Dramatic Increase in the Signal and Sensitivity of Detection via Self-Assembly of Branched DNA

摘要

In molecular testing using PCR, the target DNA is ampli-fied via PCR and the sequence of interest is investigated via hybridization with short oligonucleotide capture pro-bes that are either in a solution or immobilized on solid supports such as beads or glass slides. In this report, we report the discovery of assembly of DNA complex(es) between a capture probe and multiple strands of the PCR product. The DNA complex most likely has branched structure. The assembly of branched DNA was facilitated by the product of asymmetric PCR. The amount of branched DNA assembled was increased five fold when the asymmetric PCR product was denatured and hybridized with a capture probe all in the same PCR reaction mixture. The major branched DNA species ap-peared to contain three reverse strands (the strand complementary to the capture probe) and two forward strands. The DNA was sensitive to S1 nuclease sug-gesting that it had single-stranded gaps. Branched DNA also appeared to be assembled with the capture probes immobilized on the surface of solid support when the product of asymmetric PCR was hybridized. Assembly of the branched DNA was also increased when hybridization was performed in complete PCR reaction mixture suggesting the requirement of DNA synthesis. Integration of asymmetric PCR, heat denaturation and hybridization in the same PCR reaction mixture with the capture probes immobilized on the surface of solid sup-port achieved dramatic increase in the signal and sensitivity of detection of DNA. Such a system should be advantageously applied for development of automated process for detection of DNA.