Fast bioluminescent nucleic acid detection using one-pot isothermal amplification and dCas9-based split luciferase complementation

Abstract

Nucleic acid detection methods based on isothermal amplification techniques show great potential for point-of-care diagnostic applications. However, most current methods rely on fluorescent or lateral flow assay readout, requiring external excitation or post-amplification reaction transfer. Here, we developed a bioluminescent nucleic acid sensor (LUNAS) platform in which target dsDNA is sequence-specifically detected by a pair of dCas9-based probes mediating split NanoLuc luciferase complementation. Whereas LUNAS itself features a detection limit of ~1 pM for dsDNA targets, the LUNAS platform is easily integrated with recombinase polymerase amplification (RPA), providing attomolar sensitivity in a single-pot assay. We designed a one-pot RT-RPA-LUNAS assay for detecting SARS-CoV-2 RNA without the need for RNA isolation and demonstrated the diagnostic performance for COVID-19 patient nasopharyngeal swab samples using a digital camera to record the ratiometric signal. Detection of SARS-CoV-2 from samples with viral RNA loads of ~200 cp/microL was achieved within ~20 minutes, showing that RPA-LUNAS is attractive for point-of-care diagnostic applications.