Chitosan improves the crystallization of silk fibroin: a three-dimensional scaffold material with better mechanical stability

doi:10.3969/j.issn.2095-4344.2015.12.011

Abstract

Abstract:

BACKGROUND: Silk fibroin as natural biological macromolecules has good biocompatibility, but it is difficult to make the three-dimensional scaffold with uniform structure because of its higher crystallization performance and bigger brittleness.
OBJECTIVE: To improve the crystallization of silk fibroin through the addition of chitosan, and to get three-dimensional tissue engineering scaffolds with better mechanical strength.
METHODS: CaCl₂/CH₃CH₂OH/H₂O ternary solution was used to dissolve silkworm cocoon to extract silk fibroin and form solution. Silk fibroin solution and chitosan solution were mixed according to different mixing ratios of 2:1, 1:1, 1:2, respectively, and then porous silk protein/chitosan scaffolds were prepared by freeze-drying method and treated by methanol. Scaffold morphology was observed by scanning electron microscopy, the chemical structure and crystalline state of the scaffolds were characterized through infrared spectrum and X-ray diffraction test, respectively. Also, the porosity and water uptake were tested and periodic cycle compression mechanical properties under the water environment were determined.
RESULTS AND CONCLUSION: The introduction of chitosan could improve the properties of scaffolds. The porosity of the composite scaffold with lower porosity was more uniform and orderly with higher content of chitosan. When the mixture rate of chitosan and silk fibroin was 1:2, the water uptake rate was the highest in the composite scaffolds, and also higher than that of the silk fibroin scaffold but lower than that of the chitosan scaffold. With the increase of silk fibroin, the composite scaffolds had better elasticity and stronger ability to maintain the shape.

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

全文链接：

Key words: Materials Testing, Chitosan, Silk

CLC Number:

R318

Zhang Xia-zhi, Situ Fang-min, Peng Peng, Jiao Yan-peng. Chitosan improves the crystallization of silk fibroin: a three-dimensional scaffold material with better mechanical stability[J]. Chinese Journal of Tissue Engineering Research, 2015, 19(12): 1858-1863.

Figures/Tables 2

2.1 扫描电镜观察支架材料形貌由图1显示，混入壳聚糖使得丝素蛋白/壳聚糖支架的孔隙结构比纯丝素蛋白支架更均匀有序，并且壳聚糖含量越高复合支架的孔隙分布越均匀、有序。由此可知，壳聚糖的加入可有效抑制丝素蛋白片层结构的生成，明显改善复合支架的孔隙结构。 2.2 支架材料孔隙率测试结果图2显示，不同配比的支架孔隙率表现得极为不同，复合支架的孔隙率较纯壳聚糖或者丝素蛋白支架均变小，其中壳聚糖含量越高，复合支架的孔隙率越低，支架结构较为致密，当壳聚糖与丝素蛋白的混合质量比例为2∶1时，在复合支架中的孔隙率最低，支架材料最致密，可推测得壳聚糖组分的加入可以改变支架的孔隙结构。 2.3 支架材料吸水率测试结果图3显示，不同配比制备的复合支架材料在吸水率上表现出较明显的不同，当壳聚糖与丝素蛋白的混合质量比为1∶2时，吸水率最高，同时明显高于丝素蛋白支架材料，与壳聚糖支架材料相当。支架材料的吸水率主要与支架材料本身的亲疏水性有关，同时也与孔隙率有关系。 2.4 支架材料X射线衍射图图4A显示的是不同支架材料的X射线衍射图谱，8°、15°、22°对应壳聚糖的特征2 θ角，随着壳聚糖含量的减少，壳聚糖的峰强逐渐减弱。SilkⅠ的主要衍射峰为12.2°、19.7°、24.7°、28.2°；而SilkⅡ的主要衍射峰为9.1°、18.9°和20.7°。经冷冻干燥制成的丝素多孔材料没有出现SilkⅠ和SilkⅡ结构的特征峰，说明此多孔材料的聚集态结构以无定型结构为主。 2.5 支架材料傅里叶红外光谱图图4B显示，冷冻干燥丝素在1 650，1 545，1 241 cm-1处分别显示了典型的酰胺Ⅰ、酰胺Ⅱ和酰胺Ⅲ结构，分别对应着丝素的无轨卷曲结构、β-折叠、无轨卷曲结构。丝素蛋白的酰胺Ⅱ峰主要与N-H平面弯曲及C-H伸缩振动相关，它们能够参与分子内氢键的形成并导致β-折叠结构的出现。壳聚糖的红外图谱显示，在1 035，1 083 cm-1出现的峰归属于壳聚糖糖环上的C-O-C和C-O的伸缩振动峰。同时在1 598，1 652 cm-1处存在壳聚糖上酰胺基团的特征吸收峰，分别是C=O的伸缩振动峰，酰胺Ⅰ带；N-H的弯曲振动峰，酰胺Ⅱ带。甲醇处理后丝素蛋白的红外图谱显示(图4B)，在1 626，1 527，1 234 cm-1左右的峰归属于丝素蛋白的β-折叠构象的特征吸收峰，分别对应于酰胺Ⅰ带、酰胺Ⅱ带，酰胺Ⅲ带。因为形成β-折叠，而出现蓝移。处理后壳聚糖的1 650 cm-1的特征峰消失掉了，证明壳聚糖与丝素蛋白发生了分子间的相互作用。1 409 cm-1是壳聚糖的-COOH基团特征峰，因为样品用0.1 mol/L NaOH处理过，所以消失了[10]。"

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