Conjugated Polymer Nanoparticles as a Fluorescence Probe for Amplified Detection of Human Serum Bilirubin

Bilirubin (BR) is a potent biomarker for jaundice and liver malfunction. However, its quantitative determination remains a bottleneck due to the interference of numerous biomolecules present in the blood serum. To overcome this, a conjugated polyfluorene derivative, poly1,1′-((2,7-dimethyl-9H-fluorene-9,9-diyl)bis(hexane-6,1-diyl))bis(1H-benzo[d]imidazole) (PFBZ), was synthesized by incorporating it with a specific receptor, benzimidazole, for BR detection using a low-cost and straightforward oxidative coupling polymerization. The PFBZ polymer spontaneously forms nanoparticles in an aqueous medium and unveils excellent sensitivity toward BR in an aqueous PBS medium with a limit of detection of 6.9 pM, which is far less than the clinically relevant range. The sensing mechanism is based on probe–analyte interaction chemistry and Förster resonance energy transfer, which were confirmed from both experimental and theoretical studies. This platform offers excellent sensitivity and selectivity, which motivated us to successfully explore the quantitative determination of BR in real serum samples. This method of sensing is straightforward, noninvasive, and can be used as a biomedical sensor to diagnose the onset of jaundice and liver malfunction.