Bactericidal Activity of Surface Immobilized Antimicrobial Peptides

Substrates with antimicrobial functionality have many potential uses including medical devices, food safety, decontamination and prevention of materials degradation.  Currently used antimicrobial agents such as metals, chloramines and quaternary ammonium compounds have a biochemical mode of action that may lead to increased bacterial resistance after prolonged use.  In contrast, the physical mode of action of antimicrobial peptides (AMPs) is not expected to induce resistance.  AMPs incorporated into polyurethane films and coatings exhibited antibacterial activity. After washing, films lost activity while coated glass fiber filters remained active. Peptide leaching is required for activity, limiting the length of time the polymer retained functionality.   To address this limitation, the activity of AMPs covalently-attached to amine functionalized surfaces was examined.  As proof of concept, AMPs were attached to magnetic beads.  Activity against both Gram-positive and Gram-negative bacteria including Acinetobacter baumannii, Bacillus anthracis sterne and Staphylococcus aureus has been demonstrated.  Potency was cell–dependent; however, the peptides exhibited activity for all organisms in a dose-dependent manner, reaching a critical concentration that inhibited growth completely.  A combination of increased concentration and longer exposure time was required for activity compared to peptides in solution.  SMAP immobilized to a glass exhibited activity against E. coli and S. aureus.  A greater amount of peptide required to exhibit antibacterial behavior than was needed on magnetic beads. We have demonstrated that antimicrobial functionality can be imparted to surfaces through covalent attachment of AMPs.  The research presented here lays the foundation for a new generation of non-leaching antimicrobial treatments.