key: cord-0942196-buiiepcy
authors: Xu, Yang; Rather, Adil M.; Song, Shuang; Fang, Jen-Chun; Dupont, Robert L.; Kara, Ufuoma I.; Chang, Yun; Paulson, Joel A.; Qin, Rongjun; Bao, Xiaoping; Wang, Xiaoguang
title: Ultrasensitive and Selective Detection of SARS-CoV-2 using Thermotropic Liquid Crystals and Image-based Machine Learning
date: 2020-11-17
journal: Cell Rep Phys Sci
DOI: 10.1016/j.xcrp.2020.100276
sha: d98a1dc3ac6199dbf60791260dbefa90187e3bc6
doc_id: 942196
cord_uid: buiiepcy

Rapid, robust virus detection techniques with ultrahigh sensitivity and selectivity are required for the outbreak of the pandemic coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). Here, we report that the femtomolar concentrations of single-stranded ribonucleic acid (ssRNA) of SARS-CoV-2 trigger ordering transitions in liquid crystal (LC) films decorated with cationic surfactant and complementary 15-mer single-stranded deoxyribonucleic acid (ssDNA) probe. More importantly, the sensitivity of the LC to the severe acute respiratory syndrome (SARS) ssRNA, with a 3 base pair-mismatch compared to the SARS-CoV-2 ssRNA, is measured to decrease by seven orders of magnitude, suggesting that the LC ordering transitions depend strongly on the targeted oligonucleotide sequence. Finally, we design a LC-based diagnostic kit and a smartphone-based application (App) to enable automatic detection of SARS-CoV-2 ssRNA, which could be used for reliable self-test of SARS-CoV-2 at home without the need for complex equipment or procedures.

The outbreak of the coronavirus disease 2019 , caused by the novel severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) virus, has spread rapidly and evolved into a global pandemic. 1-3 SARS-CoV-2 has an incubation period of 2-7 days during which infected individuals present no obvious symptoms, 4, 5 and the transmission of the SARS-CoV-2 virus has been shown to peak on or before symptom onset. 6, 7 To efficiently control such pre-symptomatic transmission, rapid, robust, and inexpensive tests should be performed on a large fraction of the population. 3, 8 Nucleic acid tests on the viral RNAs swabbed from a patient's throat or nasal passage, typically in the form of a reverse-transcription polymerase chain reaction (RT-PCR) test, are effective for the detection of the SARS-CoV-2 virus. This RT-PCR test is considered to be the "gold standard" for clinical diagnosis. [8] [9] [10] A promising alternative approach to RT-PCR is the isothermal amplification method, which mainly contains two techniques: loop-mediated isothermal amplification (LAMP) 11 and recombinase polymerase amplification (RPA). 12 However, these methods require both long characterization time and specialized equipment.

Very recently, Cas12 and Cas13, 13 gold nanoparticles, 14 field-effect transistors (FETs), 15 the plasmonic photothermal (PPT) effect, 16 and column agglutination test (CAT) technologies 17 have emerged as diagnostic tools for the detection of SARS-CoV-2. While these diagnostic techniques are promising, each has its own limitations. For example, the gold nanoparticle-based technique is cost-prohibitive for large-scale testing and requires improvements in its detection limit in order to reduce the required input amount of virus samples. Moreover, the FETs and PPT effect-based diagnostic approaches require specialized J o u r n a l P r e -p r o o f analytical equipment for virus detection, while the CAT approach requires blood sample collection and centrifugation that depends on an established testing laboratory. Thus, the development of a low-cost, rapid, reliable and simple diagnostic method for the self-detection of the SARS-CoV-2 virus remains elusive.

Thermotropic liquid crystals (LCs) exhibit unifying characteristics and behaviors that emerge from the long-range orientational order and mobility of their mesogenic constituents, 18, 19 and have been broadly utilized in fast switching electro-optical devices, such as liquid crystal displays (LCDs). 20 Over the past decade, a series of work has revealed the design of LC films and droplets that undergo orientational ordering transitions in response to a wide range of molecules adsorbed at an interface, including synthetic surfactants [21] [22] [23] and polymers, 24, 25 phospholipids, [26] [27] [28] [29] peptides, 30 proteins, [31] [32] [33] [34] streptavidin, 35 bacterial toxins, 36 and deoxyribonucleic acid (DNA). [37] [38] [39] [40] [41] For instance, single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) produce different orientations of LCs at cationic surfactant-laden aqueous-LC interfaces, which leads to a change in the effect on visible light caused by the optical birefringence of the LC film and thus enables the detection of DNA hybridization under polarized light microscopy. 40, 41 Despite the great potential of LC biosensor applications, their rational study and use in the detection of ribonucleic acid (RNA), which is the core genetic materials of most pathogenic viruses, have not yet been explored.

