Quantifying nisin adsorption behavior at pendant PEO layers

Abstract

The antimicrobial peptide nisin shows potent activity against Gram-positive bacteria including the most prevalent implant-associated pathogens. Its mechanism of action minimizes the opportunity for the rise of resistant bacteria and it does not appear to be toxic to humans, suggesting good potential for its use in antibacterial coatings for selected medical devices. A more quantitative understanding of nisin loading and release from polyethylene oxide (PEO) brush layers will inform new strategies for drug storage and delivery, and in this work optical waveguide lightmode spectroscopy was used to record changes in adsorbed mass during cyclic adsorption-elution experiments with nisin, at uncoated and PEO-coated surfaces. PEO layers were prepared by radiolytic grafting of Pluronic® surfactant F108 or F68 to silanized silica surfaces, producing long- or short-chain PEO layers, respectively. Kinetic patterns were interpreted with reference to a model accounting for history-dependent adsorption, in order to evaluate rate constants for nisin adsorption and desorption, as well as the effect of pendant PEO on the lateral clustering behavior of nisin. Nisin adsorption was observed at the uncoated and F108-coated surfaces, but not at the F68-coated surfaces. Nisin showed greater resistance to elution by peptide-free buffer at the uncoated surface, and lateral rearrangement and clustering of adsorbed nisin was apparent only at the uncoated surface. We conclude peptide entrapment at the F108-coated surface is governed by a hydrophobic inner region of the PEO brush layer that is not sufficient for nisin entrapment in the case of the shorter PEO chains of the F68-coated surface.

Structural attributes affecting peptide entrapment in PEO brush layers

“…PEO brush layers with good steric-repulsive function are expected to form at chain densities greater than about 0.2 chains/nm 2 [17]. Adoption of a brush configuration by the methods used here was evident by their excellent fibrinogen repulsion as we have described elsewhere [18]. Hydrophobic control sensors were prepared as described above, but in the absence of F108.…”

Concentration effects on peptide elution from pendant PEO layers

“…Electrostatic repulsion by the positively-charged Arg residues on the solvent-exposed helix face would make formation of coiled-coil structures unfavorable, even if the peptide surface density were high. However, peptides which are entrapped within a PEO brush apparently do not directly interact with the underlying surface [23]. Thus, WLBU2 peptides entrapped in a PEO brush still form highly-charged coiled-coil structures, with low resistance to elution, at sufficiently high surface density.…”

“…200 μL of TCVS was evaporated at 20 °C into a stream of dry nitrogen carrier gas, which was directed over the sensor surfaces for 4 h. The silanized, hydrophobic sensors were then incubated overnight with 5% Pluronic® F108 in water, and then γ-irradiated to 0.3 Mrad to covalently attach the F108 to the surface [21, 23]. The irradiated sensors were rinsed with water, dried with nitrogen, and stored in the dark to avoid oxidation of the vinyl moieties.…”

Effect of PEO coating on bubble behavior within a polycarbonate microchannel array: A model for hemodialysis

“…The complex nature of the PEO brush layer becomes more significant when the coating is utilized in the presence of blood, which contains cells, proteins, and other constituents that will interact with or be repelled by the brush layer. 36,37 To complete the simulation "picture" of the two-phase bubble-flow phenomena in microchannels, it may be necessary to incorporate the entire microchannel array and additional coating effect components into future simulations involving blood or other complex fluids. We are encouraged by our current simulation results and see promising potential for the LBM method to incorporate more surface complexity with a level of flexibility and transparency above classical computational fluid dynamics.…”