Nanopatterned silk fibroin films with high transparency and high haze for optical applications

Simultaneous high transparency and high haze are necessary for high-efficiency optical, photonic, and optoelectronic applications. However, a typical highly transparent film lacks high optical haze or vice versa. Here, we report a silk fibroin-based optical film that exhibits both ultrahigh optical transparency (>93%) and ultrahigh optical transmission haze (>65%). Also, in combination with the soft lithography method, different nanostructured silk fibroin films are presented and their optical properties are characterized as well. To demonstrate its exceptional performance in both high transmission and high optical haze, we combine the silk fibroin with the silicon photodiode and show that the efficiency can be increased by 6.96% with the silk fibroin film without patterns and 14.9% with the nanopatterned silk fibroin film. Silk provides excellent mechanical, optical, and electrical properties, and the reported high-performance silk fibroin can enable the development of next-generation biocompatible eco-friendly flexible electronic and optical devices.

Nanopatterned silk fibroin-based optical films exhibit both ultrahigh optical transparency and ultrahigh optical transmission haze.     

The mineralization,drug release and in vivo bone defect repair properties of calcium phosphates/PLA modified tantalum scaffolds

Calcium phosphate based biomaterials have been widely studied in biomedical areas. Herein, amorphous calcium phosphate (ACP) nanospheres and hydroxyapatite (HA) nanorods were separately prepared and used for coating tantalum (Ta) scaffolds with a polymer of polylactide (PLA). We have found that different crystal phases of calcium phosphate coated on Ta scaffolds displayed different effects on the surface morphologies, mineralization and bovine serum albumin (BSA) release. The ACP-PLA and HA-PLA coated on Ta scaffold were more favorable for in vitro mineralization than bare and PLA coated Ta scaffolds, and resulted in a highly hydrophilic surfaces. Meanwhile, the osteoblast-like cells (MG63) showed favorable properties of adhesion and spreading on both ACP-PLA and HA-PLA coated Ta scaffolds. The ACP-PLA and HA-PLA coated Ta scaffolds showed a high biocompatibility and potential applications for in vivo bone defect repair.

Calcium phosphate modified tantalum scaffolds displayed high performance on mineralization, sustained drug release and in vivo bone defect repair.     

Silk fibroins in multiscale dimensions for diverse applications

Silk biomaterials in different forms such as particles, coatings and their assemblies, represent unique type of materials in multiple scales and dimensions. Herein, we provide an overview of multi-scale silk fibroin materials including silk particles, silk coatings and silk assemblies, each of which represents a unique type of material with wide range of applications. They feature tunable structures and mechanical properties with excellent biocompatibility, which are essentially required for various biomedical and drug delivery applications. The review focuses on bringing a new perspective on the utilization of regenerated silk fibroins in modern biomedicine by beginning with the fabrication of silk in multiscale dimensions and their state-of-the-art applications in various biomedical and bioelectronic fields. It covers the fundamentals of processing silk fibroins in multi-dimensions (sizes and shapes) with a specific emphasis on its structural tunability at various length scales (nano–micro) by using the latest fabrication methods/mechanisms and advanced fabrication technologies, followed by their recent applications in diverse fields of biomedicine.

Silk biomaterials in different forms such as particles, coatings and their assemblies, represent unique type of materials in multiple scales and dimensions.     

A silk fibroin based green nano-filter for air filtration

Fibrous air filters fabricated by electrospinning have proved to be an effective approach among the various strategies for PM2.5 removal. However, in the electrospinning process, the large amounts of toxic organic solvents usually evaporate into the atmosphere and disposing of these used polymer-based air filters would leave further pollution in the environment. Here, we report on the fabrication of a silk fibroin based nanofiber air filter with robust filtration performance via a green electrospinning process. Silk worm cocoons were degummed and dialyzed against water to form the silk fibroin solution and then the silk fibroin nanofiber membranes were fabricated by electrospinning with the help of polyethylene oxide. Moreover, special attention was paid to the morphological evolution of the pollutants captured by the nanofiber nets during the filtration process. It was discovered that the inherent properties of silk fibroin play a key role in improving the filtration performance. Benefiting from the richness of functional groups, the resultant silk fibroin fibrous membranes exhibited a high filtration efficiency of 99.99% with a relatively low air resistance of only 75 Pa, leading to an obvious higher quality factor. Due to the biodegradability of silk fibroin, the membranes are disposable after use. We believe that the methodology and results presented here will not only provide a novel perspective for air filtration, but also pave the way for producing a safe and clean air filtration system.

