Genetically Modifiable Flagella as Templates for Silica Fibers: From Hybrid Nanotubes to 1D Periodic Nanohole Arrays

Abstract

Bacterial flagellum is a protein nanotube that is helically self‐assembled from thousands of a protein subunit called flagellin. The solvent‐exposed domain of each flagellin on the flagella is genetically modifiable, in that a foreign peptide can be genetically inserted into this domain, leading to the high‐density display of this foreign peptide on the surface of flagella. In this work, wild‐type and genetically engineered flagella (inner diameter of ∼2 nm and outer diameter of ∼14 nm) detached from the surface of Salmonella bacterial cells are used as templates to site‐specifically form silica sheaths on the flagellar surface, resulting in the formation of double‐layered silica/flagella nanotubes. The flagella templates inside the silica/flagella nanotubes can be removed to obtain silica nanotubes by calcining the nanotubes at high temperature (550°C). Further calcination of the silica nanotubes at a higher temperature (800 °C) leads to the formation of a periodic nanohole array along the silica fibers with a center‐to‐center nanohole spacing of ∼79 nm. It is demonstrated that the double‐layered silica‐flagella nanotubes can be used for selective CdTe quantum dot uptake into the inner channels or selective Au nanoparticle coating on the outer wall of the nanotubes due to the different chemistry between inner flagellum core (protein) and outer silica wall of the nanotubes. It is also found that flagella displaying different peptides result in different morphologies of the silica nanotubes. This work suggests that the monodisperse diameter and genetically tunable surface chemistry of the flagella can be exploited for the fabrication of silica nanotubes with uniform diameter and controllable morphologies as well as silica nanofibers decorated with periodic nanohole arrays.

Green Synthesis of Metallic Nanoparticles via Biological Entities

“…Bacteria, bacteriophages and viruses are attractive assemblers for manufacturing one dimensional structures into ordered arrays. For example, the tobacco mosaic virus has been used to assemble Au, Ag and Pt nanoparticles [298] and filamentous bacteriophages have been used to form silica fibres and nanotubes [299,300,301,302]. These nanometre scale entities are very effective templates for forming well-ordered 1D assemblies [303,304].…”

Bio-inspired synthesis of metal nanomaterials and applications

“…Some metal ions might be adsorbed and further reduced to elemental metals by microorganisms, plants, biomass, etc. [19][20][21][22][23][24][25] 1.2 Scope of the present review Based on the scale of bio-inspired candidates, bio-inspired syntheses can be divided into two different types, namely synthesis using (1) biomatrices with sizes ranging from nanometers and microns to macroscale, e.g., microorganisms, live plants and viruses ((a) in Fig. Seminal reports on bioinspired synthesis date back to the late 90s when Ag and Au NPs were prepared from Pseudomonas stutzeri AG259 10 and alfalfa plant biomass, 11 respectively.…”

“…Protein-and DNA-templated noble metal NCs have been actively explored for the detection of Hg(II) ions. The fluorescence intensity of BSA-templated Au 25 NCs decreased linearly over the Hg(II) concentration range of 1-20 nM. 328 The surface of as-prepared Au cluster is stabilized by a small amount of Au(I), which has a strong and specific interaction with Hg(II) ions.…”

Morphology-controlled synthesis of silica nanotubes through pH- and sequence-responsive morphological change of bacterial flagellar biotemplates

“…12 Aminopropyltriethoxysilane (APTES) was first mixed with flagella and followed by adding TEOS. The APTES should play dual roles in directing the in situ transcription of silica nanotubes on the flagellar surface.…”

“…Coating of silica on flagella templates used the methods we previous described 12 with some modifications. Briefly, APTES (2×10 −3 mmol) was mixed and agitated gently with flagella solution (500 mL) by vortex mixer.…”