Signal Amplification Technologies

Abstract

The introduction of target nucleic acid amplification technologies, such as polymerase chain reaction (PCR), nucleic acid sequence-based amplification (NASBA), and strand displacement amplification (SDA), was accompanied by a plethora of technology patents. This made it very difficult for companies without access to these amplification technologies to compete in the area of assay development for ultrasensitive infectious disease detection and quantification. One way around this intellectual property roadblock was the development of highly sensitive assays that depended not on target amplification, but signal amplification. Signal amplification technologies have one major advantage over target amplification in that the issue of contaminating one test run with previously amplified material from a previous run is not an issue. Also, the three signal amplification technologies that are discussed in this chapter are isothermal, meaning that unlike PCR, thermocycling instrumentation is not required. Lastly, assays can be designed to detect and or quantify specific DNA or RNA targets using each of these methods, and, in the case of RNA, without the need to first convert the RNA target to DNA via reverse transcription. Care must still be taken, however, to minimize cross-contamination between samples being tested due to the enhanced analytical sensitivity inherent in assays using signal amplification technologies. An inherent concern with signal amplification methods is that great care must be taken during the design of the assay to ensure that carryover of the different assay components, from one step to the next, is minimized to reduce background noise, which will degrade the analytical sensitivity of the test in question.