This paper reports the fabrication of a silk fibroin nanofiber air filter via a green electrospinning method.     

丝素蛋白对磷酸钙骨水泥抗压强度及注射性的影响术

背景:高分子材料对磷酸钙骨水泥力学性能的增强作用已得到了一定的证实,但往往会同时减弱复合材料的注射性能,影响复合材料的临床应用.目的:将丝素蛋白加入磷酸钙骨水泥固相粉末中,观察其对骨水泥抗压强度和注射性的影响.设计、时间及地点:对照实验,于2007-09/12在苏州大学分析测试中心实验室完成.材料:磷酸钙骨水泥购自上海瑞邦生物材料有限公司,丝素蛋白为苏州大学材料工程学院自行合成.方法:按5,10,15,20,25,30 g/L的丝素蛋白质量比例,用自制的粉末搅拌器将丝素蛋白粉末和骨水泥固相粉末混合均匀,依次设为6个实验组,以单纯磷酸钙骨水泥为对照组,液固比均为0.4 mL/g.主要观察指标:测定丝素蛋白/磷酸钙骨水泥复合材料的抗压强度、注射系数,应用扫描电镜观察试件断裂面的微脱结构特征.结果:随着丝素蛋白质量比例增加,磷酸钙骨水泥的抗压强度呈现先上升后下降的趋势,当丝素蛋白质量比例为1%-2.5%时,抗压强度显著高于对照组(P<0.05).注射系数随着丝素蛋白质量比例增加而逐渐下降,当丝素蛋白质量比例为1.5%-3%时,注射系数显著低于对照组(P<0.05).扫描电镜发现,丝素蛋白呈网状,贯穿于磷酸钙水泥晶体间,并将磷酸钙水泥晶体紧密连接.结论:丝素蛋白能在不明显影响注射操作的情况下,显著提高丝素蛋白/磷酸钙骨水泥复合材料的抗压强度.     

丝素/褐藻多糖硫酸酯复合膜的理化性质

背景:丝素膜α-螺旋的结构是水溶性的而且不稳定,不能直接作为医用材料,具而β-折叠构象更为稳定.目的:利用褐藻多糖硫酸酯导致丝素膜的构象转变来制备β折叠构象的丝素膜,观察膜的理化件质.设计、时间及地点:生物材料复合膜的理化性质观察实验,于2003-11/2006-08在中科院北京化学所、承德石油高等专科学校化学实验中心完成.材料:褐藻多糖硫酸酯,从海带中提取,在承德石油高等专科学校化学实验中心完成,蚕丝购于中国进出口公司.方法:将丝素溶液和褐藻多糖硫酸酯的水溶液按一定比例混合,静置脱泡后,注入聚乙烯模具内,于25℃.相对湿度65%的环境干燥成膜,当褐藻多糖硫酸酯含量≤20%时,成膜性较好.根据复合膜中褐藻多糖硫酸酯和丝素的质量比0∶100、5∶95、10∶90、20∶80、100∶0,将膜分别标记.主要观察指标:采用红外光谱、X射线衍射、热失重分析表征观察制成膜的理化性质.结果:红外光谱、X射线衍射结果表明,由于褐藻多糖硫酸酯的引入,促使了丝素β-折替构象的形成.丝素从无规线团转变为β-折叠构象归结于丝素与褐藻多糖硫酸酯之间存在着氢键的相互作用.热失重分析表明,具有β-折叠结晶结构的丝素复合膜热稳定性要比无定形丝素膜高.结论:利用褐藻多糖硫酸酯导致丝素膜的构象转变来制备β折叠构象的丝素膜,构象的转变可通过红外光谱、X射线衍射证实.具有β-折叠结晶结构的丝素膜的热稳定性要比无定形丝素膜高.     

