Highly sensitive, reagentless amperometric immunosensor based on a novel redox-active organic–inorganic composite film

A new highly sensitive amperometric immunosensor for the determination of carcinoembryonic antigen (CEA) had been constructed by employing a novel organic–inorganic composite film coupled with gold nanoparticles. At first, prussian blue (PB) was deposited on a glassy carbon electrode (GCE) and then a new porous organic material synthesized with 3,4,9,10-perylenetetracarboxylicdianhydride (PTCDA) and ethanediamine was coated on the surface of PB film to obtain a stable organic–inorganic composite film, which contained electrochemical redox activity and abundant amino groups on electrode interface. Furthermore, this porous organic material (PTC-NH2) could prevent the leakage of the PB efficiently which led to the significant enhancement of the stability and sensitivity of the immunosensor, as well as provided abundant amino-groups to assemble gold nanoparticles (nano-Au) for immobilization of carcinoembryonic antibody (anti-CEA). The morphologies of PB and the organic–inorganic composite films (PTC-NH2/PB) were studied by means of scanning electron microscope (SEM). In addition, the preparation procedure of the immunosensor was further investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under optimal conditions, the resulting immunosensor displayed a high sensitivity for the detection of CEA, and responded to the CEA concentration in two ranges from 0.05 to 2.0 ng/ml (R = 0.996) and from 2.0 to 40.0 ng/ml (R = 0.995) with a detection limit of 0.018 ng/ml. Moreover, the immunosensor exhibited high selectivity, long-term stability and good reproducibility.