integrated enzyme‐linked immunosorbent assay system with an organic light‐emitting diode and a charge‐coupled device for fluorescence detection

A fluorescence detection system for a microfluidic device using an organic light‐emitting diode (OLED) as the excitation light source and a charge‐coupled device (CCD) as the photo detector was developed. The OLED was fabricated on a glass plate by photolithography and a vacuum deposition technique. The OLED produced a green luminescence with a peak emission at 512 nm and a half bandwidth of 55 nm. The maximum external quantum efficiency of the OLED was 7.2%. The emission intensity of the OLED at 10 mA/cm2 was 13 μW (1.7 mW/cm2). The fluorescence detection system consisted of the OLED device, two band‐pass filters, a five microchannel poly(dimethylsiloxane) (PDMS) microfluidic device and a linear CCD. The fluorescence detection system was successfully used in a flow‐based enzyme‐linked immunosorbent assay on a PDMS microfluidic device for the rapid determination of immunoglobulin A (IgA), a marker for human stress. The detection limit (S/N=3) for IgA was 16.5 ng/mL, and the sensitivity was sufficient for evaluating stress. Compared with the conventional 96‐well microtiter plate assay, the analysis time and the amounts of reagent and sample solutions could all be reduced.