PHILADELPHIA—Even as biomarkers are seeing increased attention, scientists are finding that the current detection methods often aren't sensitive enough to indicate the presence of the marker before damage has been done. With this in mind, researchers at the University of Pennsylvania developed a method that combines immunological detection with nucleic acid amplification-based detection. They presented their efforts in Nature Medicine (2006, 12, 473-477).
The scientists conjugated double-stranded DNA to the detection antibody, which could then be amplified by T7 RNA polymerase. The resulting RNA can then be detected with Invitrogen's fluorescent dye RiboGreen. The researchers compared the new method—fluorescent amplification catalyzed by T7 polymerase technique (FACTT)—against standard ELISA and found that FACTT was 105-fold more sensitive.
They then tested FACTT on mice expressing human Her2 marker and found that unlike ELISA, which could only detect the marker after tumors had become inoperable, the new method could detect Her2 in early tumor development. They then examined human sera samples of healthy and breast cancer patients and successfully identified 90 percent of Her2+ patients compared to only 20 percent by ELISA.