A novel conjugated polyfluorene: synthesis, characterization and application in label-free ECL immunoassays for biomarker detection

In this paper, a novel amino-functionalized polyfluorene derivative has been successfully designed and synthesized. Polyfluorene derivatives are commonly used as signal-transducing elements for sensor applications due to their signal amplification properties and the versatility of the molecular design process. Hence, an electrogenerated chemiluminescence (ECL) label-free immunosensor based on a novel ECL reagent was also prepared by chemical modification of a polyfluorene derivative on an indium tin oxide (ITO) glass electrode. The ECL and X-ray photoelectron measurements demonstrated the covalent attachment of the polyfluorene derivative to the ITO glass electrode. It can be found that the ECL of the polyfluorene derivative at a low positive potential (ca. 0.3 V vs. Ag/AgCl) induced a strong light emission on the polyfluorene derivative-modified ITO glass electrode. The label-free immunosensor was successfully applied in the detection of a cancer biomarker: ovarian protein antigen (CA125) with high sensitivity, specificity, and stability. The results indicated that the ECL signal decreased regularly with the CA125 concentration increasing from 0.50 to 500 U mL−1, and the detection limit was 0.087 U mL−1. Moreover, the polyfluorene derivative-based ECL immunosensor can be accurately employed to detect the CA125 concentration in 10 human serum samples, suggesting the promising application of the as-proposed ECL immunosensor in the field of clinical screening of cancer biomarkers.