Characterization and Scaled-Up Production of Azido-Functionalized Silk Fiber Produced by Transgenic Silkworms with an Expanded Genetic Code.

Hidetoshi Teramoto,Kenichi Nakajima,Masatoshi Iga,Hiromi Tsuboi

doi:10.3390/ijms20030616

Abstract

The creation of functional materials from renewable resources has attracted much interest. We previously reported on the genetic code expansion of the domesticated silkworm Bombyx mori to functionalize silk fiber with synthetic amino acids such as 4-azido-L-phenylalanine (AzPhe). The azido groups act as selective handles for biorthogonal chemical reactions. Here we report the characterization and scaled-up production of azido-functionalized silk fiber for textile, healthcare, and medical applications. To increase the productivity of azido-functionalized silk fiber, the original transgenic line was hybridized with a high silk-producing strain. The F1 hybrid produced circa 1.5 times more silk fibroin than the original transgenic line. The incorporation efficiency of AzPhe into silk fibroin was retained after hybridization. The tensile properties of the azido-functionalized silk fiber were equal to those of normal silk fiber. Scaled-up production of the azido-functionalized silk fiber was demonstrated by rearing circa 1000 transgenic silkworms. Differently-colored fluorescent silk fibers were successfully prepared by click chemistry reactions, demonstrating the utility of the azido-functionalized silk fiber for developing silk-based materials with desired functions.

Highlights

Materials development based on naturally derived renewable resources is of great interest because such sources are independent of fossil resources and have lower impact on the environment [1,2,3]
We demonstrated the preparation of differently-colored fluorescent silk fibers by click chemistry reactions
A decrease in the copy number would lead to decreased expression of the mutant enzyme, which might lead to lowered incorporation of AzPhe into silk fibroin

Summary

Introduction

Materials development based on naturally derived renewable resources is of great interest because such sources are independent of fossil resources and have lower impact on the environment [1,2,3]. The development of novel technologies to utilize B. mori silk could lead to the creation of high-performance bio-based materials for textile, healthcare, and medical fields. We have been developing a novel technology to incorporate synthetic amino acids with unnatural functional groups into silk fibroin [7,8,9,10], which is the major protein component of B. mori silk and is regarded as a heterodimer of fibroin heavy chain (FibH; ~390 kDa) and fibroin light chain (FibL; ~26 kDa). The technology for incorporating synthetic amino acids into proteins is referred to as genetic code expansion, and it could enhance the utility of proteins as renewable materials. In the case of silk fibroin, incorporation of synthetic amino acids bearing azido groups endows the fibers with novel functionalities. Azido groups can act as selective chemical handles for further modifications with desired functional molecules for specific applications

Methods

Results

Conclusion