Low-Cost Optodiagnostic for Minute-Time Scale Detection of SARS-CoV-2.

The COVID-19 pandemic has exacerbated our society's tremendous health equity gap. Disadvantaged populations have been disproportionally affected by COVID-19, lacking access to affordable testing, a known effective tool for preventing viral spread, hospitalizations, and deaths. Here, we describe COVID-19 Low-cost Optodiagnostic for Rapid testing (COLOR), a colorimetric biosensor fabricated on cotton swabs using gold nanoparticles modified with human angiotensin-converting enzyme 2 (ACE2), which costs 15¢ to produce and detects SARS-CoV-2 within 5 min. COLOR detected very low viral particle loads (limit of detection: 0.154 pg mL-1 of SARS-CoV-2 spike protein), and its color intensity correlated with the cycle threshold (Ct) values obtained using reverse transcription polymerase chain reaction (RT-PCR). The performance of COLOR was assessed using 100 nasopharyngeal/oropharyngeal (NP/OP) clinical samples, yielding sensitivity, specificity, and accuracy values of 96%, 84%, and 90%, respectively. In summary, each COLOR test can be manufactured for 15¢ and presents rapid minute-time scale detection of SARS-CoV-2, thus providing a solution to enable high-frequency testing, particularly in low-resource communities.