Analysis of tumor-specific extracellular DNA fragments and mRNAs in the blood can enable specific detection of tumor types from a simple blood sample. These circulating nucleic acids are present in serum or plasma usually as short fragments, <1000 bp (DNA) or <1000 nt (RNA). In addition, miRNAs, as small as 21 nt, have the potential to provide biomarkers for certain cancers and disease states.
The QIAamp Circulating Nucleic Acid Kit enables efficient purification of these circulating nucleic acids from human plasma or serum and other cell-free body fluids. Efficient purification with reproducible yields provides a representative population of the circulating nucleic acids in blood (see figure " Reproducible recovery of circulating DNA"). Tube extenders and vacuum processing on the QIAvac 24 Plus enable starting sample volumes of up to 5 ml, and flexible elution volumes between 20 μl and 150 μl allow concentration of nucleic acid species that are present in low concentrations. The kit provides advanced technology of selective binding to a silica-based membrane for improved recovery of fragmented nucleic acids (see figure " Improved recovery of fragmented DNA").
Purification of circulating RNA, without copurification of DNA, is possible with DNA digestion using the RNase-Free DNase Set. A specialized protocol provides highly efficient purification of small RNA, such as miRNAs (see figure " Efficient purification of circulating miRNA"). Methylated DNA can be efficiently purified using the QIAamp Circulating Nucleic Acid Kit. The purified DNA maintains its methylation, allowing bisulfite conversion for analysis of the methylation state (see figure " Efficient recovery of methylated DNA").
The purified and concentrated circulating DNA and RNA is free of proteins, nucleases, and other impurities, and is ready to use in wide range of downstream applications, including:
- PCR and quantitative real-time PCR and RT-PCR
- Biomarker research and validation for blood-based cancer detection
- Viral nucleic acid detection