High-speed, whole-column fluorescence imaging detection for isoelectric focusing on a microchip using an organic light emitting diode as light source

An integrated and simplified microfluidic device using a 250 [micro]m X 1-4 cm of organic light emitting diode (OLED) array as a two-dimensional light source for single-channel and multichannel whole-column imaging detection was developed. This fluorescence detection system was used for isoelectric focusing (IEF) of R-phycoerythrin in a microchip. The IEF conditions were optimized, and the total analysis time was extremely reduced to 30 s for 2-cm-long microchannels at 700 V/cm of electric field strength without the presence of electroosmotic flow. The compression of pH gradient caused by electrolytes drawing into the microchannels was efficiently restrained when 1% hydroxylpropylmethyl cellulose in 2% ampholyte was used as the carder for IEF. Under optimized IEF conditions, the detection limit of this system was ~0.6 [micro]g/mL or 45 pg at 75 nL/column injection of R-phycoerythrin. This OLED-induced fluorescence detection system for WCID provides a high-speed IEF technique with quantitative ability and the potential for high integration and throughput microchip systems.