Graduation date: 2007The adsorption and elution of the antimicrobial peptide nisin at hydrophobic, silanized silica surfaces coated with the poly[ethylene oxide]-poly[propylene oxide]- poly[ethylene oxide] surfactant Pluronic® F108 was measured in situ, with ellipsometry. While such layers are known to inhibit protein adsorption, nisin was observed to adsorb in multilayer quantities, to an extent similar to its adsorption at uncoated, hydrophobic surfaces. The rates of nisin adsorption and elution were generally slower at F108-coated surfaces. And, the sequential adsorption of nisin, including two adsorption-elution cycles at each surface, showed greater differences in adsorption rates between the first and second adsorption cycles, when evaluated at identical mass density, for uncoated relative to F108-coated surfaces. These results indicate that nisin adsorption occurs via entrapment within the PEO brush layer at F108-coated surfaces, in this way slowing adsorption and spontaneous elution, and inhibiting post-adsorptive molecular rearrangements by reducing the lateral mobility of nisin. While F108-coated layers rejected adsorption of serum albumin, sequential adsorption experiments carried out with nisin and albumin showed a low level of albumin adsorption when nisin was present at the interface. The activity of these nisin-loaded layers was evaluated in the presence and absence of blood proteins, after contact periods up to one week. While an increase in serum protein concentration reduced the activity of nisin retained on both the bare hydrophobic and F108-coated surfaces of these materials, the F108-coated surfaces retained more antimicrobial activity than the bare surfaces. These results support the notion that the pendant PEO chains of the F108 coating inhibited the exchange of nisin by blood proteins. F108-coated microspheres and polyurethane catheter segments were observed to retain more antimicrobial activity than their uncoated counterparts in the absence of blood proteins as well, but the difference in function between bare and F108- coated substrates was most pronounced in the presence of blood proteins. Circular dichroism spectroscopy studies conducted with nisin in the presence of F108-coated and uncoated, silanized silica nanoparticles suggested that nisin experienced conformational rearrangement at a greater rate and to a greater extent on bare hydrophobic relative to F108-coated surfaces.