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Abstract Rapid, inexpensive, and easy-to-use coronavirus disease 2019 (COVID-19) home tests are key tools in addition to vaccines in the world wide fight to eliminate national and local shutdowns. However, currently available tests for SARS-CoV-2, the virus that causes COVID-19, are too expensive, painful, and irritating, or not sufficiently sensitive for routine, accurate home testing. Herein, we employ custom-formulated graphene inks and aerosol jet printing to create a rapid electrochemical immunosensor for direct detection of SARS-CoV-2 spike receptor-binding domain (RBD) in saliva samples acquired noninvasively. This sensor demonstrated limits of detection that are considerably lower than most commercial SARS-CoV-2 antigen tests (22.91 ± 4.72 pg ml −1 for spike RBD and 110.38 ± 9.00 pg ml −1 for spike S1) as well as fast response time (∼30 min), which was facilitated by the functionalization of printed graphene electrodes in a single-step with SARS-CoV-2 polyclonal antibody through the carbodiimide reaction without the need for nanoparticle functionalization or secondary antibody or metallic nanoparticle labels. This immunosensor presents a wide linear sensing range from 1 to 1000 ng ml −1 and does not react with other coexisting influenza viruses such as H1N1 hemagglutinin. By combining high-yield graphene ink synthesis, automated printing, high antigen selectivity, and rapid testing capability, this work offers a promising alternative to current SARS-CoV-2 antigen tests.
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This content will become publicly available on January 28, 2026
Evaporation‐Enhanced Redox Cycling for Rapid Detection of Attomolar SARS‐CoV‐2 Virions Using Nanolithography‐Free Electrochemical Devices
Abstract In fighting against infectious diseases such as COVID‐19, simple‐to‐use, sensitive, scalable, and rapid diagnostics are crucial for early disease diagnosis. In this regard, electrochemical biosensors are particularly attractive in developing point‐of‐need diagnostics. Importantly, by being compatible with nano‐ and microfabrication methods, they are amenable to miniaturization, which reduces background noise and the required sample volume. However, miniaturization also reduces the signal level, making it challenging to detect low virus counts. In this work, microfabricated electrochemical sensors with a dual signal amplification scheme based on evaporation‐enhanced redox cycling (E2RC) in a generator–collector configuration are developed. A scalable, nanolithography‐free fabrication method is proposed to achieve a controllable sub‐micrometer gap between three dimensional (3D) interdigitated microelectrodes by combining photolithography with template‐driven electrodeposition. Using the optimized electrodes, the sensors achieve rapid detection with a limit of quantification of ≈1.2 × 103particles mL−1through continuous measurement in evaporating droplets containing SARS‐CoV‐2 virion mimics. Investigating particle charge and size reveals the role of electrophoretic enrichment in the overall response. The sensor performance is also validated using heat‐inactivated SARS‐CoV‐2 virions, with selective response to SARS‐CoV‐2 against HCoV‐299E, SARS‐CoV S1, and MERS‐CoV S1 (captured using antibody‐functionalized magnetic nanoparticles). The proposed sensing method is sensitive, rapid, scalable, and can be extended to broader applications, including detection of bacteria, extracellular vesicles, and other viruses.
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- Award ID(s):
- 2236997
- PAR ID:
- 10572265
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Advanced Materials Technologies
- ISSN:
- 2365-709X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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