A Scalable, Easy-to-Deploy, Protocol for Cas13-Based Detection of SARS-CoV-2 Genetic Material

Jennifer N Rauch; Eric Valois; Sabrina C Solley; Friederike Braig; Ryan S Lach; Naomi J Baxter; Kenneth S Kosik; Carolina Arias; Diego Acosta-Alvear; Maxwell Z Wilson

Next, we quantitively compared CREST's sensitivity and cost to established methods. First, we compared it to RT-qPCR (one-step TaqMan assay) and found that, while being similarly sensitive, CREST's reagents cost less than RT-qPCR's even at the low-scale of our pilot experiment (Fig. 3 , Sup. Spreadsheet). In addition, the upfront cost of CREST instrumentation is 30 to 50 times lower. Second, we compared the RT-DNA amplification step of CREST to a variety of Cas13-based protocols that utilize RT-Recombinase Polymerase The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10.1101/2020.04.20.052159 doi: bioRxiv preprint Amplification (RT-RPA). We found thermal cycling amplification (20 cycles) to be substantially more efficient with comparable amplification reaction times (Fig. 3A, Fig. S3 ). Moreover, in stark contrast to the proprietary, high-cost, relatively small batch production rates of reagents required for RPA, Taq polymerase, which has been in highvolume production for decades, and has been a workhorse of modern molecular biology, is readily accessible, stable at room temperature, and lowers costs significantly (Fig. 3B) . Lastly, we compared lateral flow test strip visualization to CREST, and while we found them to equally as sensitive as fluorescent detection methods (Fig. 3A) , their high cost and difficulty to obtain can limit their distribution and scaled use in this pandemic.