ABSTRACT
Inexpensive yet sensitive and specific biomarker detection is a critical bottleneck in diagnostics, monitoring, and surveillance of infectious diseases such as COVID-19. Multiplexed detection of several biomarkers can achieve wider diagnostic applicability, accuracy, and ease-of-use, while reducing cost. Current biomarker detection methods often use enzyme-linked immunosorbent assays (ELISA) with optical detection which offers high sensitivity and specificity. However, this is complex, expensive, and limited to detecting only a single analyte at a time. Here, it is found that biomarker-bound enzyme-labeled probes act synergistically with nanostructured catalytic surfaces and can be used to selectively reduce a soluble silver substrate to generate highly dense and conductive, localized surface silver metallization on microelectrode arrays. This enables a sensitive and quantitative, simple, direct electronic readout of biomarker binding without the use of any intermediate optics. Furthermore, the localized and dry-phase stable nature of the metallization enables multiplexed electronic measurement of several biomarkers from a single drop (<10 µL) of sample on a microchip.This method is applied for the multiplexed point-of-care (POC) quantitative detection of multiple COVID-19 antigen-specific antibodies. Combining a simple microchip and an inexpensive, cellphone-interfaced, portable reader, the detection and discrimination of biomarkers of prior infection versus vaccination is demonstrated.
ABSTRACT
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.
ABSTRACT
We present a multiplexed, electronic enzyme-linked immunosorbent assay (E2LISA) microchip for direct electrical detection and quantitation of multiple biomarkers from a single microliter-scale drop of sample. Spatially distinct spots on the microchip, each containing an interdigitated microelectrode array, are coated with specific capture agents and used to bind different analytes. Enzyme-labeled probes are then used to convert this analyte binding to an electrical impedance signal via the amplified, localized deposition of silver on the nanostructured, catalytic surface of the chip prepared using gold nanoparticles. We use this microchip with a custom handheld, cellphone interfaced reader to detect COVID-19 biomarkers including antigen-specific antibodies and viral antigens. Further, we demonstrate the multiplexed measurement of distinct antibody responses in serum samples from convalescent COVID-19 patients versus uninfected vaccine recipients. © 2021 MicroTAS 2021 - 25th International Conference on Miniaturized Systems for Chemistry and Life Sciences. All rights reserved.