Silk is a Biomedical Metamaterial: An Oxymoron?

다국어 초록 (Multilingual Abstract)

As protein-based biopolymers produced by spiders and silkworms, silk is a fascinating biomaterial that has been extensively studied for numerous biomedical applications. Several studies show that silk proteins can be reinforced to superior material properties that often do not exist in naturally occurring materials. This idea has an analogy with the concept of metamaterials and metastructures. Research on metamaterials and metastrcutures is centered in constructing materials to have user-designed atypical responses that often do not exhibit in nature. Optical metamaterials are often realized by controlling the electric and magnetic properties, not limited to negative refractive index and invisibility cloaks. Mechanical metamaterials take advantage of artificially engineered structures to determine mechanical properties, relatively independent of material compositions. On the other hand, typical metamaterials are not intended for biomedical applications and their construction primarily relies on exotic materials and complex nanofabrication and nanomanufacturing.
In this talk, we argue that the concept of reinforced or superior silk can be extended to a type of metamaterials. In other words, reinforced silk produced by transgenic silkworms and silkworms fed with special diets could be considered as biomedical metamaterials that are designed for direct utilizations for biological and medical applications. In particular, metamaterial-like silk can serve as an ab initio foundation for opening immediate applications. Reactive oxygen species (ROS)-generating fluorescent silk will offer immediately exploitable and scalable photocatalyst-like biomaterials. The ROS generation and the photoelectric conversion are two sides of the same coin in terms of redox reactions and electrochemistry. As light-fluorescent protein interactions are often understood based on quantum mechanics, fluorescent protein-expression silk could provide an alternative model system for studying quantum biology and quantum biophotonics. Silkworm transgenesis and diet-enhanced silk production can potentially guide synthetic biology approaches to enable the production of superior synthetic silk.