Microfluidic free-flow electrophoresis: A promising tool for protein purification and analysis in proteomics

Microfluidic free-flow electrophoresis (μFFE) is the most promising technique for proteomics. This method can perform real-time separation and detection of analytes in a small device where a continuous flow of carrier buffer is driven and an external electric field is applied perpendicular to the buffer flow. The capability of μFFE has motivated extensive applications pertaining to the pre-fractionation, enrichment, and higher-level purification of target proteins in biological systems. This review introduces the proteomics applications of the technique, along with a detailed theoretical overview, as follows. First, the principle and the band broadening involved in μFFE are explained. Next, materials for the fabrication of a μFFE device are described, followed by a summary of the online detection methods for μFFE. Finally, various applications of μFFE in proteomics fields are introduced, particularly focusing on microfluidic free-flow zone electrophoresis and microfluidic free-flow isoelectric focusing, the two major separation modes of μFFE.