DNA Extraction Chip Using Key-type Planar Electrodes S. M. Azimi * , W. Balachandran * , J. Ahern ** , P. Slijepcevic *** , C. Newton *** * School of Engineering & Design, Brunel University, Uxbridge, Middlesex, UB8 3PH, UK, Mohamad.azimi@gmail.com ** Chargelabs, 21 Rhestr Fawr, Ystradgynlais, Wales, SA9 1LD, UK *** School of Health Sciences and Social Care, Brunel University, Uxbridge, Middlesex, UB8 3PH, UK ABSTRACT This paper presents a novel method of DNA extraction from whole blood using time varying magnetic field. The novelty of this chip is that both mixing and separation steps are performed in a single chamber in less than a minute with no need for extra microfluidic channels. In order to extract DNA from white blood cells, whole blood is mixed with lysis buffer containing superparamagnetic beads. The mixing chamber is sandwiched between two key-type planar coils. Time varying magnetic field is generated within the mixing chamber to create efficient mixing. This process distributes the magnetic beads both temporally and spatially to achieve the desired mixing effect. Once the white blood cells are lysed, the exposed DNA molecules attach themselves onto the functionalized surface of the magnetic beads. Finally, DNA-attached magnetic beads are attracted to the bottom of the chamber by activating the bottom electrode. DNA molecules are extracted from magnetic beads by washing and re-suspension processes. The extracted DNA output was verified using bench-top PCR and gel electrophoresis. Keywords: DNA chip, DNA extractor, mixer, magnetic bead 1 INTRODUCTION Over the past decade, the advent of Micro-Electro- Mechanical Systems (MEMS) has created the potential to fabricate various structures and devices on the order of micrometers. This technology takes advantage of almost the same fabrication techniques, equipment and materials that were developed by semi-conductor industries. The range of MEMS applications is growing significantly and is mainly in the area of micro-sensors and micro-actuators. In recent years, miniaturization and integration of bio- chemical analysis systems to MEMS devices has been of great interest which has led to invention of Micro Total Analysis Systems (µ-TAS) or Lab-on-a-Chip (LOC) systems. However, whilst there has been a great deal of work in core areas, for example, miniaturizing PCR for expedited amplification of DNA in the microchip format, less effort has been directed towards miniaturizing DNA purification methods. In fact, most of the currently demonstrated microfluidic or microarray devices pursue single functionality and use purified DNA or homogeneous sample as an input sample. On the other hand, practical applications in clinical and environmental analysis require processing of samples as complex and heterogeneous as whole blood or contaminated environmental fluids. Due to the complexity of the sample preparation, most available biochip systems still perform this initial step off-chip using traditional bench-top methods. As a result, rapid developments in back-end detection platforms have shifted the bottleneck, impeding further progress in rapid analysis devices, to front-end sample preparation where the "real" samples are used. A problem with the currently known microfluidic devices is performing efficient chaotic mixing in these platforms, this usually needs existence of moving parts, obstacles, grooves, and twisted or three dimensional serpentine channels. The structures of these components tend to be complex, however, requiring complicated fabrication processes such as multi-layer stacking or multi- step photolithography. Magnetic beads have been of great interest in both research and diagnostic applications. Functionalized surface of magnetic beads offer a large specific surface for chemical binding and may be advantageously used as a mobile substrate for bioassays and in vivo applications [1]. They may have various sizes ranging from a few nanometres up to tens of micrometres. Due to the presence of magnetite (Fe3O4) or its oxidized form maghemite (c- Fe2O3), magnetic particles are magnetized in the presence of an external magnetic field. Such external field, generated by a permanent magnet or an electromagnet, may be used to manipulate these particles through magnetophoretic forces and therefore, result in migration of particles in liquids. Due to the size and distribution of the small embedded iron- oxide grains, particles lose their magnetic properties when the external magnetic field is removed, exhibiting superparamagnetic characteristics. This additional advantage has been exploited for separation of desired biological entities, e.g. cell, DNA, RNA and protein, out of their native environment for subsequent analysis, where particles are used as a label for actuation. This paper introduces a novel DNA extractor process using magnetic beads and time varying magnetic field. Extractions of DNA from white blood cells and Lymphoblast GM 607D have been tested using two different schemes. NSTI-Nanotech 2008, www.nsti.org, ISBN 978-1-4200-8505-1 Vol. 3 249