Bilirubin Sensing Using Organic Electrochemical Transistors: Role of Gate Materials and Operational Parameters.

Bilirubin, a critical yellow-orange bile pigment and heme degradation product, serves as a key biomarker for neonatal jaundice and liver dysfunction, with elevated concentrations posing significant neurotoxicity risks particularly in neonates. However, timely detection remains challenging due to limitations in current point-of-care technologies. This study reveals that organic electrochemical transistors that include PEDOT:PSS as the channel material exhibit inherent sensitivity to free bilirubin - but only when paired with polarizable gate electrodes (Au, Pt, glassy carbon). Intriguingly, this response is abolished with non-polarizable Ag/AgCl gates, highlighting the pivotal role of electrode polarizability in bilirubin detection. Furthermore, the drain-source current changing direction is modulated by operational parameters, suggesting complex interfacial dynamics between bilirubin and channel material. Through systematic investigation, we demonstrate that this sensitivity persists for human serum albumin-bound bilirubin, a clinically relevant complex, and elucidate the redox mechanisms underlying signal transduction via cyclic voltammetry. Our work not only decouples the influence of gate materials and measurement conditions on device performance but also establishes a foundational framework for designing high-precision bilirubin sensors, paving the way for transformative diagnostic devices that address critical gaps in neonatal care through miniaturized, low-power platforms capable of real-time bilirubin monitoring in both clinical and resource-limited settings.