Microfluidic systems for extracting nucleic acids for DNA and RNA analysis

This paper is to review the differences in the developments of microfluidic chips for extracting genomic deoxyribonucleic acid (DNA) and viral ribonucleic acid (RNA) from blood by the Biosensor Focus Interest Group (BFIG) in Singapore. DNA was extracted in a multi-step process by isolating and lysing white blood cells (WBC), typically similar to 10 mu m in diameter. Viral RNA was extracted directly from the submicron viruses in the blood. In terms of basic microfluidic components required, both DNA and RNA extractions used similar mixers for mixing reagents, filters for capturing or separating the blood cells, and a binder for capturing and purifying the DNA/RNA molecules. The designs of the filters were adapted to either capture WBC for DNA isolation or capture all virus particles for RNA isolation. The designs of these two kinds of filters had to be different. Besides the differences in the sizes of WBC and viruses, the concentration of the virus particles is usually much lower than WBC. Thus, a much higher volume of blood for filtering would be required for extracting viral RNA, especially for the intention to detect the viruses at early onset of infection. With proper modifications of the protocols, it has been demonstrated that both genomics DNA and viral RNA could be extracted successfully in these microfluidic chips. The quality of the extracted samples was verified by polymerase chain reaction (PCR) and gel-electrophoresis after the extractions. (c) 2006 Elsevier B.V. All rights reserved.