(152a) Gel-Free Isoelectric Focusing In Plastic Microfluidic Devices

We will present the investigation on isoelectric focusing (IEF) in plastic microfluidic devices. A laser-induced fluorescence (LIF), whole-channel imaging detection (WCID) system has been developed to monitor proteins while they migrate under an electric field. IEF is carried out in a separation medium consisting of carrier ampholytes and a mixture of linear polymers (hydroxyethyl cellulose and hydroxypropyl cellulose). Dynamic coating of the linear polymers prevents proteins from adsorption and suppresses electroosmotic flows. We experimentally confirmed the theoretical prediction that IEF resolution is essentially independent of the focusing length when the applied voltage is kept the same and within a range that it does not cause Joule heating. This result supports the notion that IEF in a microfabricated device leads to more rapid analysis without sacrificing the resolving power. A higher separation voltage also brings about more rapid analysis and superior separation resolution. We found that a linear relationship exists between the focusing time and the inverse of the electrical field strength. IEF of proteins is achieved in 1.5 minutes when 500 V was applied across a 1.9-cm channel. We are incorporating IEF into a microfluidics-enabled two-dimensional electrophoresis device that has a potential to be used for proteomics research.