Convenient and flexible approach to alter silk properties
NARO has developed a genetically modified silkworm that can easily bind functional components into silk proteins using the genetic code expansion strategy. Silkworm was engineered to incorporate unnatural amino acids with chemical handles into silk proteins to bind desired functional components such as pigments and drugs which can conveniently and flexibly enhance the properties of silk. The fundamental technology was first developed in 2014, and this time, NARO in collaboration with the RIKEN Center for Life Science Technologies has successfully increased the efficiency of incorporating chemical handles into silk proteins up to 30-fold, paving the way for practical production. This result is expected to facilitate the development of silk that retains its color even after repeated washing and silk materials that combine drugs for medical purposes.
- The Institute of Agrobiological Sciences, NARO (NIAS) is developing silk with new properties to expand the use of silk to various fields and applications. In 2014, NIAS developed a silk incorporating unnatural amino acids with chemical handles (4-azidophenylalanine, AzPhe) that can easily bind functional molecules using genetically modified silkworms. Combining functional molecules such as pigments and drugs facilitated the production of silk with various properties.
- Initially, it was necessary to add a large amount of expensive unnatural amino acids into the diet of silkworm which was a big problem in terms of production cost. In this study, NIAS collaborated with the RIKEN Center for Life Science Technologies and successfully increased the efficiency of incorporating AzPhe into silk proteins to approximately 30-fold. Hence the cost of supplementing unnatural amino acids necessary to produce cocoon is greatly reduced towards practical production. Silk with that can bind functional molecules can be produced with a cost increase of about 10 to 50% as compared with ordinary genetically modified cocoon.
- Using silk that can bind functional components, it is possible to create various kinds of functionalized silk easily and quickly, not only from cocoon and raw silk but also silk processed into film or sponge, by simply by immersing the cocoon in a solution containing the target functional components. It is particularly suitable for functionalization with synthetic dyes, drugs, synthetic polymers, etc. in which chemical handles are easily incorporated. Since these functional components cannot be incorporated by normal genetic recombination, utilization of a proper genetic recombination strategy will facilitate diverse functionalization of silk.
- With this result, it becomes possible to develop color silk that retains its color even after repeated washing and drugs such as wound healing film.
- The results are now available in the online version of the journal ACS Synthetic Biology published by the American Chemical Society on February 26, 2018.
Teramoto H, Amano Y, Iraha F, Kojima K, Ito T, Sakamoto K. 2018. Genetic code expansion of the silkworm Bombyx mori to functionalize silk fiber. ACS Synthetic Biology (DOI: 10.1021/acssynbio.7b00437)