The outbreaks of the infectious disease COVID-19 caused by SARS-CoV-2 seriously threatened the life of humans. A rapid, reliable and specific detection method was urgently needed. Herein, we reported a contamination-free visual detection method for SARS-CoV-2 with LAMP and CRISPR/Cas12a technology. CRISPR/Cas12a reagents were pre-added on the inner wall of the tube lid. After LAMP reaction, CRISPR/Cas12a reagents were flowed into the tube and mixed with amplicon solution by hand shaking, which can effectively avoid possible amplicon formed aerosol contamination caused by re-opening the lid after amplification. CRISPR/Cas12a can highly specific recognize target sequence and discriminately cleave single strand DNA probes (5′-6FAM 3′-BHQ1). With smart phone and portable 3D printing instrument, the produced fluorescence can be seen by naked eyes without any dedicated instruments, which is promising in the point-of-care detection. The whole amplification and detection process could be completed within 40 min with high sensitivity of 20 copies RNA of SARS-CoV-2. This reaction had high specificity and could avoid cross-reactivity with other common viruses such as influenza virus. For 7 positive and 3 negative respiratory swab samples provided by Zhejiang Provincial Center for Disease Control and Prevention, our detection results had 100% positive agreement and 100% negative agreement, which demonstrated the accuracy and application prospect of this method.

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BackgroundInfluenza represents a serious public health concern. The emergence of resistance to anti-influenza drugs underlines the need to develop new drugs. This study aimed to evaluate the anti-influenza viral activity and possible mechanisms of 12 phenanthrenes from the medicinal plant Bletilla striata (Orchidaceae family). MethodsTwelve phenanthrenes were isolated and identified from B. striata. Influenza virus A/Sydney/5/97 (H3N2) propagated in embryonated chicken eggs was used. Phenanthrenes mixed with the virus were incubated at 37 °C for 1 h and then inoculated into 9-day-old embryonated chicken eggs via the allantoic route to survey the antiviral activity in vivo. A (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H–tetrazolium) (MTS)-based assay was performed to evaluate the reduction of cytopathic effect induced by H3N2 on Madin-Darby canine kidney (MDCK) cells. The hemagglutination inhibition assay was used to study the blockage of virus receptors by the phenanthrenes, and the neuraminidase (NA) inhibition assay to evaluate the effects of the release of virus. The synthesis of influenza viral matrix protein mRNA in response to compound treatment was measured by real-time polymerase chain reaction.ResultsThis study showed that phenanthrenes 1, 2, 3, 4, 6, 9, 10, 11, and 12 significantly inhibited the viruses in vivo, with inhibition rates of 20.7, 79.3, 17.2, 34.5, 34.5, 34.5, 44.8, 75.9, and 34.5%, respectively. In MDCK models, the phenanthrenes did not show significant antiviral activity when administered as pretreatment, while phenanthrenes 2, 3, 4, 6, 7 10, and 11 exhibited inhibitory activities as simultaneous treatment with 50% inhibition concentration (IC50) ranging from 14.6 ± 2.4 to 43.3 ± 5.3 μM. The IC50 ranged from 18.4 ± 3.1 to 42.3 ± 3.9 μM in the post-treatment assays. Compounds 1, 3, 4, 6, 10, and 11 exhibited an inhibitory effect on NA; and compounds 2, 3, 4 6, 7, 10, and 11 resulted in the reduced transcription of virus matrix protein mRNA. However, no compound could inhibit hemagglutination by the influenza virus.ConclusionPhenanthrenes from B. striata had strong anti-influenza viral activity in both embryonated eggs and MDCK models, and diphenanthrenes seemed to have stronger inhibition activity compared with monophenanthrenes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12906-017-1780-6) contains supplementary material, which is available to authorized users.

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