Au3+-Assisted Bilirubin Oxidation and Electrochemical Investigation of Biliverdin on Poly(4-aminobenzoic acid)-Modified Screen-Printed Carbon Electrode

Free-unconjugated bilirubin (BR) is a crucial biomarker of liver function and its related disorders. Electrochemical BR detection suffers due to insolubility and its electrode fouling nature. This study demonstrates a new approach to the electrochemical investigation of biliverdin (BV), obtained from Au3+-assisted BR oxidation. The BR oxidation reaction was analyzed using UV–vis spectroscopy, demonstrating Au3+ as a suitable oxidant for complete BR oxidation within 3 min with a molar ratio of 1.67. Cyclic voltammetry and amperometric techniques were used to investigate the BV on poly (aminobenzoic acid) (PABA) modified screen-printed carbon electrodes (SPE). The fabricated SPE/PABA electrode was developed by potential-dynamic technique and characterized using physicochemical, and electrochemical methods. BV was electrochemically oxidized at 0.32 V in a buffer with pH 8.5. The SPE/PABA shows selective BV oxidation, reduced fouling, and enables a broad range of BV detection. The sensor shows a high sensitivity and linear range of 0.115 μA μM−1 cm−2 and 5 to 440 μM, respectively, with a limit of detection of 0.9 μM. Additionally, the sensor exhibited good reproducibility and high selectivity in the presence of potential interfering biomolecules. The analysis of human serum spiked samples shows promising results, suggesting potential applications in the diagnosis of bilirubin-related disorders.