NSTI Nanotech 2009

A Microfluidic Platform for Pre-concentration and Label-free Detection of DNA and Proteins Using On-chip Electrode Arrays

Y.-W. Huang, V.M. Ugaz
Texas A&M University, US

Keywords: detection, preconcentration, DNA, proteins


Here we report a new technique that can enable biomolecules (DNA, proteins) and other charged analytes to be detected in free solution without the need for labeling with chemical fluorophores using a simple device design that consumes minimal electrical power. This method harnesses a microfluidic on-chip electrode array to generate localized zones where the biomolecules become ultra-concentrated, resulting in formation of a mesophase that is clearly visible under ordinary white light. This phenomenon is possible due to the close inter-electrode spacing within the array that permits sufficiently high electric field strengths to be imposed by applying relatively low potentials. Using this arrangement, we show that it is possible to detect a variety of analytes (DNA, proteins, etc.) in free solution by simply illuminating the electrode surface with white light and observing the accompanying strong increase in reflected intensity that occurs at the electrode surface within 10 – 20 s after applying the voltage. This capture process can be precisely tuned by adjusting the buffer pH relative to the analyte’s isoelectric point (e.g., to localize the sample at either the anode or the cathode). This approach is a promising generic label-free method to concentrate and detect small molecule analytes in portable bioanalysis systems without the use of chemical fluorophores.
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