Lab in a drop

In contrast to other chip-based methods, the actual sample, such as a drop of blood, can be placed directly on the PCR chip, where it is mixed with a drop that contains magnetic particles. These particles are equipped with antibodies on their surface, antibodies that bind specifically to the interesting cells in the blood. By moving a magnet underneath the chip, a droplet containing the bound magnetic particles is physically pulled out of the blood droplet and moved on to the next station—a droplet of washing liquid. The magnetic droplet is combined with the washing droplet and then pulled out again through movement of the magnet. Another droplet then delivers the enzymes and reagents necessary for cell disruption.

The last station is the PCR station. After combination with a reagent droplet, the magnetic droplet is moved around like a clockwork, passing again and again through four different zones set to the temperatures necessary for PCR. Each cycle lasts 8 seconds. A fluorescence detector over one of the zones monitors the progress of the PCR (real-time PCR) and indicates whether the desired gene sequence is present and in what amount.

With their new PCR chip, the researchers were able to isolate 30 cells implanted with the genetic information for a green-fluorescing protein from 25 µL of blood, concentrate them 100-fold, wash them, rupture them, and detect the gene for the green protein by real-time PCR—all within just 17 minutes!

Author: Jürgen Pipper, Institute of Bioengineering and Nanotechnology (Singapore),
http://www.ibn.a-star.edu.sg/research_areas_04_details.php?id=103
Title: Clockwork PCR Including Sample Preparation
Angewandte Chemie International Edition 2008, 47, No. 21, 3900–3904, doi: 10.1002/anie.200705016