Signal Amplification Methods

Abstract

Signal amplification methods were initially designed as an alternative to the target amplification technologies such as polymerase chain reaction (PCR) so as to minimize the possibility of contamination by target amplification products. Unlike target amplification, signal amplification methods (as defined herein) do not rely on enzymes for the amplification. Probe-based amplification techniques such as cleavage-based amplification (36) and rolling-circle amplification (1) rely on enzymes, and will not be covered in this chapter. Signal amplification increases or amplifies the signal generated from the probe molecule hybridized to the target nucleic acid sequence. The advantages of signal amplification methods include specific detection, dynamic range, ease-of-use, and reproducibility. To date these methods have met the challenge from advanced or automated target amplification methods such as real time PCR. Signal amplification technologies include hybrid capture (HC) and branched DNA (bDNA) assays (32, 33). The HC method was developed and marketed initially by Digene Corporation (Gaithersburg, MD) which was acquired by Qiagen (Valencia, CA) in 2007. The bDNA method was initially developed by Chiron (Emeryville, CA), marketed by Bayer Diagnostics (Emeryville, CA) which diagnostic division was acquired by Siemens (Tarrytown, NY) in 2006. Due to the growing demand for quick time to detection, automation, and multiplexing, the popularity of commercial signal amplification methods has declined in clinical virology laboratories.