Disruption of the Metal Ion Environment by EDTA for Silk Formation Affects the Mechanical Properties of Silkworm Silk

• Published in: International journal of molecular sciences Vol. 20; no. 12; p. 3026
• Main Authors: Liu, Qingsong, Wang, Xin, Tan, Xiaoyin, Xie, Xiaoqian, Dong, Haonan, Li, Xinning, Li, Yi, Zhao, Ping, Xia, Qingyou
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 21.06.2019; MDPI
• Subjects: Acetic acid; Animal Feed - analysis; Animals; Aqueous solutions; Biomechanical Phenomena; Bombyx - chemistry; Bombyx - metabolism; Chelating agents; Chelation; Disruption; Edetic acid; Edetic Acid - administration & dosage; Edetic Acid - metabolism; Elastic Modulus; Ethylenediaminetetraacetic acids; Fourier analysis; Fourier transforms; Infrared analysis; Infrared spectroscopy; Ions; Larvae; Mechanical properties; metal ion; Metal ions; Metals - analysis; Metals - metabolism; Morphology; Nanoparticles; Physical characteristics; Protein Conformation, beta-Strand; Proteins; Quantitative analysis; Researchers; Scanning electron microscopy; Silk; Silk - chemistry; Silk - metabolism; silk fiber; Silkworms; Spectroscopy, Fourier Transform Infrared; Spectrum analysis; Stress, Mechanical; Studies; mechanical properties; silk fiber; metal ion
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms20123026

Silk fiber has become a research focus because of its comprehensive mechanical properties. Metal ions can influence the conformational transition of silk fibroin. Current research is mainly focused on the role of a single ion, rather than the whole metal ion environment. Here, we report the effects of the overall metal ion environment on the secondary structure and mechanical properties of silk fibers after direct injection and feeding of silkworms with EDTA. The metal composition of the hemolymph, silk gland, and silk fiber changed significantly post EDTA treatment. Synchrotron FTIR analysis indicated that the secondary structure of silk fiber after EDTA treatment changed dramatically; particularly, the β-sheets decreased and the β-turns increased. Post EDTA treatment, the silk fiber had significantly decreased strength, Young's modulus, and toughness as compared with the control groups, while the strain exhibited no obvious change. These changes can be attributed to the change in the metal ion environment in the silk fibroin and sericin in the silk gland. Our investigation provides a new theoretical basis for the natural silk spinning process, and our findings could help develop a method to modify the mechanical properties of silk fiber using metal ions.