A strategy for covalent anchoring of self-assembling β3 oligoamide nanorods to gold surfaces

Abstract

Oligopeptides stand out for their remarkable structural variability, ease of synthesis, and amenability to functionalization, making them exceedingly appealing for crafting functional nanostructured materials. The low metabolic stability of natural peptides can be overcome by replacing α-amino acids with β3- amino acids, to yield artificial peptides best described as substituted β3-oligoamides. Controlling the morphology of such structures by varying the amino acid residues and altering the oligoamide termini makes it possible to adapt the core design to a range of hierarchical structures and function. Conductivity is a desired property in such nanomaterials; preferably conductive materials should be chemically anchored to a highly conductive metal, such as gold surface to connect to macroscopic electronics. It is preferable to use thiol functionality, however β3 cysteine is not synthetically achieveable. In this study β3 [SLIA] oligoamide has been synthesized and functionalized at the N terminus with a thiol moiety. After successful synthesis and purification, the thiolated oligoamide was physically characterized to confirm binding to gold, self-assembly and hetero assembly on these anchor points. It was demonstrated with a quartz crystal microbalance (QCM) that self-assembling monolayers can be formed on a gold surface and the formation of a S-Au bond was confirmed with X-ray photoelectron spectroscopy. Growth of Ac-β3[WKLWEL] fibres on these anchor points was confirmed by using atomic force microscopy and QCM. Hence, a viable metal anchor has been established that lays the foundations for the future development of molecular electronics based on β3 oligoamides.

Keywords

• substituted oligoamide
• gold binding
• self-assembly
• hetero-assembly