Microwave-Assisted Synthesis of Luminescent Carbonaceous Nanoparticles as Silkworm Feed for Fabricating Fluorescent Silkworm Silk

In biomedical engineering, optics, and photonics, fluorescent silkworm silk has many potential applications, but its complex preparation process and the environmental pollution of corresponding chemical dyeing methods hinder its development. Herein, we provide a green and effective method for fabricating fluorescent silkworm silk with enhanced mechanical properties. Citric acid and urea were selected as raw materials for synthesizing carbon dots (CDs), which were applied as additives of silkworm feed to produce fluorescent silkworm silks by microwave-assisted methods. The results showed that a diet of mulberry leaf with 0.5 wt% CDs was safe for silkworms and did not affect silk yield. CDs rapidly entered silkworms and accumulated in their blood and silk glands. After feeding for 90 min, the silk gland fluorescence appeared prominent. Compared with ordinary silk, the highest elongation at break of the CD-modified silk was 22.24%, and the breaking strength was 28.07 MPa, which were increases of 5.05 and 22.84%, respectively. The CD-modified silk displayed intrinsic blue fluorescence when exposed to a 405 nm laser, exhibited no cytotoxic effect on L929 cells and had excellent cell adhesion. The strategy proposed in this work is not only environmentally friendly but can also produce high-quality fluorescent silk on a large scale.