Selected Experiments with Proteins at Solid-Liquid Interfaces

Abstract

This thesis describes a number of novel experiments contributing to the understanding of protein adsorption from both a fundamental and applied perspective. The first three papers involve the use of the localized surface plasmon resonance of gold nanospheres to measure protein conformational dependencies during heat and acid denaturation. Thermal denaturation of BSA is shown to proceed differently depending on the size of nanosphere to which it is conjugated. Activation energies are extracted for thermal denaturing on nanoparticles. These energies decrease with decreasing radius of curvature. Under pH perturbation in the acid region, the multiple transition states of bulk BSA are suppressed, and only one apparent transition around pH 4 is evident. Smaller spheres (diameter < 20nm) do not exhibit any transition. A significant finding of all three studies is that the state and stability of BSA depends strongly upon local curvature. The last two papers investigate protein adsorption relevant to the biomaterial field. Investigation of protein adsorption to polyHEMA hydrogels is carried out using a quartz crystal microbalance. Single and mixed protein adsorption kinetics for BSA, lysozyme and lactoferrin are extracted and interpreted. Selected commercial cleaning solutions are shown to be no more effective than simple buffer solution. Examination of commercial lenses indicates that the morphology of adsorption is material dependent and that siloxane-based hydrogels only deposit low levels of protein. A unique fibril-like morphology is identified on galyfilcon A. Protein morphology is discussed in terms of bare lens morphology, roughness, and surface composition.