Separating the DNA from the blood
and concentrating DNA directly from blood samples that could speed
up the use of genomics in clinical trials.
Researchers from the University of Virginia in the US, have developed a microdevice, described in an early view article in the journal Analytical Chemistry, for extracting DNA samples from whole blood samples. The device can capture DNA from whole blood samples as large as 10µL allowing the detection of low abundant disease biomarkers or infectious agents such as bacteria or viruses. "DNA purification and preconcentration [of whole blood] is a requirement for most genetic analysis applications, primarily due to the complex nature of the biological samples," write the authors. They continue to explain that whole blood is a complex mixture of nucleic acids, proteins, lipids, metabolites and inorganic ions and some of these can inhibit DNA amplification using PCR (polymerase chain reaction) techniques. While other microdevices have been designed to process human whole blood, they often suffer from poor DNA extraction efficiency and tend to involve a protein wash that increases the number of steps involved in the process. The poor DNA extraction efficiency arises due to the large mass of protein present in blood that can block DNA capture and lead to poor PCR results unless they are washed away prior to analysis. These devices tend to only be able to process small sample volumes of blood, up to 1.5µL, making the need for multiple runs or parallel purifications necessary. The new device makes use of a two-stage system extraction system that is made up of a C18 reverse phase column for protein extraction coupled to a monolithic column for DNA extraction. "This provided not only an improvement in extraction efficiency over other chip-based DNA extraction solid phases but also the highest extraction efficiency reported to date for such sample volumes in a microfluidic device," write the authors. "As an added bonus, the two-stage, dual phase microdevice allowed the 2-propanol wash to be completely eliminated, streamlining the process without affecting the PCR amplifiability of the extracted DNA."