In this study, we report the design of LC-based sensors for the reliable detection of SARS-CoV-2 RNA. Specifically, a partially self-assembled monolayer of cationic surfactants is formed at an aqueous-LC interface, followed by the adsorption of a 15-mer ssDNA probe with a complementary sequence to the SARS-CoV-2 virus at the cationic surfactant-laden J o u r n a l P r e -p r o o f aqueous-LC interface. We demonstrate that the ordering transition in the formed LC surface strongly depends on the targeted nucleotide sequence. The minimum concentration of SARS-CoV-2 RNA that can drive an ordering transition in the LC film is seven orders of magnitude lower than that of the base pair-mismatched severe acute respiratory syndrome (SARS) RNA. Furthermore, we design and fabricate a LC-based SARS-CoV-2 RNA point-of-care detection kit, with an obtained response that is visible to the naked-eye without any additional equipment, and a smartphone-based application (App) to enhance the overall accuracy of the test result readout and to avoid user error. Overall, these results unmask principles by which LCs and RNA can be coupled at cationic surfactant-decorated aqueous interfaces, and hint at new routes by which the RNA of a pathogenic virus can be rapidly and easily sensed using LCs with both high sensitivity and selectivity.

The initial experiments reported below employed a cationic surfactant dodecyltrimethylammonium bromide (DTAB)-decorated interface on micrometer-thick films of nematic E7. The thermotropic LC E7 was chosen because of the relatively broad temperature range of its nematic mesophase (-62 to 58 o C). In this phase, the rod-shaped E7 molecules have no positional order but self-align to possess a long-range orientational order.

As described in the Experimental Procedures and in Figure 1 , films of nematic E7, with an approximately flat interface, were prepared by filling the pores of a 20 µm-thick copper specimen grid supported on a dimethyloctadecyl [3-(trimethixysilyl) propyl]ammonium J o u r n a l P r e -p r o o f chloride (DMOAP)-functionalized glass slide, which induced a perpendicular ordering of the E7. Next, the E7 films were submerged into an aqueous solution of 5 mM sodium chloride (NaCl; pH ~ 5.5-6.0), which was chosen to minimize the repulsive interaction of the base pairs of the ssDNA. 40 A monolayer of DTAB was subsequently deposited at the aqueous-E7 interface by adding an aqueous solution of DTAB to the aqueous phase above the E7 film. The DTAB was then allowed to adsorb onto the surface for 10 minutes. The optical images of DTAB-decorated E7 films were obtained by using an Olympus BX53 polarized light microscope equipped with crossed polarizers and set to the transmission mode. After adsorption of DTAB at the aqueous-E7 interface, we observed the optical appearance of the E7 films to be uniformly dark, which is consistent with the homeotropic anchoring of the nematic E7 at the DTAB-decorated aqueous interface of the E7 films ( Figure 2A ). Previous studies have established that steric interactions between the acyl tails of synthetic surfactants and mesogens cause LCs to adopt a homeotropic orientation. 37, 40 We comment here that under the experimental condition of a 0.5 mM solution of DTAB, where the surface coverage of DTAB was near the minimum required for homeotropic orientation, we calculated only ~ 36% of the aqueous interface to be covered by DTAB (see Notes S1 and S2). These results suggest that a substantial open LC surface area exists at the interface and thus a LC reorientation is allowed upon the adsorption of ssRNA and/or ssDNA at the interface. We also comment here that such low surface coverage of DTAB plays a critical role in the ultrasensitive detection of SARS-CoV-2, which will be discussed later.

