Device Structure for enhancement of DNA hybridization kinetics by Electrodeless Dielectrophoresis
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1064-PP06-08
Device Structure for enhancement of DNA hybridization kinetics by Electrodeless Dielectrophoresis Nathan Swami1, Chia-fu Chou2,3, and Fernanda Camacho-Alanis1 1 Electrical & Computer Engineering, University of Virginia, 351 McCormick Rd., PO Box 400743, Charlottesville, VA, 22904 2 Institute of Physics, Academia Sinica, 128, Sec. 2, Academia Rd., Nankang, Taipei, 11529, Taiwan 3 Harrington Biomedical Engineering, Arizona State University, Tempe, AZ, 85287 ABSTRACT Signal transduction for purposes of biomolecular sensing can be enhanced through miniaturization (nanoscale sensors such as nanowires, cantilevers, etc), but this may impose insurmountable limitations on transport of analyte molecules to the surface. In order to improve biomolecular detection sensitivity, this study aims to develop electrodeless dielectrophoresis (EDEP) methods for the selective transport and trapping of analytes in close proximity to the sensor surface. A device design based on microscale dielectric constrictions of the fluidic channel and nanoscale metal electrode edges was used to locally enhance electric field gradients and trap biomolecules. The resulting electric field focusing effect was enhanced as a result of miniaturization and an instantaneous ten-fold EDEP preconcentration was obtained in high-salt buffers (50 mM NaCl) that enabled an equivalent improvement in DNA hybridization kinetics. INTRODUCTION The role of mass transport limitations on sensitivity of biomolecular sensor assays, especially for miniaturized sensor arrays, has been widely recognized [1], [2]. For many detection platforms based on electrochemical, surface enhanced Raman spectroscopy (SERS) [3], electrical, resonance frequency shift, and surface Plasmon resonance methods [4], miniaturization improves signal transduction and sensitivity to varying degrees. However, miniaturization poses penalties on passive transport of biomolecules by diffusion to the sensor surface [2]. At successively lower DNA target concentration values, fewer target DNA molecules are available for diffusion towards the miniaturized sensor surface, and consequently for hybridization with surface bound capture probe DNA molecules. This slows down binding kinetics; thereby considerably delaying signal onset and saturation (i.e. complete hybridization of all capture probes on sensor surface). Hence, while signals barely above the noise are observed for various biomolecular assays at pico-molar or lower target DNA concentration values [6], these assays operate under mass transport limitations of analyte rather than at a signal transduction limitation. For protein sensors, transport limitations become even more crucial since proteins with ~100kDa molecular weight diffuse an order of magnitude slower than DNA molecules. Hence, in order to capitalize on improved signal transduction as a result of sensor miniaturization, there is a need to develop active transport methods that can selectively direct the transport of target biomolecules towards the sensor surface, and especially focus
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