Toward Spinning Greener Advanced Silk Fibers by Feeding Silkworms with Nanomaterials

Silk has been used in several biomedical applications, including tissue engineering, drug delivery systems, biomedical implants, and diagnostic medical devices, due to its attractive intrinsic properties such as biocompatibility, controllable biodegradability, and excellent mechanical properties. In recent years, several attempts have been made to produce silk fibers with improved properties and new functionalities by feeding silkworms with modified diets containing nanomaterials. Nanomaterials possess unique physical, chemical, and biological properties and when combined with silk can expand its applicability for biomedical applications. Feeding silkworms with modified diets containing nanomaterials is a greener method of producing functionalized silk fibers when compared to the alternative postfunctionalization methods that include multistep procedures and toxic chemicals. The main advantages of using this greener method are related to the reduced usage of resources such as water, energy, and additional chemicals to spin functional silk fibers, the maintenance of intrinsic silk properties, the stability of the added new functionalities, and the possibility of large-scale production. Feeding silkworms with different nanomaterials such as carbon-based nanomaterials, metal and metal oxide nanoparticles, and quantum dots has led to the production of silk fibers with improved properties (e.g., mechanical and thermal) and/or new functionalities (e.g., magnetical and luminescence). However, nanomaterials concentration, dimensions, and solubility were shown to influence their uptake by silkworms as well as silk fiber properties. Here, we review the literature that focuses on the feeding of silkworms with nanomaterials, highlighting the acquired new functionalities and improved properties of the obtained greener and more sustainable silk fibers.