Mode of Action of Cationic Antimicrobial Peptides Defines the Tethering Position and the Efficacy of Biocidal Surfaces

Abstract

Covalent immobilization of cationic antimicrobial peptides (CAPs) at sufficient density and distance from the solid matrix has been suggested as a successful strategy for the generation of biocidal surfaces. To test the hypothesis that the mode of peptide action is decisive for the selection of an appropriate tethering position on solid surfaces, melittin (MEL), a channel-forming peptide, buforin 2 (BUF2), a peptide able to translocate bacterial membranes without permeabilization and targeting nucleic acids, and tritrpticin (TP), described to be membrane-lytic and to have intracellular targets, were C- and N-terminally immobilized on TentaGel S NH(2) resin beads as model surface. The peptide termini were modified with aminooxyacetic acid (AOA) and coupled via oxime-forming ligation. The comparison of the activities of the three peptides and their AOA-modified analogues with a KLAL model peptide which permeabilizes membranes by a so-called "carpet-like" mode provided the following results: The peptides in solution state were active against Bacillus subtilis and Escherichia coli at micromolar concentrations. MEL and TP but not BUF2-derived peptides permeabilized the inner and outer membrane of E. coli and enhanced the permeability of lipid bilayers at concentrations around their antimicrobial values (MICs). Immobilization reduced peptide activity to millimolar MICs. The activity reduction for KLAL was independent of the tethering position and comparably low, as reflected by a low ratio of MIC(tethered)/MIC(free). In contrary, the pore-forming MEL was much less active when immobilized at the N-terminus compared with the C-terminally tethered peptide. C- and N-terminal TP tethering caused an identical but much pronounced activity decrease. The tethered BUF2 peptides were inactive at the tested concentrations suggesting that the peptides could not reach the intracellular targets. In conclusion, membrane active peptides seem to be most suitable for the generation of antimicrobial surfaces, but knowledge about their mode of membrane insertion and positioning is required to identify optimal tethering positions. The relationship between the mechanism of action and position of immobilization is highly relevant for the establishment of a general approach to obtain efficient biocidal solid matrices loaded with CAPs.

Dhvar5 antimicrobial peptide (AMP) chemoselective covalent immobilization results on higher antiadherence effect than simple physical adsorption

“…Nevertheless, reports diverge in their general conclusion about the specific characteristics of the applied spacer, suggesting that it may be peptide-dependent. More recently, Bagheri et al [36], tried to assess whether the mechanism of action of soluble AMP could be relevant for the correct configuration of immobilization. To that end, those authors chose different AMP with distinct putative mechanisms of action, and tested them after different tethering approaches.…”

New trends in peptide-based anti-biofilm strategies: a review of recent achievements and bioinformatic approaches

“…The type of mechanism of action of AMPs can dictate their application fields. For example, it has been noticed that AMPs targeted at the membrane are better suited for use in surface coatings than AMPs that act at an intracellular level (Bagheri et al 2012).…”

pH Dependence of Microbe Sterilization by Cationic Antimicrobial Peptides

“…An interesting possibility is the use of tethered CAMPs in surgical applications attached, perhaps in a slow-release form (18), to the surface of artificial joints and implants (19)(20)(21). Despite having been studied for over 30 years, the clinical use of CAMPs is still limited.…”