DEVELOPMENT OF AMPEROMETRIC AND MICROGRAVIMETRIC IMMUNOSENSORS AND REVERSIBLE IMMUNOSENSORS USING ANTIGEN AND PHOTOISOMERIZABLE ANTIGEN MONOLAYER ELECTRODES

Antigen monolayers assembled onto Au-electrodes or Au-electrodes assoc iated with quartz crystals act as active interfaces for the amperometr ic or microgravimetric analysis of the complementary antibody and prov ide the grounds for the development of electrochemical and piezoelectr ic immunosensors. The antigen monolayer of N epsilon-2,4-dinitrophenyl -L-lysine is assembled on an electrode. The anti-dinitrophenyl antibod y, anti-DNP-Ab, is sensed by the antigen monolayer, and the formation of the antigen-antibody complex at the monolayer interface is probed b y the insulation of the electrode toward a redox probe in the electrol yte solution. The formation of the antibody-antigen complex is amplifi ed by the application of the anti-antibody or the use of a ferrocene-f unctionalized redox-enzyme, glucose oxidase, as redox probe. A 3,5-din itrosalicylic acid antigen monolayer bound to An-electrodes associated with a quartz crystal is used as active interface for the microgravim etric, quartz-crystal-microbalance analysis of the anti-DNP-Ab. Photoi somerizable antigen monolayer electrodes provide the basis for tailori ng reversible immunosensors. The dinitrospiropyran monolayer, SP-state , is assembled on Au-electrodes or quartz crystals. The monolayer exhi bits reversible photoisomerizable features, and irradiation of the SP- monolayer, 360 < lambda < 380 nm, yields the protonated merocyanine mo nolayer, MRH+-state. Further irradiation of the MRH+-monolayer electro de, lambda > 495 nm, restores the SP-monolayer electrode. The SP-monol ayer acts as antigen for anti-DNP-Ab, whereas the MRH+-monolayer lacks antigen properties for anti-DNP-Ab. This enables the amperometric or piezoelectric transduction of the formation of the antigen-anti-DNP-Ab complex at the SP-monolayer interface. By photoisomerization of the m onolayer to the MRH+-slate, the Ab is washed-off from the sensing inte rface. Subsequent light-induced isomerization of the monolayer to the SP-state regenerates the electrochemically or piezoelectrically active sensing interfaces.