CRISPR/Cas12a coupled with enzyme-DNA molecular switch photoelectrochemical assay for HIV nucleic acid

Molecular switches formed by enzyme-DNA hybrid compounds combined with CRISPR-Cas12a cis-cleavage used for photoelectrochemical nucleic acid assay was fabricated. A compound, molecular switch, consisting of Taq DNA polymerase, aptamer, block DNA and methylene blue labeled primer (primer-Mb) is formed. Block DNA is assembled on the surface of MBs (block DNA-MBs), and hybridized with the primer-Mb. In the presence of Human Immunodeficiency Virus (HIV) target, molecular switches are turned on by hybridization of the target with block DNA. The Taq DNA polymerase is released and activated. The activated Taq DNA polymerase elongates the primer via the template, block DNA, which attached onto Magnetic beads (MBs). A dsDNA with Mb (dsDNA-Mb) was formed. With the assistance of Cas12a, a amplified photoelectrochemical signal was obtained and the HIV target DNA was qualified. Under the best conditions, the limit of detection (LOD) can be as low as 0.3 fM. This photoelectrochemical assay extends the tool kit of molecular nanotechnology.