A highly specific and sensitive fluorescence quenching probe for carcinoembryonic antigen detection based on tetrapod Au nanostars with Ag coating

The fluorescence quenching properties of Ag-coated Au tetrapod nanostars have been studied via fluorescence spectroscopic techniques. Because of the intense plasmonic light absorption and the corresponding fluorescence resonance energy transfer (FRET), the fluorescence quenching effect of Au tetrapod nanostars could be greatly enhanced by Ag coating. What's more, the fluorescence quenching ability of Ag-coated Au tetrapod nanostars could be further increased by tuning the size of inner Au tetrapod nanostars or the thickness of the outer Ag coating. In the study of carcinoembryonic antigen (CEA) detection based on the fluorescence probe of Ag-coated Au tetrapod nanostars, surface modification of antibody conjugation has been carried out to guarantee the specificity. Under the optimized conditions, the fluorescence efficiency of the Ag-coated Au tetrapod nanostars probe exhibits a linear response to CEA concentration ranging from 10−280 pg/mL, and the corresponding theoretical detection limit (LOD) is as low as 8.2 pg/mL. Interference experiment results shows that the influence from the interfering proteins could be neglected in the detection, and it has been successfully applied to detect CEA in real samples. Compared with other optical detection techniques of CEA, this method based on fluorescence quenching of Ag-coated Au tetrapod nanostars has better performance because of the special geometry features including regular tips and Ag coating.