J o u r n a l P r e -p r o o f Next, we deposited a 15-mer probe ssDNA (ssDNA probe ; 5'-GCATCTCCTGATGAG-3'), which can hybridize with our target 15-mer SARS-CoV-2 ssRNA (ssRNA CoV ; 5'-CUCAUCAGGAGAUGC-3'), at the DTAB-decorated aqueous-E7 interface. The negatively-charged ssDNA is attracted to the cationic DTAB at the aqueous-E7 interface via electrostatic interactions. The temperature of the system was kept at the melting temperature (T m ) of the ssDNA probe , at which 50% of the nucleotide was annealed. Figure 2B shows the dynamic optical response of the DTAB-decorated nematic E7 film to the adsorption of ssDNA probe . After addition of 100 nM ssDNA probe , micrometer-sized domains with a bright optical appearance (corresponding to the regions of E7 with a tilted or planar alignment) nucleated at the interface. Subsequently, these domains grew over a period of 10 minutes resulting in a bright optical appearance across the entire aqueous-E7 interface. These results indicate that, as the ssDNA probe adsorbs to the interface, the flexible ssDNA probe chains (with typical persistence length of ~ 6 Å) 42 tend to spread at the surface and the hydrophobic bases of the ssDNA probe interact with the DTAB to decrease the effective surface coverage of DTAB below what is required for a homeotropic orientation, resulting in a reorientation of the LC from homeotropic to either tilted or planar, as illustrated in Figure 2C . This phenomenon is consistent with previous studies. 37, 41 The concentration of the ssDNA probe was fixed at 100 nM for the rest of the experiments performed in this work. We emphasize here that the addition of 100 nM ssDNA probe to E7 films incubated in a 6 mM DTAB solution (> 90% of the aqueous-E7 interface is covered by DTAB ( Figure S1 )) triggers no measurable change in the optical appearance of the E7 films, revealing that the surface coverage of DTAB plays a J o u r n a l P r e -p r o o f key role in driving the reorientation of the LC surface anchoring upon adsorption of the ssDNA probe .

In this set of experiments, we investigated the effect of the adsorption of ssRNA CoV on the optical response of the ssDNA probe /DTAB-decorated aqueous-E7 interfaces (Video S1). As shown in Figure 3A , after addition of the ssRNA CoV to the aqueous phase, black domains were observed to nucleate and grow on the E7 surface over a period of 20 minutes, resulting in a uniformly dark optical appearance which corresponds to the homeotropic anchoring of the nematic E7 across the entire aqueous-E7 interface. Furthermore, quantification of the optical appearance of the E7 films revealed a clear threshold concentration in a plot of normalized grayscale of E7 films versus ssRNA CoV concentration ( Figures 3B and S2) . Figure 3D shows that remarkably low concentrations of ssRNA CoV (~ 30 femtomolar of target ssRNA) are able to trigger the ordering transition of the E7 (see Note S3

and Figure S3 ). In addition, the response time of the E7 film from a bright to dark optical appearance decreased with an increase in the concentration of ssRNA CoV , as shown in Figure   3E .

Our polarized light microscopy imaging revealed that the adsorption of ssRNA CoV caused a LC reorientation from tilted/planar to homeotropic at the DTAB-decorated aqueous-E7 interface. We notice here that our results shown in Figure 3C are strikingly similar to past studies of the DNA hybridization at an aqueous-LC interface, where hybridization between a ssDNA probe and a complementary targeted ssDNA caused a transition from a tilted/planar to a perpendicular orientation of the LCs at the cationic surfactant-decorated aqueous-LC J o u r n a l P r e -p r o o f interface. 37, 40, 41 Building from the previous studies of the DNA hybridization at LC surfaces, we hypothesize that upon adsorption of complementary ssRNA CoV to the aqueous-E7 interface, the nucleobases of ssRNA CoV will bind to its complementary base of the ssDNA probe rather than remaining intercalated between the surfactant molecules due to the strong forces from hydrogen bonding and hydrophobic interactions involved in the process of hybridization.

Once hybridized, the rigidity of the ssDNA-ssRNA complexes increase (e.g., the persistence length of the dsDNA increases by two orders of magnitude). 42, 43 Such an increase in the rigidity compacts the double strands of the ssRNA-ssDNA and the hydrophobic bases are no longer exposed. Therefore, the rigid ssDNA-ssRNA complexes allow for a more efficient packing at the DTAB-decorated aqueous-E7 interface, and thus reorganize the DTAB to the original surface coverage prior to the ssDNA probe adsorption. This increase in effective surface coverage of DTAB gives rise to the transition from the planar/tilted orientation to the homeotropic orientation that is observed in our experiments.

