate to SF were used to verify this effect on the characteristics of the formed materials. Samples were characterized by thermogravimetric analysis, X-ray diffractometry, UV, AFM and FT-IR spectroscopy.The experimental results reveal that, compared to the pure silk fibroin films, the mechanical strength of these regenerated SF/nano-TiO2 composite films were increased and the dissolubility in water of SF/nano-TiO2 composite films in aqueous solution were decreased. The diameter of nano-TiO2 particle films was about 80nm through UV and AFM. The nano-TiO2 particles were well dispersed in the regenerated silk fibroin. It was found that the crystal structures of the composite films were transited from typical Silk Ⅰ to typical Silk Ⅱ by the XRD and FTIR. Furthermore, the crystallinity of the composite films was obviously improved. Through the TGA, it was demonstrated that the heat transition temperature of composite films was also enhanced.     

THE PREPARATION AND STUDY ON THE NANO-TiO_2/SILK FIBROIN COMPOSITE FILMS BY THE SOL-GEL METHOD

1. INTRODUCTIONSilk is a well described natural fiber produced by the silkworm, B. mori, which has been used traditionally in the form of thread in textiles for thousands of years. This silk contains a fibrous protein that forms the thread core and glueli…     

溶胶-凝胶法制备纳米TiO2/丝素复合膜及结构性能研究

用溶胶凝胶法制备不同比例纳米TiO₂改性再生蚕丝丝素蛋白复合膜. UV和AFM测试结果表明, 该丝素膜中纳米TiO₂均匀分散在丝素中, TiO₂粒径约为80 nm; 同时该丝素膜的结构和热性能用FTIR, XRD, EDS, TGA和DTG进行表征. XRD测试结果表明, 随着纳米TiO₂的加入, 复合丝素膜的结晶结构从Silk I向Silk II转化, 但当纳米TiO₂的加入超过一定量时, 又破坏复合丝素膜的结晶结构; FTIR和EDS测试结果表明, TiO₂与丝素形成较好的键合; TGA和DTG测试表明复合丝素膜的热转变温度相比于纯丝素膜有所提高.     

甲醇-水混合溶剂后处理制备丝素蛋白膜及其药物释放研究

采用溶液浇注法制备丝素蛋白薄膜, 应用傅里叶红外光谱(FTIR)和X 射线衍射(XRD)研究了浓度不同的甲醇-水混合溶剂处理后丝素蛋白薄膜的结构变化, 并以罗丹明B 为模型药物与丝素蛋白构建药物缓释体系, 考察了丝素蛋白膜的结晶结构对药物释放动力学的影响. 结果显示, 在甲醇体积比浓度Φ_MeOH＝50%～90%的范围内, 丝素蛋白材料中以β-折叠为主的silk Ⅱ 结晶含量随着混合溶剂中甲醇浓度的增加而先增加后下降, 在Φ_MeOH＝80%附近出现最大值. 罗丹明B 从丝素蛋白膜的释放属于Fickian 扩散机理, 其扩散指数n 随着丝素蛋白膜中β-折叠含量的增加而增加, silk Ⅱ结晶是丝素蛋白材料药物释放的天然调节器.     

Folding and assembly of fibroin driven by an AC electric field: effects on film properties

Silk fibroin from Bombyx mori is a high-molecular-weight protein, largely employed in the biomaterials field. Several parameters can affect the folding and assembly of fibroin heavy and light chains. The present work has shown that anisotropic and water-stable films are produced when fibroin solution is cast under an alternating electric field (AC). The treatment can affect the mechanical, thermal and surface properties of fibroin films. These effects have been related to the alignment of molecular dipoles and the formation of oriented supramolecular assemblies. Cell response is affected by this novel processing: MRC5 fibroblasts, cultured on anisotropic fibroin films, preferentially spread parallel to the field direction 6 h after seeding. [Figure: see text].     

