A new antibody immobilization technique based on organic polymers protected Prussian blue nanoparticles and gold colloidal nanoparticles for amperometric immunosensors

A new antibody immobilization strategy based on organic polymers protected Prussian blue (PB) nanoparticles and gold colloidal nanoparticles (GNPs) was used to develop a highly sensitive amperometric immunosensor for the detection of carcinoma antigen 125 (CA125). PB nanoparticles, as an electron transfer mediator, have been synthesized using chitosan (CS) and poly(diallyldimethylammonium chloride) (PDDA) as protective matrix, which were cast onto a glass carbon electrode surface directly. Then, GNPs were assembled onto the electrode through strong binding interactions between GNPs and amino groups of CS and electrostatic interaction between oppositely charged GNPs and PDDA. Finally, CA125 antibody (anti-CA125), used as a model antibody, was assembled onto the surface of GNPs. UV–vis absorption spectroscopy, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy were employed to characterize CS and PDDA protected PB nanoparticles (CS–PDDA–PB). The assembly process of the modified electrode was characterized with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). The proposed immunosensor showed a high sensitivity, broad linear range and low detection limit for CA125 determination. Moreover, it possessed good reproducibility and stability, and would be applicable to clinical immunoassay of CA125. The use of the CS–PDDA–PB nanoparticles would open new horizons for fabrication of biosensors and biocatalysts.