What is the Secret of Silk’s Natural Strength?

Chinese researchers have discovered the secret of the natural strength of silk spun by silkworm caterpillars.

For over a century, scientists have been trying to figure out a way to make synthetic fibers with similar or even better properties to silkworm and spider gossamer.

The Biological Science Center at Southwest University in Chongqing, China supplied the silkworm strain JingSong which the researchers used.

The silkworm larvae were raised at room temperature until they reached the pupal stage in their development, when they were promptly frozen using liquid nitrogen and then stored at -80°C.

Scientists carefully dissected the silk-producing organs of over 20,000 frozen silkworm larvae over four years. They screened more than a thousand compounds and five thousand more compound combinations to gain insights into the physical structure and assembly of natural silk fibroin (NSF) at various levels, to understand how silkworms and spiders create silk.

The study team discovered that two substances, amphipol and digitonin, helped stabilize the structure of NSF when tested in a lab setting.

Employing modern scientific techniques, they then used these findings to examine NSF’s natural structure and arrangement in the silk gland.

They discovered that NSF forms tiny, disordered fiber structures called nanofibrils throughout the silk gland, influenced by certain metal ions and pH levels. These nanofibrils are arranged into herringbone patterns near the silk-spinning organ, aiding the silkworm’s silk-spinning process.

But how these nanofibrils naturally assemble to form herringbone patterns in the silk-producing organ remains uncertain, the researchers said.

Recent research has shown that a structured herringbone pattern can withstand significant stretching without losing strength, suggesting they are central to silk’s durability, the publication noted.