Separation and Concentration of Proteins by Isoelectric Focusing without Carrier Ampholytes in a Nitrocellulose Membrane

This paper reports a simple isoelectric focusing (IEF) technique without carrier ampholytes to generate stable pH gradients in a nitrocellulose membrane for the fabrication of paper-based analytical devices suitable for complex biological samples. To design the custom-built IEF apparatus, silver-coated copper wire electrodes were employed; the distance between anode and cathode was 8 mm. Concentration and separation of sample biological analytes (bovine serum albumin and avidin conjugated with different fluorescent dyes) were performed with continuous sample flow to demonstrate the potential of paper-based IEF for use in sample pre-conditioning systems.