Branched Dna (bdna) Technology

The branched DNA (bDNA) assay provides a unique and powerful tool for reliable quantification of nucleic acid molecules. Fundamentally different from target amplification methods such as PCR, the bDNA assay directly measures nucleic acid molecules at physiological levels by boosting the reporter signal, rather than replicating target sequences as the means of detection, and hence avoids the errors inherent in the extraction and amplification of target sequences. The bDNA assay employs linear signal amplification using synthetic oligonucleotide probes and bDNA molecules, and can accurately and precisely measure between approximately 500 and 10,000,000 molecules. New advances in bDNA technology include the addition of preamplifier molecules and the incorporation of novel nucleotides, isoC and isoG, into oligonucleotide probe sequences to further enhance signal and reduce noise caused by nonspecific hybridization of bDNA assay components (Kern et al., 1996; Collins et al., 1999). These improvements have extended the quantitative detection limit of the bDNA assay to as low as 50 molecules.