Accelerated RNA detection using tandem CRISPR nucleases

CDetection.v2: One-pot assay for the detection of SARS-CoV-2

Introduction

The ongoing 2019 coronavirus disease pandemic (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and its variants, is a global public health threat. Early diagnosis and identification of SARS-CoV-2 and its variants plays a critical role in COVID-19 prevention and control. Currently, the most widely used technique to detect SARS-CoV-2 is quantitative reverse transcription real-time quantitative PCR (RT-qPCR), which takes nearly 1 hour and should be performed by experienced personnel to ensure the accuracy of results. Therefore, the development of a nucleic acid detection kit with higher sensitivity, faster detection and greater accuracy is important.

Methods

Here, we optimized the system components and reaction conditions of our previous detection approach by using RT-RAA and Cas12b.

Results

We developed a Cas12b-assisted one-pot detection platform (CDetection.v2) that allows rapid detection of SARS-CoV-2 in 30 minutes. This platform was able to detect up to 5,000 copies/ml of SARS-CoV-2 without cross-reactivity with other viruses. Moreover, the sensitivity of this CRISPR system was comparable to that of RT-qPCR when tested on 120 clinical samples.

Discussion

The CDetection.v2 provides a novel one-pot detection approach based on the integration of RT-RAA and CRISPR/Cas12b for detecting SARS-CoV-2 and screening of large-scale clinical samples, offering a more efficient strategy for detecting various types of viruses.

Powerful CRISPR-Based Biosensing Techniques and Their Integration With Microfluidic Platforms

In the fight against the worldwide pandemic coronavirus disease 2019 (COVID-19), simple, rapid, and sensitive tools for nucleic acid detection are in urgent need. PCR has been a classic method for nucleic acid detection with high sensitivity and specificity. However, this method still has essential limitations due to the dependence on thermal cycling, which requires costly equipment, professional technicians, and long turnover times. Currently, clustered regularly interspaced short palindromic repeats (CRISPR)-based biosensors have been developed as powerful tools for nucleic acid detection. Moreover, the CRISPR method can be performed at physiological temperature, meaning that it is easy to assemble into point-of-care devices. Microfluidic chips hold promises to integrate sample processing and analysis on a chip, reducing the consumption of sample and reagent and increasing the detection throughput. This review provides an overview of recent advances in the development of CRISPR-based biosensing techniques and their perfect combination with microfluidic platforms. New opportunities and challenges for the improvement of specificity and efficiency signal amplification are outlined. Furthermore, their various applications in healthcare, animal husbandry, agriculture, and forestry are discussed.

Equipment-free detection of SARS-CoV-2 and Variants of Concern using Cas13

The COVID-19 pandemic, and the recent rise and widespread transmission of SARS-CoV-2 Variants of Concern (VOCs), have demonstrated the need for ubiquitous nucleic acid testing outside of centralized clinical laboratories. Here, we develop SHINEv2, a Cas13-based nucleic acid diagnostic that combines quick and ambient temperature sample processing and lyophilized reagents to greatly simplify the test procedure and assay distribution. We benchmarked a SHINEv2 assay for SARS-CoV-2 detection against state-of-the-art antigen-capture tests using 96 patient samples, demonstrating 50-fold greater sensitivity and 100% specificity. We designed SHINEv2 assays for discriminating the Alpha, Beta, Gamma and Delta VOCs, which can be read out visually using lateral flow technology. We further demonstrate that our assays can be performed without any equipment in less than 90 minutes. SHINEv2 represents an important advance towards rapid nucleic acid tests that can be performed in any location.

A Novel Miniature CRISPR-Cas13 System for SARS-CoV-2 Diagnostics

Rapid, point-of-care (POC) diagnostics are essential to mitigate the impacts of current (and future) epidemics; however, current methods for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) require complicated laboratory tests that are generally conducted off-site and require substantial time. CRISPR-Cas systems have been harnessed to develop sensitive and specific platforms for nucleic acid detection. These detection platforms take advantage of CRISPR enzymes' RNA-guided specificity for RNA and DNA targets and collateral trans activities on single-stranded RNA and DNA reporters. Microbial genomes possess an extensive range of CRISPR enzymes with different specificities and levels of collateral activity; identifying new enzymes may improve CRISPR-based diagnostics. Here, we identified a new Cas13 variant, which we named as miniature Cas13 (mCas13), and characterized its catalytic activity. We then employed this system to design, build, and test a SARS-CoV-2 detection module coupling reverse transcription loop-mediated isothermal amplification (RT-LAMP) with the mCas13 system to detect SARS-CoV-2 in synthetic and clinical samples. Our system exhibits sensitivity and specificity comparable to other CRISPR systems. This work expands the repertoire and application of Cas13 enzymes in diagnostics and for potential in vivo applications, including RNA knockdown and editing. Importantly, our system can be potentially adapted and used in large-scale testing for diverse pathogens, including RNA and DNA viruses, and bacteria.