Influence of Immobilization Strategies on the Antibacterial Properties of Antimicrobial Peptide-Chitosan Coatings

Abstract

It is key to fight bacterial adhesion to prevent biofilm establishment on biomaterials. Surface immobilization of antimicrobial peptides (AMP) is a promising strategy to avoid bacterial colonization. This work aimed to investigate whether the direct surface immobilization of Dhvar5, an AMP with head-to-tail amphipathicity, would improve the antimicrobial activity of chitosan ultrathin coatings. The peptide was grafted by copper-catalyzed azide-alkyne cycloaddition (CuAAC) chemistry by either its C- or N- terminus to assess the influence of peptide orientation on surface properties and antimicrobial activity. These features were compared with those of coatings fabricated using previously described Dhvar5-chitosan conjugates (immobilized in bulk). The peptide was chemoselectively immobilized onto the coating by both termini. Moreover, the covalent immobilization of Dhvar5 by either terminus enhanced the antimicrobial effect of the chitosan coating by decreasing colonization by both Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria. Relevantly, the antimicrobial performance of the surface on Gram-positive bacteria depended on how Dhvar5-chitosan coatings were produced. An antiadhesive effect was observed when the peptide was grafted onto prefabricated chitosan coatings (film), and a bactericidal effect was exhibited when coatings were prepared from Dhvar5-chitosan conjugates (bulk). This antiadhesive effect was not due to changes in surface wettability or protein adsorption but rather depended on variations in peptide concentration, exposure, and surface roughness. Results reported in this study show that the antibacterial potency and effect of immobilized AMP vary greatly with the immobilization procedure. Overall, independently of the fabrication protocol and mechanism of action, Dhvar5-chitosan coatings are a promising strategy for the development of antimicrobial medical devices, either as an antiadhesive or contact-killing surface.

Medical Device-Associated Healthcare Infections: Sterilization and the Potential of Novel Biological Approaches to Ensure Patient Safety

“…The derivative Mel4 displayed antimicrobial activity and no eye toxicity in test rabbits in vivo for up to 7 days [ 87 ]. Studies describe the increased anti-adhesion activity of AMP bounded chitosan, compared to free chitosan in film coatings against Gram-positive bacterial species [ 88 ]. Research on an immobilized peptoid AMP mimic, with a polymer tether against pathogens, including P. aeruginosa and S. aureus , demonstrated surface antimicrobial activity and reduced bacterial attachment [ 85 ].…”

“…The coating or immobilization of medical device/biomaterial surfaces with AMPs has demonstrated anti-adhesion, anti-colonization, and antibiofilm formation action [ 81 ]. Furthermore, immobilization of AMPs has numerous advantages in vivo, including reduced cytotoxicity, enhanced stability, and prevention of protein binding [ 88 ]. The studies of Nielsen et al, 2022 describe the antibacterial and antibiofilm activity of self-assembling AMP peptoids against ESKAPE pathogens [ 80 ].…”

“…Contact between an immobilized AMP and microbial species is a consideration for surface coatings, where contact with cell membranes is typically required for inactivation. The efficacy and mode of action of immobilized AMPs differ from that of soluble AMPs and are influenced by exposure, density, orientation, immobilization technique, and type of biomaterial [ 88 ]. A range of solid surfaces have been successfully modified with AMPs, including polymers, titanium, gold, stainless steel, and glass [ 69 ].…”