(311g) Evaluating Free Energy Changes during Protein Adsorption Processes

Surface resistance to protein adsorption is a key design requirement for applications ranging from marine coatings to biomedical devices and sensors. While a variety of materials that resist protein adsorption exist, the mechanisms are not well understood. Furthermore, non-fouling surfaces frequently losses stability over time. By developing a better understanding of the mechanism of current non-fouling materials, like oligo-(ethylene glycol) or phosphorocoline groups, we can lay a foundation for rational design of new, more stable non-fouling materials.

Our group has done significant work to quantify the resistant forces that non-fouling surfaces generate on proteins and the resulting hydration structure and dynamics. However, the true thermodynamic criterion of protein adsorption or resistance is the change in free energy as the protein approaches the surface. In this work, molecular simulations and adsorption experiments were used to model and measure the free energy changes as model peptides in solution approach surfaces of varying non-fouling ability. By using both simulations and experimental techniques we were able to directly evaluate the validity of our simulations, as well as evaluate the relative influence of the surface and the hydrating water on the free energy changes. This paired approach provides feedback on our simulation parameters as well as a deeper understanding of the mechanism involved in protein resistance and adsorption.

As the mechanism of protein adsorption and resistance is better understood it opens the door to rational material design based directly on molecular function. By combining molecular simulations and experimental techniques, we are able to develop a fundamental description of the interactions present at both the molecular and macro scale. This fundamental understanding then opens to door to direct rational design of novel non-fouling materials.