Iridium oxide pH sensor for biomedical applications. Case urea–urease in real urine samples

This work demonstrates the implementation of iridium oxide films (IROF) grown on silicon-based thin-film platinum microelectrodes, their utilization as a pH sensor, and their successful formatting into a urea pH sensor. In this context, Pt electrodes were fabricated on Silicon by using standard photolithography and lift-off procedures and IROF thin films were growth by a dynamic oxidation electrodeposition method (AEIROF). The AEIROF pH sensor reported showed a super-Nerstian (72.9±0.9 mV/pH) response between pH 3 and 11, with residual standard deviation of both repeatability and reproducibility below 5%, and resolution of 0.03 pH units.For their application as urea pH sensors, AEIROF electrodes were reversibly modified with urease-coated magnetic microparticles (MP) using a magnet. The urea pH sensor provided fast detection of urea between 78 μM and 20 mM in saline solution, in sample volumes of just 50 μL. The applicability to urea determination in real urine samples is discussed.

► Electrodeposited iridium oxide films (AEIROF) on thin-film platinum electrodes.
► Potential-pH measurement against on-chip thin-film pseudo-reference.
► Urease incorporation by using magnetic beads.
► Urea detection in real urine sample.