BIOSENSORS BASED ON RECEPTORS : BIOSENSOR BASED ON A SUGAR TRANSPORT PROTEIN

Abstract

The bacterial membrane protein lactose-permease transports lactose across the cell membrane in symport with a proton. For application in a biosensor, the protein is reconstituted in planar lipid membranes spread on a glass surface. In the space between the membrane and the glass surface a pH-sensitive fluorescence dye is entrapped. When lactose is added to the external medium, a change in the fluorescence signal is detected which permits to determine the external lactose concentration. Synthetic lipopeptides are immunologically active compounds with low molecular mass and biophysically interesting properties. They have a potential for the immobilization of antigens on transducer surfaces. Fluorescence-labelled and non-labelled lipopeptides can be obtained by solid phase peptide synthesis. A new synthetic route for lipopeptides with C-terminallipid part is described which allows the N-terminal coupling of marker molecules. An antigenic partial sequence of a foot-and-mouth disease virus protein has been used to study the localisation of antibody binding to the lipopeptide. Lipid bilayers are examined by non-destructive spectral ellipsometry which yields information about their stability, thickness and structure. Diode arrays allow the spectral fluorescence and reflectance measurementsof antigen-antibody interactions. Binding of antibodies alters the thickness of the active film and the refractive indices in the sensing interface. Both effects are monitored by spectral interferometry as a new approach to label-free immuno-sensors. Immunosensorsand biosensors based on transport proteins using electrical transducer principles are discussed. Characteristic capacitance and voltage changes due to membrane coatings on electrolyte/TagzOs/SiO2Si(ETOS) structures were investigated. The layer arrangement of these structures is similar to those used in ourion sensitive field effects transistors (ISFETs).