Ultrasensitive Detection of COVID-19 Virus N Protein Based on p-Toluenesulfonyl Modified Fluorescent Microspheres Immunoassay.

The pandemic of new coronary pneumonia caused by the COVID-19 virus continues to ravage the world. Large-scale population testing is the key to controlling infection and related mortality worldwide. Lateral flow immunochromatographic assay (LFIA) is fast, inexpensive, simple to operate, and easy to carry, very suitable for detection sites. This study developed a COVID-19 N protein detect strip based on p-toluenesulfonyl modified rare earth fluorescent microspheres. The p-toluenesulfonyl-activated nanomaterials provide reactive sulfonyl esters to covalently attach antibodies or other ligands containing primary amino or sulfhydryl groups to the nanomaterial surface. Antibodies are immobilized on these nanomaterials through the Fc region, which ensures optimal orientation of the antibody, thereby increasing the capture rate of the target analyte. The use of buffers with high ionic strength can promote hydrophobic binding; in addition, higher pH could promote the reactivity of the tosyl group. The detection limit of the prepared COVID-19 N protein strips can reach 0.01 ng/mL, so it has great application potential in large-scale population screening.

Comparative research on nucleocapsid and spike glycoprotein as the rapid immunodetection targets of COVID-19 and establishment of immunoassay strips.

The SARS-CoV-2 virus responsible for coronavirus 2019 (COVID-19) poses a significant challenge to healthcare systems worldwide. According to the World Health Organization (WHO), the outbreak of COVID-19 has been a pandemic that infected more than 25.32 million people and caused more than 848.25 thousand deaths worldwide at the time of 1st September 2020. Despite governmental initiatives aimed to contain the spread of the disease, several countries are experiencing unmanageable increases in medical equipment and larger testing capacity. The current diagnosis based on nuclear acid requires specialized instruments, time-consuming, and laborious, the low-cost and convenient technologies were still urgently needed. Both spike and nucleocapsid are key structural proteins of COVID-19 with good immunogenicity, can serve as primary targets for immunoassay. After comparative research, we certified nucleocapsid antigen-monoclonal antibody (mAbs) system was more suitable for the COVID-19 immunodetection. Subsequently, we designed a rapid test strip based on it that can be used in large-scale screening of COVID-19 in population and more suitable for some remote and special needs areas were restricted by a medical condition or for quick and large quantities of screenings.

Comparison and analysis of results of 120 specimens with three SARS-CoV-2 nucleic acid detection reagents

To provide reference for laboratory by comparing and analyzing the test result of three SARS-CoV-2 nucleic acid detection reagents (real-time RT-PCR). Three kinds of nucleic acid detection reagents (real-time RT-PCR) were used to parallel detect 120 Corona Virus Disease 2019(COVID-19) specimens, including swabs, urine, saliva and feces, and the results were analyzed with SPSS20. As results the positive rates for the A,B, C reagents were 42.50%(51/120), 39.17%(47/120), and 41.67% (50/120), respectively, 89 cases were shown in the same results and there was no significant difference among three reagents (chi²=0.298, P > 0.05), there was no significant difference in the positive detection rate of the four types samples, also (P > 0.05). The consistency of test results from high to low is: A reagent and C reagent > B reagent and C reagent> A reagent and B reagent. There are differences in the test results and test consistency between different manufacturers due to different sensitivity and accuracy. The reagent performance should be further optimized to improve detection sensitivity and accuracy should be improved. At the same time, laboratory should take various quality control methods to ensure the accuracy of SARS-CoV-2 nucleic acid detection, in order to provide better scientific basis for disease prevention and control.