Label-Free Electrochemical Detection for Aptamer-Based Array Electrodes

Abstract

An electrochemical impedance spectroscopy method of detection for aptamer-based array electrodes is reported in which the binding of aptamers immobilized on gold electrodes leads to impedance changes associated with target protein binding events. Human IgE was used as a model target protein and incubated with the aptamer-based array consisting of single-stranded DNA containing a hairpin loop. To increase the binding efficiency for proteins, a hybrid modified layer containing aptamers and cysteamine was fabricated on the photolithographic gold surface through molecular self-assembly. Atomic force microscopy analysis demonstrated that human IgE could be specifically captured by the aptamer and stand well above the self-assembled monolayer (SAM) surface. Compared to immunosensing methods using anti-human IgE antibody as the recognition element, impedance spectroscopy detection could provide higher sensitivity and better selectivity for aptamer-modified electrodes. The results of this method show good correlation for human IgE in the range of 2.5-100 nM. A detection limit of 0.1 nM (5 fmol in a 50-microL sample) was obtained, and an average of the relative standard deviation was <10%. The method herein describes the first label-free detection for arrayed electrodes utilizing electrochemical impedance spectroscopy.

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“…Because of their exceptionally high stability, selectivity and sensitivity, aptamerbased biosensor arrays have the potential to overcome the lacking functional and storage stability of most biosensors [34] . For example, an electrochemical impedance spectroscopy method of detection for aptamer-based electrochemical biosensor array (Figure 10) is reported in which the binding of aptamers immobilized on gold electrodes leads to impedance changes associated with target protein binding events by Xu et al [35] . Human IgE was used as a model target protein and incubated with the aptamer-based array consisting of single-stranded DNA containing a hairpin loop.…”