Multi-Dimensional Microchip Electrophoresis of Proteins

The popularity of micro-Total Analysis Systems (μ-TAS) is exponentially increasing, especially in the fields of medical and biological analyses. The work presented here includes 2-D separation of proteins in PMMA-based microchips. Sodium Dodecyl Sulfate Capillary Gel Electrophoresis (SDS-CGE) and Micellar Electrokinetic Chromatography (MEKC) were used as the separation scheme for the first and second dimension of electrophoresis, respectively. The separation mechanism in MEKC is based on differences in distribution coefficient between the micellar and the non-micellar (aqueous) phases. SDS-CGE is the adaptation of traditional gel electrophoresis into the microchannels using polymers in solution as sieving matrices. This allows solutes having similar charge-to-mass ratios to be resolved by size. Both dimensions were prepared in a hot-embossed PMMA microchip. Electrokinetic injection and separation were used with field strengths ranging from 100-400 V/cm. To perform this, an automatedprogrammable power supply was used. Laser-induced fluorescence (LIF) was used as the detection method for dye-labeled proteins ranging from 38 kDa to >100 kDa in size. Each peak in the first dimension (SDS-CGE) is shifted to the second dimension for further separation using MEKC. Finally, a 2D separation platform is reported for protein samples that were efficiently separated in a few minutes.