Osteoinductive recombinant silk fusion proteins for bone regeneration

Area of Science:

• Biomaterials Science
• Protein Engineering
• Regenerative Medicine

Background:

• Organic-inorganic interfaces are crucial for biomaterial function in tissue repair and regeneration.
• Protein polymers offer tunable designs but have limitations in fine-tuning properties and functionalization for specific applications.
• Genetic engineering can improve the biological performance of protein-based biomaterials.

Purpose of the Study:

• To genetically engineer spider silks with hydroxyapatite binding domains (VTK) to create novel organic-inorganic hybrid systems.
• To investigate the effect of VTK domain placement (N-, C-, or both termini) on material properties, biomineralization, and osteogenesis.
• To assess the suitability of silk-VTK fusion proteins for mineralization and functionalization in biomedical applications, particularly bone regeneration.

Main Methods:

• Genetic engineering of spider silk proteins with the VTK domain.
• Fusion of the VTK domain to N-, C-, or both termini of the spider silk domain.
• Characterization of physical properties of recombinant silk-VTK constructs.
• Assessment of biomineralization (hydroxyapatite formation) and osteogenic potential using human mesenchymal stem cells (hMSCs).

Main Results:

• Fusion of the VTK domain did not alter the physical properties of the silk constructs.
• The VTK domain was critical for inducing biomineralization, with significantly increased crystalline hydroxyapatite formation when placed on both termini.
• All recombinant proteins supported hMSC growth and proliferation.
• The presence of the VTK domain enhanced osteoinductive properties up to threefold compared to silk alone.

Conclusions:

• Silk-VTK fusion proteins are suitable for controlled mineralization and functionalization.
• The strategic placement of the VTK domain, particularly at both termini, significantly enhances hydroxyapatite formation.
• These engineered silk-VTK proteins show promise as osteoinductive biomaterials for bone regeneration.