The main goal of this work is to review total internal reflection ellipsometry (TIRE) with special focus on its advantages for monitoring protein adsorption. The idea behind TIRE is not new; the background theory can be found in textbooks (Azzam and Bashara 1987; Pedrotti and Pedrotti 1996). However, the lack of powerful computing devices required for ellip-sometric analysis has limited the development of TIRE (as well as its parent technique - ellipsometry) for quite a time. The situation has changed during recent decades, and TIRE has come to the attention of several scientists, who noticed its potential and advantages in many different areas of science (Bortchagovsky 1997; Okutani et al. 1998). Rekveld carried out some pioneering work using single-wavelength ellipsometry and a flow cell to study fibrinogen adsorption on titanium dioxide, but without sensitivity optimization (Rekveld 1997). Nowadays, depending on the application and experimental settings, TIRE can also be found under the names of internal reflection ellipsometry (IRE; Poksinski and Arwin 2004), (surface) plasmon enhanced ellipsometry ((S)PEE; Westphal and Bornmann 2002), or total reflection ellipsometry (TRE; Okutani et al. 1998). With enhancement of

Michal Poksinski, Hans Arwin: Laboratory of Applied Optics, Department of Physics, Chemistry and Biology, Linkoping University, SE-581-83 Linkoping, Sweden, E-mail: [email protected]

Principles and Practice Proteins at Solid-Liquid Interfaces Philippe Dejardin (Ed.) © Springer-Verlag Berlin Heidelberg 2006

the surface plasmon resonance (SPR) effect, this technique becomes powerful in the area of protein adsorption, where it is mostly used nowadays (Poksinski and Arwin 2004; Nabok et al. 2005). However, applications in other areas like liquid crystals (Okutani et al. 1998) and corrosion monitoring (Poksinski et al. 2003) are also of interest.

Development of measurement techniques in the area of protein adsorption is of special interest as it becomes more and more important to monitor proteins as close as possible to their natural environments. Interactions of different proteins with the surfaces of different materials are important to the scientific community (Caruso et al. 1997; Martensson et al. 1995; Tengvall et al. 1998). The TIRE technique is very attractive as it allows in situ studies of proteins adsorbed onto thin metal films, with a potential to provide the out-of-plane refractive index profile of the adsorbed material.

The objective of this work is to provide a general overview of the possible applications of TIRE for monitoring protein adsorption on thin metal films. The theoretical aspects of TIRE are presented in brief, followed by a description of experimental setups and examples of applications. Suggestions and comments about other possible applications are given at the end. More details regarding the theoretical aspects of TIRE, as well as sensitivity and accuracy considerations, can be found elsewhere (Arwin et al. 2004; Tompkins and Irene 2005; Poksinski and Arwin, unpublished data).

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