The impact of hydrogen peroxide production in OECTs for in vitro applications

Organic electrochemical transistors (OECTs) have shown great potential in bioelectronics to transduce small biological signals for applications such as the electrical recording of excitable cells and assessing cell barrier properties. It is imperative that operating the OECT as a biosensor does not affect the biological system. However, bias voltages applied to channel materials such as the conducting polymer (CP) PEDOT:PSS have been shown to induce the formation of hydrogen peroxide (H2O2) which can disrupt the physiology of cells. In this work, we evaluated the impact of H2O2 formation during OECT operation by comparing an oxygen-sensitive CP (PEDOT:PSS) and an oxygen-stable CP (p(gPyDPP-MeOT2)). While both CPs show high biocompatibility in their non-biased, resting state, we observed large differences during the operation of the electrochemical device. OECTs with PEDOT:PSS produce H2O2 where the H2O2 concentration in the electrolyte depends on the channel area and the time of operation. In comparison, OECTs using the oxygen-stable DPP-based polymer showed no sign of H2O2 formation. Further investigation also revealed how the proliferation rate of neuronal cells directly interfaced with such OECTs was affected by the concentration of H2O2. Our work demonstrated the limitations of oxygen-sensitive OECT channel materials for bioelectronic applications and provides guidance for material design strategies to develop safe bioelectronic devices for real-life applications.