Exploring potential of glass surface immobilized short antimicrobial peptide (AMP) as antibacterial coatings

Bacterial infections associated with biomedical devices and implants pose serious clinical threat to human health and medical sector. Antimicrobial peptides (AMPs) based coatings are promising candidate to prevent these infections due to broad spectrum antimicrobial activity, reduced bacterial resistance propensity, and low cytotoxicity. In this study, an in-house designed peptide, KLR (KLLLRLRKLLRR), is immobilized onto glass substrates and its antibacterial activity against E. coli and S. aureus is studied. The effect of orientation of the peptide on the antibacterial activity is also tested by tethering the peptide through its C-terminus, using EDC/NHS coupling, and N-terminus, using maleimide-thiol chemical coupling. To confirm successful modification in all the sequential steps, X-ray photoelectron spectroscopy (XPS), water contact angle (WCA) measurements, and atomic force microscopy (AFM) is used. Antibacterial assays reveal that peptide-modified surfaces exhibit excellent antibacterial activity against E. coli (Gram-negative bacteria) but were ineffective in inhibiting S. aureus (Gram-positive bacteria). Furthermore, confocal studies with dye encapsulated giant unilamellar vesicles (GUVs) show that immobilized KLR induces dye leakage from the vesicles indicating pore-forming action mechanism of immobilized peptide. These peptide coated surfaces exhibit no cytotoxicity towards mammalian cells. Thus, these short peptides can be synthesized easily and cost effectively, opening an opportunity to be new antibacterial surface coating agents.