Rapid and sensitive detection of viruses can reduce the number of suspicious cases, screen more patients in a shorter period, and help contain the spread of the disease.
Tsinghua-Berkeley Shenzhen Institute (TBSI) Assistant Prof. Qin Peiwu and his team has been developing new ways of detecting the COVID-19 virus with CRISPR reaction, custom designed mini-spectrometer, and single molecule imaging. This novel technique is to address the limitations of current nucleic acid detection kits, which is time-consuming and incapable of detecting shorter COVID-19 RNA fragments.
By integrating single molecule imaging with CRISPR enzymatic reaction, the developed detection system is highly sensitive, specific, and high-throughput. Fluorescent substrates are immobilized on a glass slide as a detection kit, and fluorescence signals are generated when the virus and CRISPR components are introduced. These signals are then collected with a single molecule microscope. In order to enhance signal to noise ratio, the crRNA array is designed to cover all the conserved regions of the coronavirus to maximize the detection efficiency of the virus.
The team will also develop detection strips for rapid virus RNA testing. The CRISPR reaction system is dissolved onto the test paper, which can detect RNA fragments derived from COVID-19 patients' throat swab samples. The signal can be visualized by the eye or by high-sensitivity spectrometer. If the result is negative, single molecule detection can be used to double check since it has higher sensitivity.
Prof. Jennifer Doudna at UC Berkeley and Prof. Zhang Feng at MIT discovered the CRISPR reaction based nucleic acid detection. Dr. Qin has been integrating CRISPR reactions with microfluidic chip for RNA virus detection since 2017. Previously, Dr. Qin detected low-concentration Ebola virus at 20 pfu/ml awith microfluidics, mini-spectrometer, and Cas13a enzyme reaction. The concentration of virus RNA shows linear correlation with fluorescent signal. The assay requires 20 μl sample with 18 reaction chambers for high-throughput detection. They have published the data on ACS Sensors as a cover story.
Dr. Qin has also collaborated with Prof. Du Ke from Rochester Institute of Technology to design a DNA virus detection method based on Cas12a reaction. Dr. Xu Qian from Qin’s lab could detect picomole-concentration of African swine fever virus DNA without DNA amplification. They have just published the data on Biosensors and Bioelectronics and Dr. Xu Qian from TBSI is the first author of the paper.
Edited by Qin Peiwu, Karen Lee
