Robust and reusable iridium oxide-modified FTO electrodes for long-term organ-on-a-chip monitoring

Real-time monitoring in organ-on-a-chip (OoC) systems is critical for capturing dynamic drug responses, yet standard gold (Au) electrodes utilized in electrical cell-substrate impedance sensing (ECIS) suffer from opacity, high cost, and poor reusability. Here, we report a transparent, robust, and reusable sensing interface based on iridium oxide-modified fluorine-doped tin oxide (IrOx@FTO). By electrodepositing nanostructured IrOx onto FTO, we exploited its pseudocapacitive properties to significantly improve interfacial properties, enhancing sensitivity while preserving optical clarity. We integrated these electrodes into a 128-channel high-throughput platform to monitor HaCaT keratinocytes. The system successfully resolved acute surfactant-induced barrier disruption and differentiated dose-dependent cytotoxic responses to doxorubicin (DOX) with higher precision than bare FTO. Crucially, cycling tests involving repeated culture and cleaning revealed that IrOx@FTO maintains exceptional baseline stability, significantly outperforming gold electrodes which exhibited severe degradation and delamination. This work establishes a scalable, optically compatible, and cost-effective strategy for long-term, multi-modal monitoring in advanced microphysiological systems.