Individual evaluation of DEP, EP and AC-EOF effects on λDNA molecules in a DNA concentrator

Bio-concentrators have been proposed to concentrate and detect tiny amount of cells, DNAs, or proteins in a microfluidic system. Concentrating processes have been experimentally Studied and discussed as a result of concentration caused by multiple electrokinetic phenomena. Here, we have investigated individual electrokinetic phenomenon in a DNA concentrator to propose a design guide for a micro-bioconcentrator. Three dominant electrokinetic phenomena: dielectrophoresis (DEP), electrophoresis (EP). and AC electroosmotic flow (AC-EOF) are experimentally and theoretically evaluated. DNA mobility due to DEP was separately Studied by utilizing quadrupole electrodes generating a uniform field gradient, which enables LIS to derive a DEP force on the order of 10(-13) N acting on a single DNA molecule. Using the theoretical model the DEP force on the order of 10(-12) N, close to the experimental result, was calculated. The EP force estimated from the average charge per base pair of DNA molecule Was on the order of 10(-9) N. Compared with these two forces, AC-EOF generating a flow velocity of 100-200 mu m/s, globally dominates the manipulation of DNA Molecules throughout the concentrator. However, the three-dimensional observation of molecule distribution reveals that the EP force has a significant role in holding the DNA molecules at the electrode centre. The results not only Support the proposal that the biomolecular concentrator Should be designed to utilize AC-EOF and EP [1,2], but also provide approximate estimates for the DEP and EP forces, and the AC-EOF velocity which will allow us to design a concentrator with a given experimental condition. (C) 2009 Elsevier B.V. All rights reserved.