Development of an SDS-gel electrophoresis method on SU-8 microchips for protein separation with LIF detection: Application to the analysis of whey proteins.

This work describes the development of an SDS-gel electrophoresis method for the analysis of major whey proteins (α-lactalbumin, β-lactoglobulin, and BSA) carried out in SU-8 microchips. The method uses a low-viscosity solution of dextran as a sieving polymer. A commercial coating agent (EOTrol LN) was added to the separation buffer to control the EOF of the chips. The potential of this coating agent to prevent protein adsorption on the walls of the SU-8 channels was also evaluated. Additionally, the fluorescence background of the SU-8 material was studied to improve the sensitivity of the method. By selecting an excitation wavelength of 532 nm at which the background fluorescence remains low and by replacing the mercury arc lamp by a laser in the detection system, an LOD in the nanomolar range was achieved for proteins derivatized with the fluorogenic reagent Chromeo P540. Finally, the method was applied to the analysis of milk samples, demonstrating the potential of SU-8 microchips for the analysis of proteins in complex food samples.