A novel method to prepare tussah/Bombyx mori silk fibroin-based films

The possibility of using silk fibroin in biomaterials for tissue engineering is a subject of broad interest. In this study, Bombyx mori/tussah silk fibroin (BSF/TSF) blend films were prepared by solution casting using CaCl₂/formic acid as a co-solvent and water as a rinse solvent. The morphology, crystallinity, thermal resistance, mechanical properties and water contact angle of the blend films as well as the biocompatibility were investigated. The BSF/TSF blend films displayed a smooth surface and specific nanostructure in their cross-section, originating from the nanofibril-preservation during fibroin dissolution. The water rinse process induced the formation of a stable β-sheet structure. The BSF film showed superior mechanical properties to the TSF film, and the blending with TSF led to a significant reduction in the strength and elasticity of blend films. However, adding the TSF component could regulate the hydrophilic properties and enhance cell growth on the blend films. The BSF/TSF blend films with specific nanostructure, stable secondary structure, appropriate mechanical properties, and good biocompatibility, are promising candidates for application in regenerative medicine.

A novel method is reported to prepare tussah/Bombyx mori silk fibroin blend films featured transparent, flexible and biocompatible.     

丝素蛋白/透明质酸复合多孔支架材料的表征及细胞相容性

背景:丝素蛋白和透明质酸具备细胞外基质两种主要成分特征,并且有良好的生物相容性。目的:采用冷冻干燥法制备丝素蛋白/透明质酸复合多孔支架,并观察其表征与细胞生物相容性。方法:将丝素蛋白与透明质酸按10:1混合通过冷冻干燥法构建丝素蛋白/透明质酸复合多孔支架并观察其表征。将1×108L-1的第3~5代大鼠骨髓间充质干细胞接种在丝素蛋白/透明质酸复合多孔支架上观察其细胞生物相容性。结果与结论:采用冷冻干燥法可以成功制备丝素蛋白/透明质酸复合多孔支架,与纯丝素蛋白支架相比,复合支架具有更好的多孔三维结构。此外,支架制备过程中不含有毒溶剂,支持骨髓间充质干细胞的黏附铺展与增殖。说明实验制备的丝素蛋白/透明质酸复合支架的成孔性好,具有良好的细胞生物相容性。     

Tailor-made spider-eggcase-silk spheres for efficient lysosomal drug delivery

Spider silks are attractive biopolymers due to their excellent mechanical properties and biomimetic potential. To optimize the electrostatic interaction for lysosomal drug delivery, a spider-eggcase-silk protein was genetically engineered using 5× His Tag with a tailor-made isoelectric point of 4.8. By a facile HFIP-on-oil method, silk spheres were assembled as rapidly as 10 s. After the post-treatment of ethanol, silk spheres were determined with an improved compressive modulus by AFM indentation. Under incubation of silk spheres in a Doxorubicin solution, a maximum of 35% loading and average of 30% loading efficiency were determined. In the cytotoxicity experiment, silk spheres exhibited intrinsic biocompatibility and showed good control of the loaded drug in the neutral PBS solution. Significantly, by 96 h, the accumulative drug release at pH 4.5 was approximately 4.5-fold higher than that at pH 7.4. By conducting the platelet adhesion and hemolysis assay, Doxorubicin-loaded silk spheres exhibited good hemocompatibility. To further demonstrate this release behavior, within 24 h, Doxorubicin-loaded silk spheres were efficiently delivered to lysosomes and then released the payload to the nuclei of Hela cells.

Recombinant spider-eggcase-silk spheres are facilely prepared as drug carriers with a tailor-made isoelectric point specifically for lysosomal delivery.     

Novel non-mulberry silk fibroin nanoparticles with enhanced activity as potential candidate in nanocarrier mediated delivery system

