Sandwich-type amperometric aptasensor for carcinoembryonic antigen based on Janus colloids as enzyme-free labeling elements

A masking/toposelective modification approach was employed to prepare novel Janus colloids based on Au nanoparticles anisotropically-modified with polyamidoamine dendrons. Catalytic Pt nanoparticles were further grown into the dendritic structure, and the opposite Au surface of the Janus colloids was provided with specific ssDNA aptamers for carcinoembryonic antigen (CEA). These anisotropic nanoparticles were employed as enzyme-free biorecognition/signaling elements to design an amperometric aptasensor with sandwich-type architecture for the specific detection of CEA, by using screen-printed carbon electrodes functionalized with Au nanoparticles and anti-CEA aptamers as transduction interface. The aptasensor was employed to detect the cancer biomarker in the broad range from 25 pg/mL to 1.0 ng/mL, with detection limit of 8.0 pg/mL. This electroanalytical device also showed high specificity and reproducibility, retaining full biosensing capacity after 50 days of storage at 4 °C. The aptasensor was successfully used to quantify CEA in reconstituted human serum samples.