4.8 Article

Interplay of Effective Surface Area, Mass Transport, and Electrochemical Features in Nanoporous Nucleic Acid Sensors

Journal

ANALYTICAL CHEMISTRY
Volume 92, Issue 15, Pages 10751-10758

Publisher

AMER CHEMICAL SOC
DOI: 10.1021/acs.analchem.0c02104

Keywords

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Funding

  1. National Science Foundation [CBET-1512745, CBETDMR-1454426]
  2. National Institutes of Health [R21-EB024635, R21-AT01093]
  3. University of California.Davis Comprehensive Cancer Center and Microbiome Special Research Program funds

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Electrochemical biosensors transduce biochemical events (e.g., DNA hybridization) to electrical signals and can be readily interfaced with electronic instrumentation for portability. Nanostructuring the working electrode enhances sensor performance via augmented effective surface area that increases the capture probability of an analyte. However, increasing the effective surface area via thicker nanostructured electrodes hinders the analyte's permeation into the nanostructured volume and limits its access to deeper electrode surfaces. Here, we use nanoporous gold (np-Au) with various thicknesses and pore morphologies coupled with a methylene blue (MB) reporter-tagged DNA probe for DNA target detection as a model system to study the influence of electrode features on electrochemical sensing performance. Independent of the DNA target concentration, the hybridization current (surrogate for detection sensitivity) increases with the surface enhancement factor (EF), until an EF of similar to 5, after which the sensor performance deteriorates. Electrochemical and fluorometric quantification of a desorbed DNA probe suggest that DNA permeation is severely limited for higher EFs. In addition, undesirable capacitive currents disguise the faradaic currents from the MB reporter at larger EFs that require higher square wave voltammetry (SWV) frequencies. Finally, a real-time hybridization study reveals that expanding the effective surface area beyond EFs of similar to 5 decreases sensor performance.

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