Next, we performed two additional experiments to provide insight into the role of the target ssRNA on the ordering transition in LC films. First, we adsorbed pre-hybridized ssDNA probe -ssRNA CoV to the DTAB-decorated E7 films that were prepared as described earlier (see Note S4). At concentrations up to 100 nM, the presence of pre-hybridized ssDNA probe -ssRNA CoV had no measurable impact on the optical appearance of the E7 film ( Figure S4 ). Second, we adsorbed complementary 15-mer SARS-CoV-2 ssDNA (ssDNA CoV ; 5'-CTCATCAGGAGATGC-3') to the ssDNA probe /DTAB-decorated aqueous-E7 interface.

Similar to the ssRNA CoV , we observed the ssDNA CoV was able to trigger the ordering transition of the DTAB-decorated E7 film at remarkably low concentrations (< 10 2 fM). We J o u r n a l P r e -p r o o f note here that the sensitivity of our DTAB-decorated E7 film (30 fM) is around three orders of magnitude higher than previous study on the detection of a ssDNA using a DTAB-decorated nematic LC film (50 pM). 41 The ultrasensitivity of our LC films can be attributed to the minimum surface coverage of DTAB at the aqueous-E7 interface (0.5 mM) compared with the concentration of DTAB (several mM) in the previous study. 41

To examine the selectivity of the obtained ssDNA probe /DTAB-decorated E7 films, 15-mer ssRNAs or ssDNAs with different degrees of base pair-mismatch were tested. The first oligonucleotide sequence tested was the SARS virus, a close member of the coronavirus family that emerged in 2003, with a nucleotide sequence 5'-AUCAUCCGGUGAUGC-3' (ssRNA SARS ), which contains a 3 base pair-mismatch compared with the ssDNA probe . As shown in Figure 4A , for concentrations up to 30 nM, we measured no change in the optical appearance of the ssDNA probe /DTAB-decorated E7 films for 90 minutes upon adsorption of ssRNA SARS (Video S2). When the concentration of ssRNA SARS reached 100 nM, the E7 film underwent an optical change from bright to dark after 90 minutes, corresponding to an ordering transition of E7 from planar/tilted to perpendicular at the aqueous-E7 interface.

Moreover, we observed similar results using ssDNA SARS ( Figure 4B ). This pronounced difference in threshold concentration of ssRNA CoV (30 fM) and ssRNA SARS (100 nM) required to trigger ordering transitions within E7 films (seven orders of magnitude) leads us to hypothesis that lack of hybridization between the ssDNA probe and ssRNA SARS , due to the 3 base pair-mismatch, caused no increase in the effective surface coverage of DTAB to trigger the E7 ordering transition at the aqueous-E7 interface ( Figure 4C ). We notice here that 10 µ L J o u r n a l P r e -p r o o f of 30 fM ssRNA CoV corresponds to ~ 1.8 × 10 5 copies, which is comparable with the SARS-CoV-2 virus RNA copy number in real patient swab sample. 6 To further test this hypothesis, we performed measurements with two additional 15-mer ssDNA sequences with different degrees of base pair-mismatch: 7 base pair-mismatch ssDNA (ssDNA 7bpm ; 5'-AGCGTCCGGTGACGT-3') and 15 base pair-mismatch ssDNA (ssDNA 15bpm ; 5'-AGACGACTTCTCGTA-3'). When the ssDNA concentration reached 100 nM, the ssDNA 7bpm triggered the optical change of the ssDNA probe /DTAB-decorated E7 films after a period of 90 minutes, which is similar to the behavior of both ssDNA SARS and ssRNA SARS . Additionally, the ssDNA 15bpm failed to cause any measurable difference in the optical appearance of the E7 films over a wide concentration range (3 fM -100 nM) after 90 minutes. Overall, these results support our hypothesis that the response of the ssDNA probe /DTAB-decorated LC film strongly depends on the targeted oligonucleotide sequence, which gives rise to an ultrahigh selectivity to complementary ssRNA CoV .

In the final set of experiments for this study, we sought to design a point-of-care detection kit for SARS-CoV-2 that is visible to the human eye. We fabricated a 2.5 cm × 2.5 cm optical cell-based detection kit by pairing one bare glass slide and one DMOAP-functionalized glass slide each with a polarizer sheet. The two surfaces were then spaced apart with a 2 mm-thick poly(dimethylsiloxane) (PDMS) spacer, as shown in Figure 5A and 5B. An opening was conserved in the center and at one side of the PDMS spacer to allow for the analysis and the injection of the test samples, respectively. A copper specimen grid (TEM grid) was placed on the surface of the DMOAP-functionalized glass slide and was subsequently filled with E7.