Silk fibroin (SF) is well known for its excellent biocompatible properties facilitating its application in the field of biomedical engineering through different biomaterial fabrications in the recent era. Here in this study, novel nanoparticles from non-mulberry SF of Antheraea assamensis were fabricated, characterized and evaluated for its applicability as nanocarrier. Fabricated nanoparticles were initially compared with prevailing SF nanoparticles from Bombyx mori. Fabricated A. assamensis silk fibroin nanoparticles (AA-SFNps) were found to be lesser in size (80–300 nm in diameter) than B. mori silk fibroin nanoparticles (BM-SFNps) (120–500 nm in diameter). When checked for stability, AA-SFNps were found to be more stable than BM-SFNps in biological media. FTIR and XRD studies revealed persistence of structural properties even after fabrication. TGA and DSC studies showed AA-SFNps to be thermally more stable than BM-SFNps without any cytotoxicity (MTT assay). On loading with model drug Doxorubicin hydrochloride (DOX), AA-SFNps exhibited an encapsulation efficiency of 94.47% with 11.81% loading of the anticancer drug. Cumulative release study revealed highest percentage release of DOX (42.1 ± 0.4%) at pH 5.2 on day 7 in comparison to pH 7.4 and 8.0. Sustained release profile of the DOX loaded AA-SFNps (AA-SFNps-DOX) was clearly reflected and it was found to be highly cytotoxic against triple negative MDA-MB-231 cells in comparison to free DOX at different time points. Overall, this study showed the efficacy of the AA-SFNps as a nanocarrier for future drug delivery applications.

Novel Antheraea assamensis silk fibroin nanoparticles (AA-SFNps) exhibiting enhanced activity as doxorubicin hydrochloride (DOX) loaded nanocarriers for future drug delivery applications.     

Chitosan composite scaffolds for articular cartilage defect repair: a review

Articular cartilage (AC) defects lack the ability to self-repair due to their avascular nature and the declined mitotic ability of mature chondrocytes. To date, cartilage tissue engineering using implanted scaffolds containing cells or growth factors is the most promising defect repair method. Scaffolds for cartilage tissue engineering have been comprehensively researched. As a promising scaffold biomaterial for AC defect repair, the properties of chitosan are summarized in this review. Strategies to composite chitosan with other materials, such as polymers (including collagen, gelatin, alginate, silk fibroin, poly-caprolactone, and poly-lactic acid) and bioceramics (including calcium phosphate, calcium polyphosphate, and hydroxyapatite) are presented. Methods to manufacture three-dimensional porous structures to support cell attachment and nutriment exchange have also been included.

Properties of chitosan/polymer and chitosan/bioceramic composite scaffolds for articular cartilage defect repair are reviewed.     

Biological properties of calcium phosphate biomaterials for bone repair: a review

Bone defects are a common disease threatening the health of many people. Calcium phosphate (CaP) is an ideal bone substitutive material that is widely used for bone repair due to its excellent biological properties including osteoinductivity, osteoconductivity and biodegradability. For this reason, investigation of these properties and the effects of various influencing factors is vital for modulating calcium phosphate during the design process to maximally satisfy clinical requirements. In this study, the latest studies on the biological properties of CaP biomaterials, including hydroxyapatite (HA), tricalcium phosphate (TCP), and biphasic calcium phosphate (BCP), have been summarized. Moreover, recent advances on how these properties are altered by different factors are reviewed. Considering the limited mechanical strength of CaP materials, this study also reviews CaP composites with different materials as improvement measures. Finally, perspectives regarding future developments of CaP materials are also provided.

This article reviews the recent advances and various factors affecting the improvement of the biological properties of calcium phosphate for bone repair.     

Study on the mechanism of laccase-catalyzed polydopamine rapid dyeing and modification of silk

Research on the polymerization of dopamine and its modification on the surface of materials has received extensive attention. In this work, the process of laccase catalyzing the rapid polymerization of dopamine and in situ dyeing of silk fabric were studied. The results showed that laccase catalyzed dyeing for 3 h under acidic conditions could achieve the dyeing effect of 24 h under an alkaline environment, and the enzyme catalyzed polydopamine showed better deposition uniformity on the substrate surface. According to molecular simulation analysis, dopamine oligomers were easily combined with the amorphous regions of silk fibroin, and dopamine oligomers and amino acids of silk fibroin could form hydrogen bonds and π–π stacking interactions. Dopamine oligomers could form intermolecular and intramolecular hydrogen bonds through amino groups and hydroxyl groups. In addition, dopamine oligomers would aggregate in the process of binding to silk fibroin and adsorbed to the surface of silk fibroin in the form of aggregates, and Michael addition reaction would also occur between dopamine oligomers and silk fibroin. Finally, the silk fabrics loaded with polydopamine were reacted with different kinds of metal salt solutions to form particles with different morphologies and crystal structures on the surface of the silk fibers, and the modified silk fabrics showed good hydrophobicity.

