Synergy on Surfaces: Anti-Biofouling Interfaces Using Surface-Attached Antimicrobial Peptides PGLa and Magainin-2

The synergistic effect of antimicrobial compounds is an important phenomenon that can increase the potency of treatment and might be useful against the formation of biofilms on surfaces. A strong inhibition of microbial viability on surfaces can potentially delay the development of biofilms on treated surfaces, thereby enhancing the performance of water-purification technologies and medical devices, for example, to prevent hospital-acquired infections. However, the synergistic effects of surface-immobilized antimicrobial peptides (AMPs) have not yet been reported. Here, we demonstrate the synergistic antimicrobial effects of the AMPs PGLa and magainin-2 on modified reverse-osmosis (RO) membranes. These AMPs are known to act synergistically in the free state, but their antimicrobial synergistic effects have not yet been reported in a surface-immobilized state. The AMPs were functionalized with alkyne linkers and covalently attached to RO membranes modified with azides, using a click chemistry reaction. The resulting RO membranes showed reduced contact angles, indicating increased wettability. X-ray photoelectron spectroscopy confirmed the presence of the two peptides on the membranes via changes in the amounts of carbon, oxygen, and sulfur, which led to an increased S/C ratio, probably because of the sulfur present in the methionine residue of the peptides. The synergistic activity was measured with the free peptides in solution and covalently bound on RO membrane surfaces by observing increased leakage of 5(6)-carboxyfluorescein from large unilamellar vesicles. The synergistic antimicrobial activity against Pseudomonas aeruginosa was observed using surface-activity assays, where the AMP-modified RO membranes showed an effective inhibition of P. aeruginosa biofilm growth, as compared with unmodified membranes. An enhanced activity of antimicrobials on surfaces might lead to potent antimicrobial surfaces, which could result in more fouling-resistant water-treatment membranes.