AVS 51st International Symposium
    Biomaterial Interfaces Monday Sessions
       Session BI-MoA

Paper BI-MoA3
Approach Towards Protein Adsorption, Desorption and Exchange

Monday, November 15, 2004, 2:40 pm, Room 210D

Session: Protein-Surface Interactions
Presenter: M. Halter, ETH Zurich, Switzerland
Authors: M. Halter, ETH Zurich, Switzerland
G. Szöllösi, Eötvös University, Hungary
I. Derényi, Eötvös University, Hungary
J. Vörös, ETH Zurich, Switzerland
Correspondent: Click to Email
When an artificial object is introduced into a biological environment, its surface is covered almost instantly with a protein layer. Being such a crucial issue for any biological application, the processes involved in protein adsorption, desorption and exchange are still not fully understood. Many controversial theories about the reversibility or irreversibility of protein adsorption, whether an adsorbed layer is static or forming a dynamic equilibrium and other puzzles and paradoxes exist. We present a realistic model for protein adsorption that can adequately describe the observed experimental data, such as irreversibility, history dependence, or the Vroman effect. A novel instrument, the Single Channel Grating Coupler, was used to provide new insight into protein behavior at interfaces. It is a planar waveguide technique that uses the evanescent field generated by an incoupled laser beam. Fluorescently labeled proteins within this field are excited and emit a fluorescent signal. The major advantages of this instrument are its high sensitivity (lower detection limit < 10 fmol/cm@super 2@) and the possibility to measure protein exchange by varying the labeled to unlabeled protein ratio in a solution. In situ measurements of interfacial exchange reactions provide sufficient data to develop a sophisticated protein adsorption model. It assumes that each protein molecule has several different conformations in the adsorbed state with different footprint sizes and binding energies, separated by energy barriers. Numerical simulations of large numbers of proteins - supplemented by analytical calculations - allow us to reproduce the experimental data and identify the conformations of proteins. Such a model will hopefully lead to a better understanding of protein behavior at interfaces. Beyond this, knowledge of the processes involved will help to tune the important parameters to build up and control adsorbed protein layers as desired for specific applications.