Two-Dimensional Electrophoresis in a Chip
Z. Hugh Fan, Champak Das and Hong Chen
from: Lab-on-a-Chip Technology (Vol. 2): Biomolecular Separation and Analysis (Edited by: Keith E. Herold and Avraham Rasooly). Caister Academic Press, U.K. (2009)
Two-dimensional (2D) electrophoresis chips are fabricated from cyclic olefin copolymer resins using microfabrication and compression molding techniques. Protein separation in the chips is carried out by integrating isoelectric focusing (IEF) and polyacrylamide gel electrophoresis (PAGE). Each chip consists of one IEF channel for the first dimension and 29 parallel PAGE channels for the second dimension. The IEF and PAGE channels are intersected orthogonally so that the focused protein can be transferred from the first to the second dimension. An array of microfluidic pseudo-valves is created for introducing different separation media, without cross-contamination, in both dimensions. Fabrication of the valves is achieved by photo-initiated, in situ gel polymerization; acrylamide monomers are polymerized only in the PAGE channels whereas polymerization does not take place in the IEF channel where a mask is placed to block light exposure. A layer of titanium dioxide membrane can also be synthesized at the interface of two dimensions for strengthening the pseudo-valves. The presence of the valves does not affect the performance of IEF or PAGE when they are investigated separately. Detection in the chip is achieved using a laser induced fluorescence imaging system. Fluorescently-labeled proteins with either similar pI values or close molecular weight are well separated, demonstrating the potential of the 2D electrophoresis chips read more ...