Test for Maranda

Session Number: L03-08
Track: Electrochemistry
Monday, March 08, 2021: 11:05 AM – 11:25 AM


Author: Sommer Osman
Iowa State University

Co-author: Kira Rahn
Iowa State University

Co-author: Robbyn Anand
Iowa State University


We report a novel lateral flow assay (LFA) that exploits a local electric field gradient to pre-concentrate antigens at the test line. Our method employs this additional amplification step to improve limits of detection in LFAs, which historically suffer from poor sensitivity at ultra-low concentrations relevant for bioanalysis. We utilize dual Nafion-coated electrodes, overlaid on a paper analytical device (PAD), to achieve ion concentration polarization focusing (ICPF). In ICPF, a charged analyte focuses and stacks along an electric field gradient at a location where its electrophoretic velocity balances convective flow. We demonstrate the pre-concentration of small molecules, proteins and antibodies with enrichment factors upwards of 100 fold. The PAD employs a patterned bead bed to counteract vortex flow within the device and to stabilize the focused plug. Performance optimization is achieved by tuning voltage and flow rate. Integration of ICPF with the LFA is then demonstrated by enriching a model antigen, rabbit immunoglobulin G, over a bead bed conjugated to capture antibody. Compared to a control LFA, the ICPF-LFA brought antigen within limits of detection and allowed for visual confirmation that was not seen without the initial enrichment step. This method is then applied to the enrichment and detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid protein in simulated saliva, by colorimetric readout with the ICP-LFA. We anticipate that this method can be adapted to enhance LFAs for several classes of biomarkers by simple modifications to the paper strip, flow rate, and voltage. The device presented here is constructed from low cost materials and fabricated in a facile manner to promote widespread use. We envision our device will lead to early disease detection and better clinical outcomes. The authors gratefully acknowledge the Research Corporation for Science Advancement for grant support through the COVID Initiative.

Course Info Register Now