Peptides as potent antimicrobials tethered to a solid surface: Implications for medical devices

Abstract

Medical devices are an integral part of therapeutic management; despite their importance, they carry a significant risk of microbial infection. Bacterial attachment to a medical device is established by a single, multiplying organism, leading to subsequent biofilm formation. To date, no preventative measures have impacted the incidence of device-related infection. We report the bidirectional covalent coupling of an engineered cationic antimicrobial peptide (eCAP), WLBU2, to various biological surfaces is accomplished. These surfaces included (i) a carbohydrate-based gel matrix, (ii) a complex polymeric plastic bead, and (iii) a silica-calcium phosphate nanocomposite associated with bone reconstruction. WLBU2-conjugated surfaces are shown to retain potent antimicrobial activity related to bacterial surface adhesion. This study provides proof of principle that covalently coating laboratory and bone-regenerating materials with eCAPs has the potential for decreasing infection rates of implanted devices. These findings have important consequences to the patient management component of our current health care technology.

Binding interactions of bacterial lipopolysaccharide and the cationic amphiphilic peptides polymyxin B and WLBU2

“…However the 24-residue, de novo engineered peptide WLBU2, a synthetic analogue of LL-37, shows highly selective, potent activity against a broad spectrum of Gram-positive and Gram-negative bacteria at physiologic NaCl and serum concentrations of Mg 2+ and Ca 2+ [23-26]. Moreover WLBU2 shows greater antimicrobial activity than either LL-37 or PmB, and is active against a much broader spectrum of bacteria [27, 28]. …”

“…The propensity for α -helix formation in cell membranes correlates positively with CAP activity and selectivity of bacterial over human cells, and WLBU2 has been optimized specifically for formation of an amphipathic α -helix conformation in cell membranes[23-25, 28]. Finally, in addition to its broad-spectrum antimicrobial activity in blood, WLBU2 retains potency while bound to solid surfaces[14, 26, 27, 29, 30] and importantly, shows high affinity for adhesion of susceptible bacteria [27]. …”

Sequential and competitive adsorption of peptides at pendant PEO layers

“…The structure of WLBU2 in water is substantially disordered, but the peptide gains considerable secondary structure, involving segregation of its positively-charged and hydrophobic groups onto opposing faces of an α -helix, in the presence of counterions, membrane-mimetic solvents, or bacterial membranes and lipopolysaccharides. Moreover, WLBU2 retains its antimicrobial activity when immobilized at solid surfaces by a number of methods [4, 8-10]. For controlled comparison of amphiphilic effects on WLBU2 adsorption, we also used a peptide chemically identical to WLBU2 but of scrambled sequence (S-WLBU2).…”

Concentration effects on peptide elution from pendant PEO layers

“…The structure of WLBU2 in water is substantially disordered, but the peptide gains considerable secondary structure, involving segregation of its positively-charged and hydrophobic groups onto opposing faces of an α -helix, in the presence of counterions, membrane-mimetic solvents, or bacterial membranes. Moreover, WLBU2 retains its antimicrobial activity when immobilized at solid surfaces by a number of methods [2, 6-8]. While chemically identical to WLBU2, the scrambled sequence of S-WLBU2 eliminates the ordered segregation of positively-charged and hydrophobic residues of WLBU2 during helix formation (Figure 1), and is associated with a very low hydrophobic moment in comparison to WLBU2 (0.1 vs. 10.7, respectively).…”