Sensitive Electrochemical Detection of Nucleic Acids Following Electrokinetic Enrichment in a Bed of Bioconjugated Beads for Point-of-Care Testing
Thursday, March 11, 2021: 2:50 PM - 3:25 PM
Sensors that leverage the influence of a biorecognition event on charge transport, such as field-effect transistors and nanoporous membranes, are among the most sensitive because they translate localized binding into a change in a system-scale property. However, fabrication and custom functionalization of these sensors is not trivial, and their integration with protocols that pre-enrich target species and facilitate their transport to the biorecognition site is an active area of research. In this presentation, we demonstrate that ion concentration polarization (ICP) in the presence of fluid flow drives focusing and efficient capture of target nucleic acids within a bed of oligoprobe-conjugated beads. A key finding is that ion conduction along the surface of the bioconjugated beads is the dominant contributor to current to the electrode that drives ICP, under the condition of ICP-induced depletion of ions from the bulk solution. Therefore, hybridization of a target nucleic acid (a polyanion) to the bead surface leads to a shift in the slope of the current-voltage curve. Therefore, this approach is versatile in that a target nucleic acid can be detected electrically, in the absence of a label, or electrochemically via a label that generates an electroactive product. We further achieve high-efficiency focusing in a millimeter-scale fluidic channel, which allows for facile fabrication and increased volumetric throughput. This outcome is accomplished by driving ICP with a 3D porous electrode comprised of metallic beads. The metallic and bioconjugated bead beds mitigate fluidic instability that arises at increased length scales and hinders enrichment of target nucleic acids. The resulting approach allows for a plug-and-play nucleic acid sensor using off-the-shelf bioconjugated beads and simple electronics, making it advantageous for point-of-care testing.
Keywords: Please select up to 4 keywords ONLY:
Biotechnology,Nucleic Acids,Voltammetry,Sample Preparation