Engineering flexible dopamine biosensors: blended EGylated conjugated and radical polymers in organic electrochemical transistors

We demonstrate an enhancement in the figure of merit (μC*) of a flexible organic electrochemical transistor (OECT) and its dopamine (DA) biosensor by blending various open-shell, non-conjugated radical polymers featuring nitroxide radical active sites as pendant groups with closed-shell, ethylene glycol (EG)-functionalized conjugated polymers as a macromolecular active layer system. The precisely controlled ionic transport of the OECT by the radical polymer modulated the doping level of the EGylated polymer, ensuring well-regulated redox activity and resulting in μC* values exceeding 192 F V^-¹ cm^-¹ s^-¹, along with an on/off ratio of 10⁴. Additionally, we achieved an ultrasensitive detection limit for DA at the clinically relevant level of 1 pM, along with exceptional specificity, effectively distinguishing DA even in the presence of a substantial excess of interfering substances. These findings underscore the potential of a systematic design approach for developing an advanced, flexible OECT-based biosensor platform through the strategic selection and processing of open- and closed-shell macromolecules.