Ultrafine and High-Strength Silk Fibers Secreted by Bimolter Silkworms.

Kaiyu Guo,Yan Zhang,Xiaolu Zhang,Haoyun Li,Qingyou Xia,Zhaoming Dong,Ping Zhao,Yuqing Chen,Yuhui Ni

doi:10.3390/polym12112537

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.

Highlights

Bombyx mori silk fiber has a long history of application in the textile industry since it was discovered; the fibers were unwound from cocoons and used to manufacture strong and unique fabrics
We reported on the treatment of a trimolter mutant silkworm strain with the anti-juvenile hormone (AJH) KK-42 to induce bimolters, which produced more closely packed cocoons and ultrafine silk fibers
Showed that the bimolter silk fibroin possessed a higher content of β-sheet structures and fewer random coil and helical structures

Summary

Introduction

Bombyx mori silk fiber has a long history of application in the textile industry since it was discovered; the fibers were unwound from cocoons and used to manufacture strong and unique fabrics. Ultrafine fiber has been widely used in many fields because of its excellent characteristics, including its high detergency, heat preservation, softness, and lightness [1,2,3]. The light weight fabrics and clean cloths composed of ultrafine fibers are popular in Japan and Europe. Thin silk fibers are typically obtained by breeding trimolter strains or inducing normal tetramolters into trimolters. This process is followed since trimolter silk is thinner than typical tetramolter silk, which suggests that further reducing the number of molts could produce thinner silk. Numerous studies have focused on trimolters induced by hormone-like chemicals [4,5,6]

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Discussion

Conclusion