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The thermodynamics of irreversible nonspecific protein adsorption at a solid-aqueous interface

University of British Columbia

Nonspecific adsorption of protein to interfaces is pervasive in nature and has both positive and negative consequences which are of interest to scientists and engineers. Previous studies on protein adsorption have indicated that adsorption is driven by a complex set of subprocesses rather than a single effect, and that the overall process is usually irreversible as verified by the lack of traceability between the ascending isotherm (increasing bulk protein concentration) and the descending isotherm (decreasing bulk protein concentration). These irreversible energetic effects have been neglected in current models describing protein adsorption which are entirely based on reversible thermodynamics. The objective of this thesis is to develop a thermodynamic framework describing the energies associated with nonspecific adsorption of protein to a liquid/solid interface, incorporating both the apparently reversible (quasi-equilibrium) and irreversible components of the process. To demonstrate the theory, a model system was chosen: the adsorption of hen egg-white lysozyme, to particulate silica in 50-rnM KC1 at pH 7 and 37°C. Isothermal titration calorimetry, differential scanning calorimetry and isotherm measurements are combined with our thermodynamic framework and a theory by Everett to show that two major subprocesses, restructuring of the protein upon adsorption and formation of multiple contacts between the protein and sorbent surface, are the major contributors to the irreversibility of the process.

Thesis/Dissertation

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2009-03-12

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http://hdl.handle.net/2429/5969

Chemical and Biological Engineering

University of British Columbia

UBCV

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