Platinum Nanoparticle-decorated Graphene Oxide@Polystyrene Nanospheres for Label-free Electrochemical Immunosensing of Tumor Markers

We reported the synthesis of novel platinum-nanoparticle-decorated reduced graphene oxide@polystyrene nanospheres (PtNPs@rGO@PS NSs) and their use in developing a novel label-free electrochemical immunosensor for tumor markers. The PtNPs@rGO@PS NSs were fabricated via the electrostatic self-assembly of negatively charged graphene oxide nanosheets onto positively charged PS nanospheres, followed by hydrazine reduction of the GO outer layer and the in situ deposition of PtNPs. The PtNPs@rGO@PS NSs were characterized by scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The PtNPs@rGO@PS NSs show a large specific surface area, high electrical conductivity, and good hydrophilicity. The nanospheres were further biofunctionalized with streptavidin and a biotinylated antibody for use as a highly sensitive electrochemical immunosensor for the label-free determination of tumor marker carcinoembryonic antigen (CEA). The fabricated immunosensor detected concentrations of CEA ranging from 0.05 to 70 ng/mL with a detection limit of 0.01 ng/mL, presenting high sensitivity comparable to standard commercial techniques. The nanospheres also showed excellent specificity against other tumor markers and reliability in detection with clinical samples.