How to Improve Physico-Chemical Properties of Silk Fibroin Materials for Biomedical Applications?—Blending and Cross-Linking of Silk Fibroin—A Review

This review supplies a report on fresh advances in the field of silk fibroin (SF) biopolymer and its blends with biopolymers as new biomaterials. The review also includes a subsection about silk fibroin mixtures with synthetic polymers. Silk fibroin is commonly used to receive biomaterials. However, the materials based on pure polymer present low mechanical parameters, and high enzymatic degradation rate. These properties can be problematic for tissue engineering applications. An increased interest in two- and three-component mixtures and chemically cross-linked materials has been observed due to their improved physico-chemical properties. These materials can be attractive and desirable for both academic, and, industrial attention because they expose improvements in properties required in the biomedical field. The structure, forms, methods of preparation, and some physico-chemical properties of silk fibroin are discussed in this review. Detailed examples are also given from scientific reports and practical experiments. The most common biopolymers: collagen (Coll), chitosan (CTS), alginate (AL), and hyaluronic acid (HA) are discussed as components of silk fibroin-based mixtures. Examples of binary and ternary mixtures, composites with the addition of magnetic particles, hydroxyapatite or titanium dioxide are also included and given. Additionally, the advantages and disadvantages of chemical, physical, and enzymatic cross-linking were demonstrated.     

丝素蛋白/壳聚糖复合支架有良好的细胞相容性与渗透性

文题释义：丝素蛋白/壳聚糖复合支架：将壳聚糖溶于浓度为1%的冰乙酸,制备成质量浓度为35 g/L的壳聚糖溶液并与丝素蛋白溶液融合,将素蛋白与羧化壳聚糖按照体积比8∶2的比例混合,再将混合溶液注入48孔板中,每孔注入1 mL,最后通过冷冻干燥得到丝素蛋白/壳聚糖复合支架。 热重分析：是指在程序控制温度下测量待测样品的质量与温度变化关系的一种热分析技术,用来研究材料的热稳定性和组分。实验中将10 mg待检验的样品放于氮气环境下进行检测,测试温度升高控制范围为30-800 ℃,温度上升速度为10 ℃/min。 背景：丝素蛋白与壳聚糖为组织工程常用的支架材料,但二者单独应用均存在一定的不足,将两者混合使用可以互为改性,充分发挥优点,获取理想的复合支架材料。 目的：制备丝素蛋白/壳聚糖复合支架并对其进行性能测定。 方法：通过冷冻干燥方法制备丝素蛋白/壳聚糖复合支架,采用电镜扫描检测复合支架的形态结构,并进行热重分析、力学性能及细胞毒性检测。制备季铵化壳聚糖,利用核磁共振仪表征其核磁氢谱,Zeta电位仪检测其电位和粒径分布,凝胶电泳实验检测其保护DNA的情况,透射电镜观察其与DNA结合情况。 结果与结论：①扫描电镜显示丝素蛋白/壳聚糖复合支架具体良好的三维孔洞结构,孔径为50-100 μm;②热重分析显示当温度小于200 ℃时,丝素蛋白/壳聚糖复合支架的质量损失下降速度较低;当温度上升至200-500 ℃时,支架质量损失速度开始加快,损失量增多;在800 ℃时,复合支架的残余质量为38%;③丝素蛋白/壳聚糖复合支架的最大应变可以达到94.94%,最大承受应力为7.01 MPa;④CCK-8实验显示,丝素蛋白/壳聚糖复合支架对兔骨髓间充质干细胞没有细胞毒性,具有良好的细胞相容性;⑤核磁氢谱检测显示,季铵化壳聚糖的季铵化程度约为20%;⑥季铵化壳聚糖的粒径分布为(588.56±52.39) nm,季铵化壳聚糖颗粒的表面带正电荷,电位为(16.3±3.92) mV,有利于与DNA结合;⑦凝胶电泳实验显示,季铵化壳聚糖材料的比例越高,对DNA的包裹越好,当其与DNA的比例为1∶3时,对DNA达到包裹作用;⑧透射电镜显示,季铵化壳聚糖/DNA大部分的微粒呈实心圆形,微粒粒径差别较小,平均粒径约为200 nm;⑨结果表明,丝素蛋白/壳聚糖复合支架有良好的细胞相容性与细胞渗透性,利于细胞在支架间的生长。 ORCID: 0000-0002-2572-0229(章晓云) 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