Dopamine oligomers are easily combined with amorphous regions of silk fibroin, they can form hydrogen bonds and π–π stacking interactions, and undergo Michael addition reactions. The oligomers will aggregate in the process.     

Concurrent occurrence of electrochemical dissolution/deposition of cobalt–calcium phosphate composite

Amorphous cobalt–calcium phosphate composite (CCPC) films are electrochemically prepared on various electrodes by utilizing the solid phase of hydroxyapatite as a phosphate source. The CCPC film formation is surface process in which the dissolution of hydroxyapatite and the deposition of CCPC film concurrently occur on the electrode surface without the mass transfer of phosphate ions into the bulk solution. Elemental, crystallographic, and morphological analyses (EDX, ICP-AES, XPS, and XRD) indicate that the CCPC is composed of amorphous cobalt oxide with calcium and phosphate. The film exhibits durable oxygen evolution reaction (OER) catalytic properties under neutral and basic aqueous condition. Compared to using solution phase of phosphate source, our preparation method utilizing solid hydroxyapatite has advantage of preventing unnecessary chemical reaction between phosphate and other chemical species in bulk solution.

Solid phase of phosphate source (hydroxyapatite) is utilized for the electrochemical preparation of cobalt–calcium phosphate composite (CCPC) film.     

Degradable allyl Antheraea pernyi silk fibroin thermoresponsive hydrogels to support cell adhesion and growth

At present, Antheraea pernyi silk fibroin (ASF) based hydrogels have wide potential applications as biomaterials because of their superior cytocompatibility. Herein, ASF is used as a nucleophilic reagent, reacted with allyl glycidyl ether (AGE) for the preparation of allyl silk fibroin (ASF-AGE). The investigation of ASF-AGE structure by ¹H NMR and FTIR are revealed that reactive allyl groups were obtained on ASF by nucleophilic substitution. A series of ASF based hydrogels are manufactured by N-isopropylacrylamide (NIPAAm) copolymerization bridged with ASF-AGE. By the silk fibroin self-assembly process, stably physical cross-linked hydrogels are formed without any crosslinking agent. These hydrogels exhibit good thermoresponsive and degradability, for which the LCST was about 32 °C, and these hydrogels can be degraded in protease XIV solution. Excellent cell proliferation, viability and morphology is demonstrated for b End.3 cells on the hydrogels by the characteristic MTT assay, CLSM and SEM. The cytocompatibility of b End.3 cells was demonstrated with excellent cell adhesion and growth on these ASF based hydrogels in vitro. These degradable and thermoresponsive ASF based hydrogels may find potential applications for cells delivery devices and tissue engineering.

At present, Antheraea pernyi silk fibroin (ASF) based hydrogels have wide potential applications as biomaterials because of its superior cytocompatibility.     

Both chemical and crystalline phase configuration influence the molecular features of humic acids in humic–calcium–phosphates fertilizers

Phosphate–metal–humic complexes are very relevant in nature due to their crucial role in phosphate availability for plants and microorganisms. Synthetic phosphate–calcium–humic acid (HA) complexes have proven to be efficient sources of available phosphorus for crops. However, the current knowledge about their structure and molecular features is very poor. The structural implications of phosphate interaction with humic binding sites through calcium bridges, in both monocalcium phosphate and dicalcium phosphate is investigated by using molecular modeling, ³¹P-NMR, ¹H-NMR and X-ray diffractometry. The conformational changes in the molecular configuration of the humic acid involved in the interaction resulting from the synthetic process is also studied by using HPSEC and synchronous fluorescence. The results obtained allow us to identify the phosphate type in the crystalline phase that is involved in the interaction of humic acid binding sites and the different forms of calcium phosphate. Synchronous fluorescence also shows that whereas the conformational configuration of the HA binding site is only partially affected in the monocalcium phosphate interaction, it changes in the case of dicalcium phosphate showing simpler molecular arrangements. These changes in the molecular conformation of the binding site in HA in solution may influence the biological activity of the humic acid. On the other hand, HPSEC studies show that the humic–calcium–phosphate interaction is accompanied by increases in the humic acid apparent size distribution. This effect is more intense in the case of monocalcium phosphate system probably due the influence of pH.