The optical cell was then filled with a 5 mM NaCl aqueous solution containing the ssDNA probe at a concentration of 100 nM. We notice here that TEM grid can stabilize LC film against dewetting by water, and our LC sensors exhibit good stability under water for at least 10 days. We also comment here that this LC detection kit is not reusable. The bright optical appearance was visible to the human eye. Subsequently, 2 µL of ssRNA CoV or ssRNA SARS was added to the detection kit. When viewed with natural (sunlight) or artificial (lamp) light, a significant decrease in the brightness of the specimen grid was observed upon the addition of a 30 fM ssRNA CoV solution ( Figure 5C ) and no measurable difference in the optical appearance in the case of a 30 fM ssRNA SARS aqueous solution ( Figure 5D ). In conclusion, it was observed that the LC ordering transitions can be triggered by adsorbing ssRNA CoV at a cationic surfactant/ssDNA probe aqueous-LC interface in a manner that depends strongly on the targeted nucleotide sequence. Additionally, when the surface coverage of DTAB was near the minimum required for a homeotropic orientation of the LCs, the minimum concentration of ssRNA CoV that can drive the ordering transitions in the E7 film are seven orders of magnitude lower than that of ssRNA SARS . In comparison with conventional detection techniques, we find that ssRNA CoV -driven ordering transitions in LC films exhibited ultrahigh sensitivity and selectivity. To the best of our knowledge, this is the first experimental evidence that LC films can optically respond to adsorbed RNA on an interface. Our results suggest new principles for the naked-eye self-detection of viruses,

including SARS-CoV-2, without requiring complex equipment or procedure.

In future work, we will investigate the selective LC detection on different SARS-CoV-2 genome sequences and similar control sequences with fewer base pair mismatches.

Additionally, the massive detection of full-length SARS-CoV-2 RNA containing patient samples will be performed in a biosafety level 3 (BSL-3) laboratory to validate its reliability.

Moreover, the influence of the target ssRNA on the ordering transition of LC confined in droplets is being investigated. Future efforts will also seek to explore more sophisticated deep learning methods for image analysis, such as convolutional neural networks (CNNs), 46 which have been successfully applied in LC chemical sensors, 47,48 semiconductors, 49 and a variety of image-based medical diagnostic tests 50 including X-rays, ultrasounds, and magnetic resonance imaging (MRI). The main advantage of CNNs is their inherent capability to learn more complex features directly from raw data -mitigating the need to use expert knowledge to define specific hand-crafted features as done as a proof-of-concept in this work.

Further information should be directed to and will be fulfilled by the Lead Contact, Xiaoguang Wang (Email: wang.12206@osu.edu).

This study did not generate new unique materials.

Further requests for datasets and code should be directed to and will be fulfilled by the Lead Contact.

Thermotropic LC E7 was purchased from Jiangsu Hecheng Advanced Materials Co., Ltd. 

A copper specimen grid was placed on the surface of a DMOAP-functionalized glass slide (7 mm × 7 mm). Next, 0.5 µL of E7 was placed on the specimen grid using a syringe with the excess E7 being removed with a capillary tube to obtain a uniform thin film. The obtained E7-infused specimen grid was observed under polarized light microscopy to confirm the homeotropic orientation of LC mesogens within the LC film. In this work, E7 was used due to its relatively high nematic-isotropic phase transition temperature.

The E7-filled specimen grid on the DMOAP-functionalized glass slide was immersed into a 5 mM NaCl aqueous solution (pH ranged from 5.5 to 6.0) and was subsequently exposed to a 0.5 mM DTAB solution. The E7 mesogens adopted a perpendicular anchoring at the DTAB-laden aqueous-E7 interfaces.

The optical appearance of the E7 film during adsorption of ssRNA/ssDNA at the aqueous-E7

interface was recorded using an Olympus BX53 polarized light microscope equipped with crossed polarizers. Images were captured using a charge-coupled device (CCD) camera.

The probe ssDNA (ssDNA probe ; 15-mer-5'-GCATCTCCTGATGAG-3') was added to the DTAB-adsorbed E7 surface and the optical response of the E7 surface was characterized with polarized light microscopy. The surface anchoring of E7 changed from homeotropic to planar/tilted within 5 minutes as the concentration of the ssDNA probe reached 100 nM resulting in a bright optical appearance.

