In vivo Incorporation of an Alkyne-Bearing Amino Acid into Bombyx mori Silk Fibroin

Abstract

Bombyx mori silk fibroin is a natural protein material characterized by mechanical toughness and biocompatibility, which makes it a promising candidate for the development of biomaterials. To adapt silk fibroin to a diverse range of applications, versatile methods for tuning its properties are desirable. Here, we report the in vivo incorporation of an alkyne-bearing unnatural amino acid, 4-ethynylphenylalanine (EthPhe), into B. mori silk fibroin and demonstrate that EthPhe can be used as a selective chemical handle for conjugation with functional molecules by click chemistry. EthPhe-incorporated silk fibroin (AlkyneSilk) is produced by oral administration of EthPhe to transgenic B. mori larvae expressing a mutant of the B. mori phenylalanyl-tRNA synthetase α-subunit in posterior silk glands. We verified that ethynyl groups in AlkyneSilk selectively react with azide-bearing molecules, demonstrating the utility of AlkyneSilk as a “clickable” silk material which can be easily decorated with desired functional molecules.