Generation and characterization of inorganic and organic nanotubes on bioengineered flagella of mesophilic bacteria.

Three types of rationally designed peptide loops were genetically engineered for display on the surface of the FliTrx E. coil flagella scaffold, a type of bacterial bionanotube adapted for the multivalent display of peptide loops. The resulting three types of loop flagella fibers were used to demonstrate the feasibility of templating synthesis of inorganic nanotubes and nanoparticles and organic nanotubes. Purified flagella fibers displaying a cationic arginine-lysine loop peptide with three guanidine and three amine functional groups were used to form silica bionanotubes, using two types of silicate ion precursors. Purified flagella fibers displaying a tyrosine-serine-glycine loop peptide with six phenolic and three aliphatic hydroxyl groups were used to initiate formation of titania bionanotubes. Purified flagella fibers displaying an anionic aspartate-glutamate loop peptide with 18 carboxylate groups were used to initiate formation of polyaniline nanotubes and hydroxyapatite nanoparticles, a key component of bones. The resulting nanomaterials were mainly characterized by transmission electron microscopy and additionally by scanning electron microscopy, in the case of polyaniline nanotubes. The studies demonstrate the versatility of employing bioengineered flagella for the generation of a variety of nanoparticle arrays and nanotubes.