Immunosensing microchip using fast and selective preparation of an iridium oxide nanoparticle-based pseudoreference electrode

Iridium oxide (IrO_x) electrodes have been used as pseudoreference electrodes operating in buffered solutions, but their preparation requires a time-consuming procedure. Here we report a simple, fast, and selective preparation of an IrO_x pseudoreference electrode based on the deposition of presynthesized IrO_x nanoparticles. The reference electrode is applied to an immunosensing microchip consisting of a patterned poly(dimethylsiloxane) plate and an indium-tin oxide-micropatterned glass. The sequence of microfabrication is optimized to accomplish better performance. The microchip is operated by capillary-driven microfluidic controls and used for detecting a target mouse IgG. The measured detection limit in the microchip is ca. 10pg/mL.