Controlled release of proteins from polymer-modified surfaces.

The ability to control the rate of adsorption and desorption of proteins from surfaces is studied by using a molecular theory. We show how changing the chemical structure and charge of short linear and branched grafted polymers to an electrode surface can be used to promote fast adsorption of charged proteins on a time scale of seconds and control the desorption in a time scale ranging from milliseconds to hours. The optimal controlled release is found from the interplay of electrostatic attractions at short distances from the surface and the proper electrostatic and steric repulsive barrier at distances from the surfaces larger than the proteins' size. The implications of our results to the design of controlled-release devices is discussed.