alpha-Aminoisobutyric Acid-Stabilized Peptide SAMs with Low Nonspecific Protein Adsorption and Resistance against Marine Biofouling

A series of low fouling peptide self-assembled monolayers (SAMs) was developed to understand how the effects of subtle sequence alterations determine the properties of peptide-terminated SAMs and settlement and adhesion of two model fouling organisms, the green alga Ulva linza and the diatom Navicula perminuta, and adsorption of two different proteins, fibrinogen and lysozyme. Insertion of the bulky, nonproteinogenic amino acid alpha-aminoisobutyric acid (Aib) was examined for how it affects the peptide surfaces and performance in the assays. By exchanging the serine (S) of the sequence (SGKGSSGSS) with alanine (A), we slightly altered the hydrophilicity and found reduced fouling by N. perminuta. The inclusion of Aib residues resulted in surface structural changes of the peptides from a mixture of beta-sheet/random coil to strictly random coil and a decrease in the overall packing density by about 17-37%. Notably, these changes had little effect on the ability of the surface to resist nonspecific adsorption of fibrinogen and lysozyme and attachment of N. perminuta. The sequences containing Aib were 50-84% better than without Aib against the settlement of the zoospore of U. linza. Furthermore, the inclusion of Aib helped to create peptides that were 100% resistant against enzymatic degradation by trypsin, whereas the peptides without Aib were 9.5% degraded after 4 h.