iScience. 2019 Jul 3;17:277-287. doi: 10.1016/j.isci.2019.06.036. [Epub ahead of print]

Genetically Engineered Flagella Form Collagen-like Ordered Structures for Inducing Stem Cell Differentiation.

Li D¹, Zhu Y¹, Yang T², Yang M³, Mao C⁴.

Abstract

Bacteria use flagella, the protein nanofibers on their surface, as a molecular machine to swim. Flagella are polymerized from monomers, flagellins, which can display a peptide by genetic means. However, flagella as genetically modifiable nanofibers have not been used in building bone extracellular matrix-like structures for inducing stem cell differentiation in non-osteogenic medium. Here we discovered that interactions between Ca²⁺ ions and flagella (displaying a collagen-like peptide (GPP)₈ on every flagellin) resulted in ordered bundle-like structures, which were further mineralized with hydroxyapatite to form ordered fibrous matrix. The resultant matrix significantly induced the osteogenic differentiation of stem cells, much more efficiently than wild-type flagella and type I collagen. This work shows that flagella can be used as protein building blocks in generating biomimetic materials.