Here we used SARS-CoV-2 ssRNA (ssRNA CoV ; 15mer-5'-CUCAUCAGGAGAUGC-3') as an example. We added ssRNA CoV to the DTAB-laden E7 surface with the adsorbed ssDNA probe . The temperature of the system was increased to 48.7 o C, which is the melting temperature (T m ) of the ssRNA CoV . A Linkam PE120 Peltier hot stage was used to control the temperature of the E7 surface during these measurements. We characterized the grayscale of the E7 film over a period of 40 minutes. To determine the detection limit of the E7 surface for the target ssRNA/ssDNA, we varied the concentration of the target ssRNA/ssDNA from nanomolar to femtomolar concentrations.

A KRÜSS DSA 100 goniometer was used to measure the surface tension of aqueous-E7 interfaces using a pendant drop method. During these measurements, E7 was pushed through J o u r n a l P r e -p r o o f a needle slowly, at 5 µL/min, to minimize the effect of the dynamic forces on the shape of the droplet. Images of the pendant E7 droplet near departure were captured and analyzed using a drop shape analyzer to estimate the surface tensions.

The optical appearance (i.e., brightness) of the RNA-adsorbed E7 films was quantified from images using ImageJ software. We set the grayscale of the E7 film upon adsorption of DTAB and the ssDNA probe to be G DTAB and G probe , respectively. Upon addition of the target DNA/RNA, the grayscale of the E7 films, G, was measured and the rescaled grayscale value was calculated as: A copper specimen grid, filled with E7 and placed on a DMOAP-functionalized glass slide, was immersed into a 5 mM NaCl aqueous solution (pH ranged from 5.5 to 6.0). Subsequently, after being exposed to a 0.5 mM DTAB solution, the E7 mesogens adopted a perpendicular anchoring, shown in the beginning of the video. When the probe ssDNA is added to the DTAB-adsorbed E7 surface, the surface anchoring of the E7 changes from homeotropic to planar within 5 minutes as the concentration of the ssDNA probe reached 100 nM. This results in a bright optical appearance. Then, 30 fM of ssRNA CoV is added to the DTAB-laden E7

surface with the adsorbed ssDNA probe ; at the same time, the temperature of the system is increased to 48.7 o C, which is the melting temperature (T m ) of the ssRNA CoV . The polarized light microscopy imaging, with black domains growing on the E7 surface over the period of 20 minutes, revealed that the adsorption of the ssRNA CoV caused a reorientation of the E7 from a tilted/planar to a homeotropic orientation at the DTAB-decorated aqueous-E7

interface.

A copper specimen grid, filled with E7 and placed on a DMOAP-functionalized glass slide, was immersed into a 5 mM NaCl aqueous solution (pH ranged from 5.5 to 6). Subsequently, after being exposed to a 0.5 mM DTAB solution, the E7 mesogens adopted a perpendicular anchoring. When the probe ssDNA was added to the DTAB-adsorbed E7 surface, the surface anchoring of the E7 changed from homeotropic to planar within 5 minutes as the 

The experimental strategy was proposed initially by X.B. and X. 

The Ohio State University has filed a patent application (Application Number 63066000) on the work described in this manuscript. The inventors listed on the patent application are X.W., X.B., Q.R., X.Y. and A.M.R. The authors declare no other competing interests. 

A familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: a study of a family cluster

Clinical features of patients infected with 2019 novel coronavirus in Wuhan

Early transmission dynamics in Wuhan, China, of novel coronavirus-infected pneumonia

A novel coronavirus from patients with pneumonia in China

The epidemiology and pathogenesis of coronavirus disease (COVID-19) outbreak

Virological assessment of hospitalized patients with COVID-2019

Temporal dynamics in viral shedding and transmissibility of COVID-19

The genetic sequence, origin, and diagnosis of SARS-CoV-2

Real-time RT-PCR panel for detection 2019-nCoV. (US Centers for for Disease Control and Prevention

Current and perspective diagnostic techniques for COVID-19

Overcoming the bottleneck to widespread testing: a rapid review of nucleic acid testing approaches for COVID-19 detection

Rapid and visual detection of 2019 novel coronavirus (SARS-CoV-2) by a reverse transcription loop-mediated isothermal amplification assay

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