A label-free electrochemical immunosensor based on poly(thionine)-SDS nanocomposites for CA19-9 detection

In this paper, poly(thionine) doped sodium dodecyl sulphate nanocomposites (PThi-SDS NCs) were synthesised for the first time. The morphology and characteristics of the PThi-SDS NCs were investigated by using atomic force microscopy (AFM), UV-vis spectroscopy and electrochemical methods. Owing to the unique structure and properties of the PThi-SDS NC, it was used as a redox electrochemical mediator to construct immunoassay combining gold nanoparticles (AuNPs) as the immobilization matrix for antibody. A novel biomolecular immobilization strategy based on PThi-SDS/AuNPs was used to develop a highly sensitive label-free electrochemical immunosensor for the CA19-9 detection. Under optimal conditions, the present immunosensor exhibited a wide linear range of 5 to 400 U mL(-1) with a detection limit of 0.45 U mL(-1). Meanwhile, the novel immunosensor exhibited high selectivity, good reproducibility and stability.