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Updated: Jul 5, 2025
Microfluidic Dry-spinning and Characterization of Regenerated Silk Fibroin Fibers
Published on: September 4, 2017
Decoding silkworm spinning programmed by pH and metal ions.
Kai Song1, Yejing Wang2, Wenjie Dong3
1Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Biological Science Research Center, Southwest University, Chongqing 400715, China; National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Researchers uncovered how natural silk fibroin (NSF) forms tough fibers. Metal ions and pH changes guide NSF nanofibrils into hierarchical structures, crucial for understanding silk spinning and creating advanced biomaterials.
Area of Science:
- Materials Science
- Biochemistry
- Biomimetics
Background:
- Natural silk is a remarkably tough biomaterial, yet replicating its properties in artificial fibers remains challenging due to incomplete understanding of the in vivo spinning process.
- The precise molecular mechanisms governing the self-assembly of natural silk fibroin (NSF) within the silkworm's silk gland are not fully elucidated.
Purpose of the Study:
- To investigate the in vivo ultrastructure and hierarchical assembly of natural silk fibroin (NSF) in the silk gland lumen.
- To elucidate the role of metal ions and pH gradients in the controlled self-assembly of NSF into high-performance fibers.
Main Methods:
- Large-scale in vitro screening using amphipol and digitonin to stabilize NSF structure.
- Analysis of NSF ultrastructure and hierarchical assembly within the posterior silk gland (PSG) and anterior silk gland (ASG) lumen.
- Investigating the influence of metal ions and pH on NSF nanofibril formation and sol-gelation transition.
Main Results:
- NSF forms reversible, flexible nanofibrils (approx. 4 nm diameter) composed of random coils, not globular micelles or rods.
- Metal ions are essential for NSF nanofibril formation.
- A decreasing pH gradient from PSG to ASG induces NSF hydrophobicity and sol-gelation.
- NSF nanofibrils self-assemble into anisotropic herringbone patterns in ASG-2, preparing for spinning.
Conclusions:
- The study reveals a controlled self-assembly mechanism for NSF, from nanofibrils to hierarchical patterns, driven by metal ions and pH gradients.
- These findings offer critical insights into the spinning mechanisms of silk-secreting animals.
- The elucidated mechanism provides a basis for the bioinspired design of advanced, high-performance artificial fibers.
