CASCADE: Naked eye-detection of SARS-CoV-2 using Cas13a and gold nanoparticles

Emerging Multiplex Nucleic Acid Diagnostic Tests for Combating COVID-19

“…For example, upon binding to ssDNA or ssRNA, the trans -cleavage mechanism can release a fluorescence reporter from the quenched fluorescence probe [ 9 , 12 , 20 , 70 , 71 , 72 , 73 , 74 , 75 , 76 ]. Different CRISPR-Cas systems have been utilized for multiplex SARS-CoV-2 detection, including the Cas9 system (recognizes dsDNA) [ 77 , 78 ], Cas12 (recognizes both ssDNA and dsDNA) [ 9 , 71 , 72 , 75 , 76 , 79 ], and Cas13 (recognizes ssRNA) [ 12 , 20 , 71 , 74 , 80 , 81 ]. Additionally, amplification techniques, such as RT-PCR [ 9 , 71 , 72 , 76 ], RT-LAMP [ 73 , 77 , 79 ], and RT-RPA [ 9 , 20 , 75 , 78 ], are often combined with CRISPR-based detection to enhance the limit of detection (LOD) in viral detection assays.…”

“…Cas12a complexes, activated when bound to the target gene (amplified by PCR or RPA), cleave the ssDNA linker binding the AuNPs. Following centrifugation, positive solutions will have dispersed AuNPs, resulting in a color change [ 81 ]. They also develop a Cas13–crRNA complex, which, when activated by a target sequence, triggers gold nanoparticle aggregation, creating a pink to purple color shift due to the spatial distribution of the AuNPs [ 81 ].…”

Research progress of CRISPR-based biosensors and bioassays for molecular diagnosis

“…The CASCADE (CRISPR/CAS-based Colorimetric Nucleic Acid Detection) method was recently reported for the rapid and specific diagnosis of SARS-CoV-2 under naked eye conditions (López-Valls et al, 2022). Since colorimetric methods using AuNPs are not commonly used in Cas13-based detection systems, the authors chose the Cas13a enzyme to extend the detection tool, thus increasing its versatility.…”

Visualization Detection Based on Gold Nanoparticles

“…For RNA detection, M. Lόpez-Valls et al introduce a naked-eye method [24]. They first use clustered regularly interspaced short palindromic repeats (CRISPR) protein to recognize RNA of SARS-SoV-2 and start the RNase activity.…”