Instrumental improvements in optical waveguide light mode spectroscopy for the study of biomolecule adsorption

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Abstract
Optical waveguide light mode spectroscopy (OWLS) is a new technique that is particularly well suited to the in situ study of biomolecule adsorption kinetics on surfaces. Here we describe improvements to a commercial OWLS instrument in order to allow for easy combination with other ex situ surface-characterization methods, such as x-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and atomic force microscopy. Further, the problem of contamination of the waveguide surface arising from the use of silicone in the flow-through cuvette with which biomolecules are brought into contact with the adsorbing surface had to be resolved, as it greatly altered the wetting and adsorption properties of the waveguide. Finally, through physical vapor deposition of thin, nanosized layers of titanium oxide onto the waveguide layer, it is possible to simulate the surface properties of oxide-covered titanium implant surfaces. However, scanning angle constraints set by the mechanics of the commercial instrument must be borne in mind.