Fabrication of silk fibroin film with properties of thermal insulation and temperature monitoring

Silk fibroin exhibits excellent mechanical properties, good biocompatibility, and biodegradability combined with benign processing conditions, attracting considerable research interest for the application as biomedical materials. Among the diverse forms of sponges, hydrogels, films, and mats manufactured from silk fibroin, films are especially appealing due to the high water and oxygen permeability, good cell attachment, and low immunogenicity. Fabrication of silk fibroin films with novel properties has been successfully developed simply by incorporating various functional components into it. In the present study, the properties of thermal insulation and temperature monitoring for the silk fibroin film are demonstrated for the first time through the incorporation of thermochromic microcapsules within it. Moreover, the silk fibroin film is also endowed with improved mechanical properties in terms of tension strength and elongation at break because of the reinforcing effect of thermochromic microcapsules. The silk fibroin film fabricated with novel features in this study can be a good candidate for the application of wound dressings, tissue engineering scaffolds, and bio‐related devices in the future. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1846–1852     

Effect of Silk Fibroin Reinforcement on the Properties of Potato Starch-Polyvinyl Alcohol Blend Films

Starch and polyvinyl alcohol composite films, reinforced with raw and methylmethacrylate-grafted silk fibroin particles, were prepared by the solution-casting method on leveled plates. Silk fibroin was used as reinforcement for starch and polyvinyl alcohol (St/PVA) blends in order to improve their mechanical and water-resistance properties. The composites were plasticized with citric acid and cross-linked with gluteraldehyde. The reinforced films showed an increase in tensile strength with decrease in elongation at break. The optimized samples were characterized by scanning electron microscopy and were studied for their antibacterial properties. The biodegradable behavior was studied by the soil burial method.     

Fibroin nanofibers production by electrospinning method

Silk fibroin, which has many characteristic properties such as low inflammation reaction, biodegradation, suppleness, good antithrombogenic details, biocompatibility and high tensile strength is a very good candidate for biomedical applications. Electrospinning procures high surface area, porous, nanofiber dimension fiber generation, which is a plain method. An experimental study was carried out to produce nanofiber structure from silk fibroin by electrospinning and the electrospinning parameters for the spinning of uniform, continuous and silk fibroin fibers were optimized. As a result, the effect of variables of concentration, distance and applied voltage on the strength, thickness, surface structure, fiber diameter of nanomaterial was investigated. Then, in vitro cell viability of the silk fibroin mat was analyzed. It was seen that the strength, mat thickness, and fiber diameter increased with solution concentration rise. It was found that the values of the fiber diameter and tensile strength decreased with increasing distance. It was determined that the effect of distance varies depending on the concentration in the mat thicknesses. The tensile strength was affected inversely proportional the applied voltage rises and distance. It was found that the fiber diameter values decreased together with increasing applied voltage. At cell viability of silk fibroin mat was occurred high cell viability after 24 h, but it was obtained low cell viability at the 48th h.     

Physical and chemical properties of tussah silk fibroin films

Physical and chemical structure, as well as thermal behavior of solution-cast regenerated films, prepared from tussah (Antheraea pernyi) silk fibroin, were compared with those of solution-cast native films, in order to ascertain whether treatment (degumming, dissolution) used for preparation affected their properties. Regenerated fibroin films exhibited a higher thermal stability than native ones, as shown by differential scanning calorimetry, thermomechanical analysis, and dynamic mechanical behavior. Glass transition temperature and other relevant thermal transitions of the regenerated silk specimen shifted to higher temperatures compared with those of native specimen. Molecular conformation and crystalline structure did not show significant differences between the two kinds of silk films. Amino acid composition and molecular weight, however, distribution changed markedly after dissolving tussah silk fibroin fiber in concentrated LiSCN in polypeptide size was the main features for the regenerated silk fibroin. © 1994 John Wiley & Sons, Inc.     

pH值对丝素蛋白构象转变的影响

模仿家蚕吐丝过程中伴随丝素蛋白自然脱水的纤维化过程,研究了再生丝素蛋白在各种pH值的磷酸盐缓冲溶液体系中自然干燥脱水成膜后的构象转变.利用激光拉曼散射光谱及其二维相关光谱,定性分析了丝素蛋白酰胺区(1600～1700cm^-1)散射峰的相关组成及结构.在此基础上,利用¹³CCP-MAS固体核磁共振谱对丝素蛋白丙氨酸C_β峰(δ14.5～22)进行了解析拟合.从而确定了体系中与Silk及Silk构象相关的组成含量与pH值的关系.结果表明,pH=5.2的酸性溶液有利于蚕丝丝素蛋白从Silk向Silk构象转变,而中性与碱性溶液(pH=6.9和8.0)则对丝素蛋白的构象转变影响甚小.     

