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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. [ABSTRACT FROM AUTHOR]

Infections and thrombus formation are major concerns for the success of blood‐contacting medical devices. Antimicrobial coatings based on antimicrobial peptides (AMPs) are described as promising strategies to fight biomaterial‐associated infections. However, their efficiency in the presence of plasma and their effect on platelets adhesion/activation, essential for blood contact applications, is not known. In this work, the AMP cecropin–melittin (CM) is covalently immobilized onto polyurethane (PU) films envisaging a coating for intravascular catheters. Immobilization is done by dip‐coating of a layer of gold nanoparticles (Au NPs) functionalized with NH2 and COOH terminated polyethylene glycol (PEG). Surfaces characterized using scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), quartz crystal microbalance with dissipation (QCM‐D), and colorimetric assays reveal a stable and homogeneous coating distribution. CM coating significantly reduces Staphylococcus epidermidis adhesion to PU films (≈80% in PBS). Its bactericidal activity is not affected in the presence of 1% human plasma (hPlasma) proteins with 65% reduction on viable bacteria comparing to PU. Moreover, CM coating is able to prevent platelet adhesion/activation to PU films (≈95% in PBS). This effect is also observed when surfaces are precoated with hPlasma. Overall, the developed antimicrobial coating demonstrates great potential to prevent bacterial infections on PU devices without instigating platelet adhesion/activation. In this work, a coating based on cecropin–melittin antimicrobial peptide is engineered for prospective applications in polyurethane catheters. The coating prevents Staphylococcus epidermidis adhesion, displaying as well bactericidal features. It is also effective against platelets adhesion and activation. Overall, the engineered coating shows excellent antibacterial activity and promising antithrombogenic properties. [ABSTRACT FROM AUTHOR]