Gold conjugated nanobodies in a signal-enhanced lateral flow test strip for rapid detection of SARS-CoV-2 S1 antigen in saliva samples

Despite the transfer of COVID-19 from the pandemic to control, we are still in a state of uncertainty about long-term success. Therefore, there is a great need for rapid and sensitive diagnostics to sustain the control status. After several optimization trials, we developed lateral flow test (LFT) s...

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Published in:Scientific reports Vol. 13; no. 1; pp. 10643 - 12
Main Authors: Maher, Sara, Kamel, Manal, Demerdash, Zeinab, El Baz, Hanan, Sayyouh, Omar, Saad, Amany, Ali, Noha, Salah, Faten, Atta, Shimaa
Format: Journal Article
Language:English
Published: London Nature Publishing Group UK 30.06.2023
Nature Publishing Group
Nature Portfolio
Subjects:
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631/326
ACE2
Angiotensin
Angiotensin-converting enzyme 2
Antigens
COVID-19
Gold
Humanities and Social Sciences
Monoclonal antibodies
multidisciplinary
Nanobodies
Pandemics
Peptidyl-dipeptidase A
Saliva
Science
Science (multidisciplinary)
Severe acute respiratory syndrome coronavirus 2
ISSN:2045-2322, 2045-2322
Online Access:Get full text
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Summary:Despite the transfer of COVID-19 from the pandemic to control, we are still in a state of uncertainty about long-term success. Therefore, there is a great need for rapid and sensitive diagnostics to sustain the control status. After several optimization trials, we developed lateral flow test (LFT) strips for rapid detection of SARS-CoV-2 spike 1 (S1) antigen in saliva samples. For signal enhancement of our developed strips, we applied dual gold conjugates. Gold-labeled anti-S1 nanobodies (Nbs) were employed as S1 detector conjugate, while gold-labeled angiotensin-converting enzyme 2 (ACE2) was used as S1 capturing conjugate. In a parallel strip design, we used an anti-S1 monoclonal antibody (mAb) as an antigen detector instead of anti-S1 Nbs. Saliva samples were collected from 320 symptomatic subjects (180 RT-PCR confirmed positive cases and 140 confirmed negative cases) and were tested with the developed strips. In early detection for positive samples with cycle threshold (Ct ≤ 30), Nbs-based LFT strips showed higher sensitivity (97.14%) and specificity (98.57%) than mAb-based strips which gave 90.04% sensitivity and 97.86% specificity. Moreover, the limit of detection (LoD) for virus particles was lower for Nbs-based LFT (0.4 × 10 4 copies/ml) than for the mAb-based test (1.6 × 10 4 copies/ml). Our results are in favor of the use of dual gold Nbs and ACE2 conjugates in LFT strips. These signal-enhanced strips offer a sensitive diagnostic tool for rapid screening of SARS-CoV-2 S1 antigen in the easily collected saliva samples.
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ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-023-37347-y