| The controlled placement of protein molecules onto surfaces represents a crucial step toward many new biotechnological devices and processes. An applied electric field offers a promising means of controlling the rate of adsorption to the surface and the structure of the adsorbed layer. A method for monitoring the time evolution of an adsorbed protein layer in the presence of an electric field is presented. In this work, Optical Waveguide Lightmode Spectroscopy (OWLS) is used to measure the mass and layer thickness of protein adsorbing onto an indium tin oxide (ITO) electrode. Over a range of applied potentials, a kinetic analysis of human albumin, cytochrome c, and apo-transferrin is performed to determine the affects of surface and protein charge and electrochemical properties of the electrode surface on the adsorption process. It is found that in the transport-limited regime an applied potential has a significant influence on the initial rate of adsorption of albumin, while cytochrome c and apo-transferrin are unaffected in this region. During the later stage of adsorption the density of each of the three proteins tested is considerably enhanced by the presence of an applied electric field. This enhancement is found to be independent of the net charge of the protein. |
