Research articles
ScienceAsia 50 (2024):ID 2024077 1-10 |doi:
10.2306/scienceasia1513-1874.2024.077
Effect of azo dye treatment on the detection of human (OC43)
coronavirus surrogate and SARS-CoV-2 viability based on an in-house photoactivator device
Nattamon Niyomdechaa,*, Pirom Noisumdaengb,c, Chompunuch Boonarkartd, Prasert Auewarakuld
ABSTRACT: Innovative detection methods for discriminating between infectious and non-infectious viruses have been
developed to determine the risk of transmission, quarantine policy, and medical treatment. This study evaluated
the efficacy of viability quantitative reverse transcription-polymerase chain reaction (vRT-qPCR) to indicate human
coronavirus surrogate strain OC43 (HCoV-OC43) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
viability based on azo dye treatment combined with our in-house photoactivator device. The factors affecting azo dye
efficacy were optimized in tests with free viral RNA and virus suspension. A propidium monoazide (PMAxx) had a better
performance than ethidium monoazide bromide (EMA) in the exclusion of false positive PCR signals, and its activity
correlated with an increasing dye concentration. Although 50 ?M PMAxx could completely quench amplification of
free viral RNA at a concentration of 108
copies/?l, the highest dose of 2 mM PMAxx was only sufficient for a complete
suppression of inactivated virus suspension at 102 pfu/100 ?l. Additionally, various techniques of dye combinations,
surfactant cotreatment, and double light exposure were tested to improve the result. Only the combination of 1 mM
PMAxx and 10 ?M EMA showed a comparable result to 2 mM PMAxx. The other evaluated conditions had a deleterious
effect on the active virus. Despite an incomplete amplification inhibition, an observed quantification cycle (Cq) value
difference larger than 8 between untreated virus and inactivated virus with intact RNA and compromised capsid might
suggest viral infectivity. Therefore, this research provides vRT-qPCR data in discerning the infectious status of enveloped
SARS-CoV-2 and its surrogate virus.
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| a |
Department of Medical Technology, Faculty of Allied Health Sciences, Thammasat University, Rangsit Campus,
Pathum Thani 12120 Thailand |
| b |
Faculty of Public Health, Thammasat University, Rangsit Campus, Pathum Thani 12120 Thailand |
| c |
Thammasat University Research Unit in Modern Microbiology and Public Health Genomics, Thammasat University,
Pathum Thani 12120 Thailand |
| d |
Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700 Thailand |
* Corresponding author, E-mail: nattamon@tu.ac.th
Received 29 Nov 2023, Accepted 21 Jul 2024
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