Green Process to Prepare Silk Fibroin/Gelatin Biomaterial Scaffolds

A new all‐aqueous and green process is described to form three‐dimensional porous silk fibroin matrices with control of structural and morphological features. Silk‐based scaffolds are prepared using lyophilization. Gelatin is added to the aqueous silk fibroin solution to change the silk fibroin conformation and silk fibroin–water interactions through adjusting the hydrophilic interactions in silk fibroin–gelatin–water systems to restrain the formation of separate sheet like structures in the material, resulting in a more homogenous structure. Water annealing is used to generate insolubility in the silk fibroin–gelatin scaffold system, thereby avoiding the use of organic solvents such as methanol to lock in the β‐sheet structure. The adjusting of the concentration of gelatin, as well as the concentration of silk fibroin, leads to control of morphological and functional properties of the scaffolds. The scaffolds were homogeneous in terms of interconnected pores, with pore sizes ranging from 100 to 600 µm, depending on the concentration of silk fibroin used in the process. At the same time, the morphology of the scaffolds changed from lamellar sheets to porous structures based on the increase in gelatin content. Compared with salt‐leaching aqueous‐derived scaffolds and hexafluoroisopropanol (HFIP)‐derived scaffolds, these freeze‐dried scaffolds had a lower content of β‐sheet, resulting in more hydrophilic features. Most of gelatin was entrapped in the silk fibroin–gelatin scaffolds, without the burst release in PBS solution. During in vitro cell culture, these silk fibroin–gelatin scaffolds had improved cell‐compatibility than salt‐leaching silk fibroin scaffolds. This new process provides useful silk fibroin‐based scaffold systems for use in tissue engineering. Furthermore, the whole process is green, including all‐aqueous, room temperature and pressure, and without the use of toxic chemicals or solvents, offering new ways to load bioactive drugs or growth factors into the process.

     

Biomaterial coatings by stepwise deposition of silk fibroin

A completely aqueous, stepwise deposition process with Bombyx mori silk fibroin for the assembly of nanoscale thin film coatings is reported the first time. The focus of this work was to develop an understanding of the control of this deposition process and to characterize the films formed from a physicochemical perspective. The deposition process was monitored by UV spectrophotometry and research quartz crystal microbalance. Both absorbance and film thickness correlated linearly with the number of silk fibroin layers deposited, analogous to multilayered materials fabricated from conventional polyelectrolytes. The polymer adsorption process was stable and reproducible, with control of a single layer thickness ranging from a few to tens of nanometers, determined by the concentrations of silk fibroin, salt concentration in the dipping solution, and method of rinsing. The driving force for the assembly of silk fibroin onto the substrate was primarily hydrophobic interactions, while some electrostatic interactions were also involved. The difference with this approach from traditional polyelectrolyte layer-by-layer techniques is that an intervening drying step is used to control the structure and stability of the self-assembled silk fibroin. The assembled films were stable under physiological conditions and supported human bone marrow stem cell adhesion, growth, and differentiation. This approach offers new options to engineer biomaterial coatings as well as bulk materials with control of both interfacial properties conducive to specific cellular or tissue responses and the potential to entrap and deliver labile molecules or other components due to the all-aqueous process described.     

丝素改性聚乳酸-羟基乙酸共聚物多孔微球作为牙龈间充质干细胞递送载体的研究

利用复乳-溶剂挥发法合成适合细胞三维培养的聚乳酸-羟基乙酸共聚物(PLGA)多孔微球, 并对其表面进行丝素改性, 利用扫描电子显微镜、 能谱、 红外光谱和X射线衍射等对改性前后PLGA多孔微球的理化特性进行表征. 原代培养人牙龈间充质干细胞并进行成骨(茜素红染色)成脂(油红O染色)分化鉴定. 通过负压混悬法将牙龈干细胞负载于丝素改性的PLGA多孔微球上进行5-乙炔基-2'-脱氧尿嘧啶核苷(EdU)细胞增殖及成骨分化研究. 结果表明, 原代培养的牙龈干细胞具有多向分化潜能, 负载在丝素改性的PLGA多孔微球上的细胞有利于细胞增殖. 丝素改性的PLGA多孔微球是良好的细胞递送载体, 为进一步修复牙槽骨缺损提供了科学依据.     

