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Title: Amplified parallel antigen rapid test for point-of-care salivary detection of SARS-CoV-2 with improved sensitivity
Authors: Tng, Danny Jian Hang
Yin, Bryan Chu Yang
Cao, Jing
Ko, Kwan Ki Karrie 
Goh, Kenneth Choon Meng
Chua, Delia Xue Wen
Zhang, Yong 
Chua, Melvin Lee Kiang
Low, Jenny Guek Hong
Ooi, Eng Eong 
Soo, Khee Chee 
Keywords: COVID-19
Point-of-care detection
Antigen rapid test
Parallel flow amplification
Gold nanoparticles
Issue Date: 1-Jan-2022
Citation: Tng, Danny Jian Hang, Yin, Bryan Chu Yang, Cao, Jing, Ko, Kwan Ki Karrie, Goh, Kenneth Choon Meng, Chua, Delia Xue Wen, Zhang, Yong, Chua, Melvin Lee Kiang, Low, Jenny Guek Hong, Ooi, Eng Eong, Soo, Khee Chee (2022-01-01). Amplified parallel antigen rapid test for point-of-care salivary detection of SARS-CoV-2 with improved sensitivity. MICROCHIMICA ACTA 189 (1). ScholarBank@NUS Repository.
Abstract: In the ongoing COVID-19 pandemic, simple, rapid, point-of-care tests not requiring trained personnel for primary care testing are essential. Saliva-based antigen rapid tests (ARTs) can fulfil this need, but these tests require overnight-fasted samples; without which independent studies have demonstrated sensitivities of only 11.7 to 23.1%. Herein, we report an Amplified Parallel ART (AP-ART) with sensitivity above 90%, even with non-fasted samples. The virus was captured multimodally, using both anti-spike protein antibodies and Angiotensin Converting Enzyme 2 (ACE2) protein. It also featured two parallel flow channels. The first contained spike protein binding gold nanoparticles which produced a visible red line upon encountering the virus. The second contained signal amplifying nanoparticles that complex with the former and amplify the signal without any linker. Compared to existing dual gold amplification techniques, a limit of detection of one order of magnitude lower was achieved (0.0064 ng·mL–1). AP-ART performance in detecting SARS-CoV-2 in saliva of COVID-19 patients was investigated using a case–control study (139 participants enrolled and 162 saliva samples tested). Unlike commercially available ARTs, the sensitivity of AP-ART was maintained even when non-fasting saliva was used. Compared to the gold standard reverse transcription-polymerase chain reaction testing on nasopharyngeal samples, non-fasting saliva tested on AP-ART showed a sensitivity of 97.0% (95% CI: 84.7–99.8); without amplification, the sensitivity was 72.7% (95% CI: 83.7–94.8). Thus, AP-ART has the potential to be developed for point-of-care testing, which may be particularly important in resource-limited settings, and for early diagnosis to initiate newly approved therapies to reduce COVID-19 severity. Graphical abstract: [Figure not available: see fulltext.]
ISSN: 0026-3672
DOI: 10.1007/s00604-021-05113-4
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