Intrinsically Fluorescent Silks from Silkworms Fed with Rare-Earth Upconverting Phosphors.

Fluorescent silk fibroin (SF) fibers have great potential in biomedical application and special functions for marking and tracking. How to fabricate fluorescent SF fibers with good fluorescence stability by a simple and environmentally friendly method has yet to be explored. Here, we successfully produced fluorescent SF fibers by using silkworms as bioreactors to introduce rare-earth upconverting phosphors (UCPs) into silk fibroin. The modified silk exhibited bright green colors under 980 nm laser. This directly feeding method to produce fluorescent SF fibers is green and environmentally friendly and easy to use for mass production. Moreover, it provides an idea that SF fibers can be cooperated with more fluorescent materials which could exhibit different colors with a certain wavelength of light for broad application.