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

Abstract

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.