Electrophoretic Concentration of Proteins at Laser-Patterned Nanoporous Membranes in Microchips.

Laser-patterning of nanoporous membranes at the junction of a cross channel in a microchip is used to integrate protein concentration with an electrokinetic injection scheme. Upon application of voltage, linear electrophoretic concentration of charged proteins is achieved at the membrane surface because buffer ions can easily pass through the membrane while proteins larger than the molecular weight cutoff of the membrane are retained. Sample preconcentration steps are ever-present components of analytical systems, since concentration of trace samples facilitates their detection.