Low Fouling Peptides with an All (d) Amino Acid Sequence Provide Enhanced Stability against Proteolytic Degradation While Maintaining Low Antifouling Properties.

Peptide-functionalized surfaces, composed of optimized l-peptides, show a high resistance toward nonspecific adsorption of proteins. As l-peptides are known to be prone to proteolytic degradation, the aim of this work is to enhance the stability against enzymatic degradation by using the all d-peptide mirror image of the optimized l-peptides and to determine if the all d-enantiomer retains the protein-resistant and antifouling properties. Two l-peptides and their d-peptide mirror images, some of them containing the nonproteinogenic amino acid α-aminoisobutyric acid (Aib), were synthesized and tested against non-specific adsorption of the proteins lysozyme and fibrinogen and the settlement of marine diatom Navicula perminuta and marine bacteria Cobetia marina. Both the d-enantiomer and the insertion of Aib protected the peptides from proteolytic degradation. Protein resistance was enhanced with the d-enantiomers while maintaining the resistance toward diatoms.