Elucidating the Influence of Electrical Potentials on the Formation of Charged Oligopeptide Self‐Assembled Monolayers on Gold

Abstract

Self‐assembled monolayers (SAMs) based on oligopeptides have garnered immense interest for a wide variety of innovative biomedical and electronic applications. However, to exploit their full potential, it is necessary to understand and control the surface chemistry of oligopeptides. Herein, we report on how different electrical potentials affect the adsorption kinetics, stability and surface coverage of charged oligopeptide SAMs on gold surfaces. Kinetic analysis using electrochemical surface plasmon resonance (e‐SPR) reveals a slower oligopeptide adsorption rate at more positive or negative electrical potentials. Additional analysis of the potential‐assisted formed SAMs by X‐ray photoelectron spectroscopy demonstrates that an applied electrical potential has minimal effect on the packing density. These findings not only reveal that charged oligopeptides exhibit a distinct potential‐assisted assembly behaviour but that an electrical potential offers another degree of freedom in controlling their adsorption rate.

Grafting of short elastin-like peptides using an electric field

“…Other studies have observed increases in packing density of a thioctic acid derivative when negative potentials were applied and suggested a potential-dependent surface reaction with no electron transfer was occurring 36 . Interestingly, in a highly related study of the adsorption of cysteine-terminated positively charged oligopeptides under similar AEF conditions (between − 0.4 V and + 0.3 V vs. Ag/AgCl) in PBS, the AEF had no impact on packing density 42 . Since our study is carried out in DI water instead of PBS, higher water coverage on the surface could cause some of the difference in adsorption behavior seen between this and the aforementioned work.…”

“…It is expected that the negative potential forces the (−)charged C-terminus to be oriented away from the gold surface while the cysteine-attached N-terminus is in contact with the gold surface. Electric fields have been shown to impact molecular orientation in simulations of alkanethiols on gold 45 , as well as experiments with charged oligopeptides 42 , 43 , 53 , 54 .…”

“…The result that a sufficiently high AEF directly impacts the hydrated mass loading as charged ELP is grafted to gold supports the premise that electric fields have the capacity to serve as an effective technique to control the loading and orientation designed peptides on solid surfaces by the attraction and repulsion of charged moieties. Experiments with peptides containing five positively charged lysine residues revealed that the electric field influenced orientation but not loading, likely due to the high charge repulsion of the many positively charged residues 42 . Our results indicate that the charge repulsion is possibly reduced when using one terminally located charge, thus minimizing the counteracting effect of charge repulsion observed in that study.…”

“…Electric fields have been used to control the assembly and grafting density of alkanethiol monolayers 32 – 36 , as well as biomolecules such as DNA 37 – 40 and peptides 41 – 44 . Recently, Gibson and Mendes demonstrated that an electric field influences the adsorption kinetics, orientation, and stability of charged oligopeptides on gold 42 . Specifically, it was shown that the presence of an electric field (positive or negative) slowed adsorption of a charged oligopeptide.…”