Self-assembled polymeric nanoparticles film stabilizing gold nanoparticles as a versatile platform for ultrasensitive detection of carcino-embryonic antigen

In this work, a novel impedimetric immunosensor was developed based on electrophoretic deposition of polymeric self-assembled nanoparticles for the sensitive determination of carcino-embryonic antigen (CEA). Biocompatible polymeric nanoparticles y-PGA-DA@CS were prepared by self-assembly of chitosan (CS) and dopamine modified poly(y-glutamic acid) (y-PGA-DA) under mild conditions. A dense and nanostructured nanoparticles film was obtained on the electrode surface by electrophoretic deposition of y-PGA-DA@CS nanoparticles. Gold nanoparticles (Au NPs) were then tightly anchored on y-PGA-DA@CS film with homogeneous dispersion due to numerous exposed dopamine adhesive dots present on the surface of y-PGADA@CS. The obtained Au/y-PGA-DA@CS nanocomposite film not only increases the electrode surface area in nanoscale dimension, but also provides a highly stable and biocompatible matrix for the convenient conjugation of antibody, thus providing a high-efficiency immunoassay platform. Monoclonal antibodies to carcinoembryonic antigen (CEA-Ab) were effectively immobilized on the Au/y-PGA-DA@CS film and a label-free impedimetric immunosensor was fabricated successfully as the ultimate goal. Under optimal conditions, the resultant immunosensor exhibited a wide linear range from 2.0x10(-14) g mIri to 2.0 x10(-8) g ml(-1) for the detection of CEA with a low detection limit of 10 fg mL(-1). To the best of our knowledge, this was the lowest detection limit compared with other counterparts of label-free impedimetric immunosensors. Moreover, the immunosensor showed high specificity, good stability and satisfactory reproducibility. As a proof of concept, the proposed strategy provided a promising and versatile platform for clinical immunoassay of other tumor markers and biomolecules.