Conducting nanowires built by controlled self-assembly of amyloid fibers and selective metal deposition

Abstract

Recent research in the field of nanometer-scale electronics has focused on the operating principles of small-scale devices and schemes to realize useful circuits. In contrast to established ''topdown'' fabrication techniques, molecular self-assembly is emerging as a ''bottom-up'' approach for fabricating nanostructured materials. Biological macromolecules, especially proteins, provide many valuable properties, but poor physical stability and poor electrical characteristics have prevented their direct use in electrical circuits. Here we describe the use of self-assembling amyloid protein fibers to construct nanowire elements. Self-assembly of a prion determinant from Saccharomyces cerevisiae, the N-terminal and middle region (NM) of Sup35p, produced 10-nm-wide protein fibers that were stable under a wide variety of harsh physical conditions. Their lengths could be roughly controlled by assembly conditions in the range of 60 nm to several hundred micrometers. A genetically modified NM variant that presents reactive, surfaceaccessible cysteine residues was used to covalently link NM fibers to colloidal gold particles. These fibers were placed across gold electrodes, and additional metal was deposited by highly specific chemical enhancement of the colloidal gold by reductive deposition of metallic silver and gold from salts. The resulting silver and gold wires were Ϸ100 nm wide. These biotemplated metal wires demonstrated the conductive properties of a solid metal wire, such as low resistance and ohmic behavior. With such materials it should be possible to harness the extraordinary diversity and specificity of protein functions to nanoscale electrical circuitry.

Self-assembled collagen-like peptide fibers as templates for metallic nanowires

“…32 For recombinant amyloid proteins, gold nanoparticles attached to the protein surface serve as nucleation sites to promote the electroless reduction of silver and gold enabling nanowire growth. Only one metal nanoparticle per 250 amino-acids was needed to create conductive nanowires.…”

“…Only one metal nanoparticle per 250 amino-acids was needed to create conductive nanowires. 32 Therefore, we expected treatment of our lysine-substituted peptides with amine-reactive gold nanoparticles, which will attach to amine functionalities at the N-terminus and lysine sidechain groups, followed by self-assembly under analogous conditions to yield nanoparticle decorated fibers suitable for nanowire growth from electroless silver plating. We found that self-assembly was not affected by this gold nanoparticle treatment as micrometer-long fibers could still be observed by TEM (Fig.…”

Hierarchical Self‐Assembly of One‐Dimensional Streptavidin Bundles as a Collagen Mimetic for the Biomineralization of Calcite

“…[1][2][3][4][5][6] In parallel to these developments, surfaces and cavities spanned by protein higher-order aggregates have been exploited for molecular encapsulation and for templating nanoparticle synthesis. Typical examples include protein fibrils, [7,8] ferritin, [9,10] S-layers, [11][12][13] antibodies, [14] peptide amphiphiles, [15] capsids, [16][17][18][19] leucine zippers, [20] etc. [21][22][23][24][25][26] Controlled protein aggregation is a critical process in many areas, ranging from biomineralization [27] to neurodegenerative diseases.…”

Direct Observation of Amyloid Nucleation under Nanomechanical Stretching

“…Furthermore, this nanofiber has potential to act as a template for nanoscale fabrication and core for nanoscale devices [6]. Therefore, it is important to understand the self-assembly process of amyloid.…”