Preamplification-free ultra-fast and ultra-sensitive point-of-care testing via LwaCas13a.

CRISPR based nucleic acid detection technology provides a deployable approach to point of care testing. While, there remain challenges limiting its practical applications, such as the need for pre-amplification and the long turnaround time. Here, we present a self-cascade signal amplification method with LwaCas13a and an artificially designed "U" rich RNA of stem-loop structure (URH) for pre-amplification-free ultra-fast and ultra-sensitive point-of-care testing (PASSPORT). The PASSPORT system contains: URH, crRNA targeted the URH, crRNA targeted the interesting RNA, fluorescent RNA reporter and LwaCas13a. The assay realized the detection of 100 copies/mL, within 5 min. The PASSPORT platform was further adopted for the detection of marker gene from SASR-CoV-2 and Severe fever with thrombocytopenia syndrome virus (SFTSV), respectively, and 100% accuracy for the analysis of clinical specimens (100 SASR-CoV-2 specimens and 16 SFTSV specimens) was obtained. Integrated with a lateral flow assay device, this assay could provide an alternative platform for the development of point of care testing (POCT) biosensors. PASSPORT has the potential to enable sensitive, specific, user-friendly, rapid, affordable, equipment-free and point-of-care testing for the purpose of large-scale screening and in case of epidemic outbreak.