# Antifouling Efficacy on S. epidermidis of Nano-Au Surfaces Functionalized with Polyethylene Glycol (PEG)-Tethered Antimicrobial Peptides

## TL;DR

Researchers found that attaching certain peptides to gold nanoparticles can create effective antibacterial coatings even when only part of a surface is covered.

## Contribution

The study reveals that cyclic antimicrobial peptides tethered to gold nanoparticles are more effective than linear ones in antifouling coatings.

## Key findings

- Antifouling efficacy increases exponentially with 2D surface coverage of PEG-tethered cAMPs.
- Cyclic cAMPs are significantly more potent than linear cAMPs after tethering to gold nanoparticles.
- PEG-brush shrinkage due to cyclic cAMP attachment may enable cooperative peptide actions on the surface.

## Abstract

Cationic antimicrobial peptides (cAMPs) kill bacteria
in solution
by membrane lysis; however, translating cAMPs into a covalently attached
antibacterial coating is challenging since it remains unclear how
the specifics of the conjugation impact the antifouling efficacy.
Furthermore, studies have typically assessed cAMP coatings with a
high and homogeneous surface coverage, although this may be difficult
to implement in practice of the materials commonly used in medicine.
Herein, we investigate the antifouling efficacy of fractional surface
coatings made from poly­(ethylene glycol) (PEG)-tethered cAMPs presented
on gold nanoparticles (AuNPs) deposited onto surfaces. For all tested
cAMPs, the antifouling efficacy increases exponentially with the 2D
surface coverage of the coating. However, although the cAMPs have
a similar primary sequence and display similar potency against Staphylococcus epidermidis in solution, the cyclic peptide
is much more potent after tethering to the AuNPs than the linear counterparts.
The attachment of the cyclic cAMPs also led to an unexpected shrinkage
of the modified PEG-brush by more than 50%, indicating a restricted
mobility of the tethering PEG chains. The shrinkage increased the
closeness of the peptide on the AuNP and may thus enable cooperative
actions of the grafted cAMPs such as the formation of nanosized peptide
clusters that were previously found to enhance cAMP potency in solution.
These findings pave the way for antibacterial coatings that cover
only a subfraction of a material while remaining active in a clinical
setting.