ELECTRONIC IMMUNOASSAY USING ENZYMATIC METALLIZATION ON MICROPARTICLES

We present here a bead-based immunoassay which provides a sensitive direct electronic readout without the use of any intermediate optics. Analyte binding to antigen-coated microparticles is converted to probe-directed enzymatically amplified silver metallization on microparticle surfaces. The microparticles are then characterized in a high-throughput manner via electrical impedance spectra captured as they flow through a 3-D printed plastic micro-aperture. Metallized microparticles are found to have unique impedance signatures. This enables an electronic readout of the silver metallization density on microparticle surfaces and hence analyte concentration as well. Here we use this scheme to measure the antibody response to the viral nucleocapsid protein in convalescent COVID-19 patient serum. © 2021 MicroTAS 2021 - 25th International Conference on Miniaturized Systems for Chemistry and Life Sciences. All rights reserved.

Characterization of Immune Responses to SARS-CoV-2 and Other Human Pathogenic Coronaviruses Using a Multiplex Bead-Based Immunoassay.

Serological assays that simultaneously detect antibodies to multiple targets of SARS-CoV-2 and to other structurally related coronaviruses provide a holistic picture of antibody response patterns. Well-validated multiplex immunoassays are scarce. Here, we evaluated the performance of an 11-plex serological assay capable of detecting antibodies directed to four antigenic targets of SARS-CoV-2 and to S1 proteins of other human pathogenic coronaviruses. We used 620 well-characterized sera (n = 458 seropositive and n = 110 seronegative for SARS-CoV-2 in the pre-SARS-CoV-2 era and n = 52 seronegative for SARS-CoV-2 in the era of SARS-CoV-2) as positive and negative standards. We calculated the sensitivity, specificity, as well as positive and negative predictive values, including a 95% confidence interval. The difference in mean fluorescence intensity (95% CI) was used to assess a potential cross-reaction between antibodies to SARS-CoV-2 and the other coronaviruses. The sensitivity (95% CI) of detecting anti-SARS-CoV-2 antibodies to four antigenic targets ranged from 83.4% (76.7-86.7) to 93.7% (91.0-95.7) and the specificity from 98.2% (93.6-99.8) to 100% (96.7-100). We observed no obvious cross-reaction between anti-SARS-CoV-2 antibodies and antibodies to the other coronaviruses except for SARS-CoV-1. The high sensitivity and specificity warrant a reliable utilization of the assay in population-based seroprevalence surveys or vaccine efficacy studies.