Concentration and Separation of Proteins in Microfluidic Channels on the Basis of Transverse IEF

The use of microfluidic channels formed by two electrodes made of gold or palladium to perform transverse isoelectric focusing (IEF) is presented as a means for continuous concentration and fractionation of proteins. The microchannels were 40 mm long with an electrode gap of 1.27 mm and a depth of 0.354 mm. The properties of pH gradients formed as a result of the electrolysis of water were influenced by variation of parameters such as the initial pH, ionic strength, and flow rate. Transverse IEF in pressure-driven flow is demonstrated using bovine serum albumin in a single ampholyte buffer as well as in multiple-component buffers. Experimental results of protein focusing compare well to predictions of a mathematical model. Optimal conditions for efficient continuous fractionation of a protein mixture are summarized and discussed.