Interaction of Proteins with Spherical Polyelectrolyte Brushes

Spherical polyelectrolyte brushes are a novel class of carrier particles for the immobilization of proteins. These particles consist of a polystyrene core onto which long chains of polyelectrolytes are grafted. A high uptake of proteins can be achieved if the ionic strength is low, while both compounds carry an overall negative charge. No adsorption takes place at higher ionic strength. This thesis provides a deeper insight in the adsorption process of proteins onto polyelectrolyte brushes. Here, the kinetics of the adsorption process is investigated by the combination of time resolved small angle X-ray scattering and rapid stopped flow mixing. The adsorption kinetics was described experimentally and theoretically. Furthermore, the thermodynamics of the adsorption process was investigated by isothermal titration calorimetry. The combination of experimental finding and theoretical considerations identify the counterion release force as the main driving force for the adsorption. Counterions from the brush layer and the protein surface are released at low ionic strength and the free energy of the system will be decreased. Furthermore, the behavior of the proteins in the adsorbed state was investigated by the combination of several analytical techniques. These provide an in-depth understanding of the kinetic activity, the protein structure and the location of the adsorbed protein molecules in the polyelectrolyte layer.