Entropy-driven dynamic self-assembled DNA dendrimers for colorimetric detection of African swine fever virus

Herein, we subtly engineered an amplified colorimetric biosensor for the cyclic detection of African swine fever virus DNA (ASFV-DNA), which associated the branched catalytic hairpin assembly (bCHA) amplification with G-quadruplex DNAzyme activity through triplex DNA formation. Firstly, a Y-shaped hairpin trimer was constructed for the dynamic self-assembly of DNA dendrimers. Then, in the presence of ASFV-DNA, the signal strand CP was opened, exposing the toehold regions, which would trigger the CHA cascade reaction between hairpin trimers. In the CHA cascade reaction, H1, H2, and H3 opened and bound in sequence, eventually forming the structure of DNA dendrimers. Subsequently, the obtained bCHA product was specifically recognized by the GGG repeat sequences of L1 and L2, then amplified by the synergistic effect of triplex DNA and the formation of asymmetric split G-quadruplex. Benefiting from the amplification properties of bCHA and the high peroxidase-like catalytic activity of asymmetrically split G-quadruplex DNAzymes, it could achieve effective colorimetric signal output in the presence of ASFV-DNA by means of triplex DNA formation. Under the optimal experimental conditions, this biosensor exhibited excellent sensitivity with a detection limit of 1.8 pM. Further, it was applied to the content detection of simulated samples of African swine fever, and the recoveries were 98.9 ~ 103.2%. This method has the advantages of simple operation, good selectivity, and high sensitivity, which is expected to be used for highly sensitive detection of actual samples of African swine fever virus.