An ultrasensitive electrochemical immunosensor for CEA using MWCNT-NH2 supported PdPt nanocages as labels for signal amplification.

The excellent catalytic activity of a novel nanomaterial was introduced to ultrasensitive sandwich-type electrochemical immunosensor applications for detection of carcinoembryonic antigen (CEA). Amino-functionalized multi-walled carbon nanotube (MWCNT-NH2) supported PdPt nanocages were used as catalytic labels of secondary anti-CEA. PdPt nanocages with hollow interiors and porous walls could efficiently enhance electrocatalysis for reduction of H2O2. Meanwhile, with good dispersion, large specific surface area and amino groups, MWCNT-NH2 can immobilize a large amount of PdPt nanocages to improve the sensitivity and amplify the signal of the immunosensor. For the immobilization of primary antibodies, 3-aminopropyltriethoxysilane functionalized graphene sheets were used as transducing materials to modify glassy carbon electrodes and to enhance the electron transfer efficiently. Under the optimal conditions, the electrochemical immunosensor exhibited a wide linear range of 0.001-20 ng mL-1 with a low detection limit of 0.2 pg mL-1 for CEA. The proposed sensing strategy enriches electrochemical immunoassays and may have a promising application in bioassay analysis.