Aptamers have been employed as the biorecognition element in electrochemical aptamer-based (E-AB) biosensors, for the detection of a diverse range of analyte molecules, on electrodes with size scales ranging from a few microns to several millimeters. Simultaneous detection of multiple different analytes using E-AB sensors requires the selective modification of multiple electrode surfaces with different aptamers. This process is typically achieved by incubating separate electrodes in a solution with the desired aptamer, which is unsuitable for microelectrode arrays in which the electrodes are closely spaced. In this work, we selectively modified electrode surfaces with thiolated aptamers of different single-stranded DNA sequences, by controlling the potential applied to gold electrodes. All aptamers were methylene blue terminated, allowing redox currents to be measured and used to monitor probe packing density of the aptamer on the electrode surface and the selectivity of the sensor. Using multiple aptamer-based sensors in solutions containing numerous analytes enabled an increase in selectivity. Negative potentials were shown to decrease the aptamer probe packing density, in which the desired packing density could be obtained through desorption of the aptamer monolayer or by applying potentials during the aptamer incubation process. Using this method, an aptamer of one sequence was adsorbed onto the electrode surfaces, followed by complete removal by desorption at a sufficiently negative potential. The same surface could then be modified with another aptamer sequence, enabling multiple different aptamers to be used on the surfaces of closely spaced microelectrodes. Here, we demonstrate a newly developed E-AB sensor multianalyte detection method using aptamers for target analytes, adenosine triphosphate, dopamine, and serotonin, that can ultimately be applied to perform localized simultaneous detection using electrode arrays.

Electrode potential control for selective aptamer modification of gold surfaces for simultaneous multiple analyte detection

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ACS Fall 2022

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