Ultrafine and High-Strength Silk Fibers Secreted by Bimolter Silkworms

Abstract

Ultrafine fibers are widely employed because of their lightness, softness, and warmth retention. Although silkworm silk is one of the most applied natural silks, it is coarse and difficult to transform into ultrafine fibers. Thus, to obtain ultrafine high-performance silk fibers, we employed anti-juvenile hormones in this study to induce bimolter silkworms. We found that the bimolter cocoons were composed of densely packed thin fibers and small apertures, wherein the silk diameter was 54.9% less than that of trimolter silk. Further analysis revealed that the bimolter silk was cleaner and lighter than the control silk. In addition, it was stronger (739 MPa versus 497 MPa) and more stiffness (i.e., a higher Young’s modulus) than the trimolter silk. FTIR and X-ray diffraction results revealed that the excellent mechanical properties of bimolter silk can be attributed to the higher β-sheet content and crystallinity. Chitin staining of the anterior silk gland suggested that the lumen is narrower in bimolters, which may lead to the formation of greater numbers of β-sheet structures in the silk. Therefore, this study reveals the relationship between the structures and mechanical properties of bimolter silk and provides a valuable reference for producing high-strength and ultrafine silk fibers.

Statistical Analysis of the Mechanical Behavior of High-Performance Polymers: Weibull’s or Gaussian Distributions?

“…This behavior is due to the formation and development of surface microcracks at the final stages of orientational drawing, the so-called kink bands, which are initiators of the most intense crack growth at the deformation stages preceding the sample failure [ 1 , 2 ]. For this reason, in order to correctly estimate the average values of σ , E , and strain at break ( ε b ), σ av , E av , and ε av , which are important characteristics playing a key role in choosing the most appropriate fields for material applications, the number of identical samples to be tested should be increased markedly, from the generally accepted about five [ 5 , 6 , 7 , 8 ] to some dozens, or even hundreds [ 2 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. In this case, the statistical distributions of mechanical properties can also be analyzed, and additional information obtained, for instance, on their conformity to a certain theoretical model (e.g., Gaussian [ 23 ], Weibull’s [ 9 , 10 , 11 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]).…”

“…For this reason, in order to correctly estimate the average values of σ , E , and strain at break ( ε b ), σ av , E av , and ε av , which are important characteristics playing a key role in choosing the most appropriate fields for material applications, the number of identical samples to be tested should be increased markedly, from the generally accepted about five [ 5 , 6 , 7 , 8 ] to some dozens, or even hundreds [ 2 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. In this case, the statistical distributions of mechanical properties can also be analyzed, and additional information obtained, for instance, on their conformity to a certain theoretical model (e.g., Gaussian [ 23 ], Weibull’s [ 9 , 10 , 11 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]). It can be helpful for a better understanding of the deformation and fracture mechanisms of materials and for making a more proper recommendation about their practical use.…”

Fabrication of a Silk Sericin Hydrogel System Delivering Human Lactoferrin Using Genetically Engineered Silk with Improved Bioavailability to Alleviate Chemotherapy-Induced Immunosuppression

“…The crystal structure variation of sericin during the process of conversion to hydrogels was assayed by XRD. A strong crystal diffraction peak was detected at approximately 19.0° in sericin hydrogel lyophilized powder (Figure I), which was similar to the crystal peak of silk protein . By contrast, no diffraction peak at 19.0° was detected in the lyophilized sericin solution containing 8 M urea and the urea groups.…”

“…A strong crystal diffraction peak was detected at approximately 19.0°in sericin hydrogel lyophilized powder (Figure 1I), which was similar to the crystal peak of silk protein. 36 By contrast, no diffraction peak at 19.0°was detected in the lyophilized sericin solution containing 8 M urea and the urea groups. Therefore, the crystal structure of sericin would be formed during the process of conversion to hydrogels.…”

Antibacterial Mechanism of Silkworm Seroins

“…As a model organism of lepidopteran insects, B. mori is the most well-known and earliest-used silk-secreting animal. B. mori silk and silk proteins have been extensively researched in-depth and are the most widely used [ 2 , 3 , 4 , 5 , 6 ]. Fibroins and sericins, as the main components of silk, are the macromolecular silk proteins.…”