BIOSENSORS BASED ON RECEPTORS : OPTICAL TRANSDUCER PRINCIPLES

Abstract

Optical spectroscopy is a non-destructive method for characterizing biological layers and surfaces as well as for monitoring changes in concentrations of an analyte interacting with the layers (23,24,25,26). Knowledge about stability, thickness, and structure of the layer are prerequisites in the intention to optimize such systems with respect to biosensorfeasibility. Therefore, lipid bilayers using lactose-permease as a transport protein (s. chapter 1) and synthetic lipopeptide-antigens (s. chapter 2) were examined. Spectral ellipsometry (27) yields information about the interaction of polarized light with the biological membranesin addition to measurements of capacitance, conductivity, and molecular properties (s. chapter 4). Fluorescence and reflectance measurements dependent on time allow to monitor the dynamic processes of fluorescence quenching of a labelled antigen by a specific antibody. Furthermore, the interference of reflected beams can be applied to the examination of immuno-sensors. Spectral detection increases the amountof information and reduces the danger of artefacts. However, multi-wavelength detection by diode arrays lowers sensitivity and increases the experimental problems.