Controlled release of stromal cell-derived factor-1α from silk fibroin-coated coils accelerates intra-aneurysmal organization and occlusion of neck remnant by recruiting endothelial progenitor cells

This study is to test the efficacy of stromal cell-derived factor-1α (SDF-1α)-coated coils together with endothelial progenitor cells (EPCs) transplantation in occluding aneurysms. Bone marrow-derived EPC surface markers were analyzed using flow cytometry. The migratory function of EPCs in response to SDF-1α was evaluated using a modified Boyden chamber assay. Capillary-like tube formation was assessed using Matrigel gel. Coil morphologies before and after coating with SDF-1α were observed under a scanning electron microscope. The level of SDF-1α in supernatants was measured by ELISA. Sprague-Dawley rats were randomly allocated into five groups. Histological analysis was performed on days 14 and 28 after coil implantation. The bone marrow-EPCs could express CD133, CD34, and VEGFR-2 and form tubule-like structures in vitro. Migratory ability of EPCs in the presence of SDF-1α-coated coils was similar to that in the presence of 5 ng/ml SDF-1α gradient. Sustained release of SDF-1α was achieved using silk fibroin as a carrier. In SDF-1α-coated coils + EPCs transplantation group, a well-organized fibrous tissue bridging the orifice of aneurysms was shown on days 14 and 28. On day 28, tissue organization was greater in the SDF-1α-coated coils group than in the unmodified coils group. Immunofluorescence showed α-smooth muscle actin-positive cells in organized tissue in sacs. Combined treatment with SDF-1α-coated coils and EPCs transplantation is a safe and effective treatment for rat aneurysms. This may provide a new strategy for endovascular therapy following aneurysmal subarachnoid hemorrhage.     

Phospholipid‐induced silk fibroin hydrogels and their potential as cell carriers for tissue regeneration

Silk fibroin (SF) hydrogels can be obtained via self‐assembly, but this process takes several days or weeks, being unfeasible to produce cell carrier hydrogels. In this work, a phospholipid, namely, 1,2‐dimyristoyl‐sn‐glycero‐3‐phospho‐(1′‐rac‐glycerol) sodium salt (DMPG), was used to induce and accelerate the gelation process of SF solutions. Due to the amphipathic nature and negative charge of DMPG, electrostatic and hydrophobic interactions between the phospholipids and SF chains will occur, inducing the structural transition of SF chains to the beta sheet and consequently a rapid gel formation is observed (less than 50 min). Moreover, the gelation time can be controlled by varying the lipid concentration. To assess the potential of the hydrogels as cell carriers, several mammalian cell lines, including L929, NIH/3T3, SaOS‐2, and CaSki, were encapsulated into the hydrogel. The silk‐based hydrogels supported the normal growth of fibroblasts, corroborating their cytocompatibility. Interestingly, an inhibition in the growth of cancer‐derived cell lines was observed. Therefore, DMPG‐induced SF hydrogels can be successfully used as a 3D platform for in situ cell encapsulation, opening promising opportunities in biomedical applications, such as in cell therapies and tissue regeneration.     

