Status Report on Novel DNA Measurement Technologies: Emerging Technologies to Detect DNA Without Prior Amplification

Date: 30/06/2000	Ref No: LGC/VAM/1999/111	Type: Report
Author(s): Heaton A, Foy C, Parkes H
Organisation/Publisher: LGC

Advances in DNA analysis to develop methods which are increasingly specific, sensitive, fast, simple and cost-effective are considered paramount.  Many current technologies depend upon the amplification of the target by methods such as PCR prior to analyte detection.  There are several drawbacks to amplification-based approaches including the requirement for specialised thermal cycling equipment, the requirement for relatively pure starting samples which are free from PCR inhibitors, the risk of possible amplification bias and contamination issues.
A desirable improvement to the current technologies would be the ability to detect specific DNA targets directly.  As prior target amplification is not required such techniques can offer a more cost effective, quicker and potentially higher throughput method of DNA 'measurement' compared with conventional methods.  Methods which do not rely upon initial amplification may be more amenable to the development of simple 'point-of-care' or field-based testing devices.  The issue of cross-contamination of targets with products from previously amplified targets is eliminated.  Also, distortions resulting from differential amplification of the target are not introduced therefore quantitation may be more reliable.
Recent activities in this area have started to produce promising results. This report focuses on recently reported methods which do not require amplification of either the target or the probe/signal by methods such as PCR for detection.  This report augments the previous report in the area of DNA 'measurement'  (Heaton & Parkes, 1999).
Current methods for ultrasensitive detection include:
1) Fluorescence Correlation Spectroscopy (FCS) 
2) Surface Enhanced Raman Spectroscopy (SERS)
3) Single molecule electrophoresis (SME)
4) Quantum dot particles (Qdots)