1. Bio-Disk based Nucleic Acid Extraction for Integrated Diagnostic Applications
F. v. Stetten1,2, S. Haeberle1, D. Mark1, R. Zengerle1,2, J. Ducrée1
1HSG-IMIT, Institute for Micromachining and Information Technology, Hahn-Schickard-Gesellschaft, Villingen-Schwenningen, Germany
2Laboratory for MEMS Applications, Department of Microsystems Engineering (IMTEK), University of Freiburg, Germany
Summary
We demonstrate an automated nucleic acid extraction system implemented on the Bio-Disk platform [1]. Applying a rotation sensitive microfluidic switch [2] our novel approach eliminates any hands-on steps common for conventional spin column protocols, such as frequent replacement of collection tubes.
Application of rotation sensitive switch
j Binding of sample DNA on particle surface k Washing to remove impurities l Elution of purified DNA  no carry-over
The Bio-Disk Platform
A passive disposable µ-fluidic cartridge, the Bio-Disk, is operated by an active base instrument, the Bio-Disk Analyzer. Liquid handling is achieved through the interplay between centrifugal and capillary forces. Full process integration can be realized by assembly of µ-fluidic building blocks [1].
DNA
waste
Figure 3: Rotation sensitive switch for separate collection of waste and eluate.
DNA Extraction Results
For an extraction chamber filled with 11 mg silica particles the amount of eluted DNA is plotted versus the amount of sample DNA. The sigmoidal curve shows a saturation at 0.7 µg with a recovery ratio of 16% in the dynamic range.
Figure 1: Bio-Disk Analyzer with microfluidic cartridge y
waste
collection
eluate
rotation
sensitive
switch
silica
column
sample and
buffer inlet
radial
direction
of flow
Bio-Disk for Nucleic Acid Extraction
A spin column protocol following the “Boom chemistry” [3] is established by aggregating silica particles as nucleic acid binding matrix. A rotation sensitive switch enables separate collection of waste and nucleic acid eluate.
Figure 4: Recovery and dynamic range of the Bio-Disk based DNA extraction.
Conclusions & Outlook
A DNA-extraction protocol for the Bio-Disk platform has been evaluated. Successful extraction of DNA from liquid samples was demonstrated, representing the 1st stage of a complete automated DNA-analysis workstation.
Next steps focus on the extraction from whole blood samples and the enhancement of the recovery ratio.
References
[1] S. Haeberle et al., J. Micromech. Microeng. 17, 103– 115, 2007.
[2] S. Haeberle et al., Proc. µTAS 2006, , [3] R. Boom et al., J. Clin. Microbiol., 28, , 1990.
Figure 2: Design of the microfluidic structure for Bio-Disk based nucleic acid extraction.