TitleQuantifying nisin adsorption behavior at pendant polyethylene oxide brush layers
Publication TypeThesis
Year of Publication2012
AuthorsDill, JK
UniversityOregon State University
CityCorvallis, Or.
Thesis TypeMasters Thesis

A more quantitative understanding of peptide loading and release from polyethylene oxide (PEO) brush layers will provide direction for development of new strategies for drug storage and delivery. 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. 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. Lateral rearrangement and clustering of adsorbed nisin was apparent on uncoated and F68-coated surfaces, but not on F108-coated surfaces. In addition, nisin showed greater resistance to elution by peptide-free buffer from uncoated and F68-coated surfaces. These results are consistent with shorter PEO chains allowing for peptide adsorption to the base substrate in the case of F68-coated surfaces, while adsorption to the F108-coated surfaces is apparently governed by the presence of a hydrophobic core within the brush layer itself. Further, these results suggest that while peptide location within the hydrophobic core provides stability against lateral rearrangement, the pendant PEO chains themselves provide no steric barrier to nisin rearrangement within the brush layer.