蚕丝蛋白材料对鼠胚表皮细胞毒性的实验研究

目的研究不同蚕丝蛋白材料对鼠胚表皮细袍的毒性及其影响细胞增殖的因素。方法采用组织块培养法体外原代培养鼠胚表皮细胞，用直接接触法和浸提液法体外培养鼠胚表皮细胞，MTT比色法检测其在不同蚕丝蛋白材料上的增殖活力和细胞相对增殖率，进行毒性分析；并用活细胞计数法观察不同蚕丝蛋白材料对鼠胚表皮细胞生长的影响。结果鼠胚表皮细胞在1、2、4、5、7、8、10号各型蚕丝蛋白材料上生长，其增殖活力与细胞对照组相当（P〉0.05）；在3、6、9号化学交联或HY-823交联型蚕丝蛋白材料上生长，其增殖活力均低于细胞对照组（P〈0．05）；而在11号蚕丝蛋白材料其增殖活力显著低于细胞对照组（P〈0．01）。1、7号丝胶材料细胞毒性分级为0级（无毒），2、3、4、5、6、8、9、10号各型蚕丝蛋白材料细胞毒性分级为1级（轻微毒），而11号蚕丝蛋白材料细胞毒性分级为2级（中度毒）。活细胞计数结果与MTT检测结果基本相一致。结论除11号蚕丝蛋白材料外，1～10号各型蚕丝蛋白材料无明显细胞毒性，能支持鼠胚表皮细胞正常生长，具有良好的细胞相容性。     

玉米须总黄酮的提取及鉴别

目的为充分利用玉米须植物资源,避免资源的浪费,探讨玉米须总黄酮的提取及鉴别方法。方法采用纯物理的工艺流程过程和分光光度法从玉米须中提取黄酮类物质,对所提取的黄酮类物质进行验证。结果测得样品中总黄酮的含量C=6.45%,回收率为97.9%,其纯度和产率均较高。结论该方法采用全物理过程,无任何化学变化及污染,是提取玉米须黄酮类物质的有效途径。     

腹腔镜下丝线结扎法治疗精索静脉曲张的临床疗效分析

目的探讨腹腔镜下用丝线结扎法治疗精索静脉曲张的疗效。方法回顾性分析采用腹腔镜下丝线结扎法治疗73例精索静脉曲张的临床效果。结果73例手术全部获得成功,手术时间为15～30min,平均20min,平均住院时间4d。术后随访2～24个月,症状全部缓解或消失,无一例复发或睾丸萎缩。结论腹腔镜下丝线结扎法治疗精索静脉具有创伤小、恢复快、疗效好的优点,同时可减少体内异物存留,是治疗精索静脉曲张,尤其是治疗双侧精索静脉曲张的首选方法。     

Adverse reactions to virgin silk sutures in cataract surgery

During the past 3 years, 12 patients (14 eyes) were encountered with severe reactions to virgin silk sutures used in cataract surgery. These reactions included nodular episcleritis, peripheral corneal ulceration, and wound necrosis with dehiscence, sometimes resulting in endophthalmitis or epithelial downgrowth. Conjunctival and scleral histopathologic studies in four eyes showed acute and chronic inflammation with multinucleated giant cells. Successful treatment included removal of the virgin silk sutures, resuturing with 10-0 nylon sutures, securing the necrotic tissue with cyanoacrylate adhesive, and resection of the inflamed superior conjunctiva. All four patients who had bilateral cataract surgery experienced either simultaneous flare-ups of both eyes or accelerated reactions after surgery on the second eye, which suggests a possible role of prior sensitization.     

A scanning electron microscope study of plaque accumulation on silk and PVDF suture materials in oral mucosa

AIM: To examine plaque accumulation on silk and polyvinylidene fluoride (PVDF) sutures at different time intervals. METHODOLOGY: Twenty-one male albino rabbits received sutures under general and local anaesthesia. After 3, 5 and 7 days sutures were removed and processed for scanning electron microscope (SEM) observation. The Friedman and the Wilcoxon tests were used to compare contamination on PVDF and silk suture materials at different time intervals. RESULTS: At all time intervals, the whole surface of silk sutures was covered with a thick layer of bacterial plaque and debris. Microorganisms and blood cells on the surface and between the filaments of the silk suture material were observed. Light debris appeared around the knot area of PVDF sutures after 3 days. At 5 and 7 days, contamination could be seen in scattered areas along the suture material. The average contaminated area was smaller on PVDF suture materials, which were removed at 5 than at 7 days after insertion. At 3 days, PVDF sutures showed significantly less contamination than at 5 and 7 days (P = 0.002). There were statistically significant differences between silk and PVDF sutures at 3, 5 and 7 days. CONCLUSION: SEM observation showed that PVDF sutures were contaminated less than silk sutures at 3, 5 and 7 days.