Processing of β-Glucosidase–Silk Fibroin Nanoparticle Bioconjugates and Their Characteristics

Silk fibroin derived from Bombyx mori is a biomacromolecular protein with excellent biocompatibility. The aim of this work was to develop silk fibroin nanoparticles (SFNs) derived from the fibrous protein, which is a novel vector for enzyme modification in food processing. Silk fibroin was dissolved in highly concentrated CaCl₂ and subjected to lengthy desalting in water. The resulting liquid silk, which contained water-soluble polypeptides with molecular mass ranging from 10 to 200 kDa, and β-glucosidase were added rapidly into acetone. The β-glucosidase molecules were embedded into silk fibroin nanoparticles, forming β-glucosidase–silk fibroin nanoparticles (βG–SFNs) with a diameter of 50–150 nm. The enzyme activity of the βG–SFN bioconjugates was determined with p-nitrophenyl-β-d-glucoside as the substrate, and the optimum conditions for the preparation of βG–SFNs were investigated. The enzyme activity recovery of βG–SFNs was 59.2 % compared to the free enzyme (specific activity was 1 U mg^-1). The kinetic parameters of the βG–SFNs and the free β-glucosidase were the same. The βG–SFNs had good operational stability and could be used repeatedly. These results confirmed that silk protein nanoparticles were good carriers as bioconjugates for the modification of enzymes with potential value for research and development. The method used in this study has potential applications in food processing and the production of flavour agents.     

Structural changes of silk fibroin membranes induced by immersion in methanol aqueous solutions

Structural changes of native and regenerated silk fibroin membranes were induced by immersion in water-methanol solutions and examined as a function of immersion time and methanol concentration. X-ray diffractometry and infrared spectroscopy data showed that transition from random coil to β-sheet structure occurred favorably when both native and regenerated silk fibroin membranes were immersed in water-methanol solutions, regardless of the different immersion time. Only native silk membrane, treated for 2 min with pure methanol, maintained its original amorphous structure, as demonstrated by differential scanning calorimetric (DSC) curves. The degree of displacement, measured by thermomechanical analysis (TMA), was much greater for regenerated than for native silk fibroin membranes. SDS-PAGE pattern showed that native silk fibroin has a molecular weight of 350, while the regenerated sample is formed by a large number of polypeptides in the range of 200-50 KD. The amount of acidic and basic amino acids decreased slightly in regenerated silk fibroin. Physical properties of silk membranes treated with water-methanol solutions are discussed in terms of membrane structure, treatment conditions, and chemical structure of starting material. © 1994 John Wiley & Sons, Inc.     

Stromal Vascular Fraction Loaded Silk Fibroin Mats Effectively Support the Survival of Diabetic Mice after Pancreatic Islet Transplantation

The aim of this study is to assess whether stromal vascular fraction (SVF)‐soaked silk fibroin nonwoven mats (silk‐SVF) can preserve the functionality of encapsulated pancreatic endocrine cells (alginate‐PECs) after transplantation in the subcutaneous tissue of diabetic mice. Silk scaffolds are selected to create an effective 3D microenvironment for SVF delivery in the subcutaneous tissue before diabetes induction: silk‐SVF is subcutaneously implanted in the dorsal area of five healthy animals; after 15 d, mice are treated with streptozotocin to induce diabetes and then alginate‐PECs are implanted on the silk‐SVF. All animals appear in good health, increasing weight during time, and among them, one presents euglycemia until the end of experiments. On the contrary, when PECs are simultaneously implanted with SVF after diabetes induction, mice are euthanized due to suffering. This work clearly demonstrates that silk‐SVF creates a functional niche in subcutaneous tissue and preserves endocrine cell survival and engraftment.