Method for detecting new coronavirus and variant strain by using double-stranded DNA (deoxyribonucleic acid) and colorimetric biosensor and application of method

The invention belongs to the technical field of molecular diagnosis, particularly relates to double-stranded DNA and a colorimetric biosensor for detecting new coronavirus and variant strains, and constructs a colorimetric biosensor for detecting SARS-CoV-2 with strong specificity and low cost on the basis of Toehold mediated strand displacement reaction. Under the driving of thermodynamic entropy, target nucleic acid is combined with a Toehold region on double-stranded DNA to initiate strand displacement reaction, a complete G-rich sequence is released and is combined with hemin to form a G-quadruplex/hemin compound, and then hydrogen peroxide is catalyzed to oxidize 3, 3 ', 5, 5'-tetramethyl benzidine, so that the solution is blue. Meanwhile, a camera is adopted to capture RGB of the solution, and experimental results observed by naked eyes are verified. According to the invention, qualitative analysis can be carried out on SARS-CoV-2 target nucleic acid, and the sensing system shows high-specificity signif