Silk ties to keep bones together.

Silk threads may one day stitch together not only clothing, but muscles and bones as well. Researchers are examining the material as a replacement for tendons and ligaments. Silk fibers have been used for years in surgical sutures and have nearly the same mechanical strength as tendons do, says Yasushi Tamada of the National Institute of Sericultural and Entomological Science in Tsukuba, Japan.

In order to be a good replacement for these body parts, however, silk would need to bind well to bone. Tamada, along with his colleagues at the institute and at Kagoshima University, chemically modified silk fabric and tested its ability to bond with a form of calcium phosphate called hydroxyapatite, the main mineral constituent of bone. Negatively charged phosphate molecules added to the silk enabled the fabric to absorb 10 times more calcium than untreated fabric and to support a growing layer of hydroxyapatite.