Structural and mechanical properties of engineered silkworm-spider composite silk

Area of Science:

• Biomaterials Science
• Genetics and Genomics
• Textile Engineering

Background:

• Spider silk possesses superior mechanical properties and biocompatibility, making it valuable for biomaterials and medicine.
• Large-scale spider silk production is challenging due to difficulties in spider farming and low yields.
• Transgenic silkworms offer a scalable alternative for producing spider silk proteins.

Purpose of the Study:

• To enhance silkworm silk properties by incorporating functional spider silk proteins.
• To investigate the effect of varying repeat numbers of the black widow spider silk gene (cre-MaSp1) fused to the silkworm sericin 1 gene (Ser1).
• To evaluate the mechanical performance of the resulting composite silk.

Main Methods:

• Utilized transcription activator-like effector nuclease (TALEN)-mediated genome editing to fuse 1-, 2-, 4-, and eightfold repeats of the cre-MaSp1 gene into the endogenous Ser1 gene of silkworms.
• Analyzed the secondary structure of the composite silk proteins using AlphaFold 3 and infrared spectroscopy.
• Assessed the mechanical properties (maximum stress and strain) of the engineered silk through tensile testing.

Main Results:

• Successful expression and secretion of fusion proteins into the cocoon shell were confirmed.
• Increased β-sheet and helix content in composite silks correlated with higher cre-MaSp1 repeat numbers.
• The composite silk with eightfold cre-MaSp1 repeats exhibited a 39.4% increase in maximum stress and a 62.2% increase in maximum strain compared to wild-type silk.

Conclusions:

• TALEN-mediated gene editing is effective for creating transgenic silkworms with enhanced silk properties.
• Incorporating multiple repeats of the cre-MaSp1 gene significantly improves the mechanical strength and elasticity of silkworm silk.
• This approach expands the potential of silkworm silk as a bioreactor for advanced biomaterial applications.