Phosphate–metal–humic complexes are very relevant in nature due to their crucial role in phosphate availability for plants and microorganisms.     

Icariin controlled release on a silk fibroin/mesoporous bioactive glass nanoparticles scaffold for promoting stem cell osteogenic differentiation

The treatment of bone defects caused by various reasons is still a major problem in orthopedic clinical work. Many studies on osteogenic implant materials have used various biologically active factors such as osteogenic inducers, but these biologically active factors have various side effects. Therefore, in this study, silk fibroin (SF) was used as a scaffold material, mesoporous bioactive glass nanoparticles (MBGNs) as a sustained release carrier, and the traditional Chinese drug icariin (ICA) was loaded to promote bone formation. The experiments in this study have proven that SF/MBGNs-ICA scaffolds can successfully load and release ICA for a long time, and the sustained-release ICA can promote the proliferation and differentiation of BMSCs for a long time. This controlled-release ICA organic/inorganic two-component scaffold material is expected to become a new bone grafting solution.

Long-term promotion of osteogenic differentiation through silk fibroin/mesoporous bioactive glass-loaded sustained release of icariin.     

丝素蛋白作为组织工程材料应用于角膜的研究进展

背景：丝素蛋白纤维材料具有透明性、结构可塑性、成分单一性、力学强韧性及生物相容性等特点。目的：综述国内外丝素蛋白应用于角膜组织工程的研究进展。方法：由第一作者在标题和摘要中以“silkfibroin,corneal,ocular”或“丝素,角膜”为枪索词,榆索1980至2011年PubMed及1990至2011年CNKI数据库中关于丝素蛋白角膜的文章。结果与结论：从天然蚕丝中提取的高分子丝素蛋白,因其良好的生物相容性、独特的力学性能、光学透明性及降解速率可控性,既可以单独应用于角膜组织结构的重建,又可与其他组织材料联合应用,成为角膜组织工程学心用的理想材料。现已证明多种角膜细胞可在丝素纤维膜上良好生长,但体外培养的细胞应用f动物模型的相关研究较少;此外丝素蛋白材料植入角膜内对其产生何种影响的研究数据较缺乏,这些均是亟待解决的问题。     

Visible sensing of conformational transition in model silk peptides based on a gold nanoparticles indicator

To understand protein structural transition and β-sheet formation is of importance in disparate areas such as silk protein processing and disease related β-amyloid behavior. Herein, GAGSGAGAGSGAGY (GY-14), a tetradecapeptide based on the crystallizable sequence of silk fibroin, was employed as a model peptide of the crystalline regions of silk fibroin. Due to the incorporation of tyrosine (Y), GY-14 was able to reduce Au³⁺ to Au NPs and further stabilize them without any external reducing or capping reagents to produce GY-14 stabilized Au NPs (GY-14@Au NPs). The in situ prepared GY-14@Au NPs were utilized as a built-in colorimetric indicator. The influences of specified physiological factors including decreasing the pH, the addition of calcium ions and isopropanol treatment on the self-assembly behavior of GY-14@Au NPs in aqueous solution have been studied. On the basis of transmission electron microscopy (TEM), dynamic light scattering (DLS), atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy and circular dichroism (CD) measurements, the color changes and the UV-Vis absorption peak shift of GY-14@Au NPs were attributed to the conformational change of the GY-14 peptide. The colorimetric readout can be seen with the naked eye, providing an efficient indicator to study the conformational changes of peptides exposed to various environmental stimuli.

Au NPs prepared in situ were utilized as a built-in colorimetric indicator to monitor conformation changes of a silk peptide.     

羟基磷灰石/丝素蛋白复合多孔材料的制备及其表征

以蚕丝丝素蛋白作为羟基磷灰石沉积的模板,制备羟基磷灰石/丝素蛋白复合凝胶,以此为基体,分别以蚕丝短纤维和NaCl颗粒作为增强材料和致孔剂,采用等静压成型法,制备羟基磷灰石/丝素蛋白多孔复合材料.对复合材料结构和力学性能的研究结果表明,材料中含有少量蚕丝短纤维对材料抗弯强度和断裂能力的提高有显著效果,以NaCI颗粒为致孔剂可使材料的平均孔径及孔隙率分别在64～183 μm及55%～75%范围内调节.