Kgomo Hlobsile, Ncube Somandla, Mhuka Vimbai, Kebede Temesgen Girma, Dube Simiso, Nindi Mathew M
Department of Chemistry, The Science Campus, University of South Africa, Private Bag X6, Florida 1710, South Africa.
Polymers (Basel). 2021 Feb 12;13(4):549. doi: 10.3390/polym13040549.
Limited studies have been done on silk fibroins of wild silkworm species owing to their relative insolubility in many solvents. In this study, the solubility of wild silk fibroin in different salts (LiBr, LiCl, Ca(NO), and CaCl) dissolved in formic acid under varying temperatures was investigated. The dissolution conditions under which the solubility was optimum were optimized using a central composite design approach. The optimum range for solvation of the fibroin were visualized using contour plots. The influence of temperature and salt concentration were found to significantly influence the solvation of the fibroin. Following the successful dissolution of the fibroin, the regenerated silk fibroin solutions were cast to obtain water insoluble films which were used in investigating optimum electrospinning conditions. Average nanofiber diameters in the 110-141 nm range were obtained under optimum electrospinning conditions. The silk forms were characterized using the FTIR, TGA, XRD, and SEM to understand their properties. The investigations revealed that formic acid-salt solvents were effective in the solvation of the wild silk fibroin. Some of the dissolution conditions induced mild effects on the silk fibroin while others were harsh. Furthermore, processing to nanofibers resulted in the degradation of the β-sheets producing nanofibers rich in α-helices. However, post-treatment using methanol and water vapor were effective in restoring β-sheet crystallinity.
由于野生蚕种的丝素蛋白在许多溶剂中相对不溶，因此对其进行的研究有限。在本研究中，研究了野生丝素蛋白在不同盐（LiBr、LiCl、Ca(NO) 和 CaCl）溶解于甲酸中的情况下，在不同温度下的溶解度。使用中心复合设计方法优化了溶解度最佳的溶解条件。使用等高线图可视化了丝素蛋白溶剂化的最佳范围。发现温度和盐浓度的影响对丝素蛋白的溶剂化有显著影响。在丝素蛋白成功溶解后，将再生的丝素蛋白溶液浇铸以获得水不溶性薄膜，用于研究最佳电纺丝条件。在最佳电纺丝条件下获得了110-141nm范围内的平均纳米纤维直径。使用FTIR、TGA、XRD和SEM对丝的形态进行表征，以了解它们的性能。研究表明，甲酸盐溶剂对野生丝素蛋白的溶剂化有效。一些溶解条件对丝素蛋白产生温和影响，而另一些则很苛刻。此外，加工成纳米纤维导致β-折叠降解，产生富含α-螺旋的纳米纤维。然而，使用甲醇和水蒸气进行后处理有效地恢复了β-折叠结晶度。
