Colorimetric Boolean AND-gated readout of multiplex LAMP-OSD assays using lateral flow dipsticks. (A) Schematic depicting colorimetric Boolean AND logic-gated readout of multiplex LAMP-OSD assays using strand displacement gating probes (AND Gate OSD) and lateral flow dipsticks designed to detect analytes labeled with both biotin and fluorescein. AuNP, gold nanoparticle. LP-Biotin, biotin-labeled primer; LP-FAM, fluorescein-labeled primer. (B) Cellphone images of AND-gated colorimetric lateral flow readout of NB and 6-Lamb (NL) multiplex LAMP-OSD assays seeded with the indicated numbers of copies per reaction of SARS-CoV-2 viral genomic RNA (genomic RNA), 30,000 copies of only N gene armored RNA (N RNA only), or 30,000 copies of only Lamb-specific gBlock DNA (Lamb gBlock only), followed by 60 min of amplification prior to analysis on lateral flow dipsticks. (C) Multiplex LAMP-OSD assays comprising unlabeled primers and fluorogenic OSD reporters for both NB and 6-Lamb assays seeded with either no specific templates (0), 30,000 copies per reaction of only N gene armored RNA (N), or 30,000 copies of only Lamb-specific gBlock DNA (L). Endpoint images of OSD fluorescence taken after 60 min of amplification are shown. Data are representative of four biological replicates.