TY - GEN A1 - Riepl, Michael A1 - Mirsky, Vladimir M. A1 - Novotny, Ivan A1 - Tvarozek, Vladimir A1 - Rehacek, Vlastimil A1 - Wolfbeis, Otto S. T1 - Optimization of capacitive affinity sensors: drift suppression and signal amplification T2 - Analytica Chimica Acta N2 - The detection limit of capacitive affinity sensors based on the gold–alkanethiol system can be improved by optimization of sensor preparation and by signal amplification. The dissociation of the gold–sulfur binding is often a critical point leading to operative errors of such sensors. The stability of self-assembled monolayers prepared with different thiols on gold electrodes in aqueous and organic solvents was studied by the capacitive technique. The results show that monolayers made of 16-mercaptohexadecanoic acid are stable in aqueous solution and can be hardly extracted from a gold surface by ethanol, methanol, or dioxane, while a considerable damage of self-assembled monolayers was observed due to incubation in chloroform or dimethylformamide. In contrast, self-assembled monolayers made from short-chain disulfides or thiols (such as 3,3′-dithio-bis(propionic acid N-hydroxysuccinimide ester) or 11-mercaptoundecanoic acid) displayed a poor stability in aqueous phase. Capacitive affinity sensors based on these short-chain thiols showed a considerable drift of the signal. The use of long-chain thiols resulted in a stable signal; it was applied to compare capacitive effects due to immobilization of different biological molecules and for preparation of different biosensors. The response of capacitive biosensors can be amplified by formation of a sandwich structure. This principle was illustrated by subsequent adsorption of polyclonal anti-HSA after binding of HSA with a sensor for HSA based on monoclonal antibodies. KW - Affinity sensor KW - Self-assembly KW - Capacitive sensor KW - Signal amplification KW - Immunosensor KW - Biosensor Y1 - 1999 U6 - https://doi.org/10.1016/S0003-2670(99)00195-6 SN - 0003-2670 VL - 392 IS - 1 SP - 77 EP - 84 ER -