Immunosensing Microchip Using Fast and Selective Preparation of an Iridium Oxide Nanoparticle-Based Pseudoreference Electrode

Iridium oxide (IrOx) 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 IrOx pseudoreference electrode based on the deposition of presynthesized IrOx 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. 10 pg/mL.