On-chip electrophoretic accumulation of DNA oligomers and streptavidin

A micro-chamber for electrophoretic accumulation of charged biomolecules ha s been designed and evaluated. The system is based on a chip with an array of planar focusing electrodes. Particular attention was devoted to a design which enables penetration of a large sample volume by the electric field of the focusing electrodes. Gene ral design principles for a cylindrically symmetrical arrangement of the fo cusing electrodes were derived. Accumulation of DNA oligomers and streptavidin in aqueous solution was demo nstrated. The concentration of biomolecules in the centre of the chip was e nhanced by up to a factor of 200. The major fraction of the total charge delivered during electrophoretic acc umulation results from Faradaic processes. The maximum charge density deliv erable without visible gas formation was determined. By careful control of the voltage and current density applied to the electrodes, evolution of gas bubbles could be avoided for the time required to accumulate analyte molec ules in the centre of the micro-chamber. On-chip electrophoretic accumulation of biomolecules can be applied to samp le pre-conditioning in lab-on-a-chip devices for analysis of DNA and protei n samples.