FtsZ cytoskeletal filaments as a template for metallic nanowire fabrication

Supramolecular protein assemblies can serve as templates for the fabrication of inorganic nanowires due to their morphological reproducibility and innate proclivity to form well-ordered structures. Amongst the variety of naturally occurring nano-scale assemblies, cytoskeletal fibers from diverse biological sources represent a unique family of scaffolds for biomimetics as they efficiently self-assemble in vitro in a controllable manner to form stable filaments. Here, we harness the bacterial FtsZ filament system as a scaffold for protein-based metal nanowires, and further demonstrate the control of wire alignment with the use of an external magnetic field. Due to the ease at which the bacterial FtsZ is overexpressed and purified, as well as the extensive studies of its ultrastructural properties and physiological significance, FtsZ filaments are an ideal substrate for large-scale production and chemical manipulation. Using a biologically compatible electroless metal deposition technique initiated by adsorption of platinum as a surface catalyst, we demonstrate the coating of assembled FtsZ filaments with iron, nickel, gold, and copper to fabricate continuous nanowires with diameters ranging from 10-50 nm. Organic-inorganic hybrid wires were analyzed using high-resolution field-emission-gun transmission and scanning electron microscopy, and confirmed by energy-dispersive elemental analysis. We also achieved alignment of ferrofluid-coated FtsZ filaments using an external magnetic field. Overall, we provide evidence for the robustness of the FtsZ filament system as a molecular scaffold, and offer an efficient, biocompatible procedure for facile bottom-up assembly of metallic wires on biological templates. We believe that bottom-up fabrication methods as reported herein significantly contribute to the expanding toolkit available for the incorporation of biological materials in nano-scale devices for electronic and electromechanical applications.